The dual-mode fluorescent and colorimetric Ag@R-CDs probe for highly selective detection of Fe³+

To overcome the interference caused by the inner filter effect, this study optimally selected red fluorescence carbon dots as the signal source and constructed a novel dual-mode Ag@Red-CDs nanoprobe for the highly selective detection of Fe³+ using fluorescence and colorimetry. This probe is based on a unique reaction between Fe3+ and silver nanoparticles (AgNPs) that weakens the static quenching effect of AgNPs on R-CDs; at the same time, the depletion of AgNPs induces a change in the absorbance of the system. Under optimal conditions, the probe exhibited a linear fluorescence response in the Fe³+ concentration range of 0.10–25.00 μg/mL and a linear colorimetric response of 0.18–8.00 μg/mL. The detection limits for fluorescence and colorimetry were 0.31 μg/mL and 0.56 μg/mL, respectively. In spiked real samples, the fluorescence method achieved Fe³+ recovery rates of 99.10–102.34%, while the colorimetric method showed recovery rates of 99.83–101.42%. Overall, this research significantly broadened the potential applications of R-CDs-based materials for the quantitative detection of heavy metal ions in water bodies.