Green synthesis of silver nanoparticles using Lepidium sativum seed mucilage as a bioreductant/capping agent for efficient antibacterial and photocatalytic activities

Abstract

Contamination of aquatic resources with organic dyes and pathogenic bacteria ranks among the most serious threats to human survival and the environment. The current work investigated L. sativum seed mucilage as a reducing and capping agent for Ag NPs. From UV–vis spectroscopy, the characteristic surface plasmon resonance peak and the band gap energy of as-fabricated NPs were 440 nm and 2.07 eV, respectively. SEM revealed irregular-shaped NPs with an average diameter of 73.85 nm and EDX disclosed Ag along with C, O, and Si from mucilage’s biomolecules. The antibacterial and antibiofilm results showed higher inhibitory effects against the Gram-positive (B. cereus) than the Gram-negative (E. coli, and E. aerogenes) bacteria. The biosynthesized NPs were impressive in degrading methylene blue (MB, 89.45 %) and methyl orange (MO, 84.78 %) under optimized conditions viz., dye solution (20 ppm), photocatalyst dose (5 mg), light intensity (UV index of 10 +), and irradiation time (120 min). The kinetic data strongly supported the pseudo-first order model with maximum adsorption capacities of 787.40 and 724.64 mg/g for MB and MO, respectively as determined through the Langmuir isotherm model. The photocatalyst exhibited sufficient stability even after six repeated cycles, highlighting its suitability for industrial and commercial applications.