The development of dependable, environmentally benign processes for the synthesis of nanoscale materials is an important aspect of nanotechnology. In the present study, we report one-pot biogenic fabrication of palladium nanoparticles by a simple procedure using broth of Cinnamomum camphora leaf without extra surfactant, capping agent, and/or template. The mean size of palladium nanoparticles, ranging from 3.2 to 6.0 nm, could be facilely controlled by merely varying the initial concentration of the palladium ions. The polyols components and the heterocyclic components were believed to be responsible for the reduction of palladium ions and the stabilization of palladium nanoparticles, respectively.National Natural Science Foundation of China [20776120, 20576109]; National High Technology Research and Development Program of China [2007AA03Z347]; Natural Science Foundation of Fujian Province of China [2008J0169

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Gardenia jasminoides Ellis' water crude extract was used for the bioreduction of palladium chloride in this paper. The UV-vis spectrum, x-ray diffraction spectrum measurement, the Fourier transform infrared spectroscopy and TEM technique confirmed the formation of palladium nanoparticles and identified antioxidants including geniposide, chlorogenic acid, crocins and crocetin were reducing and stabilizing agents for synthesizing palladium nanoparticles in water crude extract. The particle size and dispersity were temperature-dependent. The particle sizes ranged from 3 to 5 nm and revealed the best dispersity at 70 degrees C. Catalytic performance of the biosynthetic Pd nanoparticles with good dispersity was investigated by hydrogenation of p-nitrotoluene. The catalysts showed a conversion of 100% under conditions of 5 MPa, 150 degrees C for 2 h. The selectivity of p-methyl-cyclohexylamine achieved 26.3%. The catalyst was recycled five times with no agglomeration and maintained activity, which was attributed to the appropriate protection of the antioxidants. On the basis of the study, it appears to be a new promising biosynthetic nanocatalyst for the development of an industrial process.

A series of Au/TiO2 catalysts for CO oxidation with same Au loading but different Au nanoparticles (NPs) sizes were prepared by varying the calcination temperatures and biomass concentration via a biosynthetic approach. The resulting catalysts were characterized by DRUV–vis, TEM, and TG techniques. The experimental results showed that the activity of the gold catalysts for CO oxidation was very sensitive to the particle size. Among the tested catalysts, the one with mean size of 3.8 nm was the most active. As determined by TEM, the contact boundary between the Au NPs and the TiO2 support was related to the size of the Au NPs. For the most active catalyst, hemispherical Au NPs (3.8 ± 0.6 nm) had the best contact boundary with the TiO2 support, yielding the longest perimeter interface, suggesting that the contact boundary was the most critical factor for the CO oxidation. The in-situ FTIR study of CO adsorption on the catalysts showed that CO was not adsorbed on the Au surface. This might be due to the modification of the Au/TiO2 catalysts by the residual biomass. The intensity of the peak at 2185 cm–1 for the Au/TiO2 catalysts with the longest perimeter interface was highest, demonstrating that the Au–TiO2 contact boundary played an important role in the adsorption of CO.

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