|Semiconductor nanoparticles (NPs) have attracted great interest in both fundamental research and technical applications including biological labeling, LED displays, optosensing, and solar cells, due to their unique properties such as size-dependent tunable emission, narrow emission bandwidth, broad excitation, strong absorption abilities, and good photo-stability. A novel homogeneous optosensing method was put forth for simultaneous sensing of fluoroquinolone (FQ) derivatives in water utilizing the upconversion fluorescence resonance energy transfer (FRET) process. Initially, a monodisperse, size-tunable β-NaLuF4:Yb, Er, Gd upconversion nanophosphors (UCPs) were synthesized. It was then covalently linked with carboxylic acid (COOH-) group directly on the surface of the nanoparticles, which was used as a donor after conjugation with the high cross-reactivity monoclonal antibody (Mab, C2F3C2) against FQs. The corresponding antigens (ciprofloxacin-BSA) labeled gold nanoparticles (AuNPs) acted as an acceptor. Under optimized conditions, the limit of detection (LOD) was 0.29 ng/mL (calculated by the mean of zero calibrators, 3 SD).
We also developed a simple optosensing method for various biomolecules including clenbuterol, melamine, and uric acid was developed using molecularly imprinted polymer-capped CdTe quantum dots (MIP-CdTe QDs. A convenient optical detection for uric acid was performed using the fluorescence quenching of CdTe nanoparticles by H2O2 which was generated from the enzymatic reaction of uric acid. Excellent selectivity and high sensitivity of MIP-CdTe QDs toward the target molecules were observed based on the fluorescence quenching of QDs. The feasibility of the developed method in real samples was successfully evaluated through the analysis in real samples such as milk, liver, and human urine samples with satisfactory recoveries of 92-97%.