UV Vis Diffuse Reflectance Spectroscopy Research Articles

Facile one-step preparation of Co2CrO4 spinel from heterometallic compounds – Structural, magnetic, electrical and photocatalytic studies

Two isostructural heterometallic complex salts with mononuclear units, [NH(CH3)2(C2H5)][Cr(terpy)2][CoCl4]2 (1) and [NH(CH3)(C2H5)2][Cr(terpy)2][CoCl4]2 (2), were synthesized using a building block approach and characterized by single-crystal and powder X-ray diffraction (XRD), impedance spectroscopy and magnetization measurements. They exhibit particular humidity-sensing properties and very high proton conductivity at room temperature. The magnetization of complexes shows the high spin state of 3/2 for tetrahedrally coordinated CoII ions, which on cooling remain in the paramagnetic state within the CrIII network, which is antiferromagnetically correlated. The prepared compounds were thoroughly explored as single-source precursors for the formation of the spinel oxide Co2CrO4 by their thermal decomposition. By optimizing the annealing temperature, heating/cooling rates and holding times, the phase composition of thermal processing of 1 or 2 was evaluated: phase pure spinel Co2CrO4 was obtained by thermal treatment already at 450 °C. The structure, morphology, and optical properties of spinel oxides prepared at different temperatures were characterized using powder XRD, field emission scanning electron microscopy (SEM) and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), while electrical and magnetic by impedance spectroscopy and magnetization measurements. The determined band gap energy and nanosized crystallites prompted us to investigate the photocatalytic activity of spinel oxide produced at 450 °C in the degradation of dyes Rhodamine B (RhB) and Methylene blue (MB) under Vis irradiation without and with assistance of hydrogen peroxide (H2O2). The results show that the Co2CrO4/H2O2 system exhibits a significantly higher photoactivity response; the degradation efficiency of MB and RhB was found to be 86.1% and 80.3%, respectively. The electrical conductivity spectra and the activation energy for the DC conductivity demonstrate the electronically semiconducting behaviour of the Co2CrO4 oxide. The Co2CrO4 spinel has a ferrimagnetic ground state, with mixed CoII and CoIII ions on the tetrahedral and octahedral sites: CoII having a high spin state on both sites and CoIII having a high spin state on the tetrahedral site and a low spin state on the octahedral site. Different thermal treatments affect the magnetization according to the different sizes of the obtained crystallites.

Pb3[O10Pb20](SiO4)4X10 (X = Cl, Br): The First Pb-Containing Halogen Silicates with Mirror-Symmetric Pseudo-Aurivillius Bilayers.

Two new congruently melting Pb-containing halogen silicates, Pb3[O10Pb20](SiO4)4X10 (X = Cl, Br), have been synthesized using a high-temperature solution method. Their crystal structures were determined by single-crystal X-ray diffraction, and both compounds crystallize in the orthorhombic space group Cmca. In both structures, the mirror-symmetric bilayer composed of Pb-O polyhedra is observed for the first time in Pb-containing silicates and belongs to α-PbO derivatives and is related to the Aurivillius phase. Thermal behavior analysis, UV-vis diffuse-reflectance spectroscopy, and IR spectroscopy were also performed. The Pb3[O10Pb20](SiO4)4Cl10 matrix was doped with Eu3+ ions as a dopant, and its potential application in fluorescence was confirmed from the resulting orange-red emission.

The conductivity of Nb2O5 enhanced by the triple effect of fluorine doping, oxygen vacancy, and carbon modification for improving the lithium storage performance.

In view of the inherent pseudocapacitance, rich redox pairs (Nb5+/Nb4+ and Nb4+/Nb3+), and high lithiation potential (1.0-3.0V vs Li/Li+), Nb2O5 is considered a promising anode material. However, the inherent low electronic conductivity of Nb2O5 limits its lithium storage performance, and the rate performance after carbon modification is still unsatisfactory because the intrinsic conductivity of Nb2O5 has not been substantially improved. In this experiment, taking the improvement of the intrinsic electrical conductivity of Nb2O5 as the guiding ideology, we prepared F-doped Nb2O5@fluorocarbon composites (F-Nb2O5@FC) with a large number of oxygen vacancies by one-step annealing. As the anode electrode of lithium-ion batteries, the reversible specific capacity of F-Nb2O5@FC reaches 150 mA g-1 at 5Ag-1 after 1100 cycles, and the rate performance is particularly outstanding, with a capacity up to 130 mA g-1 at 16Ag-1, which is far superior to other Nb2O5@carbon-based anode electrodes. Compared with other single conductivity sources of Nb2O5@carbon-based composites, the electrical conductivity of F-Nb2O5@FC composites is greatly improved in many aspects, including the introduction of free electrons by F- doping, the generation of oxygen vacancies, and the provision of a three-dimensional conductive network by FC. Through analytical chemistry (work function, UV-Vis diffuse reflectance spectroscopy, and EIS) and theoretical calculations, it is proved that F-Nb2O5@FC has high electrical conductivity and realizes rapid electron transfer.

