The presence of a high concentration of silver metal ions can lead to soil and water toxicity, resulting in skin irritation, nausea, diarrhoea, argyria, kidney, neuronal and liver dysfunction. The study highlights the development of sensitive and selective nano sensors for the detection of toxic metal ion Ag+ in aqueous solution. Gum acacia-capped selenium nanoparticles (GA-SeNPs) were synthesized using the chemical reduction method which is a simple, eco-friendly method employing ascorbic acid as a reducing agent. The nanoparticles were characterized using techniques such as UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), and dynamic light scattering (DLS), confirming their stability, morphology, and surface chemistry. SEM and DLS studies have confirmed the particle size to be approximately 66 nm, XRD confirmed the crystalline structure and FTIR confirmed the capping of gum acacia over the selenium surface. GA-SeNP was screened for the anions and cations in aqueous solution which has shown selective detection towards Ag+ ions with a detection limit in the nanomolar range. The limit of detection and quantification for Ag+ was 0.127 ppm and 0.387 ppm, respectively. SeNP were deposited on a paper strip and silver metal ion detection was performed, showing a quick colour change of the paper strip within seconds from orange to black with a single drop of minimum 2.8 ppm of Ag+ metal. Thus GA-SeNP can be used as an efficient nanoprobe for selective, sensitive, real-time quick analysis and detection of an impermissible limit (>1 mgL−1 i.e. 1 ppm) of silver metal ions in our food, water and cosmetic samples.