As a novel carbon allotrope, carbon quantum dots (CQDs) have been investigated in various fields, including photocatalysis, bioimaging, optoelectronics, energy and photovoltaic devices, biosensing, and drug delivery owing to their unique optical and electronic properties. In particular, CQDs’ excellent sunlight harvesting ability, tunable photoluminescence (PL), up-conversion photoluminescence (UCPL), and efficient photo-excited electron transfer have enabled their applications in photocatalysis. This work focuses on the recent progress on CQDs-related materials’ synthesis, properties, and applications in photocatalysis.  Dots), or carbon nanodots , carbon dots  on the surface, which give water solubility and the possibility of further functionalization  from arc-discharged soot that they came up with the idea to publish their findings in Science . There hTop-down techniques use treatments including arc discharge, laser ablation, electrochemical oxidation, chemical oxidation, and ultrasonic synthesis to create CQDs from macroscopic carbon structures such as graphite, activated carbon, and carbon nanotubes . Bottom-Recent trends in CQD preparation favor laser ablation, which can easily control morphology and manufacture a variety of nanostructures. Laser ablation is an excellent process for creating CQDs with a limited size distribution, good water solubility, and fluorescence properties, among other qualities. However, it is not widely used because of its intricate operation and high cost .In two different configurations, a batch configuration and a flow jet configuration, Donate-Buendia et al. synthesized CQDs by laser irradiation of glassy carbon particles suspended in polyethylene glycol 200 .via oxidation . The dark suspension was cooled and then separated using a 1,000 Da ultrafiltration membrane in an MSC300 ultrafiltration apparatus. The filtrate was concentrated in vacuo and dialyzed for 3 days to remove inorganic ions to create CODs.Chemical oxidation is a cost-effective and convenient method for large-scale production that does not require sophisticated devices. Tan et al. made CQDs xidation . In a 10In the production of CQDs, electrochemical oxidation is the most often used technique. This approach has the benefits of high purity, cheap cost, high yield, ease of size modification, and excellent repeatability . Zhou etAlthough it is widely established that ultrasound can generate alternate low-pressure and high-pressure waves in liquids, the development and collapse of small vacuum bubbles are not well understood .l-glutamic acid aqueous (0.45 M) introduced to the reaction kettle through an ultrasonic transducer. The ultrasonic generator remained at 50% power during the reaction. The solution was heated to a particular temperature and then cooled to room temperature when it became yellow and no visible precipitation occurred, indicating the CQDs were formed  from pear juice in a simple and scalable hydrothermal route . In ordel method . The Coc2 conjugated carbon p-p transition and the n-p transition caused by the hybridization with heteroatoms such as N, S, and P, among others. Surface passivation or modification processes can be used to control the absorption property of the surface. He et al. synthesized CODs from lemon juice using a simple hydrothermal treatment at low temperatures and short time  and Cerium (IV) (The chemiluminescence (CL) of CQDs was initially observed when they were mixed with oxidants such as potassium permanganate (KMnOium (IV) . EPR shoium (IV) . The CL ium (IV) .There has been a significant increase in recent years in the amount of research being done on the PL of CQDs, which is one of the most exciting characteristics of CQDs and has been used in the field of photocatalysis . The PL There are some advantages to using CQDs in photocatalysis. CQDs are superior to other typical photocatalysts in terms of water solubility, chemical stability, and low toxicity . After surface modification, CQDs display outstanding and tunable optical characteristics of absorbance and PL. UCPL of CQDs, in particular, may greatly increase the sunlight absorption of wide band gap semiconductors into the visible and near-infrared regions. Photoinduced CQDs are also good electron donors and acceptors, allowing for efficient electron-hole separation. Thus, CQDs can be used as electron mediators, photosensitizers, spectral converters, and sole photocatalysts. In fact, these many impacts often occur concurrently. CQD-based photocatalyst systems are summarized in this section.−1, respectively. The ID/IG value of GQDs was as high as 1.03, indicating GQDs have a crystal structure with some sp2 defects caused by smaller clusters. The GQDs were used as photocatalysts for the degradation of New Fuchsin (NF) dye under visible light. The effects of GQDs, initial NF concentration, pH of dye, and contacting time on the degradation efficiency were investigated. The rate constant and degradation efficiency were rarely affected by NF concentration and only decreased slightly when the initial NF concentration increased.Roushani et al. fabricated graphene quantum dots (GQDs) by pyrolyzing citric acid (CA) as a source of carbon . The CA Elettaria cardamomum in an eco-friendly way by the facile sonication method  and congo red (CR) under visible light irradiation. At the optimal condition , CR degradation took 50 min. However, when the dye was changed to MB with a similar concentration and at 8 pH, degradation took just 5 min more than CR.Zaib et al. synthesized carbon dots (CDs) from n method . The Ele−1 was confirmed by Raman spectroscopy. H-TEM studies showed the presence of graphitic fringes in CDs. The photoactive CDs were used as photocatalysts for the degradation of crystal violet (CV) under solar light. The photoactive CDs degraded 20 ppm of CV in ∼90 min, much faster than the degradation in the dark. According to the active species scavenging experiment, the most important active species engaged in the degradation reactions were photogenerated electrons and holes. The degradation of CV, from aromatic compound to little aliphatic pieces, was confirmed by NMR spectroscopy.Aggarwal et al. prepared photoactive carbon dots (CDs) through a facile, green, and scalable method by charring bitter apple peel . Dried pDas et al. fabricated green-emissive carbon quantum dots (CQDs) from pear juice in a simple and scalable hydrothermal route  and H-TECoccinia grandis extract by a simple hydrothermal method  from l method . Accordivia a simple and eco-friendly hydrothermal process. The Pomelo juice was held in a Teflon-lined autoclave at 200°C for 7 h and centrifuged for 30 min at 12,000 rpm to make UCQDs. The Pomelo juice and ammonium bicarbonate were held in a Teflon-lined autoclave at 200°C for 7 h and centrifuged for 30 min at 12,000 rpm to make NCQDs. In the XRD results, the peak at 22.4° and the peaks at 12.6° and 28.2° confirmed the presence of amorphous carbon in UCQDs and NCQDs, respectively. According to TEM results, UCQDs and NCQDs had average diameters of 3 and 70 nm, respectively. The Raman spectroscopy demonstrated that the D-band, corresponding to disordered carbon, was shifted from 1,354 to 1,335 cm−1, and the G-band, corresponding to graphitic carbon, was shifted from 1,571 to 1,563 cm−1 when CQDs were N-doped. Both CQDs acted as good photocatalysts for the degradation of methylene blue (MB) under solar light, which followed pseudo-first-order kinetics. CQDs showed brilliant photocatalytic performance because they have high transfer efficiency of photoinduced electrons and remarkable sunlight absorption abilities.−1, which represents a disordered band of carbon, and a weaker D-band at 1,369 cm−1, which represents a graphitic band of carbon. The properties of PDNCDs could be precisely tuned using different solvents. PDNCDs were used as catalysts for the reduction of Safranin-O dye with NaBH4. Safranin-O was reduced in 6 min, which was better than that of pure NaBH4 and undoped CDs. The catalytic activity of PDNCDs came from their ability to transfer electrons from NaBH4 to Safranin-O.Dhanush et al. prepared fluorescent phyto-derived nitrogen-doped carbon dots (PDNCDs) from neem seeds using a green hydrothermal method . The nee−1. The degradation efficiency was maintained at 93% during five degradation cycles. The Cl-CQDs displayed the highest MB and IC degradation efficiency of 56% and 60%, respectively. The photocatalytic performances of N-CQDs and Cl-CQDs were better than that of pristine CQDs because the electric field was generated in N-CQDs and Cl-CQDs.Cheng et al. synthesized fluorescent nitrogen-doped carbon quantum dots (N-CQDs) and chlorine-doped carbon quantum dots (Cl-CQDs) from aqua mesophase pitch (AMP) through a hydrothermal process . The AMPBhati et al. prepared red-emitting-magnesium-nitrogen-embedded carbon dots (r-Mg-N-CD) in an eco-friendly way . Bougain12 was held in a quartz boat for 2 h at 250°C; was hydrolyzed with NaOH for 24 h at 80°C; and went through filtration, dialysis for 3 days, and freeze-drying to make CoSAS@CD. The TEM results showed that CoSAS@CD were spheres with the size of 9.0 nm. According to XRD results, the broad peak at 22° confirmed that CoSAS@CD was slightly graphitic. XPS results revealed that the elemental composition of CoSAS@CD was 64.73, 9.05%, 22.03%, and 4.19% for C, N, O, and Co, respectively. The photoluminescence (PL) results demonstrated that CoSAS@CD exhibited the strongest emission at 415 nm when the excitation wavelength was 300 nm. The CoSAS@CD was used as a photocatalyst for thee oxidation reactions under visible light irradiation. The CoSAS@CD exhibited high oxygen evolution rate of 168 μmol/h/g during the water oxidation reaction, high conversion of ∼90%, and high selectivity over 99% in imine formation reaction and oxidation degradation time of 10 min against RhB. The excellent photocatalytic activity of the CoSAS@CD came from improved visible light-harvesting ability and enhanced photoinduced charge transfer and separation.Wang et al. developed single cobalt atoms anchored carbon dots (CoSAS@CD) . VitaminZhu et al. fabricated S/Cl co-doped biomass-based CDs (Bio-CDs) using palm powders through the hydrothermal process . Palm pod-glucose anhydrous via hydrothermal treatment  and P-doped carbon nano-dots (P-CD) from reatment . Glucose−2 and 2.4 × 10−2 min−1. The “B-doped” C-dots showed good photocatalytic activity, which was better than other C-dots photocatalysts and comparable to metal-containing photocatalysts.Peng et al. synthesized “B-doped” carbon dots (C-dots) through a hydrothermal treatment . Citric 3, and CQDs were stirred for 36 h and filtered. Then, the precipitate was washed with CHCl3 and dried at 40°C in a vacuum for 24 h to make CQDs modified with PH (CQDs-PH). XPS result revealed that the elemental composition of CQDs was 57.6% and 42.4% for C and O, respectively. Raman spectroscopy confirmed the presence of a D-band at 1,354 cm−1 and a G-band at 1,595 cm−1, corresponding to disordered graphitic carbons, respectively. HTEM result demonstrated the presence of lattice fringes of graphene in CQDs. According to photoluminescence (PL) spectroscopy results, CQDs exhibited the strongest emission at 452 nm when the excitation wavelength was 360 nm. The CQDs/peroxymonosulfate (PMS) system was used in the photo-degradation of dyes under visible light irradiation and showed good photocatalytic activity and high stability. The alkaline condition was preferred in dye degradation because the alkaline condition promoted the separation of charge. CQDs modified with phenylhydrazine (CQDs-PH) displayed the strongest photocatalytic PMS activation for methylene blue (MB) degradation, showing a degradation time of ∼5 min. By radical quenching tests, the MB degradation mechanism was revealed. Photogenerated electrons were reacted with PMS to produce O2∙−. Then, O2∙− and photogenerated h+ degraded MB.Han et al. prepared carbon quantum dots (CQDs) by a simple and scalable method . Maltitovia a simple and cheap hydrothermal method  under visible light. The TiO2-wsCQDs nanocomposite displayed degradation efficiency that was about 2.5 times higher than that of TiO2 nanofibers. The photocatalytic performance was enhanced because wsCQDs promoted charge separation.Tyagi et al. prepared water-soluble carbon quantum dots (wsCQDs) from lemon peel l method . The lem2 nanotubes (CQDs/TNTs) nanocomposite by an