Diffuse Reflectance UV Research Articles

Influence of Cr and Fe doping on the structure, magnetic and optical properties of nano CuCo2O4

Nano CuCo2-xMxO4 (x = 0, 0.1, 0.2, M = Cr or Fe) samples were synthesized by hydrothermal method. Synchrotron x-ray diffraction data obtained for the samples were subjected to phase analysis and manifested a single-phase cubic spinel structure for Cr-doped samples, while for Fe-doped samples two phases were identified. Cation distribution and cell parameter (a) were obtained from Rietveld X-ray diffraction analysis. FTIR analysis affirmed the formation of the cubic spinel and the cation distribution obtained. The nano nature of the samples and the particle morphology were examined by high-resolution transmission electron microscope (HRTEM) with selected area electron diffraction (SAED). UV-diffuse reflectance revealed that all samples have two optical energy gaps. For all Fe doped samples, the optical band gaps decreased, while for Cr-content x = 0.1 the bandgaps increased then reduced for x = 0.2. Doped samples exhibited a blue or red shift depending on the kind and amount of the dopant ions. The PL intensity and the emitted colors depended on the kind and amount of the dopant ions. Magnetic measurements disclosed the paramagnetic nature of CuCo2O4, while a weak ferromagnetic is revealed for CuCo2-xCrxO4 and a ferromagnetic nature for CuCo2-xFexO4. Lowering the bandgap upon doping could make better mobility of lattice oxygen and enhancing the catalyst reducibility. Thus, the Cr and Fe-doped samples are expected to have better catalytic activity than the pristine one.

A 2D-layered Cd(II) MOF as an efficient heterogeneous catalyst for the Knoevenagel reaction

A Cd(II) coordination polymer based on a polytopic compartmental ligand was synthesized, and used as an efficient heterogeneous catalyst for the Knoevenagel reaction between benzaldehyde and malononitrile under mild reaction conditions. The solid catalyst was characterized using single crystal XRD, X-ray powder diffraction, SEM, TGA, UV diffuse reflectance, infrared spectroscopy and elemental analysis. The compound is a two-dimensional (2D) MOF with a grid structure. Topological analysis of the framework revealed that it is a 2,4-connected binodal net. The catalytic activity was tested between various benzaldehydes containing different substituents with malononitrile. The effect of reaction parameters such as solvent, time, reactant ratio and catalyst amount was investigated. Furthermore, the catalyst stability was examined through reusability experiments and it is observed that the catalyst can be recycled at least five times without significant drop in its activity.

Characterization and luminescence sensing behaviour of a newly constructed hydrolytic stable Pb(II) coordination polymer

Sensing and detecting toxic pollutants like Fe3+, chromate anions and trinitrophenol (TNP) in water are especially important due to their hazardous effects on environmental and ecological systems. In this work, the hydrolytic stable Pb(II) CP {[Pb(asba)(obix)]•2H2O}n (1) [H2asba = 2-amino-4-sulfobenzoic acid, obix = 1, 2-(methylenebenzene)bisimidazole] was constructed and well characterized. 1 exhibits reversible de-/re-hydration behavior. The wide indirect band gap was obtained through the analysis of the solid-state diffuse reflectance UV–Vis spectrum of 1, which is consistent with the calculated value using the CASTEP program in Materials Studio. 1 keeps its crystallinity and structural integrity in various solvents. Interestingly, 1 shows solvent-dependent fluorescence emissions. A strong blue fluorescence emission occurs in water. 1 can sense the Fe3+ and chromate anions selectively and sensitively in the presence of the co-existent different metal cations and inorganic anions, respectively. Moreover, 1 also shows efficient sensing of Fe3+ in the simulative biological system. Furthermore, 1 demonstrates sensitive sensing of TNP. 1 displays excellent recyclability in sensing of these analytes. 1 can determine the related trace analytes in ppm level.

