Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, USA.
Anal Chem. 2010 Jul 1;82(13):5844-50. doi: 10.1021/ac101021q.
Here we describe the electrochemical oxidation of an assembly of gold nanoparticles (Au NPs) attached to glass/indium-tin-oxide (ITO) electrodes as a function of particle size. We synthesized Au NP arrays with NP diameters ranging from 8 to 250 nm by electrodeposition of Au from HAuCl(4) in H(2)SO(4) at potentials of -0.2 to 0.8 V versus Ag/AgCl using chronocoulometry to keep the amount of Au deposited constant. The average Au NP size increased with increasing deposition potential. The chemical reduction of HAuCl(4) by NaBH(4) in trisodium citrate solution led to 4 nm average diameter Au NPs, which we chemisorbed to the glass/ITO electrode. Linear sweep voltammograms (LSVs) obtained on the glass/ITO/Au NP (4 to 250 nm) electrodes (with a constant coverage of Au in terms of Au atoms per cm(2)) from 0.5 to 1.1 V in 0.01 M potassium bromide plus 0.1 M HClO(4) showed a positive shift in oxidation potential from 734 +/- 1 mV to 913 +/- 19 mV with increasing Au NP diameter. The shift agrees qualitatively with that predicted by a shift in the redox potential based on a difference in free energy associated with a change in surface energy as a function of particle size. On the basis of the charge during Au deposition versus the charge during oxidation, the oxidation process produces a mixture of Au(III)Br(4)(-) (25%) and Au(I)Br(2)(-) (75%). A glass/ITO electrode coated with a mixture of 4 and 250 nm Au NPs revealed 2 oxidation peaks, consistent with the two Au NP size populations present on the surface.
我们描述了附着在玻璃/铟锡氧化物（ITO）电极上的金纳米粒子（Au NPs）组装体的电化学氧化作用，其功能取决于粒子的大小。我们通过在硫酸中从 HAuCl4 进行电沉积，使用计时库仑法将 Au 沉积量保持恒定，在-0.2 至 0.8 V 相对于 Ag/AgCl 的电势下，合成了具有 8 至 250nm 直径的 Au NP 阵列。Au NP 的平均尺寸随沉积电势的增加而增加。在三钠柠檬酸钠溶液中由 NaBH4 对 HAuCl4 的化学还原导致形成 4nm 平均直径的 Au NPs，我们将其化学吸附到玻璃/ITO 电极上。在 0.01 M 溴化钾加 0.1 M HClO4 中，从 0.5 至 1.1 V 对玻璃/ITO/Au NP（4 至 250nm）电极（以 Au 原子每 cm2 的 Au 覆盖率为常数）进行的线性扫描伏安法（LSV）显示，随着 Au NP 直径的增加，氧化电势从 734±1 mV 正移至 913±19 mV。该偏移与基于与表面能变化相关的自由能差异的氧化还原电势的偏移所预测的定性一致。基于 Au 沉积期间的电荷与氧化期间的电荷，氧化过程产生 Au(III)Br4(-)(25%)和 Au(I)Br2(-)(75%)的混合物。涂有 4nm 和 250nm Au NPs 混合物的玻璃/ITO 电极显示出 2 个氧化峰，这与表面上存在的两种 Au NP 尺寸群体一致。
