During the literature survey, it was observed that members of the Fabaceae, Rutaceae, Apocynaceae, Solanaceae and Lamiaceae families are most commonly employed for the production of ZnNPs (
Table 3). Plants from the family Lamiaceae, such as
Anisochilus carnosus,
Plectranthus amboinicus and
Vitex negundo were used to produce ZnO nanoparticles of different sizes and shapes, including hexagonal, spherical, quasi-spherical and rod-shaped particles. The findings indicated that the particle sizes decrease when plant extract concentration increases
[107][108]. All experiments displayed nanoparticles in the same size range with spherical and hexagonal disc shapes, which XRD and TEM analysis characterized. Singh et al.
[109] synthesized ZnO NPs using
Calotropis procera latex that were spherical and 5 nm to 40 nm in size. Ramesh et al.
[110] used the floral extract of
Cassia auriculata to react with Zn(NO
3)
2 solution resulting in the development of ZnNPs with a particle size ranging from 110 nm to 280 nm. Some reports on the plant-assisted synthesis of zinc nanoparticles are listed below in
Table 3.
Table 3. Plant-assisted synthesis of zinc nanoparticles.
Plant Name |
Parts Used |
Size (nm) |
Shapes |
Reference |
Artemisia pallens |
Leaves along with stem |
50–100 |
Hexagonal |
[105] |
Cayratia pedata |
Leaves |
52.24 |
Spherical |
[111] |
Euphorbia hirta |
Leaves |
20–50 |
Spherical |
Momordica charantia |
Fruit |
30–40 |
Cubical |
[ | 94 | ] |
[ | 112 | ] |
Eucalyptus globules |
Leaves |
52–70 |
Spherical, elongated |
[104] |
Tamarind |
Leaves |
20–40 |
Triangle |
[32] |
Aloe vera |
Plant extract |
50/350 |
Crystalline |
[88] |
Mentha, Ocimum, Eucalyptus |
Leaves |
3–16 |
Spherical |
[89] |
Canna indica, Quisqualis indica |
Leaves and flower |
30–130 |
Polymorphic/stable |
[ |
Phyllanthus amarus |
Leaves |
65–99 |
Cubic |
[95] |
Mangifera indica |
Leaves |
17–20 |
Tecoma castanifolia |
Leaves |
70–75 |
Spherical |
[113] |
Zingiber officinale |
Root |
90 | ] |
30–50 |
Spherical |
[ | 114 | ] |
Catharanthus roseus |
Leaves |
23–572–6 |
Murraya koenigii |
Azadirachta indica |
Leaves |
50 |
Spindle shaped |
Spherical |
[116] |
Spherical |
[42] |
[ | 115 | ] |
Leaves |
Solanum nigrum |
Leaves |
20–30 |
Hexagonal |
[117] |
20 |
Spherical |
[91] |
Olea europea |
Leaves |
18–30 |
Crystalline |
[118] |
Ceratonia siliqua |
Aegle marmelos | Leaves extract |
5–40 |
Spherical |
[ |
Leaves | 61] |
4–10 |
Spherical |
Azadirachta indica |
Leaves |
25 |
Crystalline | [80] |
[119] |
Suaeda monoica |
Leaves |
31 |
Spherical |
[62] |
Rosa hybrid |
Rose petals |
10 |
Cubic |
[92] |
Nyctanthes arbor-tristis |
Flowers |
12–32 |
Crystalline |
[120] |
Catharanthtus roseus |
Leaves |
35–55 |
Cubical |
[47] |
Terminalia chebula |
Plant extract |
6–60 |
Ocimum sanctum |
Leaves extract |
10–20 |
Spherical |
[63] |
, etc. The synthesis of TiO
2 nanoparticles on a wide scale using biological methods has stimulated the interest of researchers due to its low cost, environmental friendliness and reproducibility. Nowadays, there are many reports on the biosynthesis of TiO
2 nanoparticles by using microbes (such as bacteria and fungi), algae, plant parts and enzymes. The aqueous extract of
Eclipta prostrata produce nanoparticles with a spherical shape and sizes ranging from 36 nm to 68 nm, confirmed by XRD and TEM analysis
[139]. Subhashini and Nachiyar
[140] used the leaf extract of
Albizia saman for the production of titanium NPs via a green route. The aqueous TiO
2 solution was added dropwise into the leaf extract with stirring at 50 °C resulting in the formation of anatase crystals of TiO
2 nanoparticles. The synthesized TiO
2 nanoparticles were found to be 41 nm in size and confirmed by XRD analysis. Jalill et al.
[141] synthesized the anatase form of TiO
2 nanoparticles by using the plant extract of
Curcuma longa (because of its terpenoid and flavonoid contents). The nanoparticles that were developed were identified by the techniques of XRD, FTIR, SEM and EDX that revealed the aggregated, circular structure and a particle size of 160–220 nm. TiNPs were synthesized by the utilization of herbal extract (as a bio-reductant) of
Echinacea purpurea [142]. The particle size of the synthesized TiO
2 nanoparticles was found to be in the 120 nm range. The leaf extract of
Psidium guajava includes alcohol and primary and aromatic amines, which aid in producing TiO
2 nanoparticles. Some reports on the plant-assisted synthesis of titanium nanoparticles are listed below in
Table 4.
