Fluorometric sensing of hydroxylamine in an aqueous medium utilizing a diphenyl imidazole-based probe

The detection of hydroxylamine in an aqueous medium is challenging due to its very similar chemical reactivity to its nearest competitors such as hydrazine hydrate and primary amines. Moreover, the detection of hydroxylamine at neutral pH adds further complexity to the sensing phenomenon due to its poor reactivity in a neutral aqueous medium. In this work, we have presented a diphenyl imidazole benzaldehyde (DIB) probe which demonstrates the detection of hydroxylamine (HA) in micromolar concentrations with high selectivity in 5% DMSO phosphate buffer solution at pH 7.4 via a fluorescence "turn-on" signal. The interaction of hydroxylamine with the probe has been comprehensively studied by using fluorescence spectroscopy, proton NMR, FTIR, ESI-mass spectrometry and DLS measurements. The experimental results were further corroborated with the DFT studies. These results could pave the way toward the development of molecular indicators for hydroxylamine in chemical and biological platforms.