enhanced hydrothermal method by anchoring CQDs onto the outer surface of TNTs  plane of TiO2 and (100) plane of CQDs. Energy dispersive spectroscopy (EDS) revealed that the elements weight of CQDs/TNTs was 20.3%, 63.31%, and 16.39% for Ti, O, and C, respectively. XRD pattern of CQDs/TNTs exhibited characteristic peaks of TiO2 at 25.1°, 28.2°, 39.39°, and 48.42°. The CQDs/TNTs nanocomposite was used as a photocatalyst for the degradation of 30 mg/L methylene blue (MB) under visible light irradiation. The CQDs/TNTs-0.2 (0.2 g of TNTs) showed the highest MB degradation efficiency of 91.3% in 50 min, which was two times higher than that of pristine TNTs. The photocatalytic performance was improved because the up-conversion photoluminescence (UCPL) properties of CQDs enabled more efficient use of visible light. Furthermore, the photoinduced electrons of TNTs were transferred to CQDs, and the electron-hole recombination was delayed. The π-π stacking between CQDs and dyes enhanced the adsorption ability of the CQDs/TNTs nanocomposite.Zhao et al. developed a carbon quantum dots/TiO of TNTs . TiO2 na2 (CDs/N-TiO2) nanocomposite , (004), (200), (105), (211), (204), and (215) planes of anatase phase. HTEM images confirmed the (101) plane of the anatase and (100) plane of the graphene carbon. According to XPS results, the CDs/N-TiO2 contained C, O, N, and Ti. Photoluminescence (PL) spectra revealed that 30CDs/N-TiO2 exhibited the lowest PL intensity, indicating the lowest recombination rate of charge carriers, which are used for photocatalytic degradation. The CDs/N-TiO2 nanocomposite was used as a photocatalyst for the degradation of 10 mg/L rhodamine B (RhB) under visible light and the reduction of 20 mg/L Cr (Ⅵ) under sunlight. The 30CDs/N-TiO2 (30 μL of CDs) nanocomposite displayed RhB degradation efficiency of 99.8% in 5 min, which was higher than that of TiO2 (6.66%) and N-TiO2 (19.97%). The 30CDs/N-TiO2 nanocomposite exhibited kinetic constants of RhB degradation 85.52 and 25.40 times higher than those of TiO2 and N-TiO2. With the 30CDs/N-TiO2 nanocomposite, Cr (Ⅵ) reduction took only 4 min. The photocatalytic activity was enhanced because N doping shifted absorption range to visible light range and made TiO2 behave like a p-type semiconductor to transfer photogenerated electrons to CDs more easily. Moreover, CDs stored received electrons to promote the photo-induced charge separation.Zhang et al. constructed a carbon quantum dots/nitrogen doping TiOomposite . Ascorbi−1, corresponding to disordered carbons, and G-band at 1,550 cm−1, corresponding to graphite carbons. TEM image demonstrated that nanoparticles were successfully introduced to the active blend. Sodium alginate, sodium citrate, and TiO2 nanopowder were sonicated for 30 min and added dropwise into the mixture of CaCl2·2H2O, water, and ethanol to make TiO2 macro beads. The mixture of oxide beads and the active blend was stirred for 1 h and dried in air overnight to make oxide beads functionalized with the active blend. Alginate-based TiO2 macro beads, a photocatalyst for degradation of cationic pollutants, functionalized with the active blend showed better photocatalytic effect and adsorptive ability in mild conditions than the oxide beads functionalized with each component of the active blend or carbon dots prepared through energy-consuming hydrothermal synthesis. Functionalized TiO2 macro beads showed methylene blue (MB) dye adsorption capability of 82% and completely degraded MB in 30 min.Vassalini et al. synthesized an active blend consisting of carbon-based nanoparticles, alginate, and organic acids in an eco-friendly way . Sodium 2 (N-CDs/TiO2) composite from urea and tetrabutyl titanate (TBT) through hydrothermal treatment  and (101) crystal facets of rutile appeared as N-CDs content increased. The SEM images showed that, as N-CDs content increased, the morphology of the N-CDs/TiO2 composite changed from nano sphere agglomerations, honeycomb, to empty spheres (2-6 (mass ratio of urea to TBT = 6) was 71.96%, 2.6%, 18%, and 7.44% for C, N, O, and Ti, respectively. The photoluminescence (PL) spectra demonstrated that emission intensity decreased as N-CDs content increased. The N-CDs/TiO2 composite was used as a photocatalyst for the degradation of rhodamine B (RhB) under visible light. N-CDs/TiO2-1 degraded RhB in 120 min, which was 11.42 times better than pristine TiO2.Ouyang et al. fabricated a nitrogen-doped carbon quantum dots/TiOreatment . The mix spheres . The XPS2 nanocomposites in a simple and eco-friendly way by depositing NCQDs onto TiO2 nanosheets  peak of anatase and (110) peak of rutile. H-TEM images revealed that NCQDs/TiO2 nanocomposite exhibited (101) crystal planes of anatase, (111) crystal plane of rutile, and (101) plane of carbon. XPS result demonstrated that NCQDs/TiO2 nanocomposite contained C, O, N, S, and Ti. According to photoluminescence (PL) spectra, emission intensity decreased as NCQDs content increased. The NCQDs/TiO2 nanocomposite was used as a photocatalyst for the photoreduction of CO2 under simulated sunlight. The maximum amounts of CH4 and CO produced by the CO2 photoreduction using the nanocomposite in 1 h were 0.769 and 1.153 μmol, respectively, which were 7.79 and 7.61 times higher than those using only TiO2. The nanocomposite showed improved photocatalytic activity because NCQDs sensitized TiO2 to have enhanced light absorption.Li et al. prepared nitrogen and sulfur-containing carbon quantum dots (NCQDs)/TiOnosheets . Citric 3+. The NP-CQDs exhibited detection range from 0.05 to 200 μM. NP-CQDs and titanium butoxide were held in a Teflon-lined autoclave for 1 day at 160°C, centrifuged, washed with ethanol and water, and dried for 1 day at 60°C to make NP-CQDs/TiO2 nanocomposite. The NP-CQDs/TiO2 nanocomposite was used as a photocatalyst for the degradation of methylene blue (MB) under simulated solar light. The NP-CQDs/TiO2 nanocomposite had a degradation time of 15 min, which was shorter than pristine TiO2.Guo et al. prepared N and P co-doped carbon quantum dots (NP-CQDs) by simple heat treatment . Citric 2 NPs) and carbon dots (CDs) deposited polyvinyl imidazole cross-linked chitosan (cl-Ch-p (VI)/TiO2NPs-CDs) /TiO2NPs-CDs. XRD pattern of cl-Ch-p (VI)/TiO2NPs-CDs showed a peak at 24.1°, corresponding to (002) plane of carbon and (101) plane of anatase TiO2, and peaks at 37.5°, 47.7°, 53.9°, 62.6°, and 74.5°, corresponding to (004), (200), (105), (204), and (215) planes of crystalline TiO2 NPs, respectively. TEM image revealed that CDs and TiO2 NPs were introduced to the polymer matrix. XPS result demonstrated that cl-Ch-p (VI)/TiO2NPs-CDs contained C, N, O, and Ti. The cl-Ch-p (VI)/TiO2NPs-CDs nanocomposite was used as a photocatalyst for the degradation of organic materials under solar light. The cl-Ch-p (VI)/TiO2NPs-CDs nanocomposite showed degradation efficiency of ∼98.6%, ∼95.8%, and ∼98.2% for 2,4-dichlorophenol, reactive blue 4, and reactive red 15, respectively, which were better than those of cl-Ch-p (VI)/TiO2NPs and cl-Ch-p (VI)/CDs composites. The improved photocatalytic activity was due to the synergistic effects of CDs and TiO2 NPs and narrowed band gap.Midya et al. constructed titania nanoparticles (TiONPs-CDs) . The mix2(P25)/reduced graphene oxide (rGO) nanocomposite through a simple hydrothermal process , methylene blue (MB), and methyl orange (MO), and antibacterial performance under visible light. The 2% CDs/0.5% rGO/P25 composite showed the best photocatalytic activity. The rate constant of 2% CDs/0.5% rGO/P25 for Rh-B degradation was 29, 2.8, and 1.3 times higher than that of P25, rGO/P25, and CDs/P25, respectively. The CDs/P25/rGO nanocomposite displayed enhanced photocatalytic activity because CDs improved visible light-harvesting ability and promoted photogenerated charge separation.Zhu et al. prepared a multiplecore@shells clustered carbon dots (CDs)/TiO process . Citric 2 nanoparticles (CQDZ) by a simple method , (020), and (120) planes of ZrO2 nanoparticles. The Raman spectrum of CQDZ confirmed the presence of G- and D-bands at 1,550 and 1,356 cm−1, corresponding to graphitic carbon and disordered carbon, respectively. CQDZ was used as a photocatalyst for the elimination of a dye, methylene blue (MB), in water under UV light. Using CQDZ, 95% of MB was eliminated after 1 h. Using pristine ZrO2 nanoparticles, however, only 34% of MB was eliminated after 1 h. The enhanced photocatalytic activity of CQDZ might be due to the CQDs effect of slowing down the electron-hole recombination.Ratnayake et al. synthesized carbon-quantum-dot-decorated ZrOe method . The col3−δ (CDs_BZO) hybrid nanomaterials by loading CDs on BZO hollow nanospheres, which were both hydrothermally synthesized  spectrum, CDs_BZO displayed a strong emission at 460 nm when the excitation wavelength was 340 nm. The FETEM images revealed that BZO were hollow spheres, and CDs were spheres with diameters of ∼2–7 nm shown in 2 generation and methylene blue (MB) dye degradation under UV-visible light. The CDs_BZO with 3 wt% CDs had the highest hydrogen generation efficiency of 670 μmol/h/g with apparent quantum yield (AQY) of ∼4%, which was higher than AQY of BZO (∼2%). It also showed the highest MB degradation efficiency of ∼90%. Here, the defect states and oxygen vacancies generated by hydrothermal synthesis enable visible light absorption of the photocatalyst, and CDs improve the light absorption of the photocatalyst.Patra et al. prepared carbon dots_BaZrOthesized . Citric 3  composite by simple hydrothermal synthesis  spectrum, PL intensity of N,Fe-CDs/G-WO3 was reduced after loading of N,Fe-CDs. The N,Fe-CDs/G-WO3 composite was used as a photocatalyst for degradation of rhodamine B (RhB) under UV-vis-NIR light. 81.4%, 97.1%, and 75% of RhB were degraded in 2 h under UV, visible, and NIR light, respectively, which were better than those of commercial WO3, G-WO3, and N-CDs/G-WO3 composites. The composite was also used for the degradation of methylene blue (MB), ciprofloxacin (CIP), tetracycline hydrochloride (TCH), and oxytetracycline (OTC) under visible light. 91.1%, 70.5%, 54.5%, and 47.8% of respective materials were degraded in 3 h. According to the radical trapping experiments, the conversion between Fe (III) and Fe (II) is the most important factor in photocatalysis. The photocatalytic activity was improved because N,Fe-CDs enhanced light absorption ability, and the gear shape of the WO3 increased light reflections.Ni et al. synthesized nitrogen and iron co-doped carbon dots/gear-shaped WOynthesis . Na2WO4·3/graphene oxide/N-doped carbon quantum dots (WO3/GO/NCQDs) composite by introducing NCQDs to GO modified WO3 nanosheets  intensity of WO3/GO/NCQDs decreased when NCQDs content increased. According to Raman spectroscopy, WO3/GO/NCQDs displayed D- and G-band at 1,435 and 1,575 cm−1, corresponding to disordered carbon and graphitic carbon, respectively. The WO3/GO/NCQDs composite was used as a photocatalyst for the degradation of methyl orange (MO) under visible light irradiation. The WO3/GO/NCQDs composite with 1.5 ml NCQDs showed the best degradation efficiency of 86%. The WO3/GO/NCQDs composite exhibited better photocatalytic activity than WO3/GO composite and WO3. The photocatalytic effect was improved because NCQDs extended the absorption region to the visible light region, increased active sites, and promoted charge separation.Jamila et al. constructed a WOnosheets . GraphitVelumani et al. constructed carbon quantum dots supported ZnO hollow spheres (ZnO/C-dots) by a solvothermal process . Glucose3COO)2·2H2O in methanol was adjusted to pH 8 using NaOH, held in a Teflon-lined autoclave for 6 h at 200°C, washed with methanol, filtered, and dried at 60°C in an oven to make the ZnO nanoparticles. Grounded coffee and concentrated phosphoric acid were kept in a water bath for 30 min at 90–95°C, filtered, centrifuged for 30 min at 14,000 rpm, adjusted to pH 1–3, and dialyzed with dialysis membrane for 5 h to make CDs. ZnO and CDs were stirred for 2 h to make the ZnO-CDs nanocomposite. The TEM result showed that CDs and ZnO had diameters of 3–4 nm and 15–20 nm. The XRD pattern of ZnO-CDs nanocomposite displayed characteristic peaks of both ZnO and CDs. According to the XPS result, CDs contained C, O, N, and P.Omer et al. prepared a ZnO-phosphorous and nitrogen co-doped carbon quantum dots (CDs) nanocomposite in an eco-friendly way . Zn irradiation. The ZnO-CDs