Effect of Mg and Cu doping on structural, optical, electronic, and thermal properties of ZnS quantum dots

Undoped and 10% Mg or Cu-doped ZnS quantum dots (Zn0.9Mg0.1S and Zn0.9Cu0.1S) were prepared by a simple chemical method at low temperature (300 °C). The effect of doping on structural characteristics was investigated using Rietveld profile method and the high-resolution transmission electron microscope techniques. Differential scanning calorimetry (DSC) scans were recorded in the temperature range 23–600 °C with different heating rates (5 to 30 °C/min). The model-free isoconversional method was applied to explore the effect of doping on the reaction and the growth mechanism of nano-ZnS. Diffuse UV reflectance revealed an increase of the optical energy gap upon doping with Mg, while it decreased as ZnS was doped with Cu. The change in energy gap upon doping was explained using density function theory calculation. The photoluminescence (PL) spectra revealed violet, blue, green colors depended on the composition and excitation wavelength used in the study. The intensity of PL has been increased for doped samples compared with pristine ZnS. Tuning the energy gap of ZnS through doping enable applications for light-harvesting and photocatalytic degradation in the visible region.

Highly efficient Imprinted Polymer Nanocomposites for photocatalytic desulfurization of real diesel fuel

The well-prepared imprinted nanocomposite polymer (MIP/AgPx) was used as a highly photo-active material in the oxidative desulfurization process. The synthesized nanocomposites were characterized using various analytical techniques including X-ray diffraction (XRD), UV diffuse reflectance spectroscopy (UV-DR), Fourier-transform infrared spectroscopy (FTIR), Photoluminescence spectroscopy (PL), and scanning electron microscope (SEM). The experimental parameters of the photo-desulfurization process, such as the source of radiations, the dosage of catalyst, reaction time, and addition of oxidizing agents such as hydrogen peroxide (H 2 O 2 )/acetic acid, were evaluated. The photo-degradation efficiency of dibenzothiophene (DBT, 450 ppm) was achieved ∼ 96% at room temperature in the presence of oxidizing agents with irradiation time 2h using xenon lamp (420 nm, 500 W). The removal efficiency enhanced to be 98% at the optimum conditions with high-quality diesel index: 96.17. The photocatalytic activity was attributed to the reduction of the recombination rate between electrons & holes and fast charge transfer. Furthermore, the MIP/AgP25 can be quickly recovered and reused by simple filtration for six times with a negligible decrease in the catalytic performance. • The imprinted polymer MIP/AgPx was used in the oxidative desulfurization process. • The catalytic photochemical process has highly proven desulfurization performance. • The treatment of real diesel leads to 96% degradation of organic sulfur compounds. • The prepared composite proven to be reused for 6 times with high activity and stability.

Facile fabrication of green nano pure CeO2 and Mn-decorated CeO2 with Cassia angustifolia seed extract in water refinement by optimal photodegradation kinetics of malachite green.

To eradicate the aquatic pollution caused by dyes, trendily the global researchers provide dedication to dye degradation using nanostructured photocatalyst. This research work is dedicated to explore an advanced, facile, bio-compact green fabricated nanostructure for water refinement. In this regard, plant-mediated syntheses of pure CeO2 and Mn-decorated CeO2 nano-powders have been inspected using seed extract of Cassia angustifolia. Investigations through UV-diffuse reflectance spectroscopy explored the significantly tuned band gap of Mn:CeO2. FT-IR spectroscopy shows the existing functional groups of high-potential phenolic compounds, proteins, and amino acids in Cassia angustifolia act as reducing and capping agents involved in the green fabricated nanostructured samples. X-ray diffraction pattern has been exposed to crystalline cubic fluorite morphology in a single phase and it leads to a regulated optimized amount of Mn on CeO2 nanostructure. The FESEM analysis predicts the morphology of CeO2 in spherical and Mn:CeO2 in flower-like structure. The HRTEM analysis has portrayed particle size of CeO2 is 11nm and tuned Mn:CeO2 nanostructure is 9nm. The HRTEM images revealed the average particle size in the range 10-12nm in CeO2 and 8-9nm in 5mol% Mn:CeO2 nanoparticles. It showed a decrease in average particle size with an increase in Mn concentration and the reduction in size may be due to the replacement of Ce(IV) with Mn(II) ions. The elemental composition in nanostructure was predicted using energy-dispersive X-ray analysis. The rapid photocatalytic degradation efficiency of malachite green was effectually performed and compared with the kinetics model of Mn:CeO2 and pure CeO2 nanostructures. From the augmented results, tuned Mn:CeO2 was found to act as the finest green fabricated photocatalyst in the amputation of lethal and carcinogenic dye.

Fabrication of Hierarchical Indium Vanadate Materials for Supercapacitor Application.

