Here we report a highly selective biosensor based on ionic liquids-assisted colorimetric sensing. As(III) inhibited gold nanoparticles (AuNPs) aggregation induced by ionic liquids (ILs). Six different ILs were evaluated in this study, namely 1-(3-cyanopropyl)-3-methylimidazolium chloride (CPMI), 1-(3-cyanopropyl)pyridinium chloride (CPP), tetradecyldimethylbenzylammonium chloride (TDDBA), cetylpyridinium chloride monohydrate (CP), 1-butyl-1-methylpyrrolidinium methyl carbonate (BMP) and tributylmethylphosphonium methyl carbonate (TBMP). We discovered that a series of ILs were much more efficient, i.e. up to 40,000 folds, than traditional inorganic electrolytes (e.g. NaCl) in inducing aggregation of AuNPs, however, which was inhibited by As(III). Modelling of two- and three-ways non-covalent interactions amongst ILs, citrate, and metal ions was explored by molecular geometry optimization, and calculation of binding energies using density functional theory (DFT). Inhibition of ILs-induced AuNPs aggregation by arsenite could differentiate it from arsenate and many other ions including cadmium, zinc, sodium, chromate, bromide and iodide. DFT calculation results explain why BMP were selective to arsenite. Repeatability, interference, stability, selectivity, and sensitivity were studied. Detection limits were further lowered by a random DNAzyme substrate. The limit of detection (LOD) of the sensors was 10 ppb. The arsenite sensing was demonstrated using real water samples and validated with ICP-OES.

Highly selective biosensor based on ionic liquids-assisted colorimetric sensing for arsenite

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