UV Vis Diffuse Reflectance Spectroscopy Research Articles

Photocatalytic oxidation of benzyl alcohol coupled with p-dinitrobenzene reduction over poly(o-phenylenediamine) nanowires-decorated Gd-TiO2 nanorods

Simultaneous oxidation of benzyl alcohol (BA) and reduction of p-dinitrobenzene (p-DNB) over Gd-doped TiO2nanorods decorated with poly(o-phenylenediamine, PoPD) nanowires was reported in this work. The doping of TiO2 with Gd induced surface defects, i.e., oxygen vacancy (OV) and the Ti3+–on-Ti4+site, while incorporating PoPD highly enhanced the light absorption capability and electron conductivity of TiO2nanorods,as confirmed by UV–vis diffuse reflectance spectroscopy (DRS) and electrochemical measurements, respectively. BA was selectively oxidized by photogenerated h+to form benzaldehyde with a yield of 70.5% in water and 90.6% in acetonitrile solvent. Conversely, p-DNB was selectively reduced to p-nitroaniline (p-NA) with a yield of 89.1% in acetonitrile and to p-phenylenediamine (p-PDA) of 85.0% yield in water. This work demonstrates a vital strategy to utilize the full economic potential of photogenerated charge carriers and the decisive role of solvent for product selectivity in the course of selective organic transformations.

Study on the photoelectrocatalytic activity of reduced TiO2 nanotube films for removal of methyl orange

Abstract The reduced TiO2 film on which a photoelectrocatalytic (PEC) process had occurred was created from TiO2 nanotube film electrodes by the electrochemical reduction method. The obtained samples’ structure and morphology were characterized using UV-Vis diffuse reflectance spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, photoluminescence, and X-ray diffraction. Cyclic voltammetry, linear sweep voltammetry, electrochemical impedance spectroscopy, chronoamperometry, UV-Vis absorbance spectroscopy, and Mott–Schottky plots were employed to examine the electrochemical and photoelectrochemical activities of the prepared electrodes. The results showed that the optimal conditions of cathodic polarization were a potential of −1.4 V for 60 min. The reduced TiO2 nanotube film electrode had better photoelectrochemical activities than pristine TiO2 under UV light due to the higher photocurrent density (13.7 mA‧cm−2) at 1.5 V (vs Ag/AgCl, sat. KCl reference electrode) compared to pristine TiO2 achieving 7.3 mA‧cm−2, indicating more effective charge separation and transport. The degradation of methyl orange (MO) on pristine TiO2 and reduced TiO2 electrodes was carried out in electrocatalytic (EC) and PEC conditions. The PEC process on the reduced TiO2 electrode had the highest MO processing efficiency (98.4%), and the EC process for MO removal on reduced TiO2 had higher efficiency (95.1%) than the PEC process on pristine TiO2 (89.2%).

Boosting photocatalytic dehydrogenation and simultaneous selective oxidation of benzyl alcohol to benzaldehyde over flower-like MoS2 modified Zn0.5Cd0.5S solid solution

A series of MoS2/Zn0.5Cd0.5S with varying concentrations of flower-like MoS2 is prepared based on a simple and practical method with highly efficient photocatalytic dehydrogenation and simultaneous selective oxidation of benzyl alcohol (BA) to benzaldehyde (BAD). A comparative study between the composites and their two components (pristine MoS2 and Zn0.5Cd0.5S) is carried out for various structural, optical, electrical, and photocatalytic characterization. The studies reveal that the size of Zn0.5Cd0.5S nanoparticles is in the order of 3∼5 nm and is distributed uniformly over the surface of the flower-like 350 nm sized MoS2. The optical research conducted using UV–vis diffuse reflectance spectroscopy reflecting an excellent photoresponse by the MoS2/Zn0.5Cd0.5S. The photoelectrochemical tests showed that the adding of proper ratio of flower-like MoS2 (6%) results in an efficient separation and migration of photogenerated carriers for pristine Zn0.5Cd0.5S nanoparticles. The photocatalytic dehydrogenation rate of BA for the 6%-MoS2/Zn0.5Cd0.5S is the highest at 3.03 mmol g−1 h−1, meanwhile the yield of BAD and the selective conversion of BA to BAD are 49.3% and 100%, respectively. The essential stages of the photocatalytic dehydrogenation of BA are ·C caused by the photo-generated holes, according to the EPR spectra of the PBN-carbon centered radical (PBN–C). Besides, the mechanism for improved photocatalytic dehydrogenation and synergistic selective oxidation of BA to BAD with flower-like MoS2 modified Zn0.5Cd0.5S nanoparticles was systematically studied through gas chromatography-mass spectrometry analysis and first principle density functional theory calculations. The highly efficient dehydrogenation and synergistic selective oxidation of BA to BAD for MoS2/Zn0.5Cd0.5S are mainly attributed to the introduction of MoS2 nanoflowers that can provide abundant active sites, and formed MoS2/Zn0.5Cd0.5S heterostructures could further promote the separation of photogenerated electron-hole pairs. Moreover, the valance band position of the 6%-MoS2/Zn0.5Cd0.5S is more positive, so the hole at the VB position has the stronger ability to oxidize BA. This study provides a feasible method for efficiently photocatalytic dehydrogenation synergism selective oxidation of organic substrates into valuable products.

