Green synthesis and characterization of bioactive silver nanoparticles from Stachys tibetica

Abstract

Stachys tibetica, a significant medicinal plant was collected from Ladakh (India) and subjected to extraction. The extract was titrated with AgNO₃ at 50ºC to obtain silver nanoparticles with plant extract acts as a reducing and capping agent. The eco-friendly synthetic procedure utilizes the phytochemicals in Stachys tibetica, ensuring a sustainable and non-toxic approach to nanoparticle production. The characterization of the silver nanoparticles was conducted using various techniques, including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and dynamic light scattering (DLS). Field emission scanning electron microscopy (FE-SEM) was utilized to examine the surface morphology, revealing the irregular and rugged spherical shape of the synthesized nanoparticles. Stachys tibetica-derived silver nanoparticles (AgNPs) act as a versatile and robust multifunctional material with proficient bioactivity and catalytic properties. The synthesized silver nanoparticles displayed effective antioxidant and antimicrobial properties against Bacillus Cereus, Pseudomonas, Escherichia coli, and S.Aureus. Additionally, the green nanoparticles degraded Rhodamine-B under sunlight irradiation within 1 h at a rate constant of 0.066 min^{- 1}.

Keywords: Stachys Tibetica; FE-SEM; Rhodamine-b; Silver nanoparticles; XRD.

Scheme 1

Green synthesis of Silver nanoparticle from Aqueous extract of S. Tibetica.

Fig. 1

(a) FTIR spectra of plant extract and silver nanoparticle (b) XRD pattern of AgNP.

Fig. 2

(a,b) SEM images of Ag nanoparticles at 100 nm and 200 nm. (c) EDX of the nanoparticle. (d and e) Elemental mapping images of carbon and silver respectively revealing a uniform distribution of carbon and silver.

Fig. 3

(a) Average particle size as obtained from DLS measurements. (b) Percentage weight composition of different elements.

Fig. 4

Antibacterial bacterial activity against four bacterial strains (a) Bacillus cereus (b) Pseudomonas (c) E. coli (d) S. aureus (e) Bar graph plot of zone of inhibition of four bacterial strains.

Fig. 5

Percentage radical scavenging activity of ascorbic acid, plant extract and AgNP.

Fig. 6

(a) The gradual decrease in intensity of absorption peak at 550 nm with irradiation time. (b) The plot of - versus time and value of rate constant is found to be 0.06667 min^− 1 (c) Gradual decrease in the concentration of Rhodamine-b with time.