BET-BJH Analyses Research Articles

Fabrication of ZiF-8 metal organic framework (MOFs)-based CuO-ZnO photocatalyst with enhanced solar-light-driven property for degradation of organic dyes

In this study, CuO-ZnO/ZiF-8 was successfully synthesized with different percentages of ZiF-8 Metal-organic Framework (MOF) via ultrasound assisted precipitation method. The physic-chemical properties of the samples were studied by XRD, FESEM, EDX, BET-BJH, FTIR, DRS, and pH pzc techniques. The results showed that the CuO-ZnO/ZiF-8 (20) sample possesses high photocatalytic activity with 98.1% removal of 80 ppm AO7 in 100 min. It could be attributed to the increases the surface area, the pore volume, and pore diameter, as well as efficient homogenous distribution of active sites due to the use of ultrasound irradiation. Furthermore, the presence of ZiF-8 increases light absorption and reduces the recombination rate of electron-hole pairs. • Successfully synthesis of CuO-ZnO/ZiF-8 by ultrasonic assisted precipitation method. • Promising physicochemical and optical properties of the synthesized nanocomposites. • High photocatalytic activity of CuO-ZnO/ZiF-8 (20) (98.1% degradation of AO7) • Investigation of the effective operating parameters on AO7 photodegradation performance. In this research, novel CuO-ZnO/ZiF-8 metal–organic frameworks (MOFs) photocatalyst with different mass percentages of ZiF-8 were prepared for water purification applications under visible light. The precipitation method was used to synthesize CuO-ZnO/ZiF-8 photocatalysts. Some techniques, including XRD, FESEM, EDX, BET-BJH, FTIR, DRS, and pH pzc, were performed to determine the structural, chemical, and optical properties of the prepared samples. DRS analysis represented that CuO-ZnO/ZiF-8(20) had narrower band gap energy compared to CuO-ZnO and ZiF-8. Also, BET-BJH analysis results showed that CuO-ZnO had a low surface area that impeded the absorption of pollutant molecules. In contrast, the CuO-ZnO/ZiF-8(20) sample, due to the presence of ZiF-8, had a high specific surface area which enabled higher pollutant adsorption on the photocatalyst surface. Moreover, the synthesized samples were evaluated for the solar-light-driven removal of different organic dyes, such as Acid Orange 7, Methylene blue, and Malachite green. The tremendously enhanced photocatalytic activity under the simulated solar light with 98.1% removal of AO7 was observed over CuO-ZnO/ZiF-8(20) sample. Then, the effect of initial solution pH as an essential factor on photocatalytic activity was investigated. Finally, the reaction mechanism of AO7 degradation over CuO-ZnO/ZiF-8(20) was proposed.

Sun-light driven photo degradation of organic dyes from wastewater on precipitation Ag2CrO4 over SiO2-aerogel and nano silica

In this study, Ag2CrO4/SiO2 nanostructure was synthesized by the precipitation method to ameliorate the low specific surface area of Ag2CrO4 with nano-Silica (NS) and Silica Aerogel (SA). The coupled nanophotocatalysts with various weighted contents of Ag2CrO4 and Nano Silica were characterized with PXRD, FESEM, UV–Vis, FTIR and BET-BJH analyses. In order to find the optimal amount, different percentages of Nano Silica 10%, 20% and 30% were investigated. It was observed from BET-BJH that adding Nano Silica lead to an increase the catalyst surface area and crystallinity of synthesis samples. Then, in order to investigate the impact of specific surface area on optimal catalyst activity (Ag2CrO4/Nano Silica (20%)), Silica Aerogel, which has a higher surface area than Nano silica, was used instead of Nano silica. It was observed that increasing the surface area has a direct effect on the activity of the Ag2CrO4. The photocatalytic activity of various nanocomposites was evaluated in the remediation of the organic dyes after 120 min visible light irradiation. The tremendous enhanced photocatalytic activity under the simulated solar light with 95.4% removal of AO7 was observed over Ag2CrO4/Nano Silica (20%) sample. In addition, to illustrate how the influence of various parameters such as various organic dyes, pH, catalyst loading and reusability on the photodegradation efficiency, were conducted over Ag2CrO4/Nano Silica (20). The high activity was obtained in the medium with pH = 7, catalyst loading = 1 g/L and AO7 concentration = 20 mg/L.

