原位还原制备滤纸载纳米银粒子复合材料及其催化特性

基于绿色化学的角度,直接以滤纸(FP)为基底材料,在碱性条件下无需外加还原剂和稳定剂,原位还原得到负载纳米银(AgNPs)的AgNPs/FP复合材料。通过扫描电子显微镜(SEM)、X射线电子能谱仪(EDS)、热重分析仪(TGA)和紫外-可见(UV-vis)分光光度计等对复合材料的形貌、组成和催化性能进行表征。研究结果表明,Ag⁺被还原为AgNPs后致密又均匀地负载于滤纸表面上,所制得的AgNPs/FP复合材料中纳米银呈球形、尺寸均一且团聚较少。AgNPs/FP复合材料对对硝基苯酚(4-NP)的还原具有较好的催化活性,且易于回收再利用。     

One step green synthesis of hexagonal silver nanoparticles and their biological activity

Hexagonal and spherical silver nanoparticles were prepared by in situ and green synthesis using sun light as reducing agent with assistance newly prepared cationic surfactant which act also as capping agents. The silver nanoparticles formation was investigated using UV–vis spectrophotometer, transmission electron microscope (TEM), dynamic light scattering (DLS), energy dispersive X-ray (EDX) and FTIR. The results showed formation uniform, well arrangement hexagonal and spherical shapes. Increasing hydrophobic chain length increase the stability and amount of AgNPS. Both prepared surfactants and surfactants capping silver nanoparticles showed high antimicrobial activity against Gram-positive and Gram-negative bacteria.     

Utilization of clay minerals for developing Pt nanoparticles and their catalytic activity in the selective hydrogenation of cinnamaldehyde

Platinum sub colloids (nm range) were synthesized in the presence of a surfactant (CTAB) by micellar technique in which the metal particles ensured long-term stability in the aqueous dispersion and were prevented from agglomeration. When this surfactant stabilized Pt hydrosol was allowed to react with aqueous suspension of Na⁺ montmorillonite or Li⁺ hectorite, the cationic exchange reaction between Na⁺/Li⁺ and organic cation (CTA⁺) took place with simultaneous incorporation of the reduced Pt particles into the organoclay host. Finely divided and well-dispersed Pt particles (nm range) were generated by this method in the interlamellar space of the montmorillonite and hectorite. The catalyst samples with different metal loadings were synthesized and characterized with UV–Vis spectroscopy, XRD, TEM and AAS techniques. From the TEM micrographs it was confirmed that the diameter of the Pt particles intercalated was in the nanometer range. The catalytic activity of the synthesized catalysts was studied towards the selective hydrogenation of CO bond in cinnamaldehyde using a batch type high pressure reactor at different temperatures and hydrogen pressures. The catalytic activity of the catalysts and their selectivity towards cinnamyl alcohol were discussed in detail. The activity and selectivity of 1 wt.% Pt loaded montmorillonite catalyst was found to be appreciable.     

Green synthesis of silk sericin-capped silver nanoparticles and their potent anti-bacterial activity

In this study, a ‘green chemistry’ approach was introduced to synthesize silk sericin (SS)-capped silver nanoparticles (AgNPs) under an alkaline condition (pH 11) using SS as a reducing and stabilizing agent instead of toxic chemicals. The SS-capped AgNPs were successfully synthesized at various concentrations of SS and AgNO₃, but the yields were different. A higher yield of SS-capped AgNPs was obtained when the concentrations of SS and AgNO₃ were increased. The SS-capped AgNPs showed a round shape and uniform size with diameter at around 48 to 117 nm. The Fourier transform infrared (FT-IR) spectroscopy result proved that the carboxylate groups obtained from alkaline degradation of SS would be a reducing agent for the generation of AgNPs while COO⁻ and NH₂ ⁺ groups stabilized the AgNPs and prevented their precipitation or aggregation. Furthermore, the SS-capped AgNPs showed potent anti-bacterial activity against various gram-positive bacteria (minimal inhibitory concentration (MIC) 0.008 mM) and gram-negative bacteria (MIC ranging from 0.001 to 0.004 mM). Therefore, the SS-capped AgNPs would be a safe candidate for anti-bacterial applications.     

