Hole Pairs Research Articles

Fabrication of ternary Bi2S3/BiVO4/g-C3N4 composite material for enhanced photocatalytic degradation of antibiotics

Antibiotic contaminants are known to pose a serious threat to the human health and environment, thus a great deal of effort has been made to develop destruction technologies for antibiotic treatment in the water environment. Photocatalytic oxidation technology is regarded as one of the most promising strategies for decomposing antibiotics from water. In this work, ternary Bi2S3/BiVO4/g-C3N4 composite material is dexterously designed and synthesized to obtain the enhanced photocatalytic performance for tetracycline (TC) degradation via a facile strategy. Therein, the optimal Bi2S3/BiVO4/g-C3N4 material showed the excellent degradation efficiency under visible light irradiation in comparison to the nude g-C3N4 and BiVO4/g-C3N4 photocatalysts, and it can continuously degrade the TC pollutant in 90 min and achieve a degradation percentage of 80.7 %. The designed materials can not only intensify photo-absorption efficiency of g-C3N4 material, but also improve its separation and transfer efficiency of photo-generated charge carriers, which is attributed to the incorporation of BiVO4 and Bi2S3 materials. The active species trapping experiments verified that the superoxide radicals (•O2−) is the main active species, and holes (h+) also played an important role in the Bi2S3/BiVO4/g-C3N4 system. Furthermore, the photoelectrochemical measurement (PEC) clearly demonstrated that the incorporation of BiVO4 and Bi2S3 materials could accelerate the separation and transfer of photo-generated electron and hole pairs. As expected, our present work could spark new inspirations to further develop the efficient photocatalysts for solar energy conversion.

Hydrothermally synthesized Nb -doped TiO2 nanosheets for efficient removal of methylene blue dye on photocatalytic performance

In this work, Niobium-doped (1%, 3%, and 5%) titanium dioxide (Nb-TiO2) nanosheets were successfully formed via the hydrothermal route and further characterized using TEM, XRD, XPS and UV–vis absorption spectroscopy techniques. Phase purity and structural information of the prepared materials were analysed by XRD measurements. The band gap values ranged from 3.27 to 2.98 eV as Nb doping increased, leading to improved photocatalytic activity by creating new energy levels close to the conduction band. The XPS results confirm the amalgamation of Nb5+ ions into TiO2 without affecting the crystallinity, structure or orientation of the occurrence of oxygen vacancies. In 3% Nb-doped TiO2, the degradation efficiency for removing (Methylene blue) MB dye increased by ∼96% for the removal of MB dye within 70 min in comparison to pure and other doped TiO2 catalysts The better photocatalytic activity of 3% Nb-TiO2 is due to the longer time between electron–hole pairs before they recombine into one pair. Hydroxyl radicals (HO•) and superoxide radicals (O2 •−) are the primary reactive entities responsible for the deterioration of MB dye. Therefore, incorporating Nb into TiO2 nanostructures represents an auspicious material for the decomposition of hazardous and toxic pollutants in aquatic environments.

The Intrinsic Relationship between Photoluminescence and Photocatalysis of MMoO4/MWO4 (M = Mg, Ca, Sr and Ba) Heterojunctions: Heterojunction Construction, Mechanism Insight and Development Tendency.

The migration behavior of electron and hole pairs determines both photoluminescence and photocatalytic activity, which are two distinct properties of semiconductor materials. The photoluminescence and photocatalytic activity of semiconductor materials also exhibit strong method-dependent behavior under the influence of synthesis methods. In this review, the synthesis methods of MMoO4, MWO4 and MMoO4/MWO4 (M = Mg, Ca, Sr and Ba) heterojunction composites and their photoluminescence and photocatalytic activities are reviewed for the first time. The effects of different M ions on the photoluminescence and photocatalytic activity of MMoO4/MWO4 heterojunction composites are also reviewed. There is also a discussion about the intrinsic correlation mechanism between photoluminescence and photocatalytic activity. Different M ions result in different coordination environments in MMoO4/MWO4 heterojunction composites, which leads to different photoluminescence and photocatalytic mechanisms of different MMoO4/MWO4 heterojunction composites. This review provides theoretical reference and technical guidance for future research on MMoO4/MWO4 heterojunction composites.

