Ultraviolet-visible Diffuse Reflectance Spectroscopy Research Articles

Effect of carbon nanotube incorporation on the photocatalytic activity of TiO2 nanotubes

Arrays of titanium dioxide (TiO2) nanotubes were prepared on commercially pure titanium (Ti) foils by anodic oxidation in a 0.5 M hydrofluoric acid (HF)-based electrolyte with multiwalled carbon nanotubes (MWCNTs) up to 0.035 g/l. The samples were annealed at 450°C for 1 h after anodic oxidation to form a crystalline anatase structure. The effect of MWCNT addition on the morphology and photocatalytic activity of the nanostructures was characterized by scanning electron microscopy, Raman spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence spectroscopy and methylene blue degradation tests. The results showed that MWCNTs were successfully incorporated into the titanium dioxide nanotube structure and significantly affected its photocatalytic activity. The best photocatalytic performance was achieved with the use of 0.025 g/l MWCNTs in the electrolyte composition. However, when the MWCNT content in the electrolyte increased, the electron–hole recombination rate and photon absorption ability of the structure deteriorated, resulting in a decreased photocatalytic activity.

Optical, magnetic, and electrochemical properties of a fluorite-perovskite Ce0.9Gd0.1O2-∂ - La0.6Sr0.4FeO3-∂ nanocomposite synthesized by one pot sol-gel auto-combustion route

Gadolinium-doped cerium oxide (Ce0.9Gd0.1O2-∂; CGO) and strontium-doped lanthanum ferrite (La0.6Sr0.4FeO3; LSF) are well-known compounds for their application in solid oxide fuel cells, dense oxygen permeable membrane, and high-temperature ceramic reactor. The superior electro-catalytic performance of these two individual oxides or their composites is well established as it originates from multivalent cations (Ce3+/4+ and Fe2+/3+/4+) and doping-induced defects like electrons, holes, and oxygen vacancies. This work focuses on synthesizing and characterizing composite taking CGO and LSF in different weight ratios, i.e., 10:90, 30:70, 50:50, 70:30, and 90:10 by sol-gel auto-combustion process. End members CGO and LSF were also synthesized for comparison purposes. All synthesized nanopowders (single phases and their composites) were characterized with X-ray diffraction (XRD) for phase identification and Scanning electron microscopy (SEM) for elemental composition analysis. XRD and SEM results established the formation of the required phase and targeted composition. The optical properties of the materials were evaluated with the help of ultraviolet–visible Diffuse Reflectance Spectroscopy (UV–Vis DRS). Tauc's approximation measured band gap energies, and all the composites showed a very high band gap in the 4.85–5 eV range. Magnetic properties such as saturation magnetization (Ms), remanence (Mr), and coercive force (Hc) were calculated from a magnetic hysteresis loop obtained from the Vibrating-sample magnetometer (VSM) experiment at room temperature. Furthermore, the law of approach to saturation (LAS) model was applied to more precisely calculate Ms and other essential parameters. In magnetic characterization, the LSF phase fraction controls the overall magnetic property of the composites. Electrochemical behavior, such as the composites' charge storage ability and stability were tested by cyclic voltammetry and chronopotentiometry method. All the samples exhibited good stability, and the highest specific capacitance of 26 F/gm was obtained for the composite sample (CL91) when only 10 % LSF phase was incorporated in the nanocomposite.

Interface engineering of 0D/2D Cu2O/BiOBr Z-scheme heterojunction for efficient degradation of sulfamethoxazole: Mechanism, degradation pathway, and DFT calculation

