Increasing studies have suggested that dysregulation of RNA‐binding proteins (RBPs) contributes to cancer progression. Neuro‐oncological ventral antigen 1 (NOVA1) is a novel RBP and plays an important role in tumour development. However, the expression and role of NOVA1 in melanoma remain unknown. In this study, we indicated that NOVA1 expression was up‐regulated in melanoma samples and cell lines. Moreover, we demonstrated that knockdown of NOVA1 suppressed melanoma cell proliferation, migration and invasion in both A375 and A875 cell lines. In addition, we showed that suppressed expression of NOVA1 enhanced forkhead box O3a (FOXO3a) expression while inhibited AKT expression in melanoma cell. Furthermore, we demonstrated that inhibited expression of FoxO3A rescued NOVA1‐mediated cell proliferation, migration and invasion in melanoma cell line A375. These results suggested that NOVA1 acted as an oncogene in the development of melanoma partly through regulating FoxO3A expression. Then, we investigated the role of NOVA1 in melanoma cell. Furthermore, we explored the potential mechanism of NOVA1 in melanoma.22.1Melanoma tissues and the normal adjacent samples were collected in our hospital. These samples were cut into two copies: One was fixed with the formalin for histopathological confirming, and the other was stored in liquid nitrogen. All patients provided written consent for this research experiment. Our study was approved by the Ethics Committee of Peking Union Medical College Hospital. The detailed clinical information was shown as follows: case 1: T3, ulceration, foot; case 2: T3, no ulceration, hand; case 3: T3, ulceration, foot.2.2Tissues were fixed with the 4% paraformaldehyde and then washed with ddH2O and PBS. Next, H2O2 (3%) was added and incubated at RT for a half‐hour and the tissue was washed with PBS for three times. Then, the tissue was incubated with 0.3% Triton X‐100 for 30 minutes, followed by incubation in 12% normal goat serum. The slides were incubated with anti‐NOVA1 primary antibodies  and then incubated with biotin‐conjugated goat anti‐rabbit IgG. The slide was dehydrated and mounted, and figure was captured by microscopy.2.3http://www.cellresource.cn/cellsearch.aspx) . These cell lines were cultured in the Dulbecco's modified Eagle's medium (DMEM) supplemented with FBS  and penicillin and streptomycin and were kept at 37°C in the humidified atmosphere (5% CO2). Cells were transfected with the siRNA‐NOVA1 and siRNA‐control; siRNA‐forkhead box O3a (FOXO3a) and siRNA‐control plasmid using Lipofectamine 2000  according to the instruction.Human melanoma cell lines  and normal melanocyte cell line (D78) were collected from Cell bank Center of Institute of Chinese Academy of Medical Sciences and Peking Union Medical College . cDNA was carried out by the M‐MLV reverse transcriptase  from 1 ug total RNA, and qRT‐PCR was performed to determine the expression of NOVA1 and GAPDH using SYBR Green Kit (Qiagen) on the iQ5 Real‐Time PCR assat System  following the manufacturer's instructions. GAPDG was selected as the internal control. The mRNA expression was detected using 22.5Protein lysates from cells or tissues were prepared using the RIPA kit  following the manufacturer's instruction. The protein concentration was measured by BCA protein kit. Protein was separated by 12% SDS‐PAGE and transferred to PVDF membrane. After blocking with non‐fat milk, the membrane was immunoblotted with primary antibodies  overnight. After washing for three times, the membrane was incubated with HRP‐linked secondary antibodies for 1 hour. The signal was measured by enhanced chemiluminescence (ECL) . GAPDH was used as the internal control.2.65 cells) were cultured on the 96‐well plate, and cell proliferation was measured at 0, 1, 2 and 3 days. The number of cells was determined by measurement of OD at 450 nm using microplate reader (TECAN). Scratch wound‐healing assay was used to measure cell migration. When cells were grown to confluence on the 12‐well plate, scratch wound was created using 200 μL pipette tip. Cells were cultured in serum‐free medium; picture was taken at 0, 48 and 60 hours. For cell invasion assay, transwell was used. Cells were seeded on the top side of transwell chamber coated with Matrigel in serum‐free medium; medium with 10% serum was added in the lower chamber. The invaded cells on the lower membrane were washed and stained with crystal violet.Cell growth was monitored using a Cell Counting Kit‐8  following the manufacturer's information. Cells , and statistical assay was performed using the SPSS 19.0 . Student's 33.1Firstly, we measured the expression of NOVA1 in three patients with melanoma and two cases of cutaneous nevus using immunostaining analysis. Our result showed that the expression of NOVA1 in melanoma was overexpressed in all three patients with melanoma compared to that in two cases of cutaneous nevus Figure A. In lin3.2To explore the functions of FoxO3a in melanoma progression, siRNA‐NOVA1 was transfected into melanoma cell lines (A375 and A875). As shown in Figure 3.3Furthermore, we demonstrated that suppressed expression of NOVA1 inhibited A875 cell migration using wound‐healing assay Figure A, and th3.4Next, we studied the mechanism of NOVA1 in melanoma. We showed that knockdown of NOVA1 enhanced FoxO3A expression in melanoma A375 cell (Figure 3.5To study the role of FoxO3A in NOVA1‐regulated melanoma cell proliferation, migration and invasion, A375 was treated with siRNA‐FoxO3A. We confirmed that the expression of FoxO3A was significantly down‐regulated in the A375 cell after treated with siRNA‐FoxO3A Figure A. Moreov4We investigated the expression and functional role of NOVA1 in melanoma. Firstly, we indicated that NOVA1 expression was up‐regulated in melanoma samples and cell lines. Moreover, we demonstrated that knockdown of NOVA1 suppressed melanoma cell proliferation, migration and invasion in both A375 and A875 cells. In addition, we showed that suppressed expression of NOVA1 enhanced FoxO3A expression and suppressed AKT expression in melanoma cell line A375. Furthermore, we demonstrated that inhibited expression of FoxO3A rescued NOVA1‐mediated cell proliferation, migration and invasion in melanoma cell line A375. These results suggested that NOVA1 acted as an oncogene in the development of melanoma partly through regulating FoxO3A expression.Growing evidence has proved that RBPs play crucial roles in cell biology such as cell growth, apoptosis, migration, differentiation and invasion.Previous study showed that suppressed expression of NOVA1 enhanced FoxO3A expression and inhibited AKT expression in the pancreatic beta cell.In conclusion, we indicated that NOVA1 expression was up‐regulated in melanoma tissues and cell lines. Moreover, we demonstrated that knockdown of NOVA1 suppressed melanoma cell proliferation, migration and invasion partly through regulating FoxO3A expression. NOVA1 acts an oncological role in melanoma, and knockdown may provide a novel therapeutic target for melanoma.The authors declare no competing financial interests.


CAM4066, a specific CK2α kinase inhibitor, is anchored in the cryptic αD pocket outside the active site and inserts a “warhead” into the active site, blocking ATP binding and thereby inhibiting the kinase. Kd of 320 nM and shows significantly improved selectivity compared to other CK2α inhibitors. CAM4066 shows target engagement in several cell lines and similar potency to clinical trial candidate CX4945. Our data demonstrate that targeting a poorly conserved, cryptic pocket allows inhibition of CK2α via a novel mechanism, enabling the development of a new generation of selective CK2α inhibitors.The development of selective inhibitors of protein kinases is challenging because of the significant conservation of the ATP binding site. Here, we describe a new mechanism by which the protein kinase CK2α can be selectively inhibited using features outside the ATP site. We have identified a new binding site for small molecules on CK2α adjacent to the ATP site and behind the αD loop, termed the αD pocket. An elaborated fragment anchored in this site has been linked with a low affinity fragment binding in the ATP site, creating a novel and selective inhibitor (CAM4066) that binds CK2α with a  Despite many clinical success stories, the strong conservation of the ATP binding site across the kinase family makes it challenging to achieve selectivity.2 For example, imatinib inhibits not only its original target, Abl kinase, but eight other kinases with low nanomolar inhibitory constants.3 Therefore, inhibitors must derive selectivity from less conserved features of the kinase.4Protein kinases are key regulators of many cellular processes and are thus one of the main protein classes targeted in modern drug discovery.9 CK2α provides pro-survival and anti-apoptotic effects on the cells, and is often overexpressed in cancer cells, promoting their proliferation by multiple mechanisms such as potentiation of the Akt pathway and activation of NF-Kβ.11 Cancer cells therefore rely on CK2α's activity to survive, becoming addicted to high levels of its non-oncogenic activity. This is particularly true for cells that are challenged with chemotherapeutic agents and the most promising uses for CK2α stem from these observations. Indeed, there have been many successful studies where CK2α inhibitors have been used in combination with established drugs and synergy has been demonstrated between them.17 In several recent examples, it has been shown that CK2α inhibitors can re-sensitize cells to treatments that they have become resistant to.18 For these reasons, selective inhibition of CK2α appears to be a promising strategy for cancer therapy.19 A number of potent ATP-competitive CK2α inhibitors21 have been shown to inhibit the growth of cancer cell lines and one of these, CX4945, has progressed to phase II clinical trials ,26 a more open αD pocket can be observed, but no ligand is bound to it and no comment was made in the paper describing it. Nevertheless, the real size and potential of this pocket has only been revealed upon binding of our fragment , however, 6 was chosen as the fragment to link to 4 as it showed no inhibition of phosphorylation at 500 μM or detectable binding by ITC, but was clearly observed to bind in the crystal structure. The idea being that the binding to CK2α should not be dominated by the interaction with the conserved ATP site but instead by the interaction with the αD site. Several fragments were found that interacted with the hinge region, however, these were later found to be unsuitable for progression as the movement of Met168 (4 and 6 was investigated by the extension of 4 into the αD site with the synthesis of a series of compounds extending towards the ATP site (details to be published elsewhere) and eventually linking with 6. The structure of the resulting compound CAM4066  is positioned in the same place as CX4945 would bind , neither of which showed any inhibition at 500 μM.The s 320 nM , correspf 370 nM . This is50. At this concentration CK2α was inhibited by 75% (s.d. 19%), whereas no other kinases in the panel showed significant inhibition by CAM4066 .30 Indeed, the IC50 of CX4945 against Clk2 was reported to be 3.8 nM which is more potent than that reported against CK2α itself, in that study .30 D11 inhibits 61 other kinases by 70% or greater at 10 μM (354 kinases)31 and TF inhibits 7 other kinases by 70% or greater at 10 μM (61 kinases).32 HIPK2, HIPK3 and PIM1 are noteworthy as they are significantly inhibited by four (HIPK2-3) or 3 (PIM1) of these inhibitors,32 but show only 0% ± 4, and 3% ± 4 and –5% ± 5 inhibition, respectively, by CAM4066 at 2 μM. The off-target activities of these CK2α inhibitors are more significant when the drop-off in activity against cancer cell lines is considered. For all these inhibitors there is at least a 1000 fold reduction in activity against cell lines,32 compared to the inhibition/affinity against the isolated protein. The inhibitors are therefore being administered at concentrations higher than those that are known to cause significant inhibition of a large number of off target kinases. Thus, our initial data validates the novel strategy of targeting the newly discovered αD site. Furthermore, this data reveals the promise offered by further development of compounds targeting the αD site rather than the traditional method of targeting the ATP site.Although Clk2 itself is not included within our panel, several closely related kinases in the CMGC family are . None of these related kinases are inhibited by CAM4066. Added to this information, analysis of the crystal structure of Clk2 indicates that it is unlikely to have an αD pocket that could accommodate CAM4066, especially with the side chain of Tyr374 blocking the bottom of that site  in contr8), was used for the cellular assays, as esters are the most common form of pro-drug.34 This approach proved to be successful, and pro-CAM4066 showed good dose responses in HCT116, Jurkat and A549 cells, with a GI50 of 9, 6 and 20 μM, respectively  inhibition of the phosphorylation of AKT1 Ser129 after 24 hours. However, at later time points of 48 and 72 hours, pro-CAM4066 inhibited the phosphorylation of this targets at a similar level to CX4945 (35 It is possible that this delay in inhibition, when compared to CX4945, is because the hydrolysis of pro-CAM4066 to release the active compound CAM4066 delays the achievement of pharmacologically active concentrations within cells which delays the onset of inhibition.This compares favorably with the clinical trial compound CX4945, which shows GIo CX4945 . In contIn conclusion, we have used high concentration fragment soaks to probe the surface of CK2α leading to the identification of a cryptic pocket close to the ATP site. Fragments that bound in this cryptic pocket were linked successfully to a low affinity fragment in the ATP site. This quickly and efficiently generated a potent and highly selective inhibitor of CK2α, and validated the use of this cryptic pocket for the further development of CK2α inhibitors. Most significantly, we have fulfilled our initial aim and shown that it is possible to achieve higher levels of selectivity towards CK2α than previously reported for any inhibitor by interacting with features outside the active site. This can be rationalized by the low level of conservation around the αD pocket in kinases, compared to significantly higher similarity seen in the ATP site. The strategy of using such cryptic pockets outside of the active site to gain selectivity for inhibitors could be applied to other protein classes where selectivity is hard to achieve because of the high level of sequence conservation in the active site. This strategy could also be used to target orthologous proteins from pathogenic organisms to gain selectivity over host proteins.


