Iron oxide on carbon‐based supports as efficient catalysts for organic compounds oxidation

For the first time, iron oxide on carbon aerogel, amine functionalized carbon nanotube, black carbon and carboxylic acid functionalized carbon nanotube in the presence of H₂O₂ was reported as an efficient and stable catalyst for the selective oxidation of sulfides and alcohols. The catalysts were characterized by scanning electron microscopy, energy‐dispersive spectroscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. In the next step, catalytic reactivity toward sulfide to sulfoxide and alcohol to aldehyde/ketone oxidation in the presence of H₂O₂ was studied and discussed.     

Synthesis of a novel and reusable biological urea based acidic nanomagnetic catalyst: Application for the synthesis of 2‐amino‐3‐cyano pyridines via cooperative vinylogous anomeric based oxidation

In the current study, a novel and reusable biological urea based nano magnetic catalyst namely Fe₃O₄@SiO₂@(CH₂)₃‐urea‐benzimidazole sulfonic acid was designed and synthesized. The structure of the titled catalyst was fully characterized using several skills including Fourier transform infrared (FT‐IR) spectroscopy, energy dispersive X‐ray (EDX) analysis, X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo gravimetric analysis/differential thermal analysis (TG/DTG) and vibrating sample magnetometer (VSM). Then, the catalytic performance of Fe₃O₄@SiO₂@(CH₂)₃‐urea‐benzimidazole sulfonic acid was successfully inspected towards the multicomponent synthesis of 2‐amino‐3‐cyano pyridine derivatives through a vinylogous anomeric based oxidation pathway.     

Structure‐activity relationship of supported Au catalysts with high catalytic activity by modifying the inactive supports

Three supported Au catalysts have been prepared by the deposition‐precipitation method by using the active carbon (AC), SiO₂‐AC, and SiO₂‐AC‐hollowed. The 3 supports were characterized by Brunauer‐Emmett‐Teller and scanning electron microscopy. Meanwhile, the supported Au nanoparticles were also characterized in detail by X‐ray powder diffraction, transmission electron microscopy, H₂‐TRP, and X‐ray photoelectron spectroscopy, and their catalytic activity and stability in CO oxidation was evaluated. The results demonstrated that Au supported on SiO₂‐AC‐hollowed exhibited much higher catalytic activity with acceptable stability for 72 hours than the other 2. We attributed to finer supported Au nanoparticles with abundant low‐coordinated Au atoms on the surfaces of hollowed supports with large special surface area and abundant pore structure. In summary, we successfully found an efficient and cheap method to prepare catalysts with high catalytic activity and acceptable stability by modifying the inactive supports.     

Synthesis,characterization and application of nano‐CoAl2O4 as an efficient catalyst in the preparation of hexahydroquinolines

In this work, nano‐CoAl₂O₄ was prepared and characterized by FT‐IR, energy dispersive X‐ray analysis (EDX), X‐ray diffraction patterns (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and transmission electron microscopy (TEM). Nano‐CoAl₂O₄ was applied for the synthesis of hexahydroquinoline derivatives by the condensation reaction between ethyl acetoacetate, dimedone and various aldehydes. These reactions were carried out at 80 °C under solvent‐free conditions.     

MgBr2 supported on Fe3O4@SiO2 ~ urea nanoparticle: An efficient catalyst for ortho‐formylation of phenols and oxidation of benzylic alcohols

Urea was successfully immobilized on the surface of chloropropyl‐modified Fe₃O₄@SiO₂ core–shell magnetic nanoparticles, then supported by MgBr₂ and acts as a unique catalyst for oxidation of benzylic alcohols to aldehydes and ketones, and ortho‐formylation of phenols to salicylaldehydes. The prepared catalyst was characterized by FT‐IR, transmission electron microscopy, scanning electron microscopy, X‐ray powder diffraction, dispersive X‐ray spectroscopy, CHN and TGA. It was found that Fe₃O₄@SiO₂ ~ urea/MgBr₂ showed higher catalytic activity than homogenous MgBr₂, and could be reused several times without significant loss of activity.     

