A New Rhodamine-based Fluorescent Probe for the Discrimination of Fe3+from Fe2+

Dopamine Functionalized S,N Co-doped Carbon Dots as a Fluorescent Sensor for the Selective Detection of Fe3+ and Fe2+ in Water

In current work, novel functionalized carbon dots have been designed and synthesized by covalently linking dopamine to the surface of S,N co-doped carbon dots (DA-S,N-CDs) for the selective detection of Fe³⁺ and Fe²⁺ in water. The as-synthesized DA-S,N-CDs emit blue fluorescence peaked at 470 nm and exhibit excitation-dependent tunable emissions. The tolerance towards pH, salt, and UV irradiation of synthesized carbon dots reveals excellent stability. Upon exposure to Fe³⁺ or Fe²⁺, the fluorescence of DA-S,N-CDs was selectively quenched, while other competitive cations did not change significantly. Under the optimal experimental conditions, the fluorescence intensity of DA-S,N-CDs showed a good linear relationship with the concentrations of Fe³⁺ and Fe²⁺ (5 - 200 μM for Fe³⁺ and 5 - 300 μM for Fe²⁺), and the limit of detection was 2.86 and 2.06 μM, respectively. Furthermore, considering the excellent stability and anti-interference, DA-S,N-CDs have been successfully used for the detection of Fe³⁺ and Fe²⁺ in environmental water.

A Highly Selective "Turn-on" Fluorescent Probe for Detection of Fe3+ in Cells

A new "turn-on" fluorescent probe Py based on rhodamine and piperonaldehyde was designed and synthesized for detecting Fe³⁺ in cells. The free probe Py was non-fluorescent. While only upon addition of Fe³⁺, the significant increase of the fluorescence and color were observed which could be visible directly by "naked-eye". The probe Py shows high selectivity and sensitivity for Fe³⁺ over other common metal ions in EtOH-H₂O (3/2, v/v) mixed solution. The association constant and the detection limit were calculated to be 4.81 × 10⁴ M^-1 and 1.18 × 10^-8 mol/L respectively. The introduction of piperonaldehyde unit could increase probe rigidity which could enhance its optical properties. Meanwhile, the binding mode between Py and Fe³⁺ was found to be a 1:1 complex formation. The density functional theory (DFT) calculations were performed which would further confirm the recognition mechanism between probe Py and Fe³⁺. In addition, the probe has been proved to be reversible for detecting Fe³⁺. Moreover, the probe Py was used to detect Fe³⁺ in cells successfully.