UV Vis Diffuse Reflectance Spectroscopy Research Articles

Plasmonic resonance and type-I heterojunction interface in SrTiO3/CZTS/Ag nanocomposite for enhanced photocatalytic degradation of organic pollutants

As a novel plasmonic-heterostructure photocatalyst, the Silver (Ag)-modified SrTiO3/Cu2ZnSnS4 ternary nanocomposite was prepared through a co-precipitation method. The incorporation of Cu2ZnSnS4 (CZTS) and Ag into the SrTiO3 host phase reduced the mean particle size from 65 to 38 nm, doubled the surface area, and decreased the bandgap energy from 3.20 to 2.86 eV. A study of UV–visible diffuse reflectance spectroscopy (DRS) and valence band X-ray photoelectron spectroscopy (VB-XPS) confirmed the formation of type-I heterostructure charge transfer mechanisms between SrTiO3 and CZTS phases. Results from photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and transient photocurrent experiments indicated that the ternary nanocomposite exhibits less internal resistance and a higher capacity for charge carrier separation. The effect of different photocatalytic experiment parameters on the photodegradation performance has been studied. In this regard, 90 min visible light irradiation time, 5 mg/L initial dye concentration, and 1 g/L powder dosage were found to be the best values. The designed system exhibited excellent photocatalytic performance, in which more than 99% of methylene blue (MB) dye degraded under optimum conditions. The reaction mechanism and kinetics were comparatively investigated in-depth. After a four-run cyclic experiment, the prepared photocatalyst exhibited high stability and reusability. The prepared sample demonstrated photocatalytic efficiencies of 87%, 66%, and 71% for the degradation of methyl orange (MO), Rhodamine-B (RhB), and Ciprofloxacin (CIP) pollutants, respectively.

Optical, structural properties and photocatalytic potential of Nd-ZnO nanoparticles synthesized by hydrothermal method

The structural, optical, and photocatalytic properties of hydrothermally produced ZnO and Nd-ZnO nanostructures were studied. Doped and un-doped nanomaterials properties examine by (XRD) X-ray diffraction, (FESEM) Field Emission Scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and (DRS) UV–vis diffuse reflectance spectroscopy. XRD results show that ZnO crystalline size increases from 21.13 nm to 29.59 nm with Nd doping. DRS study indicates that energy band gap of doped ZnO sample was 3.19 eV while in case of ZnO sample 3.26 eV. The hexagonal rod shape morphology of doped ZnO was established by FESEM analyses. The photocatalytic activities of the produced nanomaterials were determined by Congo red dye photodegradation under UV and Solar light. In UV and Solar light, the photocatalytic activity of Nd-doped incorporated ZnO for CR degradation was 98.5 % and 91 %, respectively.

Heterojunction of (P, S) co-doped g-C3N4 and 2D TiO2 for improved carbamazepine and acetaminophen photocatalytic degradation

Novel photocatalysts of phosphorus and sulfur co-doped graphitic carbon nitride incorporated in 2D TiO2 structure were successfully fabricated and applied for solar-driven degradation of emerging pollutants from the group of pharmaceuticals not susceptible to biodegradation. The hybrid photocatalysts with different loadings of (P, S)-doped g-C3N4 were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy (DR/UV–vis), photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM). The optimum (P, S)-doped g-C3N4/TiO2 (5 %) composite revealed improved photocatalytic activity towards the degradation of carbamazepine and acetaminophen. For CBZ, about 100 % degradation was achieved in less than 30 min of photodegradation, whereas for ACT, the complete removal was observed in 60 min of irradiation under simulated solar light. The multi-anion doped g-C3N4/2D TiO2 composite demonstrated an excellent synergy towards the degradation of CBZ and ACT with a synergy index of 1.35 and 1.62. Moreover, the mineralization efficiency measured as TOC removal was 76 % and 40 % for CBZ and ACT, respectively. The reactive oxygen species responsible for the degradation of selected pharmaceuticals are superoxide (O2–) and hydroxyl radicals (HO), and the kinetics of reactions proved to fit the first-order kinetics with a rate constant of 0.21 min−1 for CBZ degradation and 0.074 min−1 for ACT degradation. Our results suggest that (P, S)-doped g-C3N4/ 2D TiO2 heterostructure is a Z-scheme heterojunction, which can effectively separate photogenerated charge carriers. The emissions and decay times analyzed for single components and the optimal (P, S)-doped g-C3N4/ 2D TiO2 (5 %) composite confirmed interfacial charge transfer between TiO2 nanosheets and (P, S)-g-C3N4 and more effective separation of electron-hole pairs. Identification of carbamazepine and acetaminophen intermediates was performed using LC-MS analysis in combination with additional DFT calculations of the possible by-products formation. Regarding reusability, the photocatalytic activity of (P, S)-doped g-C3N4/ 2D TiO2 (5 %) was stable after subsequent cycles of carbamazepine and acetaminophen degradation.

