Absorption Band Edge Research Articles

Investigation of electronic structure and optoelectronic properties of Si-doped <i>β</i>-Ga<sub>2</sub>O<sub>3 </sub>using GGA+<i>U</i> method based on first-principle

In this work, the formation energy, band structure, state density, differential charge density and optoelectronic properties of undoped <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> and Si doped <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> are calculated by using GGA+<i>U</i> method based on density functional theory. The results show that the Si-substituted tetrahedron Ga(1) is more easily synthesized experimentally, and the obtained <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> band gap and Ga-3d state peak are in good agreement with the experimental results, and the effective doping is more likely to be obtained under oxygen-poor conditions. After Si doping, the total energy band moves toward the low-energy end, and Fermi level enters the conduction band, showing n-type conductive characteristic. The Si-3s orbital electrons occupy the bottom of the conduction band, the degree of electronic occupancy is strengthened, and the conductivity is improved. The results from dielectric function <i>ε</i><sub>2</sub>(<i>ω</i>) show that with the increase of Si doping concentration, the ability to stimulate conductive electrons first increases and then decreases, which is in good agreement with the quantitative analysis results of conductivity. The optical band gap increases and the absorption band edge rises slowly with the increase of Si doping concentration. The results of absorption spectra show that Si-doped <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> has the ability to realize the strong deep ultraviolet photoelectric detection. The calculated results provide a theoretical reference for further implementing the experimental investigation and the optimization innovation of Si-doped <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> and relative device design.

Manganese and Nitrogen co-doped TiO2 for the photocatalytic degradation of anionic dyes and phenol under sunlight

ABSTRACT Different compositions of manganese (x = 1 & 3 wt. %) and nitrogen (y = 1 wt. %) co-doped TiO2 (MnxNyT) photocatalysts are prepared by the conventional sol-gel method. The crystallinity, optical properties, phase purity and surface morphology of prepared nano-photocatalysts were characterised in detail. The structural analyses show that the simultaneous doping with manganese and nitrogen controls the growth of TiO2 crystal structure having an average crystallite size in the range of 14.6 to 24.5 nm. The optical analysis also demonstrated that due to the synergistic effect of Mn and N, co-doped TiO2 represents the red-shift in the absorption band edge from 3.33 eV to 2.39 eV, which improved the response of TiO2 structure towards the visible region and enhanced electron-hole separation. Among all, Mn3N1T represented the better photocatalytic efficiency against anionic dyes (Blue KBR and Red GD) and phenol under optimised conditions (such as initial substrate’s concentration = 20 ppm, photocatalyst dose = 0.5 g and solution pH of 3 and 7, respectively) due to its low bandgap, low crystallite size and high absorptivity towards the visible region. The kinetics study also showed that the degradation of dyes and phenol over Mn3N1T followed pseudo-first-order kinetics.

Cation doped approach for photodegradation of 4-chlorophenol by highly efficient solar active NiS photocatalyst: The case of Cu2+ doping

This study reports an efficient photodegradation of 4-chlorophenol using Cu2+ doped nickel sulfide (NiS) nanoparticles. Our study provides a facile method to synthesize Cu2+ doped NiS nanoparticles by partial polyol method and structurally validates the formation of single phased random-shaped particles. Cu2+ doping in NiS matrix results in a red shift of the absorption band edge, thus lowering the band gap from 3.62 to 2.98 eV and creating electron trapping centers that prevent electron-hole recombination. The presence of such electron trapping centers was attributed to oxygen vacancies which were justified from the appearance of g-signal in electron paramagnetic resonance analysis. Photodegradation study of 4-chlorophenol by Cu2+ doped NiS nanoparticles under ambient solar light showed significant improvement in degradation efficiency up to 90 % as compared to 19 % for undoped NiS nanoparticles. Furthermore, increased degradation efficiency was also backed by total organic carbon (TOC) analysis of the mineralization ability of Cu2+ doped NiS nanoparticles. Moreover, scavenging trapping analysis showed holes, ⋅OH and superoxide radicals as reactive oxidative species (ROS) primarily responsible for increased photodegradation efficiency. Thus, the synthesized Cu doped NiS nanoparticles proved to be an efficient catalyst, which could be used as a potential candidate for industrial photocatalytic applications under ambient solar light.

