Ultraviolet-visible Diffuse Reflectance Spectra Research Articles

Cobalt Hydroxide Modification of TiO2 Nanosheets for Visible-Light-Responsive Photocatalysts.

To make full use of sunlight for water splitting reactions for hydrogen production, a visible-light-driven photocatalyst was developed by modifying TiO2 nanosheets with Co(OH)2. By adding an aqueous Co(NO3)2·6H2O solution to a TiO2 nanosheet suspension, the TiO2 nanosheets aggregated and Co(OH)2 was formed. In the ultraviolet-visible (UV-vis) diffuse reflectance spectrum of the photocatalyst, new absorption bands attributable to Co(OH)2 and the interfacial charge transfer between Co(OH)2 and the TiO2 nanosheets appeared at around 600 and 400 nm, respectively. The photocatalytic activity of Co(OH)2/TiO2 nanosheets was evaluated in terms of the O2 evolution reaction in an aqueous AgNO3 solution, finding that the reaction proceeds under visible light. Furthermore, the investigation of the wavelength dependence of the photocatalytic activity revealed that the photocatalytic reaction on Co(OH)2/TiO2 nanosheets proceeds via Co(OH)2 photocatalysis and interfacial charge transfer between Co(OH)2 and the TiO2 nanosheets under visible light irradiation.

Dynamically Cyclic Fe2+/Fe3+ Active Sites as Electron and Proton-Feeding Centers Boosting CO2 Photoreduction Powered by Benzyl Alcohol Oxidation.

Solar-driven CO2 photoreduction holds promise for sustainable fuel and chemical productions, but the complex proton-coupled multi-electron transfer processes and sluggish oxidation half-reaction kinetics substantially hinder its efficiency. Here, we devised a rational catalyst design to address these challenges by fabricating ferrocene carboxylic acid-functionalized Cs3Sb2Br9 nanocrystals (CSB-Fc NCs), which facilitate simultaneous benzyl alcohol oxidation and CO2 reduction reactions under visible-light irradiation. The synchronized proton-coupled electron transfer processes between the reduction and oxidation half-reactions on CSB-Fc NCs resulted in a 5-fold increase in the CO2 reduction rate (45.56 μmol g-1 h-1, 97.9% CO selectivity) and a 5.8-fold enhancement in benzyl alcohol conversion (97.7% selectivity for benzaldehyde) compared to the CSB. Insitu Raman and ultraviolet-visible diffuse reflectance spectra revealed that the dynamic Fe2+/Fe3+ redox loop within the Fc unit serves as the actual active site, facilitating the activation of substrate molecules. More importantly, insitu attenuated total reflection Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry spectroscopy, with isotope labeling of Deuteron-benzyl alcohol and 13CO2, confirmed that proton transfer from the hydroxyl group generates reactive protons at the Fe2+/Fe3+ site, enabling efficient CO2 photoreduction through subsequent protonation steps. This work offers a cost-effective and efficient approach for synergetic CO2 photoreduction driven by organic synthesis, advancing solar energy utilization.

Construction of loading g-C3N4/TiO2 on waste cotton-based activated carbon S-scheme heterojunction for enhanced photocatalytic degradation of microplastics: Performance, DFT calculation and mechanism study

In order to achieve the degradation of polyethylene microplastics (PE) in wastewater. The g-C3N4/TiO2/WCT-AC composite photocatalytic materials were prepared by mixed high-temperature thermal polymerization method with the g-C3N4 and the waste cotton based activated carbon (WCT-AC) loaded TiO2 as precursors. The phase morphology, elemental composition, morphology and photochemical properties of the g-C3N4/TiO2/WCT-AC were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), ultraviolet–visible diffuse reflectance spectrum (UV–vis DRS) and photo luminescence (PL). The results of UV–vis DRS and PL showed that the combination of the g-C3N4 and the TiO2/WCT-AC improved the absorption in the visible region, broadened the spectral response range, and the formation of heterojunctions enabled efficient photoelectron-hole separation and improved the photocatalytic activity. Under visible light irradiation for 200 h, catalyst dosage 50 mg, and system pH = 7.0, the highest removal rate of the g-C3N4/TiO2/WCT-AC for PE microplastics reached 67.58 %, and it still showed excellent stability after 5 cycles. The active groups such as ·O2−, ·OH and h+ produced in the g-C3N4/TiO2/WCT-AC system under visible light excitation realized the degradation of PE microplastics. The whole process is a complex oxidation bond breaking process, and the degradation of PE microplastics by g-C3N4/TiO2/WCT-AC follows the S-type charge transfer mechanism.

