Characterization of the biosynthesized intracellular and extracellular plasmonic silver nanoparticles using Bacillus cereus and their catalytic reduction of methylene blue

Abstract

The biosynthesis of silver nanoparticles (Ag NPs) has been studied in detail using two different approaches. For the first time, Bacillus cereus is used for one-pot biosynthesis of capsulated Ag NPs, using both intracellular and extracellular approaches. To discriminate between the produced nanostructures by these two approaches, their structures, nanomorphologies, optical properties, hydrodynamic sizes and zeta potentials are studied using different techniques. Fourier-transform infrared spectroscopy was used to identify the bioactive components responsible for the reduction of Ag+ ions into Ag and the growth of stable Ag NPs. Scanning and transmission electron microscopy images displayed spherical and polygon nanomorphology for the intracellular and extracellular biosynthesized Ag NPs. For intracellular and extracellular biosynthesized Ag NPs, a face-centred cubic structure was observed, with average crystallite sizes of 45.4 and 90.8 nm, respectively. In comparison to the noncatalytic reduction test, the catalytic activities of intracellular and extracellular biosynthesized Ag NPs were explored for the reduction of highly concentrated MB dye solution. Extracellular Ag NPs achieved 100% MB reduction efficacy after around 80 min, compared to 50.6% and 24.1% in the presence and absence of intracellular Ag NPs, respectively. The rate of MB reduction was boosted by 22 times with the extracellular catalyst, and by 3 times with the intracellular catalyst. Therefore, the extracellular production process of Ag NPs utilizing Bacillus cereus bacteria might be applied in the industry as a cost-effective way for eliminating the toxic MB dye.

Bioinspired 5-caffeoylquinic acid capped silver nanoparticles using Coffee arabica leaf extract for high-sensitive cysteine detection

“…The bands in the region 1300–1000 cm −1 are assigned to the presence of CGAs and these are attributed to the polysaccharides and other carbohydrates 43 . The stretching modes of Ag–O and Ag–C can be seen in the wavenumber regions 1353, 590 and 478 cm −1 which confirms the reduction of Ag + to AgNPs 47 , 48 . Hence, from the outcome of IR studies, it is proposed that CAE–AgNPs are stabilized via electrostatic interactions of carboxylate group of 5-CQA and its oxidized quinine form (Fig.…”

Bioinspired 5-caffeoylquinic acid capped silver nanoparticles using Coffee arabica leaf extract for high-sensitive cysteine detection

“…The bands in the region 1300 − 1000 cm -1 are assigned to the presence of CGAs and these are attributed to the polysaccharides and other carbohydrates 35 . The stretching modes of Ag-O and Ag-C can be seen in the wavenumber regions 1353, 590 and 478 cm -1 which con rms the reduction of Ag + to AgNPs 37,40,41 . Hence, from the outcome of IR studies, it is proposed that CAE-AgNPs are stabilized via electrostatic interactions of carboxylate group of 5-CQA and its oxidized quinine form (Fig.…”

“…Similarly, for CAE-AgNPs, a new band appears at 230 cm -1 along with the other parent bands which show some shift in positions and variation in intensities. Ag-O bending vibrations 40 are evident from the newly emerged band at 230 cm -1 in Fig. 5b.…”

Extracellular biosynthesis of silver nanoparticles using cell suspension ofRhodococcus fascians

“…It has been proposed that AgNPs are synthesized by enzymatic reduction mediated by NADPH-dependent nitrate reductase in the microorganisms. This enzyme has been shown to convert silver ions to metallic silver when nitrate ions activate it [52]. Following the colour shift, it has been hypothesized that DNA, sulfur-containing proteins and NADH-dependent nitrate reductase are involved in producing AgNPs by bio-reducting silver ions to metallic silver.…”