Selective interaction between phytomediated anionic silver nanoparticles and mercury leading to amalgam formation enables highly sensitive, colorimetric and memristor-based detection of mercury.

Presently, nanotechnology is being foreseen to play an important role in developing analytical assays for the detection of pollutants like mercury (Hg2+). In this study, Kokum fruit mediated silver nanoparticles (AgNPs) were differentially centrifuged to prepare anionic, monodispersed AgNPs to develop a highly sensitive, colorimetric and memristor-based assay for detection of Hg2+ in water samples. The investigation of the highly selective reaction between AgNPs and Hg2+ using HAADF-STEM images and EDS spectrum indicated the amalgam formation through etching and under potential deposition which resulted in a visible color change from brown to colorless, change in SPR intensity and also change in memristive switching like property of AgNPs. The developed colorimetric assay detected Hg2+ with a limit of detection (LOD) of 6.2 ppb and limit of quantification (LOQ) of 18.9 ppb and, quantitatively recovered Hg2+ with good accuracy and precision (RSD < 2%). Further, the test of memristive switching like property of AgNPs demonstrated frequency-dependent shrinkage of I-V hysteresis loop indicating memristive switching like property. The test of the sensitivity of Hg2+ detection was estimated to be 8.7 ppb as the LOD and 26.4 ppb as LOQ. Like the colorimetric assay, the memristor-based assay also recovered Hg2+ with good accuracy and precision.

Garcinia indica mediated biogenic synthesis of silver nanoparticles with antibacterial and antioxidant activities.

This reports the optimization of various parameters for biogenic synthesis of Silver nanoparticles using fruit extract of Garcinia indica, popularly known as Kokum. For optimization, the effects of various parameters such as concentration of AgNO3, ratio of AgNO3 to extract, pH, incubation temperature and time were varied and studied for their effect on synthesis. 1.5 mM AgNO3, 1:1 ratio of AgNO3 to Kokum fruit extract, pH 10, incubation of reaction mixtures at 37 °C for 24 h were the optimum parameter for biogenic synthesis. The biogenic AgNPs were then characterized by UV-vis absorption spectroscopy, fourier transform infra-red (FT-IR) spectroscopy, field emission scanning electron microscope (FE-SEM) imaging, energy dispersive X-ray (EDS) spectrometer, X-ray powder diffractometer (XRD), transmission electron microscope (TEM) imaging and the selected area electron diffraction (SAED) pattern. The biogenic AgNPs alone and in combination with Tetracyclin showed antibacterial activity against the four of seven tested bacteria. In addition, biogenic AgNPs also demonstrated good antioxidant activities such as DPPH, hydrogen peroxide, nitric oxide (NO) radical scavenging and reducing power activities. This study demonstrates that Garcinia indica fruit extract can be used for biogenic production of AgNPs with potential antibacterial and antioxidant activities that can be exploited for commercial biomedical application.