Effect of warpage on the electronic structure and optical properties of bilayer germanene

The electronic structure and optical properties of bilayer germanene under different warpages are studied by the first-principles method of density functional theory. The effects of warpages on the electronic structure and optical properties of bilayer germanene are analyzed. The results of the electronic structure study show that the bottom of the conduction band of bilayer germanene moves to the lower energy direction with the increase of warpages at the K point, and the top of the valence band stays constant at the K point, and so the band gap decreases with the increase of warpage. When the warpage is 0.075 nm, the top of the valence band of bilayer germanene changes from K point to G point, and the bilayer germanene becomes an indirect band gap semiconductor. This is an effective means to modulate the conversion of bilayer germanene between direct band gap semiconductor and indirect band gap semiconductor by adjusting the band structure of bilayer germanene effectively. The study of optical properties shows that the effect of warpage on the optical properties of bilayer germanene is mainly distributed in the ultraviolet and visible regions, and the warpage can effectively regulate the electronic structure and optical properties of bilayer germanene. When the warpage is 0.069 nm, the first peak of dielectric function and extinction coefficient is the largest, and the energy corresponding to the absorption band edge is the smallest. Therefore, the electron utilization rate is the best when the warpage is 0.069 nm.

Decoupling excitons behavior of two-dimensional Ruddlesden-Popper PEA2PbI4 nanosheets

Two-dimensional (2D) Ruddlesden-Popper hybrid organic-inorganic perovskites are the most promising candidates for highly efficient optoelectronic devices due to their remarkable exciton characteristics, adjustable band structure and long-term environmental stability. However, excitons emission behavior of 2D Ruddlesden-Popper perovskites is still unclear. Here we theoretically-experimentally decoupled the excitons behavior in 2D Ruddlesden-Popper PEA2PbI4 nanosheets. Theoretically, the Elliott theory was used to separate exciton and band edge absorptions of PEA2PbI4 nanosheets and determine an exciton binding energy of about 274 meV. Experimentally, spectral-dependent photoluminescence lifetime and excitation powder density-dependent photoluminescence spectra revealed that a distinct photoluminescence tail emission should be derived from localized excitons with lower emission energy than free excitons. Further, the luminescent component of the free excitons and localized excitons with their corresponding densities of states was theoretically decoupled by line-shape analysis of PEA2PbI4 nanosheets photoluminescence spectra, which is consistent with the experimental results demonstrating the existence of localized excitons. Hence, our work provides understanding on the exciton behavior and luminescence mechanism of 2D Ruddlesden-Popper perovskites, which would benefit the prediction of high-performance excitonic devices based on 2D Ruddlesden-Popper perovskites.

Waveguide-Integrated MoTe2 p-i-n Homojunction Photodetector.

Two-dimensional (2D) materials, featuring distinctive electronic and optical properties and dangling-bond-free surfaces, are promising for developing high-performance on-chip photodetectors in photonic integrated circuits. However, most of the previously reported devices operating in the photoconductive mode suffer from a high dark current or a low responsivity. Here, we demonstrate a MoTe2 p-i-n homojunction fabricated directly on a silicon photonic crystal (PC) waveguide, which enables on-chip photodetection with ultralow dark current, high responsivity, and fast response speed. The adopted silicon PC waveguide is electrically split into two individual back gates to selectively dope the top regions of the MoTe2 channel in p- or n-types. High-quality reconfigurable MoTe2 (p-i-n, n-i-p, n-i-n, p-i-p) homojunctions are realized successfully, presenting rectification behaviors with ideality factors approaching 1.0 and ultralow dark currents less than 90 pA. Waveguide-assisted MoTe2 absorption promises a sensitive photodetection in the telecommunication O-band from 1260 to 1340 nm, though it is close to MoTe2's absorption band-edge. A competitive photoresponsivity of 0.4 A/W is realized with a light on/off current ratio exceeding 104 and a record-high normalized photocurrent-to-dark-current ratio of 106 mW-1. The ultrasmall capacitance of p-i-n homojunction and high carrier mobility of MoTe2 promise a high dynamic response bandwidth close to 34.0 GHz. The proposed device geometry has the advantages of employing a silicon PC waveguide as the back gates to build a 2D material p-i-n homojunction directly and simultaneously to enhance light-2D material interaction. It provides a potential pathway to develop 2D material-based photodetectors, laser diodes, and electro-optic modulators on silicon photonic chips.

