ZnO Monolayer Research Articles

Adsorption and evolution of N2 molecules over ZnO monolayer: a combined DFT and kinetic Monte-Carlo insight

AbstractA large surface area, wide band gap, and unique bonding property between Zn and O atoms make the hexagonal ZnO monolayer attractive as a gas sensor. In the present work, the adsorption and evolution of nitrogen (N2) molecules over a ZnO monolayer have been studied using two different theoretical methods: van der Waals density functional theory (vdW-DFT) and kinetic Monte-Carlo (kMC) simulation. The adsorption and diffusion (hopping over the surface) energy of a N2 gas molecule has been calculated considering the different sites over the ZnO substrate using the revPBE-vdW functional. Bader charge, electron localization function analysis, density of states and band structure plotting have been used to understand the adsorption mechanism. Lateral repulsive interaction between two N2 molecules limits the maximum packing number of gas molecules within one hexagonal ring. The output of the vdW-DFT calculation has been fed to the kMC code to predict the rate of adsorption, desorption, and diffusion, along with the overall surface coverage at different temperatures and pressures. Finally, the change in the N2 adsorption energy has been predicted with the increase of the ZnO layer number.

The electronic and magnetic properties of Cr-doped ZnO monolayer at higher percentage by first principles calculations

The crystal structure, structural stability, electronic band structures and magnetization of Cr-doped ZnO monolayer (ML) have been investigated by GGA+U method using first principles calculations in this work. The stability of these systems is confirmed by the negative formation energies at different Cr concentrations. The calculated band gaps with and without the Hubbard U correction aligned well with other computational results. With the increase of Cr concentration, the band gap of Cr-doped ZnO monolayer decreases for the spin-up configuration. However, in the spin-down configuration, the band gap increases first and then decreases and the maximum band gap is obtained at 22.22% Cr concentrations. At 33.33% Cr concentration, the ZnO ML exhibits metallic behavior. The density of states (DOS) analysis reveals an asymmetric nature, indicating ferromagnetism in Cr-doped ZnO MLs at various concentrations, with a magnetic moment per Cr atom of approximately 3.99 μB. The total magnetic moment rises with increasing Cr concentration. Charge density difference analysis shows increased magnetization with higher Cr concentration. At 22.22% Cr concentration, the ZnO ML exhibits ferromagnetism and semiconducting properties, suggesting significant potential for spintronic applications as a diluted magnetic semiconductor.

Ab Initio Study of the Influence of Spin and Orbital Magnetic Moments on the Stability of Magnetic and Charge Distribution in Co:ZnO Monolayer.

The development of ultrathin magnets with tunable magnetic properties is essential for advancing quantum computing technologies. In this study, density functional theory (DFT) calculations were employed to investigate the atomic and electronic structures of a ZnO monolayer embedded with cobalt atoms. The impact of spin dynamics on charge transfer within the Co:ZnO system was thoroughly examined. Results revealed that the orbital magnetic moment of the cobalt atoms plays a crucial role in stabilizing the magnetic and charge distributions across the system. These findings offer valuable insights for the design and fabrication of quantum devices, thereby highlighting the potential of Co-doped ZnO monolayers in quantum computing applications.

CO oxidation on single Pt atom supported by two-dimensional ZnO monolayer: Reaction mechanism and precursor activation

CO oxidation is an effective solution for controlling CO emissions, and supported single-atom catalysts have shown excellent catalytic reactivity for chemical reactions. CO oxidation on a single Pt atom supported by a two-dimensional ZnO monolayer is investigated by combing ab initio molecular dynamics and density functional theory calculations. Seven reaction mechanisms are identified, including two new trimolecular Elie-Riedel mechanisms; six of them, except for the Mars-van Krevelen mechanism, have rate-limiting step energy barriers between 0.31 and 0.47 eV, which is lower than the experimental activation barrier of 0.81 eV on single Pt atoms supported by bulk ZnO, and is much lower than that of about 1.0 eV on Pt(111) surface. Furthermore, two preferred reaction mechanisms are discovered, an Eley-Rideal mechanism and a trimolecular Eley-Rideal mechanism, both of which have rate-limiting step energy barriers as low as 0.31 eV. Our results show that the more antibonding orbitals are filled in the reaction precursor, the higher its activation level. Activation of precursors plays an important role in CO oxidation and leads to different mechanisms. These results provide insights into the design of efficient single-atom catalysts supported by two-dimensional materials for the removal of CO pollutants.

