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The Au/TS-1 catalysts with different Au nanoparticles (NPs) sizes ranging from 3.1 to 8.4 nm but the same Au loading of 0.5 wt% were prepared by Cinnamomum camphora (CC) extract, and were used for propylene epoxidation. The results showed that the interaction between Au and TS-1 support surface is important for propylene epoxidation and much smaller Au NPs (

Microorganism-mediated, hexadecyltrimethylammonium chloride (CTAC)-directed (MCD) method was employed in this work to synthesize Pd nanoflowers (PdNFs). Proper Pichia pastoris cells (PPCs) dosage, ascorbic acid (AA), Pd(NO 3 ) 2 and CTAC concentrations were essential for the growth of the PdNFs. The size of the as-synthesized PdNFs could be tuned by adjusting the amount of Pd(NO 3 ) 2 solution and dosage of PPCs used. Characterization techniques such as X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to verify the nature of the PdNFs. Finally the PdNF/PPC nanocomposites were immobilized onto TiO 2 supports to obtain bio-PdNF/TiO 2 catalysts which showed excellent catalytic activity for CO oxidation, obtaining 100% conversion at 100 °C and remaining stable over a period of 52 h of reaction time.

BACKGROUND Au valence for Au catalysts has been considered a vital parameter for catalytic activity towards CO oxidation. However, there is no effective method to prepare precise Au0/Auδ+ molar ratios with the same Au nanoparticles (NPs) sizes. RESULTS A series of Au/TiO2 catalysts with tuneable Au0/Auδ+ molar ratios were prepared by the combination of a biosynthesis method and a deposition–precipitation (DP) method, and characterized by XPS, TEM, DRUV-Vis techniques. First, biosynthesized metallic Au NPs were immobilized onto TiO2 supports to obtain Au/TiO2 catalysts with different Au loadings but with the same sized Au NPs. And then positively ionized Au species were supported onto the above Au/TiO2 catalysts by a DP method. The metallic Au and positively ionized Au species could be totally supported on the support. Therefore, the Au0/Auδ+ molar ratios could be controlled exactly. Compared with Au/TiO2 catalysts with metallic and positively ionized Au species alone, the catalyst Au/TiO2-1:1 showed the best initial catalytic activity, suggesting enhanced catalytic performance due to the coexistence of Au0 and Auδ+. CONCLUSION This study verifies that Au/TiO2 catalysts with accurate Au0/Auδ+ molar ratios can be prepared by a combination of biosynthesis and a DP method. © 2015 Society of Chemical Industry

In this paper, we report a microwave-assisted biosynthesis method with Cinnamomum camphora (CC) leaf extract for the green and rapid synthesis of Ag nanoparticles (NPs). The as-produced Ag nanoparticles were immobilized onto CeO 2 as supported Ag/CeO 2 catalyst, which proved to be efficient for carbon monoxide (CO) oxidation. Active components in the plant extract were identified by FTIR analysis and later on validated through simulated experiments. The results revealed that polyphenols and proteins were the reducing and protecting agents, respectively. The optimum preparation conditions for the catalyst were irradiation time of 140 s, Ag loadings of 5 wt.%, CC extract concentration of 25 g L −1 and sintering temperature of 300 °C. Since biomolecules adsorbed over the surface of catalyst was detrimental to its catalytic activity, calcination to remove the biomolecules was critical to the enhanced activity. Considering the trade-off between particle size and biomass removal extent, the optimum calcination temperature was determined to be 300 °C.

Pd/γ-Al2O3 catalysts efficient for the liquid-phase hydrogenation of 2-ethyl-9,10-anthraquinone were prepared via an adsorption–reduction method using Cacumen Platycladi extract as both reductive and protective agent. The catalysts were characterized by N2 physisorption, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The results showed that Pd nanoparticles (NPs) measuring

Herein, we reported the green synthesis of Ag–Pd alloy nanoparticles (NPs) using the aqueous extract of the Cacumen platycladi leaves as well as their application as catalyst for hydrogenation of 1,3-butadiene. The biosynthetic NPs were characterized to confirm the nature of alloy by UV–vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The possible functional groups responsible for the reduction and protection of NPs were identified through Fourier transform infrared spectroscopy (FTIR). The results revealed that biomolecules like saccharides, polyphenols, or carbonyl compounds were related to the reduction process, and the (NH)C═O groups were responsible for the stabilization of the NPs. Furthermore, the as-formed Ag–Pd bimetallic-supported catalysts especially Ag1Pd3/γ-Al2O3 was found to possess excellent catalytic performance toward hydrogenation of 1,3-butadiene. A butene yield of 84.9% was obtained, which was remarkably ...

Au/TS-1 catalysts prepared by an eco-friendly and economical bioreduction method were used for the liquid phase epoxidation of styrene to styrene oxide (SO) using aqueous hydrogen peroxide (H2O2) as oxidant. The catalysts were characterized by a variety of techniques including FT-IR, DRUV–Vis, UV–Vis, N2 physisorption, XRD, XPS, TG–DTG and TEM. The influence of various parameters (Au loading, calcination, solvents, oxidants, reaction temperature, reaction time and catalyst amount) on the catalytic performance was systematically investigated. The results showed that both the conversion of styrene and selectivity to SO were improved and enhanced when catalyzed by biosynthesized gold nanoparticles (GNPs) supported on TS-1. However, decomposing the Cacumen Platycladi (CP) biomass properly through calcinations can enhance the catalytic performance though it acted as reductant and protective agents during the catalysts preparation. Besides, the optimum catalytic activity and stability of bioreduction Au/TS-1 catalysts were obtained under operational conditions of Au loading of 1.0 wt.%, CP extract (10 g L−1) as reductant, calcined at 723 K for 2 h, reaction time of 10 h, reaction temperature of 333 K, catalyst amount of 500 mg, aqueous H2O2 (30 wt.%) as oxidant and N,N-dimethylformamide as solvent. Under the optimal condition, styrene conversion of 92.7% and SO selectivity of 90.4% was achieved, which were comparable or even superior to those reported in the literatures. The catalyst was reused five times, without significant decrease in both the styrene conversion and SO selectivity.