Clean synthesis of rock candy-like metal–organic framework biocomposite for toxic contaminants remediation

A green methodology was considered to expeditiously synthesize a new class of microporous zeolitic imidazolate framework-8 (ZIF-8) crystals associated with ZnO nodes (denoted ZIF-8/ZnO) based on the eggshell membrane (ZIF-8/[email protected]) supporting bed, to study the Malachite green (MG) and tetracycline removal. Several characterization methods were applied to analyze the properties of the materials, including FTIR, XRD, BET–BJH, and SEM/EDS/Mapping. The BET–BJH analysis validates the efficiency of the applied synthesis approach in the preparation of a high specific surface area (1498.07 m2/g) and high porous (0.061 cm3/g) ZIF-8/ZnO. Also, the N2 adsorption/desorption analysis verifies the microporous structure of synthesized ZIF-8/ZnO in the pure and composite form regarding mean pore diameters of 1.8802 and 1.6579 nm, respectively. The MG dye removal ability of ZIF-8/[email protected] nanocomposite was tested and it showed better performance in comparison with the pure ZIF-8/ZnO and ZIF-8. The results indicate that the Langmuir adsorption isotherm could explain the obtained equilibrium data with a maximum adsorption capacity of 833.33 mg/g with high accuracy (R2=0.997). Kinetic study showed that the pseudo-second-order model was capable to fit the experimental data with high correctness. Reusability test was confirmed excellent regeneration ability of ZIF-8/[email protected] even after 5th cycle (<13% diminished).

Sequential impregnation and sol-gel synthesis of Fe-ZnO over hydrophobic silica aerogel as a floating photocatalyst with highly enhanced photodecomposition of BTX compounds from water

Benzene, Toluene, and Xylene (BTX) are included in the floating contaminants which originated from the explosion of oil wells. Photocatalytic oxidation of the some oil spill components like Benzene, Toluene, and Xylene can be a proper way to solve this challenge due to its economic saving, usage of free energy, and environmentally friendly. For this purpose, we have synthesized a hydrophobic catalyst of Fe-ZnO nanoparticles inoculated with silica aerogel (SA). Various percentage of hydrophobic silica aerogel (10, 20 and 30%) was added, as support of catalyst, to Fe-ZnO nanoparticles using impregnation method. The impregnation of silica aerogel to Fe-ZnO nanoparticles caused the photocatalytic performance of nanocatalyst was improved through its increased surface area, and also floated active phase (Fe-ZnO) on water. In order to investigate the impact of the synthetic method of nanocomposite on the activity of synthesized nanophotocatalyst, optimum samples (Fe-ZnO over 20% SiO2) were synthesized using the sol-gel method. The synthesized nanophotocatalysts were characterized using PXRD, FESEM, EDX, UV–Vis, Contact Angle, FT-IR, and BET-BJH analyses. Photocatalytic activity of synthesized nanophotocatalyst was evaluated in the degradation of the BTX after 120 min, under visible light irradiation. In addition, the influence of various parameters including the addition of hydrophobic silica aerogel, pH, catalyst loading, benzene concentration, and reusability was studied on the photodegradation efficiency of Fe-ZnO/SA (20%). The most photocatalytic activity was observed in the optimum condition involving pH = 5, catalyst loading = 1 g/L, and benzene concentration = 5% V/V.

