UV Vis Diffuse Reflectance Spectroscopy Research Articles

The Effect of Titanium Oxyfluoride Morphology on Photocatalytic Activity of Fluorine-Doped Titanium(IV) Oxide

Titanium oxyfluoride (TiOF2) is a metastable product that can be obtained in a fluorine-rich environment. This material can also be a valuable precursor in the synthesis of titanium(IV) oxide (TiO2). However, the effect of TiOF2 morphology on the physicochemical properties of TiO2 has not been studied so far. In this work, single-phase TiOF2 was prepared by a solvothermal method. The as-synthesized samples exhibited a variety of morphologies, including different shapes and crystallite sizes. These materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS), surface area measurements, thermal gravimetric analysis (TGA) and UV–vis diffuse reflectance spectroscopy (DR/UV–vis). Furthermore, TiOF2 samples were used as precursors in the synthesis of fluorine-doped titanium(IV) oxide and applied in photocatalytic phenol degradation under UV-vis light. The experiments showed that the crystallite size of the precursor, as well as the number of fluoride ions used in the synthesis, were the predominant factors that affected the photocatalytic activity of the final photocatalyst.

Synthesis, characterization of BiOI/rGO nanocomposite and its photocatalytic functionality analysis under visible light

Visible light responding pristine BiOI and BiOI/rGO nanocomposites were prepared using hydrothermal method. The physicochemical characteristics of BiOI and BiOI/rGO composite were studied through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), high resolution transmission electronmicroscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and UV–vis diffuse reflectance spectroscopy (UV–vis-DRS) techniques. The photocatalytic performance of the synthesized material was analysed against Methylene Blue dye. The photocatalytic activity of BiOI, and BiOI/rGO revealed the degradation of MB about 68 % and 92 %, respectively for a period of 60 min which indicated the enhancement of degradation efficiency for BiOI/rGO compared to BiOI.

A comparative study of band gap engineered in-situ and ex-situ MWCNTs/TiO2 heterostructures for their enhanced photocatalytic activity under visible light

Organic pollutants, such as various types of organic dyes coming out from the textile industries, are polluting surface and groundwater resources alarmingly and posing a threat to aquatic ecosystems. So, the demand for visible-light-driven high-performance photocatalysts having high activity and structural stability is a need of an hour. TiO2 has been one of the well-known and most studied semiconductor photocatalysts for decades. But its low electron-hole pair (e-/h+) recombination time reduces its efficiency, and the large band gap restricts its use as a visible-light-driven photocatalyst. To overcome these limitations of TiO2, herein, we have reported an in-situ and ex-situ MWCNTs modified TiO2 heterostructure nanocomposites photocatalyst and established a comparative study in terms of their ability to degrade methylene blue (MB) dye under visible light irradiation. The as-synthesized in-situ CNTs-TiO2 nanocomposite and ex-situ CNTs-TiO2 nanocomposite were characterized structurally, morphologically, compositionally, and optically through various characterization techniques such as XRD, RAMAN, SEM, XPS, FTIR, and UV–Vis diffuse reflectance spectroscopy. The result reveals the band gap tuning in the in-situ and ex-situ CNTS-TiO2 nanocomposites as a result of increasing MWCNTs concentration. The in-situ CNTs-TiO2-2 nanocomposite has high degradation efficiency (94% in 150 min) and stability due to smooth and strong chemical interactions between the MWCNTs and TiO2, while ex-situ CNTs-TiO2-20 with 10 times more MWCNTs concentration (by weight) as compared to MWCNTs concentration in in-situ CNTs-TiO2-2, exhibits degradation efficiency of 89% in 150 min. The possible degradation mechanism to degrade MB dye has also been put forward.

