Light Absorption Ability Research Articles

Synthesis of Mn-doped hollow octahedron ZnIn2S4 to enhance photocatalytic hydrogen production performance utilizing metal-organic framework as template.

Designing semiconductor photocatalysts with unique structures can improve the transfer efficiency of solar energy to hydrogen (H2). In this study, a dual modification method of element doping and morphological control was used. The Mn-doped hollow octahedron ZnIn2S4 (ZHO-Mn) was synthesized by a simple one-pot solvothermal method using the octahedral Mn-based metal-organic framework (Mn-MOF) as a template. Experiments and theoretical calculations show that the ZHO-Mn has additional active sites, strong light absorption ability and good photoelectric performance. The H2 production performance of optimized ZHO-Mn10 was the best (11.9 mmol h-1 g-1), which was 7.4 times that of monomer ZnIn2S4 (1.6 mmol h-1 g-1). This study provides a new one-step method for the dual control of doping and morphology of ZnIn2S4 photocatalyst.

Synthesis, photocatalytic activity for tetracycline degradation under visible light, and kinetic study of Ag/AgCl/ZIF-11 nanocomposite.

For the first time, Ag/AgCl/zeolitic imidazolate framework-11 nanocomposite (Ag/AgCl/ZIF-11) as photocatalyst was synthesized and investigated on tetracycline (TC) degradation under visible light. ZIF-11 (Z), Ag/AgCl (A), and four composites (AZ0.1Vis, AZ0.1UV24, AZ0.2UV12, AZ0.2UV24) were made and characterized by XRD, FTIR, Raman, BET, SEM, EDS, XPS, and DRS analysis. The characteristic peaks of ZIF-11 and Ag were observed at 4.3 and 38.2° in the XRD pattern of AZ0.2UV24, respectively. A good distribution of Ag/AgCl on the surface of ZIF-11 was observed by FESEM of AZ0.2UV24. The improvement of visible light absorption ability and reduced e-/h+ recombination of AZ0.2UV24 were confirmed by DRS and PL, respectively. The photocatalytic degradation of TC was described using the zero-order kinetic model with a degradation efficiency of 95.4%. The stability and reusability of AZ0.2UV24 were investigated during three consecutive cycles. Finally, the results of this study provide convincing evidence for using Ag/AgCl/ZIF-11 as highly efficient photocatalysts for removing TC from aqueous solutions.

Hierarchical Porous Silicon-Carbon Encapsulated Phase Change Materials for Efficient Photothermoelectric Conversion.

Scale-up applications in solar energy storage of phase change materials (PCMs) are hindered by the limitation of solid-liquid leakage and the lack of light absorption ability. Porous silicon-carbon (PSC) with a high specific surface area was prepared from a phytolith (Phy) silicon-carbon ore by the alkali-melting method, taking advantage of the natural mineral rich in light-trapping carbon structures in Phy. Stearic acid (SA) was impregnated into the PSC to produce integrated photothermal composite phase change materials (SA/PSC). The performance analysis of the form-stable PCMs (FSPCMs) shows that SA/PSC800 has good shape stability and excellent photothermal conversion efficiency and storage capacity, with a high photothermal conversion efficiency of 98.87%. The enthalpy change of the phase change was weak after 200 cycles, indicating good cycle regeneration. A solar thermoelectric generator (STEG) system for light-heat-electric energy conversion and storage was constructed using SA/PSC800 as a hot-side material integrated with a thermoelectric generator. Under a simulated solar light intensity of 200 mW/cm2, the output power generated by the STEG system through the Seeback effect can keep the small bulb and LED glowing for 21 and 18 s, respectively. Therefore, the prepared composite FSPCMs have promising applications in battery-coupled photovoltaic power generation.