A bimetallic nanocatalyst from carbonaceous waste for crystal violet degradation

The contamination of wastewater by cationic dyes has caused considerable environmental problems, such as an imbalance in the aquatic ecosystem and a decrease in photosynthetic activity. In this context, this study aims to synthesize and characterize a bimetallic nanocatalyst (MMT@TiO2-NPs/ZnO-NPs), as well as to evaluate its photocatalytic activity in crystal violet (CV) dye degradation. The samples were characterized by X-ray diffraction (XRD), Field Emission Gun – Scanning Electron Microscope (FEG-SEM), N2 physisorption (BET/BJH methods), UV–Vis Diffuse Reflectance Spectroscopy (DRS), zeta potential (ZP), and zero charge point (pHZCP). Central composite rotational design (CCRD 2³) was used for the experimental design to obtain the ideal condition. The diffractograms showed characteristic peaks of MMT (analcime and neighborite), ZnO-NPs (zincite) and TiO2-NPs (anatase) with an average crystallite size determined in the range of 10–50 nm. The MMT@TiO2-NPs/ZnO-NPs showed a high surface area (98.8 ± 0.6 m2 g−1) with IV-type isotherm characteristic of porous materials. Moreover, a heterogeneous morphology with an average particle size of around 16 nm. ZP showed a negative charge (−3.84 ± 0.07 mV) and pHZCP ≈ 5.80, favoring interactions with the CV dye. Ideal condition was [CV] = 32.5 g L−1, [MMT@TiO2-NPs/ZnO-NPs] = 1.75 g L−1 and pH = 12, with a CV removal of 99.97% (k = 0.0789 min−1) under visible radiation. Regarding reuse, MMT@TiO2-NPs/ZnO-NPs showed great photocatalytic stability after six cycles with 90.62% for the CV degradation. Therefore, MMT@TiO2-NPs/ZnO-NPs showed great potential for use in the treatment of industrial textile effluents, helping in the waste management strategy from mid-to long-term perspectives.

Comparative Study on Photocatalytic Performance of TiO2 Doped with Different Amino Acids in Degradation of Antibiotics

