中文摘要：

该文以微米级Pt-SiO2型Janus颗粒催化分解H2O2体系为研究对象，用MicroPTV技术观测Janus微颗粒在纯水及不同浓度（2．5％、5％和10％）H2O2溶液中的自驱动运动。实验结果表明：与经典布朗运动给出的定常扩散系数不同，Janus颗粒的有效扩散系数Deff 与统计时间间隔有关：在短时间间隔内Deff线性增加，随后随时间间隔增长Deff趋于一稳定值，该值可达纯水中同粒径颗粒扩散系数的10—100倍。Deff由线性增加转变为稳定的特征时间τR随粒径增大而增大，与H2O2溶液浓度的关系不明显。进一步考察颗粒均方位移△L^2、位矢转角γ的统计变化规律，清楚看出Janus颗粒的推进扩散到类布朗运动形式的转变。通过位矢转角γ的概率分布图可以定量确定τR。

英文摘要：

In this paper, micron-sized Pt-SiO2 Janus particles that utilize the asymmetrical catalytic decomposition reaction are chosen. The autonomous movement of Janus particles under water and the H2O2 solution with different concentrations （2.5%, 5% and 10%） is investigated through Micro-PTV platform. The experiment results show that the values of effective diffusion coefficient Deff of Janus particles are associated with the statistic time interval. In a short time interval, Deftt- increases linearly as the time interval increases; however, for a long enough time interval, Deft tends to a steady constant, which is about ten to onehundred times higher than that of in pure water with the same particle size. This behaviour about Janus particle is quiet different from the classical Brownian motion, where diffusion coefficient is unchanged. The characteristic time τR, from which the tendency of Deff turns to change from linear increase to steady platform, increases with the increase of particle size, but, the dependence of τR on the concentration of H2O2 solution is not so obvious. Furthermore, the mean squared displacement △L^2 and directional angle γ of Janus particles are investigated to obtain their statistic law. It is clear to show the conversion of Janus particles＇ movement from self-propulsion to Brownian-like motion. In the graphs about the probability distribution of directional angle, the characteristic time τR can be decided quantitatively.