Substrate-mediated enhanced activity of Ru nanoparticles in catalytic hydrogenation of benzene

The impact of carbon substrate-Ru nanoparticle interactions on benzene and hydrogen adsorption that is directly related to the performance in catalytic hydrogenation of benzene has been investigated by first-principles based calculations. The stability of Ru(13) nanoparticles is enhanced by the defective graphene substrate due to the hybridization between the dsp states of the Ru(13) particle with the sp(2) dangling bonds at the defect sites. The local curvature formed at the interface will also raise the Ru atomic diffusion barrier, and prohibit the particle sintering. The strong interfacial interaction results in the shift of averaged d-band center of the deposited Ru nanoparticle, from -1.41 eV for a freestanding Ru(13) particle, to -1.17 eV for the Ru/Graphene composites, and to -1.54 eV on mesocellular foam carbon. Accordingly, the adsorption energies of benzene are increased from -2.53 eV for the Ru/mesocellular foam carbon composites, to -2.62 eV on freestanding Ru(13) particles, to -2.74 eV on Ru/graphene composites. A similar change in hydrogen adsorption is also observed, and all these can be correlated to the shift of the d-band center of the nanoparticle. Thus, Ru nanoparticles graphene composites are expected to exhibit both high stability and superior catalytic performance in hydrogenation of arenes.     

Size controlled synthesis of Pd nanoparticles inspired from the Wacker reaction and their catalytic performances

A novel and facile strategy for the synthesis of size-controlled Pd nanoparticles employing C₂H₄ as the reducing agent was inspired from the Wacker reaction. Uniform Pd nanoparticles with the size ranging from 3 nm to 50 nm were successfully synthesized by using different types of capping agents and optimizing the synthesis parameters. Pd nanoparticles with different sizes exhibit a size-dependent catalytic performance in the aerobic oxidation of benzyl alcohol that could be reasonably attributed to the surface blocking effect exerted by the capping agent chemisorbed on their surfaces and the likely electronic effect.     

Mesoporous Ru/Sn-SBA-15 catalysts: synthesis,characterization and catalytic activity towards hydrogenation of levulinic acid

Journal of Porous Materials - Among the various biomass-derived platform chemicals, levulinic acid (LA) has been identified as one of the top-10 important molecules by Department of Energy, United...     

The formation and catalytic activity of silver nanoparticles in aqueous polyacrylate solutions

Silver nanoparticles (AgNPs) have been synthesized in the presence of polyacrylate through the reduction of silver nitrate by sodium borohydride in aqueous solution. The AgNO3 and polyacrylate carboxylate group concentrations were kept constant at 2.0 × 10^–4 and 1.0 × 10^–2 mol·L^–1, respectively, while the ratio of [NaBH₄]/[AgNO₃] was varied from 1 to 100. The ultraviolet-visible plasmon resonance spectra of these solutions were found to vary with time prior to stabilizing after 27 d, consistent with changes of AgNP size and distribution within the polyacrylate ensemble occurring. These observations, together with transmission electron microscopic results, show this rearrangement to be greatest among the samples at the lower ratios of [NaBH₄]/[AgNO₃] used in the preparation, whereas those at the higher ratios showed a more even distribution of smaller AgNP. All ten of the AgNP samples, upon a one thousand-fold dilution, catalyze the reduction of 4-nitrophenol to 4-aminophenol in the temperature range 283.2–303.2 K with a substantial induction time being observed at the lower temperatures.