Cat-CVD SiN x as a gas barrier for application to perovskite solar cells

We investigated a silicon nitride (SiN x ) film prepared by catalytic chemical vapor deposition as a gas barrier for further improving stability of mixed-cation-halide perovskite (PVK) Cs0.05FA0.85MA0.1PbI2Br under dark air conditions. The SiN x film can be formed on the PVK capped with carrier transport layers such as 2,2′,7,7′-tetrakis[N,N-di(4-methoxylphenyl)amino]−9,9′-spirobifluorene (Spiro-OMeTAD) and phenyl-C61-butyric-acid-methyl-ester (PCBM)/aluminum-doped-zinc-oxide (AZO) with less degradation in its optical transmittance property and crystal structure. The PVK/Spiro-OMeTAD encapsulated by SiN x exhibits a slower reduction in average carrier lifetime after storage for 330 h at room temperature with ∼65%RH. The PVK/PCBM/AZO covered with SiN x shows a small blue-shift (8–10 nm) in the absorption band-edge of PVK and with less decrease in the transmittance in the long wavelength range for ∼500 h at 85 °C with ∼2%RH. These results demonstrate the effect of SiN x in preventing the degradation of PVK due to the interactions with moisture and oxygen in the air.

Implications of morphology on excited state absorption of α-MnO2 nanostructures

Nanoclusters, nanorods and nanowires of α-MnO2 were synthesized by reduction method at different annealing temperature (100 °C–500 °C). X-ray diffraction and Raman studies confirms the formation of pure tetragonal phase of α-MnO2. Surface morphology using SEM and HRTEM reveals the gradual transformation of α-MnO2 nanoclusters (100 °C–300 °C) to nanorods (400 °C) to well defined nanowires (500 °C). While increasing the annealing temperature, Ostwald ripening process initially withholds the agglomerated clusters and its size get reduced and fused that leads to orientation along particular direction. HRTEM clearly displays the influence of temperature on favoured growth plane where (411) of nanoclusters changed to (211) plane of nanorods and nanowires. Optical band edge absorption at 268 nm arising from d–d transitions of Mn4+ in MnO2 got blue shifted due to variations in morphology. Here with increase in temperature, aspect ratio increases which alters the number of surface atoms and consequently the cohesive energy put on effect in the widening of bandgap of the material from 4.31 eV (nanoclusters) to 4.63 eV (nanowires). Open aperture Z-scan technique using Nd: YAG laser (532 nm, 10 Hz & 9 ns) revealed all MnO2 nanostructures involve reverse saturable absorption ascribed due to excited state absorption and its strength varies with morphology. Significant absorption in the visible region (532 nm) provoked excited state absorption and intensity dependent variation of nonlinear absorption coefficient confirms the existence of sequential two photon absorption process. α-MnO2 nanowires with extended interconnected network and larger aspect ratio exhibits wider excited state cross-section (6.64 × 10−2 GM), higher two-photon absorption coefficient (2.01 × 10−10 m/W) and lower onset optical limiting threshold (2.13 × 1012 W/m2). This stronger optical limiting performance of α-MnO2 nanowires symbolizes the scope of utilizing optimal α-MnO2 nanostructure for optical limiting applications.

