E7, a nematic liquid crystal (LC), is doped with 4‐pentyl‐4′‐biphenyl carboxylic acid (PBA) and encapsulated in polymeric microcapsules (P‐E7PBA), which are then immobilized on cells in a microfluidic channel. Normal human umbilical vein endothelial cells (HUVECs) and myeloma, human primary glioblastoma (U87), human colon carcinoma (Caco‐2), and human breast adenocarcinoma (MCF‐7) cells are investigated for the release of NH3. The P‐E7PBA is able to visualize NH3 release from the cell via a radial‐to‐bipolar (R‐B) orientation change, observed through a polarized optical microscope. The various cell lines significantly differ in their response time required for an R‐B change. The mean response times for Caco‐2, U87, and MCF‐7 cells are 277, 155, and 121 s, respectively. NH3 release from a single cell captured in a microwell flow chip shows a similar R‐B change. The P‐E7PBA droplets technology could be applied to other multiple targets by functionalizing LCs with different probes.Tumor cells exhibit prominent metabolic alterations through which they acclimatize to their stressful microenvironment. These cells have a high rate of glutaminolysis and release ammonia (NH 3)Ammonia (NH diffuses from the cell to the cellular microenvironment. With a dissociation constant (pKa) of 9.3, the NH3 + NH4+ content is 99% composed of NH4+ ions. The NH4+ ions interact with the COO−‐functionalized liquid‐crystals (LCs), which results in a radial‐to‐bipolar change of the LC droplet. The dashed lines in the droplets show the orientation of the LC molecules. Enzymes that function in the urea cycle synthesize NH3 in vitro. Glutamate dehydrogenase and glutaminase introduce NH3 into the urea cycle through the metabolism of l‐glutamate and l‐glutamine, respectively.3 in the cellular microenvironment. This condition may be due to the reliance of tumor cells on glycolysis for the production of energy, which reduces the requirement for mitochondrial phosphorylation. Due to metabolic reprogramming in cancer cells, mitochondria adopt a new anabolic role to fulfill the high biosynthetic need resulting from cellular proliferation. The mitochondria of tumor cells produce the intermediate α‐ketoglutarate (α‐KG) for the tricarboxylic acid (TCA) cycle.3 is released as a byproduct.3 readily diffuses across the cell membrane, following the chemical potential gradient. Thus, the real‐time imaging of NH3 release from cells to the cellular microenvironment could play a vital role in exploring the behavior and heterogeneity among tumor cells. However, analyzing metabolites released from cells to the surroundings is difficult due to rapid fluctuations and dilution to ultralow concentrations,Ammonia NH is a toxT = 18–60 °C).5 molecular length.The LCs are anisotropic liquid phases and can be best described as a liquid that possesses orientating molecular order.PBA)) and was then filled into polymeric microcapsules (P‐E7PBA). E7 was used rather than 5CB due to the need to facilitate a high nematic‐to‐isotropic transition. P‐E7PBA droplets were immobilized on cells that were cultured in a microfluidic channel. Live imaging of NH3 release from the cells/a single cell was performed through a radial‐to‐bipolar (R‐B) orientation change of P‐E7PBA under cross‐polarization  to prevent endocytosis, easy immobilization on cell membranes, selective detection of NH3 released from cells, high sensitivity, and easy detection through POM. Additionally, the polymer assembly acts as a semipermeable membraneIn this study, the LC E7 was doped with 4‐pentylbipenyl‐4ʹ‐carboxylic acid  functionality. In addition, PBA has a chemical structure resembling 5CB, which is a major component (51%) of E7 . FigurePBA in an aqueous medium under bright field and cross polarization, respectively. P‐E7PBA exhibited a radial configuration in aqueous medium. A similar radial configuration of P‐E7PBA was observed  plates, in addition to crossed‐polarization . Comparatively, the radial configuration of the P‐E7PBA under cross‐polarization without a λ‐plate was more visible than in the presence a λ‐plate. Therefore, all of the images of the P‐E7PBA configuration were captured under cross‐polarization only.Monodispersed polystyrene (PS)‐beads were obtained via dispersion polymerization of styrene, initiator, and stabilizer. The scanning electron microscopy (SEM) and optical microscopy images  show that the diameter of the PS beads was ≈2 µm. The PS beads were utilized as a template for the deposition of layer‐by‐layer assembly of polystyrene sulfonate (PSS) and polyallylamine (PAAm) . Subsequently, the PS beads were etched to obtain polymeric microcapsules, which were filled with E72.2PBA droplets was observed on human umbilical vein endothelial cells (HUVEC) and human primary glioblastoma cells (U87) at different P‐E7PBA concentrations. The cell viability was calculated by Equation FigurePBA), ≈99% of the cells were viable at a P‐E7PBA concentration of 0.25 mg mL−1. The viability decreased to 98% when the concentration was 0.5 mg mL−1. At high concentration (1 mg mL−1), the P‐E7PBA accumulated on the cell surface in such a way that the cells were not visible, yet 94% of the cells were viable, which suggested the cell compatibility of the P‐E7PBA droplets. Similarly, the cell viability was ≈99% in the negative control (naked E7PBA), which may be due to poor dispersion and nonattachment of the E7PBA on the cell membrane. We choose the P‐E7PBA concentration of 0.25 mg mL−1 for further experiments because the higher concentrations might have deteriorated the normal cellular activityThe cell compatibility of P‐E72.3PBA droplets was observed in MEM (without supplementation of FBS) at different pH values ranging from 6 to 8  and an acidic (pH = 6.5) solution . The R‐B change at acidic pH was attributed to the protonation of the PBA COO− to COOH. Doping LCs with molecules containing pH‐sensitive functional groups makes the LC orientation pH‐responsive.− pendent groups of PAA and caused the R‐B change of 5CB.PBA was due to PBA.The pH responsiveness of the P‐E78 Figureai–vi. ThPBA droplets for the imaging of NH3, the experimental conditions were optimized to equate the extracellular pH. A 0.5 µL aliquot of P‐E7PBA droplets in MEM was introduced onto HUVEC, human colon carcinoma (Caco‐2), U87, or human breast adenocarcinoma (MCF‐7) cells that were cultured in microfluidic channels. Each channel contained ≈800 cells. The radial orientation of the droplets was maintained in the HUVECs, while the R‐B change was observed in the channels containing Caco‐2, U87, and MCF‐7 cells , ascorbic acid (1 × 10−6m), or a mixture of acidic amino acids (1 × 10−6m). In each case an R‐B change was observed . P‐E7PBA was then introduced to the same concentration of these analytes in a mixed solution (1:1) of MEM and PBS (pH = 7.4). The radial configuration of P‐E7PBA was maintained, which indicated that PBS prevented the pH change due to these analytes. It was concluded that the P‐E7PBA R‐B change can be prevented via the protonation of acidic species in the cellular microenvironment under controlled experimental pH values. Furthermore, the impact of the mixture solution on the cell activity was evaluated. The U87 cells were separately cultured in MEM and MEM + PBS (1:1) for 3 h in a humid environment, with 95% air and 5% CO2 at 37 °C. Relative to the 100% cell viability in MEM, all cells were similarly viable in the mixture solution . Therefore, the mixture solution does not appear to disturb normal cellular behavior due to the short analysis time of this technique. Consequently, the imaging of NH3 released from the cells was performed in a MEM + PBS (1:1) mixture at pH = 7.4.The extracellular pH of normal cells ranges from 7.2 to 7.4, while that of cancerous cells ranges from 6.2 to 6.9.2.4PBA droplets for NH3 detection was analyzed in MEM + PBS (1:1) supplemented with aqueous ammonia at different concentrations (0.3× 10−6–1.5 × 10−6m) and pH = 7.4. The radial orientation was maintained until an NH3 concentration of 0.3 × 10−6m, while an R‐B change became visible at an NH3 concentration ≥ 1 × 10−6m . The P‐E7PBA was tested in an aqueous NH4Cl solution. A similar R‐B orientation change was observed. Furthermore, the P‐E7DTAB ) was subjected to aqueous NH3 and aqueous NH4Cl solutions. The radial orientation of the P‐E7DTAB was maintained , suggesting that PBA was responsible for the R‐B change in the presence of NH4+ ions. The kinetic transfiguration of P‐E7PBA could be an indication of the NH3 concentration in a medium. Figure S8a in the Supporting Information shows the R‐B change of P‐E7PBA as a function of time at different NH3 concentrations (1 × 10−6–2.5 × 10−6m). In the plot, an inferred value of 10% was assigned to the point of initiation of the R‐B change at different concentrations. The speed of the transfiguration was dependent on the amount of NH3. At a high NH3 concentration, there was a faster R‐B change in the biphenyl carboxylic, whereas at a low concentration, the change occurred slowly. This is quite significant because the P‐E7PBA can respond to the NH3 concentration not only in an on–off manner but also in a quantitative relationship that can be derived from the standard curve of NH3 concentration against time . The standard curve for the point of initiation of the R‐B change could be applied for the NH3 concentrations to those when the P‐E7PBA does not achieve a 100% R‐B change.The efficiency of P‐E7PBA for NH3 detection was evaluated in the presence of metal ions  and biomolecules  in MEM + PBS at pH = 7.4. The radial configuration of P‐E7PBA was maintained in 10 × 10−6m solutions of Na+, K+, glucose, glutamine, and FBS , while a slight radial‐to‐preradial configuration change was observed in the presence of Ca2+ and Fe2+. This change was attributed to the linkage of Ca2+ or Fe2+ with the COO‾ groups of two neighboring PBA molecules. The linkage may tilt the PBA molecules, resulting in a preradial configuration. Next, 0.7 × 10−6 or 1 × 10−6m NH3 was added to complex mixture solutions containing 2 × 10−6m each of Na+, K+, Ca2+, Fe2+, glucose, glutamine, and FBS. Similar to the pure NH3 solutions, a slight configuration change in the presence of the solution that contained 0.7 × 10−6m NH3 and a complete R‐B change was observed in the solution containing 1 × 10−6m NH3. The R‐B change in the presence of NH3 may be due to its lipophilic nature. Compared to the other cations, the NH4+ ion may easily accumulate on the surface of P‐E7PBA, and in addition to electrostatic interactions it forms hydrogen bonds between the neighboring PBA molecules.The selectivity of P‐E73 released from cells, P‐E7PBA droplets (0.25 mg mL−1) were immobilized on the cell membrane. Movies S1 and S2 in the Supporting Information show the P‐E7PBA droplets before and after immobilization on the cell membrane, respectively. The number of P‐E7PBA droplets per cell can be increased by increasing the concentration of the droplets. In the present experimental setup it was difficult to control the density of the P‐E7PBA droplets immobilized on a single cell. However, the use of droplet microfluidics or other experimental advancements may provide a solution to anchor a desired amount of droplets onto a single cell. The radial orientation was maintained on HUVECs, while over time a gradual R‐B change was observed in the P‐E7PBA droplets on Caco‐2, U87, and MCF‐7 cells  for the R‐B change was observed for Caco‐2, U87, and MCF‐7 cells, which followed the order of tpass = MCF7 < U87 < Caco‐2. During the R‐B change, a mixed radial and preradial‐like configuration appeared for Caco‐2 at tpass = 120 s. The R‐B change became more visible at tpass = 180 s. At tpass = 30 s the preradial configuration was observed in MCF‐7 cells but not in U87. A clear axial configuration was found for U87 at tpass = 120 s, while the axial state did not appear for Caco‐2 and MCF‐7 cells. The sequential orientation changes from radial, preradial, axial, to bipolar can be termed as the reverse‐sequence‐orientation change because the sequential change usually appears during the anchoring of the LC droplets as they change from bipolar to radial.PBA droplets was controlled by the net charge density; therefore, the lack of visible appearance of each configuration of P‐E7PBA droplets immobilized on the cell membrane may be due to the small size and high sensitivity of the droplets.For live imaging of NHplets 0.2 mg mL−1 Ka) of 9.3, NH4+ constitutes ≈99% of the total ammonia (NH3 + NH4+) concentration at a physiological pH (7.1–7.5). In its ionized form, NH4+ is relatively impermeable to cell membranes. At pH >6.8, P‐E7PBA exhibits a radial configuration, and rapid protonation of NH3 in the cellular microenvironment causes a constant flow of NH3 from the cells to the surroundings, which raises the pH of the cellular microenvironment. Under this condition, P‐E7PBA could remain deprotonated, as shown in Figure 4+ in the cellular microenvironment interacts with the opposite charge COO− of PBA. This reduces the net charge density and forms hydrogen bonding, leading to the R‐B orientation change of P‐E7PBA.With a dissociation constant (ppH 7.1–7.. In its 3 can be produced via the glutamate dehydrogenase (GLDH)‐catalyzed oxidation of l‐glutamate in the presence of nicotinamide dinucleotide (NAD+) cofactor in situ (SchemePBA droplets were tested in the presence of GLDH (10 × 10−6m), l‐glutamate (25 µg), and NAD+ (2 × 10−6m) in PBS at pH = 7.4. An R‐B change was observed, which was attributed to the presence of NH3 generated from the GLDH‐catalyzed reaction of l‐glutamate  for an R‐B change of the P‐E7PBA droplets. The tR‐B was noted from 10 channels each of Caco‐2, U87, and MCF‐7 cells , the U87, Caco‐2, and MCF‐7 cells released NH3 in the range of 0.92 × 10−6–1.2 × 10−6m, 1.54 × 10−6–2.05 × 10−6m, and 1.91 × 10−6–2.64 × 10−6m, respectively. These estimated concentrations may be higher than the actual amount of NH3 released from the cells. Furthermore, in comparison to normal cells, the tumor cells exhibited a higher rate of glutamine transport and metabolism.