Ultraviolet-visible Diffuse Reflectance Spectroscopy Research Articles

Nghiên cứu tổng hợp vật liệu composite SiO2/g-C3N4 cho quá trình quang xúc tác phân hủy rhodamine B

In this study, a visible-light-driven SiO2/g–C3N4 composite was prepared by heating a mixture of SiO2 and urea. The products were characterized by X-ray diffraction (XRD), infrared spectra (IR), scanning electron microscopy (SEM), and ultraviolet–visible diffuse reflectance spectroscopy (UV-Vis DRS). Results indicate that the composite only contained SiO2 and g-C3N4, and the SiO2/g–C3N4 composite had higher photocatalytic activities in the degradation of rhodamine B (82.2%) compared to the pristine g-C3N4 (43.9%) under visible light. The SiO2/g–C3N4 composite is a promising new material for the photodegradation of organic pollutants in wastewater due to its high photocatalytic performance, low cost, and convenient collection for reuse.

La-doped MIL-88B(Fe)-NH2: a mixed-metal-organic framework photocatalyst for highly efficient reduction of Cr(vi) in an aqueous solution.

With the aim to resolve the problem of water pollution, we herein propose a new photocatalyst based on metal-organic frameworks (MOFs), called La-doped MIL-88B(Fe)-NH2 (MIL-88B((1 - x)Fe/xLa)-NH2), which was designed and employed for the photocatalytic reduction of Cr(vi) in aqueous solutions. MIL-88B((1-x)Fe/xLa)-NH2 materials with different x values were synthesized via a one-pot solvothermal method. Their characteristics were investigated using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Brunauer-Emmett-Teller (BET) analysis, Fourier-transform infrared (FT-IR) spectroscopy and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). We found that compared to pristine MIL-88B(Fe)-NH2 with a photocatalytic efficiency of 67.08, MIL-88B((1 - x)Fe/xLa)-NH2 materials with x = 0.010, 0.025 and 0.050 exhibit excellent photocatalytic efficiencies reaching 88.21, 81.19 and 80.26%, respectively, after only 30 minutes of irradiation at a small catalyst dosage of 0.2 g L-1. These La-doped MIL-88B(Fe)-NH2 photocatalysts can work well under mild conditions (pH = 6). Furthermore, they are robust-can be recycled for at least four consecutive runs without any activity loss. This novel material is promising for the photocatalytic degradation of pollutants.

Visible-light response ZnO/CuCo2O4 nanocomposite: Vibrational, optical, structural, morphological, photocatalytic, and kinetic analyses

Compatible nanoparticle properties in photocatalytic applications are crucial. Within the scope of this investigation, we constructed a nanocomposite of ZnO and CuCo2O4 (ZnO/CuCo2O4) to boost the photocatalytic properties of ZnO by constructing ZnO/CuCo2O4 nanocomposite using Artocarpus altilis leaves extracts (AALE). Essential secondary metabolites contribute to the origin of weak bases and capping agents to form the spherical shape of ZnO/CuCo2O4. X-ray diffractometry (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), scanning electron microscope - energy dispersive X-ray spectroscopy (SEM-EDX) are some of the techniques that are utilized for the validation of nanocomposite properties, such as vibrational, crystallinity, band gap, morphology, particle size, and elemental composition. The formation of ZnO/CuCo2O4 decreased the bandgap energy and enhanced the photocatalytic performance by 93.01 % under visible light irradiation for 2 h. ZnO/CuCo2O4 followed pseudo-second-order kinetic in the photodegradation of malachite green (MG). It is noted that the increase in photocatalytic characteristics can be brought about by the narrower band gap of ZnO and increased kinetic rate toward dye degradation. Radical species analysis was of utmost importance in acknowledging that holes (h+) were the most crucial species that were indispensable to MG degradation. The photodegradation efficiency of the recycled catalyst only declines by approximately 12 % after five cycles of consumption. This study demonstrates a compelling method using plant extracts to prepare visible-light response ZnO-based nanocomposites for better photocatalytic activity and stability.

