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 nanocomposite optosensor containing carboxylic functionalized multiwall carbon nanotubes and quantum dots incorporated into a molecularly imprinted polymer for highly selective and sensitive detection of ciprofloxacin.

A nanocomposite optosensor consisting of carboxylic acid functionalized multiwall carbon nanotubes and CdTe quantum dots embedded inside a molecularly imprinted polymer (COOH@MWCNT-MIP-QDs) was developed for trace ciprofloxacin detection. The COOH@MWCNT-MIP-QDs were synthesized through a facile sol-gel process using ciprofloxacin as a template molecule, 3-aminopropylethoxysilane as a functional monomer and tetraethoxysilane as a cross-linker at a molar ratio of 1:8:20. The synthesized nanocomposite optosensor had high sensitivity, excellent specificity and high binding affinity to ciprofloxacin. Under optimal conditions, the fluorescence intensity of the optosensor decreased in a linear fashion with the concentration of ciprofloxacin and two linear dynamic ranges were obtained, 0.10-1.0 µg L-1 and 1.0-100.0 µg L-1 with a very low limit of detection of 0.066 µg L-1. The imprinting factors of the two linear range were 17.67 and 4.28, respectively. The developed nanocomposite fluorescence probe was applied towards the determination of ciprofloxacin levels in chicken muscle and milk samples with satisfactory recoveries being obtained in the range of 82.6 to 98.4%. The results were also in good agreement with a HPLC method which indicates that the optosensor can be used as a sensitive, selective and rapid method to detect ciprofloxacin in chicken and milk samples.

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.

Hybrid monolith sorbent of polypyrrole-coated graphene oxide incorporated into a polyvinyl alcohol cryogel for extraction and enrichment of sulfonamides from water samples.

A hybrid monolith sorbent of polypyrrole-coated graphene oxide embedded in polyvinyl alcohol cryogel was prepared and used as an effective solid phase extraction sorbent for the determination of trace sulfonamides. The large surface areas with many adsorption sites of polypyrrole and graphene oxide facilitated the high adsorption of sulfonamides via hydrogen bonding, π-π and hydrophobic interactions. The high porosity of the polyvinyl alcohol cryogel helped to reduce the back pressure that occurs in a conventional packed solid phase extraction cartridge. The effecting parameters on the extraction efficiency including the type of sorbent, the polymerization time, desorption conditions, the sample pH, the sample volume, the sample flow rate, and ionic strength were investigated and optimized. Under the optimum conditions, the developed method provided a wide linear range from 0.20 to 100.0 µg L-1 for sulfadiazine, sulfathiazole and sulfamerazine; and from 0.10 to 100 µg L-1 for sulfamethazine, sulfamonomethoxine and sulfadimethoxine. The limits of detection were 0.20 µg L-1 for sulfadiazine, sulfathiazole and sulfamerazine; and 0.10 µg L-1 for sulfamethazine, sulfamonomethoxine and sulfadimethoxine. The developed hybrid monolith polypyrrole-coated graphene oxide embedded in the polyvinyl alcohol cryogel sorbent provided good recoveries in the range of 85.5-99.0% with RSDs of less than 5.0%. The sorbent offered a good reproducibility, was robust and can be reused at least 10 times. It was successfully applied for the extraction and enrichment of sulfonamides from normal and supplemented water samples.

Ultra trace analysis of small molecule by label-free impedimetric immunosensor using multilayer modified electrode.

A multilayer electrode modified with a self-assembled thiourea monolayer (SATUM) followed by gold nanoparticles (AuNPs), mercaptosuccinic acid (MSA) and antibody was investigated for the detection of ultra trace amount of a small molecule (chloramphenicol) in an impedimetric system. The formation of the antibody-antigen complex at the electrode surface caused the impedance to increase. Under optimum conditions three modified electrodes were compared the SATUM/AuNPs/MSA electrode provided a wide linear range (0.50-10) × 10⁻¹6 M, and a very low determination limit of 1.0 × 10⁻¹6 M. This determination limit was much lower than the SATUM/AuNPs electrode, 1.0 × 10⁻¹5 M, and SATUM electrode, 4.7 × 10⁻¹4 M. The modified electrode provided good selectivity for chloramphenicol detection and can be reused up to 45 times with a relative standard deviation of lower than 4%. When applied to determine chloramphenicol in shrimp samples, the results agreed well with those obtained by the high-performance liquid chromatography coupled with a photo diode array detector (P > 0.05). The developed system can be applied to detect other small molecules using appropriate affinity binding pairs.