Cu(II) Schiff base complex functionalized mesoporous silica nanoparticles as an efficient catalyst for the synthesis of questiomycin A and photo-Fenton-like rhodamine B degradation

Lychee-like Mesoporous Silica Nanoparticles (LMSN) were synthesized and functionalized with 3-Aminopropyltrimethoxysilane (3-APTMS) and a novel binuclear Copper complex. The synthesized materials were characterized by UV-DRS, Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) analysis. The High Resolution Transmission Electron Microscopy (HR-TEM) analysis gives view on retention of structural order after functionalization. Thermogravimetric Analysis (TGA), low angle X-ray diffraction (XRD) and BET-BJH analyses confirmed the presence of schiff base complex moieties inside the pore architecture. Electron Spin Resonance (ESR) analysis provide evidence for the presence of paramagnetic copper and ICP-OES studies details the metal loading. The potential of synthesized material as an enzyme-mimetic catalyst for the synthesis of questiomycin A and Rhodamine B degradation agent was analysed in this work. The catalyst material served best with good yields and reusability.

Fabrication of Z-scheme Bi2WO6/CNT/TiO2 heterostructure with enhanced cephalexin photodegradation: Optimization and reaction mechanism

A Z-scheme Bi2WO6/CNT/TiO2 heterostructure was synthesized through the hydrothermal method. The photocatalysts were characterized by XRD, FTIR, SEM, EDX, TEM, UV–vis DRS, PL, and BET-BJH analyses. The photocatalytic activity of Bi2WO6/CNT/TiO2 was evaluated by the degradation of cephalexin under simulated sunlight illumination. The ternary Bi2WO6/CNT/TiO2 Z-scheme containing the optimal loading amount of 35 wt% TiO2 and 0.75 wt% CNTs, showed the best photocatalytic activity compared with pristine Bi2WO6, Bi2WO6/TiO2 and Bi2WO6/CNT/TiO2 with different mass percentage ratios. The enhanced photocatalytic activity of Bi2WO6/CNT/TiO2 was attributed to the higher specific surface area, higher visible-light adsorption spectrum, lower band gap, lower recombination of electron-hole pairs, better charge separation and higher redox ability, due to the Z-scheme construction. The optimum values of operating parameters were determined as: catalyst dose = 0.75 g/L, pH = 5, illumination time = 70 min, and cephalexin initial concentration = 20 mg/L using the central composite design. The maximum cephalexin removal efficiency in the presence of Bi2WO6/CNT/TiO2 reached 89.7% at optimum conditions. The maximum total organic carbon (TOC) removal rate was 78.9%. The photocatalytic degradation of cephalexin followed the first-order kinetic and the reaction rate by ternary composite was about 3.33 and 1.5 times, greater than those of Bi2WO6 and Bi2WO6/TiO2, respectively. The synthesized Z-scheme demonstrated an excellent chemical stability and reusability after five cyclic utilizations. According to matched Fermi level of CNTs between Bi2WO6 and TiO2, CNTs acted as electron mediator for charge transfer in the Z-scheme. Assigned to the trapping experiments, OḢ, O2−•, h+ and e- effectively improved the photodegradation process.

Effect of Size Fractionation on Purity, Thermal Stability and Electrical Properties of Natural Hematite

The present study describes the variation of grain size of natural hematite (α-Fe2O3) from bulk to nano-scale, owing to fractionation by ball milling and also the change in vital electrical properties of the products with respect to their bulk counterpart. Hematite, an important iron ore, is present in abundance in the deposits of most parts of the world. This fact was the rationale behind the selection of this mineral for the study. A gradual decrease in size via top-down synthesis technique was confirmed and the morphological parameters of the materials were analyzed using field emission scanning electron microscopy (FESEM) and corresponding pore diameter and surface area were determined by BET-BJH analysis. The studies were performed on three size fractions, namely, S1 (bulk mineral), S2 (bulk mineral, ball milled for 3 h) and S3 (bulk mineral, ball milled for 12 h). The purities of the natural mineral and its fractionated end products were estimated by using x-ray diffraction (XRD) and x-ray fluorescence (XRF) techniques. Increase in purity with decline in the particle size, especially in the nano-domain, was observed. The changes in dielectric properties of the materials with varying temperature were studied. Temperature dependence of the dielectric constant and ac conductivity were recorded, which indicated a remarkable augmentation in dielectric permittivity with reduction in size of the material. High dielectric constants of the smaller sized materials (S2 and S3) at low frequency signified their potential use in energy storage devices. Thus, using an easily available natural mineral as the starting material, an efficient energy storage appliance can be devised with a low-cost substance, synthesized by the simple approach of fractionation without employing any chemicals.

