Catalytic nanomotors: Autonomous movement of striped nanorods
Catalytic nanomotors: Autonomous movement of striped nanorods
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DOI：
10.1021/ja047697z
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发表时间：
2004-10-20
影响因子：
15
通讯作者：
Crespi, VH
中科院分区：
文献类型：
--
作者：
Paxton, WF;Kistler, KC;Crespi, VH
棒状颗粒，直径为370 nm，由1 μ m长的Pt和Au段组成，在过氧化氢水溶液中通过催化在Pt端形成氧而自主移动。在2-3%的过氧化氢溶液中，这些棒主要沿着它们的轴在Pt端的方向上以高达每秒10个体长的速度移动。杆的尺寸和它们的速度与多鞭毛细菌相似。沿棒轴的力沿着，其为10（-14）N的量级，由氧浓度梯度产生，其又产生平衡稳态下的拖曳力的界面张力。通过在移动棒的框架中求解对流扩散方程，发现界面张力力的尺度近似为SR（2）γ/μ DL，其中S是面积归一化的氧气析出速率，γ是液体-蒸气界面张力，R是棒半径，μ是粘度，D是氧气的扩散系数，并且L是棒的长度。在乙醇-水溶液中的实验证实了速度与积S γ的线性关系，并且缩放实验表明速度对R和L的强烈依赖性。运动的方向意味着在实验条件下金表面是疏水的。轻敲模式的AFM图像棒在空气饱和的水显示软功能，在空气中获得的图像不明显。假设这些特征是纳米气泡，如果存在于过氧化氢溶液中，将解释观察到的运动方向。
Rod-shaped particles, 370 nm in diameter and consisting of 1 mum long Pt and Au segments, move autonomously in aqueous hydrogen peroxide solutions by catalyzing the formation of oxygen at the Pt end. In 2-3% hydrogen peroxide solution, these rods move predominantly along their axis in the direction of the Pt end at speeds of up to 10 body lengths per second. The dimensions of the rods and their speeds are similar to those of multiflagellar bacteria. The force along the rod axis, which is on the order of 10(-14) N, is generated by the oxygen concentration gradient, which in turn produces an interfacial tension force that balances the drag force at steady state. By solving the convection-diffusion equation in the frame of the moving rod, it was found that the interfacial tension force scales approximately as SR(2)gamma/muDL, where S is the area-normalized oxygen evolution rate, gamma is the liquid-vapor interfacial tension, R is the rod radius, mu is the viscosity, D is the diffusion coefficient of oxygen, and L is the length of the rod. Experiments in ethanol-water solutions confirmed that the velocity depends linearly with the product Sgamma, and scaling experiments showed a strong dependence of the velocity on R and L. The direction of motion implies that the gold surface is hydrophobic under the conditions of the experiment. Tapping-mode AFM images of rods in air-saturated water show soft features that are not apparent in images acquired in air. These features are postulated to be nanobubbles, which if present in hydrogen peroxide solutions, would account for the observed direction of motion.