Heptazine-Based Ordered-Distorted Copolymers with Enhanced Visible-Light Absorption for Photocatalytic Hydrogen Production.

Poly(heptazine imide) (PHI), one of the attractive allotropes of polymeric carbon nitride, has recently received extensive attention in photocatalysis due to its extended conjugation for fast separation and transfer of the charges. However, pristine PHI bears an intrinsic optical absorption band edge at 460 nm, which largely restrains the visible light utilization. Herein, the narrow-bandgap PHI (N-PHI) with an ordered-distorted interface was fabricated from polycondensation of the mixture of NaSCN, cyanuric chloride, and LiCl. Results revealed that the enhanced optical absorption and the promoted separation and transfer of the charge carriers at the interface greatly improved the photocatalytic performance, which endowed N-PHI with an apparent quantum yield of 20 % for hydrogen production at 450 nm.

Extended π‑conjugated system of 3D carbon-rich carbon nitride microspheres for boosting photoelectrochemical 4-chlorophenol sensing

4-Chlorophenol (4-CP) is one of the water pollutants with high toxicity and low biodegradability. Accurate detection against 4-CP is of great value to maintain human life. A photoelectrochemical (PEC) sensor based on three-dimensional carbon-rich carbon nitride (named 3D-CN) material was proposed for monitoring 4-CP from water environment. 3D-CN material was prepared by a low-temperature supramolecular self-assembly combined with thermal-polymerization strategy. 3D and carbon rich structure endow 3D-CN material with significantly extended π-conjugated system and enhanced charge mobility, which not only easily activates inherent π → π* electronic transition, but also awakens n → π* electronic transition in 3D-CN material. The n → π* electronic transition can further extend the absorption band edge, results into excellent PEC performance of 3D-CN material. The constructed PEC 4-CP sensor showed excellent selectivity, stability, reproducibility, and accuracy for actual water sample detection. Furthermore, the sensor provided a wide detection range (1.6–3200 μg L–1) and a low limit detection (0.53 μg L–1). This work proposes a new idea for the development of graphitic carbon nitride (g-C3N4) materials with high PEC performance by introducing a synergistic regulation strategy of carbon rich and 3D structure, and broadens the application of g-C3N4-based materials in the field of PEC sensors.

Photophysics of β-Ga2O3: Phonon polaritons, exciton polaritons, free-carrier absorption, and band-edge absorption

Monoclinic gallium oxide (β-Ga2O3) has attracted much attention from the fields of optoelectronic and electronic devices owing to the properties of wide bandgap, great breakdown field strength, as well as the economic advantages of low-cost growth of large-size single crystals. Here, the basic photophysical properties including absorption (free-carrier absorption and band-edge absorption) and reflection (phonon polaritons and exciton polaritons) of differently doped β-Ga2O3 with diverse carrier concentrations are studied in detail. The unpolarized reflection spectra of differently doped β-Ga2O3 crystals are well fitted based on the non-polarized reflection model. Besides, according to analysis, the longitudinal–transverse splitting energy of β-Ga2O3 direct excitons is estimated to be as high as 100 meV, reflecting the strong interaction between light and excitons. It is hoped that this work can provide beneficial reference for a comprehensive understanding on the spectral physical characteristics of β-Ga2O3, so as to deepen and expand the basic recognition of this material in the aspect of photophysical properties.

Multifunctional PbS2 Monolayer with an In-Plane Negative Poisson Ratio and Photocatalytic Water Splitting Properties.