Magnetic-field-induced activation of S-scheme heterojunction with core–shell structure for boosted photothermal-assisted photocatalytic H2 production

Photocatalytic H2 production through water splitting using semiconductor photocatalysts offers an economical and efficient approach to generate H2 with minimal environmental pollution to alleviate the energy crisis. Maximizing the utilization of the solar spectrum and essentially accelerating the separation and transfer of photo-generated electrons are crucial for enhancing the activity of the photocatalytic H2 production systems. Herein, Mn3O4@ZnIn2S4 (MO@ZIS) core–shell heterojunction photocatalysts were meticulously designed using a convenient water bath method to obtain a system that can achieve highly efficient photothermal-assisted photocatalytic H2 production induced by a magnetic field (MF). Remarkably, the optimal photocatalytic H2 production rate up to 33.29 mmol h−1 g−1 under the effect of applied MF with an apparent quantum efficiency (AQE) of 19.93 % at 420 nm were obtained over the optimal MO@ZIS-30 photocatalyst. The substantial enhancement of the photocatalytic activity in the MO@ZIS system was attributed to the synergy of magneto-thermal effect induced by the magnetic field and the strong photo-thermal effect exhibited by MO, which significantly increases the heterojunction surface temperature of the photocatalyst and promotes the separation and transfer of photo-induced electron hole pairs, thus accelerating the surface hydrogen evolution dynamics. Furthermore, the S-scheme heterojunction formed between MO and ZIS in MO@ZIS core–shell heterojunction optimizes the carrier transfer path. This study presents an effective approach for the effective utilization of the multi-field synergistic enhancement of photocatalytic activity.

Band engineering for building cascading charge transport channels in ternary CdS-based nanorod array photoanode toward efficient photoelectrochemical H2 generation

A novel CdS/CdSe/Cu2O nanorod array (NRA) photoelectrode with cascading charge transport channels was designed for the first time to remarkedly boot photoelectrochemical (PEC) hydrogen generation under visible light illumination with zero bias. This ternary photoelectrode was constructed by modifying CdS nanorod arrays with n-type CdSe and p-type Cu2O nanoparticles, successively. In this novel photoanode, CdSe and Cu2O with small band gap not merely highly heighten the visible light absorption capacity of CdS, but more importantly integrate with CdS to build cascading charge transport channels at the CdS/CdSe and CdSe/Cu2O interfaces, dramatically facilitating the separation and transport efficiency for photoexcited electron and hole pairs. The CdS/CdSe/Cu2O NRA photoelectrode gains an obvious hydrogen generation rate of 193.2 μmol·h−1, 8.2 times higher than that of bare CdS NRA photoelectrode. The remarkably enhanced PEC hydrogen production for the CdS/CdSe/Cu2O NRA photoanode can be ascribed to effective solar energy utilization and charge carrier separation.

Bulk photovoltaic effect in Cu-doped LiNbO3 single crystals with controlled oxidation state

We investigate the bulk photovoltaic (PV) effect of Cu-doped LiNbO3 single crystals with various oxidation states of Cu. The Cu-doped samples exhibit the PV response under below-bandgap excitation, and the onset of photocurrent shifts depending on partial oxygen pressures (pO2) during the annealing treatment. Open-circuit voltages (V oc) under simulated sunlight (AM 1.5 G) illumination are changed by pO2, and crystals annealed at pO2 = 1.0 × 10−10 atm exhibit the highest V oc of 1700 V. Moreover, density functional theory (DFT) calculations for Cu-doped LiNbO3 cells with Cu2+ on the Li site and the Nb site indicate that half-filled gap states derived from 3d orbitals of Cu are formed within the bandgap. Based on Glass coefficients obtained by the analyses of polarization angle-dependent photocurrent densities and the DFT calculations, we consider that Cu2+ on the Li site is the major active site for the generation and separation of electron–hole pairs under visible light at hν = 2.4 eV.