In this work, we demonstrate the potential of simple rotaxanes as metal‐ion‐responsive ligand scaffolds through the development of a proof‐of‐concept selective sensor for Zn Mechanically interlocked molecules,2+. Herein, we report not only that is this approach successful, but that relatively small structural changes in the axle component lead to large changes in the photophysical response to divalent metal ions.Given that the synthesis of mechanically chelating ligands is now relatively simple, it is perhaps surprising that these scaffolds have been overlooked in the development of cation sensors, particularly since a related strategy for the sensing of anions has been developed by Beer and co‐workers.43 and acetylene 2 in the presence of readily available bipyridine macrocycle 14]PF6. Addition of one equivalent of Zn(ClO4)2⋅6 H2O to a solution of 4 in CD3CN resulted in large changes in the 1H NMR spectrum , which is consistent with the binding of the metal ion into the cavity of the macrocycle, confirming that 4 is capable of acting as a ligand. The behavior of rotaxane 4 as a metal‐responsive sensor for Zn2+ was investigated by fluorescence titration with Zn(ClO4)2⋅6 H2O. Portion‐wise addition of Zn2+ to rotaxane 4 in MeCN led to monotonic quenching of the emission at 560 nm2+ revealed no change by UV/Vis or fluorescence spectroscopy .We synthesized rotaxane 4 is a candidate “switch off” fluorescent sensor for Zn2+. However, examination of the selectivity of this response revealed a complete lack of discrimination between Zn2+ and selected divalent metal cations; addition of M(ClO4)2  to a solution of 4 led to quenching of the emission to a greater or lesser extent than that observed with Zn2+  confirmed that rotaxanes 5–7 act as ligands for Zn2+, and UV/Vis titration revealed excellent goodness of fit to a 1:1 binding isotherm; addition of Zn(ClO4)2⋅6 H2O resulted in the appearance of absorbance bands at 312 and 322 nm corresponding to the metal‐bound bipyridine moiety .Having confirmed that the binding of metal ions within the cavity of the rotaxane can, in principle, lead to an optical response, we extended our investigation to heteroatom‐substituted naphthalimide rotaxanes 7 Figure , which w5–7 to the binding of selected divalent metal ions revealed very different behavior. Similar to rotaxane 4, rotaxane 5 displays a simple switch‐off response to Zn2+ and the majority of other metal ions investigated 2⋅6 H2O to 7 in CD3CN led to broadening of the 1H NMR resonances corresponding to 7 and the appearance of a new set of resonances assigned to [Zn(7)]2+ . Once one equivalent of Zn2+ had been added , suggesting it is considerably shielded relative to the non‐interlocked axle, while Hk and Hl shift to higher ppm, suggesting that the shielding C−H⋅⋅⋅π interactions are interrupted.Portion‐wise addition of Zn(ClO7)](OTf)2 obtained by slow evaporation of a MeCN solution confirms coordination of Zn2+ within the macrocycle cavity and exhibits a number of features consistent with the solution‐state 1H NMR data. The Zn2+ ion is coordinated by the bipyridine and triazole N‐donors, alongside one of the aliphatic ether O‐donors and a water molecule.k and Hl are also interrupted. Interestingly, in the solid state, coordination leads to the appearance of a C−H⋅⋅⋅π interaction between one of the aromatic phenyl ring protons and the naphthalene rings and a large change in the dihedral angle about the S‐naphthyl bond. With the obvious caveat that the solid‐state structure of [Zn(7)]2+ is not necessarily representative of the solution‐state (co)conformation, the observed changes in the interactions between the macrocycle and fluorophore component, along with the changes in the conjugation between the S‐donor and the naphthalene core and the altered dihedral angle, suggest that the changes in emission properties of 7 on metal binding may be due to changes in the (co)conformation of the ensemble.The solid‐state structure of 2+ is observed to form selectively , whereas the same experiment with macrocycle 1 produced a 4:1 mixture of Zn2+ and Cd2+ complexes . These results demonstrate that the mechanical bond imparts a significant degree of selectivity to the binding of otherwise similar metal ions, perhaps due to the different sizes of the Zn2+ and Cd2+ ions The binding of rotaxane 2+ compared with Cd2+ allowed us to use a more competitive solvent mixture (2 % water in MeCN) to impart selectivity to sensor 7. In the presence of H2O . As a result, whereas 1 equiv of Zn2+ achieved 50 % of Fmax and saturation was achieved at approximately 12 equiv, Cd2+ required around 20 equiv to achieve 50 % switch on and around 100 equiv to achieve saturation, demonstrating that under these conditions, Cd2+ is not bound by 7 to a significant extent. Thus, whereas addition of 5 equivalents of Cd2+ to 7 in MeCN/H2O leads to a weak response, when Zn2+ is added to the same solution, the expected switching on of luminescence is observed, thus demonstrating selectivity for Zn2+ over Cd2+  should be addressed to the authors.SupplementaryClick here for additional data file.