The Application of Encapsulated Trinuclear Cobalt Cluster Complex in Y Zeolite in the One-Pot Multi-Component Synthesis of Spiro Indoline Derivatives

A trinuclear cobalt cluster complex was prepared into the nanocages of dealuminated Y zeolite ([Co3(O)(CH3COO)6(py)3]-DAZY) and characterized by XRD, FT-IR, EDS, FE-SEM, AAS and BET-BJH analyses. The elemental content of Cobalt in [Co3(O)(CH3COO)6(py)3]-DAZY was estimated to be about 5.5 mg/g support on the basis of atomic absorption spectroscopy. The catalytic activity of [Co3(O)(CH3COO)6(py)3]-DAZY was evaluated in the synthesis of tri series of spiro indoline derivatives in a library synthesis via the condensation of isatins, malononitrile or ethylcyano acetate, and active methylene compounds (4-hydroxycoumarine, dimedone and pyrazoline-5-one). Corresponding products were obtained in good to excellent yields. Short reaction time, high yield of product, structural diversity of products, absence of organic solvents and the use of water as a green solvent, non-toxicity, stability and reusability of the catalyst are noteworthy advantages of the current work.

Iron oxide (Fe3O4) magnetic nanoparticles supported on wrinkled fibrous nanosilica (WFNS) functionalized by biimidazole ionic liquid as an effective and reusable heterogeneous magnetic nanocatalyst for the efficient synthesis of N-sulfonylamidines

Wrinkled fibrous nanosilica (WFNS) which functionalized by ionic liquid modified Fe3O4 NPs and CuI salts has been synthesized and characterized with FE-SEM, TEM, FT-IR, FAAS, EDX, and, XRD, VSM, and BET-BJH analysis. This new and effective magnetic ceramic nanocatalyst has been applied towards rapid synthesis of N-sulfonylamidines using reaction of phenyl acetylene, substituted sulfonyl azide and various amines under solvent-free conditions in very short reaction time. Higher catalytic activity CuI/Fe3O4NPs@IL-DFNS in the reaction is because of special structure of DFNS and existence of ionic liquids on its pores which act as a robust anchors to the loaded various nano-particles. So, this lead to no leaching of them from the pore of the composite. Shorter reaction time, higher yield, recovery of the catalyst using an external magnet and its reusability for 8 series without noteworthy reduction in its activity are the advantages of newly synthetic catalyst toward efficient synthesis of N-sulfonylamidines.

Application of ascorbic acid in the synthesis of rGO/micro-octahedral Cu2O nanocomposites and its effect on the wide linear response range of glucose detection

In this study, a simple and scalable method with the application of Ascorbic acid has been reported for the fabrication of decorated reduced graphene oxide by Cu2O micro-octahedrons (rGO/ micro-octahedral Cu2O nanocomposites) for non-enzymatic glucose sensor using differential pulse voltammetry (DPV) techniques. The structural study of rGO/ micro-octahedral Cu2O using detailed XRD analyses, Raman spectroscopy, FESEM imaging, EDX elemental mapping and BET-BJH analyses revealed that the application of ascorbic acid in the synthesis process enhances the morphology, surface area, charge transfer and electrocatalyst properties of the nanocomposite. XPS analysis revealed the significant reduction of GO with the distinct peak of C–C in the C 1 s orbital scan. Quenching of satellite peaks (Cu2+) in Cu 2p orbital scan accompanied by the appearance of Cu-C new bond were indications of CuO phase elimination and hybridization of rGO/Cu2O structure. The modified electrodes with Nafion showed a wide linear span of 1 µM- 9 mM for glucose detection, high sensitivity of 415 µA mM−1 cm−2 with low detection limit of 0.96 µM and significantly being selective among different species. The sensitivity measurement without Nafion as a Nafion-free modified electrode was still high as 24.8 µA mM−1 cm−2 with the same wide linearity range and low detection limit of 0.53 µM. The stability of 97.95% in signal change after 56 days and repeatability of the modified electrode with relative standard deviation of 4.06% were also obtained. The modified GC/rGO/micro-octahedral Cu2O electrode revealed its electrocatalytic activity toward glucose oxidation that was excellently competitive with HPLC measurement of glucose in human serum.

