Cellular response of one-dimensional silicon nanowires and the effect of etching silicon (111) substrates with hydrofluoric acid prior to nanowire growth

Silicon nanowires (SiNWs) have been extensively explored in the past decades not only for their electronic properties but also for their chemical/physical properties. A variety of discoveries in SiNWs have made it possible for potential device applications such as chemical sensors, biosensors, transistors, etc. In this research, two aspects of SiNWs were studied: cellular uptake of 1D silicon nanowires, and HF pretreatment for vertical SiNW growth.;Due to SiNWs showing strong emission from four-wave mixing signals, three aspect ratios of positively charged SiNWs (2-3 μm, 5-6 μm, and 8-9 μm length and 40 nm in diameter) were used to study the cellular uptake of NWs. Silicon nanowires were modified with an amine-terminated layer to introduce positive charges on their surface. Chinese hamster ovary-β cells (CHO-β) showed size-dependent uptake of NWs in which 2-3 μm wires were more efficiently internalized into cells than 5-6 μm long nanowires, and 8-9 μm long nanowires bound to cell surfaces. The longer SiNWs underwent toxicity faster than shorter SiNWs using equivalent concentrations.;Development of a quick method for growing vertical SiNWs was investigated. In this study, silicon nanowires were grown on Si (111) substrates using silane gas as the precursor and Au colloids as the catalyst. Si (111) substrates were pretreated with HF solution prior to transferring to a quartz tube. For growth, the results demonstrated a linear relationship between etch time and growth rate of SiNWs. Vertical SiNWs were obtained using an 8 second etch time and had a growth rate of 3 nm sec-1 at 460°C growth temperature.