Graphitic carbon nitride embedded-Ag nanoparticle decorated-ZnWO4 nanocomposite-based photoluminescence sensing of Hg2+

Abstract

The adverse effects of the advancement of civilization have damaged the environment significantly by heavy metal ion toxicity, empoisoning soil, water, food, etc. In this work, Ag loaded metal tungstate–organic framework-based nanomaterials (g-C₃N₄/Ag/ZnWO₄) which can generate more and more oxygen defects have played a crucial role in detecting selective toxic metal ions in solution. The PL intensity of the samples increases with compositing ZnWO₄ with g-C₃N₄ and Ag, as the recombination of excited electrons with the holes at the oxygen vacancy sites increases. Here, a novel strategy has been adopted to develop a nanocomposite assembly of Ag-loaded ZnWO₄ nano-rods with π conjugated sp² hybridized g-C₃N₄ for fluorescence detection of Hg²⁺. The prepared nanocomposites have displayed great fluorescence catalysis for Hg²⁺ sensing in terms of selectivity, sensitivity, activity, and reaction kinetics. A linear relationship in the range of 0 nM to 2 μM has been obtained for the detection of Hg²⁺ in a buffer solution of pH = 7.2 (phosphate buffer) by the fluorophore g-C₃N₄/Ag/ZnWO₄ and the minimum detection limit was found to be 0.23 nM. Furthermore, the synthesized nanocomposites were applied for Hg²⁺ detection in few real samples (pond water, sewage water, etc.), signifying their potential application in routine Hg²⁺ analysis. The probable mechanistic pathway for the sensing of Hg²⁺ by grafting the metal ion has also been studied in detail. Based on this mechanism an electronic computing system using an Implication circuit device has been constructed from the molecular information processing and a probable fluorescence mechanism (Jablonski diagram) was explored in which the material was found to possess some room-temperature phosphorescence (RTP).