Silica-magnesium-titanium Ziegler-Natta catalysts. Part 1: Structure of the pre-catalyst at a molecular level

In this paper, which is the first part of a more extended work, we elucidate the molecular level structure of a highly active SiO2-supported Ziegler-Natta precatalyst obtained by reacting a dehydroxylated silica and a solution of an organomagnesium compound with TiCl4. The synergetic combination of Ti K-edge and Ti L3-edge X-ray Absorption spectroscopy (XAS) and diffuse reflectance UV–Vis spectroscopies, complemented by Density Functional Theory (DFT) simulations, indicate that small TiCl3 clusters similar to β-TiCl3 coexist with isolated monomeric Ti(IV) species. Ti K-edge Extended X-ray Absorption Fine Structure (EXAFS) Spectroscopy allows the quantification of these two phases and demonstrates that the Ti(IV) sites are 6-fold coordinated (either by six chlorine ligands or by five chlorine and one oxygen ligands), but highly distorted, similar to what is modelled for TiCl4-capped MgCl2 nanoplatelets. Finally, IR spectroscopy suggests that the MgCl2 phase has a molecular character (Far-IR) and that the only accessible Mg2+ sites are uncoordinated cations acting as Lewis acid sites (IR of CO adsorbed at 100 K). Based on these experimental findings, we propose the co-existence in the precatalyst of small TiCl3 clusters and of mixed oxo-chloride magnesium-titanium structures deposited at the silica surface. The evolution of the precatalyst in the presence of the activator and of the monomer is discussed in the second part of this work.

Influence of non-magnetic ions doping on structural, morphological, optical, and magnetic properties of nanocrystalline zinc oxide powders

In this research study, nanocrystalline non-magnetic ion-doped zinc oxide powders are synthesized through sol-gel auto combustion with a variety of different ions (Mg, Al, and Ca) at a range of concentrations (0, 5%, 10%, 20% mol). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), filed-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), UV–visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL), and vibrating sample magnetometry (VSM) were then used to investigate the calcined products, whereupon the structures, chemical bonds, surface texture, chemical composition, morphologies, particle size, surface elemental composition, electronic state, optical and fluorescence properties including magnetism were reported for each of the samples. From XRD it could be determined that the introduction of minuscule quantities of magnesium and calcium ions to the zinc oxide powder produced solutions of hexagonal solid MgZnO and CaZnO, while composites of Mg/ZnO, CaO/ZnO, Al2O3/ZnO could also be observed, without impurity phases. Textural properties of these modified samples observed from SEM, FE-SEM, and TEM were superior to that of the pure ZnO. XPS studies confirmed the substitution of Zn2+ by Mg2+ and Ca2+ for the samples of low doping concentration. UV-DRS analysis showed that samples which had been optimally modified exhibited improved levels of absorption when compared to visible spectral observations of the pure sample. In comparison to the pure sample, the modified samples also showed higher bandgap energy (Eg). In the pure sample, violet and blue emission bands were seen in the PL spectra ranging from 350 to 430 nm, but these emissions showed significant changes in intensity as the concentration of non-magnetic ions was increased. Furthermore, VSM results revealed that diamagnetism of zinc oxide can be adjusted through the introduction of non-magnetic ions to paramagnetism and ferromagnetism.

