Table 2.

Summary of various processing routes for the production of 1-D ZnO nanostructures.

Processing Route	Synthesis Method	Starting Materials	Synthesis Temperature (°C)	Morphology	Diameter of ZnO nanostructure	Length of ZnO nanostructure	Reference
Wet Processing route	Hydrothermal	ZnAc2, NaOH, absolute ethanol, distilled water	180	Nanorod	–	–	[5]
		Zn(CH3COO)2·2H2O, C6H8O7·H2O, absolute ethanol, distilled water	400	Nanorod (vertically aligned)	50 nm	500 nm	[7]
		Zn(NO3)2·6H2O, NaOH, cetyltrimethyl ammonium bromide, ethanol	120	Nanorod	–	–	[48]
		Zn(NO3)2·6H2O, NaOH, cyclohexylamine, ethanol, water	200	Nanorod	150–200 nm	2 μm	[52]
		Zn(SO4)·7H2O, NH4OH, deionized water	75–95	Nanorod	–	–	[11]
		NaOH, Zn(NO3)2, absolute ethanol, deionized water, hydroethylenediamine	180	Flowerlike	150 nm	Few micrometer	[53]
	Ultrasonic irradation in aqueous solution	Deposited Zn layer on interdigitated alumina substrate, Zn(NO3)2·6H2O, (CH2)6N4	–	Nanorod (vertically aligned)	50 nm	500 nm	[12]
Solid-state processing route	Carbothermal Reduction	ZnO powder, graphite powder, Ar gas flow, Au coated silicon substrate	900–925	Nanowire	80–120 nm	10–20 μm	[17,54]
	Solid-state chemical reaction	ZnCl2, NaOH, polyethylene glycol, Na2WO4·2H2O	RT	Nanorod	40–60 nm	200 nm	[18]
					20–40 nm	100 nm
Vapor-7phase processing route	Thermal evaporation	Zn metal, O2, Ar	650–670	Nanowire	100 nm	Several microns	[55]
		Zn metal pellets, O2, Ar	900	Nanowire	20 nm	–	[19]
		Zn powder, O2, Ar	600	Nanowire	80 nm	1 μm	[56]
	Vapor-phase transport	ZnO powder, graphite, Cu catalist	930	Hierarchical dendrite	60–800 nm	–	[20]
	Aerosol	Zn powder, N2 gas	500–750	Fiber-mat	100–300 nm	–	[21]
				Cauliflower	20–30 nm	–
	RF sputtering	ZnO deposited over Pt sputtered interdigitated alumina substrate	−	Nanobelt	–	Few micrometer	[22]
	Molecular beam epitaxy	Zn metal, O3/O2 plasma discharge, Au coated substrate	600	Nanorod	50–150 nm	2–10 μm	[23]