Photoelectrochemical Properties of Water Splitting Reactions Using NiO/InGaN Photoanodes with Different InGaN Thicknesses and Characteristics in Gas-Phase CO2 Reduction Reactions

To improve the durability of water splitting reaction, we have developed a NiO/AlGaN photoanode in which highly crystalline AlGaN grown on a GaN substrate is covered with a protective layer of NiO [1]. InGaN, a mixed crystal of GaN and InN, has a narrower band gap than AlGaN or GaN, and it has been reported that InGaN photoanodes have higher solar-to-hydrogen conversion efficiencies compared with ones made from those materials [2]. To improve their efficiency further, it is necessary to increase the photocurrent by increasing the thickness of InGaN with the aim of maximally absorbing the light transmitted into it. However, increasing the thickness may increase dislocations that occur when growing the InGaN layer. In this study, to investigate the effect of the thickness of the InGaN layer on photoelectrochemical properties, we measured the photocurrent in a water splitting reaction using NiO/InGaN photoanodes with different InGaN thicknesses. In addition, we measured the CO2 reduction products after 350 h of continuous light irradiation using the best-performing photoanode (NiO/InGaN on GaN substance) in gas-phase CO2 reduction reaction system. In0.02Ga0.98N (thickness: 100, 200, 300, 400, 500, 600, and 700 nm)/n-GaN heterostructures were grown by metal organic chemical vapor deposition on a sapphire substrate. The InGaN layer had a composition gradient in which the In composition increased from the InGaN/n-GaN interface toward the InGaN surface [2]. The thickness of In0.02Ga0.98N was evaluated by secondary ion mass spectroscopy. The light transmittance was measured with a spectrophotometer, and the arithmetic average roughness (R a) of the In0.02Ga0.98N surface was evaluated with atomic force microscopy. Ni thin film was fabricated on the In0.02Ga0.98N surface by vacuum evaporation. The sample was then heat-treated at 563 K for 60 min in air to form the NiO layer [1]. NiO/In0.02Ga0.98N/n-GaN as the photoanode and Pt wire as the cathode were immersed in 1 mol/L NaOH and the water splitting reaction proceeded. The photocurrent was measured with a potentio-galvanostat under application of 1.7 V and irradiation with a Xe lamp adjusted to the same intensity as AM1.5G (λ ≤ 374 nm). Next, to quantify the CO2 reduction products, NiO/In0.02Ga0.98N (thickness: 500 nm)/n-GaN on GaN substrate was prepared as the photoanode. Thermocompression was used to prepare a composite sheet using gold fiber as a cathode and NafionTM as an electrolyte membrane [3]. The sheet was set so as to separate the oxidation and reduction chambers. 0.5 mol/L CsOH was used in the oxidation chamber and CO2 was directly supplied at 45 sccm to the cathode in the reduction chamber. The photocurrent was measured under similar conditions as the water splitting reaction. The produced gas was determined every 10 h with gas chromatography, and the produced liquid after 350 h was determined with high-performance liquid chromatography. The photocurrent density measured 1 min after the light irradiation ceased increased with thickness from 100 to 500 nm, while it decreased for thicknesses more than 500 nm. The maximum photocurrent density was 0.81 mA/cm2. It was considered that the light absorption ability of the In0.02Ga0.98N layer increased with its thickness. Moreover, since R a increased, it was thought that the crystallinity of the In0.02Ga0.98N decreased as its thickness increased. These results indicate that increasing the In0.02Ga0.98N thickness increases the number of generated electron-hole pairs because of the increased light absorption. On the other hand, these also indicate that the decrease in crystallinity increases the recombination probability of electron-hole pairs. Here, it was assumed that the photocurrent density reached its maximum when the thickness was 500 nm. The results of measuring the CO2 reduction products using the NiO/In0.02Ga0.98N (thickness: 500 nm)/n-GaN on the GaN substrate photoanode and the composite sheet are shown in Fig. 1. CO and HCOOH were detected, with the cumulative amounts of product per photoanode area being 3237 and 263 µmol/cm2, respectively, after 350 h. The average Faradaic efficiencies of CO and HCOOH during 350 h were 83 and 6%, respectively. The cumulative amount of O2 was 1865 µmol/cm2, and the average Faradaic efficiency during 350 h was 96%. Therefore, the NiO/In0.02Ga0.98N (thickness: 500 nm)/n-GaN on GaN substrate was found to be an effective photoanode for a gas-phase CO2 reduction reaction system with high efficiency and durability.[1] Y. Uzumaki et al., PRiME 2020, L04-3054 (2020).[2] K. Ohkawa, ECS Transactions 66 (1), 135-138 (2015).[3] S. Sato et al., 2023 ECSJ Fall Meeting, S2-1-09 (2023) (in Japanese).Fig. 1. Amount of CO, HCOOH, H2, and O2 measured using NiO/In0.02Ga0.98N (thickness: 500 nm)/n-GaN on GaN substrate photoanode versus irradiation time. Figure 1

