Xiaolian Jing

Plant-mediated synthesis of platinum nanoparticles and its bioreductive mechanism.

Pt nanoparticles (PtNPs) were biologically synthesized by reducing Na2PtCl4 with Cacumen Platycladi Extract (CPE). The effects of reaction temperature, initial Pt(II) concentration, and CPE percentage on Pt(II) conversion and the size distribution of the PtNPs were studied. The results showed that the Pt(II) conversion rate reached 95.9% and that PtNPs measuring 2.4±0.8nm were obtained under the following conditions: reaction temperature, 90°C; CPE percentage, 70%; initial Pt(II) concentration, 0.5mM; reaction time, 25h. In addition, the bioreduction of Pt(II) was attributed to reducing sugars and flavonoids rather than proteins. The elucidation of bioreductive mechanism of Pt(II) ions was achieved by investigating the changes that occurred in the reducing sugar, flavonoid and protein concentrations in the plant extract, leading to a good insight into the formation mechanism of such biosynthesized PtNPs.

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 HAuCl4 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.

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 O2-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-Al2O3 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.

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

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 H2 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.

Catalytic Application of Biogenic Platinum Nanoparticles for the Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

Pt catalysts and Co doped Pt catalysts with TiO2 as the support were prepared by the sol immobilization method based on biological synthesis process, whereby Pt nanoparticles (PtNPs) were reduced from Na2PtCl4 using Cacumen Platycladi extract (CPE). The catalytic performance of the catalysts was studied using hydrogenation of cinnamaldehyde as the model reaction. For comparison, Co doped Pt/catalysts were also prepared by traditional impregnation method, TEM observation, and XRD measurement were carried out to characterize the catalysts. The effects of different Pt loadings and Co doping amounts were investigated. The results showed that the PtNPs could be well dispersed onto the TiO2 support with narrow size distribution between 4 and 6 nm. 1.0% was observed as the optimal Pt loading amount in our experiments showing a cinnamaldehyde conversion of 73.3% with 68.8% selectivity to cinnamyl alcohol. A proper Co doping amount was also essential to the catalytic performance of the prepared Pt/catalysts as well as a favorable for the reaction process, 1.0% doping amount showed the best activity in which a 70.4% conversion and 88.3% selectivity was achieved. Recyclability tests carried out revealed that the 1.0 Co–1.0 Pt/TiO2 catalysts possessed possessing good durability. In this work, Co-Pt/TiO2 catalysts prepared by the sol immobilization method based on biological reduction process, showed better selectivity than that from traditional impregnation method.

Plant-mediated synthesis of ZnO supported Ni-Pd alloy catalyst for the selective hydrogenation of 1, 3-butadiene

We report the green synthesis of ZnO‐supported Ni‐Pd alloy nanoparticles for the gas‐phase selective hydrogenation of 1,3‐butadiene. The supported catalysts were synthesized through a simple bioreduction route using Cinnamomum Camphora leaf extract. We used XRD, SEM, TEM, and energy‐dispersive X‐ray spectroscopy to characterize and verify the nature of the catalysts. The results showed that the size of the Ni‐Pd alloy particles was (3.2±0.7), (3.4±0.3), and (3.8±0.6) nm for Ni1Pd1, Ni1Pd3, and Ni3Pd1 respectively. FTIR spectroscopy revealed that the presence of stretching vibrations from C−H, −C=C−, O−H, and −C−O−O groups that remained on the surface and act as stabilizers. The influence of some reaction variables, such as the type of S‐Pd (S=Au, Ag, Ni) bimetallic catalyst, the type of metal oxide support, and the reaction temperature, on the hydrogenation activity and selectivity towards total butene (trans‐2‐butene, 1‐butene, and cis‐2‐butene) is investigated. The bioreduced, supported catalysts showed excellent catalytic activity and selectivity to butene in the selective hydrogenation of 1,3‐butadiene. The calculated total butene selectivity was above 80 % for all supported S1‐Pd1 catalysts compared to 46.92 % for a monometallic Pd/ZnO catalyst. In addition, the Ni1‐Pd1/ZnO catalyst presented the best butene yield of 88.90 %, which was 1.9 times that of the Pd/ZnO catalyst. Moreover, it remained stable over a 10 h durability experiment.

Biosynthesis of flat silver nanoflowers: From Flos Magnoliae Officinalis extract to simulation solution

Abstract Flat Ag nanoflowers were directly synthesized from the bioreduction of AgNO3 using Flos Magnoliae Officinalis extract without any additional stabilizer or protective agent at room temperature. Effects of concentrations of the Flos Magnoliae Officinalis extract on the Ag nanostructures were investigated. The main components containing flavone, polyphenol, protein, and reducing sugar in the plant extract were thoroughly determined before and after the reaction, and the dialysis experiments were also conducted. The results of components analysis and dialysis showed that gallic acid representing polyphenols played an important role in the biosynthesis of silver nanoplates. Trisodium citrate combined gallic acid solution, instead of Flos Magnoliae Officinalis extract, was employed and successfully simulated the biosynthesis process of the flat Ag nanoflowers.Graphical Abstract