Enhanced simulated sunlight-driven magnetic MgAl2O4-AC nanophotocatalyst for efficient degradation of organic dyes

In this paper, with the aim of using the solar light as an unlimited and clean source of energy, novel magnetic MgAl2O4-AC nanophotocatalysts with different mass percentages of activated carbon were synthesized for water purification applications. In order to synthesize the magnetic MgAl2O4-AC nanophotocatalysts, three different methods of combustion, sono-impregnation, and sono-solvothermal were used at different stages. Different analyses such as XRD, FESEM, TEM, EDX, BET-BJH, FTIR, DRS, PL, pHpzc, and VSM were performed to evaluate the structural, chemical and optical properties of the prepared samples. For example, BET-BJH analysis results showed that bare MgAl2O4 had low specific surface area, pore volume and pore diameter that they would impede the entry and absorption of dye molecules. While MgAl2O4(90)-AC(10)(Mag) sample, due to the presence of carbon active had high specific surface area, large pore volume and pore diameter. Also, DRS analysis represented that MgAl2O4(90)-AC(10)(Mag) had narrower band gap energy compared to bare MgAl2O4. PL analysis results also revealed the decreased recombination rate of the excited electron-hole pairs in MgAl2O4(90)-AC(10)(Mag), due to the presence of activated carbon. Moreover, the prepared samples were examined in the solar-light-driven degradation of organic dyes. The tremendous enhanced photocatalytic activity under the simulated solar light with 96% removal of MB was observed over MgAl2O4(90)-AC(10)(Mag). It also degraded 80 and 70% of EY and AO7, respectively, indicating its ability to the removal of a wide range of organic dyes. Then, the effect of initial solution pH as one of the important factors on photocatalytic activity, the reusability of the best sample and its reaction kinetic were investigated. At last, MB degradation mechanism over MgAl2O4(90)-AC(10)(Mag) was proposed.

Sono-solvothermal decoration of pore size controlled SAPO-34 by nano-ceria for green fuel production via esterification reaction

In this research, the SAPO-34 nanocatalyst has been improved in order to produce biodiesel as a green fuel. According to large molecules of free fatty acids (FFAs) and difficulty in the diffusion of these molecules through small pores of SAPO-34, the active charcoal secondary template was used to create meso and macro pores. Also, in order to increase acidic strength and density of active sites, CeO2 particles were accommodated to the structure of mesopores SAPO-34 by sono-solvothermal treatment and using ultrasound irradiation powers of 0, 100, 200 and 300 W. The synthesized catalysts were evaluated by FESEM, FTIR, TPD-NH3, HRTEM, XRD, and BET-BJH analyses. Results of characterization and reactor tests indicate that increasing the ultrasound irradiation power from 0 to 300 W in the synthesis stage has a significant effect on improving nanocatalysts properties and their performance in producing biodiesel, such that the conversion percentage in esterification reaction increased from 77 to 94%. The BET analysis showed, firstly, that using active charcoal leads to an increase of mean pore diameter of SAPO-34 from 0.5 to 3.4 nm, and secondly, that by using ultrasound irradiation power of up to 300 W, the pore volume in meso and macro range increases by 2.5 times. Results of the reactor test for the Ce/MSAPO-34 catalyst revealed that increasing the temperature, reaction time, and mole ratio of methanol to oil leads to an increase in conversion of oleic acid to biodiesel. Studying the kinetics of esterification reaction showed that using ultrasound irradiation powers of 100, 200, and 300 W increased the reaction rate by 20%, 30%, and 40%, respectively.