Electrofluorochromic Devices Based on Electrochemical Valance Change of Europium Complex in Polyether Matrices

Chromogenic materials, in which optical properties such as luminescence and absorption are altered by external stimuli such as light, heat, and electricity, have potential applications in chemical sensors, biochemical labels, molecular memory, and display devices. Electrofluorochromic (EFC) materials, in which wavelength and/or intensity of their photoluminescence are controlled by electrochemical redox reactions, are innovative materials because they can rapidly and repeatedly convert electrical inputs into visual signals. These EFC phenomena were reported by using small molecules, conjugated polymers, inorganic compounds, and luminescent metal complexes. Among the luminescent metal complexes, the lanthanide(III) complexes are composed of a luminescent center of Ln(III) ions and surrounding antenna ligands with sufficient light-absorbing ability. They have attractive photoluminescence properties such as characteristic and narrow emission bands in the visible-near infrared (Vis-NIR) region, long emission lifetimes, and high transparency in the visible region due to the large pseudo-Stokes shift. In particular, Eu complexes have relatively stable trivalent (Eu3+) and divalent (Eu2+) states. The Eu3+ state is characterized by intense and long-lived red luminescence induced by f–f transitions and is extensively applied to biosensors, light-emitting materials, etc. On the other hand, Eu2+ is known to show broad and blue luminescence induced by d–f transitions, from the excited state of 4f65d1 to the ground level state of 8S7/2 (4f7), and the emission of Eu2+ in inorganic matrices is applicable to various phosphor materials. However, Eu2+ is unstable in common solutions, which complicates the observation of its luminescence in solution state. Therefore, this study aims to control the luminescence between Eu3+ and Eu2+ by electrochemical redox reactions. It is recognized that the blue luminescence of Eu2+ can be stabilized by polyethers, such as crown ethers and polyethylene glycols[1]. By this stabilization, the Eu2+ state was expected to produce stalely and repeatedly by the electrochemical reduction of Eu3+ in polyethylene glycol solutions. Considering the EFC reaction of Eu compounds, this study focuses on the β-diketonate Eu complex that exhibits superior red luminescence properties of the Eu3+ state.The solution was prepared by dissolving the lithium trifluoromethanesulfonate (LiCF3SO3) (500 mM) as the supporting electrolyte, β-diketone type Eu(III) complex (Eu(hfa)3(H2O)2) (10 mM) as the emitting material in polyethylene glycol (MW = 400, PEG400). A three-electrode electrochemical cell with ITO electrode as the working electrode, Pt wire as the counter electrode, and Ag/Ag+ as the reference electrode was prepared using the Eu complex solution, and the electrochemical reaction behavior of the Eu(III) complex and the changes in luminescence properties during the reaction were measured. Then two-electrode electrochemical device was fabricated by sandwiching Eu complex solution between the two ITO electrodes (ITO-ITO device) to evaluate photoluminescence (PL) properties under the application of reduction voltage.When the CV measurement using the constructed three-electrode cell structure, stable Eu2+/3+ reactions were not observed in the common electrochemical solvents (dimethyl sulfoxide, acetonitrile, and propylene carbonate). In contrast, relatively stable Eu2+/3+ changes were observed in the PEG400 electrolyte solution. This indicates that the electrochemically generated Eu2+ is more stable in the PEG400 solution than in the other solvents.The figure shows the emission spectra of the Eu(hfa)3(H2O)2 solution in the two-electrode ITO-ITO device under the application of reduction voltage. When a reduction voltage was applied for working electrode for 60 minutes, the emission bands of Eu2+ (430 nm) in the device significantly increased, and the red emission from Eu3+ (616 nm) simultaneously decreased as electrochemical reduction proceeded. Considering luminescence color, the intensity ratio of Eu2+ emission (430 nm, I 430) to Eu3+ emission (616 nm, I 616) was significantly improved using the two-electrode devices; the I 430 nm: I 616 nm ratio was 1: 100 for the three-electrode cell and 1: 2.5 for the two-electrode devices. Thus, changes in the luminescence color can be recognized by the naked eye after electrochemical reduction (Figure photos). These results show that electrochemical redox reaction of Eu complexes leads to a distinct change in luminescence color in PEG electrolyte by stabilizing Eu2+ state in liquid matrix. Figure 1

