Abstract
Copper nanoclusters (Cu NCs) are generally formed by several to dozens of atoms. Because of wide range of raw materials and cheap prices, Cu NCs have attracted scientists’ special attention. However, Cu NCs tend to undergo oxidation easily. Thus, there is a dire need to develop a synthetic protocol for preparing fluorescent Cu NCs with high QY and better stability. Herein, we report a one-step method for preparing stable blue-green fluorescent copper nanoclusters using glutathione (GSH) as both a reducing agent and a stabilizing agent. High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrospray ionization mass spectrometer (ESI-MS) were used to characterize the resulting Cu NCs. The as-prepared Cu NCs@GSH possess an ultrasmall size (2.3 ± 0.4 nm), blue-green fluorescence with decent quantum yield (6.2%) and good stability. MTT results clearly suggest that the Cu NCs@GSH are biocompatible. After incubated with EB-labeled HEK293T cells, the Cu NCs mainly accumulated in nuclei of the cells, suggesting that the as-prepared Cu NCs could potentially be used as the fluorescent probe for applications in cellular imaging.
Highlights
Due to their unique physicochemical properties, metal nanoclusters (M NCs) possess promising applications in the field of catalysis [1,2,3], sensors [4,5,6,7], photonics [8,9] and bioimaging [10,11,12,13]
Fluorescent gold and silver nanoclusters were widely explored while copper nanoclusters (Cu NCs) are much less explored mainly because of the difficulty in obtaining ultra-small size Cu NCs with good stability [2,21,22,23]
Chemical reduction and the ligand etching method are generally used for the preparation of Cu NCs [23,24,25,26,27], but they suffer from obvious drawbacks including complicated and time-consuming process, low quantum yield (QY) and poor stability
Summary
Due to their unique physicochemical properties, metal nanoclusters (M NCs) possess promising applications in the field of catalysis [1,2,3], sensors [4,5,6,7], photonics [8,9] and bioimaging [10,11,12,13]. Chemical reduction and the ligand etching method are generally used for the preparation of Cu NCs [23,24,25,26,27], but they suffer from obvious drawbacks including complicated and time-consuming process, low quantum yield (QY) and poor stability. L.Y. Lin used glutathione-capped CuNCs (with QY 1.3%) to detect Zn2+ basing on the aggregation-induced emission enhancement of GSH-capped Cu NCs [30]. Lin used glutathione-capped CuNCs (with QY 1.3%) to detect Zn2+ basing on the aggregation-induced emission enhancement of GSH-capped Cu NCs [30] Both methods used in these literature synthesized CuNCs at room temperature with short-time heating. The effect of various synthetic parameters including the concentration of GSH, NaOH, reaction temperature and the reaction time on the fluorescence and stability of the Cu NCs were examined as optimization. The as-synthesized Cu NCs exhibited high QY (6.2%) and excellent stability (ion-stability, antioxidation stability, photostability and time-stability) and were successfully used for the imaging of HEK293T cells
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