Table 4. Plant-assisted synthesis of titanium nanoparticles.
Plant Name |
Parts Used |
Size (nm) |
Shapes |
Reference |
Ledebouria revoluta |
Bulb |
47 |
Tetragonal |
[143] |
Pouteria campechiana |
Leaves |
73–140 |
Spherical |
[144] |
Syzygium cumini |
Leaves |
22 |
Spherical round |
[145] |
Mentha arvensis |
Leaves |
20–70 |
Spherical |
[146] |
Azadirachta indica |
Leaves |
15–50 |
Spherical |
[147] |
Psidium guajava |
Leaves |
32.58 |
Spherical |
[148] |
Nyctanthes arbor-tristis |
Leaves |
100–150, 100–200 |
Cubic, crystalline, Spherical |
[149] |
Hibiscus rosa-sinensis |
Leaves |
Calotropis gigantea |
Flower |
10–52 |
Crystalline, Spherical oval |
[150] |
Salvia officinalis |
Leaves |
15–20 |
Spherical |
[136] |
Solanum trilobatum |
Leaves |
70 |
Spherical, oval |
[151] |
Azadirachta indica |
Leaves |
124 |
Spherical |
[152] |
Annona squamosal |
Leaves |
40–60 |
Spherical |
[153] |
30–35 |
Crystal, spongy |
[121] |
Jatropha curcas, citrus aurantium |
Leaves |
25–50 |
Spherical |
Ruta graveolens |
Stem |
28 |
Spherical |
[102] |
Ocimum tenuiflorum |
Leaves |
25–40 |
Spherical |
[64] |
Anisotropic |
Aloe vera |
Leaves |
22.18 |
Hexagonal |
[122] |
Ginkgo biloba |
Leaves |
15–500 |
Cubic |
[65] |
Spherical |
[ | 96 | ] |
Ocimum tenuiflorum |
Leaves |
11–25 |
Hexagonal |
Tanacetum vulgare |
Fruit |
16 |
Spherical |
[66 |
[ | 123 |
Stevia rebaudiana | ] |
] |
Leaves |
8–20 |
Octahedral |
[ |
Sargassum muticum |
Leaves |
30–57 |
Hexagonal |
[124] |
Argemone mexicana |
Leaves extract |
30 |
Spherical, hexagonal |
[67] |
97 | ] |
Nyctanthes arbortristis |
Flower extract |
Calotropis gigantea |
Leaves | 19.8 |
Spherical, hexagonal |
[79] |
1.5–8.5 |
Spherical |
[103] |
[ | 154 | ] |
Sesuvium portulacastrum |
Callus extract |
5–20 |
Spherical |
[68] |
Trigonella foneum-graecum |
Leaves |
15–25 |
Spherical |
[75] |
Beta vulgaris |
Root |
52–76 |
Hexagonal |
Hibiscus-rosa-sinensis[125 |
Petals |
7–24 | ] |
Syzygium cumini |
Leaves and seed |
29–92 |
Spherical |
[ | 12 | ] |
Tanacetum vulgare | Spherical |
Fruit | [45] |
11 | [69] |
Triangular |
[ |
Curcuma longa |
Root | 66 |
20–80 | ] |
Erythrina variegates |
Leaves | Hexagonal |
[ |
39 |
Crystalline, spherical | 126] |
[ | 160 | ] |
Cinnamomum camphora |
Sun dried leaves |
3.2–20 |
Cubic hexagonal crystalline |
Cuminum cyminum |
Seeds | [ | 70 | ] |
1–10 |
Spherical |
[ | 98 | ] |
Nephelium lappaceum |
Peel |
20 |
Spherical |
[127] |
Melia azedarach |
Leaves |
78 |
Spherical |
Sorbus aucuparia |
Leaf extract |
16–18 | [ | 71] |
Spherical, triangular, hexagonal |
[ |
Artocarpus gomezianus |
Fruit | 99 | ] |
50 |
Spherical |
[ |
Rhododedendron dauricam |
Flower extract |
25–40 |
Spherical |
[72] |
Lippia citriodora |
Leaves extract |
2.4. Zinc Nanoparticles
Zinc oxide (ZnO) is an inorganic metal oxide with a vast range of nanostructures. Zinc nanoparticles (ZnNPs) have gained considerable attention due to their low cost, large surface area, white appearance, UV-filtering, antifungal, antibacterial and photochemical properties, and high catalytic activity
[100][101]. There are several reports of ZnO nanoparticle synthesis using various plant extracts
[102][103][104][105]] |
Senna auriculata |
Leaves |
2 |
Spherical |
[ |
129 |
] |
Brassica oleraceae |
Leaves |
1–100 |
Jatropha curcas |
Latex |
25–50 |
Spherical, uneven |
[155] |
Euphorbia prostrata |
Leaves |
81–84 |
Spherical |
[156] |
Citrus sinensis |
Fruit peel |
19 |
Tetragonal |
[157] |
Cassia auriculata |
Leaves |
38 |
Spherical |
[158] |
Ocimum basilicum |
Leaves |
50 |
Hexagonal |
[159] |
Spherical and sheet shaped |
[130] |
Acalypha Indica |
Leaves |
100–200 |
Cube |
[131] |
Plectranthus amboinicus |
Leaves |
20–50 |
Crystalline |
[132] |
Coptidis rhizome |
Rhizome |
2.9–25.2 |
Spherical and rod shaped |
[133] |
Ginger |
Rhizome |
23–26 |
Crystalline |
[134] |
2.5. Titanium Nanoparticles