Constructed heterojunction has been considered an efficient strategy to enhance the migration and transfer of photoinduced charge carriers. Herein, a Z-scheme Cu2O/BiOBr heterojunction with 0D/2D structure was fabricated by microwave hydrothermal method. It was found that the optimal composites photocatalyst showed excellent activity for sulfamethoxazole (SMZ) illumination, and the removal rate reached 90.7%, which was higher than pristine Cu2O (53.0%) and BiOBr (60.0%). Subsequently, the operational parameters such as catalyst dosage, concentrations of pollutants, and pH of solution were investigated. According to the ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRs), Mott-Schottky curve, and density functional theory (DFT) analysis, the Z-scheme degradation mechanism of Cu2O/BiOBr heterostructure was proposed. Among them, the interface structure of 0-dimensions/2-dimensions (0D/2D) can significantly increase the number of heterojunctions in the composite catalyst, and Z-scheme heterostructures can accelerate the generation and migration of photoinduced charge carriers, which has a facilitation effect on improving the decomposition activity of the photocatalyst. Moreover, three possible pathways for SMZ degradation were inferred. This study provides a promising strategy for constructing novel heterojunctions with high photocatalytic performance.

Construction of highly efficient CuS/CdS nanostructure for enhanced solar H2 evolution

The fabrication of efficient photocatalytic system for enhanced production of hydrogen is exceptionally thought-provoking.To address this issue herein we fabricated the CuS/CdS heterostructures by ultrasonication for photocatalytic H2 production. The structural integrity of the produced heterostructure is confirmed by the aid of analytical tools such as X-ray diffraction studies (XRD), Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV–vis DRS), scanning electron microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The fabricated CuS/CdS sample exhibited the highest H2 production rate (824 μmol/g) than CuS (67 μmol/g) and CdS (135 μmol/g) under simulated solar illumination. The hydrogen output is noticeably enhanced due to improved absorption of visible light and competent charge carrier partition. It was confirmed by UV–vis diffuse reflectivity and photoluminescence spectra (PL) as charge carrier parting was effective as absorption of visible light was enhanced. A plausible photocatalytic H2 reaction mechanism has been elucidated from increased charge carrier division and visible light absorptivity. This work depicts a new approach for greatly resourceful nano architecture for energy-related applications.

A facile synthesized Z-scheme Bi2O3/SnS/Ag ternary nanocomposite: An expedited visible photocatalysis by plasmonic silver for efficient organic decontamination

A facile precipitation and deposition method was used to synthesize the binary Bi2O3/SnS (2 & 4 wt %) and ternary Bi2O3/SnS (2 wt %)/Ag (2, 4, 6 & 8 wt %) nanocomposites. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL) spectroscopy, energy dispersive X-Ray (EDX) spectroscopy, field emission scanning electron microscopy (FESEM) and photocatalytic degradation studies were carried out on all the nanomaterials for identify their characteristics and properties. Rhodamine B (RhB), an organic pollutant was taken to examine the photocatalytic efficacy of the resultant nanomaterials under visible light. Bi2O3/SnS and Bi2O3/SnS/Ag photocatalysts revealed the maximum activity in the acidic medium (pH = 3). As photocatalysts, ternary Bi2O3/SnS (2 wt %)/Ag (6 wt %) nanocomposite showed magnificent performance in the degradation of RhB dye (99.77% degradation in 50 min) as compared to binary Bi2O3/SnS (2 wt %) nanocomposite (99.02% degradation in 50 min). This is due to the formation of heterojunctions and deposition of Ag increasing the transfer of electrons through junction and resulting in intensifying the life expectancy of charged species and increasing the photocatalytic ability of Bi2O3/SnS/Ag nanocomposite. The role of trapping agents during the degradation process of RhB was also studied.

Preparation of PANI modified TiO2 and characterization under pre- and post- photocatalytic conditions.