Q ≈ 1210) from patterned lead halide perovskite microplatelets fabricated in periodic arrays on silicon substrate with micropatterned BN film as the buffer layer. By varying the size of the platelets, modal selectivity for single mode lasing can be achieved with different cavity sizes or by simply breaking the structural symmetry of the cavity through designing the pattern. Importantly, this work demonstrates a straightforward, versatile bottom‐up scalable strategy to realize high‐quality periodic perovskite arrays with variable cavity sizes for large‐area light‐emitting and optical gain applications.Organic–inorganic metal halide perovskites have recently demonstrated outstanding efficiencies in photovoltaics as well as highly promising performances for a wide range of optoelectronic applications such as lasing, light emission, optical detectors, and even for radiation detection. Key to the realization of functional perovskite micro/nanosystems on the ubiquitous silicon optoelectronics platform is through sophisticated lithography. Despite the rapid progress made in halide perovskite lasing, direct lithographic patterning of perovskite films to form optical cavities on conventional substrates remains extremely challenging. This study realizes room‐temperature high‐quality factor whispering‐gallery‐mode lasing ( Furthermore, mode selection, which is an important issue for the application of such microstructured coherent light sources, was also demonstrated. By changing the size of cavity or by breaking the symmetry of the cavity with the patterning approaches, wavelength tunable, single mode lasers were realized. This patterning approach provides greater versatility over the control of the lasing mode and its wavelength through judicious design of the perovskite cavity. Our work suggest a viable, scalable lithography approach to fabricating high‐quality periodic light emitting arrays for potential applications as integrated coherent light sources and other large‐area optoelectronic applications.In this work, we utilized a novel bottom‐up growth technology for the synthesis high quality patterned perovskite arrays on Si with varying cavity sizes for light emission and lasing, enabled by pre‐patterned single layer hexagonal boron nitride (h‐BN) buffer layer. The atomically thin crystalline, single layer h‐BN materials2Figure2/Si substrates using a standard transfer method. After that, the large‐area BN film  was patterned using standard photo‐lithography methods. The epitaxial growth of highly crystalline PbI2 platelets on these BN substrates are performed via a physical vapor deposition (PVD) process. The PbI2 crystals were then converted into CH3NH3PbI3 by reacting with CH3NH3I under vacuum. There are two key points in the growth of perovskite/BN vdW solids: nucleation site and van der Waals epitaxy. PbI2 nanoparticles first nucleated around the edges and defects of 2D materials. These nanoparticles then grew along surface of 2D materials and began to merge to form highly crystalline nanoplatelets. Lastly, the PbI2 nanoplatelets extended on BN material surface and covered all the area. Figure 2 to CH3NH3PbI3, we first investigate the X‐ray diffraction (XRD) patterns of the arrays before and after conversion. Before conversion, a set of strong peaks at 12.54°, 25.34°, 38.50°, and 52.24° , (220), (310), and (330) for pure CH3NH3PbI3 crystals, respectively.2 and CH3NH3PbI3 possess almost the same Raman spectra , high‐resolution transmission electron microscope (HRTEM) imaging and energy dispersive X‐ray spectroscopy (EDX). Figure3NH3PbI3 is evaluated by HRTEM imaging, as shown in Figure In order to validate the complete conversion of PbI4° Figure2a,37 wFigure−2), the emission spectrum is broad and the intensity is low. With increasing pump fluence (≈9.0 μJ cm−2), the emission peak broadens due to band filling effect and increases in intensity.−2 (per pulse), a series of sharp peaks is observed at the shoulder of the main peak, which is amplified due to the optical feedback in the WGM cavity. At the pump fluence of ≈11 μJ cm−2, the intensity of the sharp peaks increase sharply, which is a signature of lasing behavior. Figure L–L' curve) with a characteristic ‘knee’ or ‘kink’ is observed in the L–L curve and an abrupt shortening  of the full width half maximum (FWHM) of the platelet emission above the threshold pump fluence of ≈11 μJ cm−2. The solid line is fitted by using a multi‐mode lasing model described in a previous report  with a large expansion in the c axis. Moreover, PbI2 has a bandgap of ≈2.4 eV and the bandgap for perovksite is ≈1.6 eV after conversion. The perovskite crystals also show superior optical properties, owing to the lower threshold, higher Q factor and near infrared working wavelength range.Figure L increases from 8.3, 13.1, 16.8 to 19.6 μm (thickness of ≈200 ± 10 nm), the highest optical gain area where lasing can be realized, redshift to the lower energy region  should scale proportionally to the inverse length 1/L. This behavior is illustrated in Figure λ and 1/L, suggests WGM mode lasing in these perovskite platelet cavities.For the perovskite platelet with a different size, the lasing modes can be tuned due to the intrinsic self‐absorption in the perovskite cavity. We first fabricated perovskite platelet arrays with platelets of a different size using the above mentioned method. As the edge length on Figure5a–d. Tβ) of an individual platelet laser of different sizes, circularly polarized pump excitations were used for the measurements in the light–light (L–L) plots shown in Figure x0. A higher value of x0 corresponds to a smaller mode area and a higher β factor. With increasing platelet size from 8.3, 13.1, 16.8 to 19.6 μm, the value of x0 increases from 0.02, 0.08, 0.2 to 0.3; while the corresponding lasing threshold decreases from 12.8, 10.8, 10.0 to 9.0 μJ cm−2. It is possible that the size dependent lasing threshold may be due to the different trap densities in different sized platelets, which influences the charge carrier dynamics. Although such mechanism was proposed in some early works,Q = λ/Δλ, the Q factor was estimated to be ≈1200. This suggests that there is more coupling of the spontaneous emission into the lasing modes with lower losses in the bigger samples. This behavior is consistent with previous descriptions that the lasing threshold power density (Pthr) is inversely proportional to the β × Q product,β and Q factors would mean a lower threshold.To estimate the lasing thresholds and spontaneous emission coupling factor  BN film was covered by a photoresist layer spin‐coated  on top of the h‐BN surface; (2) standard photolithography was performed to pattern the photoresist layer as a mask; (3) argon‐based plasma etching  was performed to transfer the photoresist mask pattern onto underlying h‐BN; (4) photoresist mask was completely removed in acetone, and a BN pattern was created, such as the hexagonal and wire patterns shown in the main and supporting text.2 PlateletsSynthesis of PbI: PbI2 powder  was used as a single source and placed into a quartz tube mounted on a single‐zone furnace (Lindberg/Blue MTF55035C‐1). The BN pattern substrate (1 × 3 cm2) was placed in the downstream region inside the quartz tube. The quartz tube was first evacuated to a base pressure of 3 mTorr, followed by a 50 sccm flow of high‐purity Ar gas. The temperature and pressure inside the quartz tube were set and stabilized to desired values for each halide (390 °C and 30 Torr). In all cases, the synthesis was carried out within 30 min and the furnace was allowed to cool down naturally to ambient temperature.3NH3ISynthesis of CH: The synthesis of CH3NH3I: 18.0 mL of methylamine  was dissolved in 100 mL of absolute ethanol  in a 250 mL round bottom flask. 20.0 mL of hydroiodic acid  was added into the solution dropwise. After that, the solution was stirred at 0 °C for 2 h. The raw product was obtained by removing the solvents using a rotary evaporator. A recrystallization process of the raw product, including the re‐dissolution in 80 mL absolute ethanol and the precipitation after the addition of 300 mL diethyl ether, was carried out twice to obtain a much purer product. Finally, the white powders were collected and dried at 60 °C for 24 h in a vacuum oven.3NH3I and PbI2Synthesis of Perovskites via the Reaction with CH: The conversions were done using a similar CVD system. CH3NH3I were used as a source and placed in the center of the quartz tube while CVD BN substrate having as‐grown lead halide platelets were placed around 5–6 cm away from the center in the downstream region. The quartz tube was first evacuated to a base pressure of 3 mTorr, followed by a 50 sccm flow of high‐purity Ar gas. The pressure was then stabilized to 30 Torr and the temperature was elevated to 120 °C and kept there for 1 h after which the furnace was allowed to cool down naturally to ambient temperature.Photoluminescence and Lasing Measurements: A frequency‐doubled, mode‐locked Ti‐sapphire regenerative amplifier laser  was used to pump the photonic lasers . An objective lens  was used to focus the pump beam to a 40 μm diameter spot on the sample. All experiments were carried out at room temperature. Individual spectra were recorded using a spectrometer with a resolution of 0.30 nm and an electrically cooled charge coupled device (CCD) (Princeton Instruments).Time‐Resolved Photoluminescence Measurement: The lifetime measurements were conducted under very low pump conditions to avoid sample heating and multiparticle scattering effects using a streak camera (Optronics GmbH); the laser source used here was a frequency‐doubled mode‐lock Ti‐sapphire oscillator laser . A 425 nm long pass filter was used to filter out laser source from the PL emission.XRD, SEM, AFM, TEM, PL, and Raman Measurements: X‐ray diffraction pattern (2θ scans) were obtained from perovskite platelet supported on the SiO2/Si substrates using an X‐ray diffractometer (XRD Shimadzu Thin Film), using Cu‐Kα radiation (λ = 1.54050 Å) within a diffraction angle (2θ) from 5° to 60°. The SEM images of perovskite platelet were obtained using JEOL JEM7600F operated at an accelerating voltage of 10 kV. For all the AFM, experiments were performed in tapping mode under ambient conditions . Commercial silicon tips with a nominal spring constant of 40 N m−1 and resonant frequency of 300 kHz were used in all the experiments. The PbI2 samples for TEM were flaked off from the 2D substrates by using Toluene  and then transfer onto the TEM grids (Quantifoil Mo grids). The CH3NH3PbI3 perovskite samples for TEM measurement were converted from the PbI2 onto the TEM grids, with the similar method introduced in the materials synthesis part above. The HRTEM and the SAED pattern were done with an FEI Tecnai F20 operated with an acceleration voltage of 200 kV. The chemical composition of lead iodide and CH3NH3PbI3 perovskite was determined by means of EDX (attached to FEI Tecnai F20). A WITec alpha300 RAS Raman system with a piezocrystal controlled scanning stage, an objective lens of 100× magnification , and an electron multiplying CCD was used for recording PL and Raman spectra/images. For PL spectra/images, a 600 lines mm−1 grating was used. For Raman spectra/images, a low‐wavenumber coupler and a 2400 lines mm−1 grating were used for observing low‐frequency Raman modes and achieving a good spectral resolution. All the PL and Raman spectra/images were recorded under an excitation laser of 532 nm (Elaser = 2.33 eV). To avoid the laser‐induced heating, laser power was kept below 0.1 mW. The laser spot was of ≈0.5 μm in diameter. The fluorescence image was obtained by an Olympus fluorescence microscope under green excitation of 530–550 nm with a mercury lamp as the excitation light source. UV–vis absorption spectra of perovskite prepared on quartz were recorded on SHIMADZU UV‐3101PC UV–vis–NIR scanning spectrophotometer.Simulation Details: Simulations of lasing mode distributions were first performed in 1D (z‐direction) using the eigenmode method , and the simulated effective mode index was used to obtain the 2D (x and y directions) mode distributions using the finite‐difference time‐domain (FDTD) method . The refractive index of perovskite was obtained from previous references.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.