Designing novel multifunctional materials at the nanoscale is vitally important for flexible electronics. Here, we have uncovered a two-dimensional metal dichalcogenide PbS2 with intriguing negative Poisson ratio behavior and favorable optical and photocatalytic water splitting properties. The calculations indicate that the Poisson ratio of the PbS2 monolayer is -0.061 along both x and y lattice directions, which is attributed to its unique tetrahedral motif and the ligand field of the local PbS4 units in the PbS2 monolayer. The electronic band structures show that the narrow band gap (1.59 eV) of the PbS2 monolayer could be effectively modulated by strain engineering. Most importantly, the strain-induced tunability of optical absorbance and suitable band edge alignment make the PbS2 monolayer a promising catalyst for photocatalytic water splitting, which is further confirmed by the reaction free energies. These findings offer an effective avenue for the design and synthesis of a novel optoelectronic functional material.

Effect of heat treatment on structure, surface morphology, linear and nonlinear optical properties of Na2Pc films for optoelectronic applications

In this paper, we study the influence of thermal annealing on the structural and optical properties of disodium phthalocyanine (Na2Pc) films. Thermal evaporation method under vacuum has been successfully used to deposit thin films of Na2Pc onto quartz and glass substrates. XRD analysis indicated that the pristine film has an amorphous structure and turns into a polycrystalline upon thermal annealing. SEM technique was used to investigate the morphological properties of thin films. The linear and nonlinear optical parameters of pristine and annealed films have been investigated in the wavelength range 200–2500 nm via spectrophotometric measurements of T(λ) and R(λ). The extinction coefficient of Na2Pc films exhibited four electronic transitions, namely, the Q, N, L and C bands. By applying a single oscillator model, many spectral dispersion parameters have been estimated in the transparent region of the spectrum. The dielectric constants, dissipation factor and optical conductivity were calculated and discussed. The optical transition type, energy gaps and Urbach energy of Na2Pc films were determined by the absorption band edges analysis. Also, the nonlinear refractive index and nonlinear optical susceptibility were evaluated from the linear refractive index results. The results of this investigation indicated the possibility of using Na2Pc films in optoelectronic device applications.

Impact of DC glow discharge plasma treated Ti doped hydroxyapatite nanomaterials using antibacterial and cytotoxicity applications

In this work we developed Ti doped hydroxyapatite with were synthesized by using a solgel technique with exposed to DC glow discharge plasma with different times treated. The pure and Ti/HAp were characterised by using different characterizations like XRD, FTIR, SEM, EDAX, UV-visible, PL, TG-DTA, antibacterial activity, 3T3 fibroblast cells and MCF-7 breast cancer cell line with cytotoxity efficiency analysis. The pure HAp and Ti/HAp materials had a nanocube and nanoflakee shape in the SEM results. In the ultraviolet-visible light (UV-vis) spectrum, the band edge absorption of bare HAp and Ti/HAp samples is discovered at wavelengths of 295 nm and 328 nm, respectively. The antibacterial activity of untreated and plasma-treated pure HAP and Ti/HAp samples are tested against two gram-positive bacteria, Bacillus cereus and Staphylococcus aureus, as well as two gram-negative bacteria, E. coli and Pseudomonas aeruginosa, using the agar well diffusion technique. The MTT assay was used to investigate the mean per cent (% percent) cell survival of Ti/HAp at various concentrations (6 mg/mL; 85 mg/mL) against 3T3 fibroblast cells and human MCF-7 Breast cancer cell lines. The synthesised Ti/HAp biocompatibility makes it a viable contender for future biological uses.

Role of dopants and defects on the photocatalytic performance of g-C3N4 under visible light and sub-band gap excitation