Polyaniline (PANI) is a promising conducting polymer for surface modification of TiO2 to overcome limitations of the use of visible light and attain increased photocatalytic efficiency for the removal of organic contaminants. In this study, a series of polyaniline modified TiO2 (PANI-TiO2) composites were prepared by using "in-situ" chemical oxidation polymerization method. The composites were systematically characterized by Fourier transform infrared spectroscopy (equipped with an attenuated total reflection accessory, FTIR-ATR), Raman spectroscopy, X-ray diffractometry (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDAX), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL), nitrogen (N2) physisorption (Brunauer - Emmett - Teller surface area (SBET) and Barrett-Joyner-Halenda (BJH) pore size analysis), thermogravimetry-derivative thermogravimetry (TG-DTG) techniques. XRD patterns of PANI-TiO2 composites confirmed both the amorphous phase of PANI and the crystalline character of TiO2. TG/DTG analysis complemented the XRD profiles that the interactions between PANI and TiO2 resulted in a more stable PANI-TiO2 matrix. SEM images displayed the dominant morphology as dandelion-like shapes of PANI being more pronounced with increasing PANI ratios in PANI-TiO2 composites. UV-DRS profiles revealed that the band gap energies of the composites were lower than bare TiO2 expressing a shift to the visible light region. Both PL and UV-DRS analyses confirmed the band-gap reduction phenomenon of PANI modification of TiO2. The incorporation of PANI into TiO2 resulted in a reduction of the surface area of TiO2. The composites were subsequently subjected to photocatalytic activity assessment tests using humic acid (HA) as a model of refractory organic matter (RfOM) under simulated solar irradiation (Uyguner-Demirel et al. Environ Sci Pollut Res 30 85626-85638, 2023). The morphological and structural changes attained upon application of photocatalysis were also evaluated by FTIR-ATR, Raman spectroscopy, XRD, and SEM-EDAX methods in a comparable manner. The FTIR-ATR spectral features of PANI, RfOM and all composites displayed peaks with slight shifts under pre- and post- photocatalytic conditions as well as following dark surface interactions. Besides exhibiting noticeable photocatalytic performance, PANI-TiO2 composites were also proven to maintain stability under non-selective oxidation conditions in the presence of a complex organic matrix. The prepared PANI-TiO2 composites overcoming the limitations of UVA light active bare TiO2 photocatalysis could possibly find a beneficial use as potential catalysts in solar photocatalytic applications.

Visible light-driven Z-scheme Bi2O3/CuBi2O4 heterojunction with dual metal ions cycle for PMS activation and Lev degradation

In this study, Bi2O3/CuBi2O4 composite was prepared by sol–gel method, which was used to degrade levofloxacin (Lev) by the synergistic effect of visible light and peroxymonosulfate (PMS). The physicochemical properties of Bi2O3/CuBi2O4 were regulated by varying the molar ratio of the raw materials. The structure and morphology of the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS). Secondly, Bi2O3/CuBi2O4/Vis/PMS system was constructed to investigate the effects of different conditions (pollutant concentration, catalyst dosage, PMS concentration, pH and different anion concentration) on the removal effect of Lev. Benefit from the highly ordered alternating nanoparticles and nanosheets, Bi2O3/CuBi2O4 showed satisfactory PMS activation ability than single Bi2O3. The degradation rate increased from 12.98 ± 2.41% (Bi2O3) to 70.62 ± 0.07% (Bi2O3/CuBi2O4) within 120 min. Finally, the quenching experiments and electron paramagnetic resonance (EPR) results showed that radical pathways (h+, SO4-·, ·OH) and non-radical pathways (1O2) were both involved in the PMS activation process. The main reaction mechanism of Bi2O3/CuBi2O4/Vis/PMS system was predicted, the unique electron transfer pathway of Z-scheme heterojunction and Cu(II)/Cu(I), Bi(V)/Bi(III) redox-cycle on the catalyst surface effectively drove the generation of radicals, realizing the high efficiency of pollutant degradation.

Nickel ferrite/graphene oxide material: synthesis and photocatalytic degradation study of Rhodamine B

In this work, a simple approach was taken to prepare a nickel ferrite based on graphene oxide magnetic photocatalyst (NF/GO). The NF/GO composite was synthesized by a one-step hydrothermal method and characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray elemental mapping analysis (EDX-Mapping), vibrating sample magnetometer (VSM) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The research results showed that the photocatalytic degradation of the Rhodamine B (RhB) by visible light radiation occurs more efficiently when there was a combination of NiFe2O4 nanoparticles with graphene oxide sheets compared individual component materials.