Visible light responsive MWCNT decorated g-C3N4/Bi2S3 photocatalyst for malachite green dye degradation

A highly efficient ternary nanocomposite consisting of multiwalled carbon nanotubes (MWCNTs), graphitic carbon nitride (g-C3N4), and bismuth sulfide (Bi2S3) is developed via a simple one-step hydrothermal route. The structural, morphological, and optical properties of the developed nanocomposites are systematically analyzed using x-ray diffraction, x-ray photoelectron spectroscopy, electron microscopy, UV–vis diffuse reflectance spectroscopy, and Brunauer, Emmett, and Teller analysis. The ternary nanocomposite g-C3N4/Bi2S3/MWCNT-6 wt. % exhibits two times higher photocatalytic performance (99.6%) than g-C3N4/Bi2S3 and g-C3N4/MWCNT binary heterostructures under visible light irradiation within 50 min. The enhanced photocatalytic activity is attributed to the strong absorption of visible light and enhanced charge carriers separation efficiency, high surface area, and synergistic effect of g-C3N4, Bi2S3, and MWCNTs. A reaction mechanism for enhanced photocatalytic performance has also been proposed. The effect of different scavengers is performed to determine the role of the main reactive species responsible for dye degradation, which reveals that electrons are the main reactive species responsible for dye degradation. Moreover, the g-C3N4/Bi2S3/MWCNT ternary photocatalyst maintained excellent stability even after several cycles. Thus, the study offers a promising, stable, highly efficient, and visible-light-driven photocatalyst for dye wastewater purification.

Synthesis of ZnO Crystal with Micro‐Nano Structures by a Continuous Co‐Precipitation Method: Morphological Evolution and Mechanism Analysis

AbstractZnO crystals are employed in numerous industries, but precisely controlling their morphologies is still challenging. In this work, a continuous flow process for synthesizing ZnO crystals is developed based on the co‐precipitation method. ZnO crystals at different morphologies, including needle‐like, rod‐like, flower‐like, spindle‐like, and nanospheres, are successfully prepared at low temperature. The influence of reaction temperature, pH value, ZnCl2 feeding concentration, and reaction time on the morphology, size, and purity of ZnO crystals is systematically investigated. The results of X‐ray diffraction show that the high‐purity ZnO can only be produced when the reaction temperature is above 75 °C. The band gap energies of ZnO evaluated by UV–vis diffuse reflectance spectroscopy increase with the synthesis temperature. According to scanning electron microscope (SEM) findings, the size of ZnO crystals is regulated by controlling the reaction time. Interestingly, the morphology of ZnO crystals is changed from 1D to 3D structure by controlling the feeding concentration of ZnCl2. Moreover, a concentration difference mechanism of ZnO crystal morphology evolution is proposed by monitoring the real‐time concentration of free Zn2+ ions.

Evaluation of Photocatalytic Activity and Electrochemical Properties of Hematite Nanoparticles

The symmetric nano morphologies, asymmetric electronic structures, and as well as the heterojunctions of the developed photocatalytic systems perform a vital role in promoting light absorption, separation of electron and hole pairs and charge carrier transport to the surface when exposed to near-infrared (NIR) light. In this present work, we synthesized hematite (α-Fe2O3) nanoparticles (NPs) by a facile hydrothermal method and studied their structural, optical, and photocatalytic properties. Powder X-ray diffraction (XRD) confirmed the rhombohedral phase of the α-Fe2O3 NPs, and Fourier transform infrared spectroscopy (FT-IR) was used to investigate symmetric and asymmetric stretching vibrations of the functional groups on the surface of the catalysts. The optical bandgap energy was estimated to be 2.25 eV using UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and scanning electron microscopy (SEM) images indicated sphere like morphology. The oxidation and reduction properties of α-Fe2O3 NPs were analyzed by cyclic voltammetry (CV). The α-Fe2O3 NPs were utilized for the degradation of methylene blue (MB) dye under natural sunlight. The experimental results demonstrate that the degradation efficiency was achieved at 33% in 2 h, and the pseudo-first-order rate constant was calculated to be 0.0033 min−1.