Sono-enhanced dispersion of CaO over Zr-Doped MCM-41 bifunctional nanocatalyst with various Si/Zr ratios for conversion of waste cooking oil to biodiesel

In present work, the catalytic properties of MCM-41 were boosted by introducing Zr into its structure with various amounts of Si/Zr molar ratios. Then it was loaded by calcium through conventional impregnation and sono-dispersion. Synthesized nanocatalysts were analysed using EDX, XRD, FTIR, FESEM and BET-BJH techniques. The results of XRD technique revealed the fabrication of MCM-41 and CaO. The FESEM images proved that the surface particle sizes of the synthesized catalysts were in the range of nanoscale and EDX results represented that Ca was more effectively scattered over the support in sonicated samples compared to non-sonicated one. Also, both FESEM and BET-BJH analysis represented a decrease in MCM-41 specific surface area with Si/Zr molar ratio reduction. The catalytic performances of bifunctional samples were evaluated for transesterification and esterification reactions. The constant operational conditions were as follows: 70 °C, MeOH/Oil = 9 and 5 wt% catalyst. Generally, the obtained results demonstrated a remarkable improvement in biodiesel conversion due to an increase of Zr amounts in catalysts and also the sample which was exposed to ultrasound represented better reusability in comparison with the non-sonicated sample. Among the prepared samples, the sonicated Ca/ZM-U (Si/Zr = 10) sample was the best catalyst for biodiesel production with high reusability.

Near room temperature synthesis of rGO-Fe3O4 nanosheets: Structural, magnetic ordering, charge transport, dye degradation properties and hydrogen evolution reaction

Abstract Reduced graphene oxide (rGO)-Fe3O4 nanosheets were synthesized at near room temperature stirring method. X-ray diffraction results showed the formation of Spinel structure of Fe3O4 with a broad diffraction pattern of reduced graphene oxide sheets. Vibrating sample magnetometery was employed to investigate the superparamagnetic behavior of Fe3O4 nanoparticles decorating rGO sheets. The estimated size of superparamagnets obtained 11 nm which was in well in agreement with XRD analysis (14 nm) and FESEM images (13 nm). A new splitting feature in high magnetic files were observed in the hysteresis curve of samples. A dipole-dipole magnetic interaction was employed to estimate the interparticle separation for the first time. The results obtained roughly 3 nm which was in good agreement with the results mean pore diameter from BET-BJH analyses. The effective surface area was obtained 97 m2 g−1 and 20 m2 g−1 for Fe3O4 and rGO-Fe3O4, respectively. Cyclic voltamettery and impedance spectroscopy revealed the significant enhancement of charge transfer for rGO-Fe3O4 hybrid nanosheets. The polarized light off-on measurement obtained a net current of 0.05 mA cm−2 which is comparable to metal chalcogenide nanostructures. Linear sweep voltamettery and corresponding Tafel plot analysis revealed an exchange current density of 210 μA cm−2 and Tafel slope of 100 mV decade−1 for rGO-Fe3O4 optimized sample. Moreover, it showed a superior methylene blue degradation of 98% and pseudo-linear degradation rate constant of 78 × 10−3min−1 which is much higher than the value of 27 × 10−3 min−1 for Fe3O4 nanoparticles. Cyclic photocatalyst activity of rGO-Fe3O4 demonstrates only 3% degradation of its performance after 5 cycles.