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Rapid biological synthesis of silver nanoparticles using Kalopanax pictus plant extract and their antimicrobial activity

Silver nanoparticles (AgNPs) have promising potential in biomedicine, energy science, optics, and health care applications. We synthesized AgNPs using plant, Kalopanax pictus leaf extract. UV-visible spectrophotometric study showed the characteristic peak for AgNPs at wavelength 430 nm. The optical density at 430 nm increased after addition of plant leaf extract, indicating increase in formation of nanoparticles. Comparative time course analyses for AgNP synthesis carried out at different reaction temperatures (20, 60, and 90 °C) revealed higher reaction rate for K. pictus than Magnolia kobus plant leaf extract, which showed highest AgNP synthesis rate in the previous report. Electron microscopy analyses confirmed the presence of well dispersed AgNPs, predominantly with spherical shapes. In transmission electron microscopy, the particle size decreased with increase in temperature. Electron dispersive X-ray spectroscopy analyses indicated that Ag content increased with increase in reaction temperature. Fourier transform-infrared spectroscopy studies revealed capping of bioorganics from plant to the synthesized AgNPs. The antimicrobial activity of the synthesized AgNPs against Escherichia coli increased with increase in reaction temperature. The observations in this study will prove beneficial in approaching rapid synthesis of AgNPs and their antimicrobial application.     

贵金属硫化物催化剂的制备及其在催化加氢反应中的应用

贵金属硫化物催化剂对含硫化合物加氢、加氢脱硫、加氢脱氮和卤代硝基化合物加氢等方面有特殊应用,选择性高,不易失活.总结了国内外贵金属硫化物制备方法,综述了各类贵金属硫化物在催化加氢方面的应用,并对贵金属特别是Pd的不同种硫化物种间相互转变条件进行了探讨.     

C3选择性加氢热耦合催化精馏流程模拟

针对C₃ 选择性加氢过程中冷剂费用过高问题提出将选择性加氢催化反应器设置在脱乙烷精馏塔的提馏段,并通过原流程的3 个精馏塔的不同热耦合方式所构成的3 种热耦合催化精馏结构;对三热耦合催化精馏结构分别进行严格模拟和评价,表明通过分离和加氢反应的结合增加了加氢反应的转化率,并通过热耦合降低了分离能耗,年度总费用降低显著。模拟结果表明,3 种方案的年度总费用节约效果分别为4.107%、6.420%和10.337%。     

A novel route for synthesis of temperature responsive nanoparticles

We report the preparation of responsive silica nanoparticles by reaction of epoxy modified silica with stimuli responsive poly (acrylic acid‐N‐isopropylacrylamide) (poly (AA‐co‐NIPAAm)). A series of copolymers of poly (AA‐co‐NIPAAm) were synthesized by a novel route, employing solid state condensation of polyacrylic acid and isopropyl amine in different feed ratios (44 mol %–100 mol % AA). The structure of the copolymers was characterized by FT‐IR, ¹H‐NMR. The lower critical solution temperature (LCST) was found to vary with the copolymer composition. The pH dependence of the LCST was also observed, and the copolymers exhibited a higher LCST at neutral pH than at acidic pH (4–5). Selected copolymers were used to prepare responsive core‐shell particles. Silica nanoparticles modified using glycidoxy propyl trimethoxy propyl silane were reacted with the responsive copolymer to form responsive core‐shell particles. The influence of reaction conditions on the modification of silica particles and reaction with responsive copolymers was investigated. The hydrodynamic behavior of the synthesized thermo responsive nanoparticles was also studied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Separate deposition of gold and palladium nanoparticles on ordered mesoporous carbon and evaluation of their catalytic activity for cinnamaldehyde hydrogenation under atmospheric condition

We report here, for the first time, a simple method to prepare ordered mesoporous carbon containing separate gold, and palladium nanoparticles (AuPd-OMC). Furthermore, the new catalysts were evaluated in the selective hydrogenation of cinnamaldehyde under atmospheric conditions. In comparison with the monometallic catalysts, the AuPd-OMC exhibited excellent catalytic activity (96.2% selectivity for hydro cinnamaldehyde). The observed synergistic effects were ascribed to hydrogen spillover. The Pd nanoparticles possess the main active sites that formed the active hydrogen species, while the Au nanoparticles served as active hydrogen acceptors and diluted the Pd active sites in order to suppress the deep hydrogenation.     