First-principles investigation on the structure, electronic, mechanical and optical properties of silver based perovskites AgBX3 (B=Be, Mg; X=Br and I)

Abstract The structure, mechanical, electronic and optical properties of Ag-based halides AgBX3 (B=Be, Mg; X=Br, I) were studied using first-principles approach for the first time. The elastic constants reveal that these materials are mechanical stability. The results of Pugh's ratio, bulk modulus, Poisson's ratio and anisotropy coefficients exhibit that these compounds are ductility, anisotropy, and ionic properties, and the hardness of beryllium compounds is larger than that of magnesium compounds. The band structure and density of states for AgBX3 show that AgBeBr3, AgMgBr3 and AgMgI3 compounds are indirect bandgap semiconductors, while AgBeI3 has metallic properties. The valence band of the AgBX3 is mainly dominated by Ag-d and X-p orbital electrons, and the conduction band is composed predominantly of B-p and X-s orbital electrons. The optical properties of AgBX3 were analyzed in the energy range 0-30 eV. It is found that AgBX3 has high transparency in visible light range and good ultraviolet light absorption ability, which reflects that AgBX3 can be employed as window and lens materials in visible light range and ultraviolet optical devices.

Synthesis of Photocatalyst Based on WO3 Applying for the Treatment of Tetracycline Antibiotics

In this paper, WO3/g-C3N4 photocatalysts were fabricated by ultrasonic-assisted hydrothermal method at different mole ratios of WO3/g-C3N4. Ultraviolet–visible absorption spectroscopy (UV-Vis DRS) and photoluminescence (PL) results indicated that WO3/g-C3N4 photocatalyst with the WO3/g-C3N4 mole ratio of 1/1 (WC-1) showed visible light absorption ability and prevented electron-hole recombination rate better than WO3, g-C3N4 and other composites. The photocatalytic activities of synthesized photocatalysts were investigated by the photocatalytic oxidation of tetracycline (TC) antibiotics under visible light. The degradation efficiency of TC in aqueous environment by the WC-1 was 79.35% after 180 minutes. This value was higher than those of other materials. The improvement in photocatalytic property of the WO3/g-C3N4 was due to the efficient generation of electrons and holes.

Constructing core–shell phosphorus doped MnCo2O4.5@ZIS for efficient photocatalytic hydrogen production from water splitting

Rational construction of core@shell heterostructured photocatalysts is the key to realize efficient hydrogen production from water splitting attributing to the accelerated photoinduced charges separation/transfer and enhanced light absorption ability. In this work, two-dimensional (2D) ZnIn2S4 (ZIS) nanosheets were in-situ grown on phosphorus doped MnCo2O4.5 (P-MnCo2O4.5) nanospheres to construct P-MnCo2O4.5@ZIS heterostructured photocatalysts for efficient photocatalytic hydrogen production. The optimized 6 wt% P-MnCo2O4.5@ZIS composite presents remarkable photocatalytic hydrogen evolution rate of 4197 µmol g−1 h−1 (8 times of single ZIS) along with excellent cycling stability, which is comparable to most previous reported ZnIn2S4-based or even noble-metal involved catalysts. The improved photocatalytic performance is resulted from the distinguished heterostructure and components of P-MnCo2O4.5@ZIS, in which the close contact interface facilitates the separation/transfer and inhibits the recombination of charges, and the uniform distribution of ZIS nanosheets on P-MnCo2O4.5 increases the active sites and fortifies the light absorption. The present work comes up with a prospective method for establishing core@shell ZIS-based heterostructured photocatalysts for efficient hydrogen generation.