High sensitivity of nitrobenzene on the ZnO monolayer and the role of strain engineering

Volatile organic compounds (VOCs) emissions have been a recurring problem that has challenged research centers to find new ways to monitor them. From this perspective, this work investigates nitrobenzene sensing through computational simulations, a well-known toxic compound, using the strained and strain-free two-dimensional (2D) ZnO monolayer, a traditional metal oxide semiconductor (MOS). The results indicate that nitrobenzene is adsorbed via strong physisorption on the 2D ZnO and maintains interaction with the sensor under thermal stimulus (500 K), as demonstrated via ab initio molecular dynamics (AIMD) simulations. The nitrobenzene also changes the ZnO band gap energy from 4.59 to 1.85 eV and shifts 0.35 eV the work function value. Under biaxial strain, the nitrobenzene becomes chemisorbed on the ZnO monolayer. Also, remarkable conductivity changes are observed with the nitrobenzene adsorption on the strained ZnO. Excellent values of sensitivity are found, 2.29 × 1023, 8.11 × 1022 and 2.80 × 1016 for strain-free ZnO and the maximum compressed and stretched ZnO monolayer, respectively. Short recovery times of 1.16 × 10−4 s (T = 300 K) and 6.89 × 10−8 s (T = 500 K) are also found for strain-free ZnO monolayer, indicating a great reusability for nitrobenzene. Consequently, the ZnO monolayer can be used to detect nitrobenzene.

Coupling of Piezo/Flexoelectricity and Its Effect on the Band Structure of Wrinkled ZnO Monolayers

Coupling of Piezo/Flexoelectricity and Its Effect on the Band Structure of Wrinkled ZnO Monolayers

Tunable electronic and magnetic properties of defective g-ZnO monolayer doping with non-metallic elements.

The electronic and magnetic properties of non-metallic (NM) elements doping defective graphene-like ZnO (g-ZnO) monolayer including O vacancy (VO) and Zn vacancy (VZn) are studied. The results show that VO-g-ZnO is a semiconductor and VZn-g-ZnO is a magnetic semiconductor. B, C, N, Si, P, 2S, and 2Si doping VO-g-ZnO systems present half-metal and magnetic semiconductors, and the magnetism mainly originates from the spin polarization of doping atoms. For single or double NM elements doping VZn-g-ZnO, 2P doping system presents a semiconductor, while other systems present ferromagnetic metal, half-metal, and magnetic semiconductor. The magnetism of single NM elements doping VZn-g-ZnO mainly comes from the spin polarization of O atoms near the defect point. For double NM elements doping VZn-g-ZnO, spin splitting occurs mainly in p orbitals of O atoms, dopant atoms, and d orbitals of Zn atoms. NM elements doping defect g-ZnO can effectively regulate the electronic and magnetic properties of the system. The software package VASP 5.4.1 (Vienna ab initio Simulation Package) is used for calculations in this paper. The local density approximation (LDA) is adopted as an exchange and correlation function to perform the structural optimization and analysis of electronic structure and magnetic properties.

Ab initio calculations on magnetic and optical characteristics of pure ZnO and Mn(II)-doped ZnO monolayers with and without neutral charged vacancies defects

At high Curie temperatures, diluted magnetic semiconductors exhibit induced ferromagnetism and spin-dependent interactions, making them useful in magneto-electronic devices. In spite of the fact that ferromagnetism and optical emission dynamics are characterized by intricate microstructural and compositional features, the origins of these phenomena are not yet completely understood. Here, we used first principles calculations to study how vacancy defects affect the electrical, optical, and magnetic properties of pure ZnO and Mn@ZnO monolayers. In the pristine monolayer, the Zn vacancy produces magnetism with a total magnetic moment of 2 μB, but the oxygen vacancy does not. The magnetic semiconducting characteristic of the Mn substitution at the Zn site is shown by a total magnetization of 5 μB. The magnetic ground state of the ZnO monolayer doped with Mn is significantly influenced by the presence of native defects. More specifically, Zn vacancies are essential for stabilizing the FM states due to the bound magnetic polarons (BMPs) formation, but O vacancies have no influence on the magnetic ground state of the Mn(II)@ZnO monolayer. Based on the optical study, we discovered that Zn and O vacancies in the ZnO ML produce optical absorption peaks at 1.92 eV and 2.90 eV, respectively. The substitution of Mn(II) at Zn site not only increases the band gap of the ZnO monolayer but also produces d-d transition bands at lower energy side of fundamental energy gap peak. The Zn vacancies in the Mn(II)@ZnO ML produce an infrared absorption band around 1.13 eV, which could be due to the formation of the BMP, and enhance the optical absorption efficiency. The ZnO ML’s energy gap and Mn ion’s d-d transition bands exhibit a blueshift in AFM systems and a redshift in the FM systems. In far configuration, the Mn(II)@ZnO monolayer show no shift in the fundamental bandgap and intra-band transition of the Mn(II) spins due to the Mn(II) ion’s paramagnetic nature.

