Silicon-hybrid carbon dots derived from rice husk: promising fluorescent probes for trivalent rare earth element ions in aqueous media

Abstract

Silicon-hybrid carbon dots (Si–CDs) was synthesized using rice husk as a raw material via a carbonization and acid-cutting method. The as-prepared Si–CDs could be well dispersed in water and exhibits unique blue photoluminescence emission. Furthermore, the Si–CDs notably distinguished between four groups of trivalent rare earth elements ions (REEs). The fluorescence mechanisms behind this were likely due to not only the different fluorescence quenching effects of the REEs, but also that the Si–CDs could transfer the absorbed energy to Tb³⁺, Eu³⁺ and Dy³⁺ ions to enhance their characteristic fluorescence emission intensity. The fluorescence intensity ratio (F₅₄₆/F_Si–CD) exhibited a good linear relationship in the Tb³⁺ concentration range from 1 to 12 μM with a detection limit of about 3.24 nM, and performed satisfactorily in real water samples. In the meantime, a linear relationship was also achieved at wavelengths of 616 nm or 575 nm, correlated with the fluorescence intensity and concentrations of Eu³⁺ or Dy³⁺ in the ranges of 1–16 μM or 4–30 μM, and the detection limit achieved was 0.15 μM or 2.43 μM, respectively. Therefore, the as-prepared Si–CDs could be a potential material for the qualitative and quantitative fluorescent probing of REEs.