Synthesis and characterization of La QDs: sensors for anions and H2O2†

The development of sensitive and accurate fluorescence sensors for the detection of anions and reactive oxygen species (ROS, H₂O₂) is essential as they play significant roles in biological and chemical processes. In this work, semiconductor La QDs were synthesized. The synthesized La QDs were determined to be pure with 100% La element using EDS technique. La QDs were observed in both cubic and hexagonal lattice configurations through powder XRD analysis. The morphology of the La QDs was characterized using HRTEM and FESEM data as tiny, spherical, homogenous QDs with a diameter ranging from 2 to 6 nm. The fluorescence characteristics of the synthesized La QDs were examined by studying their sensing properties that increased with an increase in anion concentration and decreased with an increase in [H₂O₂]. The variation in emission intensity at 315 nm and 440.5 nm satisfied the Stern–Volmer equation. The LOD and LOQ of H₂O₂ and anion sensing with La QDs were studied in the μM range. The Langmuir binding plots and FTIR spectra supported the concept that the surface functionalization of La QDs occurred in the presence of anions. With two band gap energies of about 3.26 eV and 4.66 eV, the synthesized La QDs are a mixture of two (binary) semiconductors.