Transition metal orthovanadates are emerging 2D materials for promising electrochemical energy storage applications. Facile hydrothermal method for nanocrystalline indium vanadate (InVO4) semiconducting materials’ fabrication is economical because of its direct chemical synthesis. X‐ray diffraction studies, field emission scanning electron microscope (SEM) images, transmission electron microscopy (TEM), and photoelectron X‐ray spectrum are used to describe the semiconductor materials as synthesized. InVO4 microspheres have attracted a lot of attention in the energy and environmental sector. These microsphere‐derived semiconductor materials are recognized to offer the advantages of their large surface area, tunable pore sizes, enhanced light absorption, efficient carrier (electron–hole) separation, superior electronic and optical behavior, and high durability. From the results of SEM and TEM, InVO4 shows a microsphere construction with a mixture of nanosized particles. Diffuse reflectance UV–visible measurements are used to determine the bandgap, and it is found to be 2.1 eV for InVO4. The electrochemical analysis reveals a superior performance of the pseudocapacitor with hydrothermally derived microspheres of InVO4. Alongside an improved pseudocapacity, developed after 4000 cycles, it has excellent cycling stability with a retention of ≈94% of its original specific capacitance efficiency.

Application of PANI/TiO2 Composite for Photocatalytic Degradation of Contaminants from Aqueous Solution

Polyaniline (PANI) is a promising conducting polymer for surface modification of TiO2 to achieve extended photoresponse to visible light and increased photocatalytic efficiency. In this study, we report the synthesis of a PANI/TiO2 composite with different weight ratios of PANI, which was subsequently employed for photocatalytic degradation of methylene blue (MB), bisphenol A (BPA), and bacteriophage MS2 under visible-light irradiation. The functional groups, morphology, and light response of the composite were characterized by Fourier-transform infrared spectroscopy, field-emission transmission electron microscopy, and diffuse reflectance UV–visible spectroscopy, respectively. The PANI/TiO2 composite containing 4% by weight ratio of PANI was most suitable for MB degradation, and this photocatalyst was very stable even after repeated use (four cycles). The degradation of BPA and bacteriophage MS2 by PANI/TiO2 composite reached 80% in 360 min and 96.2% in 120 min, respectively, under visible-light irradiation. Therefore, the PANI/TiO2 composite with enhanced visible-light photocatalytic efficiency and stability can be widely used for the degradation of water contaminants.

Effect of bismuth (Bi3+) substitution on structural, optical, dielectric and magnetic nature of La2CoMnO6 double perovskite

Double perovskite oxide materials represented as A2BB′O6 have attracted a great attention due to their diverse electrical, magnetic and structural properties. In this report, we discuss synthesis, structural, optical, magnetic and electric nature of the double perovskite manganites of the type La2−xBixCoMnO6 [x = 0.0, 0.1, 0.2]. These solid-state reaction route products with x = 0.0, 0.1 were found monoclinic structured (P 1 21 / n 1) confirmed from the X-ray diffraction data analysis, whereas the sample with x = 0.2 has acquired a new structure confirmed to be cubic (Fm-3 m) with another phase corresponding to Bi2O3 crystallized in monoclinic structure acquiring space groups P 1 21 / c 1. The results of XRD data analysis were re-verified via Rietveld refinement. The phase formation was further verified via Raman and FTIR spectral studies. The samples were investigated for composition and morphology also. The optical bandgap was determined (≈ 1 eV) from the diffuse reflectance UV–Vis spectra. Temperature-dependent dielectric constant and dielectric loss was investigated in the temperature range of 320–90 K at various constant values of applied ac field and the results were exceptionally good. Electrical (dc) resistivity exploiting four-probe technique with and without magnetic field infer the samples are semiconducting in nature. Room temperature magnetic measurement reveals the samples exhibit low magnetic moment which shows linear behaviour in both forward and reverse field values.

Catalytic and photocatalytic epoxidation of limonene: Using mesoporous silica nanoparticles as functional support for a Janus-like approach