Catharanthus roseus-mediated CuAl2O4 nanocomposites for evaluation of killing kinetics

The present article portrayed on the killing kinetic of human pathogenic bacteria using bioinspired mesoporous CuAl2O4 nanocomposites (NCs). The NCs was fabricated using leaf extract of medicinal plant Catharanthus roseus (CR) as a green reducer and stabilizer. As bio-fabricated material was calcined at 800 °C and characterized by several analytical techniques like X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV-DRS), Energy Dispersive X-Ray Spectroscopy (EDS), X-Ray Photoelectron Spectroscopy (XPS), Raman, Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) to authenticate its structure, phase, chemical bonding, chemical state, size and morphology behaviors. XRD and TEM revealed a reduced crystallite and nanoscale sizes of biosynthesized NCs. Moreover, XRD study exposed a cubic-structure of material, while transmission electron microscopy rendered an average particles size in range 10–15 nm. However, BET profile advocates a mesoporous nature of the particles. An effective biological molecular docking modulation assessed by substituting natural inhibitor by bioinspired NCs, while the protein PDB ID 4Z8D FabH as a receptor site for the present investigation. After assessment of molecular docking examination, the antibacterial activity of bioinspired NCs were performed against Staphylococcus aureus, Bacillus subtillis, Klebsiella pneumoniae and Escherichia coli using agar-well method. The broth culture method was employed on different pathogenic strains by kinetic growth assays and colony forming unit.

Low dose, high function: Visible light photocatalytic performance of in-situ sensitized Ti3+/Ov self-doped rutile TiO2-x nanorods with a small amount of ultrathin g-C3N4 nanosheets

Harnessing solar energy for photocatalytic sewage purification represents a significant strategy for addressing water pollution. This study focused on synthesizing ultrathin g-C3N4 nanosheets through ultrasonic refluxing g-C3N4 aggregates in a mixture of water and triethylamine. Subsequently, Ti3+/oxygen vacancy (Ov) self-doped rutile TiO2 (TiO2-x) nanorods were synthesized via an in-situ mixed solvothermal reaction. By sensitizing a minimal quantity of these ultrathin g-C3N4 nanosheets, a Z-scheme heterojunction with reduced rutile TiO2-x nanorods was achieved. Various analytical techniques were employed, including X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), and transient photocurrent analysis. These methods determined the phase, structure, morphology, and photoelectrochemical properties of the fabricated materials. The visible light photocatalytic performance was tested using rhodamine B, methyl orange, and Cr2O72- solutions as simulated pollutants and three distinct types of actual wastewater from a pharmaceutical factory as photocatalytic degradation object. The findings revealed that Ti3+/Ov self-doping significantly enhances the visible light responsiveness of rutile TiO2. The integration of minimal amounts of ultrathin g-C3N4 nanosheets with rutile TiO2-x nanorods, formed via an in-situ mixed solvothermal reaction, effectively promoted the separation of photogenerated electrons and holes, thereby increasing the photocatalytic efficiency. Interestingly, increasing the g-C3N4 content in the mixture led to an increase in the number of defects within TiO2-x and a reduction in crystallinity. Wastewater treatments yielded varied results: wastewater containing solely phenols underwent effective photocatalytic degradation, while samples with high salt content or complex compositions proved more challenging. This study demonstrated that the heterojunction formed by sensitizing rutile TiO2-x nanorods with a small amount of ultrathin g-C3N4 nanosheets retained remarkable photocatalytic activity. These findings offer valuable insights for the design of effective photocatalysts and their application in sewage treatment.

Antibacterial and antiviral PA6-AgNPs microfibers for application as a filter element in facial respirators

Polymeric microfibers are very interesting materials that can be associated with other nanomaterials aiming to obtain specific properties and be used in a wide range of applications. In this study, we prepared different formulations of polyamide 6 (PA6) containing silver nanoparticles (AgNPs) and produced microfibers by solution blow spinning technique for its use as a filter element in a face respirator. The obtained samples were then characterized by field emission gun-scanning electron microscopy (FEG-SEM), energy dispersion spectroscopy (EDS), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), water contact angle (WCA), thermogravimetric analysis (TGA), and respirability and antibacterial, antiviral and cytotoxicity assays. In general, the microfibers were well dispersed and the AgNPs were evenly distributed throughout the samples, reflecting a hydrophilic character and good thermal stability, with a maximum weight loss of 2.9 % attributed to the evaporation of water molecules. The sample produced with a concentration of 10 mmol/L of silver nitrate presented acceptable levels of resistance to respiration. Concerning the microbiological analyses, the results showed that samples evidenced antibacterial effect against Escherichia coli and Staphylococcus aureus, forming inhibition halos of up to 4 mm in disk diffusion assays and inhibiting bacterial growth in liquid medium assays, as well as antiviral effect against betacoronavirus MHV-3, promoting a reduction of up to 99.9 % of viral particles. Moreover, the samples presented cytotoxicity on the first and second days, whereas on the seventh day some of the extracts did not show cytotoxic activity, indicating that the cells adapted to the culture medium. Considering the data set and the simple process of obtaining the microfibers, it was possible to conclude that this material can be applied as a filter element in a face respirator as well as in a variety of products with antibacterial and antiviral purposes.

