Strong metal-support interactions between gold nanoparticles and ZnO nanorods in CO oxidation

The catalytic performances of supported gold nanoparticles depend critically on the nature of support. Here, we report the first evidence of strong metal-support interactions (SMSI) between gold nanoparticles and ZnO nanorods based on results of structural and spectroscopic characterization. The catalyst shows encapsulation of gold nanoparticles by ZnO and the electron transfer between gold and the support. Detailed characterizations of the interaction between Au nanoparticles and ZnO were done with transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), electron paramagnetic resonance (EPR), and FTIR study of adsorbed CO. The significance of the SMSI effect is further investigated by probing the efficiency of CO oxidation over the Au/ZnO-nanorod. In contrast to the classical reductive SMSI in the TiO(2) supported group VIII metals which appears after high temperature reduction in H(2) with electron transfer from the support to metals, the oxidative SMSI in Au/ZnO-nanorod system gives oxygen-induced burial and electron transfer from gold to support. In CO oxidation, we found that the oxidative SMSI state is associated with positively charged gold nanoparticles with strong effect on its catalytic activity before and after encapsulation. The oxidative SMSI can be reversed by hydrogen treatment to induce AuZn alloy formation, de-encapsulation, and electron transfer from support to Au. Our discovery of the SMSI effects in Au/ZnO nanorods gives new understandings of the interaction between gold and support and provides new way to control the interaction between gold and the support as well as catalytic activity.     

Thermoresponsive hydrogel of poly(glycidyl methacrylate‐co‐N‐isopropylacrylamide) as a nanoreactor of gold nanoparticles

The synthesis of a thermoresponsive hydrogel of poly(glycidyl methacrylate‐co‐N‐isopropylacrylamide) (PGMA‐co‐PNIPAM) and its application as a nanoreactor of gold nanoparticles are studied. The thermoresponsive copolymer of PGMA‐co‐PNIPAM is first synthesized by the copolymerization of glycidyl methacrylate and N‐isopropylacrylamide using 2,2′‐azobis(isobutyronitrile) as an initiator in tetrahydrofuran at 70 °C and then crosslinked with diethylenetriamine to form a thermoresponsive hydrogel. The lower critical solution temperature (LCST) of the thermoresponsive hydrogel is about 50 °C. The hydrogel exists as 280‐nm spheres below the LCST. The diameter of the spherical hydrogel gradually decreases to a minimum constant of 113 nm when the temperature increases to 75 °C. The hydrogel can act as a nanoreactor of gold nanoparticles because of the coordination of nitrogen atoms of the crosslinker with gold ions, on which a hydrogel/gold nanocomposite is synthesized. The LCST of the resultant hydrogel/gold nanocomposite is similar to that of the hydrogel. The size of the resultant gold nanoparticles is about 15 nm. The hydrogel/gold nanocomposite can act as a smart and recyclable catalyst. At a temperature below the LCST, the thermoresponsive nanocomposite is a homogeneous and efficient catalyst, whereas at a temperature above the LCST, it becomes a heterogeneous one, and its catalytic activity greatly decreases. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2812–2819, 2007     

Synthesis of acetamides via oxidative C–C bond cleavage of ketones catalyzed by Cu-immobilized magnetic nanoparticles

Copper supported on magnetite nanoparticles modified with environmentally friendly ligand tricine was devised for synthesis of acetamides via C–C oxidative cleavage of ketones with amines. The catalyst was characterized using different techniques, including Fourier transform infrared, X-ray diffraction, scannin electron microscopy, vibrating sample magnetometry, thermogravimetric analysis, and energy dispersive x-ray spectroscopy. The protocol showed relatively high yields of acetamide products. Furthermore, the magnetic recovery of the catalyst rendered the overall process fast and efficient. It was used in the reaction for six consecutive cycles with negligible loss of catalytic activity. This research is the first report of application of magnetic nanocatalysts for synthesis of acetamides from ketones of low activity through a C–C bond cleavage strategy.     

