Enhanced sensing of mercuric ions based on dinucleotide-functionalized silver nanoparticles

A very simple one-pot synthesis of nicotinamide adenine dinucleotide (NAD)-functionalized silver nanoparticles in an aqueous solution at room temperature without hazardous reducing agents wherein NADH is employed as the functional molecule for highly selective optical sensing of mercuric ions (Hg²⁺) in an aqueous solution based on an absorption and emission method, with a detection limit of 0.02 nM. NADH was used as the reducing and stabilizing agent for the formation and stabilization of silver nanoparticles, and cetyltrimethylammonium bromide (CTAB) was used as the growth agent for the silver nanoparticles. The NADH-stabilized silver nanoparticles were used as an optical sensor for the detection of mercuric ions. The potential sensing ability of these synthesized silver nanoparticles is utilized to design an absorption and emission-based sensor platform for mercuric ions with high sensitivity and selectivity in the presence of other interfering metal cations, including Pb²⁺, Cd²⁺, Ce²⁺, Cu²⁺, Ni²⁺, Li⁺, Na⁺, K⁺ and Ca²⁺. The facile biomolecule-assisted synthesis of anisotropically structured silver nanoparticles and the direct detection of mercuric ions at the nano-molar concentration level in the presence of other interfering metal ions in water are the main advantages of the present system. The ultrasensitive nature of the sensing platform is ascribed to the NAD-functionalized anisotropic silver nanostructures. The present optical sensor is very simple to prepare, cost effective, and time saving; no external assemblies are attached on the surface of the silver nanoparticles. This method does not require the use of organic co-solvents, enzymatic reactions, light-sensitive dye molecules, lengthy protocols, surface modification of nanoparticles, or sophisticated instrumentation, thereby overcoming most of the limitations of conventional methods.