nanocomposite exhibited methylene blue (MB) degradation efficiency of 80% in 10 h, which was much higher than that of pristine ZnO (10%). The photocatalytic activity was enhanced because CDs promoted photogenerated charge separation and transfer, and CDs’ up-conversion properties improved light absorption.Dots/ZnO2) composite by introducing CDots to ZnO2 nanoparticles  plane of graphitic carbon, and peaks corresponding to (111), (200), (220), and (311) planes of crystalline ZnO2. The TEM image of CDots/ZnO2 composite revealed the (110) plane of graphitic CDots and (111) plane of ZnO2. The energy dispersive spectroscopy (EDS) result demonstrated that CDots/ZnO2 composite contained C, O, and Zn. According to the up-conversion photoluminescence (PL) spectra, CDots absorb NIR light and emit light with a shorter wavelength. The CDots/ZnO2 composite was used as a photocatalyst for the degradation of methyl orange (MO), methylene blue (MB), and rhodamine B (RhB) under UV-A light irradiation. The CDots/ZnO2 composite exhibited better degradation efficiencies for MO (91 ± 2% in 60 min), MB (99 ± 1% in 50 min), and RhB (99 ± 1% in 80 min) than ZnO2, TiO2, and CDots/TiO2 due to promoted charge separation by CDots and ZnO2, electron capturing and up-conversion photoluminescence by CDots, and the CDots/ZnO2 structure advantageous to charge transfer and separation. The CDots/ZnO2 composite could be used five times without any decrease in photocatalytic performance.El-Shamy et al. developed a carbon quantum dots/zinc peroxide (Carticles . d-Gluco2) films by introducing CZnO2 to PVA (3COO)2∙2H2O, triple-distilled water, H2O2, NaOH, and ethanol was held in a 400 W microwave oven for 3 h at 180°C, filtered, washed with water, and dried for 1 day at 60°C in an oven to make ZnO2. ZnO2 solution and carbon dot solution were mechanically stirred for 1 h, centrifuged, filtered, washed with ethanol, and dried in air to make CZnO2. PVA and triple-distilled water were stirred at 67 ± 3°C for 2 h, transferred to glass dishes, and air-dried for 3 days at ambient temperature to make PVA. CZnO2 was dispersed in PVA solution, transferred to glass dishes, and air-dried for 3 days to make PVA/CZnO2. XRD pattern of PVA/CZnO2 exhibited a peak at 19.5° for (101) plane of PVA and peaks of ZnO2. FE-SEM images showed that CZnO2 particles were uniformly dispersed on PVA matrix.El-Shamy et al. developed polyvinyl alcohol/carbon dot-decorated zinc peroxide . The PVA/CZnO2 nanocomposite with 4 wt% CZnO2 exhibited an adsorption capacity of 1,972 ± 40 mg/g against methylene blue (MB), which was higher than that of the PVA/ZnO2 nanocomposite with 4 wt% ZnO2 . At pH = 6, room temperature, with low ionic strength, 40 mg of PVA/CZnO2 nanocomposite eliminated 98% of 2,000 mg/L MB in 60 min. The enhanced adsorption ability came from improved electrical conductivity, crystallinity, pore size, and mechanical properties. A solution with pH = 1 removed 75% of MB from the nanocomposite, and the nanocomposite could be used five times with only a slight decrease in adsorption efficiency (∼2%).According to Brunauer–Emmett–Teller (BET) analysis, the PVA/CZnOd-glucose, acetone, and bi-distilled water was heated in a 700 W microwave oven for 13 min and centrifuged to make CQDs. The mixture of PVA solution and CQDs solution was mechanically stirred and dried for 3 days at ambient temperature to make PVA/CQDs. XRD pattern of PVA/CQDs showed a broad peak at 19.5°, corresponding to the crystalline part of semi-crystalline PVA. According to photoluminescence (PL) spectra, as CQDs content increased, PL intensity increased and PL peak exhibited red shift behavior. FE-SEM images revealed that, as CQDs content increased, the surface area of PVA/CQDs increased. The PVA/CQDs nanocomposite films were used for the elimination of methylene blue (MB) from waste water by adsorption at room temperature. The 80 mg of (PVA/CQDs 2 wt%) film eliminated 97 ± 1% of 30 mg/L MB in 40 min at pH = 12. In the basic environment, -OH groups in PVA and -OH groups or -COOH groups in CQDs were ionized, making the composite surface more negatively charged. This made the composite more easily adsorb cationic MB. The PVA/CQDs nanocomposite films could be used five times after ethanol treatment without any photocatalytic activity decrease.El-Shamy et al. constructed polyvinyl alcohol/carbon quantum dots (PVA/CQDs) nanocomposite films using the solution casting method . PVA and4 under stirring at ambient temperature for 1.5 h, and dialyzed for 6 h to make carboxylate-PVP. The mixture of carboxylate-PVP, EDC, MES buffer, and NHS was dialyzed with water for 18 h, concentrated at 60°C in a vacuum, treated with water, and held in an air oven at 75°C to make PVP-CD. For PVP-CD, storage modulus was higher than loss modulus, indicating the elasticity of PVP-CD. PVP-CD emitted blue fluorescence when UV light was illuminated. The SEM image showed that cross-linking with CD has increased the surface area of PVP-CD. 50 mg of PVP-CD hydrogel adsorbed ∼2 mg of malachite green (MG), crystal violet (CV), and eosin Y in 12 h, which followed pseudo-second-order kinetics. The good adsorptive ability came from hydrogen bonding, inductive effect, and π-π interaction of both CD and the PVP backbone. The PVP-CD hydrogel also showed excellent photodegradative capability of dyes under solar light by degrading them in 30 min, which followed pseudo-first-order kinetics. The PVP-CD hydrogel killed gram-positive and gram-negative bacteria in 10 min under solar light. The degradation of dyes and bacterial elimination were all carried out by reactive oxygen species generated from CD. The PVP-CD hydrogel could be used four times when washed with dilute acid.Nayak et al. fabricated carbon quantum dots cross-linked polyvinyl pyrrolidone (PVP-CD) hydrogels . Lemon jvia hydrothermal process  under visible light. The reaction constant of CDs/CeO2 composite was much higher than that of CeO2.Gong et al. fabricated carbon quantum dots (CDs) from wood powder  process . The mixJamila et al. prepared copper oxide/N-doped carbon quantum dots (CuO/NCQDs) by introducing NCQDs into CuO nanoleaves . Copper 3 composite in mixed-calcination and hydrothermal routes by anchoring CQDs on KNbO3  spectra, when excitation wavelength was 400–500 nm, CQDs exhibited down-conversion PL. When excitation wavelength was 500–600 nm, CQDs exhibited up-conversion PL. The TEM result showed that CQDs were well dispersed on the surface of KNbO3 particles. EDX result revealed that the elemental composition of CQDs/KNbO3 composite was 19.40%, 23.26%, 21.89%, and 35.45% for C, Nb, K, and O, respectively. The CQDs/KNbO3 composite was used as a photocatalyst for the degradation of crystal violet dye and hydrogen evolution under visible light. When the mass ratio was CQDs: KNbO3 = 1.5:0.5, the dye degradation efficiency and hydrogen evolution rate were 70.00% and 468.72 μmol/h/g, which were higher than those of pristine KNbO3 (41.50% and 245.52 μmol/h/g). The photocatalytic performance was enhanced because CQDs converted visible light to UV light, which could activate KNbO3, and captured electrons to help the separation of electron-hole pairs. The CQDs/KNbO3 composite could be used four times without a significant decrease in performance.Qu et al. fabricated a carbon quantum dots (CQDs)/KNbOon KNbO3 . The mix3N, and BDA was dried at 40°C under vacuum; transferred to a sintered funnel; washed with water, hexane, and diethyl ether; dissolved in methanol, and dried again at 40°C under vacuum to make CD-CONH. The mixture of CD-CONH, ethanol, and PdCl2 was dried at 40°C under vacuum, transferred to a sintered funnel, washed with water, and dried for 12 h at 60°C in a vacuum oven to make Pd@CD-CONH. The PXRD patterns showed peaks corresponding to (100), (111), (200), (220), (311), and (222) planes of Pd NPs. According to the HTEM result, Pd@CD-CONH exhibited lattice fringes of the (111) plane  by cross-linking carbon dots (CDs) with benzene-1,4-diamine (BDA) and doping the resulting polymer with palladium nanoparticles (Pd NPs) . The mix1) plane . The Pd 1) plane . The XPS4, AgNO3, or H2PdCl4 was added to the mixture of water, ethanol, and MIL-53(Fe)/CQDs, illuminated with 300 W xenon lamp for 60° min, treated with N2, washed with ethanol, and blow-dried by N2 to make MIL-53(Fe)/CQDs/MNPs. The zeta potential of CQDs (−14.8°mV) indicated a negative charge, and the zeta potential of MIL-53(Fe) (4.6 mV) indicated a positive charge. Therefore, CQDs and MIL-53(Fe) were combined readily by electrostatic attraction. XRD pattern of MIL-53(Fe)/CQDs/Au showed peaks corresponding to MIL-53(Fe), a weak peak at 26° corresponding to carbon, and a weak peak at 38.1° corresponding to (111) crystal planes of Au. TEM images revealed that noble metal particles were dispersed on MIL-53(Fe)/CQDs. XPS result demonstrated that MIL-53(Fe)/CQDs/MNPs contained C, O, Fe, and noble metal. With the MIL-53(Fe)/CQDs/2%Au (mass ratio of Au to MIL-53(Fe)/CQDs = 2%) photocatalyst, almost 100% of Cr (VI) was reduced in 20 min under visible light irradiation. The MIL-53(Fe)/CQDs/2%Au displayed a rate constant of 0.1820 min−1, which was about 7.4, 2.76, 1.77, and 1.47 times higher than that of MIL-53(Fe), MIL-53(Fe)/CQDs, MIL-53(Fe)/CQDs/2%Ag, and MIL-53(Fe)/CQDs/2%Pd. It was revealed that the MIL-53(Fe)/CQDs/2%Au could also eliminate Cr (VI) and dyes at the same time. The enhanced photocatalytic activity came from increased light absorption, the high electrical conductivity of CQDs and gold, and the surface plasmon resonance effect of gold.He et al. synthesized a MIL-53(Fe)/carbon quantum dots/noble metal (MIL-53(Fe)/CQDs/MNPs) photocatalyst in a simple way . The mix3 solution for 1 h at 80°C, diluted using deionized water, treated with NaOH, centrifuged for 5 min at 8,000 rpm, and washed with water to make CCN. The SEM images with element mapping showed that CQDs were uniformly distributed on graphitic carbon nitride. XRD pattern of CCN exhibited peaks at 13.1° and 27.5°, corresponding to <002> and <100> crystal planes of graphite. XPS result revealed that CCN contained C, N, and O. The CCN was used as a photocatalyst for the degradation of methylene blue (MB) and rhodamine B (RhB) and hydrogen evolution under visible light irradiation. The 4CCN (0.98 wt% CQDs) showed the shortest MB degradation time of 20 min and the highest hydrogen evolution rate of 1,291 μmol/h/g. The CCN had better performance than pristine graphitic carbon nitride because CQDs increased visible light absorption and promoted photogenerated charge separation and transfer.Zhang et al. prepared carbon quantum dots (CQDs) modified graphitic carbon nitride (CCN) in a simple way . Citric 3N4) composite through a hydrothermal method  and (002) planes of graphite. Photoluminescence (PL) spectrum revealed that PL intensity of NCQD/g-C3N4 decreased after NCQDs loading. The NCQD/g-C3N4 composite was used as a photocatalyst for the degradation of methylene blue (MB) under LED light. The 1°wt% NCQD/g-C3N4 (1°wt% NCQD) exhibited the highest MB degradation efficiency of 54.6%, which was 2.6 times higher than that of pristine g-C3N4. The 1°wt% NCQD/g-C3N4 displayed an MB degradation rate constant of 5.061 × 10−3 min−1, which was 3.85 times higher than that of pure g-C3N4. The improved photocatalytic activity was due to increased speed of charge transfer, suppressed electron-hole recombination, and optimized heterojunction interface between g-C3N4 and NCQD. When the 1wt% NCQD/g-C3N4 was used for thee times, the degradation efficiency was 91.2% of original efficiency, showing high stability of the composite.Seng et al. developed a nitrogen-doped carbon quantum dots-decorated 2D graphitic carbon nitride (NCQD/g-Cl method . The mix3N4 nanosheet (GA-CQDs/CNN) aerogel by a simple hydrothermal method  and (100) planes of pristine CNN. XPS result showed that GA-CQDs/CNN contained C, O, and N. HTEM image revealed a distinguished interface between reduced GO and CNN. According to photoluminescence (PL) spectra, GA-CQDs/CNN displayed the PL quenching phenomenon. The GA-CQDs/CNN was used as a photocatalyst for the degradation of methyl orange (MO) under visible light irradiation. The GA-CQDs/CNN-24% (mass ratio of GO to CNN = 24%) exhibited MO degradation efficiency of 91.1%, which was 7.6 times higher than that of bulk g-C3N4. The GA-CQDs/CNN also displayed high adsorption capacity. The photocatalytic and adsorptive performance was improved because the large specific surface area of the porous structure was advantageous for light absorption and material adsorption. Moreover, the large planar interface between CNN and GO promoted photoexcited charge transfer and separation, and CQDs enhanced light absorption and charge separation. The GA-CQDs/CNN could be used for four cycles without a significant decrease in performance.He et al. constructed a 3D graphene oxide- (GO-) carbon quantum dots/g-Cl method . EDTA-2N3N4)/Ag3PO4/nitrogen-doped carbon dots (NCDs) photocatalyst by a simple solution process by anchoring NCDs onto g-C3N4/Ag3PO4 photocatalyst , rhodamine B (RhB), and phenol under visible light. 