Moore Tibbetts Katharine, Tangeysh Behzad, Odhner Johanan H, Levis Robert J
Department of Chemistry and Center for Advanced Photonics Research, Temple University , Philadelphia, Pennsylvania 19122, United States.
J Phys Chem A. 2016 May 26;120(20):3562-9. doi: 10.1021/acs.jpca.6b03163. Epub 2016 May 12.
Direct, multiphoton photolysis of aqueous metal complexes is found to play an important role in the formation of nanoparticles in solution by ultrafast laser irradiation. In situ absorption spectroscopy of aqueous AuCl4 reveals two mechanisms of Au(0) nucleation: (1) direct multiphoton photolysis of AuCl4 and (2) radical-mediated reduction of AuCl4 upon multiphoton photolysis of water. Measurement of the reaction kinetics as a function of solution pH reveals zeroth-, first-, and second-order components. The radical-mediated process is found to be zeroth-order in AuCl4 under acidic conditions, where the reaction rate is limited by the production of reactive radical species from water during each laser shot. Multiphoton photolysis is found to be first order in AuCl4 at all pHs, whereas the autocatalytic reaction with H2O2, the photolytic reaction product of water, is second order.
研究发现，金属配合物水溶液的直接多光子光解在超快激光辐照下溶液中纳米颗粒的形成过程中起着重要作用。[AuCl4]⁻水溶液的原位吸收光谱揭示了Au(0)成核的两种机制：(1)[AuCl4]⁻的直接多光子光解；(2)水多光子光解后自由基介导的[AuCl4]⁻还原。作为溶液pH函数的反应动力学测量揭示了零级、一级和二级反应组分。发现在酸性条件下，自由基介导的过程在[AuCl4]⁻中为零级，此时反应速率受每次激光脉冲期间水中活性自由基物种产生的限制。发现在所有pH值下，多光子光解在[AuCl4]⁻中为一级，而与水的光解产物H2O2的自催化反应为二级。
