Abstract
Stable water-soluble copper sulfide(Cu2S) quantum dots(QDs) with near-infrared emission were synthesized using N-acetyl-L-cysteine(NAC) as a modifier in aqueous solution and nitrogen atmosphere at room temperature. The product was characterized by TEM, XRD, XPS, FT-IR, FL and UV-VIS spectrometers. Effects of preparation conditions such as pH values, the molar ratio of reactants, temperature, and metal ions on the fluorescence properties of Cu2S QDs were discussed. Under optimal conditions, the prepared Cu2S QDs with average diameter about 2–5 nm show a near-infrared emission at 770 nm with the excitation wavelength of 466 nm, and have a good detection sensitivity for ions of Hg2+, Ag+ and Au3+, based on the characteristic of fluorescence quenching. The fluorescence quenching mechanism was proposed via electron transfer with cation exchange, which based on the theory of Hard-Soft-Acid-Base (HSAB) and Ksp value of metal–sulfide.
Highlights
Quantum dots(QDs) have been extensively applied in electronic devices[1] and solar cell[2], in the recent years, many researchers committed to synthesize QDs with properties of water-solubility, narrow emission spectra and high fluorescence intensity and low toxicity, served as biomarkers[3] in biology and medicine and a fluorescent probe to detect heavy metal in analysis[4, 5]
From the transmission electron microscopy (TEM) images Fig. 1(b and c), it is obvious that the particles were well mono-dispersed, featuring spherical shape with the size ranging from 2 nm to 5 nm
localized surface plasmon resonance (LSPR) in the NIR absorption band was not observed in our experiments further indicates that the prepared Cu2−xS QDs is Cu2S28
Summary
Quantum dots(QDs) have been extensively applied in electronic devices[1] and solar cell[2], in the recent years, many researchers committed to synthesize QDs with properties of water-solubility, narrow emission spectra and high fluorescence intensity and low toxicity, served as biomarkers[3] in biology and medicine and a fluorescent probe to detect heavy metal in analysis[4, 5]. From intensive reviews with available resources, there has been no report focusing on both the synthesis and the determination of heavy metal ions by the near-infrared emission fluorescent Cu2S QDs. In this work, stable water-soluble Cu2S QDs with NIR emission were firstly synthesized in aqueous solution at room temperature with NAC as a modifier. Based on the characteristic of fluorescence quenching of NAC capped Cu2S QDs by the heavy metal ions, detection mechanisms are discussed
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