10 mg L−1 MB solution and 10 mg L−1RhB solution were degraded in 20 and 15 min, respectively, and 64% of 50 mg L−1 phenol solution was degraded in 80 min, much faster than other catalysts such as Ag3PO4 and g-C3N4/Ag3PO4. The g-C3N4/Ag3PO4/NCDs photocatalyst showed enhanced performance because NCDs have increased molecular oxygen activation, promoted charge transfer, and improved light absorption capacity. The photocatalyst could be used up to four times without a significant decrease in performance, suggesting that the photocatalyst has high stability.Miao et al. synthesized an all-solid-state Z-scheme graphitic carbon nitride /nitrogen-doped carbon dot (NCD) photocatalyst by depositing NCDs on Ag3PO4/GO composite  spectra, Ag3PO4/GO/NCD exhibited lower PL intensity than its components. The Ag3PO4/GO/NCD photocatalyst was used for the degradation of methylene blue (MB), rhodamine B (RhB), and phenol under visible light. 10 mg L−1 MB solution, 10 mg L−1 RhB solution, and 50 mg L−1 phenol solution were degraded in 2.5, 5, and 120 min, respectively, which were much faster than those of Ag3PO4 and Ag3PO4/GO. The photocatalytic activity was improved because NCDs increased the oxygen activation, enhanced light absorption capacity, and suppressed photoinduced electron-hole pairs recombination. The Ag3PO4/GO/NCD photocatalyst could be used four times without a significant decrease in photocatalytic activity, showing the high stability of the photocatalyst.Miao et al. developed an all-solid-state Z-scheme Agomposite . The mixJana et al. prepared CuO-associated carbon dots (CDCs) in an eco-friendly way . The mix2) by compounding m-TiO2 with N-CDs . The mixture N-CDs and m-TiO2 was transferred into the heating mantle at a set temperature of 60°C for 12 h by the thermal deposition technique. XRD of N-CDs/m-TiO2 exhibited peaks at 25.3°, 48.1°, 53.8°, 55.2°, and 62.8°, corresponding to (101), (200), (105), (211), and (204), respectively for the anatase TiO2. For the FTIR spectra of N-CDs/m-TiO2, the additional peak appears at 1,050 cm−1, corresponding to bending vibration of C-NH-C, and the absorption peak appears between 3,600 and 3,300 cm−1 for the TiO2 NPs and m-TiO2 for a fact at N-CDs use capable of enhancing charge transfer rate as well as CQDs beneficial for promotion photocatalytic efficiency of TiO2. The N2 adsorption-desorption isotherm of N-CDs/m-TiO2 demonstrates the hysteresis loops at relative pressure 0.2 with type IV adsorption-desorption having uniform pore size distribution. For the UV-DRS spectra of N-CDs/m-TiO2, the threshold wavelength (λg) of N-CDs/m-TiO2 was 511.49 nm and band gap energy (Eg) was 2.42 eV. The N-CDs/m-TiO2 shows the higher photo-anode, photocurrent intensity. There was a higher photochemical activity of N-CDs/m-TiO2 due to its unique porous structure and sensitization of N-CDs. The N-CDs/m-TiO2 shows excellent photovoltaic conversion efficiency and stability.Zhang et al. prepared a first-time novel synergistic catalyst , tert-butanol (TBA), and p-benzoquinone (BQ) were employed as h+, OH·, and O2 scavengers, respectively. The luminescence property of N-CDs/m-TiO2 significantly enhanced photocatalytic performance due to the synergistic effect between N-CDs sensitization and the unique porous structure of m-TiO2. In MB containing aromatic ring is responsible for the π-π conjugated structure with the π orbitals of N-CDs, and hence enhancing the photocatalytic activity of N-CDs/m-TiO2 on the MB surface.The photocatalytic performance of N-CDs/m-TiO3N4/SnO2 photocatalyst (CDs/g-C3N4/SnO4) using the thermal polymerization method , urea (U), and DI water held in a Teflon-lined stainless steel autoclave at 180°C for 5 h. CDs/CN/SnO2 was prepared using CSn20 and CDs with ethanol heated at 60°C for evaporating ethanol and then heated at 300°C for 3 h. CDs/CN (CCN) and CDs/SnO2 (CSnO2) were prepared by the same method to make 0.5 CCSn20. The TEM, HTEM, and FPT pattern clearly shows the hexagonal crystalline structure of CDs (3N4 and SnO2 assigned (110) planes. XRD spectra of 0.5 CCSn20 show that a high purity crystalline state of materials was synthesized. The N2 adsorption-desorption isotherms of 0.5 CCSn20 photocatalysts showed a higher specific surface area (53.717°m2/g). XPS spectra reveal that 0.5 CCSn20 contains C, N, O, and Sn3d. UV-vis DRS for 0.5 CCSn20 increased light absorption capacity more than its components. According to photoluminescence (PL) spectra, 0.5 CCSn20 exhibited lower PL intensity than its components. The 0.5 CCSn20 photocatalyst was used for the degradation of indomethacin (IDM) under visible light. The photocatalytic IDM degradation rate of 0.5 CCSn20 was higher by 70.3% than CN (32.0%).Li et al. synthesized carbon dots modified g-Cn method . Preparae of CDs , confirm2) 2H2O and the alcoholic solution of CQDs was held in a Teflon-lined stainless steel autoclave heated at 100°C for 8 h washed with DI water and ethanol and then vacuum-dried at 60°C for 24 h. XRD of ZnO/CQDs shows the successful formation of ZnO/CQDs diffraction peak at ZnO corresponding to wurtzite ZnO phase (JCPDS-36-1451). Raman spectrum shows prepared ZnO/CQDs nanocomposites are composed at CQDs and ZnO. FTIR spectra results showed CQDs are successfully attached to ZnO nanoparticles. UV-Vis ZnO/CQDs nanocomposites showed higher photocatalytic activity than other components. SEM showed small uniform nanoparticles with a size of 20–30 nm of ZnO/CQDs. HTEM and TEM of ZnO/CQDs formation of carbon layer due to the addition of CQDs are shown in 2 (N–TiO2) at 60% and 55%, respectively. The CODs were loaded on the ZnO surface to the main function for the enhanced photocatalytic activity of ZnO/CQDs because ZnO/CQDs had better performance than ZnO due to CQDs increased photocatalytic activity toward degradation of toxic gas (benzene and methanol) under visible light at RT.Yu et al. prepared ZnO/CQDs nanocomposites for the one-step hydrothermal reaction method . The mix2O4 photocatalyst  spacing of CDs and (311) spacing of NiCo2O4 shown in 2O4 perfectly matches with (JCPDS No. 73-1702) card. XPS result confirmed that CDs/NiCo2O4 nanocomposite contained Ni, Co, C, and O. Electrochemical band structure of the CDs/NiCo2O4 photocatalyst reveals that helps photocatalytic overall water decomposition. According to TPV, the measurement of CDs/NiCo2O4 showed greater photocurrent intensity, and in situ TPV measurement study during the reaction of photocatalytic HER and OER further enhanced the reaction rate after being supported with CDs. The EIS spectra of CDs/NiCo2O4 demonstrates is having lower charge transfer resistance, and hence it showed better photocurrent intensity, and higher overall water decomposition reaction activity. The CDs/NiCo2O4 showed the best possible hydrogen (oxygen evolution) production is up to 62 μmol h−1 g−1 (29 μmol h−1 g−1). The CDs/NiCo2O4 is still stable toward H2 production. According to the TPV test, the CDs enhanced the interface electron extraction by about 0.09 ms, while the maximum electron storage time by CDs is up to 0.7 ms, concluding that CDs enhanced the photocatalytic water decomposition activity.Nie et al. synthesized CDs/NiCocatalyst . Nickel D/IG ratio than AuNPs and CQDs. Photocatalytic oxidation of cyclohexane to cyclohexanone with Au/CQDs composites under visible light is increased could be due to a similar combination and interaction of CQDs and AuNPs. According to PL spectra, CQDs were excellent, as they were quenched by either an electron donor or an electron acceptor. Electrocatalytic studies on Au/CODs composite toward hydrogen peroxide decomposition shows excellent activity under visible-light irradiation than that absence of light irradiation. Au/CQDs composite exhibited high photocatalytic activity selective for oxidation of cyclohexane to cyclohexanone using hydrogen peroxide as oxidant solvent-free. Electrochemical study reveals that visible light enhanced catalytic reaction.Liu et al. prepared metal nanoparticles/carbon quantum dot composite photocatalyst using Au and CQDs . CQDs we−1 of L-CQDs/ZnO, which confirmed strong physical interaction between carbon and zinc atoms. According to XPS results, L-CQDs/ZnO contained Zn, C, O with peaks appears at 1,021.1 eV (Zn2p3/2) and 1,044.2 eV (Zn2p1/2), 284.8 eV, 288.3 eV (C1s) and 531.8 eV, 532.6 eV (O1s). UV-Vis DRS results demonstrated that the L-CQDs/ZnO showed better photocatalytic activity. According to PL results, the L-CQDs/ZnO had lower photogenerated electron-hole pair recombination. The result demonstrated the efficient electron transport caused by the π bond conjugate system of L-CQDs. The L-CQDs/ZnO was used as a photocatalyst for the degradation of phenol under sunlight. The L-CQDs/ZnO’s highest degradation efficiency (60%) completely degrades phenol at 5.5 h compared to ZnO. The L-CQDs/ZnO exhibited better degradation efficiency than ZnO because wt% of CQDs increased charge separation efficiency.Liang et al. prepared ZnO sensitized by carbon quantum dots (L-CQDs/ZnO) by a combination of L-CQDs and ZnO using the hydrothermal method . Zinc oxin situ hydrothermal method (d-Lactose source of carbon and NaOH solution held in Teflon-beaker heated at 80°C for 15 min for the synthesis of CQD. Further to this CQD dispersion added Zn(CH3COO)2 at RT and adjusted pH-10 by addition of 8 M NaOH dropwise with constant stirring for 15 min. The mixture was heated at 80°C for 2 h and added drop-wise silver nitrate under stirring at 80°C for 1 h to make ZnO/CQDs/AgNPs. The XRD pattern of ZnO/CQDs/AgNPs exhibited a peak at 30°, 44.5°, and 64.6°, corresponding to (111), (200), and (220) planes Ag. According to SEM results, ZnO/CQDs/AgNPs had particles size (<50 nm). The EDX results demonstrated that chemical composition consisted of Zn, C, O, and Ag elements. XPS results demonstrated that ZnO/CQDs/AgNPs contained Zn, O, C, and Ag. N2 adsorption–desorption isotherms of ZnO/CQDs/AgNPs ternary achieved the highest surface area compared to the composite of ZnO, Ag, and binary of CQDs. UV-Vis spectra of ZnO/CQDs/AgNPs achieved band gap at 3.22 eV to generate electron-hole pairs. The ZnO/CQDs/AgNPs composite was used for photocatalysis of MB dye under UV-light irradiation. The photodegradation efficiency of MB dye was 98.6% for ZnO/CQDs/AgNPs. ZnO/CQDs/AgNPs photocatalyst achieved higher photocatalytic activity under UV-light irradiation due to the AgNPs, and CQDs reduced the recombination rate of the photogenerated electron-hole pairs and enhanced photocatalytic reactions.Bozetine et al. developed ZnO/CQDs/AgNPs by the green approach of the l method . d-Lacto2MoO6 by simple hydrothermal method (CQDs/Au/BMO) (3)3 5H2O and Na2MoO4 2H2O were added in ethylene glycol, and ethanol stirring was held in an autoclave for 12 h at 2016°C, centrifuged, washed with water and alcohol, and dried overnight in an electric oven at 60°C to make BMO. BMO, HAuCl4, and lysine were added in DI water, maintained pH with added NaOH and NaBH4, centrifuged, washed with water, and dried overnight in an oven at 60°C to make Au/BMO. CDs and Au/BMO were dispersed in ethanol using ultrasonic treatment followed by drying and calcination 2 h at 250°C to make CQDs/Au/BMO. XRD pattern of CQDs/Au/BMO showed peaks at 38.2° and 44.3° corresponding to (111) and (200) planes for Au NPs for Au/BMO and CQDs/Au/BMO. The XPS result demonstrated that CQDs/Au/BMO contained Bi, Mo, O, Au, and C elements. The morphology and EDX of BMO possesses a hierarchical microsphere with an average diameter was about 1–2 mm, CQDs/Au/BMO are similar to that of BMO, EDX indicated that all the elements are uniformly distributed , Au/BMO (45%), and CQDs/BMO (51%). According to PL and EIS spectra, 7% CQDs/Au/BMO showed higher photocatalytic activity due to the