Enhanced antimicrobial activity of silver nanoparticles with controlled particle size by pH variation

• Spherical silver nanoparticles were prepared by chemical reduction method.
• Increment of reaction solution pH causes particles size reduction.
• Photoluminescence emission intensity increased with the increase of pH.
• It exhibited an effective antimicrobial property against the tested pathogens.

PVA capped spherical silver nanoparticles (AgNPs) were synthesized at various pH conditions of reaction solution by chemical reduction method. Tuning of reaction solution pH in a narrow range could have a profound effect on particle size. The synthesized AgNPs have been characterized by studying their structural, morphological, optical and antimicrobial properties. Crystallite size decrement with the increase of pH was confirmed by X-ray diffraction analysis. UV–vis spectra showed single surface plasmon resonance (SPR) peak at ~ 420 nm and a blue shift in SPR was elicited with increment of pH. AgNPs were found to be photoluminescent and enhancement in photoluminescence intensity was observed with the increase in the reaction solution of pH. Fourier transform infrared spectroscopy (FTIR) measurements indicated that the nanoparticles were capped by PVA. The synthesized AgNPs displayed potent antimicrobial activity against Escherichia coli, Pseudomonas sp., Aspergillus niger and Penicillium sp. with particle size decrement.

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