Psidium guajava leaf extract mediated green synthesis of silver nanoparticles and its application in antibacterial coatings.

In this study, Psidium guajava (P. guajava) leaf extract-assisted silver nanoparticles (AgNPs) were synthesized and their antibacterial activities were investigated. The synthesized green AgNPs were characterized by various analytical techniques including UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, etc. From the UV-Vis spectroscopic analysis, the formation of nanoparticles has been confirmed by the color change from light yellow to reddish brown of the solution due to the excitation of the surface plasmon resonance peak at 430 nm. In addition, the FTIR study showed the reduction of Ag ions owing to the presence of biomolecules in the leaf extract, which acted as reducing as well as capping agents. Furthermore, XRD analysis reveals the identified 2θ peaks of AgNPs at ∼39° with cubic structure. The FE-SEM micrograph illustrated the material was formed in nano-dimensions, with an average particle size of ∼12 nm and almost spherical in shape. Moreover, P. guajava-mediated AgNPs demonstrated good antibacterial activity against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacterial strains. The synthesis was performed by a bio-reduction process where a bioactive agent is responsible for reducing metallic ions to metallic nanoparticles as an eco-friendly, cost-effective, non-toxic, one-step, and sustainable method. Therefore, this study may create an imperative synthetic route for the fabrication of green-AgNPs and their application in antibacterial coatings in cotton textiles.

Influence of Mg substitution on structural, magnetic and electrical properties of Zn-Cu ferrites.

Studies on Mg substituted Zn-Cu ferrites with chemical formula of Zn0.6Cu0.4-xMgxFe2O4 were synthesized by solid-state reaction technique. The structural phase of all the samples is characterized by XRD, show single phased cubic spinel structure. Density of the samples increases with the increase of Mg quantity. Average grain diameter decreases with increasing Mg content. All samples show soft ferromagnetic behavior as confirmed from the M-H hysteresis loop obtained from the VSM analysis. Thesaturation magnetization decreases with increasing Mg quantity. Increasing and decreasing trend of coercivity with the increase of Mg quantityis observed, which led to the slightly hard magnetic phase. The high frequencies create more effective for the ferrite grains of advanced conductivity and minor dielectric constant for all the samples but the AC electrical resistivity and dielectric constant are initiate to be more operational at lower frequencies. The variation of resistivity, dielectric constant with the Mg concentration is completely related to the porosity and bulk density.