Electrochemical synthesis of morphology-controlled segmented CdSe nanowires

Morphology, that is, the study of form comprising shape, size, and structure, is important for materials research in general. For nanostructured materials, popularly known as nanomaterials, morphology has a special significance since form, in this case, dictates physical and chemical properties. Unlike bulk materials, properties of nanomaterials are strongly correlated to form. Here, we present a novel strategy for the synthesis of morphology-controlled segmented CdSe semiconductor nanowires based on a straightforward sweep voltammetry approach of preprogrammed characteristics. It was found here that, by simply and simultaneously modulating the basic parameters of each cyclic voltammetry cycle during the nanowire growth process, scan rate, and cycle potential range, we can achieve a precise control over the morphology of the semiconductor material segment, density, and dimensions, obtained after each voltammetric cycle. The morphology of CdSe segments was found to be controlled by the extent of co-deposition of metal cadmium together with the deposition of CdSe. Thus "dense" CdSe segments and "nondense" segments can be achieved in the absence and presence of cadmium metal co-deposition, respectively. Accompanied by the density modulation achieved by the potential range applied, it was also observed that a fine control over each segment's length, varying between few tenths to few hundred nanometers, can be achieved by simple altering the scan rate of each cycle along the wire. Also, we propose a simple mechanism that accounts for the formation of segments of controlled morphology. This is the first report on the synthesis of "segmented" CdSe nanowires of controlled morphology, density, and length of each segment, by simple single-step cycle voltammetry preprogrammed sequences from a single electrodeposition solution. In addition, this novel strategy may be applied for the synthesis of additional analogue semiconductor materials of importance (e.g., CdS, CdTe, etc.). This segmented nanowire's synthetic route is remarkably fast and simple, leading to a high encoding capacity with a large number of distinguishable signatures.