Fluorescence chemosensing of water-soluble Ag14 nanoclusters for lysozyme and Hg2+ ions

Employing glutathione (HSG) as a protecting ligand, we have synthesized water-soluble and biocompatible Ag-14(SG)(12) nanoclusters (Ag-14 NCs) of which the composition and structure are determined via high-resolution mass spectrometry, fingerprint spectroscopy and DFT calculations. Natural bond orbital (NBO) analysis on a basis of first-principles theoretical calculations demonstrates the donor-acceptor orbital overlaps and charge-transfer interactions between silver and the ligand HSG. Further, it is interestingly found that the fluorescence of Ag-14 NCs can be largely enhanced at the presence of lysozyme distinguishing from other proteases which we have tested, revealing the feasibility of Ag-14 NCs as chemosensing to identify lysozyme. Also found is that, the fluorescence on-state of the obtained Ag14NCs-Lys can be exclusively switched off at the addition of Hg2+ ions with an ultralow detection limit of similar to 16.2 nM. This interesting finding reveals Ag-14 NCs a versatile chemosensor to identify lysozyme from proteases and to detect mercury ions from various cations. (C) 2017 Elsevier B.V. All rights reserved.