Novel colorimetric sensor for mercury (II) based on layer-by-layer assembly of unmodified silver triangular nanoplates

Abstract

A simple layer-by-layer deposition technique was used to fabricate the multilayer thin films of unmodified silver triangular nanoplates (AgTNPs). The multilayer of AgTNPs thin films were fabricated by alternate deposition of each anionic sodium citrate stabilized AgTNPs and cationic poly(diallyldimethylammonium chloride). All prepared AgTNPs multilayer thin films were exhibited a strong plasmon band at the wavelength of 667 nm, which confirmed the formation of AgTNPs onto the substrate. The characteristics of the multilayer thin films were investigated using contact angle measurement, UV–visible spectroscopy, X-ray diffraction analysis (XRD), atomic force microscope (AFM) and field emission scanning electron microscope (FESEM). As these films are to be used as a mercury (II) colorimetric sensor, the changes in optical properties of the films were evaluated for various mercury (II) concentrations. AgTNPs assembled into thin films showed a strong color shift from blue to mauve and colorless when exposed to mercury (II). The constructed multilayer thin films exhibited excellent color changes of mercury (II) with a linear range between 0.5 and 20 ppm. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.45 ± 0.002 and 1.52 ± 0.002 ppm, respectively. The recovery values of AgTNPs multilayer thin films are satisfactory in the range of 100.1%–106.4% when applied to determining mercury (II) in water samples.