A nanocomposite probe of graphene quantum dots and magnetite nanoparticles embedded in a selective polymer for the enrichment and detection of ceftazidime.

Graphene quantum dots and magnetite nanoparticles were embedded in molecularly imprinted polymer (GQDs@Fe3O4/MIP) to develop a magnetic nanocomposite fluorescent probe that could enrich and detect trace ceftazidime in milk in conjunction with an optosensor. Graphene quantum dots enhanced the sensitivity of the optosensor and the specificity of the molecularly imprinted polymer reinforced the selectivity of the nanocomposite probe. The incorporated magnetite nanoparticles increased enrichment of the target analyte so that a smaller volume of detecting solution could be used. The developed probe was characterized and the preparation procedure and detection conditions were optimized. In the optimum conditions, linearity was in the range of 0.10-10.0 µg L-1 and the limit of detection was 0.05 µg L-1. The developed system was utilized to detect ceftazidime in milk samples. Recoveries were in the range of 90.7-99.2% with RSD below 6% and the obtained results agreed well those obtained with chromatographic technique. However, the developed optosensor exhibited better sensitivity, was faster and easier to operate and can be modified for the enrichment and detection of other target analytes in various sample matrices.

A nanocomposite probe of polydopamine/molecularly imprinted polymer/quantum dots for trace sarafloxacin detection in chicken meat.

A nanooptosensor based on the fluorescence quenching of a composite probe was fabricated for the detection of sarafloxacin. The components of the nanocomposite fluorescent probe were a high affinity material of polydopamine polymer (PDA), a selective material of molecularly imprinted polymer (MIP), and optically sensitive quantum dots (QDs). The developed nanocomposite fluorescent probe exhibited excellent selectivity and sensitivity for sarafloxacin. The molecularly imprinted polymer had an imprinting factor (IF) of 8.18 and produced a probe that quenched fluorescence more effectively than a non-imprinted polymer (NIP) probe. The emission intensity of the MIP probe was linearly quenched by sarafloxacin over a range of 0.10 to 15.0 µg L-1 with a determination coefficient (R2) of 0.9966. The developed nanooptosensor had a limit of detection of 0.05 µg L-1. The optosensor detected sarafloxacin in chicken meat samples with recoveries ranging from 82.8 to 99.1% with an RSD below 3%. The found concentrations in spiked samples were compared well with recoveries obtained by HPLC method of detection. This developed nanooptosensor is simple to operate and cost-effective and the analytical procedure is rapid. Graphical abstract.