−6–4 × 10−6m l‐glutamine. To observe the activity of glutaminase in terms of NH3 production, MEM was supplemented with 25 or 50 × 10−6m glutamine  and NH3. Therefore, the cyclization of glutamine to PCA at high concentrations results in an increased extracellular NH3 concentration. The NH3, NH4+, and H+ remained at a dynamic equilibrium due to the rapid protonation and deprotonation of NH3.3 from the surroundings to the cytoplasm, which was visualized as slowness in the R‐B orientation change. The Berthelot reaction3 release from all cell lines in different conditions , which confirmed that the medium from both U87 and MCF‐7 cells contained less NH3 at 50 × 10−6m glutamine compared to normal medium and medium supplemented with 25 × 10−6m glutamine.The cellular heterogeneity among the cell lines was explored through the difference in time required . The MCF‐7 cells were cultured in a microwell flow chip. Some of the microwells contained a single cell, while most of the wells contained more than one cell. Optimizing several factors, including cell number (cells mL−1), can achieve individual cells per microwell. The NH3 release response of P‐E7PBA immobilized on MCF‐7 cells cultured in a microwell flow chip was observed. An R‐B orientation change of the P‐E7PBA droplets was observed in the microwells containing single MCF‐7 cells, while the radial orientation was maintained in neighboring wells that did not contain any cells  and myeloma  cells via an R‐B orientation change of the P‐E7PBA droplets under cross‐polarization. P‐E7PBA can easily be anchored on the cell membrane. NH3 that diffuses from the cell changes to NH4+ at physiological pH. The cationic NH4+ then interacts with the COO− of PBA, which reduces the net charge density at the LC/aqueous interface, resulting in an R‐B orientation change. The tR‐B of the R‐B orientation change was the direct indication of NH3 concentration release from the cell; this metric was used to differentiate between cell lines and explore cellular heterogeneity. In addition, the P‐E7PBA droplets have the advantages of a controllable size, easy immobilization on the cell membrane, cell compatibility, high sensitivity, and easy detection through POM. By engineering LC‐based probes, this approach can be extended to detect other molecules and ions in the cellular microenvironment and has potential applications in biomedical research.This study visualized the NH4PBASynthesis of Microcapsules and Encapsulation of E7: The uniform size PS microbeads were synthesized using a previously reported methodMn = 40 kDa, 0.4 g) was then added and stirred for 15 min, styrene (5 mL) was then slowly added to the reaction medium over the course of 5 min. Finally, 2,2‐azobisisobutyronitrile (20 mg) was introduced as a radical initiator, and the reaction was refluxed at 80 °C for 24 h with continued stirring. The PS bead suspension was cooled to room temperature and centrifuged at 7000 rpm for 5 min. The PS beads were washed twice with ethanol and dried to powder at room temperature.PSS and polyallylamine (PAAm) solutions (1 wt%) were prepared in ethanol:DIW (1:1). The PS beads (50 mg) were dispersed in PSS solution (20 mL) in a centrifuge tube and agitated for 12 h at room temperature to allow the adsorption of PSS on the PS bead surface. The suspension was then centrifuged at 5000 rpm for 5 min. To remove the loosely adsorbed PSS, the PS beads were redispersed in ethanol and washed before the deposition of the second layer. After the deposition of the first layer, the PS beads were redispersed in PAAm (20 mL) solution and shaken for 30 min, followed by centrifugation at 5000 rpm for 2 min. Thus, the layer‐by‐layer assembly was achieved by repetitive alternative depositions of PSS and PAAm until the desired number of layers (ten layers each) was deposited onto the PS beads. After every four bilayers, the PS beads were transferred to a new centrifuge tube to prevent aggregation. The coated particles were dispersed in DIW and treated with toluene for 15 min to etch the PS beads.PBA) was added to the polymeric pellets, and the resulting mixture was placed on an automated shaker plate at room temperature for 15 h in a closed container. The ethanol and E7PBA form an isotropic phase that can penetrate more readily through the walls of polyelectrolyte‐based microcapsules.PBA was observed to return to the nematic phase, resulting in trapping of the LC within the microcapsules. Excess E7PBA was then removed by centrifugation, and the remaining LC‐filled microcapsules were extracted into deionized water with gentle shaking. The LC‐filled capsules were then characterized using a polarized optical microscope. The polymeric microcapsule‐filled E7PBA (P‐E7PBA) was then sterilized under UV‐radiation and suspended in the respective medium for further experiments.The prepared polymeric microcapsules were washed twice with ethanol and centrifuged. The resulting pellets were then suspended in 1 mL of ethanol and shaken gently. E7 (100 µL) doped with pentyl‐biphenyl carboxylic acid  (E7Cell Culture: HUVEC and MCF‐7 cells were cultured in RPMI‐1640 supplemented with 10% FBS and 1% penicillin and streptomycin (1:1). Similarly, the U87 and Caco‐2 cells were cultured in MEM supplemented with 10% FBS and 1% penicillin and streptomycin (1:1). All cell types were cultured in Petri dishes for 2–3 days in a humidified atmosphere of 95% air and 5% CO2 at 37 °C. When the cells were in the exponential growth phase they were detached from the Petri dishes with 0.25% trypsin and resuspended in corresponding cell culture medium (unless otherwise mentioned) for further experiments.Cell Compatibility Test: HUVEC and U87 cells were separately seeded in 24‐well plates in their corresponding growth medium and were allowed to adhere for 3 h. The culture medium was then withdrawn from the wells using a micropipette. P‐E7PBA (sterilized overnight under UV light) was suspended in cell culture medium at different concentrations  and then added to the cell‐containing wells (≈1 × 106 cells mL−1). Cells without added P‐E7PBA droplets and those with added E7PBA were used as the positive and negative control, respectively. The cells were grown in a humidified environment of 95% air and 5% CO2 at 37 °C for 12 h. The medium was then removed and the cells were gently rinsed with PBS. Calcein AM (10 µL) and propidium iodide (PI (15 µL)) were mixed in PBS (5 mL) and added to the cells. The cells were allowed to stain for 25 min in a humidified environment of 95% air and 5% CO2 at 37 °C. The PBS was then gently removed with a pipette, the cells were rinsed with fresh PBS, and the cell medium was added to allow a longer time for efficient analysis. The live/dead cells were then observed using a fluorescence microscope.Microfluidic Channel Preparation: The PDMS microfluidic chips with straight channels were prepared using the photolithography technique. A silicon wafer (SW) was washed in gently boiling piranha solution (caution: piranha is corrosive and must be handled with care) for 1 h and subsequently washed with DIW and dried under nitrogen flow. The SU‐8 2050 negative photoresist was uniformly spin coated onto the wafer at a speed of 1200 rpm. The coated SW was baked at 65 °C for 20 min. A photomask was then placed on the SW, and it was exposed to UV light for 3 min. The SW was then baked for 10 min and developed with an SU‐8 developer, which generated a clear mold.The PDMS prepolymer and the initiator were mixed at a recommended mass ratio of 10:1 and poured into the mold. Bubbles were removed by vacuum, and the polymer was baked at 65 °C for 6 h. The polymerized PDMS was then peeled from the mold, cut, punched and sealed with glass substrate via oxygen plasma. The microfluidic chip used in this experiment has four straight channels. Each channel has a length, width, and height of 12 mm, 700 µm, and 100 µm, respectively. The volume of each channel was ≈0.84 µL.Cell Culture in Microfluidic Channels: The cells were first digested with trypsin, centrifuged, and resuspended in fresh culture medium. A cell density of ≈1 × 106 cells mL−1 was achieved by counting with a hemocytometer. The cell suspension was injected into the microchannel from the inlet and incubated for 12 h under a flow of 95% air and 5% CO2 at 37 °C. The inlets and outlets of the channels were covered by culture medium to prevent evaporation. The evaporation could change the salt concentration of the medium and affect cell viability. The medium was then refreshed, and the adhered cells in the channels were utilized for further analysis.Optimizing the Extracellular pH: First, the pH‐responsiveness of the P‐E7PBA droplets was tested in MEM at different pH values . The pH of the MEM medium was adjusted using citrate buffer. The P‐E7PBA droplets (0.25 mg mL−1) were dispersed in the media samples, and the orientation of E7 was observed using POM.PBA dispersed in culture medium (pH = ≈7.4) was then injected into the channels containing cells. The orientation of the P‐E7PBA droplets in the channels and on the cells was observed under cross‐polarization. All experiments were performed in a sterile environment to ensure the microbial‐free cells.A 0.5 µL aliquot of P‐E7−6m), ascorbic acid (1 × 10−6m), or amino acids (1 × 10−6m). Similarly, the same concentration of lactic acid, ascorbic acid, or amino acids was added to MEM + PBS (1:1). The orientation of the P‐E7PBA droplets was then observed in the MEM and MEM + PBS (1:1) samples containing these analytes. The P‐E7PBA droplets were dispersed in the MEM + PBS (1:1) mixture for further experiments.Next, to negate the effect of common pH‐reducing species, the MEM was supplemented with lactic acid  and injected into a channel containing the cells under analysis. The P‐E7PBA was allowed to immobilize on the cell membrane for 10 min. The amino groups on the outer layer of the LBL assembly facilitated immobilization due to the negative charges on the cell membrane. Subsequently, fresh MEM + PBS was introduced into the channels to wash out the nonimmobilized droplets. During the process, a few droplets were also attached to the glass under the channels, which may have been due to the interaction of slight negative charges on the glass surface with the amino groups on the outer layer of the polymeric microcapsule.3Imaging of NH: The P‐E7PBA droplets were tested in aqueous NH3 solutions of different concentrations (0.1‐1.5 × 10−6m) in PBS at pH = 7.4. For NH3 imaging in the cellular microenvironment, the cells with the immobilized P‐E7PBA in a microfluidic channel were first washed by flowing MEM + PBS (1:1) to achieve the complete replacement of channel medium with fresh medium. This process washed out all the cell debris and ions that were released from the cells to the medium. PBS was used to avoid pH changes in the medium. After immobilization, the fresh mixture was flowed a few times into the channels. The change in P‐E7PBA droplet orientation was then observed with the tpass. During the ammonia imaging, the pH of the medium was maintained at 7.4.Preparation of Microwell Flow Chip: A mold of the SW was obtained using a photolithography technique, as previously reported.Subsequently, a 3% aqueous solution of agarose gel was heated at 150 °C until the solution became transparent. The solution was then poured in the mold and was slowly cooled. The gel structure containing microwells was gently peeled from the mold surface. Each microwell had a diameter of 25 µm and a depth of 120 µm. A similar‐sized PDMS cavity was obtained from the mold design with the same procedure. The PDMS layer was placed over an agarose gel to