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 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.