A nanowire is a nanomaterial having a structure resembling a wire with a diameter of the order of 1 nanometer (10−9 meters). In a nanowire the ratio of the length to width is greater than 20; this means the length of the wire should be more than 20 times its diameter.
Nanowires (NW) can be categorised according to their chemical nature (e.g. molecular NW like DNA) or by their electrical properties, such as metallic (e.g. Ni, Pt, Au), semiconducting (e.g. Si, InP, GaN, etc.), and insulating (e.g. SiO2) nanowires.