绿色可磁性分离二氧化硅包裹镍铁尖晶石负载硫酸氢铁纳米粒子催化剂用于合成1,8-二氧十氢吖啶合成Amir Khojastehnezhad,Mohammad Rahimizadeh,简

A new magnetically separable catalyst consisting of ferric hydrogen sulfate supported on silica-coated nickel ferrite nanoparticles was prepared. The synthesized catalyst was characterized using vibrating sample magnetometry, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. This new magnetic catalyst was shown to be an efficient heterogeneous catalyst for the synthesis of 1,8-dioxodecahydroacridines under solvent-free conditions. The catalyst is readily recovered by simple magnetic decantation and can be recycled several times with no significant loss of catalytic activity.     

Selective oxidation of sulfurs and oxidation desulfurization of model oil by 12-tungstophosphoric acid on cobalt-ferrite nanoparticles as magnetically recoverable catalyst

Silica-coated CoFe2O4 nanoparticles were prepared and used as a support for the immobilization of 12-tungstophosphoric acid, to produce a new magnetically separable catalyst. This catalyst was characterized using X-ray diffraction, wavelength-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, laser par-ticle size analysis, and vibrating sample magnetometry. The catalyst showed high activity in the selective oxidation of thioethers and thiophenes to the corresponding sulfones under mild condi-tions. The catalytic activity of the nanocatalyst in the oxidative desulfurization of model oil was investigated. The effect of nitrogen-containing compounds on sulfur removal from the model oil was also evaluated. The catalyst showed high activity in the oxidative desulfurization of diesel. The cata-lyst can be readily isolated from the oxidation system using an external magnet and no obvious loss of activity was observed when the catalyst was reused in four consecutive runs.     

Radiation synthesis of copper sulphide/poly(vinyl alcohol) nanocomposites films: an efficient and reusable catalyst for p-nitrophenol reduction

ABSTRACT

Copper sulphide nanoparticles (CuS NPs) were in situ synthesised via irradiation process, using Poly (vinyl alcohol) (PVA) as host polymeric matrices. The as-prepared CuS/PVA nanocomposite films were characterised by X-ray diffraction (XRD) spectroscopy, ultraviolet-visible (UV-VIS) spectroscopy, Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Both UV-VIS spectra and X-ray diffraction patterns confirmed the formation of CuS nanoparticles. The FTIR spectrum indicates the coordination between CuS nanoparticles and the OH groups of the PVA chains. The TEM image showed that the obtained CuS nanoparticles have spherical shape, monodispersed and uniform particle size distribution. The CuS/PVA nanocomposite film was successfully applied in the reduction of p-nitrophenol into p-aminophenol as a catalyst using NaBH₄ as reducing agent. The catalytic test indicates that CuS/PVA nanocomposite film has high activity for the conversion of P-NP into P-AP and effectively recycled and reused for several times.     

无溶剂条件下磷酸锆纳米粒子作为固体酸催化剂催化苯酚选择性烷基化(英文)

A facile synthesis of α-zirconium phosphate(ZP) nanoparticles as an effective, eco-friendly, and recyclable solid acid catalyst is reported. Polyvinylpyrrolidone(PVP) and polyvinyl alcohol(PVA) were used as organic matrix as dispersing agents and served as a template for the nanoparticles. Hydrogen bonds between ZP and PVA or PVP, along the polymer chains, appear to play an important role for improving the dispersion of in situ formed ZP. Following calcination of PVA/ZP or PVP/ZP, pure hexagonal ZP nanoparticles were obtained. The catalysts were characterized by nitrogen sorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy, and transmission electron microscopy. Pyridine-FTIR and temperature-programmed desorption of NH3 suggest the presence of Brnsted acid sites. The acidic properties of the catalyst were studied in Friedel-Crafts alkylation of phenol by tert-butanol, producing 2-tert-butylphenol, 4-tert-butylphenol, and 2,4-ditert-butylphenol. The alkylation reaction was performed in the presence of catalysts P2O5/Al2O3, P2O5/SiO2, α-ZrP(prepared in the absence of the polymers), and various ionic liquids. The use of the hexagonal ZP nanoparticle catalyst afforded an excellent phenol conversion(86%) and selectivity towards 4-tert-butylphenol(83%) under optimized reaction conditions. The catalyst was easily recovered from the reaction mixture, regenerated, and reused at least four times without significant loss in the catalytic activity.     