In this study, three different reusable photocatalysts containing different amino acids as a source of non-metals, including L-Arginine, L-Proline, and L-Methionine, have been synthesized for the first time. Using a kinetic study and degradation efficiency test, these visible driven photocatalysts were investigated for their photocatalytic activity in removing antibiotics, including metronidazole (MNZ) and cephalexin (CEX). The morphology, structure and optical properties of the fabricated catalysts were characterized by X-ray Powder Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectrometry (EDS)/mapping, Fourier-Transform Infrared Spectroscopy (FTIR), Photoluminescence Spectroscopy (PL) and UV-Vis Diffuse Reflectance Spectroscopy (DRS) analyses. Based on the results of the PL analysis, it was confirmed that doping TiO2 with amino acids containing C, N, and S inhibited the recombination of induced electrons and holes. Among the three catalysts, L-Arginine-TiO2 demonstrated the highest photocatalytic activity for antibiotic degradation, followed by L-Proline-TiO2. According to the response surface methodology (RSM), the optimum operating conditions were a concentration of 50 mg/L MNZ, pH = 4, and catalyst concentration = 1.5 g/L under 90 min of irradiation time. At this condition, 99.9% of MNZ and 81% of TOC were removed. In addition, 97.2% of CEX and 75% TOC were eliminated at the optimum conditions of 1g/L catalyst concentration, 50 mg/L CEX concentration, at neutral pH, and after 120 min irradiation. L-Arginine (1 wt.%)-TiO2 was tested for stability and reusability, and it showed that after five cycles, 10% of its performance had been lost. The role of reactive species in photocatalysis was identified and •OH had the most significant impacts on MNZ and CEX photodegradation. Antibiotic degradation efficiency was adversely affected by the presence of anions and humic acid, but this reduction was not significant for inorganic anions, as only 13% of degradation was lost.

Synergistic C-TiO2/ZIF-8 type II heterojunction photocatalyst for enhanced photocatalytic degradation of methylene blue.

Zinc imidazolate framework (ZIF-8) and titanium dioxide (TiO2) have been extensively studied as photocatalysts and have shown remarkable potential. In this study, we report the synthesis of a type II heterojunction photocatalyst based on carbon-doped TiO2 (C-TiO2) and ZIF-8 as a potentially improved material for solar light-harvested methylene blue (MB) degradation. Pure ZIF-8 has a wide band gap of 4.9eV, due to which the application of this material to visible light-assisted photocatalytic performance is a challenging task. Therefore, C-TiO2 has been chosen as a composite material with ZIF-8 owing to its narrow band gap compared to TiO2. This enables the free radical-initiated photocatalytic reaction to shift into the visible region instead of the ultraviolet region. To construct the C-TiO2/ZIF-8 heterostructure, the zinc-based ZIF matrix has been built upon the exterior of C-TiO2 nanoparticles. UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRS) corroborated the decrease in the band gap of ZIF-8 after the fabrication of C-TiO2/ZIF-8, while X-ray diffraction (XRD) analysis demonstrated a decrease in average d-spacing and average crystallite size of the synthesized photocatalyst. Raman spectra and X-ray photoelectron spectroscopy (XPS) analysis of the synthesized samples were also performed to further understand their chemical structure and elemental content. Ultraviolet photoelectron spectroscopy (UPS) and high-resolution transmission electron microscopy (HRTEM) analyses were performed to understand the valence band (VB) states and the morphology of C-TiO2/ZIF-8. The comparison between pure ZIF-8 and C-TiO2/ZIF-8 in the photocatalytic degradation of MB under visible light has also been drawn. A possible charge-transfer mechanism for the same has also been proposed. It is concluded that the synergistic effect of C-TiO2 and ZIF-8 in C-TiO2/ZIF-8 produces an effective material for photocatalytic dye degradation.

Photocatalytic Synthesis of Materials for Regenerative Medicine Using Complex Oxides with β-pyrochlore Structure.

Graft copolymerization of methyl methacrylate onto cod collagen was carried out under visible light irradiation (λ = 400-700 nm) at 20-25 °C using the RbTe1.5W0.5O6, CsTeMoO6, and RbNbTeO6 complex oxides with β-pyrochlore structure as photocatalysts. The as-prepared materials were characterized by X-ray diffraction, scanning electron microscopy, and UV-Vis diffuse reflectance spectroscopy. It was also found that RbNbTeO6 with β-pyrochlore structure was not able to photocatalyze the reaction. Enzymatic hydrolysis of the obtained graft copolymers proceeds with the formation of peptides with a molecular weight (MW) of about 20 and 10 kDa. In contrast to collagen, which decomposes predominantly to peptides with MW of about 10 kDa, the ratio of fractions with MW of about 10 kDa and 20 kDa differs much less, their changes are symbatic, and the content of polymers with MW of more than 20 kDa is about 70% after 1 h in the case of graft copolymers. The data obtained indicate that synthetic fragments grafted to the collagen macromolecule do not prevent the hydrolysis of the peptide bonds but change the rate of polymer degradation. This is important for creating network matrix scaffolds based on graft copolymers by cross-linking peptides, which are products of enzymatic hydrolysis.