Enhanced Photocatalytic Hydrogen Evolution of In2S3 by Decorating In2O3 with Rich Oxygen Vacancies.

The hydrogen (H2) evolution rates of photocatalysts suffer from weak oxidation and reduction ability and low photogenerated charge carrier separation efficiency. Herein, by combining band-gap structure optimization and vacancy modulation through a one-step hydrothermal method, In2O3 containing oxygen vacancy (Ov/In2O3) is simply introduced into In2S3 to promote photocatalytic hydrogen evolution. Specifically, the change in the sulfur source ratio can induce the coexistence of Ov/In2O3 and In2S3 in a high-temperature hydrothermal process. Under light irradiation, In2S3@Ov/In2O3-0.1 nanosheets hold a remarkable average H2 evolution rate up to 4.04 mmol g-1 h-1, which is 32.14, 11.91, and 2.25-fold better than those of pristine In2S3, In2S3@Ov/In2O3-0.02, and In2S3@Ov/In2O3-0.25 nanosheets, respectively. The ultraviolet-visible (UV-vis) diffuse reflectance and photoluminescence (PL) spectra reveal that the formation of Ov/In2O3 in In2S3 optimizes the band-gap structure and accelerates the migration of the photogenerated charge carrier of In2S3@Ov/In2O3-x nanosheets, respectively. Both the enhancement of oxidation and reduction ability and photogenerated charge carrier separation ability are responsible for the remarkable improvement in photocatalytic H2 evolution performance. This work provides a new strategy to prepare a composite of metal sulfide and metal oxide through a one-step hydrothermal method.

Eu2+-Eu3+ Co-doping provoking polyhedron-cluster-based emission structural unit evolution triggering phases transition and blue-green-red multimode luminescence emission

A series of Ca2-xSiO4:xEu2+/Eu3+ and Ca2-2xSiO4:xEu2+/Eu3+, xM (M = Na+, K+) phosphors were prepared by co-doping Eu2+-Eu3+ in Ca2SiO4 solid solution for selectively locating Eu2+-Eu3+ ions deriving polyhedron-distorted emitting structure units’ evolution. During β, γ1,2-C2S matrix phase transitions, the structure and luminescence properties were analyzed by XRD, diffuse reflection, PL and luminescence thermal stability. The results show that Eu2+/Eu3+ occupying 6 Ca2+ sites forms 10 emission structural units in the matrix and the phase transition of γ1-Ca2-xSiO4(x = 0.0001–0.0004)→β-Ca2-xSiO4 (x = 0.0005–0.04)→β, γ2-Ca2-xSiO4 mixed phase (x = 0.08–0.32) is generated by the extrusion of structural units. Ultraviolet–visible diffuse reflectance spectra confirm the band gap difference caused by structural unit rotation. According to the bond energy method, the priority occupation order for the Eu2+/3+ ions was determined. The energy transfer of Eu2+→Eu3+ occurs when the structural units 3–10 of β, γ2-Ca2-xSiO4 mixtures coexist. After co-doped M+ as charge compensator, the luminescence intensity/thermal stability of Ca2-2xSiO4:xEu3+, xM(M = Na+, K+) were improved by 33.88 %/57.12 %, and 5.1 %/6.6 % than that of Ca2-xSiO4:xEu3+, respectively. These characteristics indicate that phosphors have broad application prospects in the field of solid-state lighting.

