生物合成法主要是利用微生物和生物提取物合成金属纳米颗粒，以前的研究工作中，利用柠檬草和芦荟的植物提取物合成了大量的金纳米片。金纳米线在微电子学、光电子学、纳米电子器件和其它领域都有其应用价值。本文报道了利用用紫色光养菌R. capsulata的细胞提取物来合成金纳米线材料的研究，提取物中的蛋白质可以作为还原剂，保持一定的还原剂的量，通过改变氯金酸的量，从而改变氧化剂与还原剂的配比，可以显著的改变氯金酸的还原动力学，除了可以生成球形的金纳米颗粒外，还能够选择性合成网络状的金纳米线这种非球形的金纳米结构。整个过程无需附加的稳定剂或者表面吸附剂等辅助的功能分子，而且反应条件温和，反应过程简单，生成的金纳米线表面还包覆有蛋白质，有利于近一步的应用。
Shiying He, Yu Zhang, Zhirui Guo, and Ning Gu. Biological Synthesis of Gold Nanowires Using Extract of Rhodopseudomonas capsulata , Biotechnol. Prog. 2008, 24, 476−480
Biological synthesis of gold nanowires using extract of bacteria Rhodopseudomonas capsulate
An environmentally friendly method using the cell-free extract (CFE) of bacteria Rhodopseudomonas capsulate was proposed to synthesize gold nanowires with a network structure in this paper. This procedure offers control over the shapes of gold nanoparticles with the change of HAuCl4 concentration. The CFE solutions were added with different concentration of HAuCl4 resulting in the bioreduction of gold ions and biosynthesis of morphologies of gold nanostructures. It is probably that proteins acted as the major biomolecules involved in the bioreduction and synthesis of gold nanoparticles. At a lower concentration of gold ions, exclusively spherical gold nanoparticles with size range from 10 to 20 nm produced whereas gold nanowires with a network structure formed at the higher concentration of gold ions in the aqueous solution. This method is expected to be applicable to the synthesis of other metallic nanowires such as silver and platinum. Even other anisotropic metal nanostructures are expected using the biosynthetic methods.
Figure 1. UV-visible spectra of gold nanoparticles prepared by the CFE at the 2.5×10-4 M HAuCl4. The inset shows the test tube of gold nanoparticles solution formed at the end of the reaction.
Figure 2. (A) Representative TEM image of gold nanoparticles produced by CFE at the 2.5×10-4 M HAuCl4 concentration. (B) SAED pattern from gold nanoparticles corresponding to A.
Figure 3. (A) FTIR spectrum of gold nanoparticles synthesized in the CFE. (B) Spot profile EDAX spectrum recorded from gold nanoparticles synthesized in the CFE. (C) SDS-PAGE analysis showing the proteins in the CFE. Lane 1 shows the standard protein molecular-weight markers with molecular weights given in kilo Daltons. Lane 2 shows the proteins in the CFE and their approximate molecular weights.
Figure 4. UV-visible spectra of gold nanowiress prepared by the CFE at the 5.0×10-4 M HAuCl4. The inset shows the test tube of gold nanowires solution formed at the end of the reaction.
Figure 5. (A) Representative TEM image of gold nanoparticles produced by CFE at the 5×10-4 M HAuCl4 concentration. Inset is SAED pattern from gold nanoparticles corresponding to (A). (B) Higher magnification TEM image of nanowires
Scheme 1. Schematic growth mechanism of gold nanowires with network structure.