Fabrication, characterization, and gas sensing performance of chromium doped WO3 nanoflakes

Pristine and chromium (Cr) doped WO3 nanoflakes (NFs) with various concentrations were successfully fabricated by a facile hydrothermal technique on alumina (Al2O3) substrates. The structural, optical, and morphological properties of these NFs were investigated by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-Visible diffusion reflectance spectroscopy (UV–Vis DRS), and x-ray photoelectron spectroscopy. Gas sensor tests were performed against various volatile organic compounds such as ethanol, xylene, toluene, and isopropanol gases in the temperature range between 50 °C and 250 °C. According to the results of these tests, the isopropanol sensing ability of WO3 NFs is enhanced with Cr-doping due to the increasing active adsorption sites on the surface and improved surface reactions with the decreasing band gap energy. The highest isopropanol sensing response which was calculated to be 77.1 has been obtained by nominally 2% Cr doping at the optimal operating temperature of 150 °C.

Optical response of SrTiO3 thin films grown via a sol-gel-hydrothermal method

The polycrystalline SrTiO3 thin films were prepared by the sol-gel-hydrothermal method on glass substrates. The synthesis pathway was initiated by preparing a clear TiO2 solution using the sol-gel method. This clear solution was then deposited on a glass substrate using the dip coating technique, followed by the transformation of a thin layer of TiO2 into SrTiO3 by the hydrothermal method. The crystal structure, bond interactions, and band gap energy of SrTiO3 thin layers were characterized using X-ray Diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), and UV–Vis Diffuse Reflectance Spectroscopy (UV-DRS). The XRD patterns of all SrTiO3 thin layers indicated the perovskite structure of the samples. The FTIR spectrum showed an interaction of the silanol groups on the surface of the glass substrate with Ti–O–Ti of SrTiO3 layers. The characteristics of the UV-DRS spectrum were influenced by the thickness of the SrTiO3 layer formed on the glass substrate. The findings of this work provide insights for producing SrTiO3 layers with specified thickness and morphology.

Reusable Fe2O3/TiO2/PVC Photocatalysts for the Removal of Methylene Blue in the Presence of Simulated Solar Radiation.

Currently, environmental pollution by various organic pollutants (e.g., organic dyes) is a serious, emerging global issue. The aqueous environment is highly exposed to the harmful effects of these organic compounds. Furthermore, the commonly applied conventional purification techniques are not sufficient enough. Heterogeneous photocatalysis and the photo-Fenton process are effective, low-cost and green alternatives for the removal of organic pollutants. In this study, different iron(III) oxide/titanium(IV) oxide/polyvinyl chloride (Fe2O3/TiO2/PVC) nanocomposites in tablet form were investigated in the photodegradation of methylene blue (MB) under simulated sunlight, and their possible antibacterial effects were examined. The newly synthesized nanocomposites were characterized by scanning electron microscope, X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, and Raman spectroscopy. The results showed a hematite crystal form in the case of Fe2O3(2) and Fe2O3 samples, while the Fe2O3(1) sample showed a combination of hematite and synthetic mineral akaganeite. The highest photocatalytic efficiency was achieved in the presence of Fe2O3/TiO2/PVC, when 70.6% of MB was removed. In addition, the possible photo-cleaning and reuse of the mentioned photocatalyst was also examined. Based on the results, it can be seen that the activity did not decrease after five successive runs. Nanocomposites also exhibited mild antibacterial effects against the two tested Gram-positive bacteria (S. aureus and B. cereus).

Synthesis of Bimetallic BiPO4/ZnO Nanocomposite: Enhanced Photocatalytic Dye Degradation and Antibacterial Applications.