Composites of Lignin-Based Biochar with BiOCl for Photocatalytic Water Treatment: RSM Studies for Process Optimization

Textile effluents pose a massive threat to the aquatic environment, so, sustainable approaches for environmentally friendly multifunctional remediation methods degradation are still a challenge. In this study, composites consisting of bismuth oxyhalide nanoparticles, specifically bismuth oxychloride (BiOCl) nanoplatelets, and lignin-based biochar were synthesized following a one-step hydrolysis synthesis. The simultaneous photocatalytic and adsorptive remediation efficiency of the Biochar-BiOCl composites were studied for the removal of a benchmark azo anionic dye, methyl orange dye (MO). The influence of various parameters (such as catalyst dosage, initial dye concentration, and pH) on the photo-assisted removal was carried out and optimized using the Box-Behnken Design of RSM. The physicochemical properties of the nanomaterials were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric analysis, nitrogen sorption, and UV-Vis diffuse reflectance spectroscopy (DRS). The maximum dye removal was observed at a catalyst dosage of 1.39 g/L, an initial dye concentration of 41.8 mg/L, and a pH of 3.15. The experiment performed under optimized conditions resulted in 100% degradation of the MO after 60 min of light exposure. The incorporation of activated biochar had a positive impact on the photocatalytic performance of the BiOCl photocatalyst for removing the MO due to favorable changes in the surface morphology, optical absorption, and specific surface area and hence the dispersion of the photo-active nanoparticles leading to more photocatalytic active sites. This study is within the frames of the design and development of green-oriented nanomaterials of low cost for advanced (waste)water treatment applications.

4,4'-(Anthracene-9,10-diylbis(ethyne-2,1-diyl))bis(1-methyl-1-pyridinium) Lead Iodide C30H22N2Pb2I6: A Highly Luminescent, Chemically and Thermally Stable One-Dimensional Hybrid Iodoplumbate.

A new one-dimensional hybrid iodoplumbate, namely, 4,4'-(anthracene-9,10-diylbis(ethyne-2,1-diyl))bis(1-methyl-1-pyridinium) lead iodide C30H22N2Pb2I6 (AEPyPbI), is reported here for the first time with its complete characterization. The material exhibits remarkable thermal stability (up to 300 °C), and it is unreactive under ambient conditions toward water and atmospheric oxygen, due to the quaternary nature of the nitrogen atoms present in the organic cation. The cation exhibits strong visible fluorescence under ultraviolet (UV) irradiation, and when its iodide is combined with PbI2, it forms AEPyPb2I6, an efficient light-emitting material, with a photoluminescence emission intensity comparable to that of high-quality InP epilayers. The structure determination was obtained using three-dimensional electron diffraction, and the material was extensively studied by using a wide range of techniques, such as X-ray powder diffraction, diffuse reflectance UV-visible spectroscopy, thermogravimetry-differential thermal analysis, elemental analysis, Raman and infrared spectroscopies, and photoluminescence spectroscopy. The emissive properties of the material were correlated with its electronic structure by using state-of-the-art theoretical calculations. The complex, highly conjugated electronic structure of the cation interacts strongly with that of the Pb-I network, giving rise to the peculiar optoelectronic properties of AEPyPb2I6. The material, considering its relatively easy synthesis and stability, shows promise for light-emitting and photovoltaic devices. The use of highly conjugated quaternary ammonium cations may be useful for the development of new hybrid iodoplumbates and perovskites with optoelectronic properties tailored for specific applications.

Ternary Polyaniline@Bi2O3-BiOCl Nanocomposites as Innovative Highly Active Photocatalysts for the Removal of the Dye under Solar Light Irradiation.

Ternary PANI@Bi2O3-BiOCl nanocomposites were successfully synthesized during the oxidative polymerization of aniline monomer in the presence of Bi2O3. PANI@Bi2O3-BiOCl nanocomposites were characterized by several analytical techniques, including X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), N2 physisorption, UV-Vis Diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The effective PANI-semiconductor interaction promotes the fast separation and transfer of photogenerated electrons and holes, enhancing the photocatalytic efficiency of the materials towards methylene blue (MB) degradation under solar light irradiation. The best results were obtained by 0.5%PANI@Bi2O3-BiOCl, leading to 80% MB degradation in 2 h, four times higher than pristine Bi2O3-BiOCl. Moreover, 0.5%PANI@Bi2O3-BiOCl maintained stable photocatalytic performances for four cycles without significant activity loss. Various scavengers (isopropyl alcohol, formic acid, and benzoquinone) were used to identify the active species by trapping holes and radicals generated during the photocatalytic degradation process. Finally, a probable photocatalytic mechanism of PANI@Bi2O3-BiOCl photocatalyst was suggested.

