Table 1.

Physicochemical characteristics of zinc oxide (ZnO) materials.

Morphology	Particle Size	Porosity	Surface Area (m2/g)	Synthesis Method (Precursor)	Refs.
Spheres	12 nm, 25 nm	Slit-like pores	90.4, 42.8	▪Solvothermal synthesis using tetramethyl ammonium hydroxide (TMAOH) (zinc nitrate hexahydrate)	[16]
	62–94 nm	Not available	Not available	▪Green synthesis using Catharanthus roseus leaf extract (0.01 M zinc acetate dehydrate)	[47]
	15–20 nm	Not available	Not available	▪Green synthesis & co-precipitation using Bambusa Vulgaris leaf extract (0.5 mol/50 mL zinc nitrate in water)	[48]
	25–30 nm (TEM); 65 ± 4 nm (dynamic light scattering)	Not available	Not available	▪Green synthesis using Sambucus ebulus leaf extract (1 M zinc acetate dihydrate)	[49]
	12–46 nm	Not available	Not available	▪Green synthesis using Hibiscus subdariffa leaf extract with further heating at 60 °C for 4 h (91 mM zinc acetate in water)	[50]
Spheres in self-assembled network	48.3 nm	Mesopores, 5–6.25 nm; macropores, 2–6 μm	Not available	▪Sol–gel synthesis using oleylamine with annealing process at 150 °C (zinc acetylacetonate dihydrate)	[18]
Spheres in NP cluster	NPs-63 nm; cluster-590 nm	34 nm	20.72	▪ Soft chemical synthesis using urea (3.6 mol) and glycerol (3.6 mol) (micrometric ZnO, 6 wt.%)	[19]
Dumbbells	Length 190–250 nm; breadth 50–60 nm	Not available	Not available	▪Green synthesis using Hibiscus subdariffa leaf extract, dried at 100 °C for 4 h (91 mM zinc acetate in water)	[50]
Nanorods	Length 523 nm; diameter 47 nm	Not available	2.3	▪Sol–gel synthesis using 1 M hexamethyl tetraamine (HMTA) at pH 6.5 (1 M zinc nitrate in water)	[52]
	Length ~2 μm; diameter ~50 nm	Not available	Not available	▪Green synthesis using Egg white albumen calcined at 650 °C (1 mmol/mL zinc acetate dihydrate)	[53]
Hollow nanotubes	Length ~500 nm	53 nm (900 °C annealing), 114.6 nm (700 °C annealing), 255.4 nm (500 °C annealing), 278.6 nm (as-synthesized)	2.4 (900 °C annealing), 7.2 (700 °C annealing), 16.7 (500 °C annealing), 17.8 (as-synthesized)	▪Hydrothermal synthesis using 0.25 mM polyvinyl alcohol (PVA) at pH 9 with annealing process at 500–900 °C (14 mM zinc acetate dihydrate)	[54]
	Length ~5 μm; thickness 59.5 nm	Internal diameter 178.2 nm	Not available	▪Atomic layer deposition (ALD) over electrospun polyvinyl alcohol (PVA) nanofibers (template) after polymer removal through calcination or hydrolysis (diethyl zinc (Zn(C2H5)2)	[55]
Needles	Length ~2 μm; diameter 20–40 nm	Not available	Not available	▪Green synthesis using Berberis aristata leaf extract, adjusting pH with 1 M sodium hydroxide (NaOH) (0.1 M zinc acetate dihydrate)	[56]
Disks	41 nm	Not available	Not available	▪Co-precipitation using 2 M sodium hydroxide in water at room temperature (1 mM zinc acetate dihydrate)	[57]
Platelets	14.7 nm, 17.5 nm; hydrodynamic environment- 6.4 μm, 5.0 μm	17.3 nm, 11.6 nm	39.0, 46.9	▪Not available (conventional products)	[58]
Flowers	Length 200–500 nm; length 1–2 μm	Not available	Not available	▪Electrochemical-thermal technique using poly-diallyl-(dimethylammonium) chloride (PDDA) and benzyl-dimethylammonium chloride (BAC) as a stabilizer (Two Zn electrodes)	[45]
	23.7–88.8 nm	Not available	Not available	▪Sol–gel synthesis using 0.2 w/v% cetyltrimethyl ammonium bromide (CTAB) at pH 11.7–11.9, and near-room temperatures (25–75 °C) (5% zinc acetate dihydrate)	[59]
	700 nm–2.2 μm	Not available	Not available	▪Co-precipitation using 0.1 M NaOH calcined at 550 °C (0.1 M zinc nitrate hexahydrate)	[60]
	45 nm	Not available	28.8	▪Solvothermal synthesis using 0.5 M NaOH at pH 9 (5.60 g/50 mL zinc acetate dihydrate in water)	[61]
Stars	31 nm	Not available	Not available	▪Liquid precipitation using 1 M NaOH (0.01 mol/50 mL zinc acetate dihydrate in water)	[62]
Flakes	32 nm	Not available	Not available	▪Co-precipitation using 0.02 M sodium carbonate (0.01 M zinc acetate)	[63]