Carbon Dots Modification Surface of Titanium Dioxide and Their Photocatalytic Activity

This work, we develop the efficient visible-light-responsive titanium dioxide photocatalyst using carbon dots as a sensitizer (C-dots/TiO2). C-dots was synthesized via a simple one-pot reaction by microwave-assisted pyrolysis method using orange juice as carbon precursors. C-dots/TiO2 samples were prepared by a facile route. Moreover, the micro-structure and optical properties of as-prepared C-dots/TiO2 have been evaluated using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and ultraviolet–visible diffuse reflection spectroscopy (DRS). The modification surface of TiO2 with carbon dots enhanced the light absorption in visible region. The photocatalytic properties of as-prepared pure TiO2 and C-dots/TiO2 were also explored indigo carmine decolorization under visible light. The photocatalytic results revealed that the C-dots/TiO2 exhibited higher catalytic performance than the pure TiO2 under visible light.

Optimization of Visible-Light-Driven Ciprofloxacin Degradation Using a Z-Scheme Semiconductor MgFe2O4/UiO-67.

A heterogeneous photocatalyst, MgFe2O4/UiO-67 (MU-x), was successfully synthesized by doping magnetic magnesium ferrite nanoparticles (MgFe2O4) with the UiO-67 metal-organic framework at various weight ratios (MgFe2O4: UiO-67 at 30, 50, 70, and 90 wt %). Various techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) , Brunauer-Emmett-Teller (BET), photoluminescence (PL), vibrating sample magnetometry (VSM), electrochemical impedance spectroscopy (EIS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), were used to characterize the prepared photocatalysts. The photocatalytic performance of MU-x in the degradation of ciprofloxacin (CIP) under visible light was assessed. The CIP degradation efficiency was found to increase as the amount of MgFe2O4 in the composite was increased up to 70 wt %. Experimental conditions were optimized using response surface methodology (RSM) based on central composite design (CCD) with three factors: initial pH, catalyst loading, and CIP concentration. Using the obtained model, the optimal conditions were determined as follows: initial pH of 8.025, catalyst loading of 33.8 wt %, and CIP concentration of 10.8 mg/L. Under these optimal conditions, a notable improvement was achieved, with 99.62% of CIP removal achieved within 90 min, surpassing the performance of previously reported photocatalysts. Total organic carbon (TOC) analysis revealed a high degree of mineralization, at 81.25%. The degradation pathway of CIP was investigated based on liquid chromatography-mass spectrometry (LC-MS) analysis. Finally, the values of ECB and EVB of the photocatalyst were determined and the possible degradation mechanism of CIP was investigated based on Mott-Schottky and the applied scavengers. The hydroxyl radical (•OH) was identified as the dominant species in the removal of CIP through a trapping experiment. The photocatalyst with 70 wt % of MgFe2O4 (MU-70) exhibited excellent stability and recoverability with an external magnet, demonstrating 86.33% CIP removal after four cycles. According to the obtained results, MU-70 is a promising visible-light-active photocatalyst with great potential for water treatment applications and convenient recovery.

1H‐Perfluorohexane—An efficient modifier for ethylene tri‐/tetramerization

Silicon‐bridged/N, P (PNSiP) ligand/Cr (III) catalyst system based on different fluorinated hydrocarbons as modifiers have been explored for ethylene selective tri‐/tetramerization. Modifiers like 1H‐Perfluorohexane (1H‐PFH), Hexafluorobenzene (HFB), and Perfluorobiphenyl (PFB) have been proven to show a significant influence on ethylene oligomerization toward 1‐hexene and 1‐octene of the catalytic system. Among them, 1H‐PFH showed the most significant promotion effect in improving activity from 0.95 × 106 g·(mol Cr·h)−1 to as much as 5.66 × 106 g·(mol Cr·h)−1 at high temperature 90°C. Through the analysis of nuclear magnetic resonance (NMR) spectroscopy and ultraviolet visible diffuse reflectance spectroscopy (UV–vis DRS) results, we concluded that 1H‐PFH can react with an amount of trimethylaluminum (TMA) contained in the cocatalyst modified methylaluminoxane (MMAO) and the solubility of Cr (III) in solvent can be increased after adding 1H‐PFH. Furthermore, the possible reaction routes of 1H‐PFH with TMA and MMAO were proposed.