Exploring the gas sensing potential of BiOBr0.9I0.1: A highly responsive sensor for ammonia detection at room temperature

Bismuth halide oxides (BiOX, where X = Cl, Br, I) are renowned in photocatalysis for their distinct layered structure, modifiable band gap, and affordability. However, their application in gas sensing has garnered comparatively less research attention. Notably, solid solutions of BiOX demonstrate superior attributes over pure BiOX compounds. BiOBrxI1-x solid solution was successfully synthesized using in situ precipitation method and used as a gas-sensitive material for ammonia (NH3) gas sensor. The structural and compositional integrity of the synthesized samples was meticulously confirmed by X-ray diffraction (XRD), which revealed the coexistence of different BiOBr and BiOI phases. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) provided insights into the morphology, revealing a flower-like nanostructure, which favors the surface reaction rate. The electronic and optical properties of the material were further elucidated by photoluminescence (PL) spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy (UV-DRS), which revealed that the band gap is tailored to facilitate the sensitivity and selectivity of ammonia detection. Key properties including surface area and porosity were quantitatively evaluated by Bruner-Emmett-Taylor (BET) analysis and found BiOBr0.9I0.1 sensor to have a specific surface area of 13.08 m2/g. Specifically, the BiOBr0.9I0.1 sensor's response ratio (Ra/Rg) to 100 ppm of ammonia reaches 8, approximately fourfold higher than that of the pure BiOBr sensor. The flower-like morphology of BiOBr0.9I0.1 enhances surface activity and charge transfer efficiency, thereby facilitating greater gas adsorption and elevating sensor performance. The rapid response and recovery times (12/24 s at 30 ppm), low detection threshold (LOD, 0.75 ppm), along with its selectivity and reproducibility at room temperature, position the BiOBr0.9I0.1 material as a promising candidate for ammonia gas detection.

Preparation, characterization and photocatalytic studies of defect pyrochlore, KMn0·33Te1·67O6 and its composite with g-C3N4

Skeletal materials belonging to the defect pyrochlore family have been the subject of considerable interest due to their remarkable properties. In this work, a highly efficient, stable and visible light active composite photocatalytic system consisting of defect pyrochlore of composition KMn0·33Te1·67O6 (KMnTeO) and g-C3N4 (g-CN) has been successfully prepared by simple physical mixing of pre-prepared KMnTeO and g-CN components synthesized in solid state and thermal treatment of low-cost melamine, respectively. Structural, morphological and optical properties of as-prepared catalysts were deduced from powder X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR), Raman, Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (FESEM-EDX), Transmission Electron Microscopy-High Resolution Transmission Electron Microscopy (TEM-HRTEM), Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV–Vis DRS), X-ray Photoelectron Spectroscopy (XPS) and Photoluminescence (PL) measurements. The lattice parameter “a” of parent KMnTeO was obtained from Rietveld refinement of its powder XRD pattern. The FT-IR and Raman spectra of KMnTeO gave characteristic bands belonging to the defect pyrochlore structure. The photocatalytic activities of KMnTeO and composite KMnTeO-g-CN were evaluated by the degradation of methylene blue (MB). Scavenger experiments were carried out to identify the reactive species responsible for the degradation of MB. Furthermore, the reusability and stability of the photocatalysts were explored. The probable photocatalytic mechanism for MB degradation over the composite KMnTeO-g-CN was surmised according to the scavenger experiments. The work provides a new approach for the development of novel defect pyrochlore based composite photocatalysts to treat industrial wastewater containing organic pollutants.