Novel carbon nitride for efficient degradation of organic pollutants and value-added recycled plastics: Synergistic effects of nitrogen vacancies and Fe

The introduction of nitrogen vacancies (VN) and iron (Fe) single atoms sites significantly enhances the visible light absorption and charge transfer ability of carbon nitride (CN) catalysts. This paper presents the successful synthesis of a VN-rich, Fe single atoms incorporated CN, a catalyst that demonstrates exceptional degradation performance and cycling stability. The 2-mercaptobenzothiazole (MBT) removal rate by 20Fe-CN reached 99.51 % within just 11 min under visible light, and the catalyst maintained superior photocatalytic performance upon repeated use. Additionally, the 20Fe-CN/Photo/High-temperature system effectively converted polystyrene (PS) to benzoic acid (BA), achieving a BA yield of 19.73 % after 48 hours. Under visible light irradiation, the VN sites captured electrons and facilitated their rapid transfer to neighboring Fe sites, enhancing the photocatalytic redox processes. This study also identified ·O2- as the primary active species in the photocatalytic process. This research supports the development of diverse single-atom modified carbon nitride photocatalysts, holding significant potential for wastewater treatment and plastic resource recycling, and providing valuable insights for future photocatalysts in environmental remediation.

Visible light degradation of antibiotics catalyzed by nanoporous carbon/V2O5 nanocomposite: structural, optical and electrochemical properties

In this study, nanoporous carbon (NPC) decorated V2O5 (NPC/V2O5) nanocomposite synthesized by a hydrothermal technique using biomass-derived NPC nanoflakes towards the application of berberine hydrochloride (BH) dye degradation under visible light irradiation. The prepared samples were characterized by X-ray Diffraction (XRD), Raman spectroscopy, Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray (EDX), UV–Visible and Photoluminescence (PL) spectroscopy. Charge transfer resistance was measured by electrochemical impedance spectroscopy (EIS) and liner sweep voltammetry (LSV). XRD studies confirm the orthorhombic crystal structure of NPC/V2O5 nanocomposite. FE-SEM and TEM analysis validate their particle-like and sheet-like morphology of V2O5 and NPC respectively. Further, UV–visible DRS and PL spectra of the green synthesized NPC/V2O5 nanocomposite exhibited a low band-gap and reduced recombination rate compared to the pure counterpart which is better light-absorbing ability in the visible light region. Batch experiments represent the incorporation of NPC and V2O5 would lead to an increase the photocatalytic performance of NPC/V2O5 toward BH dye degradation. During the photocatalytic reaction, the NPC/V2O5 nanocomposite degraded rate around 97.7 % against BH dye within 80 min while pure V2O5 degraded 92.5 % of BH dye under same visible light irradiation time. Finally, the cyclic stability experiment exhibits the photocatalyst even stable after five consecutive tests.

Layer-by-Layer Deposition of Hollow TiO2 Spheres with Enhanced Photoelectric Conversion Efficiency for Dye-Sensitized Solar Cell Applications.

Fabricating photoanodes with a strong light-scattering effect can improve the photoconversion efficiency of dye-sensitized solar cells (DSSCs). In this work, a facile microwave hydrothermal process was developed to prepare Au@TiO2 core-shell nanostructures, and then the Au core was removed by etching, resulting in hollow TiO2. Morphological characterizations such as field emission scanning and transmission electron microscopy measurements have been used for the successful formation of core-shell and hollow TiO2 nanostructures. Next, we attempted to deposit the different-sized hollow TiO2-based microspheres simultaneously on the surface of small-sized TiO2 nanoparticles-based compact film as light-scattering layers via electrophoretic deposition. The deposited hollow TiO2 microspheres constitute bi- and tri-layers that not only improve the light-harvesting properties but also speed up the photogenerated charge transfer. Compared to commercial TiO2 compact film (4.75%), the resulting bi-layer and tri-layered films-based DSSCs displayed power conversion efficiencies of 6.33% and 8.08%, respectively. It is revealed that the deposited bi- and tri-layered films can enhance the light absorption ability via multiple photon reflection. This work validates a novel and controllable strategy to develop light-scattering layers with increased light-harvesting properties for highly efficient dye-sensitized solar cells.

Study on the optical properties of Sm3+ doped bismuth silicate crystals based on first principles

Abstract This study systematically investigated the effect of Sm3+ doping on the optical properties of bismuth silicate (Bi4Si3O12, abbreviated as BSO) crystals using first principles calculations based on density functional theory (DFT). By calculating the dielectric function, reflectivity, absorption coefficient, refractive index, conductivity, and energy loss function of BSO crystals under different Sm3+ doping ratios, we found that moderate Sm3+ doping can increase the dielectric function of BSO crystals, and the real part of the dielectric function represents the material’s ability to respond to the electric field, that is, the macroscopic polarization degree. Therefore, moderate Sm3+ doping enhances the polarization ability of BSO crystals. Simultaneously doping an appropriate amount can effectively enhance the conductivity and light (visible and infrared) absorption ability of BSO crystals, and reduce the energy loss between electrons in BSO crystals, thereby improving their luminescence performance. Specifically, when the Sm3+ doping ratio is 1/6, the optical properties of BSO crystals are significantly improved. These findings not only enhance the understanding of the mechanism of optical performance changes in rare earth ion doped BSO crystals, but also provide a theoretical basis for the development of new rare earth doped optical materials.

