Road Map for the Controlled Synthesis of CdSe Nanowires,Nanobelts, and Nanosaws—A Step Towards Nanomanufacturing

One‐dimensional (1D) nanostructures of CdSe have been found to exhibit morphologies of nanowires, nanobelts, and nanosaws, but their synthesis is by trial and error. To meet the needs of large‐scale, controlled, and designed synthesis of nanostructures, it is imperative to systematically find experimental conditions under which the desired nanostructures are synthesized reproducibly, in large quantity, and with controlled morphology. This article reports the first systematic study on the growth of 1D CdSe nanostructures by a vapor–liquid–solid (VLS) process by varying a wide range of experimental conditions. Over 150 experiments have been conducted to investigate the morphology dependence of three different types of nanostructures: nanowires, nanobelts, and nanosaws, over various substrate temperatures and pressures. The results of this work yield a road map for the controlled growth of 1D CdSe nanostructures. This research serves as a guidance and “menu” for scaling up of the synthesis of CdSe nanostructures. This is a key step towards the controlled synthesis of nanostructures to meet the needs of many industrial applications of nanomanufacturing.     

Supercritical Fluid–Liquid–Solid (SFLS) Synthesis of Si and Ge Nanowires Seeded by Colloidal Metal Nanocrystals

Semiconductor nanowires, 5 to 20 nm in diameter and micrometers in length, appear to be promising candidates for a variety of new technologies, including computing, memory, and sensor applications. Suitable for these applications, silicon (Si) and germanium (Ge) nanowires ranging from 4 to 30 nm in diameter and micrometers in length can be produced in high temperature supercritical fluids by thermally degrading organosilane or organogermane precursors in the presence of organic‐monolayer‐protected gold nanocrystals. Although gas phase vapor–liquid–solid (VLS) methods can be used to produce a variety of different nanowire materials, high temperature supercritical fluids provide wire size control through nanocrystal size selection prior to synthesis, and high product yields due to the high precursor solubility.