2D/1D nested hollow porous ZnIn2S4/g-C3N4 heterojunction based on morphology modulation for photocatalytic CO2 reduction

The two-dimensional (2D) composite one-dimensional (1D) heterojunction structure is one of the main strategies for constructing composite photocatalysts for photocatalytic reduction of carbon dioxide (CO2). However, morphology modulation for 2D/1D heterojunction is an important way to enhance performance. In this study, a unique 2D/1D ZnIn2S4/g-C3N4 nested hollow porous heterojunction structure was constructed by an in-situ growth method with spatial confinement effect. The synergy between 1D g-C3N4 and 2D ZnIn2S4, achieved through advanced morphology modulation at an optimal ratio of 3:1, results in the formation of the CZ-3 photocatalyst. This unique configuration enables a simultaneous high yield of carbon monoxide (CO) and methane (CH4), achieving 79.96 μmol/g and 17.33 μmol/g respectively, under visible light irradiation without the need for sacrificial agents. The core of this enhanced photocatalytic performance is attributed to the employment of a type-II heterojunction mechanism, which optimizes the transfer of photogenerated carriers. Ultraviolet-visible diffuse reflection spectrum, photoluminescence spectrum and photoelectrochemical analysis reveal the effect of morphology on photocatalytic performance in terms of visible light absorption, photogenerated carrier pairs separation and electronic band structure of heterojunction. By combining the advantages of 2D/1D structural benefits with the efficient charge dynamics of a type-II heterojunction, this work provides new ideas for improving the morphology of composite heterojunction photocatalysts with 2D/1D structure to enhance the photocatalytic CO2 reduction performance.

Negative comonomer effect induced by TiCl3-like clusters in MgCl2-based Ziegler-Natta catalysts

The comonomer effect of ethylene/α-olefin copolymerization in the Ziegler-Natta (Z-N) catalytic system, remaining largely elusive and less understood at the molecular level, has been of huge industrial importance and absorbing research interest for decades. Herein, four catalysts with similar physical structures but different polymerization activities and comonomer effects were synthesized by using n-butanol in combination with different secondary electron donors. By tracking catalyst formation, it was found that altering the secondary donor changes the ν(O-H) stability and in turn the MgCl2 facet growth, to influence the polymerization activity. In situ diffuse reflectance Ultraviolet–visible spectra show that different types of active Ti centers are in function in the ethylene polymerization and the ethylene/1-butene copolymerization. Tracing further the microscopic structures of active species upon triethylaluminium (TEA) activation by using Extended X-ray Absorption Fine Structure, it is found that: (i) for the catalysts with negative comonomer effect, the enhanced donor migration promotes the aggregation of active species and leads to the formation of TiCl3-like clusters; (ii) by contrast, for the catalysts with positive comonomer effect, the less mobile donors hinder the aggregation of active species, thus inducing the formation of isolated Ti3+ sites. Our work reveals an evident correlation between the active center and the comonomer effect, which may be strongly modified by the aggregation of the former.

Robust Thiazole-Linked Covalent Organic Frameworks for Water Sensing with High Selectivity and Sensitivity.

The rational design of covalent organic frameworks (COFs) with hydrochromic properties is of significant value because of the facile and rapid detection of water in diverse fields. In this report, we present a thiazole-linked COF (TZ-COF-6) sensor with a large surface area, ultrahigh stability, and excellent crystallinity. The sensor was synthesized through a simple three-component reaction involving amine, aldehyde, and sulfur. The thiazole and methoxy groups confer strong basicity to TZ-COF-6 at the nitrogen sites, making them easily protonated reversibly by water. Therefore, TZ-COF-6 displayed color change visible to the naked eye from yellow to red when protonated, along with a red shift in absorption in the ultraviolet-visible diffuse reflectance spectra (UV-vis DRS) when exposed to water. Importantly, the water-sensing process was not affected by polar organic solvents, demonstrating greater selectivity and sensitivity compared to other COF sensors. Therefore, TZ-COF-6 was used to detect trace amounts of water in organic solvents. In strong polar solvents, such as N,N-dimethyl formamide (DMF) and ethanol (EtOH), the limit of detection (LOD) for water was as low as 0.06% and 0.53%, respectively. Even after 8 months of storage and 15 cycles, TZ-COF-6 retained its original crystallinity and detection efficiency, displaying high stability and excellent cycle performance.