Multidrug-resistant strains (MDRs) are becoming a major concern in a variety of settings, including water treatment and the medical industry. Well-dispersed catalysts such as BiPO4, ZnO nanoparticles (NPs), and different ratios of BiPO4/ZnO nanocomposites (NCs) were synthesized through hydrothermal treatments. The morphological behavior of the prepared catalysts was characterized using XRD, Raman spectra, PL, UV-Vis diffuse reflectance spectroscopy (UV-DRS), SEM, EDX, and Fe-SEM. MDRs were isolated and identified by the 16s rDNA technique as belonging to B. flexus, B. filamentosus, P. stutzeri, and A. baumannii. The antibacterial activity against MDRs and the photocatalytic methylene blue (MB) dye degradation activity of the synthesized NPs and NCs were studied. The results demonstrate that the prepared BiPO4/ZnO-NCs (B1Z4-75:300; NCs-4) caused a maximum growth inhibition of 20 mm against A. baumannii and a minimum growth inhibition of 12 mm against B. filamentosus at 80 μg mL-1 concentrations of the NPs and NCs. Thus, NCs-4 might be a suitable alternative to further explore and develop as an antibacterial agent. The obtained results statistically justified the data (p ≤ 0.05) via one-way analysis of variance (ANOVA). According to the results of the antibacterial and photocatalytic study, we selected the best bimetallic NCs-4 for the photoexcited antibacterial effect of MDRs, including Gram ve+ and Gram ve- strains, via UV light irradiation. The flower-like NCs-4 composites showed more effectiveness than those of BiPO4, ZnO, and other ratios of NCs. The results encourage the development of flower-like NCs-4 to enhance the photocatalytic antibacterial technique for water purification.

Solution combustion synthesis of novel PrFeO3/CeO2 nanocomposite with enhanced photo-Fenton activity under visible light

In this study, we successfully synthesized PrFeO3/CeO2-based nanocomposites with different mass contents of СeO2 (0–18 wt%) via solution combustion with subsequent heat treatment in air. The results of EDXS and PXRD confirmed the presence of two phases in nanocomposites: a PrFeO3 orthorhombic phase with an average crystallite size of 13.6–36.6 nm and a СeO2 cubic phase in the form of an ultradisperse phase with an average particle size of 7.4–11.5 nm depending on the mass content of СeO2. We characterized the morphology, porosity, and specific surface structure of the powders by scanning electron microscopy, transmission electron microscopy, and adsorption–structural analysis, which established the foam-like morphology of nanopowders with a predominantly mesoporous structure. The specific surface area varied in the range of 8.8–19.4 m2/g for different СeO2 contents. We studied the optoelectronic properties of the nanocomposites with UV–visible diffuse reflection spectroscopy, which determined the values of the band gap of the PrFeO3 phase actively absorbing radiation in the visible region (2.07–2.13 eV). Based on the adsorption–photocatalytic properties of the obtained nanocomposites, we established the presence of a synergistic effect from the addition of CeO2 to PrFeO3. We studied the adsorption capacity of the samples during the adsorption of methyl violet, and we analyzed the resulting adsorption isotherm in accordance with the Freundlich model. The obtained results indicated increased dye adsorption in the presence of CeO2, with the maximum value of Kf = 45.7 observed at 15 wt%. We studied the photocatalytic Fenton-like activity of nanopowders during the degradation of methyl violet under the influence of visible light. We established he presence of a positive effect of CeO2 additive. At 9 wt% content, the maximum photocatalytic reaction rate constant was reached at 0.056 min−1, which was previously unavailable for analogical Fenton-like photocatalysts based on REE orthoferrites. Based on the conducted studies, we propose a possible mechanism of the photo-Fenton-like decomposition of organic pollutants in the presence of PrFeO3/CeO2 under the influence of visible light. The obtained nanocomposite materials were also characterized by high cyclic stability and the potential for magnetically controlled separation from the reaction solution, showing their potential as a basis for photocatalysts in wastewater treatment from dyes and other organic pollutants.

