Thick-And-Thin Nanowire Segments

A simple electrochemical method can be used to prepare semiconductor nanowires that feature segments of alternating density and size along the wire’s length, according to a paper published in ACS Nano (DOI: 10.1021/nn901661z). Multisegmented nanowires could be used as nanometer-scale bar codes in biodetection applications or as basic components of optoelectronic devices that exploit the wires’ periodic properties. Prior studies have led to multistep procedures for preparing nanowires with alternating segments of dissimilar materials—for example, two different metals, a metal and a semiconductor, or alloys of various compositions. Nava Shpaisman, Uri Givan, and Fernando Patolsky of Israel’s Tel Aviv University have now devised a cyclic voltammetry method for growing CdSe nanowires in which uniformly sized dense segments of the material are separated by shorter uniformly sized porous segments that are less dense. The technique, which is based on delivering a single electrodeposition solution to a porous membrane, relies on computer control of the voltammetry parameters to tune the segment lengths. Cadmium metal, which codeposits with CdSe, is removed during voltage cycling, thereby forming the porous segments.