Effects of Reynolds and Froude dimensionless numbers on geometry of silica powders: simultaneous optimization using overall evaluation criteria technique

Specific surface area, mean pore diameter, and pore volume are among the most important geometrical properties, which can be controlled by the sol-gel mixing parameters during the silica synthesis. In this paper, these geometrical parameters were simultaneously optimized by overall evaluation criteria (OEC) technique in the Taguchi method. The optimum conditions were obtained at Reynolds dimensionless number (Re) of 250,000, Froude dimensionless number (Fr) of 0.034, acid dripping time (θ) of 60 min and acid normality (N) of 8, which resulted in BET specific surface area, BJH pore diameter and pore volume of 473.12 m2g−1, 5.21 nm, and 0.861 m3g−1, respectively. Analysis of variance demonstrated that only Re had a significant effect on the OEC values with 76.3% of contribution. The samples were characterized by SEM, BET–BJH analyses. Morphological observations confirmed the considerable effects of N, Re, and Fr on geometrical properties such as particle shapes, N2 adsorption–desorption isotherms and pore size distribution.

Modified Overlapping Grain Size Distributed Model for the Kinetic Study of CO2 Capture by a Synthetic Calcium-Based Sorbent: Structural Changes from the Chemical Reaction and Sintering

In this study, an overlapping grain size distributed model (OGSDM) was proposed to investigate the kinetics of carbonation by CO2 of a synthetic zirconia-stabilized Ca-based sorbent composed of 10 wt % ZrO2 and 90 wt % CaO in the subsequent calcium-looping cycle. In the OGSDM, the synthesized calcium-based particle consisted of initial numerous nonuniform spherical grains, which were allowed to overlap. The initial size distribution of grains was obtained through the pore-to-sphere factor method using BET–BJH analysis data. The OGSDM was improved by considering a variable diffusion coefficient of the gaseous reactant through the development of the product layer as a function of overall conversion. Mathematical modeling using the grain size distributed model (GSDM) and the OGSDM was used to calculate the overall conversion over the reaction time. It was found that the assumption of overlapping spherical grains improved the ability of the grain model in the kinetic study of the gas–solid reactions. Profiles...

Synergistic effect of ascorbic acid on the synthesis of mesoporous rGO-MoS2(100) nanocomposites and promotion of hydrogen evolution reaction

Abstract We report a new method for the preparation of MoS2 (100)-reduced graphene oxide (rGO) nanocomposites for enhancement of HER. Ascorbic acid synergistically is applied to reduce graphene oxide and controls the sulfur content of MoS2 resulted in texturing of MoS2 (100) by up taking sulfur and proposing Mo(VI) oxidation state. Variety of characterization were performed to support this hypothesis including XRD, FESEM, TEM, EDX elemental mapping, XPS, Raman, FT-IR and UV–Vis spectroscopies, TGA and BET-BJH analyses. By incorporating ascorbic acid in the synthesis process, the atomic ratio of S Mo is 0.02 for rGO-Mo(VI)S2 hybrid structure with quenched (002) Bragg diffraction peak. rGO-MoS2 shows a net 0.08 mA cm−2 polarized photocurrent in light off-on measurement. A Tafel slope of 44 mV.dec−1, an exchange current of 0.62 mA cm−2, over potential of 156 mV 10 mA cm−2 and onset potential of 25 mV was obtained. This report opens a new pass way in simple and cheap preparation of controlled defective MoS2-rGO structures with new crystal growth (100) of MoS2 for enhanced Hydrogen Evolution Reaction using ascorbic acid. Mechanisms for the role of ascorbic acid on the formation of such defective structure as well as the process of enhancement of HER have been suggested.

A glassy carbon electrode modified with TiO2(200)-rGO hybrid nanosheets for aptamer based impedimetric determination of the prostate specific antigen.