obtain a microwell flow cell for subsequent experiments.3 at Single‐Cell ResolutionCell culture in the Microwell Flow Chip and Imaging of NH: The microwell flow cells were washed with PBS several times and sterilized under UV light for 3 h. The cells from the culture medium were then detached using 0.25% trypsin, washed with PBS, centrifuged, and redispersed in fresh medium at a final cell density of ≈1 × 106 cells mL−1. The cells were then injected into the inlet of the microwell flow chip, and the drag force along the direction of the flow helped to accumulate the cells into the microwells. The cells in the microwell flow cell were cultured for 3 h in 95% air and 5% CO2 at 37 °C.PBA was dispersed in a mixture of PBS and cell culture medium (0.25 mg mL−1) at pH = 7.4. The cells in the microwell flow device were washed several times with a mixture of PBS and cell culture medium. Gentle washing was performed because slightly harsh treatment could damage or detach the cells from the microwells. The P‐E7PBA suspension was flowed into the microwell flow device. Because of the hydrogel surface, the droplets were also attached onto surfaces other than the microwells. The R‐B configuration change of P‐E7PBA was observed with tpass. The cross‐polarization state of hydrogels cannot be observed as it can for LC in a glass microfluidic channel. Therefore, for the hydrogel‐based microwell flow chip, it was necessary to adjust the cross‐polarization angle during analysis.Sterilized P‐E73 in the Cell Culture MediumAnalysis of NH: The presence of NH3 in the culture medium as a function of time and temperature was investigated using the Berthelot method. The HUVEC, Caco‐2, U87, and MCF‐7 cells at a density of ≈1 × 106 cells mL−1 were cultured at room temperature and 37 °C in Petri dishes. The media samples were collected with a tpass of 0.5 and 3 h. The Berthelot reagent was prepared as previously reported.3 solution was then added to the mixture and the color was developed for 30 min. A standard curve at different aqueous NH3 concentrations, 0.5, 1, 1.5, and 2 × 10−6m, against the maximum absorbance wavelength (λmax) = 633 nm was obtained using UV–vis spectrophotometry. The Berthelot reagent was used as a reference solution.An equal volume (0.5 mL) of reagent A and reagent B were mixed in a vial. Aqueous NH3 was calculated from the absorption at λmax = 633 nm. Culture medium treated with Berthelot reagent in the corresponding condition was used as a reference solution. Due to the instrument detection limit, the standard addition/dilution method was also applied.Similarly, the medium sample was added to the reagent A and B mixture, and the color was developed for 30 min. The concentration of NHThe authors declare no conflict of interest.SupplementaryClick here for additional data file.SupplementaryClick here for additional data file.SupplementaryClick here for additional data file.


Simultaneous uptake and excretion of the two carbon species is referred to as inorganic carbon cycling. Often, inorganic carbon cycling is indicated by displacements of the extracellular dCO2 signal from the equilibrium value after changing the light conditions. In this work, we additionally use (i) the extracellular pH signal, which requires non‐ or weakly‐buffered medium, and (ii) a dynamic model of carbonate chemistry in the aquatic environment to detect and quantitatively describe inorganic carbon cycling. Based on simulations and experiments in precisely controlled photobioreactors, we show that the magnitude of the observed dCO2 displacement crucially depends on extracellular pH level and buffer concentration. Moreover, we find that the dCO2 displacement can also be caused by simultaneous uptake of both dCO2 and HCO3− (no inorganic carbon cycling). In a next step, the dynamic model of carbonate chemistry allows for a quantitative assessment of cellular dCO2, HCO3−, and H+ exchange rates from the measured dCO2 and pH signals. Limitations of the method are discussed.Photosynthetic organisms developed various strategies to mitigate high light stress. For instance, aquatic organisms are able to spend excessive energy by exchanging dissolved CO CAcarbonic anhydrase2dCOdissolved carbon dioxideDICdissolved inorganic carbon2dOdissolved oxygenICCinorganic carbon cyclingMIMSmembrane inlet mass spectrometry1Living organisms developed numerous adaptations to gain advantages in diverse environments. One branch of metabolic adjustments, widely spread throughout Bacteria, Plantae, Fungi, and Animalia kingdoms, is the evolution of so‐called futile cycles. These cycles are part of regulation of the cellular energy status 2) and excretion of bicarbonate (HCO3−), or vice versa simultaneous HCO3− uptake and dCO2 efflux. In cyanobacteria, HCO3− can enter the cells via the transporters BCT1, SbtA and BicA, and dCO2 by NDH‐I3 and NDH‐I4Chlamydomonas reinhardtii), SLC4 and its homologues (in diatoms), and possibly also other transporters in other species 2 is reduced to HCO3− by carbonic anhydrase (CA) or CA‐like enzymes, and HCO3− is transported for DIC assimilation by RuBisCo either to the carboxysome (in cyanobacteria), the pyrenoid  or elsewhere in the chloroplast . In algae, more pathways for DIC transport to chloroplast are known, e.g. the transport of intermediates of the C4‐like metabolism 2 is known to diffuse out of the cell, either through membranes or pores, however, HCO3− excretion still remains an open question.ICC, mediated through components of the carbon concentrating mechanism, can be defined as simultaneous uptake of dissolved carbon dioxide . Further, the conversion of dCO2 to HCO3−, mediated by CA‐like activity of NDH‐I3/4 , requires reduction equivalents such as NADPH or ferredoxin Although see ref. . Both coQuantification of carbon fluxes in aquatic photoautotrophic communities is of significant importance for understanding and accurate assessment of cellular carbon partitioning and carbon economy. In this study, we present methods for a quantitative description of inorganic carbon cycling between photosynthetic microorganisms and their environment. The often overlooked phenomena of carbon cycling performed by some photosynthetic microorganisms can negatively influence the accuracy of the measurement of carbon‐related properties of cells, e.g. their sequestration capacity, in dynamic culturing environments and can lead to incorrect bioenergetic calculations. Developed model and the technique for fast and accurate measurement of dissolved carbon dioxide provide a tool for identification and quantification of fast carbon fluxes that can be eventually used for smarter, model‐based, design of biotechnological solutions.2 signal, measured by methods with high sensitivity and high temporal resolution, such as membrane inlet mass spectrometry (MIMS). A representative example of a Dark‐Light‐Dark experiment (to detect ICC) is shown in Figure 2 increases mainly as a consequence of cellular respiration , whereas in the light phase dCO2 decreases mainly as a consequence of DIC assimilation . Most notably, the presence of ICC  causes an abrupt displacement of dCO2 .ICC can be detected from the dCO2 signal, also the pH signal can be used for ICC detection. For quantitative description of DIC exchange rates between photosynthetic cells and the aquatic environment, we developed a dynamic carbonate chemistry model. The model allows for detection of ICC activity and quantification of DIC reaction rates, and it extends previously published model 2 displacement at the transitions between dark and light phases need not be caused by ICC. In fact, under high buffer concentrations such a displacement can be observed also in the absence of ICC. On the other hand, for low buffer concentrations and low pH (<7) it is not possible to detect ICC solely from the dCO2 signal, but only in combination with the pH signal. We validated our model predictions experimentally, using MIMS in combination with well‐controlled photobioreactors. For the assessment of ICC, we therefore recommend to measure dCO2 and pH simultaneously  and hence to use weak buffer concentrations in the cultivation media.In this work, we show that in addition to the dCO2 and HCO3− exchange rates between photoautotrophic cells and the aquatic environment from experimental data. Our unique combination of a highly controlled experimental setup with a mathematical model can be used as a tool for detection and quantification of ICC in photoautotrophic microorganisms.The model can be further used to quantitatively determine dCO22.12, HCO3−, and H+ exchange rates between photoautotrophic cells and the aquatic environment and (ii) a quantitative assessment of ICC in photosynthetic microorganisms, we developed a dynamic model of carbonate chemistry and related processes. The model comprises the following variables (and constants):2]: concentration of dCO2[COHCO3−]: concentration of bicarbonate ions[+]: concentration of protons, [HCO3−], [H+], CP, TA . The differential algebraic equation system contains three ordinary differential equations and two algebraic equations:After introducing the carbonate pool Wolfram Mathematica 10  in particular, the function NDSolve with default options.Further details including model derivation as well as model analysis are provided in the Supporting Information. For numerical solutions of the differential algebraic equation system (3), we used 2.22.2.1Synechocystis sp. PCC 6803. The strain was kindly provided by Dr. Martin Hagemann. The inoculum cultures were pre‐cultivated in 250 mL Erlenmeyer flasks on air on a standard orbital shaker at 31°C, under 110 µmol(photons) m−2 s−1 of warm white LED light and in cultivation medium BG‐11 x g, 10 min), supernatant was discarded, and pellet was washed two times with HEPES‐free BG‐11 medium, to ensure minimal buffer concentration in the culture media. The culture was then inoculated into the photobioreactor.Model predictions were validated experimentally, using a cyanobacterium 2.2.2max ≈ 633 nm, Δλ1/2 ≈ 20 nm, Luxeon LXHL‐PD09; blue: λmax ≈ 445 nm, Δλ1/2 ≈ 20 enm, Luxeon LXHL‐PR09; both manufactured by Future Lighting Solutions, Montreal, QC, CA). The culture pH was continuously monitored by InPro3253 electrode , the own‐developed scripts allowed measurement of pH in temporal resolution of 1 s. Culture temperature was monitored by the same electrode and controlled by a Peltier cell incorporated in the instrument base. All other photobioreactor accessories and properties were such as described in Sinetova et al., 2012 For the validating experiments, we used a flat‐panel photobioreactor described in detail in 2.2.32 and dissolved oxygen (dO2) exchange between cells and cultivation media was measured by MIMS, described in detail in Zavřel et al., 2016 2), 44 (CO2), and 40 (Ar).Dynamics in dCO2.2.4K1 and K2 of BG‐11 cultivation medium at 30°C were determined using high‐sensitivity Total Organic Carbon Analyzer . All experiments for carbonate system parametrization were performed in a highly controlled environment of the photobioreactor to secure accurate and stable conditions, and the carbon analyzer was calibrated using certified premium range standards .Equilibrium constants 2 in BG‐11 medium, we adjusted pH of BG‐11 medium to pH 4.0 by addition of 1 M hydrochloric acid and aerated the medium with 15 000 ppm CO2 + air mixture  long enough to eliminate HCO3−; the bicarbonate elimination was validated by sequential sampling for total inorganic carbon quantification in the time interval of several hours.First, to determine concentration of the dCOK1 (relating dCO2 and HCO3−) was determined from a series of measurements in BG‐11 medium for slightly acidic to neutral pH levels, adjusted by addition of 1 M hydrochloric acid, following similar approach as for determination of dCO2; at each pH level the medium was aerated with 15 000 ppm CO2 + air mixture and the total inorganic carbon content was measured when the carbonate system equilibrated.The equilibrium constant K2 (relating HCO3− and CO32−) was determined from a series of measurements in BG‐11 medium under slightly alkaline pH levels, adjusted by addition of 1 M sodium hydroxide. Calculated equilibrium constants according to the carbonate system description  m2, dCO2, and pH during Dark‐Light‐Dark experiments was measured under pH levels 6.5, 7.3, 7.7, and 8.1. After 24 h of acclimation period, pH in the photobioreactor was decreased to 6.5 by addition of 1 M hydrochloric acid. dCO2 formed from HCO3− pool was bubbled out by air until the dCO2 concentration in the culture reached approximately 30 µM. Then, simultaneous measurement of gas exchange and pH was initiated. Each measurement consisted of three steps: (i) initial measurement in dark, (ii) measurement of photosynthetic activity at light, and (iii) final measurement in dark. Each step took 4 min.The dynamics