Photocatalytic degradation of caffeine and E. coli inactivation using silver oxide nanoparticles obtained by a facile green co-reduction method

Harshiny Muthukumar,Santosh Kumar Palanirajan,Sathyanarayana N Gummadi,Pugazhendhi Arivalagan,Manoj Kumar Shanmugam

doi:10.1007/s10098-021-02135-7

Abstract

In this study, silver oxide nanoparticles (Ag2O-NPs) were synthesized from silver nitrate using green amaranth leaf extract as a reducing agent. The degradation of caffeine and inactivation of Escherichia coli (E. coli) by Ag2O-NPs was studied under compact fluorescent lamp illumination irradiation. Apart from that, the antibacterial and antioxidant activities of Ag2O-NPs were also examined. Synthesized Ag2O-NPs were shaped like monodispersed husk, and cubic structured with surface area, and average particle size was detected to be 100.21 (m2/g) and 81 nm, respectively. Antioxidant efficacy of the Ag2O-NPs was evaluated using 1, 1-diphenyl-2-picrylhydrazyl, and 91% inhibition was achieved with 100 µg Ag2O-NPs. Cell viability assay demonstrated that Ag2O-NPs showed less cytotoxicity for human embryonic kidney (HEK 293) cells. The bacteriocidic propensity of Ag2O-NPs was examined against the S. aureus and P. aeruginosa by disk diffusion, minimum inhibitory concentration (MIC), live and dead assay. It was observed that the NPs have a higher bactericidal effect on Gram-negative as compared to Gram-positive bacteria. Up to 96%, photocatalytic inactivation of E. coli was achieved using 30 µg/mL of NPs. Photocatalytic degradation of caffeine (50 ppm initial concentration) was observed to be 99% at pH 9 in 15 h using 50 mg/L of Ag2O NPs. These results indicate that Ag2O NPs can be employed in environmental applications like harmful bacteria inactivation and organic pollutants degradation.

Highlights

The rising rate of drug-resistance to current antibiotics microbial infections and adverse toxic effects of some antibiotics warranted alternative of new drugs (Wang et al 2018; Roy et al 2019)
The UV–visible spectra exhibited a distinct peak at 432 nm and it was due to the surface plasmon resonance (SPR) of Ag2O-NPs and the peak at 278 nm could be due to oxidized polyphenols in NPs (Fig. 1A)
Analytical techniques confirmed that NPs have husk shape with cubic phase structure, large surface, less aggregation and smaller sizes and these properties made it as a better physicochemical nanomaterial

Summary

Introduction

The rising rate of drug-resistance to current antibiotics microbial infections and adverse toxic effects of some antibiotics warranted alternative of new drugs (Wang et al 2018; Roy et al 2019). In this regard, nanotechnology is a forthcoming research topic in area of infectious disease treatment with the advancement of nano-scale substances with enhanced antimicrobial activities against multidrugresistant microbes (Shanmuganathan et al 2018). Silver nanoparticles been extensively used as antimicrobial and drug delivery agents as well as more efficient photocatalyst under visible light compared to many other metal oxides (Yang et al 2015). Among the plant extracts studied, aqueous leaf extracts of Amaranthus. sp. hold many organic compounds and have been used for the synthesis of NPs (Muthukumar et al 2020a)

Methods

Results

Conclusion