Table 3.

Basic information about the discussed methods of green synthesis and the main characteristics of the synthesized NPs.

Type of Catalyst	Applied Plant Extract in Experiments	Method of Synthesis	Size of the Newly Synthesized Particles	Structure of the Newly Synthesized Particles	Type of Pollutant in the Photocatalytic Experiments	Applied Irradiation	Efficiency of the Photocatalytic Degradation (%)	Reaction Rate Constant	Study
TiO2	Leaf extract of Azadirachta indica	Plant-mediated synthesis	Average crystal size in the range of 12.7–16.8 nm	Mesoporous structure of TiO2	Rhodamine 6 G	UV irradiation	64% after 57 min of irradiation	0.0321 min−1	[29]
TiO2	Aloe Vera gel from the plant leaf	Hydrothermal synthesis	Size of pure TiO2 57 nm, while the Ag@TiO2 38 nm	Combination of anatase and rutile phase	Picric acid	Visible irradiation	After 50 min of irradiation a decent amount of PA was removed	Not mentioned	[33]
TiO2	Leaf extract of Cinnamomum camphora	Synthesis under ambient conditions	12.6 ± 1.7 nm	Spherical shape and anatase phase of the Au-Ag/TiO2	methyl orange (MO), rhodamine B and methylene blue	UV-Vis irradiation (Xe lamp)	89.4% of MO after 60 min of irradiation; Complete degradation in the case of mixture dyes after 60 min of irradiation	0.0356 min−1 in the case of MO degradation; For the mixture the constant was not mentioned	[34]
TiO2	Leaf extract of Deinbollia pinnata	Sol–gel method	Average crystal size in the range of 19–21 nm	Aggregated, semi-spherical shape with anatase phase	Methyl orange	UV irradiation	97.53% after 150 min of irradiation	Not mentioned	[35]
TiO2	Leaf extract of Euphorbia hirta	Plant-mediated synthesis	Avarage crystal size in the range of 20–50 nm	Spherical shape and cubic phase of TiO2	Methylene blue (MB), MO, alizarin red (AR) and crystal violet (CV)	Direct sunlight	86.8% (CV); 81.3% (AR); 77.5% (MO) after 6 h of irradiation	Not mentioned	[36].
ZnO	Leaf extract of Syzygium Cumini	Not mentioned	11.35 nm	Agglomerated, well-crystallized hexagonal wurtzite structure	Methylene blue	Sunlight irradiation	91.4% after 180 min of irradiation	Not mentioned	[37]
ZnO	Pullulan, product of Aureobasidium pullulans fungus	Precipitation method	Average particle size 110.86 nm	Flower-like strucutre	Methyl orange	UV irradiation	97% after 300 min of irradiation	Not mentioned	[38,39]
ZnO	Leaf extract of Cinnamomum tamala	Plant-mediated synthesis	Average particle size 35 nm	Hexagonal wurtzite crystallite structure	Methylene blue	Direct sunlight	98.07% after 90 min of irradiation	Not mentioned	[40]
ZnO	Plant extract of Gynostemma pentaphyllum	Co-precipitation method	35.41 nm	Hexagonal structure of crystalline nanoparticles	Malachite green	UV irradiation	89% after 180 min of irradiation	Not mentioned	[41]
ZnO	Peel extract of Cavendish bananas	Plant-mediated synthesis	15.3 nm	Triangular and spherical shaped particles with hexagonal wurtzite structure	BB9 organic dye; Crystal violet (CV) and Congo red (CR)	UV-Vis irradiation (xenon lamp)	100% of BB9 after 90 min of irradiation; 97.79% of CV and 81.70% of CR after 420 min of irradiation	0.5254 h−1 for CV and 0.2837 h−1 for CR	[42]
ZnO	Leaf extract of Alchornea laxiflora	Plant-mediated synthesis	29–38 nm, depending on the volume of leaf extract	Quasi-hexagonal shape with hexagonal crystallographic phase	Congo red	Direct sunlight	87% after 60 min of irradiation	0.0401 min−1	[43]
ZnO	Peel extract of banana	Plant-mediated synthesis	18.86–20.72 depending on the type of banana	Nanocrystalline ZnO	Not mentioned	Not mentioned	Believed to be effective in the photodegradation	Not mentioned	[46]