in dO−1). During the measurements, bubbling was turned off and culture homogenization was secured by rotation of magnetic stirrer bar (ø5 × 35 mm) in a vertical plane (500 rpm). To secure light saturated conditions for the cells −2 s−1 of red light and 900 µmol(photons) m−2.s−1 of blue light. Between the measurements, the intensity of both lights was reduced to 10 µmol(photons) m−2 s−1. Once each measurement was completed, pH of the culture was increased by addition of 1 M sodium hydroxide to the next pH level (6.5–7.3–7.7–8.1). After pH increase, culture was bubbled with air until dCO2 level reached approximately 30 µM. Stabilization of pH took no longer than 45 min after each induced pH increase.Between the measurements, culture homogenization was secured by air bubbling through the photobioreactor cuvette , both dark respiration and light‐dependent carbon fixation  can be simulated together to abrupt dCO2 displacements at the beginning and at the end of the light phase as caused by inorganic carbon cycling . In dark, we assumed excretion of both dCO2 and HCO3− from the cells to the cultivation media due to dark respiration. Under light, we assumed carbon fixation together with ICC, where dCO2 is assimilated and HCO3− is excreted from the cells to the cultivation medium. To preserve charge balance, we assumed qH+ = qHCO3−, which results in constant total alkalinity TA, see Equation 3c.First, we studied the visibility of both dCO2 and pH signals for pH levels of 7, 7.5, and 8 and under low and high buffer concentrations. Under light, the exchange rate qCO2 was set to −150 nmol L−1 s−1 (CO2 uptake), whereas qHCO3− was set to +100 nmol L−1 s−1 (HCO3− excretion). The assumed magnitudes of the exchange rates qCO2 and qHCO3− are based on the previously published experimental data cBtot = 1 µM), the magnitude of the dCO2 displacement decreases with decreasing pH (from 8 to 7), although identical exchange rates qCO2 and qHCO3− are assumed , the magnitude of the dCO2 displacement remains almost constant (in the pH range 7–8), and the pH signal is shifted only negligibly  are summarized in Supporting Information Model predictions of dCO3.1.22 displacement in the presence of ICC. Figure 2 displacement can be observed even in the absence of ICC — in the case of sole carbon fixation where both dCO2 and HCO3− are taken up by the cells. This effect can be explained by analyzing the dynamics of dCO2 hydration which brings the system back (close) to equilibrium. As the model analysis shows (see Supporting Information Section 2 hydration rate v (Equation 2) does not directly follow the hydration rate constant k1 (Equation 1), but the “apparent” dCO2 hydration rate defined as k1(1+α); see Supporting Information Equation 4. The parameter α ≥ 0 depends on buffer concentration and pH in a complicated way (Supporting Information Section K1). The lowest value α ≈ 0 and thus the slowest dynamics occurs for high buffer concentration and alkaline pH. Only then, the net hydration rate v follows the hydration rate constant k1, and the slow dynamics of the system returning back (close) to equilibrium is visible as a dCO2 displacement. The dynamics of the dCO2 hydration rate v during Dark‐Light‐Dark experiments  under pH 7.0 and 8.0 as well as under low and high buffer is summarized in Supporting Information Figure 2. In Figure qCO2 and qHCO3− such that the resulting DIC fixation rate was −(qCO2 + qHCO3−) = −50 nmol L−1 s−1, both in absence and presence of ICC. In Figure 2 dynamics can be obtained. Indeed, the particular choice of exchange rates qCO2 and qHCO3− as used in Figure As a consequence, under high buffer, it can be hard or even impossible to distinguish between sole carbon fixation and carbon fixation with ICC, when only measuring dCO2 displacement. In the simulations summarized in Supporting Information 2 displacement is almost identical for all buffers, whereas in the absence of ICC, the dCO2 displacement decreases with an increasing difference between the pKa value of a particular buffer from the initial pH value of 8 considered in the simulation.The model can also be used to simulate the effect of various buffers  on the visibility of the dCOqCO2 and qHCO3− from experimental data (see Section 3.5), weak pH buffer and simultaneous monitoring of the dCO2 and pH signals dynamics is required. In the next section, we present a case study of such an experimental system where a precisely controlled photobioreactor is coupled with a membrane inlet mass spectrometer.Based on the results of the simulations, we conclude that optimal conditions for the detection of ICC as well as for identifying the exchange rates 3.22 and pH displacements under varying pH levels and buffer concentrations, we performed a series of Dark‐Light‐Dark experiments. High magnitudes of the dCO2 displacement under high buffer concentration are well documented in the literature 2 and pH dynamics in a Synechocystis sp. PCC 6803 culture during Dark‐Light‐Dark experiments. To be consistent with the simulations, the initial dCO2 concentration during the experiments was set to 30 µM. Additionally, all simulations shown in Figures 2 and pH signals for “CO2 users” — organisms taking up a higher fraction of dCO2 compared to HCO3−. The measured dCO2 dynamics in Synechocystis during our experiments also resembles dynamics typical for “CO2 users” 2 concentration (air), it is likely that all DIC transporters were active Synechocystis was most likely able to uptake both dCO2 and HCO3−. The results of the experiments are summarized in Figure 2 displacement became less visible and, on the contrary, the pH displacement became more pronounced. In particular, the pH displacement was the most visible at pH 6.5 , less visible at pH 7.3 , even less visible at pH 7.7 , and the least visible at pH 8.1 . It is important to note that this agreement between simulations and experiments was achieved although the rates qCO2 and qHCO3− as identified from the experiments  was almost identical for all pH levels (6.5–8.1), which indicates a negligible effect of the pH level on the light‐dependent photosynthetic reactions  from the measured dCO2 and pH signals. Mathematically, the identification of three time series from two noisy time series is an ill‐posed problem. The development of a numerically stable identification algorithm is beyond the scope of this work. As a first step, we assume equal HCO3− and H+ exchange rates  and implement a simple algorithm that involves data differentiation; see Supporting Information Subsection qCO2 and qHCO3−; the results are summarized in Figure The mathematical model can also be used for identifying the exchange rates 2 uptake and HCO3− excretion) was identified to be both qualitatively and quantitatively different for initial pH levels of 6.5–8.1. For initial pH 6.5  between cells and the environment, (ii) we predicted the visibility of ICC under various buffer concentrations and pH levels, and (iii) we experimentally validated the model predictions, using the combination of a precisely controlled photobioreactor and a high resolution membrane inlet mass spectrometer. In both simulations and experiments, we focused on slightly acidic to slightly alkaline pH range, since first, with pH increase, the pH displacement becomes hardly detectable even in non‐buffered systems due to (self‐) buffering capacity of the carbonate system, Figure 2 uptake can become significantly reduced or even inhibited In the present work, we developed methods for a quantitative description of inorganic carbon cycling (ICC) between photosynthetic microorganisms and their aquatic environment. In particular, (i) we developed a mathematical model that quantitatively describes dCO2 displacement at the beginning and at the end of the light phase ; see Supporting Information Equation 4. For pH = 7, when the hydration rate v shows a very short delay compared to pH = 8  identified from the experimental data  increase 10 times, and protons that are excreted from the cells (pressumably together with HCO3−) react with the both anions to a higher extent which leads to a reduced amount of “free” protons available for pH displacement.A further analysis showed that the magnitude of the pH displacement during ICC decreases with increasing pH in the range of 7–8 Figure , which i2 displacement can be detected only when the dCO2 hydration rate constant k1 (part of the “apparent” hydration rate constant k1 (1+α)) is small enough — in particular, as shown in Supporting Information −1. In this work, we experimentally determined the value of k1 as 0.04 s−1 . The current understanding of proton efflux in cyanobacteria is fully consistent with this assumption. Even though current carbon concentrating mechanism models consider two HCO3− transporters (SbtA and BicA) that require extracellular Na+ which is exchanged with H+ by the antiporter NhaS3, the photosynthetic and respiratory models consider at least three complexes in the cytoplasmic membrane that all work as proton (efflux) pumps: NDH1/2, COX, and P‐ATPase HCO3− and H+ cotransport in some strains qHCO3− and qH+ over time is reasonable; otherwise the cells would become acidified or basified over time. However, eventual fast fluctuations in both qHCO3− and qH+  can result in temporal qHCO3− and qH+ disbalance. This can lead to  incorrect qCO2 and qHCO3− rates identification from experimental data (see the following section for further discussion).Our mathematical model is based on several assumptions regarding carbonate chemistry such as fast equilibrium for reactions W, B, 1′, and 2qCO2, qHCO3−, and qH+, Figure +, K+, NO3−, NH4+The model further assumes that both kinetic and equilibrium constants buffering capacity of carbonate chemistry and hence a higher S/N with increasing pH. Noise reduction in the identified exchange rate qHCO3− at higher pH can be achieved by advanced data fitting methods involving regularization techniques. However, without direct measurement of the HCO3− dynamics, the identification of qCO2 and qHCO3− fluxes may still depend on model assumptions such as q HCO3− = qH+ (see the previous section for further discussion).In addition to predicting the visibility of ICC, the model was further used to identify the exchange rates qCO2 and qHCO3− identified from experimental data can be interpreted only as rough guides of ICC in general. The first analysis of our experimental data showed that ICC could take place throughout the whole light period  that each HCO3− molecule requires 1/3 ATP to be excreted from the cell , such a rate would burn 6.7 amol cell−1 s−1 ATP, that is, 35% of the ATP generated by photosynthetic light reactions: assuming 3 ATP produced per each O2 molecule, the dO2 production rate of 6.4 amol cell−1 s−1 (as derived from the data presented in Supporting Information −1 s−1 (and 6.7/19.2 = 35%). However, we note that a precise accounting of ATP  production/consumption is tricky since the stoichiometry of both dO2:ATP production and HCO3− excretion:ATP consumption can vary considerably over time. In addition, under high blue light as used in our experiments, one can expect a strong cyclic electron flow around photosystem I (PSI) that can shift the ratio of ATP:NADPH production significantly The amount of ATP “burned” during ICC by the cells can be significant since transport of 2 release:CO2 fixation) was ranging between 5.7–0.3 in the pH range 6.5–8.1. Such values represent a higher PQ variation than reported previously for Synechocystis. However, in previous works Synechocystis blue light preferentially affects PSI, resulting in cyclic electron flow The photosynthetic quotient in our experiments  times the true inorganic carbon fixation rate (qCO2 + qHCO3−), see Supporting Information Equation 8. Thus, the dCO2 signal slope depends on the pH level (Figure The model analysis also showed that the negative slope of the dCOl Figure . The “apl Figure . As showqCO2 and qHCO3−, and thus for the assessment of ICC is still missing. This work summarizes the complexity and limitations of ICC detection related to the effects of carbonate chemistry and to the current state of the art of the experimental techniques. Until a method for the dynamic and quantitative measurement of HCO3− concentrations will be available, both qCO2 and qHCO3− quantification will depend on a mathematical analysis involving extra assumptions. In this work, we outlined future developments of both experimental and modeling methods as necessary for a reliable ICC detection.A reliable method for the dynamic identification of both exchange rates https://identifiers.org/ecyano.experiment:31. Mathematical model is available online here: https://identifiers.org/ecyano.model:46.Source data for Figure 6 are available online here: The authors have declared no conflict of interest.Supporting InformationClick here for additional data file.