Photoelectrocatalytic degradation of emerging organic pollutants in water on an FTO/BiVO4/NiS photoanode

This study demonstrates the facile synthesis of bismuth vanadate-nickel sulfide (BiVO4/NiS) heterojunction via a solvothermal process coated on a fluorine-doped tin oxide (FTO) substrate for photoelectrochemical (PEC) degradation of sulfamethoxazole (SMX) and Rhodamine B (RhB). The two semiconductors were rationally designed for the p-n heterojunction as it enhances the charge-separation and light-absorbing properties for efficient degradation of organic pollutants. The successful preparation of the BiVO4/NiS composite was confirmed using structural, morphological, and optical analysis such as X-ray diffraction (XRD), transmitted electron microscopy (TEM), energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), ultraviolet–visible diffuse reflectance spectroscopy (UV-DRS). The electrochemical and photoelectrochemical properties were investigated using electrochemical impedance spectroscopy (EIS), Mott-Schottky (M−S), and photocurrent response. Compared with the individual components, the FTO/BiVO4/NiS photoanode showed an enhanced photocurrent response of 0.4 mA/cm2 at 1.5 V potential, 16 and folds higher than the pristine BiVO4. The composite showed a band gap of 1.9 eV, 2.28 eV, and 2.18 eV for the FTO/NiS, FTO/BiVO4, and FTO/BiVO4/NiS, respectively. Moreover, the PEC degradation of the two analytes indicated that the FTO/BiVO4/NiS photoanode successfully degraded SMX (58%) and RhB (73%) in 120 min time intervals with a rate constant of 0.00755 min−1 and 0.108 min−1. Scavenger studies revealed that holes and superoxides were significant contributors to the mineralization of the analytes.

Preparation of a water‐absorbent mesoporous material and film to simulate the infrared spectrum of plants

AbstractHyperspectral imaging poses great challenges to traditional camouflage materials, primarily because there is a huge difference between the reflectance spectra of camouflage materials and natural plants in the 1400–2000 nm band. The difficulty of simulating the natural plant spectrum lies in reproducing the absorption peak of water by increasing the water content in a camouflage material. Herein, a mesoporous (MS) material is used to simulate the plant spectrum because such material can absorb and retain a large amount of water. MS was prepared via a two‐step method using tetraethyl orthosilicate and tetrabutyl titanate. The characteristics of the as‐prepared MS were examined via X‐ray diffraction, transmission electron microscopy, ultraviolet–visible diffusion reflectance spectroscopy and nitrogen adsorption–desorption isotherms. In addition, a film was prepared using the fully absorbent mesoporous material, and the water content was determined via near‐infrared spectroscopy and thermogravimetric analysis. The bonding between the mesoporous material and resin was examined via field emission gun scanning electron microscopy. The mechanical properties of the film were measured by a pendulum hardness tester and a cylindrical bending tester. The results indicate that low‐temperature synthesis followed by high‐temperature hydrothermal treatment is conducive to expanding the mesopore aperture, reaching a maximum of 23 nm. Moreover, the regular structure of the as‐prepared titanium‐containing mesoporous material is maintained under high hydrothermal temperature. The mesoporous film exhibits a good water absorption capacity of up to 80% by mass and can effectively simulate the spectrum of plants. The mechanical properties of the film are good, and the hardness of the film is related to the content of mesoporous powder. © 2023 Society of Industrial Chemistry.