Vibrational, optical, and photocatalytic properties of ZnO/layered carbon nanocomposite synthesized by ball milling

ZnO/layered carbon nanocomposites with varied sizes of ZnO nanoparticles (NPs) were synthesized by mechanical milling of mixture of ZnO NPs and carbon NPs. The NP size of ZnO was controlled with average particle sizes about 19.33, 21.87, 24.21, and 27.89 nm by varying the concentrations of carbon NPs viz 0, 2, 5, and 10 weight percent, respectively, in the mixture. Presence of carbon with ZnO in the form of composite also resulted in the enhanced shift of the band gap of ZnO due to the optical transitions in the impurity states or presence of carbon as compared to the ZnO size change alone. Additionally, the enhancement of absorbance in the visible region with an increase in carbon content was observed. Such an increase in absorbance can enhance the photocatalytic activity of ZnO NPs. Raman bands for ZnO NPs also were found to shift faster in the presence of layered carbon. The quenching of visible photoluminescence emission of ZnO NPs with an increase in concentration of carbon NPs in the composite indicated the phenomenon associated with transfer of electrons from ZnO to layered carbon helping the separation of photo-generated electrons and holes in ZnO and can lead to enhancement of the photocatalytic activity of ZnO NPs. In the photocatalytic studies, it was observed that the degradation of methylene blue (MB) dye was significantly enhanced by the increase of content of layered carbon in the nanocomposite. The sample containing 10% carbon showed the highest adsorption in dark conditions which was up to 60% of the starting strength and this was further enhanced to 88% in the presence of UV radiation. Enhanced adsorption of MB dye and the effective separation of electron–hole pairs due to charge transfer were believed to be the main causes behind such kind of improvement in the photocatalytic effects.

Oxalic Acid-Assisted Photo-Fenton Catalysis Using Magnetic Fe3O4 Nanoparticles for Complete Removal of Textile Dye

Textile industry effluents contain several hazardous substances, such as dye-containing effluents, which pose environmental and aesthetic challenges. Presently, the microbial-based remediation process is in use. This study investigated the application of ferrous–ferric oxide (Fe3O4) nanoparticles, a readily formulated nanoadsorbent, to remove scattered dye molecules from industrial effluents. The ferrous–ferric oxide nanoparticles were prepared using a chemical co-precipitation method. The nanoparticles had 26.93 emu g−1 magnetization, with sizes smaller than 20 nm, and possessed a highly purified cubic spinel crystallite structure. The catalytic activity of the iron oxide depended on the dose, photocatalytic enhancer, i.e., H2O2 level, pH of the reaction medium, and dye concentration. We optimized the Fenton-like reaction to work best using 1.0 g/L of ferrous–ferric oxide nanoparticles, 60 mM oxalic acid at pH 7.0, and 60 ppm of dye. Iron oxides act as photocatalysts, and oxalic acid generates electron–hole pairs. Consequently, higher amounts of super-radicals cause the rapid degradation of dye and pseudo-first-order reactions. Liquid chromatography–mass spectrometry (LC-MS) analysis revealed the ferrous–ferric oxide nanoparticles decolorized and destroyed Disperse Red 277 in 180 min under visible light. Hence, complete demineralization is observed using a photo-Fenton-like reaction within 3 h under visible light. These high-capacity, easy-to-separate next-generation adsorption systems are suggested to be suitable for industrial-scale use. Ferrous–ferric oxide nanoparticles with increased adsorption and magnetic properties could be utilized to clean environmental pollution.

