Nano Ag0 decorated-silica matrix for the remediation of environmental pollutants: Visible-light driven Cr(VI) photoreduction, photodegradation of organic dye, nanomolar Hg2+ detection, and antimicrobial applications

Abstract

BackgroundWater contamination with toxic heavy metals and dye colorants causes a harmful effect on all living organisms and affect ecosystem adversely. In this study, nano-Ag0 decorated porous silica matrix conjugated with alanine was investigated for multifunctionality including mercury (Hg2+) detection, visible-light photocatalytic performance for organic dye degradation, Cr(VI) photoreduction and antibacterial activity. MethodHRTEM and XRD verified the anchoring of crystalline Ag0 on silica matrix with devoid of impure phases. SEM and XPS analysis was carried out before and after Hg2+ interaction with nano-Ag0/silica probe to understand the variation in morphology, interactions, chemical states, and intrinsic mechanism. Significant findingsThe LOD of the present probe for the detection of Hg2+ was 12 nM. The Ag0-silica NPs incorporated paper strip and agarose gel was prepared and used for mercury detection by the naked eye. The silica stabilized Ag particles form conjugate with alanine and when it interacts with Hg2+, mercury oxidizes the Ag(0) to Ag(I) by amalgam formation resulting in pale-yellow color changing to colorless. Environmental parameters such as salinity, pH and temperature did not influence Hg2+ detection. In addition, photocatalytic activity of nano-Ag0/silica was tested with cationic methylene blue (MB) dye under visible light irradiation that showed 90.3% degradation. Further, the nano-Ag0/silica exhibited significantly superior Cr(VI) photoreduction activity. In addition, gram positive and gram negative bacterial strains showed higher growth inhibition upon exposure to Ag0-silica NPs.