Xu Weilin, Kong Jason S, Yeh Yun-Ting E, Chen Peng
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
Nat Mater. 2008 Dec;7(12):992-6. doi: 10.1038/nmat2319. Epub 2008 Nov 9.
Nanoparticles are important catalysts for many chemical transformations. However, owing to their structural dispersions, heterogeneous distribution of surface sites and surface restructuring dynamics, nanoparticles are intrinsically heterogeneous and challenging to characterize in ensemble measurements. Using a single-nanoparticle single-turnover approach, we study the redox catalysis of individual colloidal Au nanoparticles in solution, using single-molecule detection of fluorogenic reactions. We find that for product generation, all Au nanoparticles follow a Langmuir-Hinshelwood mechanism but with heterogeneous reactivity; and for product dissociation, three nanoparticle subpopulations are present that show heterogeneous reactivity between multiple dissociation pathways with distinct kinetics. Correlation analyses of single-turnover waiting times further reveal activity fluctuations of individual Au nanoparticles, attributable to both catalysis-induced and spontaneous dynamic surface restructuring that occurs at different timescales at the surface catalytic and product docking sites. The results exemplify the power of the single-molecule approach in revealing the interplay of catalysis, heterogeneous reactivity and surface structural dynamics in nanocatalysis.
纳米颗粒是许多化学转化过程中的重要催化剂。然而，由于其结构分散性、表面位点的不均匀分布以及表面重构动力学，纳米颗粒本质上是不均匀的，并且在整体测量中难以表征。我们采用单纳米颗粒单周转方法，通过对荧光反应的单分子检测，研究了溶液中单个胶体金纳米颗粒的氧化还原催化作用。我们发现，在产物生成方面，所有金纳米颗粒都遵循朗缪尔-欣谢尔伍德机制，但反应活性存在异质性；在产物解离方面，存在三个纳米颗粒亚群，它们在多种具有不同动力学的解离途径之间表现出异质反应性。单周转等待时间的相关性分析进一步揭示了单个金纳米颗粒的活性波动，这归因于在表面催化和产物对接位点不同时间尺度上发生的催化诱导和自发动态表面重构。这些结果例证了单分子方法在揭示纳米催化中催化作用、异质反应性和表面结构动力学之间相互作用方面的强大能力。
