Table 5.

Typical researches about biological imaging of ZnO NPs.

Materials	Size and models	Biological imaging
ZnO@MAA-co-PEGMEMA	Human hepatoma cells	With tunable photoluminescence emission and high quantum yield, under UV light, ZnO-1 showed green fluorescence, while ZnO-2 appeared yellow [121]
ZnO@PMAA-co-PDMAEMA	Spherical: 4 nm/COS-7 cells	The PDMAEMA-modified ZnO QDs emitted strong yellow luminescence under UV light [124]
ZnO-Au@PEG NPs	<100 nm/B16F10 cells	ZnO-Au@PEG NPs can penetrate into the living cells and exhibit bright yellow fluorescence [125]
ZnO nanosheets	46.6 ± 8.5 nm/K562 cells	Yellow-orange light emission was observed around or inside the cells under UV light [122]
ZnO@silica NPs	2.7–4.4 nm/HeLa cells	Monodispersed ZnO@silica NPs with blue, green, and yellow emission through using VTES, TEOS, and APS as modification materials [126]
Fe3O4-ZnO NPs	15.7 nm/dendritic cells	Fe3O4-ZnO NPs emit green fluorescence under UV light irradiation [127].
ZnO@silica NPs	NIH/3T3 cells	ZnO@silica NPs exhibited emission colors of blue, green, yellow, and orange under 365 nm excitation via the adjustment of the pH of the precipitation solutions [123]
ZnO@silica NPs	55 nm/nerve cells, Caco-2 cells	ZnO@silica QD colloidal solution exhibited a significant blue emission [128]
ZnO nanowires	20–50 nm/U87MG cells, MCF-7 cells	ZnO nanowires exhibited green fluorescent. RGD peptide-conjugated green fluorescent ZnO NWs can be specifically targeted to cell surface receptors in vitro [129]