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

Abstract

In this study, silver oxide nanoparticles (Ag 2 O-NPs) were synthesized from silver nitrate using green amaranth leaf extract as reducing agent. The degradation of caffeine and inactivation of Escherichia coli by Ag 2 O-NPs was studied under compact uorescent lamp illumination irradiation. Apart from that, the antibacterial and antioxidant activities of Ag 2 O-NPs were also examined. Synthesized Ag 2 O-NPs were shaped like monodispersed husk, and cubic structured with surface area and average particle size was detected to be 100.21 (m 2 /g) and 81 nm respectively. Antioxidant e cacy of the Ag 2 O-NPs was evaluated using 1, 1-diphenyl-2-picrylhydrazyl and 91% inhibition was achieved with 100 µg Ag 2 O-NPs.Bacteriocidic propensity of Ag 2 O-NPs was examined against the S. aureus and P. aeruginosa by disc diffusion, minimum inhibitory concentration (MIC), Live and dead assay. It was observed that the NPs have 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 Ag 2 O NPs. These results indicate that Ag 2 O NPs can be employed in environmental applications like harmful bacteria inactivation and organic pollutants degradation.

Green, novel, and one-step synthesis of silver oxide nanoparticles: antimicrobial activity, synergism with antibiotics, and cytotoxic studies

“…The authors reported that concentrations of 50 and 100 mg mL À1 of nanocrystals of Ag 2 O do not affect cell viability over 24 h. 30 However, Muthukumar et al suggest that concentrations below 30 mg mL À1 Ag 2 ONPs may be used for biomedical applications since higher concentrations would be dangerous for non-cancerous cells. 25 In summary, cytotoxic studies showed that the combination of the concentrations 0.5/1.0 mg mL À1 of Ag 2 ONPs/antibiotics respectively, do not affect the cell viability of HDF (Fig. 8).…”

“…24 It is important to emphasize that the MIC exhibited by the present Ag 2 ONPs against reference strains and resistant and MDR clinical isolates, were in the lower range of MIC values previously reported for Ag 2 ONPs synthesized by physical and biological methods. 24,25,29…”

“…16,17 Another offered benefit when using combined therapy is that the accumulation of various mutations is required for bacteria to develop resistance to metal and metal oxides NPs, due to their multi-target activity. 18,19 In recent years, silver oxide NPs (Ag 2 ONPs) have attracted great scientific interest not only for being excellent photocatalysts, 20 but also for their antimicrobial [21][22][23][24][25][26][27][28][29] and healing effects. 22 For the synthesis of Ag 2 ONPs, the use of chemical approaches such as the sol-gel method 21 and chemical reduction using 2-dimethyl amino ethanol as the reducing agent, 23 as well as physical methods assisted by sonication 24 have been reported.…”

“…22 For the synthesis of Ag 2 ONPs, the use of chemical approaches such as the sol–gel method 21 and chemical reduction using 2-dimethyl amino ethanol as the reducing agent, 23 as well as physical methods assisted by sonication 24 have been reported. However, the scientific community has leaned towards the use of green methods, including different biological sources such as extracts from medicinal plants, among these Lippia citriodora , 22 green amaranth leaf, 25 Ficus benghalensis , 26 Artocarpus heterophyllus , 27 Centella asiatica and Tridax; 28 as well as microorganisms such as Kitasatospora albolonga 29 and Xanthomonas sp. 30 There is evidence that the combination of Ag 2 ONPs with moxifloxacin enhances the antimicrobial effect against susceptible microorganisms; unfortunately, the researchers evaluated the effect of the combination by the agar well diffusion method, 23 which has the inconvenient of using fixed concentrations of NPs and antibiotic, and a range of concentrations is not studied.…”

Boosting charge migration in V2O5 nanorods by niobium doping for enhanced photocatalytic activity

“…Conventional waste water treatment processes have failed to successfully degrade caffeine and hence it is imperative to design new technologies for efficient treatment of caffeine-contaminated wastewater. In this respect, there have been a few reports on the successful degradation of caffeine using photocatalysts like Ag 2 O, Mg-doped ZnO-Al 2 O 3 , and NiO/TiO 2 -F. [38][39][40] However, the reports are very scanty in number and much more research work is necessary to augment the applicability of photocatalysis in the treatment of caffeine-contaminated wastewater. Hence, in this work caffeine was chosen as a model pollutant to establish a technology for efficient degradation of caffeine and also to study the photocatalytic activity of the developed Nb-doped V 2 O 5 samples.…”