超顺磁性介孔纳米颗粒嫁接肟Pd环络合物对Heck反应的催化活性

采用溶胶-凝胶法制备出介孔二氧化硅包裹四氧化三铁纳米复合颗粒,在其表面修饰巯基,并以此为载体通过-SCH2-化学键嫁接长链的肟钯环络合物.利用透射电镜(TEM)、高分辨透射电镜(HRTEM)、傅里叶变换红外(FT-IR)光谱、N2吸附-脱附、X光电子能谱(XPS)、振动样品磁强计(VSM)等手段对催化剂进行表征,通过Heck反应对催化剂的活性进行评价.实验结果表明:所制备的磁性颗粒直径约为150nm,比表面积为287.0m2·g-1,且具有大小为3.5nm呈不规则的孔道结构,整个催化剂呈现超顺磁性.对于碘代苯与丙烯酸乙酯之间的Heck反应,2.5h后碘代苯的转化率可达到99%,催化剂在重复使用6次后能保持很高的催化活性(碘代苯转化率为95%).催化剂可稳定分散于反应体系中,并可在外磁场作用下快速与反应体系分离.     

Sulfamic acid immobilized on amino‐functionalized magnetic nanoparticles: A new and active magnetically recoverable catalyst for the synthesis of N‐heterocyclic compounds

Sulfamic acid immobilized on amino‐functionalized magnetic nanoparticles (MNPs/DETA‐SA) was successfully fabricated and characterized using various techniques. Diameters of approximately 15 nm for the MNPs/DETA‐SA were observed from scanning electron microscopy images. The as‐fabricated nanocomposite was applied as an efficient and magnetically reusable catalyst for the synthesis of 2,3‐dihydroquinazoline‐4(1H)‐one and polyhydroquinoline derivatives. All products were obtained in good to excellent yields. Recovery tests confirm that the catalyst can be readily recovered using an external magnet and reused many times without significant loss of its catalytic activity.     

Magnetic NiFe2O4 nanoparticles: efficient,heterogeneous and reusable catalyst for synthesis of acetylferrocene chalcones and their anti‐tumour activity

A robust synthesis of magnetic NiFe₂O₄ nanoparticles via a hydrothermal technique was investigated. The prepared magnetic NiFe₂O₄ nanoparticles were characterized using powder X‐ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), high‐resolution TEM, energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, infrared spectroscopy and vibrating sample magnetometry. XRD and TEM analyses confirmed the formation of single‐phase ultrafine nickel ferrite nanoparticles with highly homogeneous cubic shape and elemental composition. Moreover, the prepared magnetic NiFe₂O₄ nanoparticles were used as an efficient, cheap and eco‐friendly catalyst for the Claisen–Schmidt condensation reaction between acetylferrocene and various aldehydes (aromatic and/or heterocyclic) yielding acetylferrocene chalcones in excellent yields, with easy work‐up and reduced reaction time. The products were purified via crystallization. The structures of the produced compounds were elucidated using various spectroscopic analyses (¹H NMR, ¹³C NMR, GC–MS). The catalyst is readily recovered by simple magnetic decantation and can be recycled several times with no discernible loss of catalytic activity. Furthermore, the prepared chalcone derivatives were evaluated for their anti‐tumour activity against three human tumour cell lines, namely HCT116 (colon cancer), MCF7 (breast cancer) and HEPG2 (liver cancer), and showed a good activity against colon cancer. Copyright © 2016 John Wiley & Sons, Ltd.     

(Triazinediyl)bis sulfamic acid-functionalized silica-coated magnetite nanoparticles: Preparation,characterization and application as an efficient catalyst for synthesis of mono-, bis-, tris- and spiro-perimidines

(Triazinediyl)bis sulfamic acid-functionalized silica-coated magnetite nanoparticles have been prepared and applicated as an efficient catalyst for synthesis of mono-, bis-, tris- and spiro-perimidines. The desired products have been synthesized in high purity and good yields. The workup procedure of reaction is simple. The catalyst was easily separated from the reaction mixture with the assistance of an external magnetic field and reused for several runs without deterioration in catalytic activity. The core/shell nanoparticles were characterized by transmission electron microscopy, scanning electron microscope, powder X-ray diffraction, energy dispersive spectrometer, Fourier transform infrared spectroscopy and vibrating sample magnetometer.     