Selective catalytic reduction of NOX with CH4 over In/SSZ-13 zeolites: The enhancement of high-temperature catalytic activity by Ce modification

The selective catalytic reduction of nitrogen oxides by methane (CH4/NOX-SCR) is a potential technique for the abatement of the NOX emissions from lean-burn GDI engines, due to the excellent thermal stability of CH4. This work focuses on the promotion of In/SSZ-13 catalysts by Ce modification for the CH4/NOX-SCR performance at high temperatures. A series of In/SSZ-13 and Ce-In/SSZ-13 catalysts were prepared using the wetness impregnation method. The effects of Ce modification on the catalytic performance were analysed in detail using the scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectrum and temperature-programmed desorption/reduction techniques. The results show that the Ce modification significantly enhances the high-temperature activity of the In/SSZ-13 catalysts for the NOX-SCR reaction, especially for the 5 wt% Ce-15 wt% In/SSZ-13 sample which has more than 75% NOX conversion at 390–700 °C. In addition, the Ce modification enhances the water vapor tolerance of the catalyst sample. The Ce modification increases not only the concentration of surface chemisorption oxygen species, but also the relative amount of InO+ species which serve as the main active sites for CH4 activation. Furthermore, the incorporation of Ce into In/SSZ-13 greatly promotes NOX adsorption on the catalyst surface. Most importantly, the Ce modification makes In species well-dispersed on the catalyst surface and thus suppresses the formation of bulk In2O3 species which are more active for the CH4 non-selective oxidation. The combination of all these effects results in the Ce-In/SSZ-13 samples with the superior catalytic activity.

Deciphering the synergistic action of multiple factors inducing high piezoresponse in CaBi4Ti4O15‐based piezoelectric ceramics

AbstractNaBiCe/Sc ions were co‐doped into a pure CaBi4Ti4O15 (CBT) ceramic to investigate the synergistic action of multiple factors that induced a high piezoresponse. In comparison to the undoped CBT ceramic, the NaBiCe/Sc co‐doped CBT solid solution exhibited an enhancement in spontaneous polarization (Ps) attributed to the tilting of the oxygen octahedra, enhanced domain reorientation owing to increased grain size, and improved dielectric breakdown strength as a consequence of reduced porosity. The synergistic action of the aforementioned comprehensive factors resulted in excellent electrical properties of Ca0.6(Na0.5Bi0.5)0.4Bi3.97Ce0.03Ti3.925Sc0.075O15 ceramic: piezoelectric coefficient d33 = 25.0 pC/N, remnant polarization Pr = 9.28 μC/cm2, and coercive field Ec = 76.14 kV/cm. Moreover, a significant high direct current resistivity (ρdc = 1.22 × 107 Ω·cm at 500°C) was achieved, and the corresponding conductance mechanism was analyzed through a synergistic approach that combines ultraviolet–visible diffuse reflectance spectra and density functional theory.