TiO2(200)-rGO hybrid nanosheets were synthesized starting from TiO2, rGO and NaOH solid powders via a scalable hydrothermal process. The weight ratio of TiO2-GO was found to be crucial on the crystal growth and biosensor properties of the final hybrid nanosheets. They were characterized by means of SEM, FESEM-EDX, XRD, XPS, Raman and FTIR spectroscopies in order to verify the formation of very thin TiO2 anatase nanosheets with an orientation of the anatase crystal structure towards the (200) plane. The free active sites of TiO2 structure and the large surface of the 2D graphene structure strongly facilitate charge transport confirmed by BET-BJH analyses. Compared to pure AuNPs, rGO and TiO2, the hybrid nanosheet modified electrode represents the most sensitive aptasensing platform for the determination of PSA. The detection was based on that the variation of electron transfer resistance (Rct) at the modified electrode surface in a solution containing 3.0mmolL-1 [Fe(CN)6]3-/4- as a redox probe and 0.1molL-1 KCl as supporting electrolyte. The detection limit of the sensor is 1pgmL-1, and the sensor can be operated up to 30days. It was applied to the analysis of PSA levels in spiked serum samples obtained from patients with prostate cancer. Data compare well with those obtained by an immunoradiometric assay. Graphical abstract Scalable reduced graphene oxide (rGO)-TiO2(200) mesoporous hybrid nanosheets with large surface area and new crystal growth of anatase (A) are introduced as efficient, durable, selective with low detection limit aptamer based prostate specific antigen biosensor.

Cr doped MCM-41 nanocomposites: an efficient mesoporous catalyst facilitating conversion of toluene to benzaldehyde, an industrial precursor

In this study, toluene, a hazardous organic compound is being converted to benzaldehyde, which has wide applications in food and dye industries. In order to achieve better conversion efficiency, Cr incorporated MCM-41 systems were used. The incorporated systems were synthesized via in situ and wet impregnation methods. The obtained samples have been characterized by Fourier Transform Infra-red, Small angle X-ray Diffraction, Wide angle X-ray diffraction, Scanning Electron Microscopy and UV–Vis Spectroscopy. FTIR spectroscopy showed the bond characteristics in the prepared nanocomposites. X-ray diffraction (XRD) pattern and UV–Visible spectra showed the presence of Cr in MCM-41 framework. Nuclear Magnetic Resonance (NMR) confirmed the conversion of toluene to benzaldehyde. Pore volume and average pore diameter (BET-BJH analysis) was estimated using Surface Area Analyzer. 97.19% conversion of toluene to benzaldehyde was achieved in 18 h using Cr-MCM-41 synthesized via in situ method having Cr/Si ratio as 0.033 as compared to Chromium oxide nanoparticles which took 36 h for 85.2% conversion. The Cr-MCM-41 prepared by wet impregnation method also showed 95% toulene to benzaldehyde conversion, but the time taken by reaction was 36 h.

Magnetic and reusable MgO/MgFe2O4 nanocatalyst for biodiesel production from sunflower oil: Influence of fuel ratio in combustion synthesis on catalytic properties and performance

The successful synthesis of magnetic MgO/MgFe2O4 nanocatalyst via combustion method was achieved that has far less time and cost than the other methods. This catalyst was used in biodiesel production reaction from vegetable oil. By changing the fuel to nitrates ratio, proper structure of catalyst was obtained to produce biodiesel. Physiochemical analysis including XRD, FESEM, EDX dot-mapping, BET-BJH, FTIR and Surface Particle Size Distribution (SPSD) were used to define the characteristics of synthesized catalysts and optimum fuel ratio in combustion synthesis method. To evaluate the performance of the synthesized nanoceramics, all samples were used in the biodiesel production reaction. The results of XRD analyses showed the successful synthesis of MgFe2O4 crystals and also determined that other materials peaks (iron oxide phases) does not exist in the catalyst structure. BET-BJH analyses reveal the structures with large pore (more than 10 nm) and relatively good surface area (97.8 m2/g) for synthesized catalysts by combustion method. By biodiesel production reaction in the conditions of temperature = 110 °C, methanol-to-oil molar ratio = 12, catalyst concentration = 4 wt.% and reaction time = 4 h, it was found that the catalyst has great potential to produce biodiesel and also maximum conversion of 91.2% was obtained. For the stability test of catalyst, after convenient catalyst separation by magnet, it was used for five consecutive transesterification reactions that the results were very acceptable and finally the lowest conversion was achieved to be 82.4%. By the simultaneous consideration of analyses and reactor tests results, it was found that synthesized catalyst with fuel ratio of 1.5 has the best performance and it is very suitable for biodiesel production reaction.