Mesoporous silica nanoparticles (MSN) were used as a platform to design novel active materials for the catalytic and photocatalytic epoxidation of limonene. Binary systems comprised of TiO2 and MSN were used for the catalytic reaction when doped with manganese, and for the photocatalytic reaction when functionalised with hexadecyl chains or imidazolinyl groups. All of the MSN based systems were synthesized by condensation in emulsion. A thorough characterization of the powders has been performed by means of Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES), X-ray diffraction (XRD), FT-IR, Raman and EPR Spectroscopy, Fluorescence and diffuse reflectance UV–vis (DRS) Spectroscopy, gas Porosimetry, and Transmission Electron Microscopy (TEM). The obtained morphological and structural information have been related to the catalytic and photocatalytic performances for the epoxidation of limonene. MSN support finely distributes the manganese active centres in the case of the catalytic epoxidation, while acts as functional co-catalyst in the case of the photocatalytic reaction. Upon careful optimization of the experimental conditions, the catalytic process afforded conversion and selectivity values up to 90 and 84%, respectively, while the photocatalytic process provided in the best case conversions up to 80% and selectivity values of ca. 50%. Both the catalytic and photocatalytic approaches were performed under relatively mild experimental conditions and use molecular oxygen as the oxidant. Therefore, both of them represent promising green alternatives to traditional methods for the industrially relevant production of limonene epoxide. This compound, in fact, is the starting material for the production of poly(limonene carbonates), biopolymers with outstanding properties which are promising substitutes of oil derived polycarbonates.

Bi2S3 anchored ZnS/ZnO nanorod arrays photoanode for enhanced visible light driven photo electrochemical properties

We report on the enhanced photoelectrochemical water splitting of hybrid ZnS/ZnO core-shell nanorod arrays functionalized with Bi2S3 nanosheets as photoanode. The ZnO nanorod arrays were prepared by a facile hydrothermal approach and sulphurized to form ZnS shell. Subsequently porous Bi2S3 nanosheets were arbitrarily decorated on the nanorod arrays by ionic adsorption and reaction method. Substantial enhancement in photocurrents with twofold increment is observed for hybrid photoanode compared to pristine counterparts. The structural and morphological properties of nano hybrid Bi2S3/ZnS/ZnO samples were analyzed by field emission scanning electron microscopy and X-ray diffraction. The higher wavelength shift in the absorption edge of Bi2S3/ZnS/ZnO photocatalyst was observed in diffuse reflectance UV–Visible spectra. The low temperature photoluminescence and impedance spectra of Bi2S3/ZnS/ZnO photoanode confirm that Bi2S3 functionalization reduces the recombination of electron–hole pair and facilitates barrier free charge transfer. The Bi2S3/ZnS/ZnO photoanode device exhibits photocurrent density of 220 μA/cm2 at 0.2 V vs. Ag/AgCl under the electrolyte solution at pH ~10.8. The resultant hybrid photoanode withhold good stability and maintain the facile charge carrier generation and separation. Bi2S3 topological nanosheets are responsible for the absorption of complete visible photons while ZnS/Bi2S3 inter-junction provides the robust electron-hole pair separation at their interface due to infiltration pathway. The photoactive hybridization of Bi2S3/ZnS/ZnO provokes the enhanced donor charge density for efficient hydrogen evolution reaction.

Features of Lignin Destruction in Wood under the Action of Ozone

Samples of pine wood ozonated with different contents of water are studied via UV diffuse reflectance spectroscopy. It is shown that polyaromatic and stilbene structures, guaiacyl derivatives, and carbonyl- and carboxyl-containing aromatic structures of lignin are destroyed during ozonation of pine wood. The destruction of aromatic structures proceeds efficiently in wood with a moisture content of more than 60–65% in the 2–3 mmol/g range of ozone consumption. When the moisture content is below 40%, ozone treatment of pine wood at low ozone consumption allows us to obtain different modifications of oxygen-containing aromatic and polyaromatic structures on surfaces of lignocellulosic material (LCM). IR absorption spectra of dioxane lignin obtained from the initial and ozonated wood samples confirm the different direction of lignin transformations, depending on the content of moisture in the wood.

Investigation on structural, optical and electrochemical behavior of NiO/ZnMn2O4 ternary nanocomposites via two-step synthesis approach for supercapacitor application

The present investigation deals with the synthesis of nickel oxide (NiO)/zinc manganite (ZnMn2O4) nanocomposites (NCs) by a two-step approach. The powder X-ray diffraction (PXRD) pattern revealed the existence of face-centered cubic (FCC) phase of NiO and tetragonal rutile phase structure of ZnMn2O4 in NiO/ZnMn2O4 NCs. The optical properties of NiO/ZnMn2O4NCs have been investigated by the UV-diffuse reflectance Spectroscopy (UV-DRS) and photoluminescence (PL) spectral analysis. The surface morphology and elemental composition of NiO/ZnMn2O4NCs was investigated by field emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectrum (EDX) analysis. The surface area and the nature of porosity of the samples were analyzed using Brunauer–Emmett–Teller (BET) method. The electrochemical properties were investigated from the cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements. In 0.5 M potassium hydroxide (KOH) electrolyte solution, NiO/ZnMn2O4NCs exhibited higher specific capacitance of 886 F/g at a current density of 1Ag−1 with high cyclic stability over 1000 charge–discharging cycles. Thus, the result demonstrates that the prepared NiO/ZnMn2O4NCs is a promising electrode material for future energy-storage devices.