Visible Light Induced Photocatalytic Degradation of Diclofenac in Aqueous Solution Using Fabricated ZnO/g-C3N4 by Facile Calcination Technique.

The ability of the heterojunction between two distinct semiconductors with appropriately matched band gaps to improve the separation of photogenerated electron-hole pairs has been demonstrated to enhance photocatalytic activity. Hence, ZnO/g-C3N4 composites have been fabricated by the facile deposition and calcination of ZnO and g-C3N4. X-ray photoelectron spectroscopy, powder X-ray diffraction, and Fourier transform infrared spectroscopy confirm the formation of the composite. Scanning electron microscope, transmission electron microscope, and energy-dispersive X-ray spectroscopy morphological analysis reveal that ZnO was homogeneously spread over the g-C3N4 surface. UV-vis diffuse reflectance spectroscopy analysis shows the slightly enhanced visible light absorption ability of the composite. Photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopy analysis prove the higher charge separation of the composite during the irradiation of light. The composite shows admirable photocatalytic efficiency in the visible light-driven photocatalytic degradation of an aqueous diclofenac (DFC) solution. The superoxide anion radical (•O2 -) and hydroxyl radical (•OH) act as reactive species during the degradation reaction. Probable reaction mechanisms have been proposed.

Vitamin B6 Appended Polypyridyl Co(III) Complexes for Photo-Triggered Antibacterial Activity.

Three novel polypyridyl-Co(III)-vitamin B6 complexes viz., [Co(CF3-phtpy)(SBVB6)]Cl (Co1), [Co(anthracene-tpy)(SBVB6)]Cl (Co2), [Co(NMe2-phtpy)(SBVB6)]Cl (Co3), where 4'-(4-(trifluoromethyl)phenyl)-2,2':6',2''-terpyridine=CF3-phtpy, 4'-(anthracen-9-yl)-2,2':6',2''-terpyridine=anthracene-tpy;, 4-([2,2':6',2''-terpyridin]-4'-yl)-N,N-dimethylaniline=NMe2-phtpy, (E)-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylpyridin-3-ol=H2SBVB6 were successfully developed for aPDT (antibacterial photodynamic therapy) applications. Co1-Co3 exhibited an intense absorption band at ca. 435-485 nm, which is attributed to ligand-to-metal charge transfer and was beneficial for antibacterial photodynamic therapy. The distorted octahedral geometry of the complexes with CoIIIN4O2 core was evident from the DFT study. The visible light absorption ability and good photo-stability of Co1-Co3 made them good photosensitizers for aPDT. Co1-Co3 displayed significant antibacterial responses against gram-positive (S. aureus) and gram-negative (E. coli) bacteria upon light exposure (10 J cm-2 , 400-700 nm) and showed MIC values between 0.01-0.005 μg mL-1. The aPDT activities of these complexes were due to their ability to damage bacterial cell membranes via ROS generation. Overall, this study shows the photo-triggered ROS-mediated bacteria-killing potential of Co(III) complexes.

Aqueous photochemical aging of water-soluble smoke particles from crop straws burning