Weekly observation of ammonium over a twelve-year period revealed high concentrations and suggests impairment of water quality, particularly since 2011. The estimated total dissolved nitrogen flux was 7.2 times higher in middle reaches than that at head waters. Anthropogenic nitrogen sources become more important in lower section of the upper reaches and middle reaches because of intensive agricultural activities and urban input. Nitrate in the lower reaches was mainly derived from transportation of upstream nitrate and point sources from cities. The spatial variation of ammonium and nitrate isotopes show that nitrification is a key process governing nitrogen transformation. Riverine biological processes could potentially be responsible for the shift of nitrate isotope signature. The first step to reducing nitrogen load and improving water quality will be containment and careful management of sources from urban input, sewage waste and irrigation runoff.A heavy load of nitrogenous compounds reflects nutrient loss and influences water quality in large rivers. Nitrogenous concentrations and dual isotopes of nitrate were measured to ascertain the spatial and temporal distributions of nitrate transformation in the Yellow River, the second-longest river in China. Assessment of the long-term record indicates that [NO Long-term monitoring is crucial to understanding nitrogen (N) dynamics and transformation in rivers. Over the past 50 years, the nitrogen load in watersheds has been heavily impacted by urbanization and land-use practices associated with intensification of agriculture and animal farming4. N export to the sea by large rivers has increased significantly during the past five decades, with up to a six-fold increase in N fluxes caused by human activity observed in the United States6.Elevated concentrations of nitrogenous compounds in riverine environments is well demonstrated as having detrimental consequences for human and ecosystem health7. The nitrogen cycle in riverine systems involves several transformations, primarily nitrification, denitrification and biological uptake8. Elucidation of the sources of nitrogen and riverine transformations that most influence N export is essential for understanding the sustainability of freshwater systems and environmental changes on the Earth’s surface8. Paired stable nitrogen and oxygen isotopes are a powerful tool that is highly suitable for this research objective13.Nitrate and ammonium are the two dominant forms of reactive N entering the aquatic environment. The major sources of nitrate are atmospheric deposition, chemical fertilizers, soil organic nitrogen (SON), manure, and sewage effluents5 km2 and an annual average discharge of 5.8 × 1011 m3 and so is a significant drainage system globally. The Yellow River provides 140 million people with drinking and irrigation water in regions where the water supply per person is less than one third of the national average and water quality has suffered greatly from pollution14. Few long-term studies of riverine nitrogen in the YR have been conducted, and even fewer studies have used the dual isotopes of nitrate to identify its sources and behaviors20. In this study, samples representing the whole watershed were collected across the wet and dry seasons  is the second longest rivers in China, with drainage area of 7.95 × 10−1  in the main channel (in future referred to as mainstream) during the high flow season  . The [TDN] in tributaries ranged from 0.54 to 12.0 mg·L−1 with a mean value of 4.3 ± 3.6 mg·L−1 (n = 13) during the high flow season  in the low flow season.The concentration of total dissolved nitrogen ([TDN]) ranged from 0.53 to 4.1 mg·Ln Figure , which in Figure , and 7.03−–N] from main stream in the high flow season were generally lower than that in the low flow season  in China during the high flow season21. All mainstream samples exhibited [NH4+–N], dissolved organic nitrogen concentration ([DON]) and [NO2−–N] of less than 0.5 mg·L−1  during both flow seasons, and the highest [DON] was observed at T9 during the low flow season  during the high flow season  during the high flow season. Almost all samples had higher [Cl−] in the low flow season than that in the high flow season  was lower than that at the other two sites  . The [TDN] at site M23 ranged from 3.0 to 5.6 mg·L−1 . Furthermore, up to 80% of the samples at M17 and M23, and 54% of samples at M1 have a [NO3−–N]/[TDN] ratio of greater than 80%, indicating that nitrate represented a substantial proportion of the TDN. The [NO3−–N] at the M17 and M23 sites was three to four times higher than that at M1 sites. Three samples at M17 had [NO2−–N] of greater than 0.30 mg·L−1 during the low flow season. The [TDN] also exhibited temporal variation from 2012 to 2014, with higher concentrations observed during the low flow season at all three sites. The [NO3−–N] was higher during the dry seasons (from November to April) than in the wet season because of reduction in water fluxes and a relatively high load of nitrogen from anthropogenic inputs  Figure . The  or dissolved inorganic nitrogen concentration ([DIN]) has increased over the past thirty years. For example, the average [NO3−–N] at Luokou station (M23) had increased from 1.94 mg·L−1 (n = 24) in the 1980s to 3.4 ± 0.7 mg·L−1 (n = 19) during 2012 to 2014, which indicates that the [NO3−–N] has increased by approximately two-fold during the past thirty years. High [NO3−–N] was also found in the Yellow River during the low flow season in 2011  in the middle and lower reaches of the YR in recent years. Although an increasing trend in [NO3−–N] is observed over the past three decades, [NO3−–N] during the period 2012 to 2014 was lower than the average [NO3−–N] during 1989 to 2000.As illustrated in Fig. 4+–N] during the period 2004–2015 at nine stations. Significant spatial and temporal variation is observed in the long-term monitoring data. The lowest [NH4+–N] in the water sample was found at M3 station located in the upper reaches among all nine monitoring sites. A gradual increase occurs from station M3 to station M5, and a three-fold increase is observed between stations M5 and M6. In the middle reaches, [NH4+–N] decreased between stations M7 and M16.Figure 4+–N] in two major tributaries ranged from 0.19 to 60.7 mg·L−1 at T9 and from 0.14 to 17.6 mg·L−1 at T12, with mean values of 14.4 mg·L−1 and 3.71 mg·L−1, respectively, which are quite high concentrations for surface water. The values of [NH4+–N] at T9 and T12 are higher than that of the other stations located in the mainstream  during the low flow season and from 0.1‰ to 12.2‰ with a mean value of 6.9 ± 2.1‰ (n = 39) during the high flow season, respectively. The δ15Nnitrate values were higher during the low flow season than those during the high flow season . Tributary samples have lower average δ15N values  than mainstream samples  during the high flow season. Samples from the middle reaches had a higher average δ15Nnitrate value  than that in the upper reaches  and lower reaches  during the high flow season. However, the average δ15Nnitrate value of samples in the middle reaches was lower than that in the lower reaches (7.8 ± 0.5‰ compared to 8.7 ± 0.5‰) during the low flow season , and from −3.0‰ to 1.9‰ for δ18Onitrate, with an average value of −0.8 ± 1.2‰ (n = 25). The δ15Nnitrate values varied from 6.0‰ to 11.1‰ in the samples at M17 and from 7.5‰ to 11.1‰ in the samples at M23 (n = 19), showing a wider nitrogen isotope range relative to that of the samples at M1. The δ18Onitrate values ranged from −1.3‰ to 3.3‰ at M17 and −0.5‰ to 4.2‰ at M23  and three mainstream samples (M1–M3) in the upper reaches (UR), with low population density (9.5 person/km2)28, had relative low [Cl−] and [NO3−–N] for these five sites, which amounted to one third of those from other mainstream sites. This result suggests minimal contamination from human activities in this section of the YR. The degree of influence of industrial and agricultural activities on water quality gradually increased after site M3, such as the polluted tributaries of T3 and T4. A heavy load of Cl− and NO3−–N in river water samples was also detected in the tributaries of the middle reaches (TMR). Ningxia Plain and Hetao Plain are important agricultural districts, where YR water is diverted for irrigation of farmland by a drainage network  constitute 28% of the entire drainage area of the YR, contributing more than 56% of discharge3−–N] was observed between two water conservancy projects, Sanmen Valley Reservoir (near M14) and Xiaolangdi Reservoir (near M15), where water is retained for prolonged periods  and developed economy28, [NO3−–N] showed only a slight increase from 2.9 to 3.5 mg·L−1 between sites M19 and M26, which may be related to the small number of tributaries entering the main body of the YR. The primary inputs in this section are point sources from industry and domestic waste in city and urban areas.The concentration of nitrogen increased between M12 and M13, following the input of two major tributaries  and indicating high nitrogen concentrations in these tributaries. A significant decrease in  and δ15N values during the low flow season than that during the high flow season, indicating that manure and sewage waste were the major source instead of nitrogen from agriculture. The high DON and nitrate isotopic composition  of the water samples collected from other tributaries showed that manure and sewage waste were major contributors to riverine nitrate during this period.The riverine nitrate in the Yellow River might be impacted by various factors in different zone due to sparse distribution of dual isotopic characteristics Fig. . The riv28. Therefore, SON might be a more important nitrate source. Nitrate concentration increased slightly during the low flow season, when the level of microbial activity is lower due to low temperature conditions, and the average nitrate concentration (0.75 ± 0.19 mg·L−1) suggests the presence of other nitrogen sources with high nitrogen concentrations and similar δ15N values (4.9 to 7.3‰). Animal manure produced by free grazing of livestock in this region may be responsible for the variation in nitrate concentrations. Therefore, nitrate in the upper reaches (M1) is mainly derived from mineralization of SON and animal manure. The increased [NH4+–N] at long-term monitoring sites located in the lower section of the upper reaches (M3–M9), suggests an anthropogenic source of N, such as nearby urban areas. Although fertilizer application and precipitation are limited during the low flow season, flood irrigation would allow nitrogenous fertilizers to infiltrate the groundwater, resulting in nutrient discharge into rivers36. Therefore, sewage waste and chemical fertilizer may be responsible for the high [NH4+–N]. Riverine nitrate in the middle reaches exhibited a wider range in δ15N than that in the upper and lower reaches, which suggests that multiple nitrogen sources contribute to the middle reaches across different seasons. The distribution of nitrate isotope values in the middle reaches indicates that nitrate sourced in the upper reaches of the YR and the tributaries located in the middle reaches are impacted by multiple sources, including chemical fertilizers, SON, manure and sewage waste. The higher isotope values of nitrate at M17 and M23 than at M1 indicate the addition of further sources between these sites that are enriched in15N, such as manure and sewage waste, or that riverine nitrate is affected by isotopic fractionation by denitrification. The [NO3−–N] is higher in the lower reaches, but the isotopic values showed no significant change, indicating similar sources to those encountered in the middle reaches.The small monthly variation of dual isotopes M1, Fig.  suggestsOverall, it can be concluded that the tributaries in the middle reaches were polluted by manure or sewage waste and this dominated the nitrate pool. Nitrate in samples from the upper reaches would be from SON, while agricultural sources, chemical fertilizer and manure waste dominate in the lower section of the upper reaches. The middle reaches are influenced by multiple sources and may be affected by the significant variations observed in tributaries during high flow season. The concentration of nitrogen and difference in isotopic signature of nitrate indicates that manure and sewage waste was a larger contributor to the Yellow River Basin during the low flow season.15N of the substrate, unless the reactions go to completion7, such as ammonia losses from organic matter