Here, we report the photocatalytic (PC) activity of graphitic carbon nitride (g-C3N4) doped with potassium (K), magnesium (Mg), and boron (B) under visible (>390 nm), green (532 nm), and red (660 nm) light. Doped g-C3N4 has an improved band structure, high carrier density, and tunable band-edge absorption as compared to pure g-C3N4. An atomic force microscope shows a decrease in layer thickness that follows the order: g-C3N4 > K/g-C3N4 > Mg/g-C3N4 > B/g-C3N4. The evolution of nitrogen vacancies in doped g-C3N4 was identified via x-ray photoelectron spectroscopy (XPS) and CHNS/O analyses. The red-shift in the absorption spectrum of K/g-C3N4 and the emission spectrum of B/g-C3N4 is caused by the band gap renormalization (BGR) effect. Quantum confinement and a possible Burstein–Moss (BM) effect both contribute to the spectral blue shift in the absorption spectra of Mg/g-C3N4 and B/g-C3N4. The BM effect, quantum confinement, and dopant-induced lattice strain might all alter the band structure and move the conduction band edge away from the valence band zone centre, causing an above band gap emission in K/g-C3N4 and Mg/g-C3N4. All samples degraded methylene blue (MB) under visible light with outstanding results, but they responded poorly to methyl orange (MO) and rhodamine B (RhB). With 83.59% MB degradation at a rate constant of 1.1 × 10−2 min−1, Mg/g-C3N4 recorded the best PC, which was three times quicker than g-C3N4 (3.7 × 10−3 min−1). When compared to g-C3N4, the doped samples’ current density (both anodic and cathodic) and carrier density were almost two times greater. The mechanism demonstrated how active edge sites, defects, and dopants contributed to the remarkable PC activity in the doped samples.

(4AMTP)PbBr2]2PbBr4: a Nontypical Cation-Coordinated Perovskite Showing Deep-Blue Emissions and Blue-Light Photoelectric Response.

Metal-halide perovskites have been extensively investigated due to their fascinating structural diversity and outstanding optoelectronic properties. We report the photoluminescence and photoelectric response behavior of a nontypical Dion-Jacobson perovskite [(4AMTP)PbBr2]2PbBr4 (4AMTP = 4-aminomethyltetrahydropyran cation), featuring neutral PbBr2 layers incorporated into the cationic layers between the anionic [PbBr4]2- layers. A 4AMTP-coordinated PbBr2 unit constitutes the unique nontypical dication layer. The seven-coordinated PbBr6O unit forms a largely distorted decahedron with a short distance from the inorganic [PbBr4]2- layer. The photoluminescence behavior of [(4AMTP)PbBr2]2PbBr4 shows crystal size dependence. Larger crystals show purplish-blue emission with two peaks at 414 and 431 nm, whereas smaller grain size (<50 μm) crystals demonstrate a single emission peak at 425 nm. Meanwhile, it shows a blue-light photoelectric response under the illumination of 405 nm with an on/off ratio of 175 for single-crystal devices and 97 for thin-film devices. The photoresponse performance is proportional to the molar extinction coefficient of the absorption band edge.

Third order nonlinear optical absorption studies of Cr3+ doped PbWO4 nanostructures

We report the synthesis of Cr3+ doped PbWO4 nanoparticles with different concentration of Cr3+ through chemical method. The structural, morphological and optical characterization was studied through X-ray diffraction (XRD), Raman, UV–Visible spectra, Photoluminescence, X-ray photo electron spectroscopy (XPS) and Transmission electron Microscopy (HR-TEM). The XRD patterns revealed the tetragonal phase of stolzite and the peaks are highly crystalline structure with no segregation of Cr3+. UV–Vis absorption spectra reveal that the shift of absorption band edge towards higher wavelength upon doping of Cr3+ions. The average particle size of the nanostructure as revealed by the TEM image lies around 47 nm. Third order nonlinearity of Cr3+ doped PbWO4 nanoparticles were analysed by the standard Z-scan technique using 532 nm Nd: YAG laser. The observed nonlinear absorption (NLA) and nonlinear refraction (NLR) behavior is caused by thermal nonlinear effects due to localized heating. Experimental results have demonstrated that an increase in optical nonlinearity occurs with higher Cr3+ concentrations. Based on the observed nonlinearity it is suggested that the synthesized nanostructures could be used in various optical device applications.