Structural properties and photocatalytic activity of amorphous-crystalline TiO2 thin films

TiO2-coated glass plates were prepared by dip coating using TiO2 coating sol with a mixed amorphous and crystalline structure. These samples were dried at 100°C or calcined at 500°C, which were referred to as MT and CT, respectively. The TiO2 thin films on glass plates were characterized by X-ray diffraction, thermogravimetry-differential thermal analysis, X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy, Brunauer-Emmett-Teller surface area measurement, scanning electron microscopy, and ultraviolet–visible diffuse reflectance spectra. The TiO2 thin films of MT samples had mixed amorphous and crystalline structures, while those of CT samples had only crystalline structures. The photocatalytic activity of the samples was investigated on the basis of methylene blue (MB) decomposition under ultraviolet and visible light irradiation. In the dark stabilization, MT samples had a higher MB adsorption capacity than CT samples. MT samples had a smaller amount of anatase TiO2 than CT samples, but both glass plate samples showed the same MB photocatalytic activity under ultraviolet light irradiation. We presumed that these results were because the amorphous-crystalline TiO2 thin films had a high specific surface area, so they had more adsorption and active sites. Under visible light irradiation, only the MT samples had photocatalytic activity, which can be attributed to their high visible light absorbance, which may be due to their peroxo groups, disordered structure, and larger specific surface area.

Crystal structure, Hirshfeld surface analysis, optical properties and stability of organic-inorganic compound (C6H5CH2NH3)2(CH3CH3NH2)3Bi2Br11

A novel bismuth-based zero-dimensional organic-inorganic hybrid material (C6H5CH2NH3)2(CH3CH3NH2)3Bi2Br11 was synthesized by a hydrothermal method. The crystal structure, intermolecular interactions, chemical groups, chemical bond characterization, optical and thermal stability of the sample were systematically investigated by single crystal X-ray diffraction, powder X-ray diffraction, Hirshfeld surface analysis, field scanning electron microscopy, Fourier transform infrared spectrometer, Raman spectra, thermogravimetric analysis, and Ultraviolet–visible diffuse reflectance spectra. The results indicated that the (C6H5CH2NH3)2(CH3CH3NH2)3Bi2Br11 crystal displayed a triclinic crystal system with a P-1 space group at room temperature with a = 8.5290(4) Å, b = 14.2484(10) Å, c = 18.9386(10) Å, α = 94.418(5) °, β = 102.260(4) °, γ = 106.595(5) °, V = 2131.9(2) Å3, Z = 2, R1 = 0.0936, wR2 = 0.1536. The compound displayed typical zero-dimensional consisting of two benzylamine organic [C6H5CH2NH3]+ cations, three dimethylamine organic [CH3CH3NH2]+ cations and a corner-sharing dimer unit [Bi2Br11]5–. Infrared and Raman vibrational study indicates the presence of [CH3CH3NH2]+. The 2D fingerprint plot of Hirshfeld surface analysis shows that H⋯Br/Br⋯H (56.8 %) and H⋯H (31.4 %) are major contributions to the intermolecular contact of (C6H5CH2NH3)2(CH3CH3NH2)3Bi2Br11. The sample presented relatively perfect thermal stability up to 240 °C and a wide band gap of about 2.75 eV. It provides some reference value for exploring organic-inorganic hybrid materials with low toxicity and high thermal stability.

CeO2-CePO4 and Ag@CeO2-CePO4 nanocomposites from Penaeus semisulcatus for heavy metals sensing, UV shielding and cytotoxic applications