Facile Green Synthesis of ZnO NPs and Plasmonic Ag-Supported ZnO Nanocomposite for Photocatalytic Degradation of Methylene Blue

Removing organic pollutants, textile dyes, and pharmaceutical wastes from the water bodies has become an essential requirement for a safe environment. Therefore, the present study aimed to prepare semiconductor zinc oxide nanoparticles (ZnO NPs) and plasmonic Ag-supported ZnO nanocomposite (ZnO–Ag) using an environmentally friendly bio-approach as an alternative to hazardous synthesis approaches. ZnO NPs and ZnO–Ag nanocomposite were characterized by using UV–Vis diffuse reflectance spectroscopy (UV–DRS) (the Ag-supported ZnO nanocomposite exhibited an absorption band between 450–550 nm, attributed to the Ag NPs surface plasmon resonance (SPR)), Photoluminescence (PL) spectral investigation, which revealed the PL emission intensity of ZnO–Ag NPs was lower than pure ZnO NPs, describing an extended electron-hole pair (e--h+) lifespan of photogenerated charge carriers, Fourier transform infrared spectroscopy (FTIR), FT-Raman, and X-ray diffraction (XRD) analyses were deduced. In addition, energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) were performed and further ascertained the successful biosynthesis and thermally stable ZnO Nps and ZnO–Ag nanocomposite. The as-prepared ZnO–Ag nanocomposite displayed increased photocatalytic characteristics due to the decline in the bandgap energy from 3.02 eV (ZnO NPs) to 2.90 eV (ZnO–Ag nanocomposite). The photocatalytic activity of the developed nanocomposite for the degradation of methylene blue (MB) dye, a primary textile industry released water-pollutant, was conducted under UV light irradiation. Meanwhile, the maximum % degradation of MB dye molecules was attained by 98.0 % after 60 min exposure of UV-light irradiation. Increased photocatalytic activity of ZnO–Ag nanocomposites and a faster rate of MB degradation were achieved by the deposition of plasmonic Ag NPs and the surface plasmon resonance (SPR) effect possessed by Ag NPs. The primary oxidative route that resulted in MB degradation was the production of hydroxyl radicals (OH•). The SPR effect of the photocatalyst induced the synergistic enhancement of the optical response and separation of the photo-induced charge carriers. The combined study gives comprehensive information and directions for future research on noble metal-modified nanocatalysts for direct applications in the photocatalytic degradation of textile and organic wastes in water.

Guest molecular guided syntheses of 2-dimensional uranyl complexes with rigid benzenedicarboxylate ligands

Two new heterometallic uranyl-organic frameworks (UOFs), [Cd(phen)2(H2O)2][(UO2)2(BDC)3]·2H2O (1) and [Ni(phen)3][(UO2)2(BDC)3]·2H2O (2), were obtained under hydrothermal conditions. Both crystal structures were characterized by single-crystal X-ray diffraction analyses and the results indicate that both complexes feature a similar 2D honeycomb framework that is connected by rigid benzenedicarboxylate (BDC) ligands and uranyl units. BDC works as a linker to bridge neighboring UO2 2+ units, where UO2 2+ is tris-chelated. Different guest molecules guided the stacking of 2D layers and lead into their 3D supramolecular crystal structures with different space groups. As a result, 1 crystallized in a polar space group Cc, whereas 2 belongs to a chiral space group P6122. Thermogravimetric measurements were performed to study their thermal stability. UV-visible diffuse reflectance spectroscopy measurements indicate an experimental optical bandgap of 3.87 eV and 3.63 eV, respectively, for 1 and 2. Luminescent studies of both samples show strong green light emissions.

A Z-scheme BiYO3/g-C3N4 heterojunction photocatalyst for the degradation of organic pollutants under visible light irradiation.