Preparation, characterization and photocatalysis performances of superparamagnetic MgFe2O4@CeO2 nanocomposites: Synthesized via an easy and green sol–gel method

The characterization of MgFe2O4@CeO2 superparamagnetic nanocomposites was thoroughly investigated using powder X-ray diffraction (XRD), a vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), dispersive X-ray analysis (EDX), elemental mapping (MAP), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) and UV–Vis diffuse reflectance spectroscopy (DRS) analyses. The photocatalytic activity of the synthesized samples was evaluated as a novel magnetic nanocatalyst for degrading Congo red (CR) dye in an aqueous solution under visible light at room conditions. The results demonstrate that the efficiency of photocatalytic degradation is higher than that of absorbance and photolysis. The degradation efficiency of photodegradation is 93% within 49% of total organic carbon removal performance. The prepared MgFe2O4@CeO2 magnetic nanocomposites (MNCs) can be easily recovered and recycled for five repeated cycles, demonstrating potential extensive efficiency in magnetic nanocomposites in wastewater and water treatment. The nanoscale morphology of MgFe2O4@CeO2 MNCs was characterized as spherical, with a size range of 35–40 nm, utilizing SEM and TEM techniques. The saturation magnetization (Ms) of the resulting nanocomposites was analyzed by VSM, revealing a value of 3.58 emu/g. Furthermore, the surface area was determined to be 27.194 m2/g using BET analysis, and the band gap was identified as 2.85 eV through DRS analysis.

Enhancing photocatalytic H2 production and dye degradation: Comparative analysis of gold reduction techniques on Au/TiO2 nanocomposites

This study compares the impact of two reduction techniques, thermal reduction (TR) and photocatalytic reduction (PR), on Au/TiO2 photocatalysts synthesized using the deposition-precipitation with urea method. Characterization methods, including temperature-programmed reduction, UV-Vis diffuse reflectance spectroscopy, electrochemical assessments (open-circuit potential and linear sweep voltammetry), and transmission electron microscopy, were employed. The 2-h. PR treatment yielded a highly effective photocatalyst (0.5Au-PR2), with 93.6% of gold nanoparticles below 4 nm, outperforming the TR counterpart (76.8%). All Au-loaded samples exhibited an absorption band between 400 and 800 nm, indicating the localized surface plasmon resonance (LSPR) effect. Interestingly, the TR catalyst had a broader LSPR band than the PR catalyst. Additionally, the 0.5Au-PR2 sample showed higher photocurrent and superior photocatalytic activity in the degradation of methyl orange and hydrogen production, which is attributed to its smaller particle size (2.9 nm) and weaker metal-support interaction. This smaller particle size emphasizes the crucial role of reduction techniques in tailoring Au/TiO2 photocatalysts for enhanced performance.

SYNTHESIS OF NICKEL-DOPED BIVO4 MATERIALS BY HYDROTHERMAL METHOD AND EVALUATE THE PHOTOCATALYTIC ABILITY TO DECOMPOSE METHYLENE BLUE UNDER VISIBLE LIGHT