CeO2-CePO4 and Ag@CeO2-CePO4 nanocomposites (NCs) were prepared using Penaeus semisulcatus and characterized by various analytical techniques. The NCs exhibited spherical morphology, with average particle sizes measuring 2.36 nm, 3.30 nm and 29.64 nm for the samples air dried, annealed at 550 °C and 800 °C respectively, and the Selected Area Electron Diffraction patterns from HR-TEM revealed their crystalline nature. In 3d X-ray Photoelectron Spectra (XPS) of NCs, the highest binding energies were observed at 916.46 eV (3d3/2) and 898.16 eV (3d5/2) with spin–orbit splitting of 18.3 eV. The X-Ray Diffraction (XRD) patterns of the NCs showed peaks typical of both CeO2 and CePO4 phases. The Fourier Transform-Infra Red (FT-IR) spectrum contained bands due to Ce-O stretching at 560 cm−1 and PO43- groups at 1008 and 711 cm−1, which was further substantiated by Raman spectrum, which had an intense peak at 468 cm−1 corresponding to F2g band of CeO2 and another peak at 976 cm−1 due to PO43- tetrahedron. In the Ultraviolet-Visible Diffuse Reflectance Spectra (UV-Vis DRS), the broad absorption peak at 352 nm and minor peaks around 300 nm confirmed the formation of CeO2-CePO4 NCs. The green synthesized NCs were excellent fluorescence sensors for Pb2+, Cd2+ and Hg2+ in a wide range of concentrations, from 5.0x10-9 M to 4.0x10-5 M. The concentration Vs. emission fitting plot had three distinctive linear ranges. At a low concentration range (5x10-9 to 3.5x10-7 M), the limit of detection for Pb2+, Cd2+ and Hg2+ was found to be 2.41x10-8, 2.56x10-8 and 3.11x10-8 M. The sensitive detection of a mixture of heavy metal ions in ppb levels by biocompatible NCs gained insight in treating aqueous industrial wastes. Further, NCs showed cytotoxicity and UV shielding properties.

Enhanced photocatalytic degradation of crystal violet dye and high-performance electrochemical supercapacitor applications of hydrothermally synthesised magnetic bifunctional nanocomposite (Fe3O4/ZnO)

The present investigation employed a facile hydrothermal approach for the fabrication of Fe3O4/ZnO dual-functional magnetic nanocomposite. Supercapacitor and visible-light-driven photocatalytic applications of the material were explored. X-ray diffraction, Fourier transform infrared spectra, ultraviolet–visible diffuse reflectance spectra (UV–vis/DRS), field emission scanning electron microscopy (FE-SEM), energy dispersive x-ray spectroscopy, and vibrating sample magnetometer were used to analyse the nanocomposite’s structural, morphological, optical, and magnetic properties. The FE-SEM analysis demonstrated that the surface morphology of Fe3O4, ZnO, and the Fe3O4/ZnO nanocomposite consisted of nanoparticles, nanoflakes, and nanoparticles adhered to the nanoflakes, respectively. The maximum specific capacitance of the electrode based on the Fe3O4/ZnO nanocomposite was measured to be 736.36 Fg−1 at a scan rate of 5 mVs−1. The electrode also demonstrated remarkable cycling stability, retaining 86.5% of its capacitance even after 3000 cycles. The Fe3O4/ZnO nanocomposite was found to have an optical bandgap of 2.7 eV, an average particle size of 22.5 nm, and a saturation magnetization of 68.7 emu g−1. The photocatalysis experiment was conducted using the optimised settings, which included a pH of 7.0, a dye concentration of 30 mg l−1, a catalyst dose of 1 g l−1, and a contact time of 120 min. The Fe3O4/ZnO nanocomposite exhibited a notable degradation efficiency towards crystal violet dye upon exposure to visible light, achieving a degradation efficiency of 96.9%. This performance surpassed that of pure ZnO, which attained a degradation efficiency of 70.2%. The nanocomposite exhibited a rate constant of 2.80 × 10−2 min−1, which was found to be notably higher than that of pure ZnO (0.8 × 10−2 min−1), as determined through modelling (pseudo-first order linear fit). The radical scavenger experiments indicated that the superoxide radicals and hydroxyl radicals are the primary reactive species. The Fe3O4/ZnO photocatalyst can be effectively isolated using a bar magnet. Remarkably, the photocatalytic efficiency of the material remained almost entirely intact even after undergoing four cycles of recycling. In addition, this research opens up exciting new possibilities for use in fields like energy storage and pollution control.

