Search

Based on the hybrid functional method, the electronic structure, optical property and electron effective mass of α -Ga2O3, together with the properties for intrinsic and extrinsic defects incorporated into α -Ga2O3 are studied. Obtained results indicate the α -Ga2O3 possesses a wide band gap (5.31 eV), small electron effective mass (0.22 m0) and a high visible light transmittance. The nonstoichiometric α -Ga2O3 is not an excellent n-type semiconductor. To improve the n-type conductivity, the W-doped α -Ga2O3 is studied. We find that W Ga is a promising n-type defect due to its relatively small ionization energy ϵ (0/+) (0.30 eV). When the equilibrium fabrication method is selected, the WO2 is a promising dopant source. Using the equilibrium fabrication method, the defect complex (V O+ W Ga) would be formed, and the ionization energy ϵ (0/+) for defect complex (V O + W Ga) would decrease to 0.08 eV, which implies that a great number of free electrons could be induced in the samples. We expect that this work can promote the understanding of the n-type conductivity for α -Ga2O3 and provide significant insights for the development of a transparent n-type semiconductor. [ABSTRACT FROM AUTHOR]

Full-colour-sorting metalens using few nanostructured layers have recently generated considerable interest as high-sensitivity colour image sensors because of their reliability and high resolution. Based on the guided mode resonance principle and propagation phase modulation, a full-colour-sorting metalens is designed, which can theoretically obtain any wavelength of light from the incident white light and realize arbitrary wavelength focusing with the same focal length in the visible range. Without the loss of generality, we propose a prototype of such metalens used for sorting blue, green and red light from the visible spectrum commonly used in practical applications. The maximum focussing efficiency is over 50% with a relatively high numerical aperture of 0.7. The proposed full-colour-sorting metalens can be used in many applications, such as colour mixing, colour holography, colour filtering, wavelength division multiplexing and so on. [ABSTRACT FROM AUTHOR]

The utilization of two-dimensional van der waals heterostructures in optoelectronic synapses allows for the integration of information processing and memory, thereby providing novel operating platforms for simulating the perceptual visual systems and developing the neuromorphic computing systems due to its contactless, highly efficient and parallel computing. Herein, we have constructed a straightforward MoS2/WS2 heterostructure optoelectronic synapse and examined its capacity to imitate synaptic behaviors under optical stimulus. The MoS2/WS2 device demonstrated several synaptic functions, such as the excitatory postsynaptic current, short-term plasticity, long-term plasticity, pairs-pulse facilitation and 'learning-experience' behavior. Moreover, the MoS2/WS2 synaptic device can achieve a wide range of photo response wavelengths, spanning from UV to visible light, as well as the conversion from short-term plasticity to long-term plasticity. Furthermore, light-induced charge transfer due to adsorption and desorption of oxygen molecules in MoS2/WS2 heterostructure can be used to explain its working mechanism. Additionally, the synaptic plasticity of MoS2/WS2 device can be controlled by adjusting the duration, power and number of the optical pulses, which renders the MoS2/WS2-based optoelectronic synaptic device extremely favorable for implementation in the perceptual visual system. [ABSTRACT FROM AUTHOR]

In this research, the visible light active performance of Bi2ZnB2O7 (BBZO) was significantly enhanced through the formation of a composite with few layer MoS2. The resultant MoS2@BBZO catalyst was employed in both photocatalysis and photodetector applications. Comprehensive structural and morphological analyses of the MoS2@BBZO catalyst were conducted using x-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy. The estimated band gaps of BBZO and the composite were found to be 2.8 eV and 1.74 eV, respectively. Rhodamine B degradation studies demonstrated that the catalyst achieved 75% degradation within 30 min. Additionally, the photodetector application was investigated, revealing rapid photo-switching capabilities and an increased photocurrent. [ABSTRACT FROM AUTHOR]

The self-powered PVP-Co@C nanofibers/n-GaAs heterojunction photodetector (HJPD) was fabricated by electrospinning of the nanofibers onto GaAs. An excellent rectification ratio of 6.60 × 106 was obtained from I – V measurements of the device in the dark. The I – V measurements of the fabricated device under 365 nm, 395 nm and 850 nm lights, as well as I – V measurements in visible light depending on the light intensity, were performed. The HJPD demonstrated excellent photodetection performance in terms of a good responsivity of ∼225 mA W−1 (at −1.72 V) and at zero bias, an impressive detectivity of 6.28 × 1012 Jones, and a high on/off ratio of 8.38 × 105, all at 365 nm wavelength. In addition, the maximum external quantum efficiency and NPDR values were 3495% (V = −1.72 V) and 2.60 × 1010 W−1 (V = 0.0 V), respectively, while the minimum NEP value was ∼10−14 W.Hz−1/2 for 365 nm at V = 0.V volts. The HJPD also exhibited good long-term stability in air after 30 d without any encapsulation. [ABSTRACT FROM AUTHOR]

An efficient removal of the photocatalysts used in the decontamination of water is crucial after its application beside its expected visible light sensitive activities. This study presents the synthesis of magnetically separable CuFe2O4 nanoparticles (CFNPs) with enhanced photoactivity under AM 1.5 G sunlight. A simple two-step process involving co-precipitation and hydrothermal treatment is employed, with subsequent annealing at temperatures from 200 °C to 1000 °C to synthesize the CFNPs. The characteristic features of the highest photoactive tetragonal phase of CFNP are confirmed by powder XRD studies with Rietveld refinement. This scheme strategically controls the growth of a highly photoactive tetragonal phase with predominant (224) facets over other less active facets in cubic CuFe2O4. Mott–Schottky analysis confirms the p -type semiconducting nature of CFNPs. A favourable direct optical band gap of 1.73 eV, as well as photoluminescence emission quenching for visible photons, show that the (224) oriented CFNPs are good photocatalysts in the visible spectrum with demonstrated organic dye degradations, including methylene blue and others. A density functional theory-based approach validates that the adsorption of such dye is thermodynamically more favourable on (224) facets of CuFe2O4 to facilitate the redox action by the excitons. [ABSTRACT FROM AUTHOR]

This study reports the efficient synthesis and thorough characterization of novel graphene doped BiV O 4 / ZnO nanocomposites. Among these doping percentages, 3% BVZO/G is optimized composite as it shows the highest photocatalytic performance i–e 98% and 95% among all the doping percentages. Under the visible light exposure λ ⩾ 420 nm , the decomposition of tetracycline (TC) and methylene blue has been studied to evaluate the photocatalytic activity of the prepared composites. The characterization techniques such as photoluminescence spectroscopy, UV visible (UV-Vis) spectroscopy, x-ray diffraction, scanning electron microscopy, and Fourier transform infrared have been used to investigate the optical, structural, morphological, and vibrational properties respectively. The findings of the research indicate that the doping of graphene resulted in enhanced absorption of visible light and efficient mitigation of charge carrier recombination. To check the stability of optimized photocatalyst, reusability test has been performed. Additionally, role of active species has been examined using different scavengers in trapping experiment. By understanding the composite material for the enhanced photocatalysis, the results of this research help to design a sustainable and efficient photocatalyst. [ABSTRACT FROM AUTHOR]