Ni-doped BiVO4 photocatalysts were successfully synthesized by hydrothermal method. The catalytic samples were characterized by scanning electron microscopy (SEM), UV-vis diffuse reflection spectroscopy (DRS), photoluminescence spectroscopy (PL) and X-ray diffraction (XRD). Based on the results of PL spectrum analysis, the electron-hole recombination phenomenon is limited by the presence of the second metal Ni in the structure at Bi3+ positions. The catalyst materials at the Ni doping ratios all have the monoclinic-scheelite BiVO4 structure as shown by the XRD and Raman methods. The photocatalytic ability of methyl blue (MB) on the Ni/BiVO4 catalyst was studied under visible light irradiation in order to contribute to reducing the current environmental pollution problem. The removal efficiency of MB varies with the doping ratio of Ni/BiVO4, reaching the highest decomposition efficiency of 84.77% in the 5% mol Ni sample, which is 30% higher than that of the BiVO4 sample. The BiVO4 material modified with Ni gives a high photocatalytic efficiency of organic pigment decomposition under visible light indicates the potential improvement in the efficiency of a material for existing applications and exploit many new applications in the future.

Mössbauer and magnetic studies of Fe-doped ZnO nanoparticles prepared by solution co-precipitation method

A series of Zn[Formula: see text]FexO ([Formula: see text], 0.015, 0.045, 0.075) nanoparticles were synthesized using the solution co-precipitation method, and their structural and property characteristics were investigated. X-ray diffraction (XRD) analysis revealed that all Zn[Formula: see text]FexO samples exhibited a hexagonal wurtzite crystal structure with the P63mc space group. The introduction of Fe doping led to a slight lattice distortion in the samples. The morphology of the nanoparticles, including polydispersion and agglomeration, as well as the presence of the second phase ZnFe2O4, was examined by scanning electron microscope (SEM) and transmission electron microscope (TEM). UV–Vis diffuse reflectance spectroscopy demonstrated that the band gap of Zn[Formula: see text]FexO lies between 3.152 and 3.163[Formula: see text]eV. With the increase in Fe ion doping, the band gap shows a slight decreasing trend. Mössbauer spectroscopy revealed that iron ions in the nanoparticles existed in a trivalent state and exhibited two different configurations: One involved iron replacing zinc without creating a vacancy, while the other involved iron substituting zinc with a vacancy. The ferromagnetic nature of the Fe-doped samples can be attributed to the exchange interaction between two Fe[Formula: see text] ions mediated by the F-center mechanism.

Enhanced Photo/Electrocatalytic Hydrogen Evolution by Hydrothermally Derived Cu-Doped TiO2 Solid Solution Nanostructures.

Highly efficient nanocatalysts with a high specific surface area were successfully synthesized by a cost-effective and environmentally friendly hydrothermal method. Structural and elemental purity, size, morphology, specific surface area, and band gap of pristine and 1 to 5% Cu-doped TiO2 nanoparticles were characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), energy dispersive X-ray analysis (EDAX), inductively coupled plasma mass spectrometry (ICP-MS), liquid chromatography-high resolution mass spectrometry (LC-HRMS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area, Raman spectroscopy, photoluminescence spectroscopy (PL) and UV-visible diffused reflectance spectroscopy (UV-DRS) studies. The XPS and EPR findings indicated the successful integration of Cu ions into the TiO2 lattice. UV-DRS and BET surface area investigations revealed that with an increase in dopant concentration, Cu-doped TiO2 NPs show a decrease in band gap (3.19-3.08 eV) and an increase in specific surface area (169.9-188.2 m2/g). Among all compositions, 2.5% Cu-doped TiO2 has shown significant H2 evolution with an apparent quantum yield of 17.67%. Furthermore, the electrochemical water-splitting study shows that 5% Cu-doped TiO2 NPs have superiority over pristine TiO2 for H2 evolution reaction. It was thus revealed that the band gap tuning with the desired dopant concentration led to enhanced photo/electrocatalytic sustainable energy applications.

Graphene oxide-induced CuO reduction in TiO2/CaTiO3/Cu2O/Cu composites for photocatalytic degradation of drugs via peroxymonosulfate activation

