Fluorescence ‘turn‐off–on’ assays for neomycin sulphate and K⁺ ions with orange‐red fluorescent molybdenum nanoclusters

Fluorescent metal nanoclusters (MNCs) have found extensive application in recognizing molecular species. Here, orange‐red fluorescent Arg– A. paniculata –MoNCs were synthesized using Andrographis paniculata leaf extract, arginine as a ligand, and MoCl 5 as a metal precursor. The Arg– A. paniculata –MoNCs complex exhibited a quantum yield (QY) of 16.91% and excitation/emission wavelengths of 400/665 nm. The synthesized Arg– A. paniculata –MoNCs successfully acted as a probe for assaying neomycin sulphate (NS) via fluorescence turn‐off and K + ions via fluorescence turn‐on mechanisms, respectively. Moreover, the developed probe was effectively used to develop a cellulose paper strip‐based sensor for detection of NS and K + ions. Arg– A. paniculata –MoNCs demonstrated great potential for sensing NS and K + ions, with concentration ranges of 0.1–80 and 0.25–110 μM for NS and K + ions, respectively. The as‐synthesized Arg– A. paniculata –MoNCs efficiently detected NS and K + ions in food and biofluid samples, respectively.