The enhancement of light absorption in an ultrathin two-dimensional material is critical for its optoelectronic and photonic applications. In this work, we investigated the enhanced light absorption of layered PtSe2 by engineering the optical impedance and the attenuation of the PtSe2-based metal–insulator–metal (MIM) absorber. For a monolayer PtSe2-based MIM absorber, the undesirable impedance mismatch can be compensated for using the top patterned metal array in the MIM structure to achieve near-perfect absorption (99.95%), and the absorption of monolayer PtSe2 is enhanced by 8.6 times in the visible spectra. For a few-layer PtSe2 MIM absorber, the self-impedance of the PtSe2 layer becomes an important factor in modulating the optical absorption and the PtSe2-based absorbers show excellent features with broadband absorption, insensitive to the incident angle and polarization. Our results improve the viability of the PtSe2-based optoelectronic and photonic devices and shed light on the design of absorbers with hybrid 2D materials. [ABSTRACT FROM AUTHOR]

The vertical stacking of different two-dimensional materials to construct van der Waals heterostructures (vdWHs) opens up a promising platform for designing high-efficiency photocatalysts. Direct Z-scheme heterostructures for photocatalytic dissociation have received much attention in recent years, in which charge carriers migrate directly between two semiconductors without redox mediators. Here, the electronic and optical properties as well as the solar-to-hydrogen conversion efficiency of g-GeC/ PtSe2 vdWHs are systematically investigated, especially for their high-efficiency visible-light water splitting catalyst features. Calculations show that the g-GeC/ PtSe2 vdWH is a semiconductor with an indirect band gap of 1.356 eV, featuring a type-II band alignment. The built-in electric field E int and band bending at the interface lead to a direct Z-scheme photocatalytic structure, and photocatalytic water splitting can be realized in the pH range of 0–14. In particular, with biaxial tensile strain ϵ = 4% applied, the g-GeC/PtSe2 vdWH possesses a smaller band gap, wider visible light response range and very high STH conversion efficiency (η STH) up to 49.07%, entirely satisfying the optimal photocatalytic water splitting conditions. This work provides a new perspective for designing promising direct Z-scheme visible light water splitting catalysts with a high-efficiency solar energy conversion, beneficially to the development of clean energy. [ABSTRACT FROM AUTHOR]

The incomplete absorption of light in the perovskite solar cells (PSCs) due to the escape of photons and the waste of their energy in the visible spectrum hinders the efficiency of this type of solar cell. Utilizing light-trapping nanostructures and stimulating the device's plasmonic is an efficient way to increase absorption and reduce the energy losses. In this paper, a novel configuration of a nanostructured PSC with a plasmonic enhancement has been introduced to confine light in the active layer and boost energy harvesting. According to the conducted calculations, the modified configuration supports 23.4% higher short-circuit current density (J SC) and 21% power conversion efficiency compared to the conventional PSC. In this study, the finite element method has been employed to perform numerical simulations of the examined structures. For modeling and characterizing solar cells, optical physics of the devices is used in conjunction with their electrical physics. [ABSTRACT FROM AUTHOR]

Efforts over 40 yr still leave the source of astronomical infrared emission bands largely unidentified. Here, we report the first laboratory infrared (6–25 μ m) spectra of gas-phase fullerene-metal complexes, [C60-Metal]+ (Metal = Fe, V) and show with density functional theory calculations that complexes of C60 with cosmically abundant metals, including Li, Na, K, Mg, Ca, Al, V, and Fe, all have similar spectral patterns. Comparison with observational infrared spectra from several fullerene-rich planetary nebulae demonstrates a strong positive linear cross-correlation. The infrared features of [C60-Metal]+ coincide with four bands attributed earlier to neutral C60 bands and in addition also with several bands unexplained to date. Abundance and collision theory estimates indicate that [C60-Metal]+ could plausibly form and survive in astrophysical environments. Hence, [C60-Metal]+ are proposed as promising carriers, in supplement to C60, of observational bands, potentially representing the largest molecular species in space other than C60, C60+, and C70. [ABSTRACT FROM AUTHOR]

Carnation-like ZnO was synthesized by the facile precipitation method (at room temperature and in 120 min) to decompose dyes in an aqueous medium. The carnation-like ZnO had a stratified porous structure with a size of about 2–3 μ m, its petals had a smooth surface with a thickness of 5–10 nm and a width of about 300–500 nm. Ag-ZnO composites were synthesized using glucose with the assistance of PVP. The morphology of Ag-ZnO composites was almost unchanged compared to ZnO. Where, the Ag nanoparticles in the size range of 5–15 nm were uniformly dispersed on the ZnO petals, improving the catalytic ability of the composites in tartrazine (TA) degradation. The influence of Ag content on catalytic structure and performance of composite was studied. The 5Ag-ZnO sample had the highest BET surface area and pore volume and the lowest gap energy (E g) among the as-synthesized samples. The 5Ag-ZnO sample proclaimed the degradation efficiency in 70 min of 97.8% and the k ap of 0.031 min−1. The influences of catalyst content, solution pH, and concentration of dye on the photodegradation efficiency of the composite were thoroughly studied. Besides, the photocatalytic activity of the composite was demonstrated by degrading various organic substances and reusability. In addition, it was compared to a metal-semiconductor catalyst of Au-ZnO and semiconductor-semiconductor catalysts of MoS2-ZnO, Cu2O-ZnO, and SiO2-ZnO. The catalytic mechanism under visible light was proposed. [ABSTRACT FROM AUTHOR]

This article addresses the synthesis of Fe3+ doped TiO2 nanoparticles with variations of molar concentrations of Fe3+ and their adequate use as potential photocatalysts for Photocatalysis applications. Synthesized photocatalysts were characterized thoroughly by different analytical techniques in terms of morphological, chemical, structural, crystalline, optical, electronic structure, surface area etc properties. The occurrence of red shift phenomenon of the energy band gap attributes to the transfer of charges and transition between the d electrons of dopant and conduction band (CB) or valence band (VB) of TiO2. The doping of Fe3+ ions generates more trap sites for charge carriers with the surface trap sites. Thorough experimental conclusions revealed that the Fe3+ ions necessarily regulate the catalytic property of TiO2 nanomaterial. The obtained total degradation efficiency rate of Methylene Blue (MB) was 93.3% in the presence of 0.1 M Fe3+ in the host material and for Malachite Green Oxalate the efficiency was 100% in the presence of 0.05 M and 0.1 M Fe3+in the host material. In both the cases the total visible light irradiation time was 90 min. The adsorption properties of the photocatalysts have been also performed in a dark for 90 min in the presence of MB dye. However, till now there are hardly reported photocatalysts which shows complete degradation of these toxic organic dyes by visible light driven photocatalysis. of potential values of valence and conduction band shows the production of active oxidizing species for hydrogen yield and the possible mechanism of the Schottky barrier has been proposed. A schematic diagram of visible light driven Photocatalysis has been pictured showing degradation activity of Fe3+-TiO2 catalysts sample. [ABSTRACT FROM AUTHOR]