Contamination of water bodies is a global environmental and human health issue. Conventional water treatment systems cannot efficiently eliminate organic contaminants, particularly drugs. Photocatalysis is a promising, environmentally friendly oxidation process for the removal of such compounds. A key point is the choice of material to be used as photocatalyst. Here, TiO2/CaTiO3/Cu2O/Cu composites were fabricated by adding different amounts (x) of graphene oxide (GO) (x wt% = 1, 3, and 5 %) to CaCu3Ti4O12 powder using the solid-state synthesis method. The produced pellets were sintered under inert nitrogen atmosphere at 1100 °C for 3 h. X-ray diffraction analysis showed that the Cu metal amount was increased upon GO addition, and the UV–Vis diffuse reflectance spectroscopy showed that the spectral response was extended to the visible range. Then, high performance liquid chromatography assessment of paracetamol degradation by a photocatalytic cell using TiO2/CaTiO3/Cu2O/Cu composites with different GO amounts showed that the removal efficiency was increased upon introduction of 0.5 mM peroxymonosulfate (PMS) as active component to generate SO4‾ radicals. After 3 h under visible light, 96 % of 10 ppm paracetamol was degraded by the composite with 3 % of GO (1 cm2 surface photocatalyst) compared with 50 % by the composite without GO in the same experimental conditions (PMS in 210 mL of aqueous solution). Free radical trapping and the acute toxicity of potential degradation by-products were also investigated. Our results indicate that TiO2/CaTiO3/Cu2O/Cu with 3 % GO displays long-term stability and durability for the photocatalytic removal of pharmaceutical pollutants from wastewater.

Controlling cisplatin release by synergistic action of silver-cisplatin on monodispersed spherical silica for targeted anticancer and antibacterial activities

Recently, metal-based nanoformulations have been explored for targeted cancer therapeutics. In this study, synergistic therapeutic action of silver (Ag)-cisplatin nanoparticles loaded on monodispersed spherical silica (MSS) was investigated to evaluate anti-cancer (HCT-116 and HeLa cells) and antibacterial activity (P.aeruginosa, and S.aureus). Four different wt% of Ag (1, 2, 4 and 6 wt%) was loaded on MSS using a wet impregnation method. Characterization using XRD revealed the cubic phase of Ag nanoparticles with (111), (200) and (220) plane on MSS. The chemical state, dispersion of Ag and synergistic cohabitation with cisplatin (Cpt) was identified using diffuse reflectance UV–visible spectroscopy (DR-UV Vis), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM-EDS) and High-resolution transmission electron microscopy (HR-TEM). Zeta potential analysis indicated an increase in hydrodynamic diameter with high colloidal stability (–23.3 to −28.5 mV). The percentage cumulative Cpt release was studied using automated Franz cell and dialysis membrane technique. The effect of Cpt release on 4 wt%Ag impregnated on different shaped supports was investigated using cubic SBA-16 (Santa Barbara Amorphous), MFI type Ti-ZSM-5 (Zeolite Socony Mobil #5), hexagonal mesosilicalite, nanotube halloysite, and Ag-silicalite, respectively. Drug release study indicates that Ag loading controls the Cpt release. The kinetics of drug release for the different formulations was examined using Korsmeyers-Peppas model. Release constant (k) and release exponent (n) were utilized for the rate of drug release and diffusion mechanisms, respectively. The in vitro study revealed an efficient interaction of nanoformulations promoting both antibacterial and anticancer activities.

Highly efficient magnetically separable SrFe12O19 for photo-assisted oxidation of benzylic alcohol derivatives under visible light

The selective oxidation of the Cα−OH group of benzylic alcohols is a crucial process for the conversion of lignin into useful products. In this study, we describe the synthesis and characterization of magnetic strontium hexaferrite, SrFe12O19. The SrFe12O19 nano-powder was produced through coprecipitation at a pH level of 10. The catalyst has been studied using various methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray analysis (EDX), UV–vis diffuse reflectance spectroscopy (DRS), and magnetic field dependence measurements. The study aimed to evaluate the photocatalytic performance of SrFe12O19 in selective oxidation of benzylic alcohols and degradation of methylene blue under visible light. Additionally, the magnetic properties of the catalyst were also investigated. Magnetic properties were also investigated. M-SrFe12O19 with a band near 2 eV, showed excellent photocatalytic degradation performance at ca. 90% of MB under visible light. The photocatalytic degradation activity was evaluated for three cycles, and the results demonstrate that it maintains its photodegradation potency, with significant photo-degradation conversion of 89%, 87%, and 84%. The experiment clearly demonstrated that the reaction kinetics followed a pseudo-first order. The oxidation of benzyl alcohol (BzOH) was successfully carried out over SrFe12O19 in the presence of hydrogen peroxide, a highly effective green oxidant, under visible light. Notably, the experiment results showed a maximum conversion of BzOH, reaching approximately 70%, with absolute selectivity towards benzaldehyde (BzCHO). Furthermore, the yield of aldehyde increases according to the Hammett constant, with the highest yield being obtained for 2-hydroxybenzaldehyde (σ = −0.37). The synthesized M-SrFe12O19 material shows potential as an eco-friendly method for lignin valorization.