within manure, which may result in δ15N values higher than 25‰27. The middle and lower reaches of the basin drained a greater area of agricultural land and were subject to fertilizer application during the high flow season. In theory, the nitrogen isotope values during this season may have low values close to 0‰. However, the measured compositions were greater than the theoretical values, which indicates that volatilisation may occur and enrich the heavy isotopes. Xing and Zhu (2002) reported that the loss of N through volatilization of urea was 22% in agricultural land based on mass budget37. The volatilization process follows the Rayleigh distillation equation with an overall fractionation effect of approximately −20‰38. Based on the conversion factors, the Rayleigh fractionation equation, and δ15N values of nitrogenous fertilizers collected within the basin, the δ15N of the residual fertilizer nitrate would be 4.6‰, which is close to that observed in tributary samples from the middle reaches.The main processes that control nitrogen dynamics in ecosystems commonly result in an increase in the δ18Onitrate values higher than the theoretical δ18Onitrate value (2.8‰), indicating that nitrification was the major transformation in the nitrogen cycle. Additionally, the long-term observation of ammonium showed high concentration in the low flow season and low concentrations during the high flow season with warm temperature, indicating that nitrification was the dominant process controlling the temporal variation of ammonium. Meanwhile, the increasing trends of oxygen isotopic values in water and oxygen isotopic values of nitrate along the flow path suggest nitrification played an important role in production of nitrate31.Nitrification is a multi-step oxidation process mediated by several different autotrophic organisms. Several samples showed δ39. The decreased concentration and highest dual isotopes of nitrate in the mainstream of the Xiaolangdi water conservancy project , particularly for samples collected in the high flow season . The decreased nitrate concentration and increased δ18Onitrate value at M1 and M17 sites during the high flow season  is discharged into the river from the Loess Plateau located in the middle reaches which constitutes 92% of riverine silts, making it the most sediment-laden river in the world and the spectacle after which it is named14. The riverbed in the lower reaches is elevated above the ground surface by more than 10m in some areas, due to the building of levee banks to combat flooding accompanied by continuous sediment deposition due to the extremely high sediment transport from the middle reaches. The abundant hydrodynamic resources distributed in the middle reaches where the elevation of the river drops 890 m make it highly suitable for hydroelectric power generation. Two major water conservancy projects  are located in the middle reaches. The two largest tributaries (Wei River and Fen River) of the YR are in the middle reaches.The Yellow River (Huang River), located between 32°10′N–41°50′N and 95°53′E–119°10′E, is the world's fifth longest river and the second longest river in China, with a length of 5464 km. The mainstream of the YR is commonly divided into three sections, the upper reaches (M1–M9), middle reaches (M9–M18) and lower reaches (M18–M26)  and lower reaches. In the agricultural regions, synthetic fertilizers are generally applied twice a year, in July for summer crops and October for winter crops. However, manure is also applied periodically throughout the year. Three large cities, Xi’an, Zhengzhou, and Jinan, each have populations of greater than seven million people, and more than three million people live in urban areas surrounding the mainstream or major tributaries. Dry land area accounts for 80% of the basin area. The cultivated land is mainly in the middle and lower reaches, with 7.2% irrigated agricultural area. The majority of grazing land is located in the upper reaches. Grassland, cropland, wetlands, and urban areas account for 60%, 29.5%, 1.1%, and 6% respectively28.The Yellow River Basin has a continental monsoon climate and most of the basin belongs to the temperate-arid and semi-arid climatesThe seasonal water samples were collected from the mainstream of the YR and its major tributaries in August of 2010 and February of 2011, corresponding to the high and low flow seasons respectively. Water samples comprised 26 mainstream water samples (M1–M26), 13 tributary water samples (T1–T13), and 2 rain water samples during the high flow season. The upper reaches were frozen in winter, resulting in low water discharge into the mainstream. Therefore, water samples were collected from the middle and lower reaches during the low flow season, comprising 22 river samples (16 mainstream and 6 tributaries), one snow sample and one sewage sample. Additionally, three sites  were selected for monthly sampling from July 2012 to June 2014. Water samples were filtered through 0.45-µm cellulose-acetate filter paper at the field site and collected in 100mL opaque plastic bottles for nutrient and nitrate isotope analysis, and samples for isotopic analysis were refrigerated at 4°C.− and NO3−) concentrations (mg/L) were determined using a Dionex ion chromatography (IC) system 90 . The N concentrations (mg/L) of NH4+, NO2−, and TDN in the filtered samples were analyzed using an automatic flow analyzer (SKALAR Sans Plus Systems) after the field work. The nitrogen detection limit was 5 μg·L−1 for NO2−–N, 10 μg·L−1 for NO3−–N 10 μg·L−1for NH4+–N, and 20 μg·L−1 for TDN. The DON concentration was calculated by subtracting DIN  from the TDN. Denitrifer bacteria were used to transform the nitrate to nitrous oxide (N2O). Isotopic analysis of the N2O product was performed using an isotope ratio mass spectrometer after purification using Trace Gas Pre-concentrator unit45. For calibration, four international nitrate  and experimental reference materials were treated in an identical manner as the filtered water samples. The analytical precision for the samples analyzed in duplicate was 0.3‰ for δ15N and 0.5‰ for δ18O of nitrate.Anion (ClR = 15N/14N or18O/16O. The15N/14N reference was N2 in air and the18O/16O reference was Vienna standard mean ocean water.The isotope ratios are reported as delta (δ) expressed in per mil (‰) using the usual delta notation:Supplementary information


S=1/2 spin states separated by only 0.1 meV (0.8 cm−1).The first regular homometallic ring containing an odd number of metal centers is reported. The ring was synthesized by means of amine‐templated self‐assembly. Extensive physical characterization studies, including magnetic measurements, powder inelastic neutron scattering (INS), and DFT calculations, show that the molecule has a near perfect match to the expected behavior for a frustrated system with the lowest energy pair of  Since the publication in 1990 of both {Fe7V2} and a {Cr8M} family.7} ring made by Oshio and co‐workers with the vanadium sites bridged by a cyclodextrin ligand.There are a few reported heterometallic nine‐metal rings, including {Cr9} and {Ni11}, were published by Dahl and co‐workers, both of which showed considerable geometric irregularity; however, no characterization beyond crystallography was reported.9} that was not isolated but co‐crystallized with a range of other copper rings.Large regular odd‐numbered rings would show interesting physics associated with spin frustration,9F10} and {Cr9F11} (see below), each of which contained one edge with a defect breaking the regularity of the ring.2CtBu)2]91, along with characterization of the ring by magnetometry and inelastic neutron scattering (INS) to explore the extent of spin frustration.We previously reported two nonametallic rings {Cr1 is based on a procedure we previously developed for synthesizing hexametallic and heptametallic chromium horseshoes2CtBu)2]82 . Using diisopropylamine as the template along with the addition of trifluoromethanesulfonic acid leads to a mixture of octa‐ and nonametallic rings which can be purified by column chromatography, resulting in the separation of 1 and 2, along with the previously published2iPr2][Cr9F10(O2CtBu)18]  and [NH2iPr2][Cr9F11(O2CtBu)17] . The templating ammonium cation is not present in 1 but addition of diisopropylamine is essential for the compound to form.The synthesis of 1 can be grown from a range of solvents  resulting in two distinct types of crystals. Crystals with hexagonal space group P63/m show significant disorder in the pivalate carbons and only the Cr, F, and O positions can be refined with confidence. However, crystals with the orthorhombic space group Pcba can be grown from n‐propanol and the full crystal structure determined ; Figure S7) and variable‐field magnetization (M(H); Figure S8), show the expected behavior for an antiferromagnetic exchange between the CrIII centers in 1, and can be fitted to a Hamiltonian containing a single antiferromagnetic exchange parameter J=1.35(3) meV (1 meV=8.066 cm−1). These thermodynamic measurements confirm the presence of an S=1/2 ground state and support the presence of spin frustration, but they are comparatively insensitive compared with spectroscopic techniques. The size of the exchange coupling is somewhat smaller than that found in 2 which is 1.46 meV.Given the regular structure of 1 recrystallized from toluene  measured at 1.5, 7, and 15 K. The dominant peak at low temperature corresponds to the transition between the ground S=1/2 states and the lowest energy S=3/2 multiplet, labelled transition I. At higher resolution (iE=2.5 meV), a splitting of this peak of about 0.1 meV is detected . At 15 K, hot transitions can be detected due to additional excitations from the lowest energy S=3/2 state (transitions VI and VII). The seemingly temperature‐independent broad peak at 3 meV is due to an overlap of two peaks corresponding to one cold (III) and one hot transition (VIII). All these results are well reproduced by a Hamiltonian with C9 symmetry, thus demonstrating that the spin dynamics of 1 matches that expected of a perfectly frustrated antiferromagnetic ring .Inelastic neutron scattering (INS) probes the spin dynamics of the system and can directly detect any splitting of the pair of potentially degenerate ground‐state doublets. INS data were collected using the low energy transfer (LET) spectrometer on a powder sample of e Figure , top, us1 quantitatively, we performed high‐resolution  INS measurements which revealed a small (0.1 meV) splitting between the two S=1/2 ground states . Fitting the INS data resulted in parameters of J=1.32 meV (10.6 cm−1), J′=1.2⋅J=1.58 meV and d=−0.022 meV. It is worth noting that the average value of the exchange constants is the same found from magnetometry. This model reproduces the observed splitting of the peak corresponding to transition I  is in good agreement with calculations, confirming that the structure of the states involved in the transition is well reproduced by our model.In this Hamiltonian, J value of 1.40 meV is found from these calcuations, which is in very good agreement with that obtained by fitting magnetometry and INS data (1.35 meV). The distribution of the calculated couplings is much more uniform than those of the previously reported Cr9 wheels,To validate our findings, we have performed density functional theory (DFT) calculations employing the NWChem software,1 has been investigated through analysis of the scalar spin chirality C^[Eq. The internal spin structure of the ground state of y C^Eq. , which i1 is an equal superposition of chirality eigenstates with opposite eigenvalues . Thus, in contrast to the classical spin configurations , Cr9 fluctuates between nonplanar states with opposite chirality keeping C>=0, consistent with the behavior expected for an ideally frustrated antiferromagnetic ring.The results show that the quantum ground state of 1 is the first compound reported containing a regular homometallic ring containing nine metal centers. The INS data for the compound reveal nearly frustrated spin dynamics, with a slight lifting of the degeneracy of the lowest‐energy states resulting in a splitting of the two S=1/2 multiplets of only 0.1 meV. Compared to systems such as triangles where highly rigid ligand systems are required to ensure spin frustration,1, further studies of the spin properties, such as spin density or correlation dynamics, will provide fascinating information on the physics of such large frustrated spin systems.Compound 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.


