Green synthesis of a fluorescence optical probe for Fe³⁺ based on Barberry derived carbon quantum dots: Deep insight...

A green facile method was developed to synthesize the carbon quantum dots from barberry, a native plant, as a new carbon source. The synthesis strategy is a simple one-step hydrothermal process without requiring hazardous chemical reagents. The spherical structure of b-CDs with an average particle size of 3.3 nm including oxygen and nitrogen functional groups was evaluated by various analyses (FT-IR, DLS, XRD, FE-SEM, TEM, AFM). The synthesized b-CDs with QY of 12.82 % were used as a fluorescence optical probe (λ_ex = 350 nm, λ_em = 450 nm) to measure iron ions as an inorganic pollutant. In the presence of Fe³⁺, the fluorescence intensity of b-CDs decreases due to the interaction between the functional groups on the surface of b-CDs and Fe³⁺. The linear relationship was in the concentration range from 5.00 × 10^-6 to 8.00 × 10^-5 M with LOD of 1.73 × 10^-6 M which was lower than the concentration determined by WHO. AGREE software was utilized to prove the greenness of the reported analytical method. In parallel, the theoretical calculations employing Density Functional Theory (DFT) were used to understand the electronic structure and atomic level insight into the functionalized b-CDs and interaction of Fe³⁺ with the different sites of b-CDs surface. From a thermodynamic point of view, the interaction of Fe³⁺ from the COOH functional group in b-CDs is more favorable than other sites with more negative Gibbs free energy interaction. Overall, producing eco-friendly fluorescence nanomaterials with favorable fluorescence properties, low cost, and sufficient sensitivity like b-CDs seems promising for designing new fluorescence probes.