Preparation of carbon-supported core-shell Au-Pt nanoparticles for methanol oxidation reaction: The promotional effect of the Au core

Core-shell Au-Pt nanoparticles with intimate contact of Pt and Au were prepared by a displacement reaction without formation of monometallic Au nanoparticles. The Au-Pt nanoparticles were dispersed on carbon (Au@Pt/C) and were used to catalyze methanol electrooxidation in acidic solutions at room temperature. The core-shell nanostructure was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy, and specific catalytic activities were evaluated by CO anodic stripping voltammetry in 0.5 M H(2)SO(4) and by cyclic voltammetry in 1 M CH(3)OH + 0.5 M H(2)SO(4). The Au@Pt/C catalyst demonstrated enhanced specific activity in methanol electrooxidation and showed multiple CO stripping peaks which were all negatively shifted with respect to a similarly prepared Ag@Pt/C catalyst. The activity enhancement is attributed to the presence of Au underneath a very thin Pt shell where electron exchange between Au and Pt had promoted the formation of active oxygen species on Pt, which facilitated the removal of inhibiting CO-like reaction intermediates.     

磁性纳米颗粒负载钯催化剂对Heck反应的催化活性

采用水热法合成了碳包埋磁性纳米复合颗粒C/(Au@Fe),并以之为载体制备了纳米钯催化剂,利用透射电镜、X射线光电子能谱和振动样品磁强计等手段对催化剂进行了表征,评价了催化剂对Heck反应的催化活性.结果表明,催化剂的平均粒径约为300nm,表面覆盖着一层粒径为12nm的钯颗粒,整个催化剂呈现超顺磁性.对于碘代苯与丙烯酸之间的Heck反应,在乙酸钠或三乙胺碱性条件下反应4h,碘代苯转化率可达95%以上.催化剂重复使用10次时仍可保持很高的催化活性(碘代苯转化率88%).对于其他不同反应底物之间的Heck反应,催化剂同样显示有较高的催化活性.催化剂可稳定分散于反应体系中,并可在外磁场作用下快速与反应体系分离.     

Synthesis and characterization of bromine source immobilized on diethylenetriamine‐functionalized magnetic nanoparticles: A novel,versatile and highly efficient reusable catalyst for organic synthesis

Bromine source immobilized on magnetic nanoparticles functionalized with diethylenetriamine was successfully synthesized and characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometry, thermogravimetric analysis and X‐ray diffraction. The catalytic activity in the synthesis of 2,3‐dihydroquinazoline‐4(1H )‐one and polyhydroquinoline derivatives and in Knoevenagel condensation was studied. The bromine catalyst can be magnetically recovered and reused several times without significant loss of its catalytic activity. All products were obtained in high to excellent yields.     

Synthesis and curing of poly(glycidyl methacrylate) nanoparticles

Glycidyl‐functional polymer nanoparticles [poly(glycidyl methacrylate) (PGMA)] were fabricated with microemulsion polymerization. The successful fabrication of PGMA nanoparticles was confirmed by Fourier transform infrared spectroscopy and transmission electron microscopy (TEM). A TEM image showed that the average diameter of the PGMA nanoparticles was approximately 10–28 nm and was fairly monodisperse. As the surfactant concentration increased, the average size of the nanoparticles decreased and approached an asymptotic value. A significant reduction of the nanoparticle size to the nanometer scale led to an enhanced number of surface functionalities, which played an important role in the curing reaction. The PGMA nanoparticles were cured with a low‐temperature curing agent, diethylene triamine, to produce ultrafine thermoset nanoparticles. The low‐temperature curing process was performed below the glass‐transition temperature of PGMA to prevent the coagulation and deformation of the nanoparticles. A TEM image indicated that the cured PGMA nanoparticles did not exhibit interparticle aggregation and morphological transformation during curing. The average size of the cured PGMA nanoparticles was consistent with that of the pristine PGMA nanoparticles © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2258–2265, 2005     