Visible-light-driven photocatalytic degradation of doxycycline using TiO2/g-C3N4/BIOCHAR catalyst

Abstract TiO2/g-C3N4/biochar (TCNBC) catalysts were prepared by the hydrolysis method for the photocatalytic degradation of doxycycline antibiotic (DC), with biochar obtained from the pyrolysis of Phragmites australis. The catalysts were examined using scanning electron microscope (SEM), transmission microscopy (TEM), energy dispersive X-ray spectrometer (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL), and ultraviolet-visible diffuse reflectance spectroscopy (UV–Vis DRS) and nitrogen adsorption/desorption. The photocatalytic activity results showed that the TCNBC catalyst exhibited higher catalytic activity than pure TiO2 or g-C3N4. Its peak catalytic activity, achieving a decomposition efficiency of 91.93% and a mineralization efficiency of 81.50%, can be attributed to the synergistic effect of biochar, TiO2, and g-C3N4. Even after four cycles of use, the catalyst still maintained relatively high activity for the degradation of DC. The photocatalytic degradation efficiency of TCNBC decreased from 91.93% to 86.30% after four recycling events.

Improved antimicrobial activities of biphasic titania nanowires against Gram-negative and Gram-positive bacteria

This research focused on the synthesis of biphasic titania nanowires from commercially available anatase titania via hydrothermal method to improve its antimicrobial activity. The electron microscope scanning (SEM) showed that the titania nanowires structures were successfully synthesized with width varying from 17 to 96 nm and length from 0.7 to 8 μm. The titania nanowires have biphasic structure of brookite and anatase, as observed from the X-ray diffraction pattern. The band gap was calculated from the ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) spectra at 3.3eV, which is between the range of pure anatase and pure brookite band gap. The crystallite size of the titania nanowires was calculated using the Scherer equation and showed a much smaller crystallite size compared to commercial titania. The antimicrobial activity of the titania nanowires was then investigated against gram-negative and gram-positive bacteria. They exhibited improved antimicrobial activity against the Gram-negative Pseudomonas aeruginosa and Escherichia coli along with Gram-positive Bacillus subtilis. Interestingly, their inhibition zone was comparable to the antibiotic tetracycline. Meanwhile, the commercial titania did not show any antimicrobial activity on any tested bacterial strains. The improved antimicrobial activity of the titania nanowires was attributed to its biphasic phase, small particle size, and its one-dimensional morphology.

Facile fabrication of bifunctional ternary nanocomposite (FCPTNC) as an efficient catalyst for 4-nitrophenol reduction and crystal violet photodegradation

The synthesis of a ternary nanocomposite Fe3O4/CuO-Ppy (FCPTNC) was effectively achieved via hydrothermal and in-situ chemical oxidative polymerisation techniques. FCPTNC was used as a catalyst for reducing the toxic compound 4-nitrophenol to the non-toxic compound 4-aminophenol. Additionally, it was utilised for the visible-light-induced degradation of the crystal violet (CV) dye. FCPTNC underwent characterisation using various techniques, namely X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), ultraviolet–visible diffuse reflectance spectroscopy (UV-DRS), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). The successful preparation of the nanocomposite was validated through analysis of its structural properties. Moreover, examining its optical properties indicated that the nanocomposite can effectively operate through visible light irradiation. The catalyst demonstrated exceptional catalytic efficacy in eliminating the targeted organic pollutants, namely 4-nitrophenol (4-NP) and crystal violet (CV). The catalyst exhibited a degradation efficiency of 97 % for CV dye within60 min. It achievedthecomplete conversion of 4-nitrophenol into its corresponding amino derivative within15 min. The calculated first-order rate constants for the reduction of 4-NP and photodegradation of CV dye were found to be in the range of 0.53–11.6 × 10−2 min−1 and 3.2–5.6 × 10−2 min−1, respectively. The magnetic catalyst exhibited efficient separation from the reaction media and was successfully recycled for up to fiveconsecutive cycles with negligible loss of catalytic activity. The work demonstrates that the FCPTNC nanocomposite has favourable characteristics, such as facilesynthesis, efficient catalytic activity, and reusability. These findings suggest that the nanocomposite possesses desirable efficiency and durability, rendering it a promising catalyst for environmental applications.

