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arXiv 1106.5166cond-mat.mtrl-sci
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单壁碳纳米管AFM纳米探针长度和空间功能的控制

Control of Length and Spatial Functionality of Single-Wall Carbon Nanotube AFM Nanoprobes

Haoyan Wei, Sang Nyon Kim, Minhua Zhao, Sang-Yong Ju, Bryan D. Huey, Harris L. Marcus, Fotios Papadimitrakopoulos

摘要:

利用介电泳技术将单壁碳纳米管(SWNT)纳米纤维组装到导电原子力显微镜(AFM)探针上。该过程涉及在金属涂覆的AFM探针和单壁碳纳米管的稀悬浮液之间施加10 V、2 MHz的AC偏压。这对纳米管施加了正介电泳力,使它们在沉淀到探针上的同时对齐。AFM探针逐渐从单壁碳纳米管悬浮液中移除,将这些纳米管合并成具有高度对齐的纳米原纤维,如偏振拉曼实验所示。通过改变拉动速度、浸没时间和单壁碳纳米管悬浮液的浓度,可以定制这些探针的直径,从而定制这些探针的刚度。还通过将这些纳米原纤逐渐浸入并溶解到与纳米管强烈相互作用的液体中(即,十二烷基硫酸钠(SDS)溶液)。在高达450摄氏度的温度下真空退火这些纳米探针进一步增加了它们的刚度,并使它们不溶于SDS和所有其他水性介质。新的SWNT纳米原纤维从先前生长的SWNT纳米原纤维的侧面或末端的再生长也通过在期望的浸没深度处的重复介电泳组装来证明。这些配备SWNT纳米纤维的AFM探针具有导电性和机械稳定性,可用作高纵横比电化学纳米探针。

英文摘要:

Single-wall carbon nanotube (SWNT) nanofibrils were assembled onto conductive atomic force microscopy (AFM) probes with the help of dielectrophoresis (DEP). This process involved the application of a 10 V, 2 MHz, AC bias between a metal-coated AFM probe and a dilute suspension of SWNTs. This exerted a positive dielectrophoretic force onto the nanotubes that caused them to align while precipitating out onto the probe. The gradual removal of the AFM probe away from the SWNT suspension consolidated these nanotubes into nanofibrils with a high degree of alignment as demonstrated with polarization Raman experiments. By varying the pulling speed, immersion time, and concentration of the SWNT suspension, one can tailor the diameter and thus the stiffness of these probes. Precise length trimming of these nanofibrils was also performed by their gradual immersion and dissolution into a liquid that strongly interacted with nanotubes, (i.e., sodium dodecyl sulfate (SDS) solution). Vacuum annealing these nanoprobes at temperature up to 450 degree C further increased their stiffness and rendered them insoluble to SDS and all other aqueous media. Regrowth of a new SWNT nanofibril from the side or at the end of a previously grown SWNT nanofibril was also demonstrated by a repeated dielectrophoretic assembly at the desired immersion depth. These SWNT nanofibril-equipped AFM probes are electrically conductive and mechanically robust for use as high-aspect-ratio electrochemical nanoprobes.

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