Reinforced Electrons Transfer and Capture in S‐Scheme TiO2@Co(OH)F‐Pt Heterojunction for Excellent Solar Hydrogen Evolution

AbstractTiO2 with the merits of non‐toxicity, high stability, strong redox capability, and low cost, has garnered considerable attention in the fields of renewable energy. However, the practical application is limited by the rapid recombination of photogenerated electron–hole pairs, posing a challenge to enhance electron utilization without compromising catalytic activity. Herein, S‐scheme TiO2@Co(OH)F‐Pt heterojunction through a simple hydrothermal and photo‐deposition method is constructed. The experimental tests and theoretical computation indicate that Co(OH)F possesses a smaller work function and a more negative conduction band (CB) position, significantly accelerating the separation of photogenerated charge carriers. Furthermore, the built‐in electric field, band bending between TiO2 and Co(OH)F, and the electron sink of Pt nanoparticles, facilitate the reduction of protons to hydrogen. The as‐prepared TiO2@Co(OH)F‐Pt exhibits high‐performance solar hydrogen evolution with an evolution rate of 1401 µmol h−1. The apparent quantum yield (AQY) is determined to be 22.8% at a single wavelength of 365 nm. After reacting 12 h for three cycles, no noticeable performance degradation occurs, showing good stability of the catalyst. This work provides a rational strategy for the design of heterojunction photocatalysts for driving the production of new energy and useful chemicals.

Nonvolatile photoelectric memristor for reconfigurable Boolean logic operation and data storage

Photoelectric memristors have the advantages of highly parallel computing and large-scale interconnection, which provides a promising method for reconfigurable logic operations and greatly promotes the development of new memory computing technology. In this paper, a photoelectric memristor was fabricated using natural gelatin and water-soluble CdSe/ZnS quantum dots with a shell structure. Under light stimulation, the device undergoes photoelectric effects in the dielectric layer, generating electron–hole pairs and causing the device to transition from a high-resistance state to a low-resistance state. Seven nonvolatile logic functions are achieved using three wavelengths of light excitation devices. Compared with traditional electrically controlled memristors, emerging photoelectric memristors are more attractive because they can integrate the advantages of photons and electrons.

Enhanced optical properties of BiVO4 photoanode with subwavelength moth-eye structure fabricated via e-beam evaporation and direct printing

Photoelectrochemical (PEC) water splitting, which harnesses solar radiation (an infinite energy source) for clean hydrogen production without carbon-dioxide emissions, is an ideal eco-friendly energy technology. The core reactions in PEC water splitting, involving the oxidation and reduction of water, are driven by electron–hole pairs generated through solar energy absorption. Consequently, the light-absorption efficiency emerges as a critical parameter in PEC devices. Conventional thin-film-type photoanodes, however, grapple with limited absorption due to their high reflectance, hindering absorption and carrier separation efficiency. Conversely, moth-eye-structured photoanodes exhibit an anti-reflection effect stemming from their subwavelength structure, markedly enhancing light-absorption efficiency. In this study, we present the design and fabrication of a densely packed moth-eye-structured bismuth vanadate (BiVO4) (M-BVO) photoanode, which is engineered to possess superior light absorption properties. The photoanode was fabricated via direct printing, electron-beam evaporation, and Vanadium calcination processes. The light absorption of the resulting M-BVO photoanode increased to approximately 92 % within the 300–500 nm wavelength range, with the absorption efficiency (ηabs) surging to 82.9 %. This represents a 23.5 % enhancement compared to its flat BiVO4 counterparts. Impressively, the photocurrent density of M-BVO reached 2.98 mA cm−2 at 1.23 VRHE, 37.6 % higher than that of flat BiVO4. These results indicate that the PEC efficiency can be significantly increased through moth-eye structuring, emphasizing the indispensable role of nanostructure research in the manufacture of high-efficiency photoanodes.