Photocatalytic degradation of norfloxacin antibiotics on ZnxCd(1-x)S/g-C3N4 composites in water.

g-C3N4/ZnxCd(1-x)S composites were synthesized by a simple hydrothermal method. The composites were characterized by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, infrared spectroscopy, and electron micro-projective microscopy. According to the performance of ZnxCd(1-x)S for the photocatalytic degradation of norfloxacin under visible light in water, the best stoichiometric number of x was 0.5. The best photolytic norfloxacin degradation rate of g-C3N4/ZnxCd(1-x)S composites was 89.8%, which was obtained when the dosage ratio of g-C3N4 to ZnxCd(1-x)S was 1:1. The experiment was conducted to investigate the effect of pH on the catalyst to obtain the optimal NORF degradation environment pH in the range of 7 ± 0.3; by simulating the anions that may be contained in the actual environmental water, the results showed that the catalyst has a certain effect on the degradation of NORF when the water contains NO3-, Cl- and HCO3-. In addition, this study also obtained that the main active substances produced by the catalyst during degradation were electron-hole pairs by adding different trapping agents in the NORF removal experiments; and the catalyst was able to achieve a degradation rate of 86.1% after four cycles of the experiments, which proved that it had good stability.

Keto-Adamantane-Based Macrocycle Crystalline Supramolecular Assemblies Showing Selective Vapochromism to Tetrahydrofuran

Here, we report the synthesis of adamantane-based macrocycle 2 by combining adamantane building blocks with π-donor 1,3-dimethoxy-benzene units. An unpredictable keto-adamantane-based macrocycle 3 was obtained by the oxidation of 2 using DDQ as an oxidant. Moreover, a new type of macrocyclic molecule-based CT cocrystal was prepared through exo-wall CT interactions between 3 and DDQ. The cocrystal material showed selective vapochromism behavior towards THF, specifically, among nine volatile organic solvents commonly used in the laboratory. Powder X-ray diffraction; UV-Vis diffuse reflectance spectroscopy; 1H NMR; and single crystal X-ray diffraction analyses revealed that color changes are attributed to the vapor-triggered decomplexation of cocrystals.

Green synthesis, characterisation, and performance evaluation of ZnO/TiO2 nanocomposite for cationic and anionic dye removal from aqueous solutions under solar irradiation

Abstract Utilising plant extract for the synthesis of nanocomposite shows great potential as a viable substitute for conventional chemical method. In this study, ZnO/TiO2 composite of three different weight ratios (1:2, 1:1, and 2:1) were green synthesised using hibiscus leaf extract as the capping agent. The synthesised composites were characterised using X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), UV–Vis Diffuse Reflectance Spectroscopy (UV–Vis DRS), Energy Dispersive X-ray Spectrometer (EDS), and Fourier Transform Infrared Spectroscopy (FTIR). XRD results confirmed the presence of wurtzite ZnO and anatase TiO2 in the composite. FTIR and FESEM analysis confirmed the formation of the composite. The composite was used for the removal of methylene blue and methyl orange dye under solar radiation. The degradation rate constant (k) of the composite with 1:2 weight ratio was 1.9 times the k value of pure TiO2. The effect of photocatalyst amount, initial pH of the dye solution, and reusability of the catalyst was investigated. The TiO2 and ZnO/TiO2 samples indicated a bandgap of 3.14 and 2.98 eV, respectively, which suggests better photocatalytic activity and also making the composite more active in the visible region.