The optimized Mo‐doped Ta2O5 substrate exhibits a remarkable SERS sensitivity with an enhancement factor of 2.2 × 107 and a very low detection limit of 9 × 10−9m for methyl violet (MV) molecules, demonstrating one of the highest sensitivities among those reported for semiconductor SERS substrates. This remarkable enhancement can be attributed to the synergistic resonance enhancement of three components under 532 nm laser excitation: i) MV molecular resonance, ii) photoinduced charge transfer resonance between MV molecules and Ta2O5 nanorods, and iii) electromagnetic enhancement around the “gap” and “tip” of anisotropic Ta2O5 nanorods. Furthermore, it is discovered that the concomitant photoinduced degradation of the probed molecules in the time‐scale of SERS detection is a non‐negligible factor that limits the SERS performance of semiconductors with photocatalytic activity.Recent achievements in semiconductor surface‐enhanced Raman scattering (SERS) substrates have greatly expanded the application of SERS technique in various fields. However, exploring novel ultra‐sensitive semiconductor SERS materials is a high‐priority task. Here, a new semiconductor SERS‐active substrate, Ta Therefore, exploring a new type of semiconductor that has high SERS performance and that features further enhanced SERS activity to a limit is a high‐priority task.Currently, the objectives receiving the most focus regarding semiconductor SERS substrates are improving their SERS performance and exploring their intrinsic enhancement mechanism, and the two complement each other. As an increasing number of researchers are engaging in the study of semiconductor SERS substrates, research achievements regarding semiconductor SERS substrates have grown exponentially in recent years. From porous ZnO nanosheets,5. To obtain the highest SERS enhancement in semiconductor substrates, the semiconductor‐molecule system and experimental parameters must be carefully selected to match the SERS selection rules and produce cooperative resonance effects, including molecular resonance, molecule‐semiconductor CT resonance, and electromagnetic resonance including metal‐like surface plasmon resonance and Mie scattering resonance of semiconductors under an excitation laser. Therefore, we present a “coupled resonance” strategy for optimizing semiconductor SERS sensitivity in order to fulfill three quasi‐resonance Raman effects, molecular resonance λmol, molecule‐semiconductor CT resonance λCT, and semiconductor electromagnetic resonance λEM including plasmon or Mie scattering resonance,laser via a multicomponent design including bandgap engineering and morphology tuning. We invoke a quasi‐approximation here that is given as followsUsually, metal nanoparticles exhibit great SERS enhancement, which is mainly attributed to EM enhancement because EM enhancement is several orders of magnitude stronger than CM enhancement. However, whether EM‐SERS enhancement or CM‐SERS enhancement (including molecular resonance and CT resonance) is operative in reported semiconductor substrates, the individual contribution for SERS is usually less than 10SchemeAmong the factors in Equation 2O5 has many excellent properties, such as a high refractive index, excellent photoelectric performance, and high chemical stability.2O5) has never been reported. At the same time, with the discovery of the intrinsic outstanding SERS performance of Nb2O5,2O5, in which the element Ta is located in the same VB family as the element Nb.As a wide bandgap semiconductor, Ta2O5 nanorods (NRs) were first synthesized, and then energy band engineering through element doping  was adopted to further improve the SERS performance. The Mo‐doped Ta2O5 substrate exhibited a remarkable SERS sensitivity with an EF of 2.2 × 107 and a very low detection limit of 9 × 10−9m for methyl violet (MV), which is better than those of most reported semiconductor SERS substrates. The synergistic resonance enhancement mechanism of three components under 532 nm laser excitation, namely, i) MV molecular resonance, ii) photoinduced charge transfer (PICT) resonance between MV molecules and Ta2O5 NRs, and iii) EM enhancement around the “gap” and “tip” of anisotropic Ta2O5 NRs were demonstrated in our novel Mo‐doped Ta2O5 NRs by experiments and first‐principles calculations. This work offers a cost‐effective pathway to design novel ultra‐sensitive semiconductor SERS‐substrates.In this work, Ta2O5 SERS substrates, we discovered the concomitant photoinduced degradation of the probed molecules on the Ta2O5 substrates during the process of SERS detection by ultrafast spectroscopy. In addition to the well‐known phenomenon of photobleaching of dye molecules in metal SERS materials by strong lasers,Simultaneously, along with the synergistic realization of the good photocatalytic self‐cleaning capability of the ultra‐sensitive Mo‐Ta22.12O5 NRs and Mo‐doped Ta2O5 NRs were first obtained by an improved hydrothermal reaction according to the literature,2O5 NRs to derive hydrogenated Ta2O5 nanosheets (H‐Ta2O5 NSs). Transmission electron microscopy (TEM) and high‐resolution TEM (HRTEM) were used to study the morphological evolution and crystal structures of different Ta2O5 SERS substrates  with an inter‐planar spacing of 0.384 nm. This finding indicates that the Ta2O5 NRs preferably grew along the [010] direction. It can be clearly inferred from Figure 2O5 (Mo‐Ta2O5) still maintains the NR nanostructure after element doping. As the concentration of Mo added to the precursor increased, the nanorods exhibited an obvious increased length, whereas there were no significant changes in diameter. The average lengths were 25.5, 35.8, and 42.7 nm for the 10%‐, 15%‐, and 20%‐Mo‐Ta2O5 substrates, respectively . However, the low‐valence hydrogen‐reduced Ta2O5 exhibited a very different appearance. After annealing in Ar/H2 and deoxygenating over the H‐Ta2O5 substrate, the Ta2O5 NRs were completely converted to well‐crystallized H‐Ta2O5 NSs . As shown in Figure S2 (Supporting Information), the Ta2O5 NRs were crystallized with Ta2O5 (JCPDS. 79‐1375) phases with lattice constants corresponding to the orthorhombic Ta2O5 structure with space group Pmm2 . The strongest peak indexed to (010) suggested a preferential growth along the b axis, whereas other crystal planes, namely, (411), (1410), (020), and (2410), in Ta2O5 exhibited widened peaks due to the weaker crystallization; these crystal planes were highly aligned with the polycrystalline ring presented in the selected area electron diffraction (SAED) pattern of the Ta2O5 substrates  that (010) was still the strongest peak and that there was no significant shift in the XRD peak positions as the incorporation content of Mo increased, revealing that Mo was uniformly dissolved into Ta2O5 due to the similar ionic radius of Mo (0.65 Å) and Ta (0.64 Å).The shape‐controlled Tas Figure. The der2O5 and Mo‐doped Ta2O5, among which both of the Ta4f peaks presented an obvious displacement to lower binding energies , whereas XPS analysis of O1s exhibited a significant shift to a higher binding energy , indicating that some of the Ta5+ in both samples was reduced to a lower valence state. Figure S3c (Supporting Information) shows the high‐resolution XPS spectra of Ta4f in the H‐Ta2O5 sample. In addition to doublet peaks arising from Ta5+, there were two more unambiguous doublet peaks located at 28.17 eV (Ta4f5/2) and 26.25 eV (Ta4f7/2), which belonged to Ta4+ and suggested that reduction occurred during hydrogenation.VO), respectively , thus confirming the emergence of Ta4+ and the damage to the interlayer oxygen atoms in the H‐Ta2O5 NSs by hydrogen atoms . A similar reduction of Ta5+ to Ta4+ and the appearance of VO can also be observed in the Ta4f and O1s XPS spectra of Mo‐doped Ta2O5  was further used to obtain more detailed information about the superficial chemical state of the doped substrates. Ta and O can be clearly identified in the XPS spectra of both the H‐Ta2O5, X‐ray absorption spectroscopy (XAS) was adopted to detect their chemical states. Although the Mo3d peaks were completely submerged in the Ta4d peaks in the XPS spectra, the M2‐edge and M3‐edge of Mo in the XAS spectra /Mo4d (t2g), O2p‐Ta5d (e2g)/Mo4d (e2g), and O2p‐Ta6sp, respectively.2O5 substrates, peak a in the 15%‐Mo‐Ta2O5 and H‐Ta2O5 substrates was found to be relatively obvious, indicating the appearance of more oxygen vacancies or oxygen holes due to the high‐valence Mo6+ doping and the low‐valence hydrogen reduction . Under the same measurement conditions, the full width at half maximum (FWHM) of peak d was decreased followed by an increase with the increase of incorporated Mo6+ concentration . It can be attributed to that different doping concentration produce different orbital hybridization, and there are less core holes at the O 2p‐Ta 6sp energy level for 15%‐Mo‐Ta2O5.To clarify the behavior of the Mo dopants and the local structures of Mo and Ta atoms in Mo‐Ta2.26+ doping and low‐valence hydrogen reduction) on the SERS performance of Ta2O5 substrates. The dye MV was used as a Raman probe to examine the Raman enhancement behavior of the Ta2O5 substrates because MV exhibited a strong optical absorption peak and molecular resonance near the laser excitation wavelength of 532 nm (λmol ≈ λlaser). The intrinsic Raman spectra of MV and substrates are shown in Figure S4 (Supporting Information). Interestingly, the hydrogenated Ta2O5 substrate exhibited a much better Raman enhancement ability than the Ta2O5 NR substrates when detecting 10−6m MV, whereas its SERS behavior was regretfully much inferior to that of the 15%‐Mo‐Ta2O5 substrate , 1371 , and 1179 cm−1 . All these peaks and the other observed SERS peaks, which are listed in Table S2 (Supporting Information), agreed well with the characteristic peaks of MV.6+ into the Ta2O5 NR substrate, its SERS performance obviously became superior to that of the pure Ta2O5 NRs. Moreover, as the amount of Mo incorporated gradually increased, the SERS signal of 10−7m MV first exhibited an improvement followed by an attenuation. This may be due to the most suitable doping concentration to obtain the best energy band structural match between MV molecules and the doped Ta2O5. Among the concentrations evaluated, the optimal doping concentration of Mo was 15%, and it can be found from Figure 2O5 SERS substrate can also exhibit better performance when detecting 10−8m MV. Moreover, even when the concentration of MV aqueous solution was diluted to 9 × 10−9m, the Raman lines of MV molecules on our 15%‐Mo‐Ta2O5 substrate at 