Synthesis of Bi-doped TiO2 Nanotubes and Enhanced Photocatalytic Activity for Hydrogen Evolution from Glycerol Solution

Bi‐doped TiO₂ nanotubes with variable Bi/Ti ratios were synthesized by hydrothermal treatment in 10 mol·L^?1 NaOH (aq.) through using Bi‐doped TiO₂ particles derived from conventional sol‐gel method as starting materials. The effects of Bi content on the morphology, textural properties, photo absorption and photocatalytic activity of TiO₂ nanotubes were investigated. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) observations of the obtained samples revealed the formation of titanate nanotube structure doped with Bi, which exists as a higher oxidation state than Bi³⁺. Bi‐doping TiO₂ nanotubes exhibited an extension of light absorption into the visible region and improved photocatalytic activities for hydrogen production from a glycerol/water mixed solution as compared with pure TiO₂ nanotubes. There was an optimal Bi‐doped content for the photocatalytic hydrogen production, and high content of Bi would retard the phase transition of titanate to anatase and result in morphology change from nanotube to nanobelt, which in turn decreases the photocatlytic activity for hydrogen evolution.     

Oxidation of ethylbenzene to styrene oxide in the presence of cellulose‐supported Pd magnetic nanoparticles

Palladium and Fe₃O₄ nanoparticles were deposited on N‐(2‐aminoethyl)acetamide‐functionalized cellulose for use in a catalytic reaction. The catalyst was characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, energy‐dispersive X‐ray analysis and transmission electron microscopy, and applied in the oxidation reaction of ethylbenzene at 100 °C using H₂O₂. Styrene oxide was obtained as the sole product of the oxidation reaction during 24 h. This reaction has some advantages such as one‐pot transformation of ethylbenzene to styrene oxide, high yield, excellent selectivity and magnetically recoverable catalyst. Also, the recovered catalyst could be used in the oxidation reaction four times without decrease in yield. Copyright © 2016 John Wiley & Sons, Ltd.     

Spinel copper ferrite nanoparticles: Preparation,characterization and catalytic activity

The magnetic CuFe₂O₄ nanoparticles have been synthesized and characterized by various spectroscopic methods, including X‐ray diffraction (XRD), O K, Cu and Fe K ‐edge X‐ray absorption near edge structure (XANES), energy dispersive X‐ray analysis (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The azide‐alkyne cycloaddition by the reaction of various phenylacetylenes with a mixture of benzyl halides and NaN₃ and also three component (A³) coupling reaction of aldehyde, alkyne and amine catalyzed by CuFe₂O₄ nanoparticles under aerobic conditions led to the formation of the 1,4‐disubstituted‐1,2,3‐triazoles and propargylamines in excellent yields. The catalyst can be recovered by applying an external magnetic field for the subsequent cycloaddition reactions and reused without any tangible loss in catalytic efficiency.     

Synthesis,Characterization, and Photocatalytic Activity of N‐Doped TiO2 Nanotubes

N‐doped TiO₂ nanotubes with high photocatalytic activity were prepared by the combination of sol‐gel process with hydrothermal treatment. The prepared materials are characterized with transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), x‐ray diffraction (XRD), x‐ray photoelectron spectra (XPS), and UV‐vis spectra. Photocatalytic performance of the N‐doped TiO₂ nanotubes is studied by testing the degradation rate of methyl orange under UV irradiation. Obtained results indicate that N‐doped TiO₂ nanotubes have high catalytic activity for photocatalytic oxidation.     

Controllable preparation of highly dispersed TiO2 nanoparticles for enhanced catalytic oxidation of dibenzothiophene in fuels

The aggregation of nanoparticle catalysts is one of the main problems in catalytic reactions. In this study, a series of TiO₂ nanoparticle catalysts with various dispersions were prepared and applied in the catalytic oxidation of dibenzothiophene (DBT) systems. Compositions and structures of the as‐prepared samples were analyzed by means of wide‐angle X‐ray diffraction, Raman and X‐ray photoelectron spectroscopies. The dispersions of TiO₂ nanoparticles were controlled by calcining at various temperatures and verified using transmission electron microscopy. It was found that the activities of TiO₂ nanoparticles in the catalytic oxidation of DBT were positively correlated with the dispersions. TiO₂ nanoparticles calcined at 500 °C (500‐TiO₂) showed the best catalytic activity and the oxidation of DBT reached 99.8% under mild conditions. Based on the results of GC–MS analysis, radical trapping experiments and electron spin resonance spectra, ^?O₂^? radicals were proved to be the main active species in the oxidation process, and a mechanism is proposed. Meanwhile, the recycling performance of 500‐TiO₂ was investigated, and no obvious decrease was observed after six recycles.     

