Preparation Of Imprinting Polymers On The Surface Of CdTe Quantum Dots And Their Application For Detecting4-aminophenol In Water

Quantum dots （QDs） are a kind of semiconductor nanocrystals, which have uniqueand attractive fluorescence properties, such as broad excitation spectra, narrowemission spectra, rigorous quantum size effect, excellent photostability，long lifetimeof fluorescence, good biocompatibility and so on. Based on their unique opticalproperties and high sensitivity, they can be used as fluorescence probes and showadvantages in the areas of biological markers and molecules detection and so on. Butthe surface of QDs is generally susceptible to external environment and QDs can notrecognize specific substances, so it is essential to endow the QDs surface with aprotecting shell and improve the selectivity of QDs. Silica has became the mostpopular material for surface protection of QDs. In order to improve the selectivity ofQDs, a promising way is to cap QDs by the molecularly imprinted polymers （MIPs）.The process is to use QDs as carrier materials, preparing the surface molecularlyimprinted polymers on QDs. Such imprinted polymers show high affinities for thetemplate molecules which can make the fluorescence intensity increased or decreased.The particular specific substance would be detected by monitoring the fluorescenceintensity through the above method.In this research paper, silanated CdTe QDs （CdTe@Si0₂QDs） in water phase weresynthesized through "one pot” method which coated silica shells outside of the CdTeQDs. Subsequently, the surface molecularly imprinted polymers on CdTe@Si0₂QDs（CdTe@Si0₂@MIPs QDs） were synthesized by using4-aminophenol （PAP） astemplate molecules and CdTe@Si0₂QDs as carrier materials. Then CdTe@Si0₂@MIPs QDs were further employed as fluorescence probes. The detailsof this research could be categorized as follows:1.The CdTe@Si0₂QDs were synthesized by “one pot” method in water phaseusing3-mercaptopropionic acid （MPA） as stabilizer. The as-prepared CdTe@Si0₂QDs showed symmetry emission spectra with full width at half maximum（FWHM）about53nm and high quantum yield （39%）. The size of the CdTe@Si〇2QDs wassmall （about11nm） with good dispersion.2.The preparation of CdTe@Si0₂@MIPs QDs was designed as follows: using theas-prepared CdTe@Si0₂QDs as carrier materials, PAP as template molecules,3-aminopropytriethoxysilane （APTES） as functional monomers, tetraethylortho-silicate （TEOS） as the crosslink agents,6.25%aqueous ammonia as catalyst. Afterremoval of the template molecules by ultrasonic and shaking methods,CdTe@Si0₂@MIPs QDs was obtained. The as-prepared CdTe@Si0₂@MIPs QDswas used as fluorescence probes for the determination of aminophenol. Theinteractions between the CdTe@Si0₂@MIPs QDs and PAP were investigated and theresults showed that CdTe@Si0₂@MIPs QDs could identify PAP selectively. PAPcould quench the fluorescence intensity of the CdTe@Si0₂@MIPs QDs. Based on theabove research, a simple, rapid and highly sensitive method for PAP determination intap water and lake water was proposed. The factors affecting the preparation ofpolymers were studied, such as template molecules concentration, the molar ratio oftemplate molecules to functional monomers, the molar ratio of functional monomersto crosslink agents, solvent and so on. The effects of pH value, concentration ofCdTe@Si0₂@MIPs QDs, interfering components on the adsorption properties werestudied too. The mechanism of the reaction was also discussed. Based on the aboveresearch, a practical method for detecting PAP was set up by usingCdTe@Si0₂@MIPs QDs as fluorescence probe. Under the optimized conditions, the quenched intensity of the fluorescence versus PAP concentration from0.05to50\xMgave a linear response with an excellent correlation coefficient of0.9988，and thelimit of detection （3a/K） was0.O₂(aM. The precision for three replicate detections of7.5(aM PAP in tap water sample and lake water sample were1.7%and3.7%（relative standard deviation）, respectively and the recovery of PAP in samples wereranged from98%to103%and97%to1O₂%, respectively.