BACKGROUND The facile use of microorganisms as green templates for shape-control of Au nanostructures can not only utilize their characteristic nanoscale dimensions and versatility, but also bridge the gap between bulk materials and Au nanostructures for technical applications. RESULTS Using Escherichia coli cells (ECCs), closely packed, hierarchically branched, chemically difficult-to-synthesize and stable Au nanowires (AuNWs) were fabricated through a seedless microorganism-mediated, hexadecyltrimethylammonium bromides (CTAB)-directed method. The ECCs played dual roles in the biosorption of Au ions and acted as preferential nucleation sites for Au nanocrystals in the formation of the AuNWs. In addition, proper CTAB concentration and just a little excessive ascorbic acid were essential to the formation of the AuNWs. The preferential nucleation sites that were simultaneously mediated by adjacent cells favored branched growth. Random growth of the same nanowire with multiple branched points gave rise to hierarchically branched AuNWs. Interestingly, the AuNW/ECC nanocomposites exhibited a noticeable absorbance at around 1900 nm in the near-infrared (NIR) region. CONCLUSION This study verifies the general strategy by combining a microorganism and CTAB for the fabrication of functional AuNW/microorganism nanocomposites. © 2013 Society of Chemical Industry

Anatase type extra-framework titanium in titanium silicate-1 (TS-1) molecular sieves has been observed to cause adverse catalytic impediments such as carbon–carbon bond cleavage and low H 2 O 2 efficiency during the epoxidation of terminal alkenes. In this study, a series of TS-1 sieves were synthesized, and used as catalysts for styrene epoxidation. Among the catalysts, the TS-1 with a Si/Ti molar ratio of 35 and 0.21 mol% of anatase type extra-framework titanium exhibited the best styrene conversion and styrene oxide (SO) selectivity. The results suggests that, framework Ti species have no effect on the stabilization of SO selectivity, whereas the synergetic interaction between the framework Ti species and the anatase type extra-framework titanium is essential for the outstanding catalytic performance of TS-1 in styrene epoxidation. In addition, our results demonstrate that the usage of tetraethyl orthosilicate (TEOS), tetrabutyl titanate (TBOT), and isopropyl alcohol in the synthesis of TS-1 does not guarantee the absence of extra-framework Ti species. Instead, the asynchronous degrees of hydrolysis between TEOS and TBOT might account for the formation of the anatase type extra-framework titanium. The influence of H 2 O 2 amount, reaction temperature and time, as well as the types of solvent, oxidant, and catalyst amount, on the catalytic performance of TS-1 with anatase type extra-framework titanium was likewise investigated.

The oxidation of benzyl alcohol, with molecular oxygen at atmospheric pressure in an aqueous medium, is investigated using Au–Pd/MgO bimetallic catalysts to examine the effect of catalyst parameters (viz. preparation method, Au/Pd molar ratio, and calcinations temperature) and reaction conditions (viz. reaction temperature and oxygen flow rate) on conversion and selectivity. The bimetallic catalysts were prepared via two novel reduction methods with bio-reducing agents and were characterized by transmission electron microscopy, X-ray diffraction, diffuse reflectance UV–vis spectroscopy, and thermogravimetric analysis to understand synergistic interactions between Au and Pd. Under optimal conditions, the Au–Pd bimetallic catalysts, with a 1:1 molar ratio and 9.7 ± 1.3 nm particle size, exhibited remarkably enhanced catalytic activity (>52%) and selectivity (∼100%) compared with their monometallic counterparts. Moreover, the activity of the catalysts was maintained after six recycles without agglomeration.

Biosynthesized gold nanoparticles (GNPs) were transferred from water to a hydrophobic ionic liquid (IL), [Bmim]PF(6), with the assistance of alkyl trimethyl ammonium bromide. The phase transfer mechanism was illustrated through the exemplification of cetyltrimethyl ammonium bromide (CTAB). Interaction between GNPs and CTAB was demonstrated through zeta potential analysis. Moreover, an anion-exchange process was discovered between CTAB and IL. During the process, the hydrophobic CTAPF(6) formed in situ on the GNPs led to the hydrophobization and thus phase transfer of the GNPs. The phase transfer efficiency was found to be size-dependent.

Lacking of quantitative experimental data and/or kinetic models that could mathematically depict the redox chemistry and the crystallization issue, bottom-to-up formation kinetics of gold nanoparticles (GNPs) remains a challenge. We measured the dynamic regime of GNPs synthesized by l-ascorbic acid (representing a chemical approach) and/or foliar aqueous extract (a biogenic approach) via in situ spectroscopic characterization and established a redox–crystallization model which allows quantitative and separate parameterization of the nucleation and growth processes. The main results were simplified as the following aspects: (I) an efficient approach, i.e., the dynamic in situ spectroscopic characterization assisted with the redox–crystallization model, was established for quantitative analysis of the overall formation kinetics of GNPs in solution; (II) formation of GNPs by the chemical and the biogenic approaches experienced a slow nucleation stage followed by a growth stage which behaved as a mixed-order reaction, and different from the chemical approach, the biogenic method involved heterogeneous nucleation; (III) also, biosynthesis of flaky GNPs was a kinetic-controlled process favored by relatively slow redox chemistry; and (IV) though GNPs formation consists of two aspects, namely the redox chemistry and the crystallization issue, the latter was the rate-determining event that controls the dynamic regime of the whole physicochemical process.