Laboratory for Sustainable Technology, School of Chemical and Biomolecular Engineering, University of Sydney, NSW 2006, Australia.
J Colloid Interface Sci. 2011 Jan 15;353(2):433-44. doi: 10.1016/j.jcis.2010.09.088. Epub 2010 Oct 25.
The biogenic synthesis of metal nanomaterials offers an environmentally benign alternative to the traditional chemical synthesis routes. Colloidal silver (Ag) nanoparticles were synthesized by reacting aqueous AgNO(3) with Medicago sativa seed exudates under non-photomediated conditions. Upon contact, rapid reduction of Ag(+) ions was observed in <1 min with Ag nanoparticle formation reaching 90% completion in <50 min. Effect of Ag concentration, quantity of exudate and pH on the particle size and shape were investigated. At [Ag(+)]=0.01 M and 30°C, largely spherical nanoparticles with diameters in the range of 5-51 nm were generated, while flower-like particle clusters (mean size=104 nm) were observed on treatment at higher Ag concentrations. Pre-dilution of the exudate induced the formation of single-crystalline Ag nanoplates, forming hexagonal particles and nanotriangles with edge lengths of 86-108 nm, while pH adjustment to 11 resulted in monodisperse Ag nanoparticles with an average size of 12 nm. Repeated centrifugation and redispersion enhanced the percentage of nanoplates from 10% to 75% in solution. The kinetics of nanoparticle formation were monitored using ultraviolet-visible spectroscopy and the Ag products were characterized using transmission electron microscopy, selected-area electron diffraction, scanning electron microscopy, X-ray powder diffraction, and atomic force microscopy. X-ray photoelectron spectroscopy was used to investigate the elements and chemical environment in the top layers of the as-synthesized Ag nanoparticles, while the metabolites in the exudate were analyzed using gas chromatography-mass spectroscopy. To our knowledge, this is the first account of M. sativa seed exudate assisted synthesis and stabilization of biogenic Ag nanoparticles; the nanoplates are notably smaller and better faceted compared with those synthesized by vascular plant extracts previously reported. Stabilized films of exudate synthesized Ag nanoparticles were effective anti-bacterial agents.
生物合成金属纳米材料为传统的化学合成路线提供了一种环境友好的替代方法。在非光介导条件下，通过将水相中的 AgNO3 与 Medicago sativa 种子分泌物反应，合成了胶体银（Ag）纳米粒子。接触后，在 <1 分钟内观察到 Ag+离子的快速还原，Ag 纳米颗粒的形成在 <50 分钟内达到 90%的完成度。研究了 Ag 浓度、分泌物的量和 pH 值对颗粒尺寸和形状的影响。在 [Ag+] = 0.01 M 和 30°C 下，生成了直径在 5-51nm 范围内的大致球形纳米粒子，而在较高 Ag 浓度下处理则观察到花状粒子簇（平均尺寸=104nm）。分泌物的预稀释诱导单晶 Ag 纳米板的形成，形成具有 86-108nm 边长的六边形粒子和纳米三角形，而 pH 值调节至 11 导致具有 12nm 平均尺寸的单分散 Ag 纳米粒子。重复离心和再分散可将溶液中纳米板的百分比从 10%提高到 75%。使用紫外-可见光谱监测纳米颗粒形成的动力学，并使用透射电子显微镜、选区电子衍射、扫描电子显微镜、X 射线粉末衍射和原子力显微镜对 Ag 产物进行了表征。X 射线光电子能谱用于研究合成的 Ag 纳米颗粒顶层的元素和化学环境，而分泌物中的代谢物则使用气相色谱-质谱进行分析。据我们所知，这是首次报道 Medicago sativa 种子分泌物辅助合成和稳定生物生成的 Ag 纳米粒子；与以前报道的血管植物提取物合成的纳米板相比，纳米板更小且具有更好的面。由分泌物合成的 Ag 纳米粒子稳定的薄膜是有效的抗菌剂。