Construction of oxygen-doped g-C3N4/BiOCl (S-scheme) heterojunction: Efficient degradation of tetracycline in wastewater

Graphitic phase carbon nitride (g-C3N4) demonstrates significant promise in the photocatalytic degradation of organic pollutants, but the rapid recombination of photogenerated electron-hole pairs seriously restricts its degradation capacity. In this study, an innovative heterostructural anion regulation strategy based on g-C3N4 was proposed to significantly enhance the degradation performance of tetracycline. Initially, we regulated the electron configuration of g-C3N4 through O doping to optimize the active sites at the reaction interface. Subsequently, the S-scheme heterojunction was constructed by introducing BiOCl to stimulate the pumping effect and form efficient build-in electric field electron channels. The oxygen-doped g-C3N4/BiOCl (OCN/BiOCl) heterojunction material obtained through aforementioned modification exhibited a degradation efficiency of 89.33 % towards 20 mg·L−1 tetracycline (90 min light reaction, 30 min dark reaction), which was 2.5 times that of conventional g-C3N4 catalyst. In particular, density functional theory calculations and ultraviolet photoelectron spectroscopy jointly revealed the unique chemical environment and electronic structure between OCN and BiOCl due to the formation of the build-in electric field, thereby providing enhanced pathways for the migration of photogenerated currents. Meanwhile, the heterostructure significantly reduced the transport distance of photo-induced charge and minimizes the internal transmission resistance. It enhances the efficiency of separating photogenerated electrons and hole pairs, which is the key mechanism for greatly improving the photocatalytic degradation performance of OCN/BiOCl materials. In summary, the hetero-anion regulation strategy proposed in this study addresses the issue of rapid recombination of photogenerated charges in g-C3N4, providing a new perspective for efficient control of organic pollutants in the environment driven by g-C3N4 photocatalyst.

Strongly coupled magneto-exciton condensates in large-angle twisted double bilayer graphene

Excitons, pairs of electrons and holes, undergo a Bose-Einstein condensation at low temperatures. An important platform to study excitons is double-layer two-dimensional electron gases, with two parallel planes of electrons and holes separated by a thin insulating layer. Lowering this separation (d) strengthens the exciton binding energy, however, leads to the undesired interlayer tunneling, resulting in annihilation of excitons. Here, we report the observation of a sequences of robust exciton condensates (ECs) in double bilayer graphene twisted to ~ 10° with no insulating mid-layer. The large momentum mismatch between two graphene layers suppresses interlayer tunneling, reaching a d ~ 0.334 nm. Measuring the bulk and edge transport, we find incompressible states corresponding to ECs when both layers are in half-filled N = 0, 1 Landau levels (LLs). Theoretical calculations suggest that the low-energy charged excitation of ECs can be meron-antimeron or particle-hole pair, which relies on both LL index and carrier type. Our results establish a novel platform with extreme coupling strength for studying quantum bosonic phase.

New pairing mechanism via chiral electron–hole condensation for non-BCS superconductivity

A novel chiral electron–hole (CEH) pairing mechanism is proposed to account for non-BCS superconductivity. In contrast to BCS Cooper pairs, CEH pairs exhibit a pronounced affinity to antiferromagnetism for superconductivity. The gap equations derived from this new microscopic mechanism are analyzed for both s- and d-wave superconductivity, revealing marked departures from the BCS theory. Unsurprisingly, CEH naturally describes superconductivity in strongly-correlated systems, necessitating an exceedingly large coupling parameter (λ>1 for s-wave and λ>π/2 for d-wave) to be efficacious. The new mechanism provides a better understanding of various non-BCS features, especially in cuprate and iron-based superconductors. In particular, CEH, through quantitative comparison with experimental data, shows promise in solving long-standing puzzles such as the unexpectedly large gap-to-critical-temperature ratio Δ0/Tc, the lack of gap closure at Tc, superconducting phase diagrams, and a non-zero heat-capacity-to-temperature ratio C/T at T=0 (i.e., the “anomalous linear term”), along with its quadratic behavior near T=0 for d-wave cuprates.

