One-step synthesis of highly fluorescent carbon dots as fluorescence sensors for the parallel detection of cadmium and mercury ions

Abstract

Cadmium (Cd2+) and mercury ions (Hg2+) are essential for the quality control of food samples because of their serious toxicity to human health, but the effective and simple strategy for their parallel detection remains challenging. In this paper, a rapid and simple parallel detection method for Cd2+ and Hg2+ was developed using carbon dots (CDs) as fluorescent sensors. A one-step hydrothermal method with a single precursor l-arginine as both the carbon and nitrogen sources was employed to prepare nitrogen-doped CDs (N-CDs). N-CDs exhibited a uniform particle size and excitation-independent fluorescence emission. The maximum emission wavelength of N-CDs was observed at 354 nm with the excitation wavelength at 295 nm. The quantum yield of N-CDs reached as high as 71.6% in water. By using sodium diphosphate and phytic acid as masking agents, the fluorescent sensor can be quenched by Cd2+ and Hg2+ in the linear range of 0–26.8 μM and 0–49.9 μM within 5 min. Other common ions in farm products showed no significant effect on the fluorescence intensity of the sensing system. The results demonstrated that the sensing system had good selectivity and sensitivity for Cd2+ and Hg2+. The detection limits for Cd2+ and Hg2+ were 0.20 and 0.188 μM, respectively. In addition, the fluorescent sensor had been successfully applied for the detection of Cd2+ and Hg2+ in fruits and vegetables, and the recoveries were 86.44–109.40% and 86.62–115.32%, respectively. The proposed fluorescent sensor provides a rapid, simple, and sensitive detection method for Cd2+ and Hg2+ in food samples and thus a novel quantitative detection method for heavy metal ions in foods.

Realizing High Performance Tunable Sensing Mode and Selectivity of Metal Ions Based on Carbon Dot

“…While, the peaks associated around 1416 cm −1 , 1118 cm −1 and 1010 cm −1 are typical for stretching vibrations of C−O bond in carboxylic group, C−O−C bond and C−N stretching vibration respectively. Moreover, the peak position at 618 cm −1 , indicates the presence of out of plane vibration of C−H group as reported in the previous literature [32,33] . However, it is observed that the peaks are more intense in case of CD2 than its counterpart CD1.…”

Metal Ion Sensing with Phenylenediamine Quantum Dots in Blood Serum

“…This phenomenon may be attributed to the chelating effect between the surface functional groups of carbon dots and metal ions. Based on IR spectroscopy, chelate complexes can be presumably formed with −NH/NH 2 , −CO, and −OH groups, where nitrogen and oxygen atoms can donate lone pairs to the unoccupied orbitals of metal ions . Furthermore, a detailed investigation of the absorption spectra suggests that for the Co 2+ ion, an additional quenching mechanism should be considered, namely, the inner filter effect (IFE), stemming from a partial overlap between the Co 2+ absorption spectrum and the CD’s emission spectrum at 530 nm. , …”

“…49 Furthermore, a detailed investigation of the absorption spectra suggests that for the Co 2+ ion, an additional quenching mechanism should be considered, namely, the inner filter effect (IFE), stemming from a partial overlap between the Co 2+ absorption spectrum and the CD's emission spectrum at 530 nm. 49,50 The absorption spectra were analyzed in various solvents, including protic solvents such as water and EtOH (ethanol) and the aprotic solvent DMSO (dimethyl sulfoxide) (Figure S5). Across this solvent series, the band gap slightly decreased, which might indicate the formation of hydrogen bonds between the solvent molecules and functional groups on the CDs' surface.…”

“…Based on IR spectroscopy, chelate complexes can be presumably formed with −NH/NH 2 , −CO, and −OH groups, where nitrogen and oxygen atoms can donate lone pairs to the unoccupied orbitals of metal ions. 49 Furthermore, a detailed investigation of the absorption spectra suggests that for the Co 2+ ion, an additional quenching mechanism should be considered, namely, the inner filter effect (IFE), stemming from a partial overlap between the Co 2+ absorption spectrum and the CD's emission spectrum at 530 nm. 49,50 The absorption spectra were analyzed in various solvents, including protic solvents such as water and EtOH (ethanol) and the aprotic solvent DMSO (dimethyl sulfoxide) (Figure S5).…”

Recent advances in fluorescent materials for mercury(ii) ion detection

“…Since uorescent carbon dots (CDs) have advantages such as low toxicity, good biological compatibility, good water solubility, and high photo-stability, their application value in heavy metal detection has naturally received widespread attention. [51][52][53][54] Functionalized CDs, especially those with surfaces rich in carboxyl, sulydryl, amino groups and so on, are easily combined with heavy metals differently, usually resulting in non-uorescent complexes, and the uorescence quenching mechanism is mainly involved in static quenching. Wu et al 55 had synthesized nitrogen-doped carbon quantum dots (N-CQDs) by a microwave hydrothermal method using citric acid and urea as sources (Fig.…”