Palladium nanoparticles supported on modified hollow Fe3O4@TiO2: Preparation,characterization, and catalytic activity in Suzuki cross‐coupling reactions

Hollow Fe₃O₄@TiO₂‐NH₂/Pd as a light‐weight, magnetically heterogeneous catalyst was successfully prepared, and characterized by using different techniques including X‐ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDX), vibrating sample magnetometer (VSM) measurements, and thermogravimetric analysis (TGA). Then this heterogeneous catalyst was tested in the Suzuki cross‐coupling reaction, and the results confirmed the success of this method. The catalyst could be separated easily using an external magnet and reused at least in five runs successfully without any appreciable loss in its catalytic activity.     

Preparation of 1,2,4,5‐tetrasubstituted imidazoles over magnetic core–shell titanium dioxide nanoparticles

Magnetic core–shell titanium dioxide nanoparticles (Fe₃O₄@SiO₂@TiO₂) were applied for the efficient preparation of 1,2,4,5‐tetrasubstituted imidazole derivatives by the one‐pot multi‐component condensation of benzil with aldehydes, primary amines and ammonium acetate under solvent‐free conditions. The catalyst was synthesized and studied using several techniques including X‐ray diffraction, transmission electron microscopy, field‐emission scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.     

Diesel Soot Combustion over Mn2O3 Catalysts with Different Morphologies: Elucidating the Role of Active Oxygen Species in Soot Combustion

Catalytic diesel soot combustion was examined using a series of Mn₂O₃ catalysts with different morphologies, including plate, prism, hollow spheres and powders. The plate‐shaped Mn₂O₃ (Mn₂O₃‐plate) exhibited superior carbon soot combustion activity compared to the prism‐shaped, hollow‐structured and powdery Mn₂O₃ under both tight and loose contact modes at soot combustion temperatures (T₅₀) of 327 °C and 457 °C, respectively. Comprehensive characterization studies using scanning electron microscopy, scanning transmission electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, temperature‐programmed reduction and oxygen release measurements, revealed that the improved activity of Mn₂O₃‐plate was mainly attributed to the high oxygen release rate of surface‐adsorbed active oxygen species, which originated from oxygen vacancy sites introduced during the catalyst preparation, rather than specific surface‐exposed planes. The study provides new insights for the design and synthesis of efficient oxidation catalysts for carbon soot combustion as well as for other oxidation reactions of harmful hydrocarbon compounds.     

Formation of CaCO3 deposits on OMS‐2 surface to synergistically promote peroxymonosulfate activation and organic dyes degradation

The development of green and efficient catalysts for peroxymonosulfate (PMS) activation and organic pollutants degradation has received widespread attention. In this study, the hybrid CaCO₃/OMS‐2 catalysts were prepared by a simple precipitation approach and characterized by X‐ray powder diffraction, N₂ adsorption–desorption, scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy and cyclic voltammetry. It was found that deposition of CaCO₃ on OMS‐2 surface can weaken the Mn‐O bond by formation of Ca‐O‐Mn bond. The interactions between CaCO₃ and OMS‐2 significantly enhanced Acid Orange 7 degradation in the presence of PMS with a pseudo‐first‐order kinetic constant of 0.21 min^?1, which was much higher than those of OMS‐2 (0.026 min^?1) and CaCO₃ (0.021 min^?1). The CaCO₃/OMS catalysts were also much more efficient than other reported OMS‐2 hybrid catalysts, and could be performed over a wide solution pH and for other organic dyes degradation. Sulfate and hydroxyl radicals were formed from the oxidation of low valent manganese species by PMS as the active species in the system. This study can provide a simple method for the design of efficient manganese‐based hybrids for wastewater remediation via PMS activation.     

Synthesis and Characterization of SnO2 One-dimensional Nanostructures

Single-crystalline SnO2 nanowires have been successfully prepared in large scale on Au-coated silicon substrate by heating the mixture of self-made high-purity SnO2 powders and graphite powders at 900℃. Besides the line type nanowires some more features were observed. The products were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and Raman spectrum techniques. The results indicate that the tin dioxide nanowires have a rutile structure with diameters ranging from 30 to 120 nm and lengths up to several tens of micrometers. The possible mechanism of the growth and reaction for the nanowires was also discussed.     

