Aqueous synthesis of functionalized copper sulfide quantum dots as near-infrared luminescent probes for detection of Hg2+, Ag+ and Au3+

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.

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“…The functional groups and the change in the characteristic peaks were determined by the decrease in the transmittance of the peaks (Figure 2). The characteristic peaks for the functional groups of NAC at 2546 cm −1 for the SH group and 1718 cm −1 C=O for carboxyl groups were consistent with the results of other studies [35]. The characteristic peaks in the spectra for the functional groups of SF were Amide I, Amide II and Amide III (e.g., 1237 cm −1 ) and were the same as those for SF NPs, which was in agreement with earlier studies [7].…”

Noninvasive Tracking and Regenerative Capabilities of Transplanted Human Umbilical Cord-Derived Mesenchymal Stem Cells Labeled with I-III-IV Semiconducting Nanocrystals in Liver-Injured Living Mice

“…However, the PL intensities were similar for other metal ions (Supporting Information, Figure S4). The quenching of the PL intensity could be due to aggregate-induced quenching and electron transfer associated with cation exchange . As the surface of NCs is highly sensitive to surface states and the bond dissociation energy of Zn–S (205 kJ/mol) is less than those of Co–S (331.1 kJ/mol) and Ni–S (356 kJ/mol), thus, the exchange of cations could have been thermodynamically favored and alter the photophysical behavior.…”

Highly Photoluminescent and Stable N-Doped Carbon Dots as Nanoprobes for Hg2+ Detection

“…Water pollution by heavy metal ions due to the emission of industrial waste presents a major environmental problem [ 1 , 2 , 3 ]. In particular, the mercury ion (Hg 2+ ) is one of the most prevalent and dangerous pollutants, with the character of easy bioaccumulation and high toxicity, which causes serious health and environment problems, including damage to the nervous system, ecosystem, brain, and heart [ 4 , 5 , 6 , 7 ]. Furthermore, the water soluble Hg 2+ is one of the most common forms in mercury pollution, which is hard to remove once released into the environment or getting into the human body due to its non-biodegradability [ 8 , 9 , 10 ].…”