Photoconductive cadmium sulfide hemicylindrical shell nanowire ensembles.

We report the synthesis and characterization of hemicylindrical shell nanowires (HSNWs) composed of nanocrystalline cadmium sulfide (CdS). CdS HSNWs were synthesized by first electrodepositing microcrystalline cadmium (Cd) nanowires by electrochemical step-edge decoration on graphite electrode surfaces and then converting these Cd nanowires into CdS by exposure to H2S at elevated temperature. These nanowires had a hemicylindrical shell morphology that was produced by the Kirkendall effect, involving disparate rates for diffusion of Cd and S atoms within the nascent CdS layer during the conversion from Cd to CdS. The outer diameter of the CdS HSNWs was 1.6-2.4 times that of Cd precursor nanowires and was adjustable over the range from 116 to 550 nm. CdS HSNWs showed strong, band-edge photoluminescence at 2.45 eV and a fast, reversible, and stable photoconductivity response in air characterized by "on" and "off" times of less than 15 ms.