Fibroin-functionalized magnetic carbon nanotube as a green support for anchoring silver nanoparticles as a biocatalyst for A3 coupling reaction

Novel and powerful fibroin-functionalized magnetic carbon nanotube–supported silver nanoparticles (CNT–Fe₃O₄–fibroin–Ag) were successfully synthesized as a nontoxic and inexpensive biocatalyst. The structure of the organic–inorganic hybrid bionanocomposite was characterized by various techniques such as Fourier transform infrared spectroscopy, thermogravimetric analysis, energy-dispersive X-ray, field emission-scanning electron microscopy, transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry, atomic absorption spectroscopy, and inductively coupled plasma-optical emission spectrometry. Then, the catalytic activity of synthesized bionanocomposite was evaluated in the three-component A³ coupling reaction under solvent-free conditions with good to excellent yields. Several propargylamine derivatives were synthesized by the reaction of different aldehydes with amines and phenylacetylene. Biodegradability, biocompatibility, availability, easy synthesis, high stability, high-throughput, cost-effectiveness, and efficient magnetic separation are some advantages of this catalyst that make it economically justified and sustainable. Moreover, the catalyst can be recycled for several runs without appreciable loss in its catalytic activity.     

Constructing magnetic polyaniline/metal hybrid nanostructures using polyaniline/Fe3O4 composite hollow spheres as supports

Polyaniline (PANI)/Fe₃O₄ composite hollow spheres have been successfully synthesized in one step using sulfonated polystyrene (PS) spheres as templates. The magnetic PANI hollow spheres were used as supports for noble metal nanoparticles (NPs) such as Au and Pd. The morphology, composition and magnetic properties of the resulting products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma (ICP) atomic spectra and vibrating sample magnetometer. The catalytic activity of magnetic PANI/Au composite shells on the oxidation of dopamine was investigated by cyclic voltammetry. The obtained results provide our product with a practical application for the detection of dopamine. On the other hand, the catalytic activity of magnetic PANI/Pd composite shells on the reduction of 4-nitroaniline was investigated by spectroscopic methods and compared with Pd/C catalyst which was already widely used in industrial production.     

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.     

乳液聚合法制备纳米金/聚苯乙烯复合粒子

以氯金酸为前驱体,十二烷基硫醇和硼氢化钠分别作为稳定剂和还原剂,采用相转移法制备了单分散的金纳米粒子.将金纳米粒子通过乳液聚合的方法制备了纳米金/聚苯乙烯复合粒子.通过紫外-可见吸收光谱(UV-Vis)研究了纳米金和纳米金/聚苯乙烯复合粒子的光吸收特性,使用傅立叶变换红外光谱(FT-IR)、X射线衍射(XRD)、透射电子显微镜(TEM)和动态光散射(DLS)对产物的组成、晶体结构、形貌、以及粒径进行了表征.结果表明,复合粒子为粒径分布较窄的球形,其中的金纳米粒子为面心立方结构.热失重分析(TGA)说明制备的纳米金/聚苯乙烯复合粒子具有很好的热稳定性.     

Synthesis of graphene oxide supported copper–cobalt ferrite material functionalized by arginine amino acid as a new high–performance catalyst

A novel Cu_0.5Co_0.5Fe₂O₄@Arg–GO catalytic system was successfully prepared by immobilization of copper substituted cobalt ferrite nanoparticles on arginine–grafted graphene oxide nanosheets, in which ferrite moiety acts as an oxidation catalyst and arginine has the role of base catalyst. Also, arginine amino acid was used to modify the surface of graphene oxide nanosheets which the prepared support can improve dispersion and uniform loading of nanoparticles. The prepared nanocomposite was characterized by flame atomic absorption spectroscopy (FAAS), inductively coupled plasma optical emission spectrometer (ICP–OES), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT–IR), ultraviolet–visible spectroscopy (UV–vis), Raman spectroscopy, thermogravimetric analysis (TGA), x–ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis. The prepared Cu_0.5Co_0.5Fe₂O₄@Arg–GO nanocomposite was used as an efficient catalyst for one–pot tandem oxidative synthesis of 2–phenylbenzimidazole derivatives in good yields.