Formation of amygdalin/β-cyclodextrin derivatives inclusion complexes for anticancer activity assessment in human cervical carcinoma HeLa cell line

Nanoencapsulation has gained considerable attention because of its unique features and advantages in anticancer drug delivery. Amygdalin (AMY) is an anticancer compound, showing limitations in its applications by low stability. Herein, the inclusion complexes (ICs) of AMY with β-cyclodextrin (βCD), and its derivatives such as 2-hydroxypropyl-βCD (HPβCD) and methyl-βCD (MβCD) were fabricated. The fabricated AMY/CD-ICs were thoroughly evaluated using Fourier-transform infrared spectroscopy, powder X-ray diffraction, thermogravimetric/differential thermal analysis, proton nuclear magnetic resonance, ultraviolet–visible diffuse reflectance spectroscopy, and photoluminescence techniques. Double reciprocal profile study of the absorption and fluorescence spectra revealed that the AMY formed the ICs with βCD derivatives at a guest/host stoichiometric ratio of 1/1. The thermal stability of AMY was enhanced as the IC formation aid observed by the shift of thermal degradation temperature of AMY from the range of ∼ 220–250 °C to > 295 °C. Theoretical analyses of the energetic, electronic, and global reactivity parameters of the AMY/CD-ICs were evaluated using the PM3 method. Further assessment of the dissolution diagrams of AMY/CD-ICs revealed a burst release profile. In addition, cell toxicity was evaluated using the MTT assay, and the results showed that AMY/CD-ICs had significantly more efficacious in inhibiting HeLa cancer cells than AMY. These results proved that the IC formations with CDs significantly enhanced the anticancer activity of AMY.

Synergistic photocatalytic removal of moxifloxacin from aqueous solutions using ZnO-Fe3O4-chitosan composites

The escalating contamination of water bodies with antibiotic residues is an urgent environmental and public health issue. This study aimed to fabricate an innovative photocatalytic composite (CMZ) by combining chitosan, magnetic iron oxide (Fe3O4), and zinc oxide (ZnO) for efficiently removing antibiotic moxifloxacin (MFX) water. Comprehensive characterization of the fabricated CMZ was performed using various techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), photoluminescence spectroscopy (PL) and nitrogen adsorption/desorption isotherm analysis. The synergistic incorporation of ZnO, Fe3O4, and chitosan in the CMZ composite altered the structural properties of ZnO and chitosan The band gap energy of CMZ was 2.58 eV, significantly boosting its photocatalytic effectiveness under visible light exposure. The CMZ composites exhibited a high efficiency in catalyzing MFX degradation in aqueous environments. The optimal conditions for MFX degradation were established, including a neutral pH level of 7, a 90 min exposure to irradiation, and employing 0.1 g of the CMZ catalyst. The degradation process obeyed closely to the first-order kinetic model. The CMZ material showed consistently high performance in degrading MFX across four consecutive reuse cycles, emphasizing its practical applicability for mitigating antibiotic pollution.

Photocatalytic ozonation-based degradation of phenol by ZnO–TiO2 nanocomposites in spinning disk reactor

Spinning disk reactor (SDR) has emerged as a novel process intensification photocatalytic reactor, and it has higher mass transfer efficiency and photon utilization for the degradation of toxic organic pollutants by advanced oxidation processes (AOPs). In this study, ZnO–TiO2 nanocomposites were prepared by sol-gel method, and coated on the disk of SDR by impregnation-pull-drying-calcination method. The performance of catalyst was characterized by X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, photoluminescence and ultraviolet–visible diffuse reflectance spectroscopy. Photocatalytic ozonation in SDR was used to remove phenol, and various factors on degradation effect were studied in detail. The results showed that the rate of degradation and mineralization reached 100% and 83.4% under UV light irradiation after 50 min, compared with photocatalysis and ozonation, the removal rate increased by 69.3% and 34.7%, and mineralization rate increased by 56.7% and 62.9%, which indicated that the coupling of photocatalysis and ozonation had a synergistic effect. The radical capture experiments demonstrated that the active species such as photogenerated holes (h+), hydroxyl radicals (·OH), superoxide radical (·O2−) were responsible for phenol degradation, and ·OH played a leading role in the degradation process, while h+ and ·O2− played a non-leading role.