A functionalized waste tire rubber powders for mitigating leaching of heavy metal ions and enhancing photocatalytic properties of rubberized cement mortar

In this study, waste tire rubber powder (R) was subjected to modification using tannic acid (TA) and ZnO to produce R-TA-ZnO composites, aiming to enhance the immobilization of heavy metal ions and improve the photocatalytic properties of rubberized cement-based materials. The characterization of R-TA-ZnO was conducted using a comprehensive range of analytical techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible-diffuse reflectance spectroscopy (UV–Vis-DRS), and other relevant methods. The findings of the study revealed that R-TA-ZnO exhibited notable hydrophilicity, surface activity, and photocatalytic properties, resulting in effective containment of the leaching of heavy metal ions. FTIR and XRD analyses confirmed the retardation of R and R-TA-ZnO. Nevertheless, the strength of the rubberized cement mortar with 5% R-TA-ZnO exceeds that of the rubberized cement mortar with 5% R (28 days) due to the interfacial bonding. The SEM and X-ray Computed Tomography (XCT) results of the rubberized cement mortar indicated that R-TA-ZnO exhibited strong binding to the cement paste, reducing both the number and size of pores. However, a high concentration of R-TA-ZnO led to the formation of larger pores, which did not contribute to the reduction of porosity. Furthermore, the rubberized mortar incorporating R-TA-ZnO displayed remarkable photocatalytic capabilities. The results of the 5-cycle degradation experiments and microscopic characterization confirmed its exceptional structural stability and reusability.

Efficient degradation of tetracycline in a photo-Fenton system constructed by combining MOF-derived Fe2O3/C/In2O3 heterojunction with vitamin C

The MOF-derived Fe2O3/C/In2O3 heterogeneous materials combined with vitamin C (AA) were first designed to construct a photo-Fenton system for the decomposition of tetracycline (TC). In this work, comparative analysis of TC degradation efficiency, photoluminescence (PL), ultraviolet-visible diffuse reflectance spectroscopy (UV–vis DRS), and transient photocurrent (I-T) performance analysis revealed that the heterojunctions not only effectively promoted the response of visible light by the catalytic system, but also facilitated the separation of photogenerated electrons and holes to increase electron density, thus, the conversion efficiency of Fe3+/Fe2+ was effectively improved, and hydrogen peroxide was activated to generate ･OH. Besides, the conversion efficiency of Fe3+/Fe2+ has been further improved due to the addition of AA, which provides many active electrons for heterogeneous materials. The capture experiments revealed that the active substances (･OH, h+, and ･O-2) played a main role in the degradation of TC. The system degraded high concentrations of TC with the efficiency of 88.9 % within 60 min. The strategy provided a new method for improving the photo-Fenton advanced oxidation performance of Fe2O3.

Green synthesis of titanium dioxide nanoparticles using Thymus vulgaris leaf extract for biological applications

In the last few decades, the biosynthesis of nanoparticles using biological agents such as microorganisms or plant extracts has gained a lot of attention due to the growing need for generating safe and non-toxic substances, cost-effective techniques, ecologically friendly solvents, and renewable materials. The aqueous leaf extract of Thymus vulgaris was used in the current investigation to achieve the biosynthesis of TiO2 nanoparticles (TiO2 NPs). In this study, leaf extract was used as a size-reducer in synthesis of TiO2. Thyme leaf extract contains flavonoids, phenols, and saponins, which function as both reducing and stabilising agents and are crucial for the synthesis of TiO2 nanoparticles. Methods such as Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), x-ray diffraction (XRD), photoluminescence (PL), and scanning electron microscopy (SEM) with energy dispersive x-ray (EDX) were used to characterise TiO2 NPs. The XRD investigations showed that titanium dioxide nanoparticles are crystalline and average crystal size is 28 nm. Gram-positive bacteria like S. aureus and B. subtilis as well as Gram-negative bacteria like Pseudomonas aeruginosa were used as standardised test microbial inoculums to evaluate the antibacterial properties of biosynthesised nanoparticles (TiO2 NPs). Against each of the studied bacteria, the TiO2 nanoparticles demonstrated significant antimicrobial activity. TiO2 nanoparticles had the maximum activity against Staphylococcus aureus, with an inhibitory zone diameter of 14 mm at 100 g ml−1. By using DPPH, hydroxyl radical techniques, the comprehensive antioxidant activity of produced NPs was examined.