Synthesis, characterization and investigation of photocatalytic activity of ZnMnO3/Fe3O4 nanocomposite for degradation of dye Congo red under visible light irradiation

ZnMnO3/Fe3O4 magnetic nanocomposites were fabricated via facile co-precipitation route and were calcined at 400 °C for 3 h. Synthesis of ZnMnO3/Fe3O4 magnetic nanocomposites were optimized by different weight percentages. Then, the as-synthesized sample was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), photoluminescence(PL), vibrating Sample Magnetometer (VSM), EDAX (Energy dispersive X-ray analysis), diffuse reflectance UV–Vis spectroscopy (DRS),ultraviolet–visible (UV–Vis) spectrometry, Bruner-Emmett-Teller (BET), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Based on the results, elemental analyses of the samples were similar to those expected from the initial concentrations of the solutions used during synthesis. The x-ray diffraction pattern revealed that ZnMnO3/Fe3O4 has a cubic structure and average particle size of the catalyst was found 27.43 nm. In addition, Fourier transform infrared spectra could confirm the presence of hydroxyl group and Fe–O bond vibration in the catalyst. Further, the superparamagnetic behavior of the synthesized nanocomposite at room temperature was confirmed by VSM studies. Furthermore, the photocatalytic performance of ZnMnO3/Fe3O4 samples were evaluated based on the removal of Congo red (CR) in aqueous solution in 60 min of under visible light irradiation. The experiment demonstrated that 0.10 g of ZnMnO3/Fe3O4 nanocomposites can degrade (98.17%) 50 mg l−1 of Congo red (CR) solution. The mechanistic study using scavengers propose that the superoxide (O2·−) is the most reactive species involved in the photodegradation of organic dyes. The photocatalytic degradation of Congo red conformed the pseudo-first-order kinetic model and the rate constant achieved for 0.10 g l−1 of ZnMnO3/Fe3O4 was (k = 0.0384 min−1). Finally, the effect of reaction time, pH, and loading of ZnMnO3/Fe3O4 on degrading Congo red was studied. The synthesized ZnMnO3/Fe3O4 nanocomposite can be potentially applied as a magnetically separable photocatalyst to deal with water pollution problems.

Mesoporous Ce-doped Ti:Ash Photocatalyst Investigation in Visible Light Photocatalytic Water Pretreatment Process

The treatment of organic pollutants in water including semiconductor photocatalysis is a promising approach to disinfect water. The objective of this study is to investigate the effect of Ce loaded on mesoporous Ti:Ash catalyst for water pretreatment process. The mesoporous Ti:Ash catalyst that doped with Ce was synthesized through wet impregnation method with 5%, 10%, and 15% weight percentage of Ce doped on 40:60 Ti:Ash. The photocatalytic properties were characterized through X-ray powder diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, N2 adsorption-desorption studies and diffuse reflectance UV–vis absorption spectroscopy. It is found that the Ti:Ash nanocomposites doped with Ce shifted the light absorption band-edge position to the visible region. Moreover, the Ce doped Ti:Ash has large surface area and pore diameter. The Ce doping could significantly improve the absorption edge of visible light and adjust the cut-off absorption wavelength from 404 nm to 451, 477 and 496 nm for 5%, 10% and 15% Ce-doped mesoporous Ti:Ash catalysts, respectively. As the Ce doping ratio increased, the band gaps decreased from 3.06 eV to 2.53 eV. The most contaminant reduction up to 45% was achieved when Ti:Ash:Ce 40:55:5 was used. Higher Ce loading on the photocatalyst may reduce the photocatalyst performance because supernumerary metal loading on TiO2 can block TiO2 defect sites which are necessary for the adsorption and photoactivation. The OPFA also acts as an adsorbent for some pollutants besides, reducing the water salinity. It can be deduced that the hybrid TiO2 photocatalyst that synthesized with OPFA and doped with Ce has huge potential to treat seawater prior to commercial seawater desalination process. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