Single-layer and bilayer MoSTe for photocatalytic water splitting: Role of optical absorption correction and band edge distribution

Single-layer and bilayer Janus transition metal dichalcogenides (TMDCs) attain great attention for possible application in solar water splitting. The crucial issues for solar water splitting are the band edge positions and optical absorption of photocatalysts. However, for this large group of Janus TMDCs materials, their optical absorption correction by the effective unit cell volume and the charge distribution of band edges, were not investigated in most previous works. To clarify these issues, we herein studied the electronic and optical properties of typical single-layer and bilayer MoSTe using first-principles calculations. Remarkably, when corrected by the effective unit cell volume, the optical absorption of bilayer MoSTe is not enhanced when compared to that of single-layer MoSTe. On the other hand, single-layer MoSTe possesses no solar water-splitting ability for lack of suitable band edges, when the charge distribution of band edges is considered. Furthermore, favorable band edges for water splitting were achieved in bilayer MoSTe. In brief, this work emphasized the optical absorption correction by the effective unit cell volume and the charge distribution of band edges when searching for 2D photocatalysts stacking by Janus monolayers.

Smart Covalent Organic Framework with Proton-Initiated Switchable Photocatalytic Aerobic Oxidation

To conveniently regulate photocatalytic reactions, the design and development of smart photocatalysts, which can realize a series of controllable regulation of their structure, physicochemical properties, photocatalytic activity, and selectivity by simple external stimuli, such as chemical substances, pH, light, electric field, and heat, has aroused keen interest. However, the relevant research is still in its infancy. Herein, a smart imine covalent-organic-framework (COF) photocatalyst HP-n (n represents the pH of COF pretreatment, n = 1∼7) with proton-initiated switchable photocatalytic aerobic oxidation has been prepared. In the structure, the imine units can be reversibly protonated, which leads to the COF skeleton rearrangement from the phenolic to its quinone structure. The corresponding absorption band edge is expanded from 463 nm (HP-7) to 630 nm (HP-1). Meanwhile, the excitation energy transfer, oxygen adsorption, and activation change significantly, endowing HP-n with smartly switchable 1O2 production and interesting proton-initiated efficiency photocatalytic sulfide oxidation with both conversion and sulfoxide selectivity >99%. This work demonstrates a smart imine-COF photocatalyst, which paves the way for the development of smart photocatalysts and reveals the critical roles of protons in the structure–property–activity relationship of COF photocatalysts.

Realization and optimization of enhanced and spectral selective photoluminescence in size and phase controlled nanocrystalline Ga2O3 films made by pulsed laser deposition

• Nanocolumnar β-Ga 2 O 3 thin films were made by pulsed-laser deposition. • Performed detailed structural, interfacial and optical characterization of Ga 2 O 3 films. • Controlled processing conditions allow to tune the surface/interface microstructure. • Spectral selective photoluminescence demonstrated from nanotextured β-Ga 2 O 3 films. Realization and optimization of the optical properties for tunable and/or enhanced emission characteristics is critical to further advance the field of optoelectronics, photonics, and electronics for extreme environment applications. While recent advancements made to realize high-quality single crystals of Ga 2 O 3 , an interesting material for electronics and optoelectronics, strategies to obtain enhanced functionality and desired optical properties in nanocrystalline Ga 2 O 3 without needing to expensive epitaxial systems or quite cumbersome equipment or rare-earth dopants remains a challenging problem for further development. In this context we have demonstrated high yield spectral selective photoemission, from pulsed laser deposited (PLD) un-doped Ga 2 O 3 thin films with extensive control over nanocrystalline growth. Structural, interfacial and morphological investigation reveals the formation of perfect nanocrystalline seed layer promoting further growth of compact nano-columns with nano-textured atop. Optical spectroscopy demonstrates the desired control over band-edge absorption and realization of ideal photo-transition in perfectly oriented nano-columnar PLD β-Ga 2 O 3 films. Ellipsometry shows the growth parameters dependent evolution of refractive index over broad spectral range. The findings as presented and described here provide evidence for controlled growth and realization of nanocrystalline β-Ga 2 O 3 for functional device applications in optoelectronics in addition to provide a platform to further explore their futuristic technological applications.