1617, 1587, 1529, 1371, and 1179 cm−1 could still be conspicuously identified despite the gradually apparent Raman signal background from the substrate . To the best of our knowledge, this SERS performance is one of the highest sensitivities among those reported for semiconductor SERS substrates  can be introduced to evaluate the surface‐enhanced Raman intensity, which is proportional to |Rmol−CT(ω)|2 for a single dominant term. Rmol−CT(ω) can be expressed asAccording to the “Unified View” presented by Lombardi et al.,Eα,β represents the electric field at the surface  of the substrates due either to the surface plasmon or the Mie scattering resonance, and QK is the molecular normal mode. The molecular resonance (μmol) and the CT resonance (μCT) are coupled to each other through the Herzberg–Teller coupling constant (hmol−CT). ε1and ε2 refer to the real and imaginary parts, respectively, of the substrates' dielectric constant and ε0 is the real part of the dielectric constant of the surrounding medium. χ is a constant factor that accounts for the geometry of the substrate if it deviates from a spherical shape. From Formula (2), there are three parts in the denominator jointly contributing to the SERS intensity. When the incident light frequency coincides with a certain resonance frequency of the system, the corresponding portion must be involved in the SERS enhancement. The EM resonance dominates when ε1 (ω) = −2ε0. When ω  = ωCT, there is CT resonance involving the transfer of electrons between the molecules and the substrates. Accordingly, ω  = ωmol indicates molecular resonance. Thus, one or more resonances will play a leading role when given an incident laser with a fixed frequency. Which one, two or three of these specific resonances will participate depends on the specific molecular and substrate parameters. Usually, nontotally symmetric vibration in addition to totally symmetric modes are excited through Herzberg–Teller vibronic coupling,1 vibration modes tend to dominate the spectrum when only surface plasmon resonances contribute through the Franck–Condon term.−1 can be ascribed to the totally symmetric a1 vibrations, whereas many other lines at 1587, 1529, 1435, 1371, 1295, 1179, 915, and 826 cm−1 can be assigned to the nontotally symmetric e modes.2O5 substrates were considerably dominated by the nontotally symmetric e vibrations, indicating a dominant CT or molecular resonances in this case. As previously discussed, both high‐valence Mo6+ doping and low‐valence hydrogen reduction resulted in the appearance of lower‐valence Ta4+ and VO. The SERS performance discrepancy among these doped Ta2O5 substrates was most likely caused by the different resonance intensities induced by the CT between the substrates and probed molecules under the incident laser.In the expression, 2O5 substrates. Figure2O5 NRs, 15%‐Mo‐Ta2O5 powder and H‐Ta2O5 powder with/without MV absorption. The probed molecule MV exhibited a strong optical absorption peak and molecular resonance (λmol) near the laser excitation wavelength of 532 nm, indicating an intrinsic resonance frequency matching with the 532 nm incident laser as followsWe first analyzed the contribution of the CM (including MV molecular resonance and CT resonance) to the SERS performance of these Ta2O5 and H‐Ta2O5 substrates, it can be clearly identified that the absorption peaks of the MV all presented certain degrees of blueshift and broadening, revealing a strong chemical interaction and CT process between the MV and our Ta2O5 substrates.2O5 complexes were located in the wavelength region of 500–600 nm and indicated CT resonance in this range, which was very close to the excitation wavelength (532 nm). Thus, the quasi‐resonance λCT ≈ λlaser was tenable here and indicated the dominance of the CT process in the surface‐enhanced Raman spectrum.After the probed MV molecules were adsorbed on the surface of the 15%‐Mo‐Ta2O5 substrates, Ta2O5, Mo‐Ta2O5, and H‐Ta2O5 models were constructed to investigate the specific degree of charge‐transfer in these three complex systems. Incorporation of Mo into the Ta2O5 NRs had two structurally different types: preferential occupation of the Mo atoms in the large lattice gap site of Ta2O5 or substitution of the Ta atom on the lattice position with Mo atoms. According to the XRD results, which showed no obvious XRD peak displacement of Ta2O5 after Mo doping, the incorporated Mo6+ was most likely in the mode of substituting Ta5+ due to the similar ion radius of Mo6+ (0.65 Å) and Ta5+ (0.64 Å). Therefore, we constructed a crystal structure of Ta2O5 NRs with a space group of Pmm2 according to the XRD results , and then replaced the Ta atom with a larger Mo atom to obtain a crystal structural model of Mo‐Ta2O5 . Similarly, according to the formation of NSs observed in TEM analysis and the appearance of oxygen vacancies in XPS analysis, the H‐Ta2O5 crystal structure was constructed by substituting the interlayer oxygen atoms with H atoms to form the H‐Ta2O5 model .To further analyze the effect of the different element doping strategies in energy band engineering on the SERS performance of Ta2O5 NR, Mo‐Ta2O5 NR, and H‐Ta2O5 NS substrates were calculated and are shown in Figure S5 (Supporting Information). Consistent with the experimental results, the calculated bandgap of the Mo‐Ta2O5 NRs became narrower (0.67 eV) than that of the Ta2O5 NRs (2.062 eV), which was due to the appearance of a tailed state energy level under the CB of Ta2O5 after replacing the Ta atom with Mo to form the Mo—O—Ta chemical bond. In contrast, both the CB and the VB positions shifted down due to the lower electron energy after hydrogenation and accordingly produced a narrower bandgap in H‐Ta2O5 (1.203 eV). Figure S6 (Supporting Information) compares the calculated and experimental Raman spectra of MV. The lines in the density functional theory (DFT)‐calculated Raman spectra of MV agree with the experimental results well, suggesting that the theoretical calculation was reasonable and feasible. The static Raman scattering spectra of a single MV molecule and MV adsorbed on the Ta2O5, H‐Ta2O5, and Mo‐Ta2O5 clusters are shown in Figure2O5 especially the modes at 1176 and 1376 cm−1. Predictably, a more prominent enhancement in the lines at 1176, 1376, 1528, and 1632 cm−1 on Mo‐Ta2O5 can also be observed in Figure 2O5, suggesting a very strong CT process between the MV molecules and element‐doped Ta2O5 substrates. To illustrate the increased SERS activity of the H‐Ta2O5 and Mo‐Ta2O5 substrates, the polarizabilities of the MV‐Ta2O5, MV‐H‐Ta2O5 and MV‐Mo‐Ta2O5 complexes . The resonance excitation wavelengths for the CT process in these three MV‐Ta2O5, MV‐H‐Ta2O5 and MV‐Mo‐Ta2O5 complexes were 390, 451, and 519 nm respectively, among which the energy band and the CT resonance frequency of the MV‐Mo‐Ta2O5 complex (λCT) best matched with the incident 532 nm excitation wavelength (λlaser) as follows2O5 to the highest occupied molecular orbital (HOMO) of MV with a CT amount of 0.153 e  and band structure diagrams of the Ta2O5 NRs from the CM, the contribution of the EM enhancement around the “gap” and “tip” of anisotropic Ta2O5 NRs to the surface‐enhanced Raman intensity under 532 nm laser excitation should not be underestimated. The finite element method (FEM) was used to simulate the surface electric field distribution of one Ta2O5 NR, two Ta2O5 NRs with a gap position and Ta2O5 NS. The strongest electric field enhancement factor for the single Ta2O5 NR under a 532 nm excitation laser was only 3 . Usually, there are many Ta2O5 NRs stacked and crossed together randomly in our sample, and many crossing and gap locations appear. Certainly, the strongest electric field enhancement factor can even reach ≈9 at the “angular” and “gap” positions of the two Ta2O5 NRs under irradiation with a 532 nm laser , which can be assumed to be modest “hot spots,” which are well known in plasmonics. Thus, the electromagnetic resonance can achieve three orders of magnitude of enhancement in SERS when the Ta2O5 NRs are in a good relative position. Considering the high density of hot spots within the powder of aggregated Ta2O5 NRs, the EM contribution to the SERS enhancement can be even higher. Thus, the strong electric field enhancement at the angular and gap positions of the Ta2O5 NRs can well explain the strong electromagnetic enhancement of our Ta2O5 NRs substrate under 532 nm excitation light. For the H‐Ta2O5 NS substrates, the largest simulated electric field enhancement factor under the incident 532 nm laser was 3.6 . Although there was a stronger electric field enhancement by the Ta2O5 NS than by the single Ta2O5 NR, the smaller size and sharper corners of the Ta2O5 NRs made them easier to generate stronger electric field enhancement when they were aggregated, thus demonstrating a stronger electric field distribution around the “gap” and “tip” of anisotropic Ta2O5 NRs and the possible greater contribution of the NRs (6 nm in diameter) than the NSs (250 nm in diameter) to the surface‐enhanced Raman intensity. We further simulated the electric field distribution around these Ta2O5 substrates at two different excitation wavelengths (633 and 785 nm), both of which induced a slightly weaker electric field than the 532 nm laser in all three models and verified that 532 nm excitation light provided the best electromagnetic field enhancement. Hence, among the current excitation lasers, the 532 nm laser was the most compatible with the electromagnetic resonance of our Ta2O5 substrate; here, the λEM was considered to be approximately equal to λlaser as followsIn addition to the MV molecular resonance and the PICT resonance between MV molecules and Ta2O5 substrates had poor performance when detecting 10−6m MV under irradiation with 633 and 785 nm lasers , which was most likely caused by the mismatch between the excitation laser and the molecular and CT frequencies.However, the 15%‐Mo‐Ta2O5 NRs for the carefully selected dye MV was obtained, and can be attributed to the synergistic effect of the molecular resonance (λmol ≈ λlaser), PICT resonance (λCT ≈ λlaser), and electromagnetic resonance (λEM ≈ λlaser), which was realized by regulating the PICT and electromagnetic resonance frequencies of our Ta2O5 substrates to be quasi‐equivalent to the given 532 nm laser by energy engineering through element doping. This result can be well understood and described by a recent theoretical model of SERS,mol ≈ λlaser) and PICT (λCT ≈ λlaser) belong to the set of microscopic strategies, which can be described by enhanced