An anodic porous alumina mold with tapered pores, which can be used to form moth-eye structures, was formed by repetitions of anodization and etching. It was shown that the controllability of the pore shape of the anodic porous alumina mold improved with the number of repetitions of anodization and etching. However, it was found that even when the total anodization time or anodic charge (electrical current × time) was kept constant, the thickness of anodic films was not constant because the total etching time varied. This is because the etching of the anodic porous alumina mold not only increases the pore size but also reduces the thickness of the barrier layer so that pore growth proceeds after the barrier layer is re-formed during re-anodization. Therefore, it was found that if anodization is performed with the additional anodic charge required to re-form the barrier layer, an anodic porous alumina mold with tapered pores and uniform film thickness can be produced even if the etching time is varied. Nanoimprinting using the resulting anodic porous alumina mold was shown to form a moth-eye structure with a reflectance of less than 0.1% over the entire visible light range [ABSTRACT FROM AUTHOR]

Understanding the optoelectronic properties of optically active materials at the nanoscale often proves challenging due to the diffraction-limited resolution of visible light probes and the dose sensitivity of many optically active materials to high-energy electron probes. In this study, we demonstrate correlative synchrotron-based scanning x-ray excited optical luminescence (XEOL) and x-ray fluorescence (XRF) to simultaneously probe local composition and optoelectronic properties of halide perovskite thin films of interest for photovoltaic and optoelectronic devices. We find that perovskite XEOL stability, emission redshifting, and peak broadening under hard x-ray irradiation correlates with trends seen in photoluminescence measurements under continuous visible light laser irradiation. The XEOL stability is sufficient under the intense x-ray probe irradiation to permit proof-of-concept correlative mapping. Typical synchrotron XRF and nano-diffraction measurements use acquisition times 10–100 x shorter than the 5-second acquisition employed for XEOL scans in this study, suggesting that improving luminescence detection should allow correlative XEOL measurements to be performed successfully with minimal material degradation. Analysis of the XEOL emission from the quartz substrate beneath the perovskite reveals its promise for use as a real-time in-situ x-ray dosimeter, which could provide quantitative metrics for future optimization of XEOL data collection for perovskites and other beam-sensitive materials. Overall, the data suggest that XEOL represents a promising route towards improved resolution in the characterization of nanoscale heterogeneities and defects in optically active materials that may be implemented into x-ray nanoprobes to complement existing x-ray modalities. [ABSTRACT FROM AUTHOR]

The establishment of heterojunction is a powerful strategy to enhance the photoresponse performance of photoanode. Here, TiO2/CuInS2 (T/CIS) composites were prepared via a two-step hydrothermal method, and their morphologies were controlled by adjusting the reaction time. The absorption spectra show that CuInS2 can significantly improve the absorption of visible light. The T/CIS2 (2 h reaction time) photoanode exhibited the most outstanding photoelectrochemical (PEC) performance, with a photocurrent density of 168% that of the pure TiO2 photoanode. Under simulated sunlight, this photoanode can supply a protective photocurrent of 0.49 mA cmâˆ'2 and a protective voltage of 0.36 V to stainless steel (304ss), which are about 4 and 2 times those of the TiO2 sample. The enhancement in the photocathodic protection performance is attributed to enlarged visible light absorbance and higher charge separation rate. This study demonstrates that the TiO2/CuInS2 photoanode is a promising candidate for application in photoinduced cathodic protection of metallic materials. [ABSTRACT FROM AUTHOR]

Understanding the optoelectronic properties of optically active materials at the nanoscale often proves challenging due to the diffraction-limited resolution of visible light probes and the dose sensitivity of many optically active materials to high-energy electron probes. In this study, we demonstrate correlative synchrotron-based scanning x-ray excited optical luminescence (XEOL) and x-ray fluorescence (XRF) to simultaneously probe local composition and optoelectronic properties of halide perovskite thin films of interest for photovoltaic and optoelectronic devices. We find that perovskite XEOL stability, emission redshifting, and peak broadening under hard x-ray irradiation correlates with trends seen in photoluminescence measurements under continuous visible light laser irradiation. The XEOL stability is sufficient under the intense x-ray probe irradiation to permit proof-of-concept correlative mapping. Typical synchrotron XRF and nano-diffraction measurements use acquisition times 10–100 x shorter than the 5-second acquisition employed for XEOL scans in this study, suggesting that improving luminescence detection should allow correlative XEOL measurements to be performed successfully with minimal material degradation. Analysis of the XEOL emission from the quartz substrate beneath the perovskite reveals its promise for use as a real-time in-situ x-ray dosimeter, which could provide quantitative metrics for future optimization of XEOL data collection for perovskites and other beam-sensitive materials. Overall, the data suggest that XEOL represents a promising route towards improved resolution in the characterization of nanoscale heterogeneities and defects in optically active materials that may be implemented into x-ray nanoprobes to complement existing x-ray modalities. [ABSTRACT FROM AUTHOR]

Solar-driven photoelectrochemical (PEC) water splitting for hydrogen generation is regarded as a sustainable strategy to relieve fossil resource issue. However, its PEC conversion efficiency still suffers from the low light absorption and high electronâ€"hole recombination. Herein, we report 1D/2D hierarchical heterostructured photoelectrode constructed by ordered ZnO nanorod array and intimately attached ultra-thin Hematene (thickness of monolayer: 1â€"2 nm) for effective PEC water oxidation with visible light irradiation. The onset potential of Hematene/ZnO NRs photoanode (0.28 V versus RHE) for PEC water oxidation has an obvious negative shift compared with that of ZnO NRs (0.32 V versus RHE) indicating the enhanced PEC kinetics. Furthermore, reduced charge transport resistance (18.82 KΩ cmâˆ'2), a high carrier density of 9.03 × 1018 cmâˆ'3 and the resulting significantly enhanced incident photon-to-current efficiency enhancement compared with ZnO NRs photoanode were obtained for Hematene/ZnO NRs photoanode. All these were ascribed to the formation of large built-in electric field which was arising from the charge redistribution at the ZnO and Hematene interface, and the band alignment engineering between the components. In summary, such interfacial engineering may inspire the future development of 1D/2D hierarchical heterostructured photoanodes in the field of PEC water splitting. [ABSTRACT FROM AUTHOR]

Based on the realization of efficient utilization of cotton stalk lignin, the degradation of cotton stalk lignin by a CDs/CuO synergistic emulsion system was investigated. Copper oxide (CuO) nanoparticles with monoclinic crystal structure were prepared and carbon dots (CDs) synthesized by microwave method was combined with CuO. Under visible light, water and n-butanol were used to construct a waterâ€"oil (W/O) emulsion reaction system to achieved depolymerisation of lignin into small molecule compounds. The involvement of hydrogen peroxide (H2O2) makes the degradation of lignin in this system even more effective. The final high value-added monophenolic compound of 57.70 mg gâˆ'1 was obtained, among which the most abundant were six monophenolic compounds such as vanillin, eugenol and vinyl guaiacol and so on. The results of GC-MS and FTIR characterization indicated that H-type monomers were the main products of lignin degradation in this system. The process conditions for lignin hydrogenolysis in this system were optimized and the best ratio of CDs/CuO was obtained by product analysis. There were characterized by SEM, TEM, XRD, XPS, FTIR, and USâ€"vis. The results show that CDs/CuO aggregates into flower clusters, in which CDs are uniformly distributed on the surface of rhomboidal CuO monoliths. The analysis shows that the doping of CDs improves the absorption efficiency of CuO in the visible region, while reducing the complexation of CuO photogenerated electrons and holes, which achieves the purpose of improved photocatalytic activity of CuO. [ABSTRACT FROM AUTHOR]