The observed static water contact angles of ZnO NRs samples were 103° ± 3°, 152° ± 4°,161° ± 3°, 164° ± 2°, 167° ± 2°,154 ± 3° and 151° ± 2° for the pristine, ion fluencies of 1E11, 3E11, 5E11, 7E11, 1E12 and 3E12 ions cm−2, respectively. The change in local surface chemistry via formation of surface oxygen related defects due to electronic excitations induced by ion irradiation determine the water dewetting properties. It is found that surface oxygen related defects could be tuned by varying the fluence of the SHIs. Durability tests show that the SHI induced surface oxygen-deficient ZnO NRs have the stable superhydrophobic behavior for more than a year.Tailoring the surface properties by varying the chemistry and roughness could be of interest for self-cleaning applications. We demonstrate the transformation of hydrophobic ZnO Nano rod (NR) array into superhydrophobic nature by changing the local chemical state and without altering the surface roughness by swift heavy ion (SHI) irradiation. The aligned ZnO NR arrays were irradiated using 150 MeV Ag ions with different fluences from 5E10 to 3E12 ions/cm The wetting properties of the surface could be altered by varying the surface roughness and surface energy by chemical functionalisation7. To date, water repellent surfaces are engineered with chemical functionalising to reduce the surface energy. The change in wettability of the surface by adding another chemical is not desirable in most of cases especially in bio-interaction platforms as the interaction of biomolecules and surface functionalised chemical groups could create additional complexity11. Therefore, methods that could alter the surface energy by inducing intrinsic local surface alterations are interesting. Among the metal oxide family, surface wetting (hydrophilic or superhydrophobic) controlled ZnO, play a crucial role in nanoscale chemical sensing, biosensing, biomedical and microfluidic applications due to its stable and tuneable chemical and physical properties14. Previous investigations reveal that under UV radiation ZnO based platforms turn hydrophilic and improved the adsorption of proteins16. Modifying the wetting nature of ZnO nanorods (NRs) can lead to more surface interactions and, hence increased sensitivity of the sensor platform. But fabricating superhydrophobic and superhydrophilic ZnO NR based platforms without any chemical coating is essential for better performance of smart nanodevices. In this work, we demonstrate the wetting properties of ZnO NRs array that could be tailored by varying the surface energy by ion beam induced intrinsic local surface alterations.Functional materials with artificial intelligent surface with tuned and robust wetting properties such as superhydrophobicity/hydrophilicity, have been an emerging field with enormous application potential in automobile industries, display panels, medical devices, sensing platforms and other optical equipments17. On the other hand, in high energy range (MeV/amu regime), ions interact with the atomic electrons of the target material. The high energy heavy ions having energies in regime of ~MeV/u or higher are referred as swift heavy ions (SHI). The SHI transfer energy by inelastic collisions with target atomic electrons resulting in excitation of the electrons and ionization of the target atoms. The SHI generates highly energetic electron gas around their irradiation tracks. These highly energetic electrons are capable of exciting the nearby atoms and thus locally alter the chemical state of the target material.Surface modifications such as (i) surface roughness and (ii) surface energy variation through ion beam irradiation without any external chemical functionality are potentially important in the field of materials science. The modification of material properties depends on the ion beam parameters such as mass of the ion, energy of the ion and fluence. Low energy ions (keV/amu regime) losses energy by elastic collisions with nuclei of the target material. The elastic collisions cause surface diffusion of target nuclei and influence the surface morphology resulting in formation of ripple like surface structures or increase the surface roughness of the materials20. Tashlykova et al., reported that irradiation of Xe+ ion on graphite surface cause variation of surface roughness which changes its wettable properties21. Mostly ion irradiated polymers show change in surface roughness which resulted in modification of their wetting properties28. Tailoring the nanostructural surface by the SHI irradiation would be interesting to understand insight on electron induced local chemical modification in order to improvise the surface/interface interactions.In this work, we demonstrate the wetting properties of ZnO nanorods (NRs) array that could be tailored by varying the surface energy by ion beam induced intrinsic local surface alterations. So far, ion irradiations on 1D ZnO nanostructures were focused towards the study of change in structural, optical and electrical properties11+ ion irradiations at normal incidence. The experimental results show that ZnO NRs with oxygen- deficiency display nearly superhydrophobic wetting behavior. The role of self-affined defect states, surface modifications and wettability changes induced by ion irradiation were studied on ZnO NR arrays. The results presented here along with the earlier findings reveal an important method to generate different types of defect centres in ZnO material which will effectively contribute to the wettability variation on the surface. Understanding the nature and role of such defects in ZnO will be helpful for functional tailoring of its optical and electronic properties. The proposed water wetting mechanism over a 1D nanostructural platform with the presence of defect sites will promote its functional applications. In addition, this study reports that ion irradiation can be used to produce super hydrophobic platform of ZnO NR arrays depending on the electronic excitation induced by ion beam irradiation.In the present study, ZnO NRs were synthesized and their self-affine defect states were investigated via 150 MeV AgFigure 11+ ion beam with fluences of 1E11, 3E11, 5E11, 7E11, 1E12 and 3E12 ions cm−2. For studying the change in wettability as a function of ion beam fluences, the surface water contact angle (CA) and contact angle hysteresis (CAH) of the pristine and ion irradiated ZnO NR arrays were investigated. The wetting properties of the ion beam irradiated samples were studied by measuring the contact angle to water. Figure −2, the hydrophobic surface is changed to superhydrophobic surface with a CA and CAH of 152° ± 4° and 20° ± 2°. The CA and CAH of ZnO NR samples irradiated at fluences of 3E11, 5E11, 7E11, 1E12, 3E12 ions cm−2 are 161° ± 3° and 20° ± 2°; 164° ± 2° and 10° ± 2°; 167° ± 2° and 3° ± 1°; 154° ± 2° and 15° ± 2°; 151° ± 2° and 15° ± 1° respectively. Upon increasing the ion fluences, the CA is found to increase up to 7E11 ions cm−2. With the ion fluence of 1E12 ions cm−2 CA starts decreasing to 154° ± 3° but retains its superhydrophobicity. On further increasing the ion fluence as 3E12 ions/cm2, the CA decreases to 151° ± 2°. It is noteworthy that ZnO NRs irradiated at ion fluence as 7E11 ions cm−2 show higher CA (167° ± 2°) and lower CAH (3° ± 1°) indicating extreme superhydrophobic nature.ZnO NR arrays have been irradiated with 150 MeV Ag2 respectively. The SEM images of the ion irradiated samples show randomly distributed darker patches (as indicated in rings in the images) on the surface. These do not show any regular or periodic defect on the surface. The irradiation at different fluences brings about the change on the surface of the NR arrays depending on the induced diffusion. However, the morphology as well as size of these structures is not affected significantly by the SHI irradiations.The surface morphologies of the ZnO NRs after Ag ion irradiation are shown in the Fig. Figure high2 and a second order phonon of 2Elow2, modes at 432 and 330 cm−1 respectively29. The significant features of the results presented in Fig. 30 552 cm−1 (Bhigh1) are attributed to disorder-activated Raman scattering processes associated with the breakdown of the translational crystal symmetry that has been induced by the presence of defects. These defects state creation may be due to the induction of disorder on the ZnO NR arrays by ion irradiation. The irradiated films show that the intensity of the Ehigh2 mode decreases drastically upon irradiation at 3E12 ions cm−2. The Ehigh2 and Elow2 modes are associated with the O and Zn sublattices31 respectively. Thus shifts in the intensity of the Ehigh2 and Elow2 modes would be consistent with large shifts in the concentrations of O and Zn vacancies and interstitials. Previously, it has been reported that the A1(LO) mode is affected by the presence of defects32. Hence, Raman studies confirm that the SHI irradiation treatment introduces disorder into the nanostructures, which certainly includes large concentrations of intrinsic point defects associated with the O and Zn sublattices.Raman spectroscopy Fig.  is used 2. PL results show typical two emissions of narrow violet (380 nm) and broad green-yellow bands (around 540 nm)  oxygen defects are competing with each other, presenting in the competition of green and yellow bands in PL. As seen in Fig. 2, the appearance of emission peak at yellowish region reveals the creation of oxygen interstitials caused at higher fluences. It can be concluded that abundant surface oxygen vacancies or defects exist in ZnO NRs, which depends on the ion irradiation fluences.Figure nm) Fig. . The bro3/2 and 2p1/2) are observed at approximately 1021.5 and 1044.5 eV, and the splitting of the 2p doublet is around 23 eV indicating a normal state of Zn2+ in the ZnO NRs. Here, interestingly, on irradiation the 2p peak of ZnO was found to shift significantly to the higher binding energy compared to the standard value and pristine ZnO. The observed XPS peak shift can be explained, by change of electronic structure in nanocrystals, resulting in increase of binding energies37. From the previous investigations, it is clear that the Auger parameter is a useful tool to determine the stoichiometry and obtained phase in the crystal structure.Figure 3/2, we calculated the modified Auger parameter α′ (α′ = BE(Zn 2p3/2)+KE(Zn LMM), where BE and KE are binding energy of the core level 2p3/2 and a kinetic energy of the Auger transition involving electrons from L3, M4, and M5 core levels). For all samples, our calculations lead to a value around 2010.8 ± 0.7 eV, corresponding to ZnO (wurtzite) (Supplementary Table 38. On comparing the modified Auger parameter (a0) of the ion irradiated ZnO with the theoretical values, the pristine ZnO NRs matches almost perfectly when compared with the rest39. However, for the ion irradiated ZnO NR arrays, a0 is significantly high and evidences different chemical states of Zn in these ion irradiated arrays. With respect to the XPS spectrum of O 1s in Fig. The main peak of the Zn (LMM) Auger series occurs around kinetic energy of 988 ± 0.5 eV. From the kinetic energy of Zn (LMM) and binding energy of Zn 2p2, the ZnO NR arrays have strong oxygen defect ratio at 531.2 eV and 532.5 eV which are related to the oxygen signals attributed to O-deficiency and Zn-OH than the Zn-O lattice vibration. It is worth saying that ratio of oxygen vacancies and O-H increases with the ion fluences. This can be seen from the deconvoluted O1s peak showing notable shift from Zn–O bonding at 530.2 eV (lattice oxygen vibration) to Zn–O bonding at <532.5 eV (oxygen defect and Zn-OH bond vibrations) , results in superhydrophobic surfaces. In contrast, higher ion fluences induce O interstitial formation or −OH sites on the ZnO surface, which reduces the CA. Upon comparison of the O vacancy defects with the water wetting behavior on the surfaces of ZnO NRs, it is found that the presence of surface O-vacancies in ZnO NRs provides extreme superhydrophobic behavior, whereas the O interstitial defect on ZnO NR surface renders nearly superhydrophobic nature. On irradiating the ZnO surfaces by SHI, it is expected that the damaging Ag11+ ions produce the Frenkel pairs, where the vacancies are accumulated in the crystal and the interstitial defects quickly move to the surface. Therefore, the interstitials may simply move to the surface and get agglomerated there. The schematic diagram in Fig. 41.Creating the surface defect states through ion irradiation may play a dominant role in changing the wettability. The oxidized and oxygen deficiency surfaces effectively contribute to the surface energy. Oxidized surfaces exhibit high surface energy with the water molecules which can indeed make the surface