Enhanced simulated sunlight photocatalytic performance in K2Ti6O13/g-C3N4 heterojunction

In this study, K2Ti6O[Formula: see text] (KTO) nanowires were doped with carbon (CKTO) via a novel solid-phase approach at 800∘C for the first time using ethanol, KF, and TiO2. In addition to the lower sintering temperature, a shorter insulation period was achieved compared to the conventional solid-phase method. Furthermore, by combining and calcining CKTO and g-C3N4, a CKTO/g-C3N4 heterojunction composite was produced. The rate at which CKTO/g-C3N4 photocatalytically degraded methylene blue was higher than those of pure CKTO and g-C3N4. Our study indicates that adding g-C3N4 enhances photocatalytic performance by reducing the recombination rate of photogenerated electron–hole pairs and narrowing the bandgap of the CKTO/g-C3N4 heterostructure. This paper presents a novel method for creating KTO composites in an eco-friendly and productive manner for the photocatalytic degradation of organic colors.

NaSCN‐Induced Cyano‐Rich Porous Graphitic Carbon Nitride with Sodium Dopant and Nitrogen Vacancies for Enhanced Photosynthesis of Hydrogen Peroxide

AbstractDefect engineering has been considered as an efficient and facile tactics to optimize the bandgap structure and improve the oxygen adsorption ability of graphitic carbon nitride (g‐C3N4). Herein porous g‐C3N4 with nitrogen vacancies and sodium dopant as well as cyano (─C≡N) groups has been successfully constructed by direct pyrolysis of melamine in the presence of cyano‐rich sodium thiocyanate (NaSCN). Moreover, the incorporation of NaSCN is interestingly found to induce the relative high content of ─C≡N groups compared to other inorganic sodium compounds (NaCl, NaOH, and Na2SO4), which has been experimentally demonstrated to be beneficial for extending the light absorption range and promoting the efficient separation of photo‐generated electron–hole pairs as well as improving the oxygen adsorption ability. Benefiting from the above features, the optimal photocatalyst exhibits high H2O2 yield of 438.2 µm within 4 h and excellent cyclic stability.

Integrated photodetectors embedded within fiber laser based on hybrid rGO:ZnO nanostructures

Online power monitoring is helpful in fiber-optic communication applications. This report introduced an innovative all-fiber photodetector based on the polished side of an arc-shaped fiber for the optical signals’ in situ measurements. For this purpose, a metal-semiconductor–metal photodetector was designed with multiple interdigitated metal fingers of gold electrodes. A waveguide structure containing polymethyl methacrylate (PMMA), graphene layers, and zinc oxide nanostructures was developed and covered over the arc-shaped fiber. Due to the PMMA’s refractive index (n = 1.4905), the evanescent field of propagating mode was drawn out of the core, thus increasing the light interaction with semiconductor nanostructures. To study the influence of graphene flakes on the optoelectrical behavior of zinc oxide nanostructures, a suspension of graphene oxide (GO) and ZnO nanorods was synthesized and transferred onto the PMMA thin film, which was deposited on the polished side of the arc-shaped fiber. The morphological analysis indicates the formation of ZnO nanorods with different orientations, and these nanorods have the potential to enhance incident photon trapping greatly. Upon photon exposure, the guiding photons in the fiber evanescently coupled with the deposited nanostructures, and the photoexcited electron–hole pairs were generated in the semiconductor material. Using applied voltage across the interdigitated electrodes, the generated excitons were separated and increased the photocurrent, which was monitored precisely by source-measure equipment. The optoelectrical properties of fabricated devices showed that incorporating graphene layers can improve the photon detection performance of the fabricated all-fiber photodetectors based on ZnO nanostructures.