A novel silver@silver chloride/carbon nanofiber (Ag@AgCl/CNF) hybrid was synthesized by electrospinning, heat treament, and subsequent in situ chemical oxidation strategy. The synthesized materials were characterized using x-ray diffraction, Fourier-transform infrared, UVâ€"Vis diffuse reflectance spectroscopy, scanning electron microscopy, and energy dispersive x-ray. The experimental results reveal that the electrospun AgNO3/PAN was carbonized and reduced to Ag/CNF, the Ag/CNF was then partly oxidized to form Ag@AgCl/CNF in which Ag@AgCl nanoparticles (ca. 10â€"20 nm in diameter) were uniformly bounded to CNFs (ca. 165 nm in diameter). The obtained Ag@AgCl/CNF was employed for Na2S2O8 activation under visible light irradiation to treat Rhodamine B (RhB). A remarkable RhB removal of ca. 94.68% was achieved under optimal conditions, and the influence of various parameters on removal efficiency was studied. Quenching experiments revealed that HO•, SO4•âˆ', 1O2, and O2•âˆ' were major reactive oxygen species, in which O2•âˆ' played a pivotal role in RhB degradation. A possible mechanistic route for RhB degradation was proposed. [ABSTRACT FROM AUTHOR]

Using sunlight to decompose water into hydrogen and oxygen is one of the most important ways to solve the current global environmental issues and energy problems. In this paper, we use density functional theory to predict the photocatalytic performance of Janus Ga2SSe nanotubes (JGSSe NTs) for the first time. The result shows that the small formation energy and strain energy ensure the stability of the nanotubes. Compared with monolayers, the visible light absorption range of JGSSe NTs is wider, and the large radius (>26.60 A) nanotubes all meet the hydrolysis potential. Surprisingly, the hole mobility of JGSSe NT was estimated to be as high as 2.89 × 104 cm2 Vâˆ'1 Sâˆ'1. In conclusion, JGSSe nanotubes are expected to be an excellent photocatalyst due to their low electronâ€"hole recombination rate, high hole mobility, solar absorption in the visible light range, and good oxidation capacity. In addition, the nanotube band gap can be effectively regulated by applying strain. It is hoped that our research will provide meaningful progress in the development of novel and efficient photocatalysts. We hope that our research will provide a possible way to develop novel and efficient photocatalysts. [ABSTRACT FROM AUTHOR]

We report the design and one-pot synthesis of Ag-doped BiVO4 embedded in reduced graphene oxide (BiVO4:Ag/rGO) nanocomposites via a hydrothermal processing route. The binary heterojunction photocatalysts exhibited high efficiency for visible light degradation of model dyes and were correspondingly used for the preparation of photocatalytic membranes using polyvinylidene fluoride (PVDF) or polyethylene glycol (PEG)-modified polyimide (PI), respectively. The surface and cross-section images combined with elemental mapping illustrated the effective distribution of the nanocomposites within the polymeric membranes. Photocatalytic degradation efficiencies of 61% and 70% were achieved after 5 h of visible light irradiation using BiVO4:Ag/rGO@PVDF and BiVO4:Ag/rGO@PI (PEG-modified) systems, respectively. The beneficial photocatalytic performance of the BiVO4:Ag/rGO@PI (PEG-modified) membrane is explained by the higher hydrophilicity due to the PEG modification of the PI membrane. This work may provide a rational and effective strategy to fabricate highly efficient photocatalytic nanocomposite membranes with well-contacted interfaces for environmental purification. [ABSTRACT FROM AUTHOR]

Circular dichroism (CD) has shown very interesting possibilities as a means to characterize the chiral signal of a chiral structure. Here, we theoretically demonstrated enhanced and tunable CD in the visible light regime using a composite structure consisting of a double-layer metal grating gaped by a dielectric waveguide layer. Based on the coupling of the waveguide modes and the localized plasmonic resonances, the CD could reach a maximum value as high as 0.52 at 635 nm, which is four times higher than the CD value obtained in a conventional double-layer grating without the waveguide coupling effect. Furthermore, the spectral positions of the enhanced CD bands could be easily tuned by controlling the structural parameters. The proposed hybrid double-grating and waveguide structures could have potential applications in chiral selective imaging, sensing and spectroscopy, especially where the transmission measurement is required. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) is gaining more and more attentions as a promising metal-free photocatalyst for H2 production. Nevertheless, from the perspective of practical applications, the photocatalytic performance over g-C3N4 in visible-light region needs a further improvement. In this work, C doping and C quantum dots (QDs) are co-integrated in g-C3N4 by a one-step thermal polymerization method to obtain an advanced C QDs/C doped g-C3N4 photocatalyst. The synergistic effects of C doping and C QDs modification promote the photocatalytic activity of g-C3N4 significantly. The optimal C QDs/C doped g-C3N4 exhibits a significant improvement on visible-light-driven photocatalytic hydrogen production (205 ÎĽ mol gâˆ'1 hâˆ'1) with an apparent quantum yield (AQE) at 420 nm reaching 1.24%, which is approximately nine-fold enhancement than that of pristine g-C3N4. The increased photocatalytic activity mainly benefits from the enhanced visible light absorption and carrier separation efficiency. This study may open a new perspective for the design and fabrication of C-modified g-C3N4 for photocatalytic hydrogen production. [ABSTRACT FROM AUTHOR]

Due to the energy transfer at the interface, the quantum dots (QDs) modification of two-dimensional (2D) materials is an effective and convenient way to improve their optoelectronic properties. In this work, we have studied the influence of the CdSe QDs on the physical properties of the 2D WSe2. After the modification of CdSe QDs, the energy transfer is observed in heterostructures which confirmed by the photoluminescence and Raman results. The WSe2/CdSe QDs heterostructure based phototransistors exhibit an ambipolar characteristic, owing to the typical type-â...ˇ band alignment. Under the illumination of 638 nm light, the performance of the device significantly improved compared with the WSe2 based device: the responsivity increased from 3.6 A Wâˆ'1 to 9.27 A Wâˆ'1; the detectivity increased from 7.73 Ă— 109 Jones to 4.38 Ă— 1010 Jones. Meanwhile, the devices exhibit good photoresponse in a wide spectral range from visible light to near-infrared light. Our work suggests that hybridizing 0D QDs and 2D material is a suitable and effective way to enhance the photodetection ability of the device and realize the ambipolar photodetection. It is a potential way to build multifunctional optoelectronic devices with broadband and high photoresponse performances. [ABSTRACT FROM AUTHOR]

It is attractive to explore practical approaches to optimize the photodegraded NO property of TiO2. Herein, a typical Z -shaped heterojunction C-TiO2/rGO composed of carbon-doped TiO2 and reductive graphene oxide (rGO) was constructed to optimize the NO removal efficiency through an in situ one-pot hydrothermal process with glucose as reductant and dopant. The C-TiO2/rGO (0.11%) composite displays a remarkable NO removal performance of 40.6% under visible light illumination. It was found that the C-TiO2 nanoparticles were tightly attached to the rGO sheets and had strong interactions with rGO, which induced a positive impact on not only the light absorption and photo-generated charge separation but also the NO adsorption and reactive oxygen species formation, resulting in boosted photodegrade NO activity. As to the photodegrade NO process over the C-TiO2/rGO, the HO• and O2•âˆ' were the dominant radicals, of which the O2•âˆ' radical originated from the interactions between C-TiO2 and rGO. We proposed a Z -scheme mechanism to illuminate the advanced photocatalytic activity of C-TiO2/rGO. This work affords an approach to developing effective photocatalysts in the NO purification field. [ABSTRACT FROM AUTHOR]