Repeated photocatalytic inactivation of E. coli by UV + Ni foam@TiO2: Performance and photocatalyst deactivation

Photocatalysis (PC) has exhibited a bright prospect in the inactivation of waterborne pathogens. However, the deactivation of photocatalysts during PC bacterial inactivation has not been systematically studied so far. In this study, we investigated the performance of a PC system nickel foam-loaded TiO2 (NF@TiO2) during a 70-cycle of bacterial inactivation focusing on the photocatalyst deactivation mechanism, where E. coli DH5α was employed as the model photocatalyst and bacteria, respectively. Our results showed that the UV + NF@TiO2 process could effectively inactivate E. coli. Approximately 1 × 108 cfu mL−1 of E. coli could be completely inactivated within 4 h using a fresh NF@TiO2 photocatalyst. However, the inactivation efficiency substantially declined with the increase in cycle number, and NF@TiO2 was almost poisoned after 70 cycles. Through the characterization of scanning electron microscope, atomic force microscope, UV–vis diffuse reflectance spectroscopy, and electron paramagnetic resonance, as well as other experiments, a deactivation mechanism of NF@TiO2 was proposed: The PC-generated reactive oxygen species (ROS) fragmented E. coli to excrete a myriad of biomolecules that subsequently adhered to the surface of NF@TiO2. This accelerated the deterioration of PC inactivation by impeding light harvest and reactive species utilization. Moreover, biomolecules were found to play a pivotal role in photocatalyst deactivation, following the order of lipopolysaccharide ≈ DNA > proteins. This study could provide a fundamental view of the deactivation of photocatalysts during bacterial inactivation.

Visible light driven CZTS QDs/α-Fe2O3-graphene p–n heterojunction for photoelectrochemical water splitting

This work investigates the implication of graphene and Cu2ZnSnS4 (CZTS) quantum dots (QDs) incorporation in the hematite thin film for its use in a photoelectrochemical cell. The thin film has been prepared by decorating the CZTS QDs over graphene-hematite composite by simple chemical approach. In Comparison to graphene modification and CZTS QDs modification separately over hematite thin film, the combination of both has produced more photocurrent. The photocurrent density obtained for CZTS QDs and graphene modified hematite thin film is 1.82 mA cm−2 at 1.23 V/RHE, which is 1.75 higher than pristine hematite. The presence of CZTS QDs over hematite-graphene composite enhances the absorption properties of composite along with creating the p–n junction heterostructure which aids the transportation of the charge carriers. The thin films have been characterized using x-ray diffractometer, Raman spectroscopy, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy, and diffuse reflectance UV–vis spectroscopy for phase, morphology and optical properties analysis. The enhancement in photoresponse has been justified by Mott-Schottky and transient open circuit potential analysis.

Gamma Radiation Synthesis of Ag/P25 Nanocomposites for Efficient Photocatalytic Degradation of Organic Contaminant.

Titanium dioxide (TiO2) has garnered significant attention among various photocatalysts, whereas its photocatalytic activity is limited by its wide bandgap and inefficient charge separation, making the exploration of new strategies to improve its photocatalytic performance increasingly important. Here, we report the synthesis of Ag/P25 nanocomposites through a one-step gamma-ray radiation method using AgNO3 and commercial TiO2 (Degussa P25). The resulting products were characterized by powder X-ray diffraction, UV-Vis diffused reflectance spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The effect of free radical scavengers, feed ratios of Ag/P25, and dose rates on the photocatalytic activity of the Ag/P25 nanocomposites were systematically investigated using rhodamine B under Xenon light irradiation. The results showed that the Ag/P25 photocatalyst synthesized with a feed ratio of 2.5 wt% and isopropyl alcohol as the free radical scavenger at a dose rate of 130 Gy/min exhibited outstanding photocatalytic activity, with a reaction rate constant of 0.0674 min-1, much higher than that of P25. Additionally, we found that the particle size of Ag could be effectively controlled by changing the dose rate, and the Ag/P25 nanocomposites doped with smaller size of Ag nanoparticles performed higher photocatalytic activities. The synthesis strategy presented in this study offers new insight into the future development of highly efficient photocatalysts using radiation techniques.

