Novel blue-emitting gold nanoclusters confined in human hemoglobin, and their use as fluorescent probes for copper(II) and histidine

摘要

We report on the synthesis and characterization of highly fluorescent gold nanoclusters (Au-NCs) from a gold precursor using a single-step chemical reduction in the presence of human adult hemoglobin (Hb). The conformational changes of Hb before and after cluster formation were studied by various spectroscopic techniques. The Au-NCs in Hb display blue fluorescence with a peak centered at 450 nm (photoexcited at 365 nm) and a quantum yield of 2.8 %. The Au-NCs exhibit excellent photostability and long-term stability, and can be applied in the pH range 5-12 even in the presence of high electrolyte concentrations. The Au-NCs in Hb can act as a highly sensitive and selective fluorescent turn-off probe for Cu(II) ion. The observed reversible fluorescence recovery of Hb-AuNCs/Cu(II) aggregates was exploited to develop a selective and sensitive turn-on fluorescence assay for His. Under optimized conditions, the probe gives a fluorescent response that is linear in the 0.1 to 20.0 mu M concentration range of Cu(II), with a limit of detection of 28 nM. The probe for His, in turn, has a linear range in the 1-21 mu M concentration range, and the limit of detection is 0.6 mu M.