Titanium dioxide nanoparticles (TiNPs) have drawn great attention because of their appropriate electrical band structure, high specific surface area and quantum efficacy, stability, and chemical innerness
[135]. TiNPs have a wide applicability in lowering the toxicity of synthetic dyes
[136] and pharmaceutical medicines
[137], wastewater treatment
[138]
2.6. Palladium Nanoparticles
The major studies of most researchers were focused on the biological synthesis of palladium nanoparticles (PdNPs) via plant materials because it is cost-effective, sustainable, and human- and eco-friendly. Plant extracts contain a number of primary and secondary metabolites that transform metal (Pd) salts to PdNPs. Siddiqi and Husen
[161] reported that the shape, size and stability of PdNPs depends on concentrations of plant extract, pH, temperature and incubation time. Plant sources including the extracts of leaves, flowers, seeds, fruits, peels and roots were extensively utilized to synthesize Pd nanoparticles.
Gurunathan et al.
[162] synthesized Pd nanoparticles from a plant extract of
Evolvulus alsinoides. This plant extract has various natural antioxidants, including alkaloids, flavonoids, saponins, tannin, steroids and phenol, which work as reducing and capping tools to synthesize Pd nanoparticles. Nasrollahzadeh et al.
[163] used the leaf extract of
Hippophae rhamnoides to synthesize PdNPs because the leaf extract has polyphenols that play an important role as reducing and capping agents for nanostructure development. The formed NPs were found to be spherically shaped and ranging from 2.5 nm to 14 nm, which was confirmed by TEM. Pd nanoparticles have been synthesized from the root extract of
Salvadora persica, which contains polyphenols that act as reductant and stabilizing agents
[164]. The average particle size of synthesized NPs was 10 nm at 90°C, which was revealed from the UV spectrum of the colloidal solution. Palladium NPs were generated with the bark extract of
Cinnamomum zeylanicum and PdCl
2 solution at 30 °C
[165]. Khan et al.
[166] carried out the plant-assisted synthesis of PdNPs from the extract of
Pulicaria glutinosa and PdCl
2. After stirring the mixture of PdCl
2 + extract at 90 °C for 2 h, the colour changed from pale yellow to dark brown, indicating the production of PdNPs, validated by UV–visible spectroscopy. A TEM monograph revealed the particle size of the obtained Pd nanoparticles ranged between 20 nm and 25 nm. The particle size of the synthesized NPs was found to be between 10 nm and 50 nm. The biosynthesis of Pd nanoparticles from the leafy solution of
Glycine max has been reported
[167]. The shape of the particles was found to be uniformly spherical with a 15 nm diameter, which was confirmed by TEM micrograph. Jia et al.
[168] performed the synthesis of Pd nanoparticles utilizing
Gardenia jasminoides extract containing various antioxidants such as geniposide, crocins, crocetin and chlorogenic acid, which reduce and stabilize the nanoparticles. There are some reports on plant-assisted synthesis of palladium nanoparticles listed below in
Table 5.
Table 5. Plant-assisted synthesis of palladium nanoparticles.
Plant Name |
Parts Used |
Size (nm) |
Shapes |
Reference |
Peganum harmala |
Seed |
22.5 ± 5.7 |
Spherical |
[169] |
Coleus amboinicus |
Leaves |
40–50 |
Spherical |
[170] |
Anogeissus latifolia |
Gum ghatti |
4.8 ± 1.6 |
Spherical |
[171] |
Filicium decipiens |
Leaves |
2–22 |
Spherical |
[172] |
Cinnamomum camphora |
Leaves |
3.2–6 |
Multiple |
[173] |
Pulicariaglutinosa |
Leaves |
3–5 |
Spherical |
[166] |
Musa paradisica |
Peeled banana |
50 |
Crystalline |
[174] |
Cinnamom zeylanicum |
Bark |
15–20 |
Crystalline |
[165] |
Catharanthus roseus |
Leaves |
38 |
Spherical |
[175] |
Curcuma longa |
Tuber |
10–15 |
Spherical |
[176] |
Glycine max |
Leaves |
15 |
Spherical |
[167] |