One-step electrodeposition of Co-Fe electrocatalysts with micro/nano-cauliflower like structure for highly efficient oxygen evolution reaction (OER)

In this study, Co-Fe coatings with different “Fe” contents were produced as catalysts for oxygen evolution reaction (OER) by a one-step electrodeposition method using 0–6 g/L FeSO4 in an electrolytic bath. The structure, electrochemical and electrical properties of the produced catalysts were carefully investigated. Scanning electron microscopy (SEM) results showed that the morphology of the prepared catalysts was varied with the “Fe” content. UV–vis diffuse reflectance spectroscopy (DRS) results along with Tauc plots indicated that the concentration of oxygen vacancy decreased by increasing the Fe content from 2 to 6 g/L, while the Co-Fe (2 g/L) catalyst with a band gap of 1.35 eV had the maximum concentrations of oxygen vacancies. Also, linear sweep voltammetry (LSV) results demonstrated that the Co-Fe (2 g/L) catalyst had the lowest overpotential (136 mV) at a current density of 10 mA.cm−2 and a small Tafel slope of 24.3 mV.dec− 1. The results confirmed the formation of the CoFe2O4 phase in the Co-Fe (2 g/L) catalysts. It was eventually concluded that the Co-Fe (2 g/L) catalyst with a nano-cauliflower like structure possesses the highest OER activity in 1 M KOH solution.

Dry reforming of methane using bimetallic Pt–Ni/Ti-SBA-15: Effect of Si/Ti ratio on catalytic activity and stability

A one-pot hydrothermal technique was used to make a series of Ti-incorporated mesoporous SBA-15 with varying Si/Ti ratios. The synthesized mesoporous materials were modified by introducing Ni (9%) as active metal and Pt (0.5%) as promoter using nickel nitrate and chloroplatinic acid, respectively, as metal precursors through incipient wetness impregnation method. All the catalysts and supports were characterized by X-ray diffraction, BET surface area, Fourier Transform–Infrared spectroscopy, UV–Visible diffuse reflectance spectroscopy, H2–temperature-programmed reduction, NH3–temperature-programmed desorption, transmission electron microscopy, and thermogravimetric analysis. The catalysts were subjected to dry reforming of methane using CH4/CO2 (molar feed ratio of 1:1) with a gas hourly space velocity (GHSV) of 36,000 mL. g−1. h−1 at a temperature range of 400–800 °C. The characterization results confirmed the incorporation of titanium ions in the SBA-15 matrix. However, Si/Ti loadings of 10 and 20 exhibited low extra-framework anatase phase titania levels, and high surface acidity. Among the subjected catalysts, Pt–Ni/Ti-SBA-15 (Si/Ti = 10) showed higher catalytic activity (CH4 = 84% and CO2 = 91%) with a H2/CO ratio of 3.6 after an 8 h reaction, and exhibited higher stability and coke tolerance than the bare catalysts and other modified Pt–Ni/Ti-SBA-15 catalysts. The characterization results of spent catalysts also confirmed low coke deposition on titanium-incorporated catalysts. The remarkable performance of the Pt–Ni/Ti-SBA-15 towards CH4 conversion and CO2 conversion may be related to strong metal–support interaction, presence of strong and weak acid sites, well-dispersed active metals and bi-metallic interaction.

Combining the bioelectricity generation with Photo-Electrocatalytic reduction of CO2 for pollutants degradation and ethanol generation

Under this investigation, a p-n heterojunction nanocomposite (CuS/MgFe2O4) was synthesized using a simplified hydrothermal technique. According to the results of UV–vis diffuse reflectance spectroscopy (DRS) research, the creation of a p-n heterojunction structure lowered the band-gap value and improved the optical characteristics of the synthesized CuS/MgFe2O4 nanocomposite in contrast to CuS and MgFe2O4 nanoparticles. To investigate the electrocatalytic and photo-electrocatalytic properties of nanoparticles in the CO2 reduction reaction, first, the synthesized catalysts were immobilized by the electrophoretic deposition method (EPD) on a graphite electrode, and then various electrochemical techniques such as cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were performed in the phosphate electrolyte (0.1 M, pH = 8) saturated with CO2 gas in the presence and absence of light. As a consequence, CuS/MgFe2O4/Graphite displayed a 2.2 and 1.3-fold increase in cathodic current density under light illumination compared to MgFe2O4/Graphite and CuS/Graphite, respectively. Using CuS/Graphite, MgFe2O4/Graphite, and CuS/MgFe2O4/Graphite as photocathodes in a two-chamber microbial fuel cell (MFC) caused a 13, 29, and 45 times increase, respectively, in the maximum power density compared to unmodified graphite. Gas chromatography-mass spectrometry (GC–MS) analysis revealed the presence of ethanol as the only detected CO2 conversion product, with a Faradic efficiency of about 35 %.

