The appropriate choice of chemical composition of a metallic precursor, which produces the basic structure units in the growth process of nanocrystals, is a high priority in the synthesis of metal--especially Au--nano...The appropriate choice of chemical composition of a metallic precursor, which produces the basic structure units in the growth process of nanocrystals, is a high priority in the synthesis of metal--especially Au--nanoparticles. In the present work, Au seeds （prepared by the reduction of Au3＋ solution with NaBI~ in the presence of cetyltrimethylammonium bromide （CTAB）） have been used to initiate the growth of Au nanoparticles from two different Au precursors. When an aqueous Au＋ solution prepared in the presence of CTAB micelles was treated with ascorbic acid in the presence of the gold seeds, a high yield （up to 92%） of gold nanoparticles was obtained. By varying the volume of the seed solution with a fixed amount of Au＋, we can effectively control the morphological transformation of the resulting Au nanoparticles from cubes to octahedra. When an aqueous Au3＋ solution was prepared in the presence of CTAB micelles and treated with ascorbic acid in the presence of the gold seeds, smaller yields of Au nanoparticles were obtained. A preliminary growth mechanism has been proposed based on the changes induced by varying the amount of ascorbic acid and the ratio of the concentration of Au＊ to the number of seeds.展开更多
Based on the layer-by-layer self-assembly of positively charged cetyltrimethylammonium bromide （CTAB） wrapped gold na- norods （AuNRs） and negatively charged superoxide dismutase （SOD） from their aqueous solution...Based on the layer-by-layer self-assembly of positively charged cetyltrimethylammonium bromide （CTAB） wrapped gold na- norods （AuNRs） and negatively charged superoxide dismutase （SOD） from their aqueous solutions on cysteine modified gold electrode （Cys/Au）, a third generation electrochemical biosensor （（SOD/AuNRs）2/Cys/Au） for superoxide anion （02＂-） was developed. The two layers assembly of SOD/AuNRs can significantly enhance the direct electron transfer between SOD and the electrode. The functional enzymatic activities of the SOD offer an electrochemical approach to the determination of 02＂-. In the reductive regions, the proposed sensor exhibits excellent analytical performances, such as wide linear range （200 nM to 0.2 mM O2-）, low detection limit （100 nM O2-）, high sensitivity （22.11 nA cm-2 μM-1）, short response time （less than 5 s）, good stability and reproducibility, while no obvious interferences are caused by commonly met interfering species including hydrogen peroxide （H202）, uric acid （UA） and ascorbic acid （AA）.展开更多
Temporal oscillations of the bromate-4-aminophenol system have been studied in the presence of four different catalysts： tris（1,10-phenanthroline）iron（Ⅱ） sulfate （ferroin）, Ce（Ⅲ）, Mn（Ⅱ）, and Fe（Ⅱ）. Tr...Temporal oscillations of the bromate-4-aminophenol system have been studied in the presence of four different catalysts： tris（1,10-phenanthroline）iron（Ⅱ） sulfate （ferroin）, Ce（Ⅲ）, Mn（Ⅱ）, and Fe（Ⅱ）. Transient temporal oscillations were observed in the four catalyzed systems when the reactions were conducted in a stirred batch reactor. The induction time was prolonged by the presence of ferroin, but it was shortened in the Ce（Ⅲ）- and Mn（Ⅱ）-catalyzed systems. On the other hand, the number of peaks was significantly decreased in the presence of ferroin. The development of oscillatory behaviour was found to be more sensitive to the ratio of bromate and 4-aminophenol concentration than to their absolute concentrations. The reaction rates of 4-aminophenol with Ce（IV） and 4-aminophenol with ferritin were measured directly by spectroscopic methods in a sulfuric acid medium.展开更多
基金Acknowledgements This work was supported by National Basic Research Program of China （973 Program No. 2009CB930703） and National Natural Science Foundation of China （No. 21033007）. We thank Dr. Jiawei Yan, Yongli Zheng, and Haixin Lin for helpful discussion. We also thank Zhaobin Chen for ICP-AES measurements.
文摘The appropriate choice of chemical composition of a metallic precursor, which produces the basic structure units in the growth process of nanocrystals, is a high priority in the synthesis of metal--especially Au--nanoparticles. In the present work, Au seeds （prepared by the reduction of Au3＋ solution with NaBI~ in the presence of cetyltrimethylammonium bromide （CTAB）） have been used to initiate the growth of Au nanoparticles from two different Au precursors. When an aqueous Au＋ solution prepared in the presence of CTAB micelles was treated with ascorbic acid in the presence of the gold seeds, a high yield （up to 92%） of gold nanoparticles was obtained. By varying the volume of the seed solution with a fixed amount of Au＋, we can effectively control the morphological transformation of the resulting Au nanoparticles from cubes to octahedra. When an aqueous Au3＋ solution was prepared in the presence of CTAB micelles and treated with ascorbic acid in the presence of the gold seeds, smaller yields of Au nanoparticles were obtained. A preliminary growth mechanism has been proposed based on the changes induced by varying the amount of ascorbic acid and the ratio of the concentration of Au＊ to the number of seeds.
基金supported by the National Natural Science Foundation of China (20805013, 20905024&21075031)the National Basic Research Program of China (2009CB421601 & 2011CB911002)the Natural Science Foundation of Hunan Province (09JJ4006 & 09JJ4007)
文摘Based on the layer-by-layer self-assembly of positively charged cetyltrimethylammonium bromide （CTAB） wrapped gold na- norods （AuNRs） and negatively charged superoxide dismutase （SOD） from their aqueous solutions on cysteine modified gold electrode （Cys/Au）, a third generation electrochemical biosensor （（SOD/AuNRs）2/Cys/Au） for superoxide anion （02＂-） was developed. The two layers assembly of SOD/AuNRs can significantly enhance the direct electron transfer between SOD and the electrode. The functional enzymatic activities of the SOD offer an electrochemical approach to the determination of 02＂-. In the reductive regions, the proposed sensor exhibits excellent analytical performances, such as wide linear range （200 nM to 0.2 mM O2-）, low detection limit （100 nM O2-）, high sensitivity （22.11 nA cm-2 μM-1）, short response time （less than 5 s）, good stability and reproducibility, while no obvious interferences are caused by commonly met interfering species including hydrogen peroxide （H202）, uric acid （UA） and ascorbic acid （AA）.
基金supported by the Natural Science and Engineering Research Council (NSERC),Canada,the National Natural Science Foundation ofChina (21003010)the Doctoral Fund of the Ministry of Education of China (20101101120032)+1 种基金the China Postdoctoral Science Foundation(20100470558)the Excellent Young Scholars Research Fund of Beijing Institute of Technology (2009 Y1017)
文摘Temporal oscillations of the bromate-4-aminophenol system have been studied in the presence of four different catalysts： tris（1,10-phenanthroline）iron（Ⅱ） sulfate （ferroin）, Ce（Ⅲ）, Mn（Ⅱ）, and Fe（Ⅱ）. Transient temporal oscillations were observed in the four catalyzed systems when the reactions were conducted in a stirred batch reactor. The induction time was prolonged by the presence of ferroin, but it was shortened in the Ce（Ⅲ）- and Mn（Ⅱ）-catalyzed systems. On the other hand, the number of peaks was significantly decreased in the presence of ferroin. The development of oscillatory behaviour was found to be more sensitive to the ratio of bromate and 4-aminophenol concentration than to their absolute concentrations. The reaction rates of 4-aminophenol with Ce（IV） and 4-aminophenol with ferritin were measured directly by spectroscopic methods in a sulfuric acid medium.
