Reverse Size-Dependent Electrooxidation of Gold Nanoparticles Coated with Alkanethiol Self-Assembled Monolayers
Reverse Size-Dependent Electrooxidation of Gold Nanoparticles Coated with Alkanethiol Self-Assembled Monolayers
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DOI：
10.1021/acs.jpcc.0c10173
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发表时间：
2021-01-26
影响因子：
3.7
通讯作者：
Zamborini, Francis P.
中科院分区：
文献类型：
--
作者：
Mainali, Badri P.;Pattadar, Dhruba K.;Zamborini, Francis P.
弱稳定的柠檬酸盐涂覆的Au和其他球形金属纳米颗粒（NPs）的氧化电位负移，负移的量与1/半径成比例，这是由于热力学标准电位的尺寸依赖性负移，这与NPs的表面积与体积比（SA/V）随着尺寸减小而增加有关。强结合的稳定剂，如烷硫醇盐，通过防止溶液中的聚集提供稳定性，但也强烈影响金属NP的氧化电位。在本文中，循环伏安法（CV）显示，当用丁硫醇（C4 S）、癸硫醇（C10 S）和十六烷硫醇（C16 S）配体涂覆时，对于4.1 +/- 0.7、15.1 +/- 1.3和50.3 +/- 1.7 nm直径的Au NPs，Br-对Au的氧化溶出显著受阻。抗氧化性随着链长的增加而增加，这与平面二维（2D）Au表面上的大量研究一致。当比较尺寸时，与用相同硫醇盐涂覆的15.1和50.3 nm直径Au NP相比，4.1 nm烷硫醇盐涂覆的Au NP显示出更大的抗氧化剥离性。计时库仑法（CC）实验表明，与4.1 nm Au NP相比，15.1和50.3 nm直径的硫醇盐涂覆的Au NP在1.0 V下相对于Ag/AgCl在1000 s内在酸性Br-中氧化到更大程度。尽管4.1 nm Au NP的SA/V高得多，但与C4 S涂覆的4.1 nm Au NP相比，Au从C4 S涂覆的50.3 nm Au NP中溶解的量几乎是其4倍。因此，Au NP对氧化的稳定性对于硫醇盐涂覆的Au NP具有独特的反向尺寸依赖性，其中氧化程度随着尺寸的增加而增加，这与对于弱稳定或裸露的Au NP观察到的趋势相反。
The oxidation potential of weakly stabilized, citrate-coated Au and other spherical metal nanoparticles (NPs) shifts negative by an amount proportional to 1/radius due to a size-dependent negative shift in the thermodynamic standard potential, which is related to the increase in surface-area-to-volume ratio (SA/V) of the NPs with decreasing size. Strongly bound stabilizers, such as alkanethiolates, provide stability by preventing aggregation in solution but also strongly influence the oxidation potential of the metal NPs. In this paper, cyclic voltammetry (CV) shows that the oxidative stripping of Au by Br- is hindered significantly for 4.1 +/- 0.7, 15.1 +/- 1.3, and 50.3 +/- 1.7 nm diameter Au NPs when coated with butanethiolate (C4S), decanethiolate (C10S), and hexadecanethiolate (C16S) ligands. The resistance to oxidation increases with increasing chain length, consistent with the numerous studies on planar two-dimensional (2D) Au surfaces. When sizes are compared, the 4.1 nm alkanethiolate-coated Au NPs show greater resistance to oxidative stripping compared to the 15.1 and 50.3 nm diameter Au NPs coated with the same thiolates. Chronocoulometry (CC) experiments show that 15.1 and 50.3 nm diameter thiolate-coated Au NPs oxidize to a much greater extent in acidic Br- within 1000 s at 1.0 V vs Ag/AgCl compared to 4.1 nm Au NPs. Almost 4 times more Au dissolves from C4S-coated 50.3 nm Au NPs as compared to C4S-coated 4.1 nm Au NPs, despite the much higher SA/V for the 4.1 nm Au NPs. The stability of the Au NPs against oxidation therefore has a unique reverse size dependence for thiolate-coated Au NPs, where the extent of oxidation increases with increasing size, which is opposite from the trend observed for weakly stabilized or bare Au NPs.