hydrophilic17. Heavy ion irradiation, dominantly due to the electronic energy loss results in the electronic excitation and ionization of target by the inelastic collisions. There have been evidences of change in areal concentration of Zn and O under SHI irradiation with higher loss of O than Zn17. This result in the production of vacancies and interstitials on the ion beam irradiated ZnO surface and might facilitate the reduction of surface energy when compared to the pristine ZnO NR arrays. Collision effect through the ion irradiation clearly states that the amorphization of ZnO NRs increases with the fluence. The black patches are formed due to the SHIs which causes structural damages in the form of amorphous sites. When SHI passes through the material, it deposits large amount of energy into the material. According to the thermal spike model, the energy is deposited by the projectile ions in the electronic subsystem of the target. This energy is shared among the electrons by electron-electron coupling and transferred subsequently to the lattice atoms via electron-lattice interactions, leading to a large increase in the temperature along and in the vicinity of the ion path42. Pressure waves develop due to the temperature spike and cause strain in the nano structure. The diffusion of atoms within this zone is responsible for creating the defect enhanced surface of the nanostructures. As ion fluence increases, the fragmentation of these structures occurs due to the internal strain generated by ion beam, which results in increased amorphization of the nanostructures.The BH theory and low energy bombardment reveals the same phenomena for the surface evolution. But in present case the underlying mechanism of surface modification is believed to be due to the SHI bombardment. In our observation till now there are no theoretical or any experimental documentation available in literature for the modification of surface energy in ZnO NRs through ion bombardment, although there has been a report on creation of self-affine structures on ZnO thin films as a result of SHI irradiation2 exhibited higher CA of 168° and on further increasing the fluence, the CA reduced. It may be due to the uncontrollable creation of interstitial defects and vacancy sites which favours uncontrollable inelastic collision (ionizing the target) that damages the ZnO surface. In our case, no model currently exists to give an exact possible explanation. Electronic sputtering in the ZnO nanoarrays gives clear evidence for the fact that the ions impart enough energy to atoms to make them mobile. The atoms which have energy more than the surface binding energy will escape the surface43. If the energy of the atoms is smaller than the binding energy, then these contribute to the surface diffusion.Ion bombardment of the ZnO NR arrays with a fluence of 7E11 ions/cmThe electronic excitations induced by SHI irradiations modify ZnO NR surfaces to superhydrophobic and superhydrophilic nature through the diffusion of self-affined defect states on ZnO NRs and their stability of dewetting properties were investigated. The result from the XRD, Raman and FESEM reveal that ion beam irradiation affects the surface properties of ZnO NR arrays which with further increase of irradiation lead to homogenization of defects. The irradiated energy contributes to the changes in the surficial properties of the NR arrays. Irradiated ZnO NRs are dominated by an almost uniformly distributed nanoscale self-affine oxygen related defect states in the NR structure. Formation of these self- defected surfaces on ZnO nanostructures occur due to the change in surface energy induced by energy deposition by SHIs in the near surface region.44. Equal mole ratio of Zinc acetate and ethylamine were dissolved in methoxyethanol and heated at 60 °C for two hours. ZnO seed layer was deposited on the substrate by dip coating and was dried at 150 °C. Dip coating process was repeated three to four times and the substrate was annealed at 350 °C. The ZnO seed layer coated substrate was immersed into a solution of equal mole of Zinc nitrate hexahydrate and Hexamine (HMTA) (C6H12N4) which were used as the precursors45. After immersing the substrate by facing top down, growth solution was maintained at 97 °C for 4 hours. After the growth time of 5h, the ZnO NR coated glass substrates were taken out and washed with DI water to remove the unwanted residual zinc salt impurities and dried in a stream of N2 and annealed at 250 °C for 2 hours.ZnO NR arrays were synthesised by solution growth method. Nucleating ZnO seed layers were first deposited on glass substrates using dip coating methodThe morphological and structural characterizations of as- synthesized samples were performed by field emission scanning electron microscopy (Carl Zeiss SUPRA 55) and X-ray diffraction spectrometer (Bruker Advanced D8) at IUAC, Delhi. Optical properties were studied using JASCO V620 spectrophotometer and Horiba Jobin Yvon Lab RAM (HR 800 Evolution) photoluminescence spectrometer using He−Cd laser of 325 nm wavelength. The vibrational characterization of ion irradiated ZnO was performed by Raman spectroscopy . The Fourier transform infrared (FTIR) spectroscopy measurements were done using Bruker Tensor 27 system through ATR mode. The chemical interactions were investigated by X-ray photoelectron spectroscopy using a SPECS monochromatic Al Kα X-ray source (hν 1486.6 eV) operating at 200 W, together with a PSP Vacuum Technology electron-energy analyzer operating with a constant pass energy of 10 eV. Calibration of the spectrometer was performed using a polycrystalline silver foil, cleaned in-vacuum. The Ag 3d5/2 photoelectron line had a binding energy of 368.3 eV and a FWHM of 0.6 eV. The wettability (static and rolling) of a water droplet on different ZnO NR array samples were characterized using an optical contact angle (CA) setup. A water droplet of 5 μL was used for each study, and the contact angle measurements were performed at five different positions for each sample. For inducing the superhydrophilicity on ZnO NR surface, UV light illumination was carried out by using a 9 W Phillips UV B lamp with the wavelength of 365 nm. The distance between the sample and UV lamp during illumination was 6 cm, and the measurements were done at room temperature.11+ ion beam with fluences of 1 × 1011, 3 × 1011, 5 × 1011, 7 × 1011, 1 × 1012 and 3 × 1012 ions cm−2  at low temperature (80 K) using 15UD Pelletron tandem accelerator at Inter-University Accelerator Centre (IUAC), New Delhi. It was estimated from SRIM simulations that the electronic energy loss (Se) of Ag in ZnO is 17.6 keV/nm, while the nuclear energy loss (Sn) is 0.067 keV/nm46. The samples were mounted on the sample holder, made of copper, in the high vacuum irradiation chamber of Materials Science Beamline. In order to achieve homogeneous irradiation, the ion beam was carefully raster scanned over an area of 1 × 1 cm2. Since the range (~15 µm) of the ions was greater than the film thickness, no ions were implanted into the ZnO film and modification was expected only due to the defects produced by ions passing through these ZnO NR arrays.ZnO NR arrays have been irradiated with 150 MeV AgAll data generated or analysed during this study are included in this published article (and its Supplementary Information files).Supplementary information


Herein, a comprehensive review is introduced, concentrating on their recent progresses and various applications in recent years. First, the crystalline structure and the origin of the strong anisotropy characterized by various techniques are discussed. Specifically, the preparation of these 2D materials is presented and various growth methods are summarized. Then, high‐performance applications of these anisotropic TMDs, including FETs, photodetectors, and thermoelectric and piezoelectric applications are discussed. Finally, the conclusion and outlook of these applications are proposed.With the continuous exploration of 2D transition metal dichalcogenides (TMDs), novel high‐performance devices based on the remarkable electronic and optoelectronic natures of 2D TMDs are increasingly emerging. As fresh blood of 2D TMD family, anisotropic MTe Researches based on Raman spectroscopy, polarization‐resolved reflectance spectroscopy, and photoluminescence spectroscopy have demonstrated the strong anisotropic characteristics of these materials.2 V−1 s−1) of MTe2 and ReX2 facilitates the ultrahigh‐speed conversion of photons into electrical signals, providing an ultrafast response time in optoelectronic devices.2 and few‐layer ReX2 possess direct energy gaps from the near‐infrared to the visible spectral region, as their bandgap ranging from 1–1.6 eV.2, MTe2 and ReX2 have asymmetrical 2D crystal lattices. In‐plane orientation‐dependent electron and phonon properties are introduced into the system, which may inspire new concepts or ideas in angle‐resolved semiconductor devices.2 due to its anisotropic structure, as determined by first‐principle calculations.2 with a high responsivity of 1000 A W−1 was reported by Liu et al.The strong anisotropic properties of the MTe2 and ReX2, with particular focus on their various applications. First, the crystalline structure and the origin of the strong anisotropy of these materials were analyzed using various characterization techniques. In addition, we discuss the preparation of these 2D materials, highlighting relevant mechanical exfoliation and chemical vapor deposition (CVD) methods. Following this, we discuss FETs, photodetectors, thermoelectric and piezoelectric applications based on these anisotropic TMDs. Finally, we present the challenges, opportunities, and outlook of these applications based on current views.In this review article, we give a comprehensive review of the recent progress in anisotropic MTe22.12, have an isotropic hexagonal phase (2H) and octahedral phase (1T) crystal structure. This structure consists of alternating stacks of single‐layer trigonal prisms formed by X atoms around the M atoms  and the Td phase .TableThe lattice structures of some TMDs that have recently joined this family, specifically MTe2 and ReX2, the 1T′ or Td phase of the atomic system is stable for the ambient environment. However, under certain conditions, the 1T′ (or Td) and 1T phases interconvert, as the energy gap of the two phases can be bridged mechanically or thermally.2/WTe2) and group VI TMDs with rhenium atoms (ReSe2/ReS2) in the crystalline structure, which is discussed in detail in the following section.Moreover, the crystalline structures in these strongly anisotropic TMDs are not static. For MTe2.1.12, the chalcogen atoms are not all equally displaced above and below the Re plane in polytelluride TMDs.2 and ReS2 validated by Liu et al.2 are shown in Figure 2 has two principal axes, . In accordance with the angles of the a and b axes, a quadrilateral shape with an angle of ≈60° or 120° is observed in thin, exfoliated ReS2, and the large anisotropic ratio of mobility of ReS2 along the two axes (up to 3.1) is the highest of all studied layered 2D materials. Meanwhile, the weak interlayer interaction exhibited in ReS2 and ReSe2, which is different from other TMDs, also affects the strong anisotropic properties.2 crystal possesses an interlayer coupling weaker than most TMD crystals, such as MoS2 and WS2. The interlayer decoupling originates from the Peierls distortion of the initial 1T ReS2 revealed by Zhong et al. As a result of the disordered stacking and minimized wavefunction overlap, this interlayer decoupling provides an ideal platform to characterize unique phenomena in few‐layered ReX2 while circumventing the challenge of preparing monolayer samples.2 layers are very weak.2 exhibit unique anisotropic optical and electronic properties.2 (or ReS2) has fascinating anisotropic properties at near‐infrared frequencies. Yu et al. calculated that ReS2 maintains a direct bandgap (≈1.58 eV) from bulk to monolayer with no dependence on the number of layers based on density functional theory (DFT)  possesses semiconducting (2H) and semimetal distorted octahedron (1T′ or Td) phases and exhibits anisotropic absorption behavior in the visible range.2 and WTe2, the strong anisotropic properties lead to a semimetal phase. The stable Td phase of WTe2 imparts reduced symmetry, which leads to the in‐plane anisotropy of various physical properties.2 exhibits an indirect–direct bandgap transition when going from bulk to monolayer  direction, Keum et al. achieved a stable monoclinic 1T′ MoTe2 phase; this process is known as the 1D Peierls distortion of MoTe2.2) is a semimetallic layered transition metal dichalcogenide in the Td phase. Td WTe2 is constituted of triple‐layer covalently bonded