Citric acid assisted synthesis of manganese tungstate nanoparticles for simultaneous electrochemical sensing of heavy metal ions

Manganese tungstate nanoparticles (NPs) were successfully synthesized via a simple and cost effective citric acid assisted solution combustion method. Rietveld refinement of PXRD pattern indicates the formation of pure wolframite phase of manganese tungstate. Transmission electron microscope (TEM) analyses confirm the spherical shaped nanoparticles with average particle size ranging from 12 to 26 nm. The ultra-light combustion derived manganese tungstate NPs exhibits mesoporous nature with the estimated band gap 2.9 eV. The synthesized NPs were found to be an excellent electrode modifier for the simultaneous detection of Pb(II), Cd(II), Cu(II) and Hg(II) ions at nanomolar (nM) concentration. The present electrochemical sensor exhibits wide linearity of 10 – 500 nM with limit of detection based on 3σ method is 3.3, 3.5, 2.9 and 3.1 nM for Pb(II), Cd(II), Cu(II) and Hg(II) respectively. Additionally, room temperature photoluminescence emission spectrum exhibits an intense band at 445 nm that can be attributed to 1A1 ground-state to the high vibration 1T2 energy levels of distorted [WO6] octahedral groups.