interaction of CQDs and Au NPs on the surface of BMO. The EIS result confirmed that CQDs/Au/BMO showed the strongest ability to separate and transfer photogenerated e−/h+ and enhanced photocatalytic activity.Zhao et al. synthesized carbon quantum dots and Au nanoparticles with Bi/Au/BMO) . Citric tributed . Accorditributed . EPR spe3N4 nanosheets (CQDs/BiOCOOH/uCN) photocatalyst by the simple method 3·5H2O is taken in water and stirred for 30 min followed by added CQDs solution. Furthermore the solution was transfer into Teflon lined autoclave and heated at 150°C for 10 h to make CQDs/BiOCOOH/uCN. The SEM image of CQDs/BiOCOOH/uCN showed a flower-like structure. EDS of CQDs/BiOCOOH/uCN contained Bi, O, N, and C elements. HTEM of CQDs/BiOCOOH/uCN demonstrated that the lattice stripes and planes ((102) (110)), (101), and (002)) for BiOCOOH, graphitic carbon, and uCN.XRD pattern of CQDs/BiOCOOH/uCN exhibited peaks at 13.1° and 27.4°, corresponding to (100) and (002) for uCN and board peak 25° for the disorder of carbon. XPS spectra revealed that CQDs/BiOCOOH/uCN contained C, N, Bi, and O elements. The photoluminescence (PL) spectra showed that CQDs/BiOCOOH/uCN exhibited the strongest emission when the excitation wavelength was 460 nm. The CQDs/BiOCOOH/uCN was used as a photocatalyst for the degradation of sulfathiazole (STZ) under LED lamp irradiation. Using the CQDs/BiOCOOH/uCN showed higher photocatalytic activity compared to its composites. The photocatalytic effect was improved because of the formation of heterojunction. Photodegradation efficiencies of STZ at various pH values were studied up to 98%, and the 4-CQDs/BiOCOOH/uCN showed excellent photocatalytic activity, both acidic and alkaline. The degradation efficiency of STZ was checked by adding natural organic matter and inorganic anions, which revealed CQDs/BiOCOOH/uCN was an attractive material for both NOM and IA. The CQDs/BiOCOOH/uCN showed better photocatalyst activity.Hu et al. developed carbon dots-decorated BiOCOOH/ultrathin g-Ce method . MelaminxBr1-x by the one-step in situ co-precipitation method (3)3⋅5H2O in glycol is ultrasonicated for better dispersion and added N-CQDs under stirring for next 2 h to make N-CQDs/BiOIxBr1−x. The XRD spectra of N-CQDs/BiOIxBr1-x exhibited a characteristic peak at 2θ = 26° to 35°. According to SEM images, the N-CQDs/BiOIxBr1-x were nanosheets thickness of about 23 nm. HTEM results demonstrated the presence of lattice fringes and an average diameter of about 7 nm. XPS result demonstrated that N-CQDs/BiOIxBr1-x contained Bi, O, I, Br, C, and N elements. According to the Brunauer–Emmett–Teller (BET) analysis of N-CQDs/BiOIxBr1-x, the large specific surface area was 20.97 m2/g. The N-CQDs/BiOIxBr1-x was used as a photocatalyst for the degradation of phenol under visible light irradiation. The photocatalytic phenol degradation rate of N-CQDs/BiOIxBr1-x was higher 98.7% than its composites. The enhancement of the photocatalytic activity of N-CQDs/BiOIxBr1-x was due to the scattering of light and layered BiOxBr1-x, as well as the internal electric field from N-CQD to BiOxBr1-x.Gao et al. prepared N-CQDs/BiOIn method . Citric After CQDs were discovered in 2004, there have been many investigations on their synthesis, properties, modifications, and applications due to their distinctive optical and electronic properties. This work focuses on recent progress on CQDs-related materials’ synthesis, properties, and applications in photocatalysis. Many simple, low-cost, and scalable synthesis routes of CQDs-related materials have been devised. CQDs exhibited excellent sunlight harvesting ability, tunable PL, UCPL, and efficient photoexcited electron transfer. CQDs can act as a sole photocatalyst or enhance the photocatalytic activity of other photocatalysts as an electron mediator, a photosensitizer, and/or a spectral converter.Despite significant improvement over the previous decade, various issues still require much investigation. Defects in CQDs modify their optical and electrical characteristics dramatically. Despite this, there are no established methodologies or tactics for dealing with CQD issues. Further research on CQD structure synthesis using dense and precise stages is required. CQD modification has sparked much interest in the scientific community. Many applications can benefit from better PL control and efficiency by readily functionalizing and doping CQDs. In the future, the mechanisms of CQD-associated phenotypes will be investigated. The UCPL mechanism of CQDs, for example, is currently unknown. As a result, additional research is needed to determine the photogenerated electron transfer route in the UCPL process. Due to UV absorption, photocatalytic CQDs have a low light-harvesting capability. CQDs that can be triggered in the visible or even in the near-infrared range can be created. This will aid heterogeneous photocatalysts in making use of the solar spectrum. Few studies have been conducted on the photostability of CQD-based nanocomposites, which are difficult to fabricate. The presence of oxygen groups on CQD surfaces may affect photocatalytic activity. The loss of oxygenic functional groups during photocatalysis doubts the photostability of CQD-based photocatalysts. As a result, CQDs will play a significant role in future photocatalytic devices. Innovative, cost-effective, and simple synthetic methodologies, as well as innovative photocatalytic applications for CQDs, will be developed.


Highly transmissible Omicron variants of SARS-CoV-2 currently dominate globally. Here, we compare neutralization of Omicron BA.1, BA.1.1, and BA.2. BA.2 RBD has slightly higher ACE2 affinity than BA.1 and slightly reduced neutralization by vaccine serum, possibly associated with its increased transmissibility. Neutralization differences between sub-lineages for mAbs (including therapeutics) mostly arise from variation in residues bordering the ACE2 binding site; however, more distant mutations S371F (BA.2) and R346K (BA.1.1) markedly reduce neutralization by therapeutic antibody Vir-S309. In-depth structure-and-function analyses of 27 potent RBD-binding mAbs isolated from vaccinated volunteers following breakthrough Omicron-BA.1 infection reveals that they are focused in two main clusters within the RBD, with potent right-shoulder antibodies showing increased prevalence. Selection and somatic maturation have optimized antibody potency in less-mutated epitopes and recovered potency in highly mutated epitopes. All 27 mAbs potently neutralize early pandemic strains, and many show broad reactivity with variants of concern.  •Potent RBD antibodies from Omicron breakthrough vaccinees broadly neutralize VoC•These, possible recall antibodies, are focused in two main clusters•Somatic maturation adapts public antibodies to recover potency•BA.2 > BA.1 ACE2 affinity. BA.2 < BA.1 neutralization by vaccine serum and Vir-S309 Analysis of antibodies from SARS-CoV-2 Omicron breakthrough infections reveals their structural and functional properties as well as ability to neutralize different pandemic strains. Omicron  contains an unprecedented number of mutations concentrated in the Spike (S) gene which carries 30 substitutions plus the deletion of 6 and insertion of 3 residues.Omicron BA.1 was first reported in late November 2021 in Southern Africa and spread explosively around the world, becoming the dominant SARS-CoV-2 variant in the UK by December 17th  with the receptor binding site, at the tip of the receptor binding domain (RBD), in the S1 fragment of S . FollowiSince late 2020, a succession of variants of concern (VoC) have emerged. Some have caused large regional outbreaks  whilst The extensive mutational burden in Omicron S disrupts the activity of the majority of potent neutralizing mAbs, leading to severe knockdown or complete loss of the neutralizing capacity of serum from natural infection or vaccination, contributing to increased transmissibility and explosive spread . Howeverhttps://www.who.int/publications/m/item/weekly-epidemiological-update-on-covid-19---1-february-2022). Compared to BA.1, BA.1.1 contains an additional R346K mutation , whilst BA.2 bears 8 unique mutations in S  and is estimated to account for approximately 93.7% of cases in England (https://www.gov.uk/government/news/covid-19-variants-identified-in-the-uk).As of February 2022, two sub-lineages additional to BA.1 have been identified: BA.1.1 and BA.2 , together with BA.1, BA.1.1, and BA.2 viruses using sera collected from vaccinees 28 days following third doses of the Oxford/AstraZeneca AZD1222 (n = 41) or Pfizer/BioNtech BNT162b2 (n = 20) vaccines C and 1D.There was a major reduction in neutralization titre for all Omicron viruses for both vaccines. For AZD1222 vaccinees, BA.1.1 and BA.2 showed small but significant reductions in titers relative to BA.1; BA.1 vs. BA.1.1, 1.5-fold reduction (p = 0.0005) and BA.1 vs. BA.2 1.4-fold reduction (p = 0.0202). BNT162b2, following the third vaccine dose, showed the same trend; BA.1 vs. BA.1.1, 1.5-fold reduction (p = 0.0049) and BA.1 vs. BA.2, 1.2-fold reduction (p = 0.0637) C and 1D.Next, we looked at the neutralization profile across all VoC for serum collected from cases infected with BA.1. Early samples (n = 12) were taken ≤14 days from symptom onset (median 13 days); later samples (n = 16) were taken ≥21 days following symptom onset (median 38 days). All cases had received at least 2 doses of vaccine , and 3 of the late convalescent cases received a third dose of vaccine following Omicron infection. Neutralization was tested using live virus assays E. At earWe generated a panel of human monoclonal antibodies from volunteers who had recovered from sequence confirmed BA.1 infection having previously received 2 doses of the Pfizer-BioNtech vaccine. First, we performed neutralization assays against BA.1 and Victoria. In all cases, the BA.1 neutralization titre, measured by the serum dilution required to reduce virus foci by 50% (FRNT50), was above 100 B.B cells from 5 donors were stained with full-length BA.1 S trimer and single cells sorted by FACS C. FollowAlmost all mAbs cross-reacted between WT and BA.1 S by ELISA A. ComparNeutralization assays were used to select the 28 most potent antibodies, with BA.1 FRNT50 titers <100 ng/mL. All but one of these bound the RBD (Omi-41 bound the NTD), but none cross-reacted with SARS-CoV-1 S protein by ELISA. With the exception of Omi-30 and Omi-41, they reduce the interaction of RBD with ACE2 C. HoweveExamination of the heavy chain gene family usage  revealedRoughly one-half of the gene families we observed in the potent early pandemic antibodies are also represented in the Omicron set D. AlthouWe found higher levels of somatic mutation in both heavy and light chains of Omicron mAbs than in the early pandemic set of antibodies; mean number of amino acid substitutions 9.00/6.00 for Omicron and 4.55/4.25 for early pandemic (p < 0.0001 and p = 0.0026) for heavy and light chains, respectively E.The potency of these antibodies is underscored by SPR measurements of the binding of 6 selected mAbs to BA.1 RBD. The antibodies bind very tightly with affinities between 5 nM and 120 pM A–S2O.FigLive virus neutralization assays show that FRNT50 titers to Victoria are <100 ng/mL for all 28 potent mAbs A, perhapLive virus neutralization assays against Alpha, Beta, Gamma, and Delta VoC show 17/28 antibodies are cross-reactive against all VoC with <10-fold difference in FRNT50 titers between all viruses A. Omi-6,Finally, of 129 anti-NTD mAbs isolated, only one, Omi-41, showed FRNT50 titers <100 ng/mL. Omi-41 showed neutralizing activity against Victoria, Alpha, and Gamma but no activity against Beta and Delta, presumably reflecting the unique spectrum of NTD changes found in these viruses.For all 28 potent Omicron antibodies, neutralization assays of BA.1, BA.1.1, and BA.2 were performed using live virus A. Most sPseudoviral neutralization curves for panels of antibodies isolated from early pandemic and Beta cases against BA.1, BA.1.1, and BA.2 are shown in Neutralization assays against Victoria, BA.1, BA.1.1, and BA.2 for clinical mAbs revealed a number of differences A.REGN 10987 and 10933: REGN 10933 , but activity against BA.1 is markedly reduced, and neutralization of BA.1.1 is knocked out. This is due to the LC CDR2 contacting G446S in BA.1 and the R346K (BA.1.1) mutation making strong interactions with the HC CDR3. AZD8895 shows