Synthesis of Ag/ZnO/BiOCl Composite Material and Its Photodegradation Performance on Ciprofloxacin

This study focuses on synthesizing a composite material of Ag/ZnO/BiOCl using Ag, ZnO, and BiOCl as raw materials. The material was prepared by loading Ag and BiOCl onto ZnO nanofilms, aiming to enhance the photocatalytic degradation of ciprofloxacin (CIP). Optimization of the photocatalytic degradation process through single-factor experiments revealed that under conditions of an initial CIP pH of 9, an Ag/ZnO/BiOCl dosage of 1 g/L, and an initial CIP concentration of 5 mg/L the conversion efficiency of CIP reached 98.79% after 150 min of exposure to a 250 W xenon lamp simulating sunlight. Furthermore, the composite material maintained a conversion efficiency of 86.17% for CIP even after five cycles of reuse, demonstrating its excellent stability. The optical properties, elemental composition, valence state, crystallinity, and morphology of the samples were analyzed using techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), UV–visible diffuse reflectance spectroscopy (UV-vis DRS), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results indicate that the introduction of Ag expanded the light response range of ZnO, while the addition of BiOCl improved the separation efficiency of electron–hole pairs in the composite nanomaterial. The photocatalytic mechanism was further elucidated through radical scavenging experiments, confirming that ·OH and h+ are the main active species in the degradation process.

Sonochemically Synthesized Bismuth Oxyiodide Nanocrystal for Wastewater Remediation through Visible‐Light Photocatalysis

AbstractIt has been demonstrated that bismuth oxyhalides [BiOX (X = Cl, Br, and I)] nano‐crystals can efficiently behave as photocatalysts both under visible light and UV light. Different types of dyes, phenols, etc. can be degraded by bismuth oxyhalides materials efficiently, for the purification of wastewater. The raw materials used in the synthesis of bismuth oxyiodide (BiOI) are pure Bi2O3, halide salt, and capping agent (poly‐vinyl‐pyrrolidone). A variety of characterization techniques are used to characterize the as‐synthesized samples, including X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–Vis diffuse reflection spectroscopy (UV–Vis DRS), photoluminescence (PL), Mott–Schottky, field emission scanning electron microscopy (FESEM), energy dispersive X‐ray spectroscopy (EDX), and high resolution transmission electron microscopic (HRTEM), etc. A potential application in environmental remediation is achieved through 95.25% degradation of organic Rhodamine B (RhB) dye within 100 min using the synthesized materials under visible light irradiation.

Synthesis, crystal structure, thermal stability, and photovoltaic properties of organic-inorganic hybridized copper-based perovskite single crystals modulated by organics

Organic-inorganic hybridized perovskite have excellent photovoltaic properties, especially Pb-based organic-inorganic perovskite polycrystalline thin films based on Pb-based organic-inorganic perovskite have achieved high power conversion efficiency, but the polycrystalline materials have a large number of grain boundaries and defects, which are susceptible to the influence of water and oxygen, leading to structural degradation, poor stability, high toxicity and slow degradation, which are not friendly to the environment. Therefore, in this paper, two copper-based organic-inorganic hybrid perovskite single crystals (C6H9N2)2CuCl4 and (C6H18N2)2Cu2Cl8 were synthesized by using the method of organic modulation, and were investigated by single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, thermogravimetric analysis, and UV–vis diffuse reflectance spectroscopy. The samples were analyzed in detail for crystal structure, chemical groups, bond characterization, optical and thermal stability. The results show that (C6H9N2)2CuCl4 and (C6H18N2)2Cu2Cl8 single crystals belong to the C2/c space group of the monoclinic crystal system and the P-1 space group of the triclinic crystal system, respectively. The optical band gap of (C6H9N2)2CuCl4 is 2.45 eV, which is stable up to 179 °C, and that of (C6H18N2)2Cu2Cl8 is 2.47 eV, which is stable up to 163 °C. The thermal stability of the crystals can be regulated by changing the organic cation in the A-site, but the optical band gap of the crystals cannot be regulated significantly.

Graphite/carbon-doped TiO2 nanocomposite synthesized by ultrasound for the degradation of diclofenac.