Photocathodic protection of 304 stainless steel by coating muscovite/TiO2 heterostructure

The sol-gel method was used to prepare a series of muscovite/TiO2 heterostructures for photocathodic protection of 304 stainless steels (304SS). The effects of different mass ratio of muscovite to TiO2 (1:0.5, 1:1 and 1:1.5, denoted as MT-0.5, MT-1 and MT-1.5, respectively) on the crystal phase, grain size, light absorption properties and photoelectrochemical properties of TiO2 and muscovite/TiO2 heterostructures were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–visible diffuse reflection spectroscopy (UV–vis DRS). The corrosion resistances and photoelectrochemical properties of the 304SS coated with muscovite/TiO2 heterostructures (304SS/MT) were studied through corrosion immersion test and electrochemical workstation in 3.5 wt% NaCl solution, respectively. In addition, Tafel curves and the electrochemical impedance spectroscopy (EIS) measurements were carried out to evaluate the photogenerated electron separation and transfer efficiency, and the interfacial charge transfer resistance of the 304SS and 304SS/MT electrodes, respectively. The time-dependent photocurrent responses of the MT-1 heterostructures demonstrated an enhanced photo-generated cathodic protection performance for 304SS substrates under visible light irradiation compared to TiO2. A photoinduced potential drop value for 304SS coated with MT-1 in 3.5 wt% NaCl solution was −0.54 V (vs. SCE). After immersion test, the corrosion image analyses of the 304SS, 304SS-MT, and 304SS coated with physically mixed muscovite/TiO2 samples showed that the 304SS/MT-1 exhibits the best corrosion resistances. After connecting with 304SS/MT-1 in 3.5 wt% NaCl solution, the corrosion current densities (icorr) of 304SS increased significantly under the white light illumination, indicating more photoinduced electrons were migrated from the muscovite/TiO2 heterostructures to the 304SS compared with that from pure TiO2. Furthermore, the simulated charge transfer resistance (Rct) of 304SS/MT-1 electrode is smaller than that of the 304SS electrode coated with TiO2, indicating that there exists an effective separation of the photogenerated electrons and holes, and a fast interfacial charge transfer after coating muscovite/TiO2 heterostructures.

Electrochemical treatment of electroplating wastewater using synthesized GO/TiO2 nanotube electrode.

The graphene oxide (GO) deposited TiO2 nanotube (GO/TiO2) electrode on a titania plate was prepared using a simple anodization method. The morphological and structural properties of TiO2 and GO/TiO2 electrodes have been studied using field emission scanning electron microscopy energy dispersive spectroscopy (FESEM-EDS), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Raman spectroscopy, Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectroscopy (XPS). FESEM-EDS analysis confirmed that the 13.56% wt of GO nanoparticles was formed over the TiO2 substrate, with the thickness of the wall to be ∼300nm. The crystallite size of GO/TiO2, i.e., 19.53nm, was confirmed by XRD analysis. Analysis of the UV-DRS spectrum showed the bandgap of the synthesized GO/TIO2 nanotube electrode to be 3.052eV. Box-Behnken design (BBD) under response surface methodology (RSM) was used to design the experiments. The effect of operating input parameters like pH, current (i), and degradation time (t) on % COD degradation (X1) and energy consumed (X2) were also examined. At optimum process parameters, the value of X1 and X2 were 57.61% and 15.00 kWh/m3, respectively. Possible intermediates were identified based on the GC-MS data analysis. Scavenger tests showed that •OH radical plays a major role in electroplating effluents degradation. Based on the results, the EO process using GO/TiO2 electrodes could be considered a promising technique for electroplating effluent degradation due to high degradation efficiency.

Lattice-charge imbalance and redox catalysis over perovskite-type ferrite- and manganite-based mixed oxides as studied by XRD, FTIR, UV–Vis DRS, and XPS