molecular Raman cross‐section or polarizability, whereas the mechanism of electromagnetic resonance (λEM ≈ λlaser) belongs to the category of mesoscopic strategies, which are closely related to the well‐established local field enhancement of Raman scattering. Importantly, the “coupled resonance” strategy is expected to be further applied as a guide to design different semiconductor SERS substrates for a better detection of many other molecules in the future.In summary, based on our presented “coupled resonance” strategy, extraordinary SERS performance of our 15%‐Mo‐Ta2.42O5 substrates . As shown in Figure S11 (Supporting Information), a clear distinction between the dynamics of MV‐Ta2O5 and pure Ta2O5 can be observed. As illustrated in Figure S12 (Supporting Information), laser light illumination can also induce direct photobleaching of the MV sample without Ta2O5. Therefore, a) the photocatalytic degradation of MV molecules by Ta2O5 and b) the direct photobleaching for the MV molecules (without Ta2O5) together contribute to the photoinduced decay. Each of them has a higher decay rate with increasing laser power. Because the photoinduced carrier behavior is also related to the PICT process, the photocatalytic degradation process of the MV molecules under the catalysis of the Ta2O5 substrates should not be ignored during Raman measurements. Moreover, we examined the photocatalytic degradation ability of our Ta2O5 substrate for MV molecules under irradiation with simulated daylight . Despite the poor photocatalytic degradation ability of Ta2O5 NRs, the self‐cleaning ability of the 15%‐Mo‐Ta2O5 substrate under simulated visible light was obvious enhanced (quickly degrading 82% of the MV molecules within 10 min), demonstrating that the 15%‐Mo‐Ta2O5 substrate possessed both optimal photocatalytic degradability and superior SERS performance. More precisely, another experiment was performed to determine whether the photodegradability of the semiconductor had an effect on our Raman test results. We focused the 532 nm incident laser at a point on the sample and collected the SERS signal every 20 s. It can be observed from Figure 2O5 substrate in Figure 2O5 substrate were obviously enhanced  , which provided the most convincing evidence for our previous conjecture. In the presence of photodegradation, the molecular Raman scattering cross‐section or polarizability could be significantly decreased, perhaps because of molecular chemical structure changes or even damage under strong laser irradiation.Whether there were factors other than the disparity of the dominant enhancement mechanism that constrained the SERS performance improvement of semiconductors was an interesting research focus. An unusual phenomenon was observed in our SERS experiment. The collected SERS signal decay took place when we repeatedly detected MV at a fixed point of Tas Figurea. It wasd Figure c, which 2O5 SERS substrates because our substrates were photodegrading the probed MV molecules during the SERS measurements. Notably, our sample can still output stable SERS signals as long as the detected position was slightly changed  of the Raman lines at 1179 and 1617 cm−1 were calculated as 12.5% and 13.5%, respectively . Thus, a good SERS signal reproducibility can be achieved in our 15%‐Mo‐Ta2O5 substrates. Moreover, our 15%‐Mo‐Ta2O5 substrates also have a good stability to storage in air atmosphere without the problem of easy agglomeration and oxidation failure like noble metal nanoparticles, it can still show good SERS performance after storage in air for more than three months .Undoubtedly, the single‐point‐detected SERS signal was not reproducible for the photocatalytic Tad Figure e, becaus32O5 by energy band engineering, which was implemented through multiple elemental doping methods . Among them, the Mo‐doped Ta2O5 substrate exhibited a remarkable SERS sensitivity with an EF of 2.2 × 107 and a very low detection limit of 9 × 10−9m for the carefully selected MV molecules, which, to the best of our knowledge, is one of the highest sensitivities among those reported for semiconductor SERS substrates under a specific laser excitation wavelength of 532 nm and even parallels that of a noble metal without “hot spots.” This extraordinary SERS performance can be attributed to the synergistic realization of molecular, PICT and electromagnetic resonance on the Mo‐doped Ta2O5 NR substrates under the 532 nm excitation laser according to our quasi‐approximate equation, which may provide guidance for the design of highly sensitive semiconductor SERS substrate materials in the future. Simultaneously, unambiguous and non‐neglectable photodegradation of MV on the Ta2O5 substrate within the time scale of the Raman test was also revealed by ultrafast spectroscopy, and thus we proposed an important point of view for the first time: the photocatalytic ability of many conventional semiconductor SERS substrates, such as ZnO, TiO2, and CdS, may be an important factor that limits their SERS performance. Finally, we expect that rapid measurements of the SERS signal of those degradable probe molecules on the surface of photocatalytic semiconductor SERS substrates via ultrafast Raman spectroscopy is probably helpful for discovering more sensitive semiconductor SERS‐active materials.In this work, the important “coupled resonance” strategy of matching SERS selection rules was presented to optimize the SERS performance of a novel semiconductor SERS‐active substrate Ta42O5 NRs, H‐Ta2O5, and Mo‐doped Ta2O5 SubstratesSynthesis of Ta: The Ta2O5 NRs were synthesized by the hydrothermal method according to the literature.2O5 powder , which was reprecipitated from the mixture by adjusting the pH to 9. Then, the precursor was obtained by redissolving the freshly formed precipitate into a 60 mL mixed solution containing hydrogen peroxide  and ammonia  at a volume ratio of 5:1. Before the hydrothermal reaction, the precursor was slowly heated at 60 °C for 1 h to promote the decomposition of H2O2, and then it was transferred into a PPL‐lined stainless‐steel autoclave (100 mL) to carry out the reaction at 240 °C for 36 h. Finally, the resultant product was thoroughly rinsed with deionized water and ethanol several times and dried naturally for subsequent characterization. The synthetic process for Mo‐doped Ta2O5 was fundamentally similar to the above process. The Mo‐doped Ta2O5 samples were prepared by mixing a certain amount of ammonium molybdate  into the precursor. The molar ratios of the Mo added to Ta were 10%, 15%, and 20%, and the resulting samples were labeled 10%‐Mo‐Ta2O5, 15%‐Mo‐Ta2O5, and 20%‐Mo‐Ta2O5, respectively. The H‐Ta2O5 sample was prepared by hydrogenating Ta2O5 NRs in a H2/N2 atmosphere (volume ratio: 1/9) at 1200 °C for 6 h.2O5 NRs, H‐Ta2O5, and Mo‐doped Ta2O5 SubstratesCharacterization of Ta: The micro‐morphology of Ta2O5 NRs, Mo‐doped Ta2O5 NRs, and H‐Ta2O5 NSs was determined by a JEM‐2100F field‐emission source TEM, and HRTEM was used to further obtain the size and inter‐planar spacing of the lattice fringes of these different Ta2O5 substrates. The surface element and chemical state were examined via XPS with a Thermo Fisher Scientific ESCAlab250. Characterization of the crystallinity was performed by XRD. XAS was carried out at the photoemission endstation at the BL10B beamline in the National Synchrotron Radiation Laboratory (NSRL). All XAS spectra were recorded in total electron yield (TEY) mode using a sample current measurement. UV–vis diffuse reflectance spectra were used to obtain the information on the optical properties and energy band structure of the substrates. All the Raman and SERS spectra were collected on a Renishaw inVia Reflex Raman spectrometer with excitation wavelengths of 532, 633, and 785 nm. For all Raman tests under each changed condition, a fresh position on the same sample was re‐selected.SERS Activity Measurement of Substrates: An MV aqueous solution with a concentration of 10−6–9 × 10−9m were used for the SERS detection. Raman spectra were then collected by dropping a dose of MV aqueous solution (10−6–9 × 10−9m) with a volume of 1 µL on the surface of the samples and then drying for 1 h. The excitation wavelength was 532 nm and a 10 ×/0.30 objective lens was used to focus the laser beam. SERS activity measurement of substrates were conducted under a laser power of 5 mW and a total exposure time of 20 s, which were acquired with a single time of 1 s and accumulation times of 20 (1 s × 20). The signal intensity of each Raman data was averaged from three detected Raman signals from three randomly selected points on the surface of the samples. The 2D‐Mapping SERS signals of 10−7m MV on the surface of 15%‐Mo‐Ta2O5 substrate were collected under the laser power of 5 mW and a total exposure time of 8 s.2O5 Substrates under Simulated SunlightPhotodegradation of MV on Ta: First, 0.003 g of Ta2O5 sample  were first immersed into 3 mL of 10−5m MV aqueous solution. Then, the 10−5m MV aqueous solution containing the Ta2O5 NR, 15%‐Mo‐Ta2O5, and H‐Ta2O5 sample at the bottom of the cuvette was directly used in order to clearly see the variety of the absorption peak of MV. These samples were irradiated with simulated daylight using a xenon lamp source, and the UV–vis spectra of the MV photocatalyzed by the Ta2O5 substrates at different irradiation times were recorded and compared.2O5 Substrates under the 532 nm LaserPhotodegradation of MV on Ta: The SERS spectra of the MV molecules on the 15%‐Mo‐Ta2O5 substrate were collected at one fixed irradiation point with an excitation wavelength of 532 nm at a laser power of 0.5 mW and a total exposure time of 20 s (1 s × 20). The next nine complete SERS signals were continually collected in a constant position according to this condition to acquire the SERS signal of 532 nm‐laser‐degraded MV on the 15%‐Mo‐Ta2O5 substrate. Under the fixed laser wavelength and laser power (532 nm and 0.5 mW), the detected SERS signal (after homogenization) of 10−6m MV on 15%‐Mo‐Ta2O5 substrate at different detected time  were compared to study the effect of photocatalysis on SERS performance under the different detection time. When fixing the same detected time and the accumulation times (0.1 s × 40) under the 532 nm incident laser, the detected SERS signal (after homogenization) of 10−6m MV on 15%‐Mo‐Ta2O5 substrate with varying laser powers  were compared to study the effect of photocatalysis on SERS performance under the different laser powers.The authors declare no conflict of interest.SupplementaryClick here for additional data file.


