Development of a sensor for the selective detection of manganese in aqueous media using grapefruit peel...

The presence of Mn²⁺ in aquatic systems even at trace ppm concentrations poses safety concerns; thus, it is indispensable to develop an accurate, sensitive, and selective sensor for Mn²⁺ detection. The use of colorimetric plasmonic nanoparticles offers a suitable approach. Herein, silver nanoparticles were synthesized using pectin (AgGPe NPs), in which the inputs of pectin and AgNO₃ and the volume of NaOH were optimized in the reaction to obtain NPs within a size range of 5-45 nm and a zeta potential of -34.26 mV, which were stable for up to 2.5 months at 4 °C. AgGPe NPs were characterized by UV-vis analysis, which revealed a surface plasmon resonance (SPR) peak at 405 nm, along with FTIR and XRD measurements. The formed silver nanoparticles showed specific recognition to Mn²⁺ ions by changing the color from yellow to brown, and the sensing performance was optimized in terms of the input volume of AgGPe NPs, incubation time and pH. The nanocomposite gave a limit of detection (LOD) of 0.5065 ppm, accompanied by a practicable detection for drinking water and Tau Hu canal water with good recoveries. In conclusion, the green-synthesized AgGPe NPs offer a cost-effective and environmentally friendly approach for Mn²⁺ detection and have good prospects for future applications.