RESUMEN
Nitrogen and sulfur codoped carbon dots (NSCDs) were synthesized via a one-pot hydrothermal method, and citric acid, ethylenediamine, and methyl blue were used as precursors. The obtained NSCDs were spherical with an average size of 1.86 nm. The fluorescence emission spectra of the NSCDs were excitation independent and emitted blue fluorescence at 440 nm with an excitation wavelength at 350 nm. The quantum yield of the NSCDs was calculated to be 68.0%. The NSCDs could be constructed as fluorescent probes for highly selective and sensitive sensing mercuric (Hg2+) and hypochlorite (ClO-) ions. As the addition of Hg2+ or ClO- ions to the NSCDs, the fluorescence intensity was effectively quenched due to dynamic quenching. Under the optimal conditions, the linear response of the fluorescence intensity ranged from 0.7 µM to 15 µM with a detection limit of 0.54 µM and from 0.3 µM to 5.0 µM with a limit of detection of 0.29 µM for Hg2+ and ClO- ions, respectively. Finally, the proposed method was successfully used for quantifying Hg2+ and ClO- ions in spiked tap water samples.
RESUMEN
A simple approach to fabricate a highly selective and sensitive dimethoate probe was developed based on Rhodamine B (RB)-functionalized gold nanoparticles (AuNPs). The quenching of RB fluorescence in the presence of AuNPs in the solution, mediated by fluorescence resonance energy transfer, was observed. In the presence of dimethoate, the fluorescence intensity of the RB-AuNP solution is gradually recovered when dimethoate molecules displace RB molecules on the surface of the AuNPs, which significantly increased the fluorescence intensity of RB. Fluorescence is proportional to the dimethoate concentration in the range of 0.005-1.0â¯ppm (R2â¯=â¯0.989), and the LOD was 0.004â¯ppm. The recoveries of dimethoate in water and fruit samples were 86-116% with a good RSD (<â¯9.3%). Because of its high sensitivity, excellent selectivity, and convenient fabrication process, this method is a promising candidate for dimethoate screening.