In-situ preparation of double Z-scheme Ag6Si2O7/C3N4/NH2-MIL-125(Ti) composite for visible-light photocatalytic degradation of organic pollutants in water

To develop photocatalysts with strong reactivity under visible light irradiation, economic feasibility, and superior effectiveness, based on the optimization of the binary NH2-MIL-125(Ti)/C3N4 composite proportion, Ag6Si2O7 can be deposited in situ on the surface of NH2-MIL-125(Ti)/C3N4 composite, the ternary photocatalytic composite material Ag6Si2O7/C3N4/NH2-MIL-125(Ti) has been fabricated with success. The ternary material was characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS), transmission electron microscope (TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transforms infrared spectroscopy (FT-IR), ultraviolet–visible diffuse reflectance spectrum (UV-Vis DRS), photoluminescence (PL), electrochemical impedance spectroscopy (EIS) as well as X-ray photoelectron spectroscopy (XPS) analysis. The effects of the mass proportions of NH2-MIL-125(Ti) to C3N4 as well as Ag6Si2O7 to NH2-MIL-125(Ti)/C3N4 on the visible light catalytic performance were investigated. It was found that the binary composite material with a mass proportion of 1:5 of NH2-MIL-125(Ti) to C3N4 and the tertiary material with a mass proportion of 1:20 of Ag6Si2O7 to NH2-MIL-125(Ti)/C3N4 exhibited superior photocatalytic performance towards Rhodamine B (RhB) and various colorless organic contaminants, the apparent photocatalytic rate constants of the tertiary composite material for RhB, tetracycline, and ethenzamide were 15.6, 1.69 and 1.75 times that of the Ag6Si2O7 alone, and 1.30, 1.42 and 7.98 times that of the NH2-MIL-125(Ti)/C3N4 binary composite, individually. The composite maintains high efficiency after completing three cycles. The formation of active species and the effective degradation of organic contaminants during photocatalysis can be attributed to the compact double Z-scheme heterostructure among the three semiconductors in the ternary composite. The development of the double Z-scheme composite is of great significance for the economical and highly efficient elimination of organic contaminants.

Construction of P-C3N4/C3N5 isotypic heterojunction for effective degradation of organic pollutants

BackgroundPhotocatalysis was an effective method for organic pollutant degradation, and graphitic carbon nitride g-C3N4 and g-C3N5 were famous two-dimensional semiconductors. Compared to the allotypic heterojunction, the band alignment and compatibility of isotypic heterojunction were superior. MethodsIn this work, an organic isotypic heterojunction was constructed via coupling phosphorus-doped C3N4 (P-C3N4) and g-C3N5. The characteristics were evaluated using transmission electron microscope, Fourier transform infrared, X-ray diffractometer, X-ray photoelectron spectrum, ultraviolet-visible (UV–vis) diffuse reflection spectrum, electronic spin resonance (ESR) analysis, photoluminescence spectrometer, electrochemical impedance spectroscopy, and photocurrent analysis. SignificantIsotypic heterojunction displayed high UV–vis light harvest, high separation efficiency of photo-induced charge carriers, and low surface resistance. Additionally, an internal-electric-field was established at the interface, which was beneficial for spatial separation of photo-induced charge carriers. As expected, the Rhodamine B (RhB) degradation efficiency was 7.3 and 12.3 times higher than that of the P-C3N4 and g-C3N5. Radical trapping experiment and ESR analysis indicated that •O2−, •OH, hole, 1O2, and electron played joint role in RhB degradation. In this work, a photocatalyst with excellent photocatalytic degradation properties was designed, and it provided a simple and novel strategy for environmental remediation.

Foamed glass functionalized with iron compounds: A strategic material for heterogeneous photocatalysis

Foamed glasses were synthesized using waste and low-cost materials. Two foaming agents were used: graphite and limestone. In addition, the foamed glass were functionalized with hematite for heterogeneous photocatalytic application. The X-ray diffractograms (XRD) showed that hematite was reduced into magnetite and that graphite remained after the thermal treatment. According to the ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS), the generated magnetite presented the same optical properties as those of the hematite raw, with the benefits of being incorporated into a low density material, which can increase the incidence of electromagnetic irradiation and hasten the photocatalytic process. This photocatalyst was able to degrade 98.6% of the Sunset Yellow dye within 15 min, without generating harmful by-products, measured by acute toxicity tests employing microcrustacean Artemia sp.