reduced neutralization due to the H2 contacts with the Q493R mutation universally present in the Omicron lineage ( lineage C.LY-CoV016 and 555: Activity of both antibodies on the entire Omicron lineage is knocked out. LY-CoV016 (IGHV3-53) makes extensive interactions with N501 and Y505 via L1 and L3, making it sensitive to mutations at these residues. LY-CoV555  attack the RBD from the front and sit above the binding site of Vir-S309. Changes, especially in the H3 loops, explain their differing specificities . Omi-6 aDetectable residual activity for mAb 150 (IGHV3-53) was observed with BA.1, BA.1.1, and BA.2 B. StructIn a set of potent early pandemic antibodies, the IGHV1-58 gene family was the second most highly represented (4/20) ; howeverWe determined the structure of BA.2 RBD in complex with ACE2 . As expeD = 4.0 nM), although affinities are similar among the three Spikes. The RBD binding probably gives the best indication of the intrinsic ACE2 affinity, and as reported earlier . All the potent mAbs generated cross-neutralize Victoria, and many are broadly reactive against VoC. These responses may be recalled from memory B cells generated following vaccination, but since we do not have paired samples to analyze repertoire following vaccination before Omicron infection, this remains conjecture. It is noteworthy that vaccination, and in particular third dose vaccination, has been shown to induce a broader antibody response to VoC .Following three doses of vaccine, particularly BNT162b2, good neutralizing titres of antibody against BA.1, BA.1.1, and BA.2 are induced, with only minor differences between them. Breakthrough Omicron infection in previously vaccinated individuals leads to an antibody response broadly effective against all VoC, including Omicron lineages. The similarity in neutralization titres suggests that reinfection of BA.1 exposed and vaccinated cases with BA.2 would be unlikely, at least in the short term; however, the concurrent high levels of infection by BA.1 and BA.2 have led to the identification of a BA.1/BA.2 recombinant virus XE , form the most frequent public antibody response in the Omicron set and in the response to early pandemic virus . Most eaThe second most abundant IGHV family amongst the Omicron antibodies (6/27) was IGHV1-69, which also featured in a panel of potent mAbs isolated from Beta-infected cases . We findWhilst the neutralization properties of most Omicron monoclonal antibodies isolated in this study did not show differences against BA.1, BA.1.1 and BA.2, some clinical mAbs showed differences, in particular REGN10987 regained some activity against BA.2 and AZD1061 regained most activity against BA.2 but lost activity against BA.1.1 compared to BA.1. Of particular concern S309, the activity of which is already reduced 6-fold against BA.1 , was redIn summary, we have presented a structure-function analysis of potent human antibodies induced by Omicron BA.1 breakthrough infection in SARS-CoV-2 vaccinated individuals. Many show broad activity against all VoC and may have been generated from vaccine memory responses. Overall, the structural studies demonstrate there is still space available on the RBD for the binding of potent mAbs able to broadly neutralize variants of concern. It also illustrates the extraordinary plasticity of the public antibody responses through IGHV3-53/66 and IGHV1-58 where neutralizing activity against BA.1 and other VoC can be restored by variation in CDR length and somatic mutation.in vitro, they are not affected by antibody-dependent cellular cytotoxicity or complement-dependent cytotoxicity, which may augment the function of poorly neutralizing antibody in vivo. Furthermore, we have not studied the effects of the T cell response, which is known to withstand changes in the VoC more robustly than the antibody response and to persist, which may contribute to the protection from severe disease if the antibody response fails to block infection.Some limitations of this study are that as the neutralization assays are performed dave@strubi.ox.ac.uk).Resources, reagents and further information requirement should be forwarded to and will be responded by the lead contact, David I. Stuart  from an upper respiratory tract (nose/throat) swab tested in accredited laboratories and lineage sequence confirmed through national reference laboratories. A blood sample was taken following consent at least 14 days after PCR test confirmation. Clinical information including severity of disease  and times between symptom onset and sampling and age of participant was captured for all individuals at the time of sampling.SARS-CoV-2/human/AUS/VIC01/2020, Alpha aVirus containing supernatant were harvested at 80% CPE and spun at 3000 rpm at 4°C before storage at −80°C. Viral titers were determined by a focus-forming assay on Vero cells. Victoria passage 5, Alpha passage 2 and Beta passage 4 stocks Gamma passage 1, Delta passage 3, BA.1 passage 2, BA.1.1 passage 2, and BA.2 passage 2 were sequenced to verify that they contained the expected spike protein sequence and no changes to the furin cleavage sites.2. To express Wuhan RBD, beta-RBD and ACE2, HEK293T cells were cultured in DMEM high glucose (Sigma) supplemented with 2% FBS, 1% 100X Mem Neaa and 1% 100X L-Glutamine at 37°C for transfection. Spike and Human mAbs were also expressed in HEK293T (ATCC CRL-11268) cells cultured in FreeStyle 293 Expression Medium  at 37°C with 5% CO2. BA.1 and BA.2 RBDs were expressed in Expi293F™ Cells (ThermoFisher), cultured in FreeStyle™ 293 Expression Medium (ThermoFisher) at 30°C with 8% CO2. E.coli DH5α and Turbo Competent E. coli (NEB) bacteria were used for transformation and large-scale preparation of plasmids. Single colonies were picked and cultured in LB broth at 37°C at 200 rpm in a shaker overnight.Vero (ATCC CCL-81) and VeroE6/TMPRSS2 cells were cultured at 37°C in Dulbecco’s Modified Eagle medium (DMEM) high glucose (Sigma-Aldrich) supplemented with 10% fetal bovine serum (FBS), 2 mM GlutaMAX  and 100 U/mL of penicillin–streptomycin. HEK293T (ATCC CRL-11268) cells were passaged in DMEM high glucose (Sigma-Aldrich) supplemented with 10% FBS, 1% 100X Mem Neaa (Gibco) and 1% 100X L-Glutamine (Gibco) at 37°C with 5% COPfizer vaccine serum was obtained from volunteers who had received either one or two doses of the BNT162b2 vaccine. Vaccinees were Health Care Workers, based at Oxford University Hospitals NHS Foundation Trust, not known to have prior infection with SARS-CoV-2 and were enrolled in the OPTIC Study as part of the Oxford Translational Gastrointestinal Unit GI Biobank Study 16/YH/0247 [research ethics committee (REC) at Yorkshire & The Humber – Sheffield] which has been amended for this purpose on 8 June 2020. The study was conducted according to the principles of the Declaration of Helsinki (2008) and the International Conference on Harmonization (ICH) Good Clinical Practice (GCP) guidelines. Written informed consent was obtained for all participants enrolled in the study. Participants were studied after receiving two doses of, and were sampled approximately 28 days (range 25–38), after receiving two doses of Pfizer/BioNtech BNT162b2 mRNA Vaccine, 30 micrograms, administered intramuscularly after dilution (0.3 mL each), 17–28 days apart, then approximately 28 days (range 25–56) after receiving a third “booster dose of BNT162B2 vaccine. The mean age of vaccinees was 37 years (range 22–66), 21 male and 35 female.33220855/PMID: 32702298). These studies were registered at ISRCTN (15281137 and 89951424) and ClinicalTrials.gov (NCT04324606 and NCT04400838). Written informed consent was obtained from all participants, and the trial is being done in accordance with the principles of the Declaration of Helsinki and Good Clinical Practice. The studies were sponsored by the University of Oxford  and approval obtained from a national ethics committee  and a regulatory agency in the United Kingdom . An independent DSMB reviewed all interim safety reports. A copy of the protocols was included in previous publications , were previously published  or half dose as their first dose (low dose) and a standard dose as their second dose (LD/SD cohort n = 4). The interval between first and second dose was in the range of 8–14 weeks. Blood samples were collected and serum separated on the day of vaccination and on pre-specified days after vaccination e.g. 14 and 28 days after boost.Data from vaccinated volunteers who received two or three doses: Vaccine doses were either 5 × 10+, IgG+, CD3−, CD14−, CD56−, CD16−, IgM-, IgA- and IgD-, and S+ was further selected and single cells were sorted into 96-well PCR plates with 10 μL of catching buffer . Plates were briefly centrifuged at 2000ⅹg for 1 min and left on dry ice before being stored at −80°C.Omicron S-specific single B cell sorting was performed as previously described . BrieflyOmicron S-specific human mAbs were cloned and expressed as described previously . BrieflyMAXISORP immunoplates were coated with 5 μg/mL of purified ACE2-His protein overnight at 4°C and then blocked by 2% BSA in PBS. Meanwhile, mAbs were serially diluted and mixed with 2.5 μg/mL of recombinant BA.1 trimeric S-twin-Strep. Antibody-S protein mixtures were incubated at 37 °C for 1 h. After incubation, the mixtures were transferred into the ACE2-coated plates and incubated for 1 h at 37°C. After wash, StrepMAB-Classic  was diluted at 0.2 μg/mL by 2% BSA and used as primary antibody followed by Goat anti-mouse IgG-AP  at 1:2000 dilution. The reaction was developed by adding PNPP substrate and stopped with NaOH. The absorbance was measured at 405nm. The ACE2/S binding inhibition was calculated by comparing to the antibody-free control well. IC50 was determined using the Probit program from the SPSS package.50 was determined using the probit program from the SPSS package.The neutralization potential of Ab was measured using a Focus Reduction Neutralization Test (FRNT), where the reduction in the number of the infected foci is compared to a negative control well without antibody. Briefly, serially diluted Ab or plasma was mixed with SARS-CoV-2 strains and incubated for 1 h at 37°C. The mixtures were then transferred to 96-well, cell culture-treated, flat-bottom microplates containing confluent Vero cell monolayers in duplicate and incubated for a further 2 h followed by the addition of 1.5% semi-solid carboxymethyl cellulose (CMC) overlay medium to each well to limit virus diffusion. A focus forming assay was then performed by staining Vero cells with human anti-NP mAb (mAb206) followed by peroxidase-conjugated goat anti-human IgG . Finally, the foci (infected cells) approximately 100 per well in the absence of antibodies, were visualized by adding TrueBlue Peroxidase Substrate. Virus-infected cell foci were counted on the classic AID EliSpot reader using AID ELISpot software. The percentage of focus reduction was calculated and ICPseudotyped lentivirus expressing SARS-CoV-2 S proteins were constructed as described before ; 2021b, To construct BA.1.1, mutagenic primers of R346K (R346K_F 5′-GTGTTCAATGCCACCAAATTCGCCAGCGTGTAC-3′ and R346K_R 5′-GTACACGCTGGCGAATTTGGTGGCATTGAACAC-3′) were PCR amplified by using BA.1 construct as a template, together with two primers of pcDNA3.1 vector (pcDNA3.1_BamHI_F 5′-GGATCCATGTTCCTGCTGACCACCAAGAG-3′ and pcDNA3.1_Tag_S_EcoRI_R 5′-GAATTCTCACTTCTCGAACTGAGGGTGGC-3′). Amplified DNA fragments were purified by using QIAquick Gel Extraction Kit (QIAGEN) and joined with pcDNA3.1 vector followed by Gibson assembly. All constructs were verified by Sanger sequencing after plasmid isolation using QIAGEN Miniprep kit (QIAGEN).4 cells/well. At 48 h post transduction, culture supernatants were removed and 50 μL of 1:2 Bright-GloTM Luciferase assay system  in 1x PBS was added to each well. The reaction was incubated at room temperature for 5 min and the firefly luciferase activity was measured using CLARIOstar® . The percentage of neutralization was calculated relative to the control. Probit analysis was used to estimate the value of dilution that inhibits half of the maximum pseudotyped lentivirus infection (PVNT50).The details of pseudoviral neutralization test were described previously , 2021b wTo determine the neutralizing activity of convalescent plasma/serum samples or vaccine sera, 3-fold serial dilutions of samples were incubated with the pseudoviral particles for 1 h and the same strategy as mAb