Nanocomposite with Polypyrrole Encapsulated within SBA‐15 Mesoporous Silica: Preparation and Its Electrochemical Application

The nanocomposite with polypyrrole (PPy) confined in ordered mesoporous silica SBA‐15 channels was synthesized by in situ electropolymerization. X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, N₂ adsorption/desorption, and FT‐IR studies indicated that the nanocomposite has the well‐ordered hexagonal structures and PPy was in situ polymerized into the channels instead of the outer surface of SBA‐15. Furthermore, the PPy/SBA‐15 nanocomposite was used as an electrode modifier. We found that the nanocomposite‐modified electrode exhibited good electrocatalytic activities for hydroquinone oxidation where PPy chains could facilitate the electron transfer between molecular sieves and electrode surface. Three dihydroxybenzene isomers (hydroquinone, catechol and resorcinol) have been successfully detected at PPy/SBA‐15 modified electrode by preconcentration of the analyte.     

Synthesis of Ag Nanoparticle Doped MnO2/GO Nanocomposites at a Gas/Liquid Interface and its Application in H2O2 Detection

Ag/MnO₂/GO nanocomposites were synthesized via the method of gas/liquid interface based on silver mirror reaction, and a non‐enzymatic H₂O₂ sensor was fabricated through immobilizing Ag/MnO₂/GO nanocomposites on GCE. The composition and morphology of the nanocomposites were studied by energy‐dispersive X‐ray spectroscopy (EDS), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Electrochemical investigation indicated that it exhibited a favorable performance for the H₂O₂ detection. Its linear detection range was from 3 μM to 7 mM with a correlation coefficient of 0.9960; the sensitivity was 105.40 μA mM^?1 cm^?2 and the detection limit was estimated to be 0.7 μM at a signal‐to‐noise ratio of 3.     

Biosynthesis of Pd/MnO2 nanocomposite using Solanum melongena plant extract and its application for the one‐pot synthesis of 5‐substituted 1H‐tetrazoles from aryl halides

In this work, for the first time, Solanum melongena plant extract was used for the green synthesis of Pd/MnO₂ nanocomposite via reduction osf Pd(II) ions to Pd(0) and their immobilization on the surface of manganese dioxide (MnO₂) nanoparticles (NPs) as an effective support. The synthesized nanocomposite were characterized by various analytical techniques such as Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray spectroscopy (EDS) and UV–Vis spectroscopy. The catalytic activity of Pd/MnO₂ nanocomposite was used as a heterogeneous catalyst for the one‐pot synthesis of 5‐substituted 1H‐tetrazoles from aryl halides containing various electron‐donating or electron‐withdrawing groups in the presence of K ₄ [Fe (CN) ₆ ] as non‐toxic cyanide source and sodium azide. The products were obtained in good yields via a simple methodology and easy work‐up. The nanocatalyst can be recycled and reused several times with no remarkable loss of activity.     

Facile Electrospinning of CeO2/Bi2WO6 Heterostructured Nanofibers with Excellent Visible‐light‐driven Photocatalytic Performance

One‐dimensional (1D) CeO₂/Bi₂WO₆ heterostructured nanofibers with a diameter of about 300 nm were successfully synthesized by using a straightforward strategy combining an electrospinning technique with a sintering process. The acquired products were characterized by thermogravimetric and differential scanning calorimetric (TG‐DSC), Fourier transform infrared (FT‐IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area measurements, and UV/Vis spectroscopy. The obtained CeO₂/Bi₂WO₆ heterostructured nanofibers exhibited an excellent photocatalytic property for the degradation of Rhodamine B (RhB) dye driven by visible light due to the promoted separation of photoelectrons and holes and the large contact area between the photocatalyst and organic pollutant.     

Development of Quercetin Biosensor Through Immobilizing Laccase in a Modified β‐Cyclodextrin Matrix Containing Ag Nanoparticles in Ionic Liquid

A biosensor containing Ag nanoparticles in ionic liquid (IL) 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI.Tf₂N) and laccase (Lac) immobilized on β‐cyclodextrin modified with epichlorohydrin (β‐CDEpi) was developed for quercetin determination. Lac catalyses the oxidation of quercetin to quinone, which is then reduced on the biosensor surface and the resulting current was investigated by square‐wave voltammetry. The β‐CDEpi support was analyzed by scanning electron microscopy and Ag‐BMI.Tf₂N by transmission electron microscopy and X‐ray diffraction. The linear range (0.499–7.407 μM) and low detection limit (0.037±0.004 μM) show that the proposed biosensor is suitable for quercetin determination in real samples.