In the present investigation, two sets of pure and substituted ferrite- and manganite-based mixed oxides were prepared within the stoichiometric formulaA_{1 - x} A^{prime}_{x} B_{1 - x} B^{prime}_{x} O_{3}, where A = Bi or La, A′ = Sr, B = Fe or Mn, B′ = Co, x = 0 or 0.2, by calcination at 700 °C (for 1 h) of corresponding metal citrate xerogels. Materials thus obtained were examined for bulk and surface characteristics using X-ray diffractometry, ex situ Fourier transform infrared spectroscopy, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and N2 sorptiometry. Their redox catalytic activity was evaluated towards a 2-propanol dehydrogenation reaction in the gas phase by employing in situ Fourier transform infrared spectroscopy. The results obtained could help reveal that (1) the presence of Bi (versus La) and Mn (versus Fe) facilitated the formation of polymeric crystalline phases assuming lattice-charge imbalance (due to excess positive charge), (2) the surface exposure of the excess positive charge was manifested in the generation of Mn sites having various oxidation states ≥ 3+, (3) the consequent development of visible light absorptions at 498–555 nm suggested occurrence of electron double-exchange facilitated by the formation of Mnn+–O2−–Mn(n+1)+ Zener-type linkages, and (4) the exposure of such linkages at the surface warrants the establishment of the electron-mobile environment necessitated by the redox catalytic activity. Moreover, the relationship between the alcohol dehydrogenation activity and the magnitude of the lattice-charge imbalance (i.e., the net excess positive charge) of the catalysts was highlighted.

The Effect of Different g-C3N4 Precursor Nature on Its Structural Control and Photocatalytic Degradation Activity

Due to its good visible-light photocatalytic activity and environmental friendliness, g-C3N4 has attracted much attention. The relationship between precursor type and the properties of obtained catalysts is interesting to investigate. In this work, target catalysts were prepared via the thermal polymerization of different precursors, melamine, a mixture of urea and melamine, and a mixture of melamine and cyanuric acid. The prepared g-C3N4 were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), and scanning electron microscopy (SEM). Through the characterization and analysis, the adjusting of precursors could result in the change of the microstructure. The maximum BET surface area was 98.04 cm3g−1 through precursor controlling, more than eight times that of MCN (11.15 cm3g−1) using melamine as precursor. The thermal decomposition process was also analyzed to discuss the interaction and polymerization with precursor controlling. The introduction of melamine and cyanuric acid with melamine as precursors led to the formation of a special nanotube structure and additional function groups on the surface of g-C3N4 to increase the photocatalytic activity.

Effective Malachite Green Degradation over the Noble Metal-Doped and MOF-Coupled CsSnBr3 Nanocomposite Catalyst

Environmental protection laws require effective and green solutions to tackle water and air pollution issues. For this purpose, perovskite photocatalytic materials have proven to be a promising solution. In this study, CsSnBr3 perovskite, coupled with ZIF-67 and decorated with noble metal Au, was shown to effectively enhance the charge separation and increase the light-absorbing capacity, and thus make the photocatalytic reaction more efficient by surface plasmon resonance. Characterization results from XRD, FTIR, and UV-visible diffuse reflectance spectroscopy indicated that a mixture of cubic and tetragonal crystalline phases was found in the prepared catalyst material. XPS also revealed that in the presence of two oxidation states for tin (Sn), the Au 4f XPS peaks of Au NPs coincided with those retained in colloidal Au particles. Using malachite green as a model compound, organic pollutant photocatalytic degradation tests proved that CsSnBr3 generated good photocatalytic activity for aromatic pollutant degradation. In this research, the synthesized 4Au-7ZIF-CsSnBr3 catalyst yielded an MG degradation rate twice as high as the unpromoted CsPbBr3.

Integration of CuS/ZnIn2S4 flower-like heterojunctions and (MnCo)Fe2O4 nanozyme for signal amplification and their application to ultrasensitive PEC aptasensing of cancer biomarker

Vascular endothelial growth factor 165 (VEGF165) is a crucial regulator of angiogenesis and works as a major protein biomarker of cancer metastasis. Therefore, its quantitative detection is pivotal in clinic. In this work, CuS/ZnIn2S4 flower-like heterojunctions had strong and stable photocurrents, which behaved as photoactive material to construct a photoelectrochemical (PEC) aptasensor for detecting VEGF165, combined by home-prepared (MnCo)Fe2O4 nanozyme-mediated signal amplification. The interfacial photo-induced electron transfer mechanism was chiefly discussed by UV–vis diffuse reflectance spectroscopy in details. Specifically, the (MnCo)Fe2O4 modified VEGF165 aptamer was released from the PEC aptasensing platform for its highly specific affinity to target VEGF165, which terminated the color precipitation reaction, ultimately recovering the PEC signals. The developed sensor displayed a wider linear range from 1 × 10−2 to 1 × 104 pg mL−1 with a smaller limit of detection (LOD) of 0.1 fg mL−1. This study provides some valuable insights for building other ultrasensitive aptasensors for clinical assays of cancer biomarkers in practice.