was applied.Monoclonal antibodies isolated from patients during the early pandemic, Beta patients and Omicron patients along with a panel of neutralization titers against Victoria, Alpha, Beta, Gamma, Delta and Omicron-BA.1 pseudoviruses were clustered using cluster4x . NeutralAntigenic mapping was carried out as previously described . In shorDpnI treatment  and the reaction mixture was electroporated into E.coli Cloni® 10G cells . The correctness of mutagenesis was verified by sequencing.Cloning was done by using a restriction-free approach . MutagenExpression plasmids encoding Omicron spikes were constructed with human codon-optimized sequences from BA.1 (EPI_ISL_6640917) and BA.2 (EPI_ISL_6795834.2). The constructs of Wild-type and BA.1 Spike plasmids are the same as previously described . The genProtein expression and purification were conducted largely as described previously . Twin-stHeavy and light chains of the indicated antibodies were transiently transfected into 293T cells. To purify full length IgG mAbs, supernatants of mAb expression were collected and filtered by a vacuum filter system and loaded on protein A/G beads overnight at 4°C. Beads were washed with PBS three times and 0.1 M glycine pH 2.7 was used to elute IgG. The eluate was neutralized with Tris-HCl pH 8 buffer to make the final pH = 7. The IgG concentration was determined by spectrophotometry and buffered exchanged into PBS.Small amounts of Fab fragments were digested from purified IgGs with papain using a Pierce Fab Preparation Kit (Thermo Fisher), following the manufacturer’s protocol. AstraZeneca and Regeneron antibodies were provided by AstraZeneca, Vir, Lilly and Adagio antibodies were provided by Adagio.To express and purify large amount of Fabs, heavy chain and light chain expression plasmids of each Fab were co-transfected into HEK293T cells by PEI. Cells were cultured for 5 days at 37 °C with 5% CO2, culture supernatant was harvested and filtered using a 0.22 mm polyethersulfone filter. Twin-strep tagged Fabs were purified using Strep-Tactin XT resin (IBA lifesciences). IgG Omi-18, Omi-31 and Omi-42 were transiently expressed in Expi293F™ Cells (ThermoFisher), cultured in FreeStyle™ 293 Expression Medium (ThermoFisher) at 30°C with 8% CO2 for 5 days. Purification was performed in the same way as other IgGs.E. coli strain and protein expression induced by 1 mM IPTG grown overnight at 28°C. Periplasmic extract was prepared by osmotic shock, and the nanobody protein was purified with a 5 mL HisTrap nickel column (Cytiva), followed by size exclusion with a Hiload 16/60 Superdex 75 column.The gene for nanobody C1 (NbC1) and F2 (NbF2) and were codon-optimized using the IDT Codon Optimization Tool, synthesized as a ready-to-clone gene fragment (Integrated DNA Technologies), and cloned into the phagemid vector pADL-23c. The nanobodies were produced as previously described . Briefly−1 using a single-cycle kinetics program. Running buffer was also injected using the same program for background subtraction. All data were fitted to a 1:1 binding model using Biacore T200 Evaluation Software 3.1. To determine the binding kinetics between the SARS-CoV-2 Spikes and ACE2, a Twin-Strep-tag® Capture Kit (IBA-Lifesciences) was used. Spike protein containing a twin-Strep-tag was immobilized onto the sample flow cell of the sensor chip. The reference flow cell was left blank. ACE2 was injected over the two flow cells at a range of five concentrations prepared by serial twofold dilutions, at a flow rate of 30 μL min−1 using a single-cycle kinetics program. Running buffer was also injected using the same program for background subtraction. All data were fitted to a 1:1 binding model using Biacore T200 Evaluation Software 3.1.The surface plasmon resonance experiments were performed using a Biacore T200 . All assays were performed with a running buffer of HBS-EP (Cytiva) at 25°C. To determine the binding kinetics between the SARS-CoV-2 RBDs and ACE2 / monoclonal antibody (mAb), a Protein A sensor chip (Cytiva) was used. ACE2-Fc or mAb was immobilized onto the sample flow cell of the sensor chip. The reference flow cell was left blank. RBD was injected over the two flow cells at a range of five concentrations prepared by serial twofold dilutions, at a flow rate of 30 μL minCompetition assays of anti-Omicron BA.1 RBD mAbs were performed on an Octet Red 96e machine (Sartorius) using Octet Anti-HIS (HIS2) Biosensors (Sartorius). His-tagged Omicron BA.2 RBD dissolved in the running buffer  was used as the ligand and was first immobilized onto the biosensors. The biosensors were then washed with the running buffer to remove unbound RBD. Each biosensor was dipped into different saturating mAbs (Ab1) to saturate the bound RBD, except one biosensor was dipped into running buffer in this step, acting as the reference. Then all biosensors were washed with the running buffer again and dipped into wells containing the same competing antibody (Ab2). The y axis values of signals of different saturating antibodies in this step were divided by the value of the reference channel to get ratio results of different Ab1-Ab2 pairs. Ratio results close to 0 indicated total competition while 1 indicated no competition.RBD proteins were deglycosylated with Endoglycosidase F1 before used for crystallization. Initial screening of crystals was set up in Crystalquick 96-well X plates (Greiner Bio-One) with a Cartesian Robot using the nanoliter sitting-drop vapor-diffusion method, with 100 nL of protein plus 100 nL of reservoir in each drop, as previously described .-1. Omicron BA.1-RBD was mixed with Omi-3 and EY6A Fabs, Omi-6 and COVOX-150 Fabs, Omi-9 Fab and Nanobody F2 (NbF2), and Omi-12 and beta-54 Fabs separately, in a 1:1:1 molar ratio, with a final concentration of 7 mg mL-1. Omicron BA.1-RBD was mixed with Omi-32 Fab and NbC1 in a 1:1:1 molar ratio, with a final concentration of 11 mg/mL. Omi18 Fab, Omi31 Fab and NbC1 were mixed with Omicron BA.1-RBD and beta-RBD separately, in a 1:1:1:1 molar ratio, with a final concentration of 7 mg mL-1.These complexes were separately incubated at room temperature for 30 min. Omi-42 Fab was also crystallized.For crystallization, Omicron BA.1-RBD was mixed with Omi-25 Fab, and Omicron BA.2-RBD was mixed with COVOX-150 and ACE2 separately, in a 1:1 molar ratio, with a final concentration of 13 mg mL1 were obtained from Hampton Research PEGRx condition 1–19, containing 0.1 M Sodium acetate trihydrate pH 4.5 and 30% (w/v) PEG 1500. Crystals of BA.2-RBD/ACE2 were formed in Hampton Research PEGRx condition 1–23, containing 0.1 M MES monohydrate pH 6.0 and 20% (w/v) PEG monomethyl ether 2000 and further optimized in 0.09 M MES monohydrate pH 6.0 and 18% (w/v) PEG monomethyl ether 2000. Crystals of BA.1-RBD/Omi-3/EY6A were formed in Hampton Research PEGRx condition 1–25, containing 0.1 M sodium citrate tribasic dihydrate pH 5.0 and 30% (v/v) Jeffamine® ED-2001 pH 7.0. Crystals of BA.1-RBD/Omi-6/COVOX-150 were obtained from Molecular Dimensions Proplex 1–23, containing 0.1 M Sodium HEPES pH 7.0 and 15% (w/v) PEG 4000. Crystals of BA.1-RBD/Omi-9/NbF2 were obtained from Hampton Research PEGRx condition 1–19, containing 0.1 M Sodium acetate trihydrate pH 4.5 and 30% (w/v) PEG 1500. Crystals of BA.1-RBD/Omi-12/beta-54 were formed in Hampton Research PEGRx condition 1–46, containing 0.1 M Sodium citrate tribasic dihydrate pH 5.0 and 18% (w/v) PEG 20000. Complex of BA.1-RBD/Omi-12/beta-54 was screen in Hampton Research Ammonium sulfate screen C2, containing 2.4 M (NH4)2SO4 and 0.1 M citric acid pH 5.0, but only crystals of Fab Omi-12 alone were formed in this condition. Crystals of BA.1-RBD/Omi-32/NbC1 were formed in Hampton Research PEGRx condition 2–35, containing 0.15 M Lithium sulfate monohydrate, 0.1 M Citric acid pH 3.5 and 18% (w/v) PEG 6000. Crystals of BA.1-RBD/Omi18/Omi31/NbC1 were formed in Molecular Dimensions Proplex condition 2–12, containing 0.2 M Ammonium sulfate, 0.1 M MES pH 6.5 and 20 % (w/v) PEG 8000. Crystals of beta-RBD/Omi18/Omi31/NbC1 were formed in Molecular Dimensions JCSG plus condition 1–48, containing 0.04 M Potassium phosphate monobasic and 16% (w/v) PEG 8000. Crystals of Omi-42 Fab alone were formed in Hampton Research PEGRx condition 1–24, containing 0.1 M Tris pH 8.0 and 30% (w/v) PEG monomethyl ether 2000.Crystals of BA.1-RBD/Omi-25 were obtained from Molecular Dimensions Proplex condition 1–31, containing 3.0 M Sodium formate and 0.1 M Tris pH 7.5. BA.2-RBD/COVOX-150 crystals were obtained in 2 different space groups. Crystals of space group C2 were formed in Hampton Research PEGRx condition 1–29, containing 0.1 M Sodium citrate tribasic dihydrate pH 5.5 and 18% (w/v) PEG 3350. Crystals of space group P2https://www.diamond.ac.uk/Instruments/Mx/I03/I03-Manual/Unattended-Data-Collections.html). Crystals were pre-frozen by mounting in loops and soaked for a second in cryo-protectant containing 25% glycerol and 75% mother liquor. Diffraction images of 0.1° rotation were recorded on an Eiger2 XE 16M detector . Data were indexed, integrated and scaled with the automated data processing program Xia2-dials  was prepared, aspirated and almost immediately applied to a freshly glow-discharged C-flat 200 mesh 2/1 grids at high intensity, 20 s, Plasma Cleaner PDC-002-CE, Harrick Plasma. Excess liquid was removed by blotting for 5 s with a force of −1 using vitrobot filter paper  at 4.5°C, 100 % reported humidity before plunge freezing into liquid ethane using a Vitrobot Mark IV (Thermo Fisher). Fab/Spike complexes were incubated for 5–10 minutes prior to application to grids and plunge freezing.Movies were collected in mrc format using EPU on a 200 kV Glacios microscope equipped with a Falcon-III detector in linear mode, a 50 μm aperture, and 100 μm objective were employed. A total of 3269 movies were recorded with a total dose of 45 e/Å2 and a pixel size 1.2 Å/pix with fringe free illumination.2 was applied to each movie and defocus range of 0.8–2.6 μm.Compressed tiff movies, 8084 and 5638 respectively, each with 40 frames, were acquired on a Titan Krios (Thermo Fisher) operating at 300 kV with a K3 detector and 20 eV slit (Gatan) at a nominal magnification of 105 kX in super resolution mode . A total dose of 50.5 e/ÅFor all three datasets, movies were 4-times binned and motion and ctf corrected on the fly using the cryoSPARC v3.3.1 live framework . Particlmabscape  were used in a competition assay prepared for antibody mapping to the RBD surface. Antibody mapping was carried out using mabscape  and clusmabscape . Mid-poi50 (FRNT50) was determined using the probit program from the SPSS package. The Wilcoxon matched-pairs signed rank test was used for the analysis and two-tailed P values were calculated on geometric mean values.Statistical analyses are reported in the results and figure legends. Neutralization was measured by FRNT. The percentage of focus reduction was calculated and IC