Photocatalytic properties of Ni1-xFexO nanoparticles synthesized by a freeze-drying process

Ni1-xFexO nanoparticles were synthesized by heat treatment at 600 °C of the powder resulting from lyophilization of the aqueous mixture of nickel and iron acetate, and their photocatalytic properties were tested. The nanoparticles were preliminarily characterized by X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, and UV-VIS diffuse reflectance spectroscopy. The results revealed monophasic samples up to x = 0.04 and that increasing iron concentration decreased the particle size and bandgap. The photocatalytic activity of Ni1-xFexO (x = 0.00, 0.02 and x = 0.04) samples under UV irradiation was investigated using the Reactive Blue 250 as a molecule test. Photocatalytic tests showed that Ni0.98Fe0.02O nanoparticles performed the best, which was attributed to the bandgap of this sample, presenting the smallest among the tested samples.

Synthesis of MnSe-Based GO Composites as Effective Photocatalyst for Environmental Remediations.

In this work, a manganese selenide/graphene oxide (MnSe/GO)-based composite was prepared for wet-chemical assisted method against organic dye; herein, methylene blue (MB) dye removal from the water was employed as a metal selenide-based photocatalyst. The synthesized MnSe/GO composite was systematically characterized by X-ray diffraction (XRD), Fourier transform electron microscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and UV-visible diffuse reflectance spectroscopy (UV-vis. DRS). The structural characteristic revealed the adequate synthesis of the sample with good crystallinity and purity of the obtained products. The morphological analysis indicates the formation of MnSe nanoflakes composed of tiny particles on their surface. At the same time, the GO nanosheets with high aggregation were formed, which may be due to the van der Waals forces. The bond interaction and compositional analysis studies confirmed and supported the structural findings with high purity. The optical analysis showed the bandgap energies of MnSe and their composites MnSe (1.7 eV), 7% GO-MnSe (2.42 eV), 14% GO-MnSe (2.6 eV), 21% GO-MnSe (3.02 eV), and 28% GO-MnSe (3.24 eV) respectively, which increase the bandgap energy after GO and MnSe recombination. Among different contents, the optimized 21% GO-MnSe composite displayed enhanced photocatalytic properties. For instance, a short time of 90 min was taken compared with other concentrations due to the narrow bandgap of MnSe and the highly conductive charge carrier's support, making the process to remove MB from water faster. These results show that the selenide-based photocatalyst can be an attractive candidate for future advanced photocatalysis applications.

Fabrication of La, Ce co-doped ZnO nanorods for improving photodegradation of methylene blue

La, Ce co-doped ZnO nanorods (ZnLC) were synthesized through a one-step solvothermal route. The photocatalysts were characterized by X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. The La and Ce doping enhanced the visible light absorption ability of ZnLC and a red shift was detected for ZnLC. Under simulated solar light irradiation, the ZnO doped with 3 at% La and 1 at% Ce (ZnLC1) degrades methylene blue (MB) more effectively than those of pure ZnO, La-doped ZnO (ZnL) and commercially available ZnO. The improved photocatalytic performance of ZnLC1 can be attributed to the high charge separation efficiency as demonstrated by the photoluminescence spectra. Additionally, the photocatalytic experiments reveal that several parameters have their own impact on the MB degradation. Using a variety of radical scavengers, it is discovered that superoxide anion radical plays a crucial role in the degradation of MB. The ZnLC1 is also reused several times without noticeable decrease of photoactivity, indicating that it has a substantial potential for environmental remediation applications.