Photocatalysis is one of the fascinating fields for the wastewater treatment. In this regard, the present study deals with an effective visible light active BiYO3/g-C3N4 heterojunction nanocomposite photocatalyst with various ratios of BiYO3 and g-C3N4 (1:3, 1:1 and 3:1), synthesised by a wet chemical approach. The as-synthesised nanocomposite photocatalysts were investigated via different physicochemical approaches like Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electrons microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and photoelectrochemical studies to characterise the crystal structure, morphology, optical absorption characteristics and photoelectrochemical properties. The photocatalytic degradation ability of the prepared photocatalytic samples was also analysed through the degradation of RhB in the presence of visible light irradiation. Of all the synthesised photocatalysts, the optimised CB-1 composite showed a significant photocatalytic efficiency (88.7%), with excellent stability and recyclability after three cycles. O2•- and •OH radicals were found to act a major role in the RhB degradation using optimised CB-1 composite, and it possessed ~ 1 times greater photocurrent intensity than the pristine g-C3N4 and BiYO3. In the present work, a direct Z-scheme heterojunction BiYO3/g-C3N4 with a considerably improved photocatalytic performance is reported.

Preparation and characterization of Ce-MOF/g-C3N4 composites and evaluation of their photocatalytic performance

In this study, unique hybrid structures were constructed between a Ce-based metal-organic framework (Ce-MOF) and graphitic carbon nitride (g-C3N4) materials. In addition, the g-C3N4 materials used for these heterostructures were prepared by five different methods, namely the conventional pyrolysis method, chemical exfoliation by a strong acid, activation by an alkaline hydrothermal treatment, melamine-cyanuric acid supramolecular assembly with a mechanochemical method, and by the solvothermally pre-treated method. The structural and morphological properties of the resulting g-C3N4 sheets and their composites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), thermogravimetric analysis-derivative thermogravimetry (TGA-DTG), diffuse reflectance UV–vis spectroscopy (UV–vis DRS) and N2 sorption-desorption isotherms (BET). Finally, the photocatalytic performance of the composites was determined by following the photocatalytic degradation of methylene blue (MB) in an aqueous solution under UV–visible light irradiation. It was found that the photocatalytic efficiency of the Ce-MOF/g-C3N4‒TS composite was significantly higher than that of their counterparts (Ce-MOF or g-C3N4‒TS) for the photocatalytic degradation of MB. When employing the composite, UV light-induced degradation of MB yielded an efficiency of 96.5% after 120 min for a dye solution containing 10 mg/L MB. This corresponds to a 5-fold or 2-fold improvement of the rate constant (k) when compared to the Ce-MOF or g-C3N4, respectively.

Self-Assembled Synthesis of Porous Iron-Doped Graphitic Carbon Nitride Nanostructures for Efficient Photocatalytic Hydrogen Evolution and Nitrogen Fixation

In this study, Fe-doped graphitic carbon nitride (Fe-MCNC) with varying Fe contents was synthesized via a supramolecular approach, followed by thermal exfoliation, and was then used for accelerated photocatalytic hydrogen evolution and nitrogen fixation. Various techniques were used to study the physicochemical properties of the MCN (g-C3N4 from melamine) and Fe-MCNC (MCN for g-C3N4 and C for cyanuric acid) catalysts. The field emission scanning electron microscopy (FE-SEM) images clearly demonstrate that the morphology of Fe-MCNC changes from planar sheets to porous, partially twisted (partially developed nanotube and nanorod) nanostructures. The elemental mapping study confirms the uniform distribution of Fe on the MCNC surface. The X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectroscopy (UV-DRS) results suggest that the Fe species might exist in the Fe3+ state and form Fe-N bonds with N atoms, thereby extending the visible light absorption areas and decreasing the band gap of MCN. Furthermore, doping with precise amounts of Fe might induce exfoliation and increase the specific surface area, but excessive Fe could destroy the MCN structure. The optimized Fe-MCNC nanostructure had a specific surface area of 23.6 m2 g-1, which was 8.1 times greater than that of MCN (2.89 m2 g-1). To study its photocatalytic properties, the nanostructure was tested for photocatalytic hydrogen evolution and nitrogen fixation; 2Fe-MCNC shows the highest photocatalytic activity, which is approximately 13.3 times and 2.4 times better, respectively, than MCN-1H. Due to its high efficiency and stability, the Fe-MCNC nanostructure is a promising and ideal photocatalyst for a wide range of applications.