Azo chromophore functionalized polyesters; Synthesis, characterizations and applications for efficient Electrocatalyst for oxygen evolution reaction and heavy metal ion detection

The current study focuses on the synthesis, characterization and investigation of the potential applications of azo chromophore functionalized polyesters and their composites with graphene derivatives. Employing the two-step diazotization coupling reaction, diazo diol monomers are synthesized. Subsequently, the azo polyesters are prepared via low-temperature solution polycondensation of the diazo diols with diacid chloride followed by the incorporation of graphene derivatives to obtain composite materials. Characterization techniques including Fourier transform Infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Ultraviolet-Visible Diffuse reflectance spectroscopy (UV–Vis DRS) and Scanning electron microscopy (SEM) are employed to evaluate the chain structure, degree of crystallinity, optical properties and morphology. Further, their electrocatalytic activity towards the oxygen evolution reaction (OER) and detection ability toward heavy metal ion was evaluated. The results demonstrate enhanced catalytic and detection capabilities attributed to synergistic interactions between polymer and graphene components. This study provides significant insights into the development of efficient polymer-graphene hybrid materials, with potential applications in green chemistry and environmental monitoring.

Photocatalytic degradation of methylene blue under visible light by cobalt ferrite nanoparticles/graphene quantum dots.

A simple approach was developed to synthesize cobalt ferrite nanoparticles/graphene quantum dots (CF/GQDs). The material was prepared from a homogeneous mixture of iron nitrate, cobalt nitrate, and starch at 140, 180 and 200 °C in a 24 h thermal hydrolysis process. The obtained materials were characterised by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, photoluminescence spectroscopy, vibrating-sample magnetometry, and nitrogen adsorption/desorption isotherms. Cobalt ferrite crystals of around 8-10 nm and graphene quantum dots formed directly at 200 °C. Stacking GQDs sheets onto the CF nanoparticles resulted in CF/GQDs nanoparticles. The nanocomposite exhibits satisfactory fluorescent and superparamagnetic properties, which are vital for catalytic applications. The CF/GQDs catalyse significantly the degradation of methylene blue (MB) under visible light. The catalyst can be recycled with an external magnetic field and displays suitable stability. Also, it was reused in three successive experiments with a loss of efficiency of about 5%. The CF/GQDs are considered as an efficient photocatalyst for MB degradation and other dyes.

Optical CuAl2O4 used as photocatalyst for IC dye degradation

ABSTRACT The nanocrystalline copper aluminate (CuAl2O4) has been successfully synthesized by a simple, economical, and environmentally friendly solid-state mechanochemical (MCH) method. The prepared sample was characterized by a variety of suitable methods employed, including scanning electron microscopy (SEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), Fourier transform infrared spectroscopy (FT-IR), and X-ray powder diffraction (XRD). The material's average particle size was 55 nm and stoichiometric. CuAl2O4 has been found to exhibit potent photocatalytic activity toward indigo carmine (IC) when subjected to UV light. Under UV radiation, 10 mg CuAl2O4 leads to 99 ± 1% degradation of an 8 ppm IC dye solution among 2 ppm, 4 ppm, 6 ppm, 8 ppm, and 10 ppm in 25 min. In addition, a prospective liquid chromatography-mass spectrometry (LC-MS) technique is identified in the current work, which provides potential routes for the photocatalytic breakdown of IC. Even after five consecutive cycles, the photocatalyst showed remarkable reusability and stability.

Spatial Distribution of Brønsted Acid Sites Determines the Mobility of Reactive Cu Ions in the Cu-SSZ-13 Catalyst during the Selective Catalytic Reduction of NOx with NH3.