Most aqueous oxidation studies focus on single model precursors, while the photochemical aging of actual water soluble organic matter (WSOM) in particles emitted from biomass burning remains poorly understood. In this study, gas chromatography-mass spectrometry (GC/MS) was first used to analyze the WSOM in smoke particles emitted from three crop straws burning. The results show that the dominant WSOM in three crop straws (CS) smoke are phenolic substances with small differences. Aqueous photochemical aging of WSOM in CS smoke was investigated under simulated sunlight exposure. High-resolution aerosol mass spectrometry (HR-AMS) analyzed aqueous secondary organic aerosol (aqSOA) and it was found that the oxidation degree of aqSOA increased with prolonged aging. No obvious increase in the abundance of N-containing organic ions was observed over the course of aqueous aging. As aqueous aging progresses, the pH of the solution gradually decreases, accompanied by the continuous generation of organic acids. Studies on dithiothreitol (DTT) activity indicate that the impact of aqueous photochemical aging on health is not significant.The solution after photoaging shows relatively lower light absorption ability than the initial solution. The aqueous photochemical aging also led to a gradual reduction of fluorescence at excitation/emission = 250–260 nm/350 nm (protein-like substances) for CS smoke WSOM, suggesting the significant degradation of chromophores. However, three-dimensional excitation-emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC) revealed that aqueous aged CS smoke WSOM contains compounds with high humification index, confirming that the fluorophore composition is altered by aqueous aging. The humic-like substance (HULIS) concentration increased for the first 3 h and then decreased, closely matching the pattern of a new fluorescence peak. Finally, GC/MS analysis of the products indicated that there was obvious decline in proportion of methoxyphenol. The results of this study are important for understanding the aqueous-phase oxidation reactions of CS smoke WSOM in the atmosphere and their light-absorption characteristics and health impacts.

Mesoporous C-doped C3N5 as a superior photocatalyst for CO2 reduction

Use of naturally abundant solar light for CO2 reduction is a green pathway to reduce carbon footprint. C3N5 is a promising visible-light photocatalyst with enhanced local electron concentration and more active NN sites compared to g-C3N4. We herein report development of mesoporous C-doped C3N5 through a simple copolymerisation of 3-amino-1,2,4-triazole with trimesic acid via hard-templating method, which demonstrated enhanced light absorption ability and delocalised π-electron density (as evident from density functional theory calculation), resulting in efficient charge transfer to the active surface sites of the photocatalyst. The optimised C-doped mesoporous C3N5 exhibited a superior photocatalytic CO2 reduction activity with the CO evolution of 116.6 µmol·g−1, which is 4-fold and 12-fold times higher than that of C3N5 and g-C3N4 respectively. The enhanced photocatalytic CO2 conversion efficiency can be attributed to the synergetic effects of π-electron modulation by C-doping and enhanced surface-active sites brought by mesoporosity.

A 3D aerogel evaporator for efficient solar interfacial evaporation: Breaking through the upper limit of steam production rate

Solar desalination is the most effective way to obtain clean and cheap fresh water. However, its lower upper limit of steam production rate limits its development and practical applications. In this paper, a microcrystalline cellulose aerogel composite Mo2C evaporator (MCAM) was prepared by combining Mo2C with microcrystalline cellulose aerogel (MCA). The evaporator consists of MCAM photothermal layer, polyurethane (PU) sponge insulation layer and one-dimensional water channel. Mo2C has high-light absorption efficiency. At the same time, the vertical channel inside the MCA makes the incident light be reflected and absorbed for many times inside. Benefiting from the synergistic effect of the vertical channel of MCA and the light absorption ability of Mo2C, MCAM obtained a high light absorption efficiency of 96.96 %. The interaction between the MCAM evaporator and water can reduce the evaporation enthalpy, thereby breaking the upper limit of the steam generation rate. Therefore, the evaporator achieved a steam production rate of 1.92 kg⋅m−2⋅h−1 and an energy utilization efficiency of 118.2 %. In addition, MCAM shows excellent salt tolerance and self-discharging salt ability, which ensures its stable operation in high-salinity environment. Besides its high efficiency, MCAM has significant purification effect on simulated seawater, heavy metal wastewater, and organic wastewater. This study provides a new strategy for further improving the steam production rate of the solar interface evaporator.

ZnS and Reduced Graphene Oxide Nanocomposite-Based Non-Enzymatic Biosensor for the Photoelectrochemical Detection of Uric Acid.