Lead-free layered double perovskite nanocrystals (NCs) with tunable visible range emission, high carrier mobility and low trap density are the need of the hour to make them applicable for optoelectronic and photovoltaic devices. Introduction of Cu2+ in the high band gap Cs3Sb2Cl9 lattice transforms it to the monoclinic Cs4CuSb2Cl12 (CCSC) NCs having a direct band gap of 1.96 eV. The replacement of 50% Clâˆ' by Iâˆ' ions generates <5 nm Cs4CuSb2Cl6I6 (C6I6) monodispersed NCs with an unchanged crystal system but with further lowering of the band gap to 1.92 eV. The p -type C6I6 NCs exhibit emission spectra, lower trap density, appreciable hole mobility and most importantly a lower exciton binding energy of only 50.8 ± 1.3 meV. The temperature dependent photoluminescence (PL) spectra of the C6I6 NCs show a decrease in non-radiative recombination from 300 K down to 78 K. When applied as the photoactive layer in out-of-plane photodetector devices, C6I6 NC devices exhibit an appreciable responsivity of 0.67 A Wâˆ'1 at 5 V, detectivity of 4.55 × 108 Jones (2.5 V), and fast photoresponse with rise and fall time of 126 and 94 ms, respectively. On the other hand, higher I- substitution in Cs4CuSb2Cl2I10 NCs (C2I10) degrades the lattice into a mixture of monoclinic and trigonal crystal phases, which also lowers the device performance. [ABSTRACT FROM AUTHOR]

The prospect of engineering the bandgap in semiconductor nanostructures all the way from ultraviolet to visible is highly significant in various applications such as photocatalysis, sensing, optoelectronics and biomedical applications. Since many semiconductors have their bandgaps in the UV region, various techniques are used to tune their bandgaps to the visible region. Doping and co-doping with metals and non-metals have been found to be highly effective in bandgap narrowing as doping creates a continuum of mid-bandgap states which effectively reduces the bandgap. Other than these techniques, the modulation of intrinsic vacancies is an effective way to control the bandgap. Among all semiconductors, titanium dioxide (TiO2) is a well-studied material for UV photocatalytic applications. TiO2 has oxygen and titanium vacancies as intrinsic defects which influence the bandgap based on its phase of existence. The oxygen vacancies generate unpaired electrons associated with Ti3+ species, resulting in the creation of donor levels within the bandgap. Trivacancies give a p-type nature to TiO2 due to excess holes and generate acceptor levels in the bandgap. The existence of a continuum of such intrinsic defect states within the bandgap appears to narrow the bandgap and enhances the visible light absorption in TiO2, although the effect is an apparent narrowing. Doping and co-doping of TiO2 with metals such as Au, Ag, Fe, Co, Ni, Pt and Pd and non-metals such as B, C, N, Br and Cl, doping with Ti3+ ions and hydrogenation have all been found to narrow the bandgap of TiO2. In this review, we focus on such intrinsic vacancy-modulated bandgap narrowing in TiO2. This review covers significant recent advancements in bandgap engineering of TiO2. [ABSTRACT FROM AUTHOR]

In this article, cadmium oxide (CdO) was deposited using pulsed laser deposition approach on porous silicon (Si) wafer for visible light photodetector application, through which a series of devices were proposed as a function of the deposition energy. The microstructural as well as optical characteristics of the prepared film/s were demonstrated, respectively, using x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and ultraviolet visible light spectroscopy (UVâ€"Vis) analysis. In details, the UVâ€"Vis analysis revealed the occurrence of optical band gaps within the range of 2.38â€"2.42 eV , while an average nanoparticle diameter was found to be 45 nm using FE-SEM technique. This in turn demonstrated a sound relation with the photoresponsive behavior of the attained photodetectors. A photoresponsivity and specific detectivity of 1.9 ÎĽ A m W âˆ' 1 and 1.21 Ă— 10 9 Jones were attained using 700 mJ laser energy. In the meanwhile, the estimated response/recover time of the addressed laser energy was found to be 300 s and 340 s , respectively. The photo-responsive characteristics of the fabricated devices were found to be in positive linear correlation with the applied laser energy. [ABSTRACT FROM AUTHOR]

Herein, we design to synthesize a novel Cu2O/ZnO/kaolinite composite catalyst by co-precipitation method. The synthesized composite catalysts were labeled as 5CZK, 10CZK, 15CZK, and 20CZK which represent 5, 10, 15, and 20% of Cu2O, respectively, on ZnO/kaolinite. The photocatalyst samples were characterized with different instruments. Moreover, the methylene blue (MB) dye was used as a target organic pollutant and the degradation was evaluated under visible light irradiation. The highest performance for the degradation of MB was achieved by 10CZK catalyst and degrades 93% within 105 min. However, ZnO (Z), Cu2O/ZnO (CZ), 5CZK, 15CZK, and 20CZK composite catalysts, degrades 28, 66, 76, 71, and 68% of MB dye, respectively. The enhanced degradation efficiency of 10CZK composites catalyst could be due to the higher adsorption properties from metakaolinite and the light-responsive properties of the Cu2O/ZnO samples under visible light. Hence, the resulting composite catalyst could be applicable for environmental remediation. [ABSTRACT FROM AUTHOR]

The hybrid materials have great significance in gas detection, photocatalysis and humidity sensing. In this paper, the SnO2/SnO material was successfully obtained by annealing Sn6O4(OH)4 at 350°C. The Sn6O4(OH)4 sample was synthesized by the coprecipitation method. The XRD analysis confirmed the formation of SnO2 and SnO phases and XPS analysis validated the results of XRD analysis (presence of the Sn2+ and Sn4+ states). The N2 adsorption-desorption isotherm revealed the mesoporous characteristic of the material along with 41.386 m² g−1 BET surface area and 3.794 nm average pore diameter. As a sensing application, a sensor based on SnO2/SnO material was fabricated on the interdigitated electrodes and investigated under combined atmospheres of humidity levels (11%RH—33%–95%RH—11%RH) and ammonia (200–1200 ppm). The response and recovery times for the maximum response (under 11%RH–95%RH—11%RH and 1200ppm NH3) were 7 s and 26 s, respectively. The experimental observations confirmed that the resistance of the sensor depends on the concentration of H2O and NH3, both form the conjugate acid-base pair and which is responsible for the response of the sensor. Moreover, SnO2/SnO material as a catalyst possessed the good results for the degradation of MB (96%) and MO (84%) under visible light source. [ABSTRACT FROM AUTHOR]