The formation of dimer-Cu species, which serve as the active sites of the low-temperature selective catalytic reduction of NOx with NH3 (NH3-SCR), relies on the mobility of CuI species in the channels of the Cu-SSZ-13 catalysts. Herein, the key role of framework Brønsted acid sites in the mobility of reactive Cu ions was elucidated via a combination of density functional theory calculations, in situ impedance spectroscopy, and in situ diffuse reflectance ultraviolet-visible spectroscopy. When the number of framework Al sites decreases, the Brønsted acid sites decrease, leading to a systematic increase in the diffusion barrier for [Cu(NH3)2]+ and less formation of highly reactive dimer-Cu species, which inhibits the low-temperature NH3-SCR reactivity and vice versa. When the spatial distribution of Al sites is uneven, the [Cu(NH3)2]+ complexes tend to migrate from an Al-poor cage to an Al-rich cage (e.g., cage with paired Al sites), which effectively accelerates the formation of dimer-Cu species and hence promotes the SCR reaction. These findings unveil the mechanism by which framework Brønsted acid sites influence the intercage diffusion and reactivity of [Cu(NH3)2]+ complexes in Cu-SSZ-13 catalysts and provide new insights for the development of zeolite-based catalysts with excellent SCR activity by regulating the microscopic spatial distribution of framework Brønsted acid sites.

Optical and dielectric properties of divalent copper based double perovskite compound, Gd2CuTiO6

In this work, we have investigated high temperature dielectric properties and room temperature optical properties on rare earth ion based orthorhombic Gd2CuTiO6 (GCTO). Optical properties like reflectance and band gap were determined from ultra-violet visible (UV–Vis) diffuse reflectance spectroscopy technique and photoluminescence (PL) spectrum. The compound exhibited substantial optical absorption and emission in the visible region. Our findings reveal the presence of an intermediate band, as evidenced by the difference between the band gap values obtained from the Tauc plot using the diffuse reflectance spectrum (3.07 eV) and the PL spectrum (2.4 eV). Furthermore, thermogravimetric analysis demonstrated high thermal stability with <0.4% change in mass over a wide temperature range of 30 °C–1200 °C in air environment. Moreover, lead-halide free compound, GCTO is highly thermally stable oxide double perovskite with wide band gap and absorption in the UV–Vis range are highly suitable for optical applications In addition, dielectric properties of the compound have been examined using impedance spectroscopy as a function of frequency ranging from 500 Hz to 1 MHz and temperature between 300 K and 550 K. Compounds with relaxor behaviour at high temperatures and high thermal stability are desired for several applications. Because of the cation disorders present in this compound, GCTO displays dielectric relaxor behaviour indicative of a distribution of relaxation times. Furthermore, the frequency-dependent modulus illustrated a thermally activated conduction mechanism. Cole–Cole plots of electrical modulus suggest prominent grain contribution above 350 K.

Carbon-doped Bi2MoO6 nanosheet self-assembled microspheres for photocatalytic degradation of organic dyes

Abstract In this paper, carbon-doped Bi2MoO6 (C-Bi2MoO6) nanosheet self-assembled microspheres were prepared by using the solvothermal-calcination route to improve the photocatalytic activity of Bi2MoO6. The characterization results of x-ray diffractometry, Fourier transform infrared spectrometry, Raman scattering, scanning electron microscopy, transmission electron microscopy, BET specific surface area test, and x-ray photoelectron spectrometry indicated that C replaced the O2− anion in the Bi2MoO6 lattice, thinning the nanosheets, decreasing the size of the microspheres, and increasing the specific surface area of the Bi2MoO6. Ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence, electrochemical impedance spectroscopy, transient photocurrent, and linear sweep voltammetry (LSV) spectroscopy demonstrated that the carbon doping reduced the band gap energy, raised the conduction band, and enhanced the photogenerated electron–hole pairs separation efficiency of Bi2MoO6. Benefiting from these favorable changes, the C-Bi2MoO6 microspheres prepared at a molar ratio of C to Bi of 4 (4C-Bi2MoO6) exhibited the highest photocatalytic activity, and the photocatalytic degradation rate constant of rhodamine B by 4C-Bi2MoO6 microspheres was almost 2.26 times that by pristine Bi2MoO6 under simulated solar light. 4C-Bi2MoO6 microspheres (0.2 g/L) presented excellent photocatalytic performance toward RhB (20 mg/L) at pH value 1 and could remove 98.31% of the RhB within 120 min. In addition, 4C-Bi2MoO6 microspheres also possessed a high photocatalytic activity toward methylene blue and tetracycline. 4C-Bi2MoO6 microspheres assembled from thin nanosheets can be used as effective photocatalysts to degrade toxic organic molecules from wastewater.