Hydrothermal synthesis of well-stable silver nanoparticles and their application for enzymeless hydrogen peroxide detection

We reported on a facile hydrothermal synthesis of well-stable silver nanopartiles (AgNPs) from an aqueous solution of AgNO₃ and poly[(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co-(1-vinylpyrrolidone)] (PQ11), a kind of cationic polyelectrolyte, at 100 °C without the extra introduction of other reducing agents and protective agents. Transmission electron microscopy (TEM) observation reveals that the AgNPs thus formed mainly consist of small nanoparticles about 5 nm in diameter. It is found that such dispersion can form stable AgNPs-embedded films on bare electrode surfaces and these nanoparticles exhibit remarkable catalytic performance for hydrogen peroxide (H₂O₂) detection. The sensor has a fast amperometric response time of less than 2 s. The linear range is estimated to be from 1 × 10⁻⁴ M to 0.18 M (r = 0.998) and the detection limit is estimated to be 3.39 × 10⁻⁵ M at a signal-to-noise ratio of 3, respectively.     

Ultrasonic synthesis of highly dispersed Pt nanoparticles supported on MWCNTs and their electrocatalytic activity towards methanol oxidation

A new method of synthesis of highly dispersed Pt nanoparticles with large catalytic surface area on multi-walled carbon nanotubes (MWCNTs) under high-intensity ultrasonic field was developed. The method, with low processing temperature at 25 °C, took only about 5 min. The surface characterization of MWCNTs was carried out by fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy methods. The electrochemical surface area and pore volume of MWCNTs were also examined. The result showed that functional groups of the MWCNTs which favored the high loading and high dispersion of particles and electrochemical surface area of MWCNTs were reinforced in the case of high-intensity ultrasonic field. The Pt/MWCNT catalysts were characterized by energy dispersion X-ray spectra analysis (EDX), transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements. The prepared Pt nanoparticles were uniformly dispersed on the MWCNT surface. The mean size of Pt particles was 3.4 ± 0.2 nm. The electrocatalytic properties of Pt/MWCNT composites and kinetic characterization for methanol electro-oxidation were investigated by cyclic voltammetry. The Pt/MWCNT catalysts prepared for 5 min in ultrasonic field present excellent electrochemical activities. The schematic of the reaction was also introduced.     

Extracellular synthesis of crystalline silver nanoparticles and molecular evidence of silver resistance from Morganella sp.: towards understanding biochemical synthesis mechanism

There has been significant progress in the biological synthesis of nanomaterials. However, the molecular mechanism of synthesis of such bio-nanomaterials remains largely unknown. Here, we report the extracellular synthesis of crystalline silver nanoparticles (AgNPs) by using Morganella sp., and show molecular evidence of silver resistance by elucidating the synthesis mechanism. The AgNPs were 20+/-5 nm in diameter and were highly stable at room temperature. The kinetics of AgNPs formation was investigated. Detectable particles were formed after an hour of reaction, and their production remained exponential up to 18 h, and saturated at 24 h. Morganella sp. was found to be highly resistant to silver cations and was able to grow in the presence of more than 0.5 mM AgNO(3). Three gene homologues viz. silE, silP and silS were identified in silver-resistant Morganella sp. The homologue of silE from Morganella sp. showed 99 % nucleotide sequence similarity with the previously reported gene, silE, which encodes a periplasmic silver-binding protein. The homologues of silP and silS were also highly similar to previously reported sequences. Similar activity was totally absent in closely related Escherichia coli; this suggests that a unique mechanism of extracellular AgNPs synthesis is associated with silver-resistant Morganella sp. The molecular mechanism of silver resistance and its gene products might have a key role to play in the overall synthesis process of AgNPs by Morganella sp. An understanding of such biochemical mechanisms at the molecular level might help in developing an ecologically friendly and cost-effective protocol for microbial AgNPs synthesis.     

