Ultrafast Catalytic Alloy Nanomotors
Ultrafast Catalytic Alloy Nanomotors
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DOI：
10.1002/anie.200803841
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Wang, Joseph
中科院分区：
文献类型：
--
作者：
Demirok, U. Korcan;Laocharoensuk, Rawiwan;Wang, Joseph
利用纳米电机驱动纳米机器和纳米工厂是纳米技术面临的最令人兴奋的挑战之一。[1，2]最近的研究表明，由过氧化氢燃料的电催化分解推动的双金属纳米线(Au-Pt，Au-Ni)连续自主的非布朗运动。[3，4]有效的能量传递是成功使用这种催化纳米电机作为纳米设备发电引擎的关键。目前已知的大多数双金属纳米线的移动速度最高可达10-20μms±1。[5]我们最近报道，通过将碳纳米管(CNT)引入铂段，纳米电机的速度可加速到51μms？1。[6]生物电化学推进也已有报道，但与更大(mm长)的酶功能化碳纤维有关。[7]在这里，我们展示了使用阴极Ag/Au合金而不是黄金段，将双段纳米线电机显著加速到150μms？1以上。几十年来，合金一直被用来提高电极的催化活性。[8]与单独使用银或金相比，银/金合金更早地被证明可以增强过氧化氢的电子转移反应。[9，10]然而，据我们所知，还没有关于使用合金段来显著提高燃料驱动纳米电机的速度和功率的报道。由于合金段是通过同时电沉积其金属组分来制备的，因此在不影响模板引导纳米线制备路线的简单性的情况下，实现了新型Ag/Au-Pt纳米电机的超快速度和高效率。图1显示了在15wt%过氧化氢存在下，Au-PT(A)和Ag/Au-PT(B)纳米线电机在1秒内的典型跟踪线和移动距离。在此期间，Au-Pt马达的移动距离约为10μm，而Ag/Au-Pt纳米线的移动距离超过110μm。相应的视频(参见支持信息)清楚地说明了含合金纳米线的运动速度显著加快。这些纳米电机在整个15分钟的跟踪实验中表现出明确的定向运动，其白金端向前移动，并保持其速度。速度分布曲线(在10秒期间超过50个纳米电机；图1C)显示，Au-PT和Ag/Au-PT纳米线的平均速度分别为10.2ms±1和113.6μms±1。其中约5%的合金丝显示的速度高于150μms？1，相当于超过75个体长/S，接近最有效的生物摩托(如鞭毛细菌)的速度。[11]含碳纳米管的纳米线在相同燃料成分下的平均速度为51μms？1。[6]图1的数据表明，合金纳米摩托的能量转换和输出功率显著高于Au-铂纳米摩托，反映出显著更高的燃料分解率。考虑到输出功率按速度的平方变化[6]，并且速度提高了11倍，新的合金线提供了大约121倍于传统纳米线马达的输出功率。新型合金纳米线电机的速度受Ag/Au段组成的影响很大。直方图和图形条(图2)表明，当生长溶液中的银含量从0增加到75%(v/v)(a-d)时，速度以近乎线性的方式增加。而基于纯金段的电机显示的平均速度为9.9μms？1(A)，而在5wt%H_2O_2溶液中观察到在镀液中制备的合金段的平均速度为35.9、63.6和87.2μms？1。…
The use of nanomotors to power nanomachines and nanofactories is one of the most exciting challenges facing nanotechnology.[1, 2] Recent efforts have demonstrated the continuous autonomous non-Brownian movement of bimetal nanowires (Au-Pt, Au-Ni) propelled by electrocatalytic decomposition of hydrogen peroxide fuel.[3, 4] Efficient energy transduction is crucial for the successful use of such catalytic nanomotors as power-generating engines for nanoscale devices. Most bimetal nanowires known to date can move at speeds of up to 10–20 μmsÀ1.[5] We reported recently that the speed of nanomotors can be accelerated up to 51 μmsÀ1 by incorporating carbon nanotubes (CNTs) into the platinum segment.[6] Bioelectrochemical propulsion has also been reported but in connection with larger (mm-long) enzyme-functionalized carbon fibers.[7] Herein, we demonstrate a dramatic acceleration of bisegment nanowire motors to over 150 μmsÀ1 by using a cathodic Ag/Au alloy instead of a gold segment. Alloys have been used for several decades for improving the catalytic activity of electrodes.[8] Ag/Au alloys were shown earlier to enhance the electron transfer reactions of hydrogen peroxide compared to silver or gold alone.[9, 10] However, to the best of our knowledge there are no reports on using alloy segments to dramatically enhance the speed and power of fuel-driven nanomotors. As the alloy segment is prepared by simultaneous electrodeposition of its metal constituents, the ultrafast speed and high efficiency of the new Ag/Au-Pt nanomotors are achieved without compromising the simplicity of the template-guided nanowire preparation route. Figure 1 shows typical tracking lines and moving distances of Au-Pt (A) and Ag/Au-Pt (B) nanowire motors for 1 sec in the presence of 15 wt% hydrogen peroxide. The Au-Pt motors travel over a distance of circa 10 μm, whereas the Ag/Au-Pt nanowires moved over 110 μm during this period. The corresponding videos (see the Supporting Information) clearly illustrate the dramatically faster motion of the alloycontaining nanowires. These nanomotors display a welldefined directional motion with their platinum end forward and maintained their speed during the entire 15 min tracking experiment. Speed distribution profiles (for over 50 nanomotors during a 10 sec period; Figure 1C), indicate average speeds of 10.2 and 113.6 μmsÀ1 for the Au-Pt and Ag/Au-Pt nanowires, respectively. About 5% of these alloy wires display speeds higher than 150 μmsÀ1, corresponding to over 75 body-lengths/s and approaching the speed of the most efficient biomotors (eg, flagellated bacteria).[11] CNT-containing nanowires have an average speed of 51 μmsÀ1 using the same fuel composition.[6] The data of Figure 1 indicate that the energy conversion and output power of the alloy nanomotors are significantly higher than that of Au-Pt nanomotors, reflecting the substantially higher fuel decomposition rate. Considering that the output power varies as the square of velocity [6] and the 11-fold speed enhancement, the new alloy wires offer approximately 121 times higher output power compared to conventional nanowire motors. The speed of the new alloy nanowire motors is strongly affected by the composition of the Ag/Au segment. Histograms and graph bars (Figure2) illustrate that the speed increases in a nearly linear fashion upon increasing the silver level in the growth solution from 0 to 75%(v/v)(a–d). Whereas motors based on the pure gold segment display an average speed of 9.9 μmsÀ1 (A), average speeds of 35.9, 63.6, and 87.2 μmsÀ1 are observed in 5 wt% H2O2 solution for alloy segments prepared in plating solutions …