Preparation of a g-C3N4/Ag3PO4 composite Z-type photocatalyst and photocatalytic degradation of Ofloxacin: Degradation performance, reaction mechanism, degradation pathway and toxicity evaluation

In this study, a g-C3N4/Ag3PO4 composite Z-heterojunction photocatalyst was prepared with a simple in situ deposition method, and was first applied to the degradation of Ofloxacin (OFX). When the theoretical g-C3N4 to Ag3PO4 mass ratio was 1:10 (denoted as AC-10), the OFX degradation was optimal, and the degradation efficiency reached 71.9 % within 10 min. Steady state fluorescence emission spectroscopy (PL), electrochemical impedance spectroscopy (EIS), transient photocurrent (I-t) and N2 adsorption-desorption (BET) studies showed that AC-10 had the best charge separation efficiency and highest specific surface area. Additionally, the effects of AC-10 dosage, OFX concentration, pH value, anions, humic acid and water source on the degradation process were also studied. A cycling experiment showed that AC-10 exhibited good stability. Three-dimensional excitation-emission matrix spectroscopy (3D EEMs), LC-MS data and ECOSAR models were used to explore the process for degradation of OFX and predict the biotoxicities of byproducts, and these results indicated that the catalyst was environmentally friendly. In addition, electron spin resonance (ESR) experiments and capture of the active species showed that photogenerated holes (h+) played a major role in the reaction. Finally, the optical properties and the energy band structure of the catalyst were analyzed by UVvis diffuse reflectance spectroscopy (DRS) and Mott-Schottky (M-S) methods, and a Z-type heterojunction charge transfer mechanism was proposed.

Enhancing the Photocatalytic Activity of TiO2 for the Degradation of Congo Red Dye by Adjusting the Ultrasonication Regime Applied in Its Synthesis Procedure

Recently, the ultrasound-assisted sol-gel synthesis procedure of mesoporous titania (TiO2) photocatalysts caught the researcher’s attention, due to the physicochemical properties enhancement of the resulting titania nanomaterials. Thus, by varying different synthesis parameters particular characteristics could be obtained. In the present study, the ultrasound pulse on/off ratio has been considered and the effect of the envisaged parameter on the textural, morphological, and optical features of titania nanomaterial has been investigated. Therefore, X-ray Diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), N2-sorption measurements, SEM imaging, and UV-Vis Diffuse Reflectance spectroscopy (UVDR) have been used. And further, the photocatalytic activity of the prepared TiO2 materials was evaluated by the features developed about the applied ultrasound pulse on/off ratio as 1/1, 2/1, 3/1, 4/1, 1/3 and 2/2. It was found that the ultrasound pulse on/off ratio considered in the synthesis procedure of titania leads to TiO2 materials with different textural (SBET = 98–156 m2/g), morphological, and optical (Eg = 3.1–3.2 eV) characteristics. For this reason, TiO2 nanomaterials prepared were found to exhibit suitable features for photocatalytic applications. Thus, the TiO2 4.1 sample prepared at 4/1 ultrasound pulse on/off ratio revealed the highest photodegradation efficiency of Congo Red dye (98.28%) as the results of photocatalytic tests show. More than that, a possible reaction mechanism of the CR photodegradation process through the contribution of reactive oxygen species (·HO, ·O2−), holes (h+), and electrons (e−) of developed titania photocatalyst was proposed.

Controlled and environmentally friendly hydrothermal synthesis of nano-V4O9 plate-like for photocatalytic degradation of methyl orange under solar irradiation

Nano-V4O9 plate-like morphology has been synthesized by hydrothermal treatment using vanadium oxide (V2O5) as vanadium source and 3-amino-1-propanol (H2N–(CH2)3–OH) as reducing and structure-directing agent, for the first time. The structural and morphological properties of the nano-V4O9 were investigated by X-ray diffraction (XRD), infrared spectroscopy and scanning electron microscopy (SEM). XRD study demonstrated the existence of orthorhombic structure V4O9 with high crystallinity. SEM micrographs revealed that the particles have a plate-like morphology with uniform size distribution whose thickness is on the order of 46 nm. The formation mechanism of V4O9 nanoplates has also been proposed. Optical properties of the as-synthesized samples were investigated by UV–visible diffuse reflection spectroscopy and room temperature photoluminescence. This study shows that when the hydrothermal treatment was carried out for 96 h, the band gap can be estimated at 3.832 eV. The photoactivity of V4O9 nanoplates was evaluated in the degradation of methyl orange under solar irradiation.

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.