基于离心技术的金纳米粒子表面清洁方法和机理研究

本文发展了一种基于离心技术的清洗金纳米八面体表面十六烷基三甲基溴化铵(CTAB)吸附物的有效方法.选择合适的离心转速和离心次数,可以驱除金纳米八面体表面的CTAB分子.通过热失重分析、表面增强拉曼光谱和傅里叶红外光谱表征可以推测,金纳米八面体经合适的离心清洗后,表面残留的少量CTAB分子通过疏水作用由烷基长链与金表面形成(亚)单层吸附,同时,与金表面有强相互作用的溴离子发生脱附.溶剂水对CTAB的稀释在离心清洗金纳米八面体表面的过程中发挥着重要作用.金纳米粒子在离心场中的高速运动导致粒子周围双电层发生极化,极化双电层内产生的局部液流引起双电层内物质交换从而也影响了金纳米八面体表面的清洗效果.金纳米八面体在硫酸溶液和碱性硝酸铅溶液中的电化学研究表明,经过离心清洗的金纳米八面体可以直接应用于单晶电化学研究.

A cleaning method with centrifugation for removing surfactants from gold nanoparticles and its mechanism

We developed an effective cleaning method based on a centrifugal effect to remove the surfactant cetyltrimethylammonium bromide（CTAB） from the surfaces of noble metallic such as 50 nm gold nano-octahedrons. The cleaned surface can be obtained by choosing the proper centrifugal speed and times under the appropriate temperature and humidity conditions. Thermal gravimetric analysis（TGA）, surface-enhanced Raman scattering（SERS） and Fourier transform infrared spectroscopy（FTIR） are conducted to systematically investigate the adsorbed CTAB layer structure on gold nano-octahedrons surface. The results indicate that CTAB molecules bind to gold surface via their long hydrophobic tail and form a（sub） monolayer on the gold surface, and the bromide ions chemisorbed at the gold surface are desorbed. The dilution effect of water can act on the transformation of CTAB on gold surface during the cleaning procedure. Additionally, a localized solution flow is induced by the polarization of the electrical double layer gold nanoparticle with high speed in a centrifugal field. Mass transfer around the gold nanoparticle is occurring, and thus to be the influences on the surface cleaning of gold nanoparticles. We also performed the cyclic voltammetry（CV） studies in 0.5 mol/L sulfuric acid solution and alkaline solution contained with 0.1 mol/L NaOH ＋ 1.0 m mol/L Pb（NO3）2, used the gold nano-octahedrons film as electrode. The results suggest that, after the cleaning procedures with centrifugation, the surface of gold nano-octahedrons can be purified enough to be used for electrochemical studies instead of traditional gold（111） facets.