1. School of Pharmaceutical Science, Southern Medical University, Guangzhou 510515, China 2. State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science and Technology,Wuhan 430074, China
Abstract：Colloidal silver nanoparticles were synthesized in water-in-oil microemulsion using silver nitrate solubilized in the water core of a microemulsion as source of silver ions, hydrazine hydrate solubilized in the water core of another one as reducing agent, cyclohexane as the continuous phase, and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as the surfactant. The main factors affecting the formation of silver nanoparticles were systematically studied. Ultraviolet-visible (UV-Vis) spectra were used for analyzing the effects of reaction parameters, including the type of reducing agents, the molar ratio of water to surfactant and the concentration of AgNO3 and AOT and so on, on the formation of silver nanoparticles. Original results for the controllable synthesis of silver nanoparticles were obtained when the synthesis proceeded in AOT-cyclohexane-AgNO3 microemulsion. The UV-Vis spectra of silver sols formed in the microemulsion with various parameters were studied systematically. The results show that the amount and average size of the obtained nanoparticles obviously depend on the above parameters. When the concentration of AgNO3 is lower, smaller silver nanoparticles are easy to form by increasing the concentration of AgNO3 appropriately. The higher W value was found to form larger numbers of silver nanoparticles with larger particle size. Compared to the solubility of NaBH4 in AOT reverse micelles, hydrazine hydrate is well soluble in these micelles, and thus it is favorable to reduce the silver ions solubilized in the water core of AOT-cyclohexane-AgNO3 microemulsion. The increase in the concentration of AOT induces an increase in the number of AOT micelles and a decrease in the molar ratio of water to surfactant. As a result, the solubilization capacity of reactants in the micelles increases and the radii of the micelles decrease. That is to say, with the increase in AOT concentration, the amount of the formed nanoparticles increases and the average size of the particles decreases.
[1] SONG Yong-hui, LIANG Gong-ying, ZHANG Qiu-li, et al(宋永辉, 梁工英, 张秋利, 等). Rare Metal Materials and Engineering(稀有金属材料与工程), 2007, 36(4): 709. [2] Taleb A, Russier V, Courty A, et al. Appl. Surf. Sci., 2000, 162-163(1-4): 655. [3] Zhang W Z, Qiao X L, Chen J G. Mater. Sci. Eng., B, 2007, 142(1): 1. [4] Petit C, Lixon P, Pileni M P. J. Phys. Chem., 1993, 97(49): 12974. [5] Zhang W Z, Qiao X L, Chen J G. Colloids Surf. A Physicochem. Eng. Aspects, 2007, 299(1-3): 22. [6] SI Min-zhen, FANG Yan, PENG Jia-lin, et al(司民真, 方 炎, 彭家林, 等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2007, 27(5): 948. [7] ZHONG Fu-xin, JIANG Zhi-liang, LI Fang, et al(钟福新, 蒋治良, 李 芳, 等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2000, 20(5): 724. [8] QIN Ai-miao, JIANG Zhi-liang, LIU Qing-ye, et al(覃爱苗, 蒋治良, 刘庆业, 等). Chin. J. Anal. Chem.(分析化学), 2002, 30(10): 1254. [9] YUAN Wei-en, JIANG Zhi-liang, PAN Hong-cheng, et al(袁伟恩, 蒋治良, 潘宏程, 等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2005, 25(6): 920. [10] ZHENG Ai-guo, WANG Du-jin, XU Yi-zhuang, et al(郑爱国, 王笃金, 徐怡庄, 等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2003, 23(6): 1132. [11] Sheu E Y, Chen S H. J. Phys. Chem., 1988, 92(15): 4466. [12] He B L, Tan J J, Kong Y L, et al. J. Mol. Catal. A Chem., 2004, 221(1-2): 121. [13] Zheng M P, Gu M Y, Jin Y P, et al. Mater. Res. Bull., 2001, 36(5-6): 853. [14] Liz-Marzán L M, Lado-Tourino I. Langmuir, 1996, 12(15): 3585. [15] Koper G J M, Sager W F C, Smeets J, et al. J. Phys. Chem., 1995, 99(35): 13291. [16] Zhang W Z, Qiao X L, Chen J G. Chem. Phys., 2006, 330(3): 495.
