Exploring a FRET-driven ratiometric probe based on perovskite quantum dots and a rhodamine derivative for Cu²⁺...

Based on the FRET mechanism, a fluorescent probe was designed and synthesized for detecting Cu²⁺ in environmental water samples. This nanoprobe was constructed with perovskite quantum dots and a synthetic rhodamine derivative (RBH), which are combined through electrostatic interactions. In the presence of Cu²⁺, RBH undergoes a coordination reaction with Cu²⁺ ions, causing RBH to exhibit an absorption peak at around 550 nm and a fluorescence emission peak at 580 nm. The absorption spectrum of RBH can overlap with the fluorescence emission spectrum of CsPbBr₃@SiO₂ at around 524 nm, triggering the FRET process, in which energy is transferred from CsPbBr₃ to RBH. As the Cu²⁺ concentration increases, the fluorescence intensity for CsPbBr₃ continuously decreases, while that of RBH continuously increases. The emission intensity ratio of RBH and CsPbBr₃ shows an excellent linear relationship with the Cu²⁺ concentration in the range of 3.5-23.5 μM. The relationship is expressed as I₅₈₀/I₅₂₄ = 0.0428 + 0.0038 C_Cu²⁺ (R² = 0.9904), with a limit of detection of 1.26 μM. This nanoprobe can act as an efficient nanosensing matrix for the detection of Cu²⁺ in environmental water samples.