ZnO	Jujube fruit extract	Plant-mediated synthesis	19 nm	Highly spherical shape with hexagonal wurtzite structure	Methylene blue (MB) and Eriochrome black-T (ECBT)	Direct sunlight	85% of both dyes after 300 min of irradiation	0.0087 min−1 for MB and 0.0067 min−1 for ECBT	[47]
ZnO	Leaf extract of Prunus cerasifera	Plant-mediated synthesis	Average crystal size 12 nm	Aggregated spheroidal shape with wurtzite hexagonal phase	Bromocresol green (BG), Bromophenol Blue (BB), Methyl red (MR) and Methyl blue (MB)	Direct sunlight	93.12% of BG; 90.54% of BB; 88.49% of MR and 76.76% of MB after 10 min of irradiation	Not mentioned	[48]
ZnO	Leaf extract of Becium grandiflorum	Biological approach	Average crystal size of 20 nm	Hexagonal wurtzite structure	Methylene blue	UV irradiation	69% after 200 min of irradiation	0.0019 min−1	[49]
ZnO	Root extract of Codonopsis lanceolata	Modified co-precipitation method	500 nm	Spherical, flower-like shape with hexagonal wurtzite structure of ZnO	Methylene blue	UV irradiation	90.3% after 40 min of irradiation	0.057 min−1	[50]
ZnO	Leef extract of Peltophorum pterocarpum	Plant-mediated synthesis	11.64 nm	Flowershaped particles with hexagonal wurtzite phase of ZnO	Methylene blue	Sunlight irradiation	95% after 120 min of irradiation	0.021 min−1	[51]
ZnO	Husk extract of Zea mays (Z-ZnO) and peel extract of Artocarpus heterophyllus (A-ZnO) and Punica granatum (P-ZnO)	Co-precipitation method under low temperature	28 (Z-ZnO), 55 (A-ZnO) and 25 (P-ZnO) nm	Z-ZnO flower-like; A-ZnO cauliflower-like and P-ZnO small nanoflower structure with hexagonal ZnO wurtzite phase	Antibacterial activity	Visible light irradiation	93.2% (Z-ZnO), 85.7% (A-ZnO) and 99.2% (P-ZnO) after 180 min of irradiation	0.0130 (Z-ZnO), 0.0091 (A-ZnO) and 0.0280 (p-ZnO) min−1	[52]
ZnO	Leaf extract of Sapindus mukorossi	Plant-mediated synthesis	10–1000 nm	Spherical-spiral shape	Methylene blue	Sunlight irradiation	99% (ZnO-PMMA); 98% (Ni2O3-PMMA); 93% (CuO-PMMA); 90% (Fe3O4-PMMA) after 130 min of irradiation	0.1349 (ZnO-PMMA); 0.1321 (Ni2O3-PMMA); 0.1263 (CuO-PMMA); 0.1231 (Fe3O4-PMMA) min−1	[53]
ZnO	Leaf extract of curry with coconut water	Plant-mediated synthesis	1.80, 1.62 and 1.88 nm with respect to 10-, 15- and 20-mL concentration of extract	Agglomerated, irregular spherical shape	Methylene blue	Sunlight irradiation	98.45% after 60 min of irradiation	0.0579 min−1	[54]
ZnO	Leaf extract of Stevia rebaudiana	Co-precipitation method	Average crystallite size 4.71 nm	Agglomerated flower-like shape with hexagonal wurtzite structure of the ZnO	Methylene blue	UV irradiation	76% after 30 min of irradiation	Not mentioned	[55]
ZnO	Root extract of Saponaria officinalis	Precipitation method	42–5500 nm	Sowrd-like shapes with hexagonal wurtzite phase of ZnO	Methylene blue	Visible light irradiation	15–42% depending on the applied catalyst, after 40 min of irradiation	Lower than the used reference value (i.e. lower than 0.0344 min−1)	[56]
ZnO	Leaf extract of Amaranthus dubius	Plant-mediated synthesis	82–250 nm for ZnO and 71–280 nm for 1% Fe-ZnO	Spherical cubic phase	Naphthalene	UV irradiation	63.5% (ZnO) and 71.7% (Fe-ZnO) after 240 min of irradiation	0.0045 (ZnO) and 0.0054 (Fe-ZnO) min−1	[57]
ZnO	Leaf extract of Rosemary	Plant-mediated synthesis	Average crystalline size 28.946 ± 0.002 nm	Quasi-hexagonal structure with high degree of agglomeration	Textile effluent	Visible light irradiation	63% after 100 min of irradiation	0.0111 s−1	[59]
ZnO	Leaf extract of Solanum lycopersicum	Plant-mediated synthesis	Average crystalline size 33 nm	Agglomerated spherical shape with hexagonal wurtzite structure of ZnO	Congo red	Sunlight irradiation	80% after 300 min of irradiation	Not mentioned	[60]