Table 1.

Green synthesis of metallic nanoparticles synthesized from conifer extracts and their characterization through different analytical techniques.

Types of Conifer	Family	Parts of Plant Used	Types of Metallic NPs	Reducing Agent	Stabilizing Agent	Reaction Time	Reaction Temp	Characterization	Shape	Size (nm)	Stability	Ref.
Picea abies L.	Pinaceae	Bark	Silver	Phenolic compounds	Phenolic compounds	3 h	60 °C	FTIR, UV–Vis, TEM	Sphere and Polygonal	44	ND	[51]
Pinus eldarica	Pinaceae	Bark	Silver	Bark extract	Bark extract	ND	RT	UV–Vis, TEM	Sphere	10–40	ND	[52]
Taxus yunnanensis	Taxaceae	Callus	Silver	Callus extract	Callus extract	120 min	NS	XRD, TEM, FTIR,	Sphere	6.4–27.2	More than 2 weeks	[30]
Pinus merkusii Jungh Et De Vriese	Pinaceae	Cone/Flower	Copper	Phenolic groups	Phenolic groups	NS	NS	FTIR, SEM	ND	20–35	ND	[53]
Juniperus communis L.	Cupressaceae	Berry/Cone	Gold	Carbonyl, Carboxyl and Hydroxyl groups	Polyphenols	24 h	RT	AFM, ATR-FTIR, EDX, UV–Vis, TEM,	Sphere and Triangle	10–50	ND	[54,55]
Pinus densiflora	Pinaceae	Cone	Silver	Hydroxyl and Carbonyl groups	Phytochemicals	15 min	RT	UV–Vis, TEM, FTIR, XRD	Oval and Triangular	40–70	ND	[56]
Pinus merkusii Jungh Et De Vriese	Pinaceae	Cone	Silver	Phenolic hydroxyl groups	Cone flower	60 min	60 °C	UV–Vis, TEM, FTIR	Sphere	8–23	ND	[57]
Araucaria heterophylla	Araucariaceae	Gum	Silver	Gum extract	Gum extract	NS	NS	AFM, EDX, FTIR, SEM, UV–Vis	ND	<25	ND	[48]
Araucaria heterophylla	Araucariaceae	Gum	Silver	Gum extract	Gum extract	NS	RT	UV–Vis, FTIR, SEM, EDX, AFM	Sphere	<30	ND	[58]
Taxus baccata	Taxaceae	Leaf/Needle	Gold	Needle extract	Needle extract	24 h	25 °C	UV–Vis, HRTEM, EDX, AFM	Sphere, Semi-sphere, Hexagonal and Triangle	<20	Several months	[59]
Thuja orientalis	Cupressaceae	Leaf/Needle	Gold	Phytochemicals	Phytochemicals	10 min	RT	EDX, FTIR, XRD, TEM, UV–Vis,	Sphere	5–94	ND	[60]
Pinus eldarica	Pinaceae	Leaf/Needle	Iron Oxide	Leaf extract	Leaf extract	30 min	RT	TEM, FTIR, XRD, EDX	Sphere	8–34	ND	[61]
Cupressus goveniana	Cupressaceae	Leaf/Needle	Silver	Carboxyl and Hydroxyl and Amine groups	Phytochemicals	60 min	80 °C	UV–Vis, FTIR, SEM	Sphere	67–200	4 months	[62]
Cupressus sempervirens	Cupressaceae	Leaf/Needle	Silver	Carbonyl and Hydroxyl groups	Phytochemicals	12 h	RT	UV–Vis, TEM, XRD, FTIR	Sphere, Hexahedral, Oval and Triangle	10–80	ND	[63]
Cupressus torulosa D. Don	Cupressaceae	Leaf/Needle	Silver	Leaf extract	Leaf extract	24 h	NS	UV–Vis, SEM, XRD, TEM	Sphere	NS	ND	[64]
Juniperus procera	Cupressaceae	Leaves	Silver	Phenolic acids, chlorogenic acid, flavonoids, caffeoylquinic acids	Phytochemicals	24 h	RT	UV–Vis SEM, FTIR	Spherical, cubical	30–90	ND	[65]
Juniperus chinensis	Cupressaceae	Leaf/Needle	Silver	Proteins	Phytochemicals	60 min	100 °C	EDX, XRD, HRTEM, UV–Vis	NS	18–25	ND	[46]
Taxus baccata	Taxaceae	Leaf/Needle	Silver	Proteins and Terpenoids	Phytochemicals	NS	10 and 30 °C	UV–Vis, TEM, AFM	Triangular and Hexagonal	75.1	Six months	[34]
Thuja occidentalis L.	Cupressaceae	Leaf/Needle	Silver	Carbonyl, Carboxyl, Aliphatic and Aromatic amine groups	Carbonyl, Carboxyl, Aliphatic and Aromatic amine groups	35–40 min	60 °C	FTIR, UV–Vis, SEM, XRD, TEM	Sphere	<30	ND	[66]
Thuja occidentalis	Cupressaceae	Leaf/Needle	Silver	Hydroxyl and Carbonyl groups	Phytochemicals	3–4 h	RT	XRD, FTIR	ND	41.48	ND	[67]
Thuja occidentalis	Cupressaceae	Leaf/Needle	Silver	Leaf extract	Leaf extract	3–4 h	RT	UV–Vis, FTIR	ND	ND	ND	[68]
Thuja occidentalis	Cupressaceae	Leaf/Needle	Silver	Leaf extract	Leaf extract	NS	NS	UV–Vis, XRD, HRTEM	ND	7–14	ND	[69]
Thuja occidentalis	Cupressaceae	Leaf/Needle	Silver	Leaf extract	Leaf extract	NS	RT	UV–Vis, XRD, TEM	ND	10–15	ND	[70]
Torreya nucifera	Taxaceae	Leaf/Needle	Silver	Proteins	Proteins	24 hrs	20 °C	FTIR, XRD, TEM, UV–Vis,	Sphere	10–125	ND	[71]
Taxus baccata	Taxaceae	Leaf/Needle	Zinc Oxide	Proteins	Proteins	NS	NS	UV–Vis, SEM, TEM, FTIR	Hexagonal	20–27.64	ND	[72]
Pinus kesiya	Pinaceae	Pollen	Gold	Pollen extract	Pollen extract	60 min	RT	UV–Vis	ND	ND	3 months	[73]
Pinus wallichiana	Pinaceae	Stem	Silver	Hydroxyl groups	Phytochemicals	30 min	55 °C	EDX, FTIR, SEM, UV–Vis, XRD	Sphere	10–30	ND	[74]
Abies spectabilis	Pinaceae	NS	Gold	Polyphenols	Polyphenols	24 h	29 °C	AFM, DLS, EDX, FTIR, UV–Vis, XRD,	Sphere	20–200	ND	[47]
Thuja occidentalis	Cupressaceae	NS	Silver	Carbonyl groups	Flavonoids, Terpenoids and Thiamines	10 min	27 °C	DLS, TEM, XRD, UV–Vis,	Sphere	122.8	ND	[75]

NS—not specified; AFM—Atomic force microscopy; ATR-FTIR—Attenuated total reflection-Fourier-transform infrared spectroscopy; DLS—Dynamic light scattering; EDX—Energy-dispersive X-ray spectroscopy; FESEM—Field emission electron microscope; HRTEM—High-resolution transmission electron microscopy; FT-IR—Fourier-transform infrared spectroscopy; RT—room temperature; SEM—Scanning electron microscopy; TEM—Transmission electron microscopy; UV–Vis—Ultraviolet-visible spectroscopy; XRD—X-ray powder diffraction. ND—Not determined.