Graphite/C-doped TiO2 nanocomposite was synthesized at room temperature using a simple, impressive, and indirect sonication (20kHz) by the cup horn system. Tetrabutyltitanate as the precursor of titanium and graphite (G) as the carbon source was used in the preparation of nanocomposite as a photocatalyst. The molar ratio of G/TiO2 as a key parameter was investigated in the synthesis of G/C-doped TiO2. The obtained materials were widely characterized using XRD, SEM, TEM, FTIR, XPS, and UV-Vis diffuse reflectance techniques. The UV-Vis diffuse reflectance spectroscopy results showed that the edge of light absorption of nanocomposite was distinctly red-shifted to the visible area via carbon doping. The XPS outcomes acknowledged the existence of the C, Ti, and O in the photocatalyst. The composite showed an enhancement in the dissociation efficiency of photoinduced charge carriers through the doping process. The photocatalytic activity of the synthesized nanocomposite was checked with diclofenac (DCF) as a pharmaceutical contaminant. The results displayed that G/C-doped TiO2 represented better photocatalytic performance for DCF than TiO2. This was due to the excellent crystallization, intense absorption of visible light, and the impressive separation of photoinduced charge carriers. Various active species such as •OH, •O2¯, h+, and H2O2 play a role in the degradation of DFC. Therefore, different scavengers were used and the role of each one in degradation was investigated. According to the obtained results, •O2¯ radical showed a major role in the photocatalytic process. This work not only proposes a deep insight into the photosensitization-like mechanism by using G-based materials but also develops new photocatalysts for the removal of emerging organic pollutants from waters using sunlight as available cheap energy.

Influence of visible light LEDs modulation techniques on photocatalytic degradation of ceftriaxone in a flat plate reactor

In this paper, the effect of light modulation on photocatalytic ceftriaxone (CEF) degradation in aqueous solution was investigated. The experimental set-up consisted of a fixed bed photocatalytic reactor with a flat plate geometry and visible LEDs for irradiation. Fe-N-codoped TiO2 photocatalyst was immobilized on a polystyrene plate (PS) by solvent casting method to achieve a structured photocatalyst (Fe-N-TiO2/PS), which was loaded in the photoreactor. Raman and UV–Vis diffuse reflectance spectroscopy confirmed the presence of Fe-N-TiO2 on the PS surface and its uniform distribution on the polymer support. Various LEDs dimming techniques were tested with fixed and variable duty-cycle values. In particular, the following modulations were used: fixed duty-cycle (FD), sinusoidal variable duty-cycle (S-VD), triangular variable duty-cycle (T-VD), square wave variable duty-cycle (SW-VD), saw-tooth variable duty-cycle (ST-VD), pulse variable duty-cycle (P-VD), and pseudo-sinusoidal variable duty-cycle (PS-VD). The optimal light modulation was the S-VD, with an average fed current between 25 and 75 mA and a period of 30 s. Indeed, by using S-VD modulation, the highest value of the apparent CEF degradation kinetic constant (resulting 0.0082 min−1) and the highest total organic carbon (TOC) removal (70 %) were achieved. By comparing the electric energy consumption (EE/O) with S-VD modulation used in this work with those found in other literature studies dealing with the photocatalytic ceftriaxone degradation, a significant decrease of EE/O was evidenced. Moreover, toxicity test showed that the photocatalytic treatment allowed to significantly reduce the toxicity of CEF solution when compared to untreated effluent.

Thermotropic Structure Phase Transitions and Two Types of Thermochromic Behaviors in a Bromoargentate Cluster [Pr-dabco]2Ag4Br6.

Organic-inorganic silver halide hybrids show abundant phase transitions and thermochromism. However, it is very rare that silver halides exhibit thermochromism related to thermotropic structure phase transition. Herein, a bromoargentate hybrid, [Pr-dabco]2Ag4Br6 (1) (Pr-dabco+ = 1-propyl-1,4-diazabicyclo-[2.2.2]octan-1-ium), with tetranuclear [Ag4Br6]2- clusters was prepared and characterized by microanalysis, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, and thermogravimetric (TG) and differential scanning calorimetry (DSC) techniques. Interestingly, 1 undergoes an irreversible structure phase transition at ∼436 K in the first heating process, which is accompanied by an abrupt color change from colorless to yellow; however, a reversible color change between pale yellow and yellow is observed in the next heating-cooling cycles. Notably, DSC measurement revealed that a reversible phase transition is associated with the change in color between pale yellow and yellow, while the powder X-ray diffraction (PXRD) patterns corresponding to pale yellow and yellow phases are quite similar to each other. These observations demonstrate that thermochromism in the next heating-cooling runs is associated with a reversible structure phase transition, which perhaps concerns the disorder-order transformation of alkyl chains in the cationic ligand [Pr-dabco]+, and relevant to the anharmonic fluctuations of the Ag-Br and Ag-N bonds, a strong electron-phonon coupling effect is seen within the bromoargentate cluster.