Elucidating the structure-nonlinear optical property relationship of Te2O4(OH)2

A mixed-valent tellurium oxide hydroxide, Te2O4(OH)2, containing both tetravalent (IV) and hexavalent (VI) tellurium cations has been synthesized using a hydrothermal reaction method. Single crystal X-ray diffraction reveals that the compound crystallizes in the polar noncentrosymmetric space group, Pna21 (no. 33). The reported compound has a layered structure consisting of Te(VI)O4(OH)2 octahedra and Te(IV)O4 seesaw, in which each layer is aligned through interlayer hydrogen bonds. In addition to the structural refinements, the structure and optical properties of the material have been studied and compared with Te2O5, which is dehydrated residue of the title compound. Second harmonic generation (SHG) measurements indicate that the Te2O4(OH)2 exhibits a large SHG efficiency of ca. 4.7 times that of KH2PO4. The ultraviolet–visible diffuse reflectance spectrum shows that the material has a band gap of ca. 3.5 eV, corresponding to a UV cutoff edge of 354 nm. These values suggest that the compound has expanded its band gap while maintaining its SHG response, compared to Te2O5. Theoretical calculations using the density functional theory have been also performed to clarify the structure-property relationship of the reported material more effectively.

Effect of Ag Modification on the Structure and Photocatalytic Performance of TiO2/Muscovite Composites

Ag/TiO2/muscovite (ATM) composites were prepared by the sol-gel method and the effects of Ag modification on the structure and photocatalytic performance were investigated. The photocatalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller surface area (BET), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), photoluminescence spectra (PL) and ultraviolet-visible diffuse reflectance spectra (DRS). The photocatalytic activity of the obtained composites was evaluated by taking 100 mL (10 mg/L) of Rhodamine B (RhB) aqueous solution as the target pollutant. The muscovite (Mus) loading releases the agglomeration of TiO2 particles and the specific surface area increases from 17.6 m2/g (pure TiO2) to 39.5 m2/g (TiO2/Mus). The first-order reaction rate constant increases from 0.0009 min-1 (pure TiO2) to 0.0074 min-1 (150%TiO2/Mus). Ag element exists in elemental silver. The specific surface area of 1-ATM further increases to 66.5 m2/g. Ag modification promotes the separation of photogenerated electrons and holes and increases the visible light absorption. 1%Ag-TiO2/Mus (1-ATM) exhibits the highest photocatalytic activity. After 100 min, the rhodamine B (RhB) degradation degrees of PT, 150%TiO2/Mus and 1-ATM are 10.4%, 48.6% and 90.6%, respectively. The first-order reaction rate constant of 1-ATM reaches 0.0225 min-1, which is 25 times higher than that of pure TiO2.

Surfactant-induced photocatalytic performance enhancement of europium oxide nanoparticles

Recently, rare earth (RE) elements and their oxides have been attracting more and more attention in the field of photocatalytic degradation. Due to the unique 4 f electronic structure and optical properties, the RE element, europium (Eu), together with its oxides, are often used for surface modification of other photocatalysts. Nevertheless, the photocatalytic degradation property of europium oxide has been rarely reported. In this study, we synthesized Eu2O3 nanoparticles via chemical precipitation and calcination processes, and performed surface modification by using surfactants as polyvinyl pyrrolidone (PVP) and hexadecyl trimethyl ammonium bromide (CTAB). Compared with pure Eu2O3 nanoparticles and those synthesized with PVP, photocatalytic degradation efficiencies of Eu2O3 nanoparticles synthesized with surfactant CTAB for degrading rhodamine B dye demonstrated to be improved by 16% and 12%, respectively. The ultraviolet-visible diffuse reflectance spectra measurements indicate that CTAB can increase the bandgap of Eu2O3 due to the reduction of oxygen defects. Photoluminescence spectra demonstrate that the surfactant would affect the luminescence of Eu3+ and carrier redistribution of energy levels.