One-pot microwave synthesized high-performance BiVO4/InVO4 heterojunction for photocatalytic reduction of Cr6+

A series of BiVO4/InVO4 composites were synthesized by one-pot microwave method based on the ratio regulation of Bi/In. Consequently, the as-fabricated BiVO4/InVO4 photocatalysts performed higher photocatalytic activities (100%) than pure InVO4 and BiVO4. The prepared photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV–vis diffuse reflection spectroscopy (UV–vis DRS) and Fourier transform infrared spectra (FTIR). The results indicate the formation of BiVO4/InVO4 and it possesses enhanced solar light absorption. The enhanced reduction rate is ascribed to the efficient separation of photogenerated charge carriers due to the heterojunction formed between BiVO4 and InVO4. The possible photocatalytic mechanism of BiVO4/InVO4 composite was also discussed in detail.

Carbon and oxygen co-doped phosphotungstate for high performance photocatalytic degradation of imidacloprid

Carbon and oxygen co-doped phosphotungstate were successfully prepared by one-pot thermal treatment with phosphotungstic acid (HPW) and melamine-cyanuric acid supramolecule (MCA) as precursors. Based on the results of X-ray photoelectron spectra (XPS), UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and Photoluminescence (PL) measurements, the existence of CO in CNPW-8-420 has been confirmed. Carbon and oxygen which are co-doped as CO in the Keggin structure of phosphotungstate are contributed to the separation of charge carriers and can increase the amount of the photocatalysis active sites. With the amount of HPW increasing, MCA decomposed in CNPW-8-420 and CNPW-20-420 without synthesizing g-C3N4, leading to in-situ doped of CO. Furthermore, the increase of treatment temperature can cause the supramolecular structure of MCA to overbreak, leading to carbon and nitrogen elements doped in CNPW-8-500. The photocatalytic degradation efficiency rate constant of CNPW-8-420 is 0.40 h−1 and it can be reused 3 times with no obvious change. LC−MS/MS revealed the most likely photocatalytic degradation pathway and intermediates of imidacloprid including imidacloprid olefin, guanidine-type imidacloprid, imidacloprid urea, 6-chloronicotinic acid, 5-hydroxy-imidacloprid, and 4,5-dihydroxy-imidacloprid. This study provides a promising strategy for the construction of co-doped POMs photocatalysts using different supramolecule precursors.

G-C3N4 supported Ag/AgCl@MIL-88A MOF based triple composites for highly efficient diuron photodegradation under visible LED light irradiation

In this work, a series of g-C3N4 supported Ag/AgCl doped MIL-88A composites were synthesized and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), and photoluminescence spectroscopy (PL). The photocatalytic performances of as-prepared composites were examined by the photodegradation of diuron (DRN), which is used as an herbicide in agriculture. The composites exhibit exceptional visible-light photocatalytic activities for photodegradation of DRN with complete degradation within 60 min in the absence of oxidants. However, in the presence of H2O2 or persulfate, complete degradation of DRN was achieved in 15 min and 30 min, respectively. The photocatalyst also gave very high conversions in water containing dissolved inorganic salts and natural organic matter (NOM). The Ag/AgCl@MIL-88A/g-C3N4 composite retained excellent photocatalytic properties after repeated use. Radical trapping experiments revealed that the most important reactive species in the photodegradation were O2−• and h+. Role of active radicals were discussed via proposed degradation mechanism for the degradation of DRN in the presence of MIL-88A/g-C3N4 and Ag/AgCl@MIL-88A/g-C3N4.