In this work, we report a study of a zinc sulfide (ZnS) nanocrystal and reduced graphene oxide (RGO) nanocomposite-based non-enzymatic uric acid biosensor. ZnS nanocrystals with different morphologies were synthesized through a hydrothermal method, and both pure nanocrystals and related ZnS/RGO were characterized with SEM, XRD and an absorption spectrum and resistance test. It was found that compared to ZnS nanoparticles, the ZnS nanoflakes had stronger UV light absorption ability at the wavelength of 280 nm of UV light. The RGO significantly enhanced the electron transfer efficiency of the ZnS nanoflakes, which further led to a better photoelectrochemical property of the ZnS/RGO nanocomposites. The ZnS nanoflake/RGO nanocomposite-based biosensor showed an excellent uric acid detecting sensitivity of 534.5 μA·cm-2·mM-1 in the linear range of 0.01 to 2 mM and a detection limit of 0.048 μM. These results will help to improve non-enzymatic biosensor properties for the rapid and accurate clinical detection of uric acid.

Impacts of elevated anthropogenic emissions on physicochemical characteristics of black-carbon-containing particles over the Tibetan Plateau

Abstract. Black carbon (BC) in the Tibetan Plateau (TP) region has distinct climate effects that strongly depend on its mixing state. The aging processes of BC in the TP are subject to emissions from various regions, resulting in considerable variability of its mixing state and physicochemical properties. However, the mechanism and magnitude of this effect are not yet clear. In this study, field observations on physicochemical properties of BC-containing particles (PMBC) were conducted in the northeast (Xihai) and southeast (Lulang) regions of the TP to investigate the impacts of transported emissions from lower-altitude areas on BC characteristics in the TP. Large spatial discrepancies were found in the chemical composition of PMBC. Both sites showed higher concentrations of PMBC when they were affected by transported air masses outside the TP but with diverse chemical composition. Source apportionment for organic aerosol (OA) suggested that primary OA in the northeastern TP was attributed to hydrocarbon OA (HOA) from anthropogenic emissions, while it was dominated by biomass burning OA (BBOA) in the southeastern TP. Regarding secondary aerosol, a marked enhancement in nitrate fraction was observed on aged BC coating in Xihai when the air masses were brought by updrafts and easterly winds from lower-altitude areas. With the development of boundary layer, the enhanced turbulent mixing promoted the elevation of anthropogenic pollutants. In contrast to Xihai, the thickly coated BC in Lulang was mainly caused by elevation and transportation of biomass burning plumes from south Asia, showing a large contribution of secondary organic aerosol (SOA). The distinct transported emissions lead to substantial variations of both chemical composition and light absorption ability of BC across the TP. The thicker coating and higher mass absorption cross-section (MAC) of PMBC in air masses elevated from lower-altitude regions reveal the promoted BC aging processes and their impacts on the mixing state and light absorption of BC in the TP. These findings emphasize the vulnerability of plateau regions to influences of elevated emissions, leading to significant changes in BC concentration, mixing states and light absorption across the TP, all of which need to be considered in the evaluation of BC radiative effects for the TP region.

Synergistic photocatalytic activity of Bi2O3/g-C3N4/ZnO ternary heterojunction with dual Z-scheme charge transfer towards textile dye degradation

It is clear that a wide range of organic substances, including synthetic textile dyes, have the potential to negatively impact the environment. It is crucial to rationally develop highly effective photocatalysts for the degradation of such type of pollutants. In this regard, a heterostructured photocatalyst comes with enhanced charge separation and extended light absorption ability that improves photocatalytic performance. Therefore, In this study, a Bi2O3/g-C3N4/ZnO (BCNZ) ternary heterojunction photocatalyst was synthesized for the degradation of methylene blue (MB) textile dye.. Thermal polycondensation method was opted to synthesize g-C3N4, while ZnO and Bi2O3 photocatalysts were fabricated using co-precipitation method. Similarly, ternary heterojunction of BCNZ was constructed through co-precipitation method. The ternary heterojunction photocatalyst demonstrated better photodegradation ability due to dual Z-scheme charge transfer route. The dual Z-scheme heterojunction enabled the ternary heterojunction to exhibit enhanced light absorption capabilities with reduced recombination rates as well as enhanced charge separation and migration efficiency (confirmed via transient photocurrent response) that resulted in improved photocatalytic performance. The BCNZ dual Z-scheme photocatalyst displayed 92 % of degradation efficiency which was much higher than that of other (binary and pristine) photocatalysts. Scavenging tests and electron spin resonance spectroscopy revealed the significant role of the •O2−, and •OH radicals in the photodegradation of MB. Furthermore, the reusability test presented good stability and recyclability of the ternary photocatalyst with 80 % degradation efficiency after five catalytic cycles.