Adsorption of NO on ZnO monolayer doped with transition metal (Ti, V, Cr, Mn, Co, and Zr): The first-principles study

Nitric oxide (NO) is a harmful gas produced by fuel combustion in the petrochemical industry. In this paper, the gas sensitivity of NO molecule on ZnO monolayer (ZnO-ML) doped with transition metal (TM = Ti, V, Cr, Mn, Co, and Zr) is systematically investigated by the first-principles calculation. The results show that the adsorption mode of NO molecule on the doped system (TM-ZnO-ML) changes from physisorption to chemisorption, and adsorption energies range from −1.59 eV to −3.12 eV, which are 8–16 times the origin adsorption energy (−0.19 eV) on the pristine ZnO-ML. Meanwhile, the charge transfer between NO molecule and substrates increases by 4–13 times compared with the pristine ZnO-ML. Furthermore, under the applied electric field of −0.4 V/Å, the charges transferred from V-ZnO-ML to the NO increase to 0.54 e. All of the results reveal the broad application prospect of TM-ZnO-ML in NO gas sensors.

Novel ZnO nanosheet with buckling stress: First principles study of electronic, structural stability, phonon vibrations, lattice thermal and optical conductivity

The physical properties of buckled ZnO monolayers are studied using DFT. It is demonstrated that when the buckling of ZnO monolayers increases, the band gap decreases confirming by both PBEsol and HSE06 approximations. A buckled ZnO monolayer is dynamically and thermally stable as is confirmed by its phonon spectrum and AIMD calculation. If the buckling increases, the frequency ranges for the phonon dispersion decrease resulting in smaller lattice thermal conductivity. Furthermore, a planar ZnO monolayer has an active optical response in the Deep-UV region, however the tunable response reaches the near-UV.

Induced ferromagnetism in Ni(II) doped ZnO monolayers via Al co-doping and their optical characteristics: ab initio study

For applications in magneto-electronic devices, diluted magnetic semiconductors (DMSs) usually exhibit spin-dependent coupling and induced ferromagnetism at high Curie temperatures. The processes behind the behavior of optical emission and ferromagnetism, which can be identified by complicated microstructural and chemical characteristics, are still not well understood. In this study, the impact of Al co-doping on the electronic, optical, and magnetic properties of Ni(II) doped ZnO monolayers has been investigated using first principles calculations. Ferromagnetism in the co-doped monolayer is mainly triggered by the exchange coupling between the electrons provided by Al co-doping and Ni(II)-d states; therefore, the estimated Curie temperature is greater than room temperature. The spin–spin couplings in mono-doped and co-doped monolayers were explained using the band-coupling mechanism. Based on the optical study, we observed that the Ni-related absorption peak occurred at 2.13–2.17 eV, showing a redshift as Ni concentrations increased. The FM coupling between Ni ions in the co-doped monolayer may be responsible for the reduction in the fundamental band gap seen with Al co-doping. We observed peaks in the near IR and visible regions of the co-doped monolayer, which improve the optoelectronic device’s photovoltaic performance. Additionally, the correlation between optical characteristics and spin–spin couplings has been studied. We found that the Ni(II)’s d–d transition bands or fundamental band gap in the near configuration undergoes a significant shift in response to AFM and FM coupling, whereas in the far configuration, they have a negligible shift due to the paramagnetic behavior of the Ni ions. These findings suggest that the magnetic coupling in DMS may be utilized for controlling the optical characteristics.