Assembly of 2D/2D Bi2WO6/Boron-doped g-C3N4 Z-type heterojunction photocatalysts for efficient antibiotic adsorption and degradation

The photocatalytic heterojunction systems have shown remarkable development in improving the efficiency of visible-light absorption and photocarriers separation. Herein, we successfully engineered efficient 2D/2D Bi2WO6/Boron-doped g-C3N4 (BiWO/BCN) architectures as Z-type heterojunction photocatalysts with different BiWO to BCN ratios for degradation of antimicrobial drug sulfamethoxazole (SMX) under visible illumination. The SMX degradation using the optimized 40%BWO/BCN sample was obviously enhanced, and the degradation rate was 99.3 % after 120 min of irradiation. Its degradation efficiency was 6.5-, 3.2-, and 2.9-times better than that of BiWO, CN, BCN, and, respectively. The significantly boosted performance of the BiWO/BCN photocatalyst was credited to the effective separation of photo-excited electron and hole pairs. The SMX photodegradation pathways have been explained with a complete assessment of the active species, which showed the major role of •O2− and electrons. The reusability tests proved the high photostability of 40%BiWO/BCN sample throughout 5 sequential cycles (only 3.8 % reduction was witnessed). Therefore, this work presents an innovative photocatalyst combination for green degradation of SMX antibiotic.

Hunting of “two birds with one arrow” strategical design of Nb doped WO3 decorated on the BN nanosheet and their enhanced photocatalytic degradation of Rose Bengal dye and Chloramphenicol drug

In the present work, “Killing two birds (RB and CAP) with one arrow (Nb/WO3/BN)” plan of action was performed for the photocatalytic degradation of organic dye of Rose Bengal (RB) and organic drug of Chloramphenicol (CAP) was degraded under visible light irradiation with the active catalyst of Nb/WO3/10 % BN composite for first time. The as-prepared Nb/WO3 was functionalized with thin-sheet structure of BN nanocomposite was synthesized via acid precipitation method followed by ultra-sonication method. The effective formation of Nb/WO3/BN were characterized by using XRD, UV-DRS, XPS, SEM-EDS, TEM, Photoluminescence (PL) and electrochemical impedance spectroscopy (EIS). The XRD, UV-DRS results clearly revealed that formation of ternary phases in the composites. Formation of ternary composite also confirmed by the XPS analysis. The morphology of WO3, Nb/WO3 and BN were examined by the SEM analysis. Furthermore, the inner morphology of cubic structure of WO3 nanoparticles and Nb/WO3 were decorated on the surface of the BN nanosheet were approved by TEM analysis. Interestingly, photocatalytic degradation of RB revealed by 94.31 % within 60 min as well as CAP degraded 95.13 % within 60 min by Nb/WO3/10 % BN ternary composite under visible light irradiation. Meanwhile, the different prepared photocatalyst, Nb/WO3/10 % BN was found to be the most efficient photocatalyst for degradation of RB and CAP. This results ascribed to the 30 mg of the photocatalyst and 10 mg/L concentration were optimum loading for the degradation of RB and CAP. Scavenger studies were also confirmed in order to understand the mechanism of photodegradation process. It was noted that electrons and holes pair are generated by irradiation of light, followed by (.OH) radical plays a crucial role for the photodegradation mechanism. The active photocatalyst Nb/WO3/10 % BN shows a good stability at room temperature and it can be recycled and reused up to five successful cycles without the major loss in their performances. Therefore, these work revealed that, the best sequence of Nb/WO3/10 % BN nanocomposite is new plan of action for photodegradation of RB and CAP.

Origin of Optical Gain in Narrow ZnO Microrods with Whispering Gallery Modes

Due to sufficiently high lasing thresholds, stimulated emission in relatively small ZnO microcrystal lasers is often considered to be fed by an inverted electron–hole plasma (EHP). In this study, the nature of optical gain in such emitters is investigated using ZnO microrods 1–6 µm in diameter synthesized by a modified thermal evaporation method and exhibiting whispering-gallery mode (WGM) lasing in the near ultraviolet range. It is demonstrated that optical gain in these objects is not a consequence of population inversion of the EHP at either low or room temperatures. Instead, the primary gain mechanism is the process of scattering of electron–hole pairs by free electrons. Unlike the case of large ZnO WGM microcavities, in small-diameter microrods this process turns out to be dominant over a wide temperature range.