G-C3N4/Chlorocobaloxime Nanocomposites as Multifunctional Electrocatalysts for Water Splitting and Energy Storage.

Due to environmental contamination and the depletion of energy supplies, it is very important to develop low-cost, high-performance, multifunctional electrocatalysts for energy conversion and storage systems. Herein, we report the development of cost-effective modified electrodes containing g-C3N4/chlorocobaloxime composites (C1-C4) and their electrocatalytic behavior toward the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), followed by their energy-storage applications. A series of chlorocobaloximes {ClCo(dpgH)2B} with diphenylglyoxime (dpgH) and neutral bases (B) containing a carboxylic acid moiety (isonicotinic acid, pyridine-3,5-dicarboxylic acid, indole-2-carboxylic acid, and p-aminobenzoic acid) have been synthesized and characterized by spectroscopic techniques. The nanocomposites of g-C3N4/chlorocobaloximes are prepared and characterized by Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), particle size distribution analysis (PSA), Brunauer-Emmett-Teller (BET), and energy dispersive X-ray analysis (EDAX) techniques. The composite coatings exhibit enhanced HER performance at lower overpotential and with a lower Tafel slope. When the water-splitting reactions are studied using 0.5 M H2SO4 and 0.5 M KOH as electrolytic solutions, the composite g-C3N4/C2 containing pyridine-3,5-dicarboxylic acid as a neutral base shows excellent HER activity with a lower overpotential of 173 mV at -10 mA cm-2 and OER activity with a lower overpotential of 303 mV. The HER reaction takes place through the Volmer-Heyrovský mechanism, where the desorption step is the rate-determining step. Among the synthesized nanocomposites, the nanocomposite g-C3N4/C2 shows higher efficiency toward both HER and OER reactions, with a lower Tafel slope of 55 mV dec-1 for HER and 114 mV dec-1 for OER than the other nanocomposites. The overall water-splitting studies of the composite g-C3N4/C2 in 0.5 M KOH indicate that the evolution of hydrogen and oxygen occurs constantly up to 120 h. The supercapacitance applications studied using cyclic voltammetry and charge-discharge studies indicate that the nanocomposite g-C3N4/C1 shows a good specific capacitance of 236 F g-1 at 0.5 A g-1 compared to others. The increased electrochemical performance of the synthesized nanocomposites is due to the incorporation of electron-withdrawing carboxylic-acid-functionalized neutral bases present in cobaloximes, which increases electron mobility. The incorporation of a cobaloxime complex into a g-C3N4 nanosheet enhances the electrocatalytic behavior of the nanosheet, and its performance can further be fine-tuned by systematic variation in the structure of cobaloxime by changing the halide ion, dioxime, the neutral base ligand, or the substituent.

UV-Light-Driven Photocatalytic Dye Degradation and Antibacterial Potentials of Biosynthesized SiO2 Nanoparticles

The present work shows the obtainment of biosynthesized SiO2 with the aid of Jasminum grandiflorum plant extract and the study of its photocatalytic ability in dye degradation and antibacterial activity. The obtained biosynthesized SiO2 nanoparticles were characterized using X-ray diffractometer analysis, Fourier transform infrared spectroscopy analysis, ultraviolet–visible diffuse reflectance spectroscopy, field-emission scanning electron microscope with energy-dispersive X-ray analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. The UV-light irradiated photocatalytic activity of the biosynthesized SiO2 nanoparticles was examined using methylene blue dye solution. Its reusability efficiency was determined over 20 cycles and compared with the commercial P-25 titanium dioxide. The bacterial resistivity of the biosynthesized SiO2 nanoparticles was examined using S. aureus and E. coli. The biosynthesized SiO2 nanoparticles showed a high level of crystallinity with no impurities, and they had an optimum crystallite size of 23 nm, a bandgap of 4 eV, no Si-OH groups and quasi-spherical shapes with Si-2p at 104 eV and O-1s at 533 eV. Their photocatalytic activity on methylene blue dye solution could reach 90% degradation after 40 min of UV light exposure, and their reusability efficiency was only 4% less than that of commercial P-25 titanium dioxide. At the concentration of 100 μg/mL, the biosynthesized SiO2 nanoparticles could allow the resistivity of E. coli to become borderline to the resistant range of an antibiotic called Amikacin.

