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 polypyrrole doped with fluorescent CdTe quantum dots and incorporated into molecularly imprinted silica for fluorometric determination of ampicillin.

A fluorometric method is described for the detection of ampicillin. A polypyrrole containing fluorescent CdTe quantum dots was incorporated into a silica-based molecularly imprinted polymer. The composite MIP displays good fluorescence (with excitation/emission maxima at 355/548 nm), and high selectivity and affinity for ampicillin due to the use of polypyrrole. Ampicillin is found to quench the fluorescence of composite much more strongly than the emission of a non-imprinted polymer. The imprinting factor of 7.5 implies that the nanocomposite probe contains specific binding sites. The MIP probe has two linear response ranges, one from 0.10 to 25 µg L-1 of ampicillin, and one from 25 to 100 µg L-1. The limit of detection is 0.05 µg L-1. The method was applied to the determination of ampicillin in (spiked) milk and meat samples and gave recoveries between 81.7 and 98.7%. The results agreed well with HPLC techniques. Graphical abstract Schematic presentation of nanocomposite fluorescence probe of polypyrrole and quantum dots incorporated in a molecularly imprinted polymer. Integrating of QDs, high specificity of MIPs and high affinity of polypyrrole, the method exhibited highly sensitive and selective for ampicillin detection.

A hybrid molecularly imprinted polymer coated quantum dot nanocomposite optosensor for highly sensitive and selective determination of salbutamol in animal feeds and meat samples.

A hybrid molecularly imprinted polymer (MIP)-coated quantum dot (QD) nanocomposite was synthesized and applied as a fluorescence probe for the highly sensitive and selective determination of salbutamol. The hybrid MIP-coated QD nanocomposite was synthesized via a copolymerization process in the presence of thioglycolic acid capped CdTe QDs with salbutamol as a template, 3-aminopropyltriethoxysilane as the functional monomer, and tetraethyl orthosilicate as a cross-linker. The optimum molar ratio of template, monomer, and cross-linker was 1:6:20. The fluorescence intensity of the hybrid MIP-coated QDs was efficiently quenched after salbutamol rebound to the recognition sites, as a result of charge transfer from QDs to salbutamol. The synthesized hybrid MIP-coated QD nanocomposite showed high sensitivity and good selectivity toward salbutamol. Under the optimal recognition conditions, the fluorescence intensity was quenched linearly with increasing concentration of salbutamol in the range from 0.10 to 25.0 µg L-1, with a detection limit of 0.034 µg L-1. The hybrid optosensor developed was successfully applied in the determination of salbutamol in animal feeds and meat samples. Satisfactory recoveries were obtained in the range from 85% to 98%, with a standard deviation of less than 8%. Furthermore, the accuracy of the hybrid MIP-coated QD nanocomposite was investigated by comparison with a conventional high-performance liquid chromatography method, with the results obtained with two methods agreeing well with each other. The advantages of this sensing method are simplicity, rapidity, cost-effectiveness, high sensitivity, and good selectivity. Graphical Abstract The synthesis of hybrid MIP-coated QDs nanocomposite.