A new bonded silica based on an amino acid derivative as a TLC stationary phase to solve nitrophenol structural isomerism and ibuprofen stereoisomerism

BackgroundMany amino acids and their derivatives have been used previously as chiral selectors in thin layer chromatography. Herein, we reported the synthesis, characterization, and chromatographic evaluation of a new modified stationary phase based on (S)-3-(aminomethyl)-5-methylhexanoic acid (also known as pregabalin) as an amino acid ligand bonded to the silica surface via triazine attachment.ResultsSC-2P (silica-cyanuric-2-pregabalin) is a bonded silica stationary phase prepared by direct binding of the pre-synthesized cyanuric-2-pregabalin organic ligand on the chlorinated silica surface. FT-IR and UV diffuse reflection spectroscopy (UV-DRS) were used to characterize the synthesized bonded phase, and the specific surface area was determined using the methylene blue Langmuir isotherm method to be 147.04 m2/g. TLC plates were prepared from a slurry of this synthesized material with 2 mM of Cu2+ as a selector additive, and the chromatographic characteristics of these plates were investigated to separate a ternary mixture of o-, m-, and p-nitrophenol as structural isomers, and a racemic mixture of (±)-ibuprofen as stereoisomers. Solvent systems of n-hexane:dichloroethane:n-propanol (75:20:5, v/v/v) and Dichloroethane:acetonitrile (90:10, v/v) were selected as mobile phases for nitrophenol and ibuprofen mixtures, respectively. The successful separation was densitometrically confirmed, and retardation factors (Rf) were determined for o-, m-, and p-nitrophenol at 320 nm to be 0.83, 0.45, and 0.28, and for R(−)-, S(+)-ibuprofen at 220 nm to be 0.43 and 0.63, respectively.ConclusionThe synthesis, characterization, and chromatographic evaluation of SC-2P were reported in this article. SC-2P was used with copper ions to form in situ ligand exchange reagent (LER), which was successfully employed to solve an isomeric mixture of nitrophenol and a racemic mixture of (±)-ibuprofen. The synthesized stationary phase showed high repeatability with minimum Rf shifts between batches.

Synthesis of TiO2/reduced graphene oxide–Al2O3 composites and their advanced properties for photocatalysis

The TiO2/reduced graphene oxide (RGO)-Al2O3 composites were synthesized by dispersing TiO2 on RGO-modified Al2O3 by impregnation method. The surface properties of TiO2/RGO–Al2O3 were systematically studied. It was found that the TiO2 particle size was about 15 nm, and the particles were relatively uniform in the loading range of 20–40 wt% compared with that of Al2O3. The surface area increased obviously as RGO was added to Al2O3. The chemical structures of the TiO2/RGO–Al2O3 composites were characterized by diffuse reflectance UV–Visible spectroscopy and X-ray photoelectron spectroscopy. Results revealed the presence of an intense interaction between TiO2 and RGO–Al2O3. The dark adsorption results showed that the TiO2/RGO–Al2O3 had a higher adsorption ability for methyl orange (MO), which was mainly due to the π-π conjugation between MO and RGO. The liquid-phase photocatalytic oxidation of MO was adopted to evaluate the efficiency of the obtained materials. TiO2/RGO–Al2O3 showed higher catalytic efficiency over the TiO2/Al2O3 or the commercial P25 photocatalyst. Recycling tests showed excellent stability of TiO2/RGO–Al2O3. The TiO2/RGO–Al2O3 was easier to separate by filtration method than TiO2 due to its high anti-hydration dispersion ability. The studies indicated their good prospects for large-scale application.

Single wall carbon nanotubes growth over cobalt-iron mesoporous MCM-41 bimetallic catalyst under methane chemical vapor deposition, an experimental and DFT evaluation

