Visible colorimetric sensing of cysteine based on Au nanoparticle modified ZIF-67

Abstract One gold nanoparticles (NPs) modified zeolitic imidazolate framework material was prepared from cobalt(II) oxide (Au@ZIF-67). The morphology, elemental composition and colorimetric property of it was characterized by UV–Vis spectrophotometer, field-emission scanning electron microscope, transmission electron microscope and energy-dispersive spectroscopy. In presence of 20 amino acids making up proteins, the feature absorbance of Au@ZIF-67 solution at 592 nm decreased accordingly only in presence of cysteine (Cys) and kept almost no change whenever added other 19 amino along or mixed together. Therefore, either naked eye and visible spectrometric methods were proposed for Cys detection with detection limits of 0.5 µM and 0.1 µM, respectively. The distinguished color change, short reaction time, high specificity and sensitivity made Au@ZIF-67 a promising visible colorimetric probe for Cys in water. Moreover, the potential mechanism was studied. The result indicated that Au NPs played as a key role. Graphic abstract