Dual-emitting quantum dot/carbon nanodot-based nanoprobe for selective and sensitive detection of Fe³⁺ in cells

A novel dual-emitting fluorescence probe is developed for rapid and ultrasensitive detection of Fe³⁺. The nanoprobe is prepared by coating CdSe semiconductor quantum dots (SQDs) onto the surface of carbon nanodot (CND) doped TiO₂ microspheres. The as-prepared nanoprobe exhibits the corresponding dual emissions at 436 and 596 nm for CNDs and CdSe, respectively, under a single excitation wavelength. The blue fluorescence of the CNDs is insensitive to Fe³⁺, whereas the orange emission of the CdSe SQDs is functionalized to be selectively quenched by Fe³⁺. The intensity ratio of I₄₃₆/I₅₉₆ shows a good linear relationship with the concentration of Fe³⁺ in the range of 10^-9 to 10^-5 M. The nanoprobe provides an effective platform for the reliable detection of Fe³⁺ with a detection limit as low as 10 nM. Besides, this ratiometric nanosensor exhibits good selectivity for Fe³⁺ over other metal ions. The results reveal that the nanoprobe could provide a sensitive sensor for rapid detection of Fe³⁺ with high selectivity and sensitivity. Moreover, 293T cells are used as models to achieve a potential application as a probe for monitoring Fe³⁺ in cells. Thus, these dual-emitting nanoprobes could work as an alternative to conventional fluorescence probes for biolabeling, sensing and other applications.