Cobalt and iron MCM-41 catalysts were synthesized through an in-situ incorporation process starting from commercial iron and cobalt nitrates. The incorporation was confirmed by diffuse reflectance UV spectroscopy (DRS-UV) inspecting the cobalt and iron silicate-like photon absorption features and comparing with pure MCM-41-Co and MCM-41-Fe catalysts. Additionally it was found that the incorporation of cobalt and iron does not compromise the mesoporous structure of MCM-41 as confirmed by N2 adsorption isotherms. All catalysts showed high surface areas (∼1100 m2g−1). Catalysts performance was conducted in a simple methane chemical vapor deposition (CVD) set up at 800 °C to produce single wall carbon nanotubes (SWCNT) under a constant flow of methane for 30 min. CVD products were characterized by thermogravimetric analysis (TGA) and Raman spectroscopy, finding that the iron content in the catalysts favors the selectivity and yield of graphitic-like structures, and confirming the presence of SWCNT by the appearance of a characteristic radial breathing mode (RBM) signals. These results were supported by Density Functional Theory (DFT) simulations of the methane dissociation (CH4 +TM → H3C –TMH) over Con (n = 1–5) and ComFe (m = 1–4), finding a different activation energy trend where ComFe (m = 1–4) clusters have the lower activation energy. The DFT study also revealed a charge difference (δC − δTM) higher in the case of dissociation over ComFe (m = 1–4) which may lead to an electrostatic stabilization of the transition metal, diminishing the activation energy of those clusters and leading to a faster carbon uptake.

A New Zinc-based Metal Organic Framework as a Stationary Phase for Thin Layer Chromatography


 Metal organic frameworks (MOFs) are a variety of micro-porous materials which have high surface area, and permanent porosity making them possible options as chromatographic stationary phases. Herein we reported the synthesis and characterization of a new MOF structure and its utilization as a stationary phase for thin layer chromatography (TLC). [Zn(BMAB).DMF]n is a zinc-based MOF with an organic linker consists of chemically distinct binding groups which is 4-{[(1h-1,2,3-benzotriazol-1-yl)methyl]amino}benzoic acid (BMAB). This MOF was synthesized using ultra sound assisted reaction process, then activated via solvent exchange protocol to preserve its porous structure. FT-IR, UV-diffuse reflection spectroscopy (UV-DRS) and differential scanning calorimetry (DSC) were performed to characterize the synthesized MOF. Integrated data from "loss on desolvation" and atomic absorption spectrophotometry (AAS) measurements were used to define the chemical composition of the synthesized material. A specific surface area of 122.9 m2/g was determined for the activated MOF using methylene blue langmuir isotherm method. TLC plates were prepared from the activated form of the structure to investigate its chromatographic characteristics by utilizing it to separate a model mixture of benzidine and o-tolidine using n-propanol: Chloroform: Acetonitrile (50:30:20, v/v/v) as a mobile phase. The retardation factors (Rf), separation factor, and resolution (Rs) were determined via densitometric method at 310 nm to be 0.45 and 0.63 (α=2.08, Rs=1.61) for o-tolidine and benzidine; respectively. The plate was then visualized using iodine chamber method to confirm a successful separation.

Photodegradation of methylene blue and methyl orange with CuO supported on ZnO photocatalysts: The effect of copper loading and reaction temperature

Copper oxide supported on zinc oxide catalysts was tested for the photocatalytic degradation of methylene blue (MB) and methyl orange (MO) dyes under UV irradiation at 25, 35 and 45 °C. These Cu/ZnO catalysts with variable copper loadings (2.5, 5 and 7.5 wt%) were prepared by impregnation and characterized by atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), N2 adsorption–desorption, transmission electron microscopy (TEM), diffuse reflectance UV–visible absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS). XRD and XPS data revealed that copper was in the form of copper oxide (CuO), and the crystal size was 240.8 and 49.3 nm for ZnO and CuO, respectively. Experiments showed that xCu/ZnO catalysts were highly active for MB and MO degradation compared with the zinc oxide supports due to the presence of copper oxide acting as an electron trap inhibiting electron-hole recombination. Furthermore, photodegradation activity was improved with increasing temperature. The 5Cu/ZnO catalyst exhibited greater degradation activity in both dyes, reaching 99% degradation at 45 °C after 15 and 75 min for MB and MO, respectively, due to its greater dispersion of CuO in ZnO and higher concentration of hydroxyl groups on the surface compared with other catalysts. Thermodynamic calculations indicated that the interaction of MB with the surface was stronger than that of MO and possibly related to the presence of hydroxyl groups on the surface, as indicated in the XPS results. The effects of different scavengers of the main species involved, such as hydroxyl radicals, superoxide radical anions and positive holes, were studied to propose photodegradation mechanisms of the dyes on these systems. The superoxide radical was the main reactive species during the photocatalytic degradation of MB and MO.