Role of Mineral Nutrients in Plant-Mediated Synthesis of Three-Dimensional Porous LaCoO3

With the assistance of plant extracts, the facile synthesis of three-dimensional (3D) porous LaCoO3 perovskite is reported at a lower calcination temperature of 500 °C. The formation mechanism is carefully studied by investigating the different roles of organic and inorganic components in Cacumenplatycladi extract. The results indicate that organic components (mainly phenolic acids) function as the similar complex species of citric acid, while the mineral nutrients (Na+, K+, Ca2+, and Mg2+) together with NO3– serve as combustion-aid agents even with trace amounts. Moreover, the biosynthesized LaCoO3 has a high surface area of 32.5 m2 g–1 and exhibits excellent catalytic performance for benzene oxidation. Benzene of 1000 ppm can achieve a stable conversion above 90% at 285 °C in a continuous run for 80 h (weight-hourly space velocity (WHSV) = 40 000 mL g–1 h–1). It can be attributed to the bio-LaCoO3 with more electrophilic adsorption of oxygen species and 3D porous structure

Microwave-Assisted Biosynthesis of Ag/ZrO2 Catalyst with Excellent Activity toward Selective Oxidation of 1,2-Propanediol

通讯作者地址: Huang, JLIn the biorefining process, polyols are important intermediates, and the oxidation of polyols toward other value added products is of great significance. This work describes a green and facile biosynthesis method for the preparation of Ag/ZrO2 catalyst for selective oxidation of 1,2-propanediol (a typical polyol). Cinnamomum comphora (CC) leaf extract was employed as the reducing and capping agent for the preparation of Ag nanoparticles (NPs) with the assistance of microwave irradiation. The main reducing agents were identified as polyphenols by Fourier transform infrared spectroscopic analysis of CC extracts before and after reaction. After electrostatic adsorption, the NPs were anchored onto the support ZrO2. The Ag/ZrO2 catalysts were found with good dispersity and showed excellent activity toward selective oxidation of 1,2-propanediol. The effects of the preparation conditions on catalyst activity were studied; the optimal condition was obtained (microwave time of 4 min, CC concentration of 12 g/L and Ag loading of 5%). Since the natural capping agents are easy to remove, the catalysts need no calcination treatment before catalytic reaction. Thus, the microwave-assisted biosynthesis appears to be environmentally benign as neither expensive chemicals nor intensive energy consumption is engaged.National Nature Science Foundation 21036004 2120614

Plant-mediated fabrication and surface enhanced raman property of flower-like Au@Pd nanoparticles

The flower-like nanostructures of an Au core and Pd petals with the average size of 47.8 nm were fabricated through the successive reduction of HAuCl4 and Na2PdCl4 at room temperature. During the synthesis, Cacumen Platycladi leaf extract served as weak reductant and capping agent. Characterization techniques such as Energy-dispersive X-ray spectroscopy, UV-Vis spectroscopy, and X-ray diffraction characterizations were employed to confirm that the as-synthesized nanoparticles have the structure of core-shell. The obtained core-shell nanoflowers exhibited good surface enhanced Raman spectroscopic activity with Rhodamine 6G. ? 2014 by the authors

Biosynthesized Ag/alpha-Al2O3 catalyst for ethylene epoxidation: the influence of silver precursors

NSFC [21206140, 21036004]; State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals [SKL-SPM-201210]Biosynthesized Ag/alpha-Al2O3 catalysts toward ethylene epoxidation were prepared with Cinnamomum camphoratrees (CC) extract using AgNO3, silver-ammonia complex ([Ag (NH3)(2)](+)) and silver-ethylenediamine complex ([Ag(en)(2)](+)) as the silver precursors. The catalyst from [Ag(en)(2)](+) demonstrated better activity compared to the catalysts from the other two precursors, 1.41% EO concentration with EO selectivity of 79.1% and 12.0% ethylene conversion were achieved at 250 degrees C. To investigate the influence of silver precursors on the catalytic performance, three catalysts were characterized by XRD, UV-Vis, XPS, SEM and O-2-TPD techniques. The results indicated that [Ag(en)(2)](+) precursors could be reduced more effectively by CC extract, and Ag particles were successfully immobilized onto the alpha-Al2O3 support under mild conditions. Moreover, a silver defects surface on the Ag/alpha-Al2O3 catalyst from [Ag(en)(2)](+) precursors had the best oxygen activation ability, playing an important role in the generation of electrophilic oxygen species which were responsible for the epoxidation reaction of C=C to EO