Transition metal sulfides are widely used for the modification of TiO2 to improve its light absorption range due to their small bandgaps. In this work, novel CoS/CuS/TiO2 was synthesized via a simple one-pot hydrothermal preparation method. Using various characterization techniques, CoS/CuS/TiO2 was found to demonstrate excellent photoelectrochemical performance and photocatalytic activity for the degradation of tetracycline hydrochloride. The CoS/CuS/TiO2 catalyst showcased a maximum photocurrent density of 55 μA cm−2, which was 7.8 times higher than that of unmodified TiO2 nanorods. Under visible light irradiation using Xe lamp, the photocatalytic degradation efficiency of CoS/CuS/TiO2 on tetracycline hydrochloride was found to be significantly improved, where it recorded an excellent degradation rate of 64.0% at 90 min. The charge transfer mechanism of the proposed material was also investigated. [ABSTRACT FROM AUTHOR]

Visible light observations from the Wide-field Imager for Solar PRobe (WISPR) aboard the Parker Solar Probe (PSP) mission offer a unique opportunity to study the dust environment near the Sun. The existence of a dust-free zone (DFZ) around stars was postulated almost a century ago. Despite numerous attempts to detect it from as close as 0.3 au, observational evidence of a circumsolar DFZ has remained elusive. Analysis of WISPR images obtained from heliocentric distances between 13.3â€"53.7 R ⊙ over multiple PSP orbits shows a gradually decreasing brightness gradient along the symmetry axis of the F-corona for coronal heights between 19 and 9 R ⊙. Below 9 R ⊙, the gradient reverses its trend, approaching the radial dependence exhibited at heights above 19 R ⊙. After taking into account the effects of both the electron corona background and the nonresolved starlight, the WISPR observations down to 4 R ⊙ are consistent with forward-modeling simulations of the F-corona brightness within [âˆ'6, 5]% if a circumsolar region of depleted dust density between 19 and 5 R ⊙ enclosing a DFZ is considered. In addition, we show, for the first time, that the F-corona brightness inward of about 15 R ⊙ depends on the observer’s location for observing distances below 35 R ⊙. [ABSTRACT FROM AUTHOR]

BiFeO3 is a photocatalyst with excellent performance. However, its applications are limited due to its wide bandgap. In this paper, MIL-101(Fe)@BiOI composite material is synthesized by hydrothermal method and then calcined at high temperature to obtain BiFeO3@Bi5O7I composite material with high degradation capacity. Among them, an nâ€"n heterojunction is formed, which improves the efficiency of charge transfer, and the recombination of light-generated electrons and holes promotes improved photocatalytic efficiency and stability. The result of photocatalytic degradation of tetracycline under visible light irradiation showed, BiFeO3@Bi5O7I (1:2) has the best photodegradation effect, with a degradation rate of 86.4%, which proves its potential as a photocatalyst. [ABSTRACT FROM AUTHOR]

TMDs based heterostructure have drawn much attention for its potential application in photoelectric devices benefiting from the rapid and effective carrier separation and ultra-long interlayer exciton lifetime. Recent studies on carrier dynamics of TMDs based heterostructures are mainly focused on the transfer process of photo-generated carriers across the interface and lifetime of interlayer exciton but little attention is paid on the dynamics of hot carriers. Here, the carrier dynamics of hot carriers in MoS2/WS2 heterostructure is investigated by transient absorption spectra. Rapid separation of electron and hole is observed. More importantly, hot carriers of C exciton, which contribute to the absorption of most of the visible light, could compensate for the carrier loss in the band edge exciton energy band through the intervalley transfer process. This re-injection process of hot carriers of C exciton could compensate for carrier depletion in photoelectric devices, thus may greatly improve the light utilization in optoelectronic devices. [ABSTRACT FROM AUTHOR]

To improve the photocathodic protection performance of traditional TiO2 photoanodes for metals, constructing a Z-scheme heterojunction is one of the most promising and creative strategies. Herein, we fabricated a novel Z-scheme MgIn2S4 nanosheets/TiO2 nanotube nanocomposite through anodization and hydrothermal method. The optimized Z-scheme MgIn2S4/TiO2 nanocomposites exhibited stronger visible light absorption, higher separation efficiency of photoelectrons and photocathodic protection performances in comparison to pure TiO2. The theoretical analysis and experimental results show that the Z-scheme heterojunction and oxygen vacancies jointly improved the separation efficiency of photogenerated electronâ€"hole pairs and visible light absorption capacity, thereby improving the photoelectric conversion performance of the MgIn2S4/TiO2 nanocomposites. Furthermore, the influence of the precursor solution concentration on the photocathodic protection performances of the composites was investigated. As a result, when the concentration of magnesium source in the precursor solution was 0.06 mmol, the prepared MgIn2S4/TiO2-0.06 displayed the best photocathodic protection performance. In addition, the hydroxyl radicals (·OH) generated in the electron spin resonance (ESR) experiment verified the Z-scheme heterojunction mechanism of the MgIn2S4/TiO2 composite, and also demonstrated the excellent redox performance of the composite. This work provides valuable reference for the construction of high-performance Z-scheme heterojunctions for photocathode protection of metals. [ABSTRACT FROM AUTHOR]

In this paper, Z-scheme Bi2MoO6/CNTs/g-C3N4 composite photocatalysts were prepared through a simple hydrothermal method. The analysis was performed by XRD, FT-IR, SEM, EDS, TEM, HRTEM, XPS, BET, UVâ€"Vis diffuse reflectance and PL spectrums. Various analyses show that CNTs not only act as excellent charge transfer bridges, but also enable a formation of the Z-scheme of charge transfer mechanism between Bi2MoO6 and g-C3N4. This process not only effectively isolates electrons and holes, but also prolongs electronâ€"hole pair lifetimes, resulting in a substantial improvement in the photocatalytic performance of the composite photocatalyst. Best photocatalytic degradation performance was shown by Bi2MoO6/CNTs/g-C3N4 composite photocatalyst under simulated sunlight, while the composite photocatalyst still maintained extremely high degradation performance in cycling tests. [ABSTRACT FROM AUTHOR]

We analyze low-resolution Spitzer infrared (IR) 5âˆ'14 ÎĽ m spectra of the diffuse emission toward a carefully selected sample of stars. The sample is composed of sight lines toward stars that have well-determined ultraviolet (UV) extinction curves and that are shown to lie beyond effectively all of the extinguishing and emitting dust along their lines of sight. Our sample includes sight lines whose UV curve extinction curves exhibit a wide range of curve morphology and that sample a variety of interstellar environments. As a result, this unique sample enabled us to study the connection between the extinction and emission properties of the same grains, and to examine their response to different physical environments. We quantify the emission features in terms of the polycyclic aromatic hydrocarbon (PAH) model given by Draine & Li and a set on additional features not known to be related to PAH emission. We compare the intensities of the different features in the Spitzer mid-infrared spectra with the Fitzpatrick & Massa parameters that describe the shapes of UV to near-infrared extinction curves. Our primary result is that there is a strong correlation between the area of the 2175 Ă... UV bump in the extinction curves of the program stars and the strengths of the major PAH emission features in the mid-infrared spectra for the same lines of sight. [ABSTRACT FROM AUTHOR]