Correlation between the basicity of solid bases and their catalytic activity towards the synthesis of unsymmetrical organic carbonates

The correlation between the basic properties of solid catalysts and the reaction rate of the selective synthesis of unsymmetrical organic carbonates via direct condensation of diethylcarbonate (DEC) and alcohols was investigated. A detailed kinetic study of the transesterification of 1-phenylethanol and DEC was made with catalysts with different basic strengths. The solids included fluorinated hydrotalcite, MgLa mixed oxides, CsF (pure or supported on α- and γ-aluminas), KF (pure or supported on α- and γ-aluminas), anatase, rutile, and zirconia. Basic properties were determined by the adsorption of CO₂, measured by gravimetry coupled with mass spectrometry and by calorimetry. Both techniques show a higher basicity for MgLa mixed oxides. The rate of the reaction was roughly proportional to the number of strongly basic sites present on the catalyst, except for CsF/α-Al₂O₃, which showed higher activity for several different substrates in spite of a lower number and strength of basic sites. This is attributed to the high nucleophilicity of the alcoholate formed as an intermediate. The addition of water to the reaction medium induces two effects: inhibition of the reaction and the promotion of etherification of the substrate by ethanol as a side reaction. The catalysts can be reused several times with a small loss of activity.     

Morphology manipulation of silica nanoparticles via the catalytic templates reaction system

In this study, we have developed a synthetic method which can precisely and conveniently manipulate the morphologies of silica nanoparticles at the molecular level. The reaction system contains cationic cetyltrimethylammonium bromide (CTAB), fatty acid salts, modulating molecules, silica precursor, and water. No additional alkaline catalysts and organic solvents are needed. Fatty acid salts, acting as the catalytic co-surfactants and the shaping agents as well, form uniform self-assembly templates with cationic CTAB. All the synthetic silica nanoparticles are characterized using TEM, SEM and N₂ sorption experiments. Results show that the generated nanoparticles are highly dispersed and demonstrate a variety of surface morphologies such as solid, porous, spokewise, sponge-like, walnut-like, Swiss roll-like appearance. The morphology transitions can be tuned by changing the aliphatic lengths (C2 to C18) of catalytic fatty acid salts, the concentration of silica precursor, and the combination of the fatty acid salts with different carbon chains. In the case of all the porous nanoparticles, the pore size (from ～2.5 nm to > 100 nm, from single-pore type to dual-pore type) can be obtained by the adjustment of above parameters. In addition, the silica nanoparticles can also be transformed to extremely small granulates（～8 nm to the lowest）and hollow shells via introducing specific compounds (called modulating molecules) that regulate the molecular interactions within the reaction system. The developed reaction system is environment-friendly. The current work could be applied to the engineering of preparing other nanomaterials via the sol-gel method.     

Preparation of polyelectrolyte‐stabilized silver nanoparticles for catalytic applications

A facile and green method is developed for the preparation of polyelectrolyte‐stabilized silver nanoparticles (AgNPs ) using dopamine as a reducing agent. The AgNPs were prepared in the presence of the polyelectrolyte poly[acrylamide‐co ‐(diallyldimethylammonium chloride)] (PADA ) and amine‐functionalized silane matrices. Interestingly, only amine‐functionalized silanes led to AgNPs in the presence of PADA , whereas silane without amine functionalization failed to produce them. The catalytic ability of the AgNPs was investigated by adopting a benchmark reaction, i.e. reduction of 4‐nitrophenol in the presence of sodium borohydride. It was found that PADA ‐Ag(0.1)‐TPDT (TPDT = N ‐[3‐(trimethoxysilyl)propyl]diethylenetriamine) showed better catalytic activity when compared to other silver concentrations of 0.05, 0.5 and 1 mmol L^?1. Remarkably, a very high normalized rate constant, 20 374 s^?1 g^?1, was observed for PADA ‐Ag(0.1)‐TPDT . © 2016 Society of Chemical Industry