Tuning the mechanical characteristics of ZnO nanosheets via C, F, and P doping: A DFT approach

This study investigates the impact of doping with carbon (C), fluorine (F), and phosphorus (P) atoms on the structural and mechanical properties of 2 × 2 and 3 × 3 ZnO monolayers using Density Functional Theory (DFT) calculations. Our analysis reveals a notable decrease in both the elastic and bulk moduli of the monolayers upon doping, with the most significant reduction observed in the P-doped structure. For the pristine structure, the elastic modulus is measured at 78.84 N/m for the 2×2 monolayer and 79.46 N/m for the 3×3 monolayer, while the bulk modulus is 62.47 N/m and 63.94 N/m, respectively. Following P doping, the elastic modulus decreases by 56.02 % (34.67 N/m) in the 2 × 2 monolayer and 46.40 % (42.59 N/m) in the 3 × 3 monolayer. Similarly, the bulk modulus experiences substantial decreases of 53.09 % (29.30 N/m) in the 2 × 2 monolayer and 42.96 % (36.47 N/m) in the 3×3 monolayer upon P doping. Additionally, C and F doping result in reductions of 26.10 % and 11.04 % in the elastic modulus of the 2×2 monolayer and 26.27 % and 10.92 % in the 3×3 monolayer, respectively. The corresponding bulk modulus reductions are 14.51 % and 10.79 % in the 2×2 monolayer and 20.12 % and 11.15 % in the 3×3 monolayer, respectively. These findings underscore the considerable influence of various dopants on the mechanical characteristics of ZnO nanosheets, with P doping inducing the most significant reductions in both elastic and bulk moduli, suggesting its efficacy in tuning the mechanical properties of ZnO nanosheets for diverse applications.

Band-structure tunability via modulation of planar buckling in ZnO monolayer: Manifestation in optoelectronic and photocatalytic properties

Two-dimensional ZnO materials, with their exceptional characteristics, hold great potential for novel nanoelectronic devices and catalysts. However, the strategy of modulating the electronic properties is still ongoing. To address this challenge, we conducted first-principles calculations to systematically investigate the structural stability, electronic properties and tunability of photocatalytic performance in ZnO monolayers with different planar buckling. The results indicate that ZnO monolayers with different buckling exhibit dynamical and thermal stability. The band edge positions of ZnO monolayers could be effectively controlled by planar buckling, and ZnO monolayers with suitable buckling can serve as potential candidates for visible-light driven water splitting for hydrogen generation. Furthermore, the narrowed band gaps in ZnO monolayers with increasing of planar buckling suggest their potential for use in the design of optoelectronic devices in nanoscale systems. In addition, the stability of buckled ZnO monolayers on Ag/Pt substrates and planar ZnO monolayer on semiconducting blue phosphorus (BlueP) are explored. Interestingly, Ag and Pt metal substrates have been found to be suitable for the growth of buckled ZnO monolayers. While BlueP monolayer is believed to serve as an excellent substrate for the growth of planar ZnO monolayers. These findings offer new strategy for designing planar or buckled ZnO monolayers with potential applications in futuristic nano-optoelectric and photocatalysis systems.

First‐Principles Study of Carbon‐Substituted ZnO Monolayer for Adjusting Lithium Adsorption in Battery Application

AbstractStructural stability, local density of states, bonding information, and charge distribution differences of C‐substituted ZnO (C/VZnxOy) monolayer structures, as well as their interactions with lithium atoms, are investigated using the density functional theory (DFT) method. The energy required to generate vacancies in pristine ZnO monolayers is considerably high, but since the C atoms are strongly adsorbed in the vacant sites, the energy required to form C/VZnxOy structures is reduced. These lattice substitutions cause an alteration of the Zn d‐states. The bonding analysis shows that the C−O interaction is stronger than the C−Zn interaction. So, it generates high stability for these structures. Furthermore, because the development of C/VZnxOy is aimed at lithium battery electrode applications, the most fundamental thing that needs to be examined initially is the interaction between the C/VZnxOy surfaces and the lithium atoms. Li3 strongly binds on all C/VZnxOy surfaces, and it turns to Li3+ based on a simple analysis of charge distribution differences. These findings will have a substantial impact on the future development of ZnO monolayers, and their potential as lithium battery electrodes can be studied further.

