A Dihomooxacalix[4]arene-gold nanohybrid based colorimetric sensor for sensitive and selective detection of iodide

Bidentate ureido-dihomooxacalix4]arene based supramolecular hosts (n-propyl 1 and tert-butyl 2) were processed into organic nanoparticles via a bottom up approach in which a single step of re-precipitation was employed. These organic nanoparticles were then coupled with gold nanoparticles on the surface, resulting in an organic – inorganic hybrid framework (n-propyl H1 and tert-butyl H2). Photophysical studies of the organic nanoparticles and of the hybrid material were performed. The size and morphology were determined by TEM and DLS analysis. Moreover, the prepared hybrid frameworks were screened against various anions using UV-Visible absorption and fluorescence spectrophotometry. H1 exhibited ratiometric response towards iodide ion in aqueous medium, and colour change of the solution from pink to light blue was observed. This hybrid material selectively and sensitively detected iodide ion with detection limit of 8.3 nM and with almost no interference from other anions. H1 sensor ability was also tested with artificial and real urine samples. H2 showed different responses and no selectivity to any anion.