Biosynthesized Ag/α-Al2O3 catalyst for ethylene epoxidation: The influence of silver precursors

Biosynthesized Ag/α-Al2O3 catalysts toward ethylene epoxidation were prepared with Cinnamomum camphoratrees (CC) extract using AgNO3, silver-ammonia complex ([Ag (NH3) 2]+) and silver-ethylenediamine complex ([Ag(en) 2]+) as the silver precursors. The catalyst from [Ag(en)2]+ demonstrated better activity compared to the catalysts from the other two precursors, 1.41% EO concentration with EO selectivity of 79.1% and 12.0% ethylene conversion were achieved at 250 °C. To investigate the influence of silver precursors on the catalytic performance, three catalysts were characterized by XRD, UV-Vis, XPS, SEM and O 2-TPD techniques. The results indicated that [Ag(en) 2]+ precursors could be reduced more effectively by CC extract, and Ag particles were successfully immobilized onto the α-Al 2O3 support under mild conditions. Moreover, a silver defects surface on the Ag/α-Al2O3 catalyst from [Ag(en)2]+ precursors had the best oxygen activation ability, playing an important role in the generation of electrophilic oxygen species which were responsible for the epoxidation reaction of CC to EO. ? 2014 the Partner Organisations

Microorganism-mediated synthesis of chemically difficult-to-synthesize Au nanohorns with excellent optical properties in the presence of hexadecyltrimethylammonium chloride

Fundamental Research Funds for Central Universities [2010121051]; NSFC [21106117, 21036004]Closely packed, size-controllable and stable Au nanohorns (AuNHs) that are difficult to synthesize through pure chemical reduction are facilely synthesized using a microorganism-mediated method in the presence of hexadecyltrimethylammonium chloride (CTAC). The results showed that the size of the as-synthesized AuNHs could be tuned by adjusting the dosage of the Pichia pastoris cells (PPCs). The initial concentrations of CTAC, ascorbic acid (AA) and tetrachloroaurate trihydrate (HAuCl4 center dot 3H(2)O) significantly affected the formation of the AuNHs. Increasing the diameters of AuNHs led to a red shift of the absorbance bands around 700 nm in their UV-vis-NIR spectra. Interestingly, the AuNH/PPC composites exhibited excellent Raman enhancement such that rhodamine 6G with concentration as low as (10(-9) M) could be effectively detected. The formation process of the AuNHs involved the initial binding of the Au ions onto the PPCs with subsequent reduction by AA to form supported Au nanoparticles (AuNPs) based on preferential nucleation and initial anisotropic growth on the platform of the PPCs. The anisotropic growth of these AuNPs, which was influenced by CTAC and PPCs, resulted in the formation of growing AuNHs, while the secondary nucleation beyond the PPCs produced small AuNPs that were subsequently consumed through Ostwald ripening during the aging of the AuNHs. This work exemplifies the fabrication of novel gold nanostructures and stable bio-Au nanocomposites with excellent optical properties by combining microorganisms and a surfactant

Precisely controlled resorcinol-formaldehyde resin coating for fabricating core-shell, hollow, and yolk-shell carbon nanostructures

MOST of China [2011CB932403, 2009CB930703]; NSFC [21131005, 21021061, 20925103, 20923004]; Fok Ying Tung Education Foundation [121011]This work provides a facile one-step sol-gel route to synthesize high-quality resorcinol-formaldehyde (RF) resin coated nanocomposites that can be further used to fabricate desired carbon nanostructures. Colloidal particles with different morphologies and sizes can be coated with high-quality RF resin shells by the proposed cationic surfactant assisted RF resin coating strategy. The as-synthesized RF resin coated nanocomposites are ideal candidates for selective synthesis of core-shell, hollow, and yolk-shell carbon nanostructures. Based on the carboxylic functional RF resin coating, graphitic carbon nanostructures can also be synthesized by employing the graphitization catalyst. The as-synthesized carbon nanostructures show the advantageous performances in several applications. Hollow carbon spheres are potential electrode materials for lithium-sulfur batteries. Hollow graphitic spheres are promising catalyst supports for oxygen reduction reaction. And yolk-shell structured Au@HCS nanoreactors with ultrathin shells exhibit high catalytic activity and recyclability in confined catalysis