CdTe-based semiconductor nanocrystals (NCs) with size and composition-dependent efficient bandgap properties are historically mature nanomaterials for colloidal optoelectronic applications. In this work, we present the highly luminescent quaternary ZnCdTeS NCs with tunable emission across a wide visible spectrum from green to red spectral range. Prepared via a direct aqueous-based approach, a second capping agent of trisodium citrate (TSC) was used to enhance the photoluminescence (PL) emission efficiency, the chemical stability, and to spectrally widen the coverage of the emission spectra of ZnCdTeS NCs. Adding TCS created a remarkable blue shift from 572 nm in the absence of TSC, to 548 nm. On the other hand, upon optimization of experimental parameters, superior ZnCdTeS NCs with a narrow PL profile typically less than 50 nm, the high quantum efficiency of 76%, and tunable emission from 515-to-645 nm were synthesized in an aqueous solvent. The keynotes were the superior and reproducible luminescent properties for the core only NCs, without shell and using relatively low reaction temperatures. It was shown that in the suggested synthesis method, the high efficiency emitted color of ZnCdTeS NCs can be easily controlled from 515-to-650 nm with excellent stability against harsh conditions. The biexponential decay profiles of samples prepared at different reaction temperatures demonstrated that the average recombination lifetime is below 40 ns and increases with the growth of the ZnCdTeS NCs. Results reveal that the excitonic energy levels have the main role in the recombination process. Finally, to demonstrate the functional advantages of the prepared NCs in optoelectronics, the NCs were used to fabricate color-conversion white light-emitting diodes. The color coordinate of the device is recorded as (0.4951, 0.3647) with CRI of 91, CCT of 1954 K, and LER of 251 lm Wâˆ'1 by employing only two distinct emitters for color conversion. [ABSTRACT FROM AUTHOR]

Owing to their unique structural and electronic properties such as layered structure with tuneable bandgap and high electron mobility, 2D materials have emerged as promising candidates for photocatalysis. Recently, bismuth oxyselenide (Bi2O2Se), a member of bismuth oxychalcogenide's family has shown great potential in high-speed field-effect transistors, infrared photodetectors, ferroelectric devices, and electrochemical sensors. However, the potential of Bi2O2Se in photocatalysis has not yet been explored. In the current work, Bi2O2Se nanosheets with an average size of ∼170 nm and a lattice strain of 0.01 were synthesized at room temperature using a facile solution-processed method and the as-synthesized material was investigated with various characterization techniques such as x-ray diffraction, FE-SEM, UV–vis spectroscopy. The bandgap for the indirect transition in Bi2O2Se nanosheets was estimated to be 1.19 eV. Further, the visible-light-driven photocatalytic degradation of methylene blue (MB) dye using Bi2O2Se as a photocatalyst is presented. The photocatalytic experiments demonstrate the promising photocatalytic ability of Bi2O2Se as it leads to 25.06% degradation of MB within 80 min of light illumination. The effect of active species trapping agents (carrier and radical scavengers) on photocatalytic activity is also presented and discussed. [ABSTRACT FROM AUTHOR]

Atomically two-dimensional materials with direct band-gap and high carrier mobility are highly desirable due to their promising applications in electronic devices. Here, on the basis of ab initio calculations and global particle-swarm optimization method, we predict the B2S3 monolayer as a new semiconductor with favorable functional properties. The B2S3 monolayer possesses a high electron mobility of 553 cm2 V−1 s−1 and a direct band-gap of 1.85 eV. The direct band-gap can be manipulated under biaxial strain. Furthermore, B2S3 monolayer can absorb sunlight efficiently in the entire range of the visible light spectrum. Besides, this monolayer holds good dynamical, thermal, and mechanical stabilities. All the desired properties render B2S3 monolayer a promising candidate for future applications in high-speed (opto)electronic devices. [ABSTRACT FROM AUTHOR]

Photofluorochromic diarylethene (DAE) molecules have been widely investigated due to their excellent fatigue resistance and thermal stability. However, the poor water solubility of DAEs limits their biological applications to some extent. Herein, we reported two kinds of water-dispersible DAE nanoparticles (DAEI-NPs and DAEB-NPs), in which DAE molecules were stabilized by the amphiphilic polymer DSPE-mPEG2000 using the nanoprecipitation approach. The fabricated nanoparticles retain well-controlled luminescence and fluorescence photoswitching properties in aqueous solution, which could be reversibly switched on and off under the alternating irradiation of ultraviolet (UV) and visible light. In addition, the closed-ring isomers of DAEB-NPs performed hot-band-absorption-based photon upconversion when excited by a 593.5 nm laser. Bearing excellent photophysical properties and low cytotoxicity, DAEB-NPs were applicable for upconversion cell imaging without high-excitation power density and free from oxygen removal. Additionally, the imaging process could be switched on by regulating the photofluorochromic nanoparticles. [ABSTRACT FROM AUTHOR]

We report an abnormal phenomenon that the source-drain current (I D) of AlGaN/GaN heterostructure devices decreases under visible light irradiation. When the incident light wavelength is 390 nm, the photon energy is less than the band gaps of GaN and AlGaN whereas it can causes an increase of I D. Based on the UV light irradiation, a decrease of I D can still be observed when turning on the visible light. We speculate that this abnormal phenomenon is related to the surface barrier height, the unionized donor-like surface states below the surface Fermi level and the ionized donor-like surface states above the surface Fermi level. For visible light, its photon energy is less than the surface barrier height of the AlGaN layer. The electrons bound in the donor-like surface states below the Fermi level are excited and trapped by the ionized donor-like surface states between the Fermi level and the conduction band of AlGaN. The electrons trapped in ionized donor-like surface states show a long relaxation time, and the newly ionized donor-like surface states below the surface Fermi level are filled with electrons from the two-dimensional electron gas (2DEG) channel at AlGaN/GaN interface, which causes the decrease of I D. For the UV light, when its photon energy is larger than the surface barrier height of the AlGaN layer, electrons in the donor-like surface states below the Fermi level are excited to the conduction band and then drift into the 2DEG channel quickly, which cause the increase of I D. [ABSTRACT FROM AUTHOR]

In this paper, we present a detailed theoretical analysis of charge exchange recombination spectroscopy based on interactions of the planned ITER neutral beams (diagnostic beam of 100 keV uâˆ'1 and heating beam of ≈1 MeV uâˆ'1) with highly-charged ions of tungsten. The results of the present spectral synthesis are based on the new set of nl -resolved charge exchange (CX) cross sections for recombination of the W q + ions (q = 61â€"66) with atomic hydrogen calculated using the classical trajectory Monte Carlo method. A large-scale collisional-radiative model describing the population kinetics of the high- n atomic states of Si-like through O-like W ions has been developed using the NOMAD code for typical conditions of the ITER core plasma, and the resulting spectra have been generated for wavelengths in the x-ray to visible range (0.1â€"1000 nm). A detailed analysis of the plasma emission predicts a significant effect of CX recombination on the W line intensity ratios that can be used for more advanced diagnostics of the ITER plasma. [ABSTRACT FROM AUTHOR]