IL36RN, which encodes interleukin-36 receptor antagonist (IL-36Ra), have been implicated in the pathogenesis of skin disorders. We previously reported that Il36rn−/− mice exhibit an enhanced contact hypersensitivity (CHS) response through increased neutrophil recruitment. In addition, Il36rn−/− mice show severe imiquimod-induced psoriatic skin lesions and enhanced neutrophil extracellular trap (NET) formation. We hypothesized that NETs may play an important role in the CHS response. To confirm this, we examined the CHS response and NET formation in Il36rn−/− mice. Il36rn−/− mice showed enhanced CHS responses, increased infiltration of inflammatory cells, including neutrophils, CD4+ T cells, and CD8+ T cells, NET formation, and enhanced mRNA expression of cytokines and chemokines, including IL-1β, C-X-C motif chemokine ligand (CXCL)1, CXCL2, and IL-36γ. Furthermore, NET formation blockade improved the CHS response, which consequently decreased inflammatory cell infiltration and NET formation. Consistently, we observed decreased expression of these cytokines and chemokines. These findings indicate that IL-36Ra deficiency aggravates the CHS response caused by excessive inflammatory cell recruitment, NET formation, and cytokine and chemokine production, and that NET formation blockade alleviates the CHS response. Thus, NET formation may play a prominent role in the CHS response.Loss-of-function homozygous or compound heterozygous mutations in  IL36RN encodes interleukin (IL)-36 receptor antagonist (IL-36Ra), a protein of the IL-1 cytokine family, which closely regulates IL-36 signaling2. In the IL-36 pathway, IL-36α, β, and γ are utilized as specific receptors2. The IL-36 pathway is activated when IL-36α, β, and γ bind to their specific receptor, interleukin-1 receptor-related protein 2 (IL-1Rrp2), thereby inducing the recruitment of the co-receptor IL-1 receptor accessory protein (IL-1RacP) and activation of the nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase signaling pathways2. This stimulates the transcription and secretion of pro-inflammatory cytokines2 and leads to the recruitment of neutrophils, T cells, and dendritic cells (DCs) to the dermis. IL-36 stimulates the production of chemotactic substances by activating leukocytes and promoting leukocyte infiltration and skin acanthosis3.IL36RN gene have been implicated in psoriasis-related pustular eruptions, such as generalized pustular psoriasis, acrodermatitis continua of Hallopeau, acute generalized exanthematous pustular eruptions, and palmoplantar pustular psoriasis4. Loss-of-function mutations in IL36RN cause “deficiency of interleukin-36 receptor antagonist”, a recessively inherited autoinflammatory keratinization disease12. According to information from the Human Genetic Variation Database, two IL36RN founder mutations (c.28 C > T (p. Arg10X) and c.115 + 6 T > C (p. ArgfsX1)) have been detected in less than 2% of the Japanese population13. Consequently, a few Japanese individuals carry IL36RN mutations, which may have etiological roles in several diseases, including generalized pustular psoriasis.Homozygous or compound heterozygous mutations in the Il36rn−/− mice12 and reported that contact hypersensitivity (CHS) responses are enhanced owing to the increase in neutrophil mobilization with the increase in the generation of CD4+ T and CD8+ T cells14. Furthermore, we previously found that imiquimod-induced psoriatic skin lesions were more severe and that neutrophil extracellular trap (NET) formation was enhanced in Il36rn−/− mice15. However, the immunological pathophysiology of NETs in CHS remains unclear. We hypothesized that NETs play a prominent role in the CHS response in the presence of a high number of CD4+ T cells and CD8+ T cells. To confirm this possibility, we evaluated NET formation qualitatively or quantitatively in Il36rn−/− and wild-type mice under the influence of CD4+ and CD8+ T cells in the CHS response.We previously generated Il36rn−/− and wild-type mice  and 48 h   **p < 0.01, 23.32% decrease (48 h) **p < 0.01; wild-type mice; 54.56% decrease (24 h) **p < 0.01, 20% decrease (48 h) **p < 0.01) . Interestingly, the number of MPO-positive neutrophils significantly decreased upon Cl-amidine treatment in both Il36rn−/− (**p < 0.01) and wild-type mice (**p < 0.01) . The number of F4/80-positive macrophages, CD4+ T cells, and CD8+ T cells decreased upon Cl-amidine treatment in both Il36rn−/− mice  and wild-type mice   Fig. a,b. Simill) Fig. a,b. ThusIl36rn−/− mice at 48 h after the challenge increased significantly in comparison with that in wild-type mice   vs. 173.2 ± 16.63 (Cl-amidine), **p < 0.01) and wild-type mice (139.5 ± 15.55 (vehicle) vs. 71.80 ± 6.675 (Cl-amidine), **p < 0.01) , C-X-C motif chemokine ligand (CXCL) 1, CXCL2, and IL-36γ in the ear tissue samples of Il36rn−/− mice were significantly higher than those in the ear tissue samples of wild-type mice , IL-4, IL-6, IL-10, or IL-36β compared to that in wild-type mice, as previously reported14. In addition, in Il36rn−/− mice, the mRNA expression levels of IL-1β, IFN-γ, IL-4, IL-6, IL-10, IL-17A, TNF-α, CXCL1, CXCL2, and IL-36γ decreased significantly in response to Cl-amidine treatment  to assess how Cl-amidine treatment inhibited the CHS response and inflammation. In agreement with findings from previous reportsIl36rn−/− mice , Th17/Tc17 cytokines (including IL-17A and TNF-α), and IL-36γ  produce IFN-γ17, which acts on keratinocytes to generate Th1 cytokines and lead to the infiltration of inflammatory cells into the skin during the effector phase17. As NET formation was confirmed in this study, NETs may contribute to the CHS response. NETs have been reported to promote macrophage pyroptosis and macrophage-derived IL-1β production20. In addition, reportedly, macrophages secrete IL-3621. Furthermore, in an in vitro experiment, IL-36γ induced CXCL1 production via the activation of keratinocytes and promoted the migration of neutrophils, αβT cells, and γδT cells22. Therefore, enhanced NET formation in Il36rn−/− mice may promote macrophage recruitment and increase IL-1β and IL-36γ production. IL-1β may induce the production of IL-17A in γδ T cells and contribute to the production of neutrophils. In addition, IL-36γ stimulation may induce keratinocyte proliferation, and CXCL1 generated by keratinocytes may induce the migration of neutrophils, CD4+ T cells, CD8+ T cells, and γδ T cells, leading to a subsequent increase in neutrophil and NET production.The number of macrophages, CD46γ Figs. . It is kIl36rn−/− and wild-type mice . The fact that, in our study, IL-10 levels differed in the ear tissue but not in the plasma was presumably because CHS is a localized inflammation and the inflammation was not high enough to affect plasma IL-10 levels.This study has a limitation that could be addressed in future studies. Since all samples in this experiment were obtained after elicitation, the pathophysiology was observed only during the elicitation phase. However, the reaction process of contact dermatitis can be roughly divided into the sensitization and elicitation phases. Therefore, to determine the effect of NETs on the pathophysiology of contact dermatitis during sensitization, it is necessary to examine the percentage of naïve, activated, and memory T cells in regional lymph nodes and tissues after sensitization. Additional experiments using flow cytometry should be conducted in the future. In a sepsis model, mice treated with Cl-amidine were reported to have higher IL-10 levels in the plasma than in mice not treated with Cl-amidine+ T cells, CD8+ T cells29, and neutrophils31 have been implicated in the immune reactions in contact dermatitis, NETs may also exacerbate immune reactions in CHS. Therefore, the inhibition of NET formation may be a new therapeutic strategy in contact dermatitis.In conclusion, the results of our study suggest that although CD4Il36rn−/− mice were generated on a C57BL/6NCr1 background, as previously reported32, and the genotype was confirmed by allele-specific PCR. Wild-type mice (C57BL/6NCr1) were obtained from Charles River Laboratories . Gender-matched female mice, aged 8 to 12 weeks, were used in these experiments.The study was approved by the Regulations for the Management of Laboratory Animals at Fujita Health University, and all procedures were conducted in accordance with the guidelines of the Animal Care and Use Committee at Fujita Health University (APU19017). Our study with observational experimental design was carried out in compliance with the ARRIVE guidelines. We bred and housed the mice in a specific pathogen-free barrier facility. Il36rn−/− and wild-type mice and assigned them to Cl-amidine treatment and no treatment groups, respectively. Six mice were assigned to each group. We generated the CHS induction mouse model using DNFB , as previously reported33. On day 0, the mice were sensitized by applying 25 µL of 0.5% DNFB in acetone/olive oil (4:1) on the shaved dorsal surface and were then topically challenged with 15 µL of 0.2% DNFB in acetone/olive oil (4:1) on each side of both ears on day 5. To investigate the effect of Cl-amidine during the CHS response, Il36rn−/− and wild-type mice were intraperitoneally injected with 10 mg/kg Cl-amidine  or an equal volume of vehicle (dimethyl sulfoxide solution) on days 0–5. We measured the ear swelling using dial thickness gauges  before the challenge and after 24 and 48 h. Measurements for each ear were performed three times, and the average value was used for analysis. We collected ear tissue samples on day 7 for RT-PCR and histopathological analysis.We created the CHS induction mouse model in 2; magnification,  400×). Two investigators, who were blinded to the study, independently examined each section. The mean values of these measurements were utilized for analysis.We excised the ears of mice in each group 48 h after the DNFB challenge. The ear tissues were fixed in 4% paraformaldehyde and embedded in paraffin, and 6 µm sections were prepared. We stained the preparations with hematoxylin and eosin (H&E) and counted the number of MPO-positive neutrophils, F4/80-positive macrophages, CD4-positive T cells, and CD8-positive T cells in 10 high-power fields . The deparaffinized sections were treated with an endogenous peroxidase blocking solution  for 20 min at 27 °C. The sections were treated overnight with specific primary antibodies against F4/80 , CD3 , CD4 , and CD8  at 4 °C, followed by three washes with PBS. Secondary antibodies conjugated to biotin were then applied and incubated with an avidin–biotin complex (Vector Laboratories: VECTASTAIN Elite ABC Kit #PK-6101) for 30 min at 27 °C, followed by washing three times with PBS. Peroxidase activity was observed with the use of an ImmPACT DAB substrate kit (Vector Laboratories: #SK-4105). The slides were counterstained with hematoxylin. For the negative control, the sections were not treated with primary antibodies.15. The ear sections were deparaffinized in xylene, permeabilized with ethanol, rehydrated in PBS, and blocked with a blocking solution  for 30 min at 27 °C. Next, the sections were treated with specific primary antibodies against citrullinated histone H3  and MPO  for 2 h at 27 °C. After washing three times with PBS, the slides were treated with secondary antibodies (donkey anti-goat immunoglobulin G (IgG), Novus Biologicals, Littleton, CO, USA; Alexa Fluor 488, Thermo Fisher Scientific, Waltham, MA, USA; donkey anti-rabbit IgG, Novus Biologicals; and Alexa Fluor 647, Thermo Fisher Scientific) for 30 min at 27 °C. The sections were washed three times with PBS and then enclosed in a medium containing 4′,6-diamidino-2-phenylindole (Abcam). Confocal imaging was performed with the use of an Olympus Fluoview 1000 microscope . The NETs showed positive staining for both MPO and citrullinated histone H3. Relative NETs area was calculated as previously reported35. Briefly, we randomly selected five sections per mouse and then used the Image J software to add the pixels in the area of NETs in each section. Thereafter, we averaged the number of pixels per section per mouse. The average NETs area for the six mice in the no-treatment group of wild type mice was then taken as 1, and for the other groups, they were calculated as ratios. Two investigators independently examined each section in a blinded manner, and the mean values of the measurements were utilized for analysis.The skin of the ear samples was cut into 4 μm-thick sections, and immunofluorescence staining was performed to determine NET release utilizing antibodies against citrullinated-histone H3 and MPO, as published previouslyGAPDH; Mm.PT.39a.1) was utilized as an internal control. The relative mRNA expression levels of various target genes normalized to the expression level of GAPDH were calculated using the 2−∆∆Ct method. The primer sequences utilized for each gene were chosen by pre-validated PrimeTime qPCR assays .Total RNA was extracted from the ear tissue samples with Qiagen RNeasy spin columns . Total RNA was reverse-transcribed into cDNA with the use of the Prime Script RT Reagent Kit  in accordance with the manufacturer’s instructions. The expression levels of IL-1β (Mm.PT.58.41616450), IFN-γ (Mm.PT.58.41769240), IL-4 (Mm.PT.58.32703659), IL-6 (Mm.PT.58.10005566), IL-10 (Mm.PT.58.13531087), IL-17A (Mm.PT.58.6531092), TNF-α (Mm.PT.58.12575861), CXCL1 (Mm.PT.58.42076891), CXCL2 (Mm.PT.58.1045839), IL-36α (Mm.PT.58.12651602), IL-36β (Mm.PT.58.11528127), and IL-36γ (Mm.PT.58.30810984) were quantified by RT-PCR on a Light Cycler System . The PCR samples were dispensed in microcapillary tubes, with a reaction volume of 20 µL, containing 2.0 µL of the diluted cDNA solution, and the PCR program was conducted in accordance with the manufacturer’s instructions. Glyceraldehyde-3-phosphate dehydrogenase  and expressed in terms of mean ± SEM. The Mann–Whitney Supplementary Information.Supplementary Figure 1.