DFT evaluation the photo-catalytic performance of g-C3N4 dots/ZnO with O/S doping

To develop the high-performance g-C3N4-based photo-catalysts and understand the mechanism of photo-catalytic degradation of volatile organic compounds (VOCs), we evaluated the photo-catalytic performance and corresponding catalytic mechanisms of g-C3N4 dots/ZnO (CNZO) systems using density functional theory (DFT) calculations. Our results showed that the combination of g-C3N4 dots and ZnO monolayer has a appropriate band gap and strong visible light absorption, significantly enhancing photoelectron excitation and immigration. We also observed that O/S doping exerted a significant impact on the band structure and interfacial coupling, thereby increasing the number of photoelectrons that move from the valence band (VB) of ZnO monolayer to the conduction band (CB) of g-C3N4 dots, thereby enhancing the separation of photo-generated electron-hole pairs in O/S-CNZO. Furthermore, the suitable CB and VB positions of O/S-CNZO encourage the adsorption of surface H2O and O2 molecules, leading to the generation of ·OH and ·O2− radicals crucial in VOCs degradation. This work introduces new approaches and perspectives for constructing novel photo-catalysts. Additionally, it involves a theoretical evaluation of the photo-catalytic performance of O/S-CNZO.

Highly conductive and flexible transparent hybrid superlattices with gas-barrier properties: Implications in optoelectronics

Transparent electrodes and passivation layers find extensive application in optoelectronic devices such as light-emitting diodes, solar cell. Integrating transparent conductive and gas diffusion barrier layers into a unified component holds promise for enhancing device performance and cost-effectiveness. However, research on these dual-function materials remains relatively scarce. Here, we introduce an innovative hybrid superlattice composed of ZnO and self-assembled monolayers, designed to function simultaneously as transparent conductive and gas diffusion barrier. Fabricated using low-temperature atomic layer deposition and molecular layer deposition techniques, the hybrid superlattice exhibited robust electric conductivity (surpassing 1400 S cm-1), exceptional moisture barrier characteristics (water vapor transmission rate < 4 × 10-7 g m-2 day-1), and remarkable flexibility. We systematically investigated the significant electrical improvement, attributing it to the formation of a well-defined amorphous/crystalline phase-composite structure in the ZnO nanolayer. Moreover, the organic layers in the superlattice enhance resilience against environmental degradation and mechanical deformation by forming a multilayered structure that effectively decouples defects in the underlying layers. These compelling features position the hybrid superlattice as a promising candidate for transparent conductive gas diffusion barriers, with diverse applications in emerging optoelectronics.

Insights into the Electronic, Optical, and Anti-Corrosion Properties of Two-Dimensional ZnO: First-Principles Study

The electronic, optical, and anticorrosion properties of planer ZnO crystal and quantum dots are explored using density functional theory calculations. The calculations for the finite ZnO quantum dots were performed in Gaussian 16 using the B3LYP/6-31g level of theory. The periodic calculations were carried out using VASP with the plane wave basis set and the PBE functional. The subsequent band structure calculations were performed using the hybrid B3LYP functional that shows accurate results and is also consistent with the finite calculations. The considered ZnO nanodots have planer hexagonal shapes with zigzag and armchair terminations. The binding energy calculations show that both structures are stable with negligible deformation at the edges. The ZnO nanodots are semiconductors with a moderate energy gap that decreases when increasing the size, making them potential materials for anticorrosion applications. The values of the electronic energy gaps of ZnO nanodots are confirmed by their UV-Vis spectra, with a wide optical energy gap for the small structures. Additionally, the calculated positive fraction of transferred electrons implies that electron transfer occurs from the inhibitor (ZnO) to the metal surface to passivate their vacant d-orbitals, and eventually prevent corrosion. The best anti-corrosion performance was observed in the periodic ZnO crystal with a suitable energy gap, electronegativity, and fraction of electron transfer. The effects of size and periodicity on the electronic and anticorrosion properties are also here investigated. The findings show that the anticorrosion properties were significantly enhanced by increasing the size of the quantum dot. Periodic ZnO crystals with an appropriate energy gap, electronegativity, and fraction of electron transfer exhibited the optimum anticorrosion performance. Thus, the preferable energy gap in addition to the most promising anticorrosion parameters imply that the monolayer ZnO is a potential candidate for coating and corrosion inhibitors.