The development of visible light photocatalysts with the ability to efficiently degrade pollutants is an important measure to solve environmental problems. In this paper, Cu2+ doped TiO2–SiO2 (CTS) with photonic crystal structure composite was successfully synthesized via sol–gel strategy and template method. The prepared materials have abundant pore structure and uniform pore diameter, and the pores were arranged in a periodically hexagonal structure. It showed enhancing synergistic effect of adsorption-photodegradation ability for removing Rhodamine B (RhB). The brilliant adsorption capability of the catalyst is not only due to the addition of silica which can increase surface area that results the increase in adsorption ability, but also related to the rich and ordered porous structure provided by the photonic crystal. The catalyst has a narrow band gap ∼2.92 eV which exhibits the excellent photocatalytic activity for RhB degradation (>95% at 30 min) under visible light irradiation, and possesses higher photocatalytic reaction apparent rate constants (k) which is 7 folds higher than that of pure TiO2. The excellent photocatalytic performance is attributed to the Cu2+ doping that narrows the band gap, increases light absorption, and promotes charge separation. Besides, the constructed photonic crystal structure not only further enhances charge transport but also provides more surface activity sites for photocatalytic reactions. More importantly, the ordered pore structure-photonic crystal can prolong the interaction time between light and catalyst through the slow photon effect and the porous scattering effect. Eventually, the photocatalytic degradation efficiency of the catalyst was significantly improved by the synergistic effect of the above mechanisms. [ABSTRACT FROM AUTHOR]

Semiconductor-based photocatalytic technology, as a green and promising avenue in response to the abuse of antibiotic pollution and human health crisis, is restricted by the limited photo-absorption and fast recombination of photogenerated carriers. In this paper, all these challenges were settled by AgBr particles incorporated into oxygen-deficient BiOBr nanosheets, forming novel oxygen vacancy (OV)-rich 2D/0D Z-scheme heterojunctions. Z-scheme photocatalytic system has an effective separation rate of photogenerated carriers and an ability to maintain original redox capacity. Moreover, introducing OVs in the Z-scheme can not only improve the visible light absorption ability, but also serve as recombination centers, thus promoting the separation of electrons and holes. Notably, the photocatalytic activity of 2D/0D BiO1−XBr/AgBr (2:1) was significantly improved under the irradiation of visible light, removing 81% of tetracycline after 25 min, which was about 2.62 times and 2.03 times as high as those of BiO1−XBr and AgBr, respectively. In addition, the 2D/0D BiO1−XBr/AgBr (2:1) indicated high photocatalytic stability and reusability, and its tetracycline degradation efficiency remained stable after five cycles. In summary, this work suggests that the photocatalysts have a great potential to remove TC and provides a possible strategy for purifying water. [ABSTRACT FROM AUTHOR]

Two-dimensional graphitic carbon nitride (g-C3N4, GCN) is considered as one of the promising visible light-responsive photocatalysts for energy storage and environmental remediation. However, the photocatalytic performance of pristine GCN is restricted by the inherent shortcomings of rapid charge carrier recombination and limited absorption of visible light. Vacancy engineering is widely accepted as the auspicious approach for boosting the photocatalytic activity of GCN-based photocatalysts. Herein, a magnesium thermal calcination method has been developed to reconstruct GCN, in which magnesium serves as a carbon etcher for introducing carbon vacancies and pores into GCN (Vc-GCN). The fabricated Vc-GCN demonstrates excellent photocatalytic performances of degrading hazardous 4-chlorophenol under visible light irradiation benefiting from the improved carrier separating and light absorption ability as well as rich reactive sites. The optimal Vc-GCN sample delivers 2.3-fold enhancement from the pristine GCN. The work provides a tactic to prepare GCN photocatalysts with controllable carbon vacancies and for a candidate for the degradation of organic pollutants from the environment. [ABSTRACT FROM AUTHOR]

The photoreactivity of TiO2 nanotube arrays (TiNT) is mainly related to the light absorption and photogenerated charge carriers separation efficiencies. Recently, engineering of the crystal facets has gained increasing attention because of its exceptional ability to extend the photoresponse toward visible light and to separate photogenerated charges. Here, TiNT with high crystallinity and percentage of exposed {001} facets was synthesized using a two-step anodization process in ethylene glycol based electrolyte containing 2 wt% of water and 0.27 M NH4F. Decreasing the potential of the second anodization (from 50 to 20 V) resulted in an increase in crystallinity, crystallite size, and percentage of exposed {001} facets. Because trap states limit the photoreactivity performance of TiNT by facilitating the recombination of photogenerated electron/hole pairs, correlation between crystallinity, preferential crystalline orientation, gap states characteristics (density and location), and photoreactivity performance was investigated. TiNT with a high percentage of {001} exposed facets, consisting mainly of shallow gap states with low density, significantly improve photoelectrochemical water oxidation and photocatalytic efficiencies. [ABSTRACT FROM AUTHOR]

Designing heterojunction photocatalysts with matched band structure and good interface contact is an effective method to improve the photoelectrochemical activity. Herein, novel CaIn2S4/TiO2 nanotube arrays (NTAs) heterojunction photoanodes were successfully prepared by electrochemical anodization and hydrothermal method. The microstructures, compositions, crystal structures, chemical valence states and light absorption performances of the composites were evaluated by field emission scanning electron microscopy, energy dispersive x-ray spectroscopy transmission electron microscope, high-resolution transmission electron microscope, x-ray diffractometer, x-ray photoelectron spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), respectively. The photocathodic protection performances of CaIn2S4/TiO2 composites for 316 stainless steel (SS) and the influences of the CaIn2S4 content on the performances were studied. The microstructural examination revealed the uniform doping of CaIn2S4 nanofragments on the TiO2 NTAs, and the composite was made up cubic CaIn2S4 and anatase TiO2. The photogenerated electrons were transferred from the TiO2 to CaIn2S4 at the interface of the composite. Compared with pure TiO2 NTAs, CaIn2S4/TiO2 NTAs exhibited better photocathodic protection performance for 316 SS under visible light. Potential drop reached 0.78 V versus saturated calomel electrode for the 316 SS coupled with CaIn2S4/TiO2 NTAs. The photocurrent density of the 316 SS coupled with the composite photoanode (235.4 μA cm–2) was 17.4 times that of TiO2. The improved photocathodic protection property of CaIn2S4/TiO2 NTAs was ascribed to the enhanced separation efficiency of the photogenerated carriers and the strong visible light absorption of the material. The CaIn2S4/TiO2 NTAs exhibited continuous protection of the 316 SS for more than 12 h even in the dark. Therefore, the CaIn2S4/TiO2 NTAs heterojunction composite is an outstanding and efficient photoanode for the photocathodic protection of metals. [ABSTRACT FROM AUTHOR]

Naked-eye observations of visible spectra using a transmission-grating-based spectrometer, with the spectral resolution of 0.2 nm @ 550 nm, are reported in this article. The resultant accuracy of the wavelength readout with the naked-eye is better than 1 nm. The diffraction angles are precisely confirmed when the virtual diffraction image of the entrance slit (line spectrum) are collinear with two collimating slits. Furthermore, a converging lens is used to magnify the tiny light source (or narrow slit), and receive more radiant flux, with no effect on the accuracy of the spectral measurement. The spectrometer provides a good training aid for college students because (1) it is a low cost and handy demo experiment; (2) it has no optoelectronic sensor, it is completely naked-eye observation; (3) it helps students intuitively understand the diffracting and imaging processes; (4) the resolving power meets the requirements for teaching purposes. [ABSTRACT FROM AUTHOR]