Kenan Laboratories of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Anal Chem. 2009 Aug 15;81(16):6960-5. doi: 10.1021/ac9010364.
The robust, irreversible adsorption of omega-ferrocene hexanethiolate-protected gold nanoparticles (composition ca. {Au(225)(SC6Fc)(43)}) on electrodes provides an opportunity to investigate their submonolayer and monolayer films in nanoparticle-free solutions. Observations of nanoparticle adsorption on unmodified electrodes are extended here to Au electrodes having more explicitly controlled surfaces, namely self-assembled monolayers (SAMs) of alkanethiolates with omega-sulfonate, carboxylate, and methyl termini, and in different Bu(4)N(+)X(-) electrolyte (X(-) = C(7)H(7)SO(3)(-), ClO(4)(-), CF(3)SO(3)(-), PF(6)(-), NO(3)(-)) solutions in CH(2)Cl(2). The nanoparticle surface coverage (Gamma(NP)) and the stability of the adsorbed nanoparticle film to repeated ferrocene/ferrocenium redox cycling decrease in the order of sulfonate > carboxylate > methyl terminated SAM, with increasing hydrophobicity of X(-) and with increasing alkyl chain length. The results are consistent with the proposal that the strong surface adsorption is jointly associated with the polyfunctional character of the nanoparticles, analogous to entropically driven adsorptions of polymeric ions on charged surfaces, and with lateral, ion-bridged nanoparticle-nanoparticle interactions.
具有稳定性和不可逆性的 ω-二茂铁己硫醇保护的金纳米粒子（组成约为{Au(225)(SC6Fc)(43)}}）在电极上的吸附为研究其亚单层和单层膜在无纳米粒子溶液中的性质提供了机会。在这里，我们将纳米粒子在未经修饰的电极上的吸附扩展到具有更明确控制表面的 Au 电极上，即具有 ω-磺酸酯、羧酸酯和甲基末端的烷硫醇自组装单层（SAM），以及在不同的 Bu(4)N(+)X(-)（X(-) = C(7)H(7)SO(3)(-), ClO(4)(-), CF(3)SO(3)(-), PF(6)(-), NO(3)(-))电解质在 CH(2)Cl(2)中的溶液中。纳米粒子的表面覆盖率（Gamma(NP)）和吸附纳米粒子膜对重复的二茂铁/二茂铁氧化还原循环的稳定性按磺酸酯>羧酸酯>甲基末端 SAM 的顺序降低，其中 X(-)的疏水性增加，烷基链长度增加。结果与以下假设一致，即强的表面吸附与纳米粒子的多官能团性质有关，类似于聚合物离子在带电表面上的熵驱动吸附，以及纳米粒子之间的横向、离子桥接相互作用。