Extended-analysis for ZnO monolayers, (TiO2 & WO3)/ZnO bilayers, and WO3/TiO2/ZnO multilayers deposited on silica glass substrates by RF sputtering as promising cap layers in optoelectronic applications

This study employs radio frequency sputtering (RF) to fabricate a range of thin film structures on silica glass substrates. These structures encompass ZnO monolayers, (TiO2/ZnO and WO3/ZnO) bilayers, and (WO3/TiO2/ZnO) multilayers. Thorough investigations were conducted to analyze their structural evolution, surface morphology, and optical characteristics, affirming film crystallinity via X-ray diffraction. By Scherrer's formula, the crystallite size D is determined, the microstrain of films ε is extracted by the Williamson-Hall method, and then the dislocation density δ is computed. It is found that the crystallite size increases from 8.47 to 13.56 nm with increasing number of layers. FTIR spectra identified functional groups, while SEM provided cross-section views. The presence of a tungsten trioxide (WO3) cap layer significantly influences optical properties, particularly in multilayers, impacting key parameters such as optical bandgap and tail energy. As the number of layers increases, the bandgap decreases from 3.45 to 2.47 eV, while the tail energy increases from 0.48 to 0.96 eV. The optical dispersion parameters of the fabricated layers, including the single oscillator energy Eo (changing from 6.93 to 4.96 eV), dispersion energy Ed (ranging from 32 to 48 eV), and static refractive index no (varying from 2.36 to 3.26), are computed using the WWD (Wemple-Didomenico) model. As the number of layers rose, the sheet resistance (Rsh) of the films increased, accompanied by a decrease in coverage density (DC). Elevated sheet resistance contributes to enhanced electrical resistivity, potentially benefiting resistive devices. Simultaneously, reduced coverage density can improve transparency and promote coating uniformity, offering advantages in optoelectronic and display technologies. The study also assessed inter-band transition strength and examined energy loss functions, revealing improved optical properties with additional layers. These findings highlight the system's promising potential as a cap layer in optoelectronic applications.

A Theoretical Investigation on Nitrogen Dioxide Adsorption on Self-Assembled Monolayer-Functionalized ZnO Monolayer

This study employs Density Functional Theory (DFT) calculations to elucidate the adsorption mechanism in the context of a ZnO monolayer system integrated with a Self-Assembled Monolayer (SAM) for NO2 detection. Through rigorous computational analysis, we delve into the intricate interplay of geometric transformations, the dissociation of NO2 bonds, and shifts in electronic properties ensuing from the introduction of the SAM. The observed modifications underscore the pronounced influence exerted by the SAM on the system’s behaviour. This investigation not only sheds light on the underlying mechanisms but also paves the way for potential experimental applications involving the functionalization of ZnO with SAM for enhanced gas sensing performance. The findings hold significant promise for the advancement of gas sensor technologies with improved sensitivity and selectivity.

Type‐II CdSe/ZnO Core/Shell Nanorods: Nanoheterostructures with A Tunable Dual Emission in Visible and Near‐Infrared Spectral Ranges

AbstractA synthesis and characterization of luminescent nano‐heterostructures consisting of CdSe nanorod (NR) cores and a ZnO shell with up to three monolayers of ZnO is reported. The core/shell heterostructures show a tunable, dual photoluminescence (PL) in visible and Near Infrared (NIR) spectral ranges. Upon shelling the visible PL band attributed to the carrier recombination within the CdSe core shifts to lower energy by ≈0.05 to 0.15 eV relative to the bare CdSe NRs, due to a reduced quantum confinement. A NIR band, observed ≈0.4 – 0.5 eV below the PL energy of the CdSe core, is attributed to a type‐II carrier recombination across the CdSe/ZnO interface. The total PL quantum yield (PLQY) in the brightest heterostructures reaches ≈20%, increasing ≈100‐fold over the PLQY of the corresponding bare CdSe NRs. The average lifetimes of the visible PL in some heterostructures exceeds 100 ns, compared to ≈5 ns lifetime typical for bare CdSe NRs. The average PL lifetimes attributed to the type‐II charge separated states exceed one microsecond. Strong NIR PL, tunable in the 800–900 nm spectral range and the long‐lived charge separated state make the CdSe/ZnO core‐shell NRs appealing materials for exploitation in applications such as bioimaging, photocatalysis and optoelectronics.