Basu Soumen, Ghosh Sujit Kumar, Kundu Subrata, Panigrahi Sudipa, Praharaj Snigdhamayee, Pande Surojit, Jana Subhra, Pal Tarasankar
Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India.
J Colloid Interface Sci. 2007 Sep 15;313(2):724-34. doi: 10.1016/j.jcis.2007.04.069. Epub 2007 May 3.
Gold nanoparticles of variable sizes have been prepared by reducing HAuCl(4) with trisodium citrate by Frens' method. It has been found that the gold particles under consideration produce well-ordered aggregates upon interaction with a biomolecule, glutathione in variable acidic pH condition and exhibit pronounced changes in their optical properties arising due to electromagnetic interaction in the close-packed assembly. The effect of nanoparticle size on the nature of aggregation as well as the variation in the optical response due to variable degree of interparticle coupling effects amongst the gold particles have been investigated. The optical properties of the gold aggregates have been accounted in the light of Maxwell-Garnett effective medium theory considering the changes in the filling factor in different aggregates produced by variable sizes of gold colloids. The aggregates have been characterized by UV-vis spectroscopy, FTIR, Raman, XRD and TEM studies. It has been observed that a new peak appearing at a longer wavelength intensifies and shifts further to the red from the original peak position depends on the particle size, concentration of glutathione and pH of the solution. On the basis of the first appearance of a clearly defined new peak at longer wavelength, a higher sensitivity of glutathione detection has been achieved with gold nanoparticles of larger dimension.
采用弗伦斯法，通过用柠檬酸钠还原氯金酸（HAuCl₄）制备了不同尺寸的金纳米颗粒。研究发现，所研究的金颗粒在可变酸性pH条件下与生物分子谷胱甘肽相互作用时会产生有序的聚集体，并由于紧密堆积组装中的电磁相互作用而使其光学性质发生显著变化。研究了纳米颗粒尺寸对聚集性质的影响以及由于金颗粒间不同程度的颗粒间耦合效应导致的光学响应变化。考虑到由不同尺寸的金胶体产生的不同聚集体中填充因子的变化，根据麦克斯韦-加尼特有效介质理论对金聚集体的光学性质进行了解释。通过紫外-可见光谱、傅里叶变换红外光谱、拉曼光谱、X射线衍射和透射电子显微镜研究对聚集体进行了表征。观察到在较长波长处出现的一个新峰强度增加，并从原始峰位置进一步向红色移动，这取决于颗粒尺寸、谷胱甘肽浓度和溶液的pH值。基于在较长波长处首次出现清晰定义的新峰，使用较大尺寸的金纳米颗粒实现了对谷胱甘肽检测的更高灵敏度。