Data was collected for eleven C16H34/C18H38 compositions for each solvent used. Raw crystallisation and dissolution data is provided over a range of solution concentrations and cooling rates used under a poly-thermal crystallisation methodology. Equilibrium saturation temperature data is also presented for each composition, concentration and solvent system, indicating the trend in solubility for each solution.The data presented in this article relates to the crystallisation of hexadecane (C Specifications TableValue of the data•16H34/C18H38 alkane mixtures in HVO fuel under cold weather conditions is a current technological problem and isn’t well understood, therefore, data collected in relation to this provides an insight into the behaviour.Crystallisation of binary C•16H34/C18H38 alkane mixtures is also important in terms of the blending of HVO derived biofuel into conventional diesel fuel.Crystallisation of binary C•The data enables key nucleation parameters to be determined as well as the mechanism of nucleation, leading to a greater understanding of how crystallisation processes in HVO fuels occur.•Future work on further understanding and potentially controlling alkane crystallisation in HVO fuel with a focus on additive selection can be built from this data.•The current global focus on ‘cleaner’ transportation fuel in order to reduce environment global warming impact means this data is very relevant towards current and future advancements.1Tc) and dissolution (Tdiss) temperatures for each of the eleven C16H34/C18H38 compositions at each cooling/heating rate (q) used for the crystallisation experiments and each solution concentration are shown in 16H34/C18H38 binary mixtures.Average crystallisation (Te) patterns as a function of C16H34/C18H38 mixtures in the three solvents dodecane, kerosene and toluene over the range of compositions used and solution concentrations. Similar trends are seen over the range of solvents used with regards to the changing Te values for different compositions and concentrations. The data highlights that the shape of the solubility profile is broadly independent of both the solvent type  and the solute concentration.22.1Model compounds present in petrodiesel and the main constituents of HVOs were chosen for this study: hexadecane and octadecane, which were chosen alongside solvents that are representative of a diesel fuel mixture, in this case an aliphatic (dodecane), aromatic (toluene) and a mixture of the two cases (kerosene), see 2.2The crystallisation experiments were carried out using the Technobis Crystal 16® system 2.32.3.118H38 in each C16H34/C18H38 sample were first prepared. For each composition of the C16H34/C18H38 mixture, the solutions were made in four concentrations ,  and  for solvents of dodecane, kerosene and toluene, respectively. Each sample was weighed using a balance with ±0.1 mg accuracy.All solutions were prepared on a 5 ml scale, enabling a sufficient amount of solution to be created for use in a single block of the Technobis Crystal 16® system. 11 binary mixed samples of differing molar ratios varying from 0% of CNext, the mixtures were placed in a shaker with an external temperature control system (F32 Julabo temperature bath), at 55 °C for 30 min, with no shaking, in orderto form a melt. After this, a Fisherbrand 100–1000 μl micropipette was used to add 5 ml of toluene to each concentration sample. The resulting mixtures were placed in the same shaker, at 50 °C for 30 min under a shaking rate of 150 rpm, in order to form a homogeneous liquid solution. Next, for each concentration 4 Technobis Crystal 16® 1 ml vials were filled with 1 ml of the solution using a Fisherbrand 100–1000 μl micropipette and a standard small magnetic stirrer was added to each vial. This resulted in one composition forming sixteen 1 ml glass vial samples, with four vials containing one of the set concentrations.2.3.2Each vial contained a magnetic stirrer, which was set to stir at 700 rpm for all samples analysed. Each block contained the four concentrations to be analysed, as described previously, meaning one cooling/heating rate (q) would be used over the entire range of concentrations for each solution composition. Different temperature cycles were set up for each block in the unit using external temperature control and the Crystal16 computer software, and due to the high amounts of data recorded by the system, the cooling/heating rates (q) of 1 °C/min, 2 °C/min and 3.2 °C/min were run initially and upon their completion the cooling/heating rate of 0.25 °C/min was run. Each temperature cycle began by heating the solutions to 40 °C, with this temperature being held for one hour to ensure that complete homogenization had taken place and were then subsequently cooled at a set rate, as aforementioned, to −15 °C. This temperature was then held for an hour to allow equilibration, followed by an increase in temperature back to 40 °C at the specified rate. Each temperature cycle was performed five times to obtain average values for the crystallisation and dissolution temperatures. This enabled data fitting improvement, whilst also reducing the standard deviation (std) of the measured temperatures.Tc) and dissolution (Tdiss) temperatures were estimated from turbidity data, which ranged from 0% for a fully crystallised solution and 100% for a homogeneous solution. Tc was taken as the point where light transmittance dropped by 10% from 100% and Tdiss was taken at the point where light transmittance reached 100%. The collected Tc(q) and Tdiss(q) data was used to form Tc(q) and Tdiss(q) graphical lines that were extrapolated back to q=0 °C/min in order to determine equilibrium saturation temperatures (Te).Once the unit had run the cooling rates over the range of concentrations for a solution composition, data on turbidity was collected in the form of the relationship between the transmission of a laser through the sample and the temperature of the sample. Crystallisation (


However, the mechanism is not yet understood. Now, a series of compounds [(RSn)4E6] CO2Et; E=S, Se), were prepared, characterized, and investigated for their nonlinear optical properties. With the exception of crystalline [(BnSn)4S6], all these compounds exhibit WLG with similar emission spectra; slight blue‐shifts are observed by introduction of cyclopentadienyl substituents, while the introduction of Se in the inorganic core can provoke a red‐shift. These investigations disprove the initial assumption of an aromatic substituent being a necessary precondition; the precondition seems to be the presence of (cyclic) substituents providing enough electron density.Adamantane‐type organotin chalcogenide clusters of the general composition [(RT) In search of the preconditions for the generation of highly directed white light by means of amorphous molecular materials of the general formula [(RT)4E6] , nine new compounds were studied. Surprisingly, R does not need to be an aromatic ligand, in striking contrast to previous assumptions. Organo Group 14 chalcogenide clusters are organic/inorganic hybrid compounds consisting of an inorganic cage, which are derived from chalcogenido Group 14 anions4S6] (Sty=4‐vinylphenyl),4E6] .4S6] has been obtained as an amorphous powder, but DFT calculations reveal that the adamantane‐type structure are favored over the double‐decker‐type isomer by ca. 30 kJ mol−1. While compounds that lack inversion symmetry are widely known for second‐harmonic generation (SHG), we observed white‐light generation (WLG) upon irradiation with a commercially available continuous wave (CW) near‐infrared laser diode.In the context of our investigation of functionalized organo Group 14 chalcogenide clusters,4S6] and [(PhGe)4S6] exhibit WLG, while [(PhSi)4S6], [(MeSn)4S6] and [(NpSn)4S6] do not emit white light; yet, these compounds still show non‐linear optical properties by strong SHG instead.4S6], this is easily attributed to the crystallinity of the compound, which suppresses WLG. In the case of [(MeSn)4S6], the organic substituent shell does not contain an aromatic π‐electron system; as [(MeSn)4S6] lacks any evidence for long‐range order but shows SHG, the presence of π‐aromatic substituent molecules was intuitively assumed to be a necessary condition for WLG. The lack of WLG observed for the naphthyl‐substituted [(NpSn)4S6] was attributed to beginning long‐range order in the amorphous powder due to π‐stacking.We have furthermore prepared a range of adamantane‐type clusters with different organic substituents and Group 14 elements:  CO2Et, η1‐Cp, Cy; E=S, Se) have been prepared according to Equation Clusters of the type  (A) in Figure Upon reaction of the corresponding organotin trichlorides and (Me4S6] (A) and [(PhSn)4Se6] (1), we do not see a significant change in the shape of the emission, thus concluding that the WLG is largely independent from the composition of the inorganic core here. This is similar to what has been reported for the variation of the Group 14 element before.To address question 1, we compare the emission spectra of the sulfide clusters with those of the selenide analogues. The observations will be discussed at each of the homologous pairs along this report and summarized at the end. In case of compounds ),4S6]),2 and 3). Although we did not expect crystalline compounds 2 and 3 to generate white light, we investigate their structures, and also their non‐linear optical response.Apparently, the methylene groups in the benzyl substituents give the molecules the necessary flexibility to orient in a way that allows for an efficient packing in a crystal lattice. Hence, although enhanced flexibility of substituents often disturbs long‐range order, and also leads to the remarkably amorphous powders of most of the clusters discussed herein, the benzyl‐substituents seem to lead to an opposite effect for a gain of lattice energy or alternate second‐order interaction energy. So far, we have identified three possible ways to do so in this class of compounds: 1) beginning long‐range order if the aromatic system is large enough for efficient π‐stacking (as found for naphthyl substituents in  are capable of white‐light generation (WLG) if they fulfill the following preconditions: The materials need to contain electron‐rich (cyclic) substituents, which may (but do not need to) possess π‐electrons, and which do not need to be directly bonded to the inorganic cluster core, as long the spacer group does not cause crystallization. A point that could not be clarified so far is the impact of a homologous replacement of sulfur atoms with its heavier congeners on the emission properties, while the effect on the absorption properties is clearly a red‐shift. Here, we need to refer to future comprehensive work into this direction.We report on a study that provides a big step forward in the understanding of this class of white‐light emitters based on adamantane‐type organotin chalcogenide clusters. While the previously stated precondition of the materials to be amorphous was substantiated, our new findings prompted us to re‐phrase some of our former assumptions that were made based on a much smaller cohort of compounds. Clusters of the type  (1), [(BnSn)4S6] (2), [(BnSn)4Se6] (3), [(R1Sn)4S6] (4), [(R1Sn)4Se6] (5), [(CpSn)4S6] (6), [(CpSn)4Se6] (7), [(CySn)4S6] (8), and [(CySn)4Se6] (9), see the Supporting Information.For the synthesis and characterization of BnSnClλ=1.54056 Å) X‐ray source. Samples were measured in transmission between two layers of Scotch Tape (3M).Powder X‐ray diffraction patterns were measured on a StadiMP diffractometer by Stoe equipped with a Mythen 1 K silicon strip detector and a Cu‐Kα (Kα radiation (λ=1.54186 Å) at 100 K. Reflection data were processed with X‐Area 1.77.F 2 using SHELXThttps://www.ccdc.cam.ac.uk/services/structures?id=doi:10.1002/anie.201909981 (3) contain the supplementary crystallographic data for this paper. These data are provided free of charge by http://www.ccdc.cam.ac.uk/.Data for the single‐crystal X‐ray diffraction analyses were collected on a STOE STADIVARI four‐circle diffractometer using CuWhite‐light emission and SHG were performed using a confocal microscopy spectroscopy setup. For excitation, we use either 100‐fs pulses from a titan‐sapphire laser oscillator operating at a repetition rate of 78 MHz tuned to 1.56 eV for SHG experiments and a multi‐mode continuous‐wave diode laser at a photon energy of 0.855 eV for white‐light emission. A 0.5 NA Schwarzschild objective focusses and collects the light onto and from the sample, which is held in vacuum at room temperature (293 K). A lens focuses the back‐reflected light onto an either an imaging camera or the entrance slit of a quarter meter Czechy–Turner spectrometer equipped with a thermoelectrically cooled silicon deep‐depletion charge‐coupled‐device camera.The apparently different overall shape of the emission spectra in comparison with those reported in former workDensity functional theory (DFT) calculations were carried out with TURBOMOLEThe authors declare no conflict of interest.As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors.SupplementaryClick here for additional data file.