Fabrication of Au/Pd alloy nanoparticle/Pichia pastoris composites: a microorganism-mediated approach

Fundamental Research Funds for Central Universities [2010121051]; NSFC projects [21106117, 21036004]Synthesis of metal nanoparticles (NPs) is in the limelight in modern nanotechnology. In this present study, bimetallic Au/Pd NP/Pichia pastoris composites were successfully fabricated through a one-pot microbial reduction of aqueous HAuCl4 and PdCl2 in the presence of H-2 as an electron donor. Interestingly, flower-like alloy Au/Pd NP/Pichia pastoris composites were obtained under the following conditions, NaCl concentration 0.9% (w/v), molar ratio of Au/Pd (1 : 2) and the time for pre-adsorption of Au(III) and Pd(II) ions 15 min, through fresh yeast reduction. The mapping results from scanning transmission electron microscopy (STEM) with a high-angle annular dark field detector confirmed that the Au/Pd NPs on the surface of the yeast were indeed alloy. Furthermore, the energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) measurements showed that the composition of the bimetallic NPs were consistent with the initial molar ratio of the precursors

Biogenic flower-shaped Au-Pd nanoparticles: Synthesis, SERS detection and catalysis towards benzyl alcohol oxidation

～40 nm flower-shaped Au-Pd bimetallic nanoparticles were prepared in a facile and eco-friendly way based on the simultaneous bioreduction of HAuCl 4 and Na2PdCl4 with ascorbic acid and Cacumen Platycladi leaf extract at room temperature. Characterization techniques, such as transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction, were employed to confirm that the as-synthesized nanoparticles were alloys. The obtained flower-shaped Au-Pd alloy nanoparticles exhibited an excellent surface enhanced Raman spectroscopic activity with rhodamine 6G and efficient catalytic ability for the oxidation of benzyl alcohol to benzaldehyde. ? 2014 The Royal Society of Chemistry

Microorganism-mediated synthesis of chemically difficult-to-synthesize Au nanohorns with excellent optical properties in the presence of hexadecyltrimethylammonium chloride

Fundamental Research Funds for Central Universities [2010121051]; NSFC [21106117, 21036004]Closely packed, size-controllable and stable Au nanohorns (AuNHs) that are difficult to synthesize through pure chemical reduction are facilely synthesized using a microorganism-mediated method in the presence of hexadecyltrimethylammonium chloride (CTAC). The results showed that the size of the as-synthesized AuNHs could be tuned by adjusting the dosage of the Pichia pastoris cells (PPCs). The initial concentrations of CTAC, ascorbic acid (AA) and tetrachloroaurate trihydrate (HAuCl4 center dot 3H(2)O) significantly affected the formation of the AuNHs. Increasing the diameters of AuNHs led to a red shift of the absorbance bands around 700 nm in their UV-vis-NIR spectra. Interestingly, the AuNH/PPC composites exhibited excellent Raman enhancement such that rhodamine 6G with concentration as low as (10(-9) M) could be effectively detected. The formation process of the AuNHs involved the initial binding of the Au ions onto the PPCs with subsequent reduction by AA to form supported Au nanoparticles (AuNPs) based on preferential nucleation and initial anisotropic growth on the platform of the PPCs. The anisotropic growth of these AuNPs, which was influenced by CTAC and PPCs, resulted in the formation of growing AuNHs, while the secondary nucleation beyond the PPCs produced small AuNPs that were subsequently consumed through Ostwald ripening during the aging of the AuNHs. This work exemplifies the fabrication of novel gold nanostructures and stable bio-Au nanocomposites with excellent optical properties by combining microorganisms and a surfactant