Te—W—Te atomic planes stacked along the perpendicular direction, as shown in Figure 2 is strongly distorted from the ideal hexagonal net because the off‐centering W atoms form slightly buckled W—W zigzag chains along the x axis of the orthorhombic unit cell  showed strong anisotropic properties, and exhibits anisotropic absorption behavior in the visible range. Figure For 2D tellurides, specifically MoTeer Figure2a,b.992.22 as an example, the Raman spectra of the 2H phase (black) and the 1T′ phase (red) of MoTe2 are shown in Figure2 exhibits E2g and Ag modes at 235 and 174 cm−1, while 1T′ MoTe2 does not exhibit an E2g mode, but instead new peaks appear at 124, 138, and 272 cm−1.2. The Raman spectra of mono‐ to few‐layer TMDs in the 1T′ (or Td) phase  are shown in Figure Raman spectroscopy is a useful optical method for investigating lattice vibrations and elementary excitations and has been extensively used for the characterization of anisotropic 2D materials.2, Raman scattering of the linearly polarized exciton also verifies the strong anisotropy. Chenet et al. measured the Raman spectrum of ReS2 in a backscattering geometry using a laser of 532 nm with a fixed linear polarizer. The strongest modes are present between 120 and 240 cm−1 in unpolarized Raman spectrum for a ReS2 monolayer.2 Raman modes occupy the frequency range from 100 to 300 cm−1 and are densely spaced, with the exception of a gap at ≈140 cm−1  direction, the single‐particle optical absorption spectrum begins near 2.7 eV, while for the Γ‐M3 (y) direction, the spectrum becomes significant at 2.9 eV. Ho and Huang reveal that this optical anisotropy is assigned to the transitions from nonbonding Re 5d t2g to 5d t2g* and to antibonding chalcogen p and σ states.2 exhibits a similar anisotropic optical response, with subtle differences.2 is different from the polarization direction of incident light. The lowest‐energy absorption peak (≈1.4 eV) along the Γ‐K2 (x) direction does not completely disappear for the incident light polarized along the Γ‐M3 (y) direction. Zhong et al. verified that the lowest‐energy peak of ReSe2 consists of two excitons (EΓ and EΛ), in contrast to that of ReS2. EΓ is dark when the incident light is polarized along the Γ‐M3 (y) direction, such as the lowest exciton in ReS2. Differently, EΛ is not completely dark along the same direction. Thus, the lowest‐energy peak does not have an extremely high polarization anisotropy. The oscillator strength of the excitons  shows significant spatial anisotropy. However, the prominent absorption peak at 1.4 eV is the combination of these two excitons, and the overall optical absorption does not show complete anisotropy  was first discovered by Novoselov et al., who used the method to obtain 2D graphene.3.22,2 by CVD is critical to large‐scale applications. In this section, we discuss the synthesis of anisotropic materials of MTe2, and ReX2, by CVD methods.CVD is a well‐established technology that has been demonstrated as a facile method for synthesizing large‐scale monolayer crystals, including graphene, MX2 and MoTe2 by existing CVD or physical vapor deposition methods. First, the electronegativity difference between the transitional metal (W or Mo) and Te (0.4 or 0.3 eV) is low.2 or MoTe2 stoichiometry difficult to obtain. Another problem involves synthetic issues of both the precursors and products, including oxidation,2 single crystals are grown by the chemical vapor transport (CVT) method, and then, few‐layer flakes are exfoliated onto SiO2/p++ Si substrates.2 thick films via the tellurization of Mo films deposited on 300 nm thick SiO2/Si substrates with an e‐beam evaporator or sputterer.2 is inferior to that of the mechanically exfoliated sample. This method is difficult to apply to the synthesis of WTe2 due to the low chemical reactivity between W and Te. Gong et al.'s work indicated that Te can facilitate the synthesis of MoS2/WS2 heterojunctions by lowering the melting point of the materials.Figure2 and MoTe2 on a large scale. As shown in Figure 2 and MoTe2 monolayers were characterized by their optical vibrational modes in Raman spectroscopy, and a low defect concentration was confirmed  may change the electrical properties of the materials. The crystals grown by the I2 vapor transport technique are typically p‐type,2 usually results in n‐type materials.2 and ReSe2 nanosheets.Figure2 atomic layers on mica substrates  with ammonium perrhenate and sulfur as the raw materials on SiO2/Si substrates.2 on sapphire substrates,2 flake for the first time.2 films were grown via CVD in a three‐zone horizontal tube furnace using ReO3 and S. A similar route using Se as a precursor material on SiO2/Si substrates was reported by Hafeez et al.2 on sapphire substrates,The melting point of Re is ≈3180 °C, which is one of the highest melting point of all metals, and S and Se have relatively low melting points  and high vapor pressures.3.32 nanosheets from bulk powders with a solvent‐free method by lithium intercalation. Meanwhile, their semiconducting nature and photocatalytic properties were retained.2 nanostructures by the solvothermal method. However, these nanostructures exhibit a lateral lattice compression of ≈1% compared with the bulk analogue, causing light compressive lattice strain.Chemical, electrochemical, and liquid‐phase exfoliation are also effective synthetic methods providing the scalable production of stacked 2D thin films and heterostructures, which have wide application in research fields such as catalysis42 and ReX2. Then, MTe2 and ReX2 photodetectors based on photovoltaic effects in the near‐IR and visible range for application in optoelectronics are discussed. Notably, polarized light detection is demonstrated in orientation‐dependent field‐effect photodetectors. Furthermore, we discuss the different optoelectronic behaviors in vdW heterostructures with various composite structures and tuning of the photodetector through intercalation and atmospheric exposure. Finally, we propose prospects for piezoelectric and thermoelectric applications.Logic devices based on metal–oxide–semiconductor field‐effect transistors (MOSFETs) are fundamental in microelectronic circuits.4.1FETs, one of the most elementary components in electronics, are widely used in a variety of electronic components. However, the traditional semiconductor FET is close to the miniaturization limit under the constant exploration of many researchers.2‐based FETs have been reported to possess a carrier mobility of 1–68 cm2 V−1 s−1 and large on/off ratios of 104–106.2 field‐effect transistors  (P(VDF‐TrFE) top gate reached a current maximum carrier mobility of 68 cm2 V−1 s−1 among MoTe2‐based FET  direction /graphene heterostructures can be modulated by the gate bias to achieve high quantum efficiency .2, MoSe2, WS2, and WSe2 have led to considerable progress in the field of photodetectors, the optoelectronic applications of the TMD family require further in‐depth exploration. Compared to the isotropic behavior of the well‐studied TMDs, anisotropic properties can be introduced by reducing the lattice symmetry. For instance, the electronic and phonon properties of strongly anisotropic MTe2 and ReX2 are dependent on the in‐plane orientation.2 and ReX2 can control the crystal orientation to enhance the separation of photogenerated electron–hole pairs.TableLight detection is one of the basic components of many optoelectronic applications, including imaging, quantum communication, dynamic capture technology, positioning, and guidance.r MoS2.2  nm/graph4.2.12 is a group VI TMD with a layer‐dependent bandgap, meaning that it has a tunable range of detection. In addition, Zhang et al. predicted that MoTe2 possesses a theoretical ultrahigh mobility of up to 2526 cm2 V−1 s−1, which is several times higher than that of MoS2.2 (6.5 nm) photodetectors based on photoconduction under 685 nm laser illumination with a high responsivity of 6 A W−1  and EQE (>1000%) and thus can be applied to detect extremely weak signals. Zhang et al. first fabricated few‐layer ReS2‐based back‐gate photodetectors  and small on/off ratio of 2.8. In 2016, a fast‐response‐time photodetector based on ReS2 flake was constructed by Hafeez et al. In their study, CVD‐grown ReS2 film‐ and ReS2 flake‐based photodetectors were illuminated at a 500 nm light of 3.11 mW cm−2 /MoS2 (3l) p–n diodes working in photocurrent operating mode  and was higher than that of ReSe2  and MoS2 . In particular, this device demonstrated an extremely high responsivity of 6.75 A W−1 and EQE of 1266%, which are better than other X/MoS2‐based photodetectors investigated so far.Type‐II heterostructures can effectively tune the interlayer gap due to their staggered band alignments.de Figure9a. The4.2.42 and ReX2 were discussed in the previous sections. Most photodetectors were modulated by the applied gate voltage and temperature.2, with a high carrier mobility that was calculated to be 68 cm2 V−1 s−1  than a multilayer device and a red‐light‐sensitive (633 nm) mobility of ≈14.1 cm2 V−1 s−1. Furthermore, because of the enhanced molecular physisorption due to the low symmetry structure, the photoconduction of ReSe2 nanosheet photodetectors is significantly affected by the gas atmosphere. This atmosphere‐sensitive property allows for an additional tuning approach by gas molecule gating. A high photoresponsivity of 95 A W−1 and an EQE of 18645% were found in a monolayer ReSe2‐based transistor under red light (633 nm) and an O2 environment /5.43(relaxed‐ion) 10−10 C m−1) and 2H WTe2 has the lowest piezoelectric coefficients in TMDs (e11 = 1.60(clamped‐ion)/3.40(relaxed‐ion) 10−10 C m−1). Both 2H MoTe2 and 2H WTe2 have the huge Δe11 bigger than that of MoS2. In addition, the piezoelectric effect of 2H MTe2 may be much more abundant than the theoretical calculation due to its surprising magnitude.Piezoelectricity is a direct conversion from mechanical stress force to electricity via accumulating polarization charge in asymmetrical atomic structures, which has been widely applied in micro‐electromechanical systems, actuation, sensor, and electronics calls. TMDs have been ideal candidates for piezoelectric applications for the following reasons.ZT) via reducing dimensionalities.ZT and thermoelectric efficiency. The strong anisotropic TMDs of MTe2 and ReX2 meet the above requirements and have the potential to exceed anisotropic black phosphorus. Ma et al.2 by first‐principle calculations. WTe2 exhibits thermal conductivity of 9 and 20 W m−1 K−1 along two principal lattice directions in room temperature, which is higher than thermal conductivity of black phosphorus (<10 W m−1 K−1).2 possesses weak interlayer coupling, which is different from strong interlayer coupling. The ratio between two transports of ReX2 which may result in an improvement of the ZT.The anisotropic crystal structure may benefit not only the piezoelectric properties as mentioned above, but also the thermoelectric properties. Analogous to piezoelectricity, thermoelectric devices convert heat into electrical energy by the Seebeck effect.52 and ReX2 materials. The anisotropy, caused by the distorted octahedral phase, was analyzed using various characterization methods. Mechanical exfoliation from bulk materials and CVD are the primary methods to prepare strongly anisotropic TMDs. Other methods, such as chemical and liquid‐phase exfoliation, were further discussed. However, the growth of high‐quality, large‐scale, and uniformly oriented MTe2 and ReX2 remains a challenge. In addition, the stacking of different 2D materials requires more in‐depth study to upgrade the device performance. Photodetectors containing MTe2 and ReX2 based on the photovoltaic effect show better performance than other TMDs in terms of the responsivity and EQE, especially in the detection of polarized light. Intercalation and atmosphere tuning were also demonstrated to improve the device performance. However, this improvement is not sufficient. Linear polarized excitons and selectively tunable optical Stark effects have been theoretical predicted in thin ReS2. ReX2‐based or MTe2‐based photodetectors and light‐emitting diodes are extremely promising devices that still require in‐depth examination. It is worth mentioning that magnetic‐field‐induced valley Zeeman splitting and polarization have been observed in monolayer MoTe2.2 have great potential for next‐generation optoelectronic devices. Overall, the recent findings concerning anisotropic TMDs indicate broad promise in electronic and optoelectronic applications.Herein, we reviewed the latest knowledge of the crystalline structure, preparation methods, and electronic and optoelectronic applications of novel and strongly anisotropic MTeThe authors declare no conflict of interest.