Wang Yang, Hernandez Rose M, Bartlett David J, Bingham Julia M, Kline Timothy R, Sen Ayusman, Mallouk Thomas E
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Langmuir. 2006 Dec 5;22(25):10451-6. doi: 10.1021/la0615950.
Bimetallic nanorods are propelled in aqueous solutions by the catalytic decomposition of hydrogen peroxide to oxygen and water. Several mechanisms (interfacial tension gradients, bubble recoil, viscous Brownian ratchet, self-electrophoresis) have been proposed for the transduction of chemical to mechanical energy in this system. From Tafel plots of anodic and cathodic hydrogen peroxide reactions at various metal (Au, Pt, Rh, Ni, Ru, and Pd) ultramicroelectrodes, we determine the potential at which the anodic and cathodic reaction rates are equal for each metal. These measurements allow one to predict the direction of motion of all possible bimetallic combinations according to the bipolar electrochemical (or self-electrophoretic) mechanism. These predictions are consistent with the observed direction of motion in all cases studied, providing strong support for the mechanism. We also find that segmented nanorods with one Au end and one poly(pyrrole) end containing catalase, an enzyme that decomposes hydrogen peroxide nonelectrochemically, perform the overall catalytic reaction at a rate similar to that of nanorods containing Au and Pt segments. However, in this case there is no observed axial movement, again supporting the bipolar electrochemical propulsion mechanism for bimetallic nanorods.
双金属纳米棒在水溶液中通过过氧化氢催化分解为氧气和水而被驱动。对于该系统中化学能向机械能的转换，已经提出了几种机制（界面张力梯度、气泡反冲、粘性布朗棘轮、自电泳）。通过在各种金属（金、铂、铑、镍、钌和钯）超微电极上对阳极和阴极过氧化氢反应的塔菲尔曲线，我们确定了每种金属阳极和阴极反应速率相等时的电位。这些测量使得人们能够根据双极电化学（或自电泳）机制预测所有可能的双金属组合的运动方向。在所有研究的情况下，这些预测都与观察到的运动方向一致，为该机制提供了有力支持。我们还发现，一端为金、另一端为含过氧化氢酶（一种非电化学分解过氧化氢的酶）的聚吡咯的分段纳米棒，其整体催化反应速率与含金和铂段的纳米棒相似。然而，在这种情况下未观察到轴向运动，这再次支持了双金属纳米棒的双极电化学推进机制。