Structural Features and Optical Properties of All-Inorganic Zero-Dimensional Halides Cs4PbBr6-xIx Obtained by Mechanochemistry.

Despite the great success of hybrid CH3NH3PbI3 perovskite in photovoltaics, ascribed to its excellent optical absorption properties, its instability toward moisture is still an insurmountable drawback. All-inorganic perovskites are much less sensitive to humidity and have potential interest for solar cell applications. Alternative strategies have been developed to design novel materials with appealing properties, which include different topologies for the octahedral arrangements from three-dimensional (3D, e.g., CsPbBr3 perovskite) or two-dimensional (2D, e.g., CsPb2Br5) to zero-dimensional (0D, i.e., without connection between octahedra), as the case of Cs4PbX6 (X = Br, I) halides. The crystal structure of these materials is complex, and their thermal evolution is unexplored. In this work, we describe the synthesis of Cs4PbBr6-xIx (x = 0, 2, 4, 6) halides by mechanochemical procedures with green credentials; these specimens display excellent crystallinity enabling a detailed structural investigation from synchrotron X-ray powder diffraction (SXRD) data, essential to revisit some features in the temperature range of 90-298 K. In all this regime, the structure is defined in the trigonal R3̅c space group (#167). The presence of Cs and X vacancies suggests some ionic mobility into the crystal structure of these 0D halides. Bond valence maps (BVMs) are useful in determining isovalent surfaces for both Cs4PbBr6 and Cs4PbI6 phases, unveiling the likely ionic pathways for cesium and bromide ions and showing a full 3D connection in the bromide phase, in contrast to the iodide one. On the other hand, the evolution of the anisotropic displacement parameters is useful to evaluate the Debye temperatures, confirming that Cs atoms have more freedom to move, while Pb is more confined at its site, likely due to a higher covalency degree in Pb-X bonds than that in Cs-X bonds. Diffuse reflectance ultraviolet-visible (UV-vis) spectroscopy shows that the optical band gap can be tuned depending on iodine content (x) in the range of 3.6-3.06 eV. From density functional theory (DFT) simulations, the general trend of reducing the band gap when Br is replaced by I is well reproduced.

In-depth opto-electrical analysis of Ni:CdS film towards the performance as Ag/Ni:CdS/FTO Schottky diode

Nickel doped cadmium sulfide (Ni:CdS) thin films are deposited onto glass and FTO substrate using spray pyrolysis technique. The effect of annealing temperature on the thin films and its morphological, microstructural, optical dispersion, linear-nonlinear and electrical, properties are extensively investigated by using various techniques such as field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM), X-ray diffraction (XRD) and ultraviolet visible (UV-VIS) diffuse reflectance spectroscopy. Morphological studies revealed that doped thin films surface is almost homogeneous and well-covered. Peaks associated with Ni, Cd and S elements are present in EDS analysis, which confirm the composition of the films. The energy band calculation using the Tauc plot from the recorded absorption spectra reveals the decrement in the energy gap from 3.75 eV to 3.61 eV and the refractive index is in the range of 2.57–2.62. The effect of annealing temperature on complex dielectric constant are also analyzed. Moreover, the dispersion of refractive index is calculated in terms of Wemple-DiDomenico approach. Third order susceptibility and nonlinear refractive index are calculated of Ni:CdS films. The designed Ag/Ni:CdS/FTO Schottky diode is tested under illumination conditions, and the empirical diode parameters, viz. ideality factor, barrier height, series resistance etc. are influenced by annealing temperature.