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A highly sensitive and selective detection of picric acid using fluorescent sulfura??doped graphene quantum dots
摘要： The development of an analytical probe to monitor highly mutagenic picric acid (PA) carries enormous significance for the environment and for health. A novel, simple and rapid fluorescence analytical assay using sulfur-doped graphene quantum dots (SGQDs) was designed for the highly sensitive and selective detection of PA. SGQDs were synthesized via simple pyrolysis of 3-mercaptopropionic acid and citric acid and characterized using advanced analytical techniques. Fluorescence intensity (FI) of SGQDs was markedly quenched by addition of PA, attributed to the inner filter effect and dominating static quenching mechanism between the two, in addition to a significant colour change. The calibration curve of the proposed assay exhibited a favourable linearity between quenched FI and PA concentration over the 0.1–100 μΜ range with a lowest detection limit of 0.093 μΜ and a correlation coefficient of 0.9967. The analytical assay was investigated for detection of trace amounts of PA in pond and rain water samples and showed great potential for practical applications with both acceptable recovery (98.0–100.8%) and relative standard deviation (1.24–4.67%). Analytical performance of the assay in terms of its detection limit, linearity range, and recovery exhibited reasonable superiority over previously reported methods, thereby holding enormous promise as a simple, sensitive, and selective method for detection of PA.
关键词： static quenching,inner filter effect,picric acid,fluorescent probe,sulfur-doped graphene quantum dots
更新于2025-09-16 10:30:52
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Carbon quantum dots (CQDs) modified ZnO/CdS nanoparticles based fluorescence sensor for highly selective and sensitive detection of Fe(III)
摘要： A simple and fast spectrofluorimetric method coupled with carbon quantum dots (CQDs) modified ZnO/CdS nanoparticles was developed for the detection of Ferric iron (Fe(III)). The fluorescence of CQDs/ZnO/CdS NPs was effectively quenched by Fe(III) due to the strong interaction between the CQDs/ZnO/CdS NPs and Fe(III). In addition, the detection limit of Fe(III) was about 1.72 × 10^-7 M. The effect of foreign ions on the fluorescence intensity of CQDs/ZnO/CdS NPs showed that the interference response in detecting of Fe(III) ions was low. Moreover, the quenching of Fe(III) and CQDs/ZnO/CdS NPs was discussed to be a static quenching procedure, which was proved by quenching constant KSV and fluorescence lifetime τ. The study of thermodynamics showed that the values of entropy change (?S) and enthalpy change (?H) were both positive, and the values of free energy (?G) was negative, which implied that the weak interaction of the molecular between CQDs/ZnO/CdS NPs and Fe(III) was hydrophobic force, and the quenching process was endothermic and spontaneous.
关键词： Static quenching,Ferric iron,CQDs/ZnO/CdS NPs,Fluorescence sensor
更新于2025-09-12 10:27:22
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Study of alloyed quantum dots-porphyrazine interaction in solution
摘要： The core-shell quantum dots, namely, CdSxSe1-x/ZnS (QD), and free-base porphyrazine (1) undergoes spontaneous interaction in solution. Steady state fluorescence measurements reveal significant quenching of the photoluminescence of QD in presence of 1. The average value of lifetime of QD (16.10 ns) suffers negligible change in presence of 1 (15.55 ns). The value of bimolecular quenching constant, i.e., kq for QD-1 system (kq = 1.380 × 1011 litre·mol-1·sec-1) determined from time-resolved fluorescence experiment rules out the possibility of diffusion driven process in present work. The mechanism of binding interaction between QD and 1 is established following the evaluation of binding constant value, i.e., K = 12,720 litre·mol-1 for QD-1 system. The results emanating from present work would be very much helpful for employing QD-porphyrazine type system as possible binding unit in energy and/ electron transfer process.
关键词： binding interaction,CdSxSe1-x/ZnS (QD),static quenching,free-base porphyrazine,PL quenching
更新于2025-09-11 14:15:04
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A fluorescence quenching based gene assay for Escherichia coli O157:H7 using graphene quantum dots and gold nanoparticles
摘要： A fluorometric assay is described for highly sensitive quantification of Escherichia coli O157:H7. Reporter oligos were immobilized on graphene quantum dots (GQDs), and quencher oligos were immobilized on gold nanoparticles (AuNPs). Target DNA was co-hybridized with reporter oligos on the GQDs and quencher oligos on AuNPs. This triggers quenching of fluorescence (with excitation/emission peaks at 400 nm/530 nm). On introducing target into the system, fluorescence is quenched by up to 95% by 100 nM concentrations of target oligos having 20 bp. The response to the fliC gene of E. coli O157:H7 increases with the logarithm of the concentration in the range from 0.1 nM to 150 nM. The limit of detection is 1.1 ± 0.6 nM for n = 3. The selectivity and specificity of the assay was confirmed by evaluating the various oligos sequences and PCR product (fliC gene) amplified from genomic DNA of the food samples spiked with E. coli O157:H7.
关键词： Food pathogens,Static quenching,fliC gene,Selectivity,Fluorophore,Quencher,Real samples
更新于2025-09-11 14:15:04