The Analytical Application And Construction Of Imprinted Hybird Membrane And Dual Fluorescence Ratio Sensor Based On Mn-Doped ZnS Quantum Dots

Quantum dots (QDs) have unique optical properties, high luminescenceefficiency, size-tunable emission wavelength, symmetric emission peak and soon, which make it becoming a superior fluorescence material. Quantum dotsas chemical sensors have been used to detect ions, biological molecules andso on. Molecularly imprinted polymers (MIP) can specific identification ofthe template molecules. Quantum dot capped by molecularly imprintedpolymers can combine the excellent optical properties of quantum dots andexcellent selectivity of molecularly imprinted polymers, and improve thesensitivity and selectivity of the sensor. Organic-inorganic hybrid membranehas many advantages, such as low cost, the film is good, high stability and soon, and to some extent, to meet the demanding requirements of the sensor onthe membrane, thus becoming the new hot spot of the membrane of scientificresearch. Compared to the pure liquid phase analysis, the hybrid membranesanalysis has easy regeneration, reversible, and high sensitivity. Notably, mostof the traditional fluorescence probes use single fluorescence intensity as aresponse signal. However, the analysis of single fluorescent signal isinterfered by concentration of substrate, the external environment, instrumentconditions change and so on. The ratiometric fluorescence sensing caneffectively eliminate these uncertain environmental effects by using anotherfluorescence signal as a reference.This thesis includes the main contents as following:(1) We prepared ZnS: Mn QDs in water, and studed the optical propertiesof ZnS: Mn QDs. Then, the functional monomer3-aminopropyltriethoxysilane (APTES), cross-linking agent tetraethoxysilane (TEOS), thecatalyst ammonia and the template molecule nitric phenol (4-NP) were mixed,ZnS: Mn QDs would be coated by molecularly imprinted polymers. Inaddition, the structure and morphology of the Quantum dots werecharacterized by Fourier transform infrared spectra (FTIR), field emissionscanning electron microscope (SEM), X-ray powder diffraction (XRD). The optical properties of the Quantum dots ware characterized by UV absorptionspectra and fluorescence spectra.(2) MIP/ZnS:Mn QDs and chitosan were mixed, and hybrid membranewas fabricated onto the quartz surface. A fast, sensitive and selective methodwas established to detect trace4-nitrophenol (4-NP) based on the fluorescencequenching of hybrid membrane by4-NP. In addition, a good linearrelationship between fluorescence response and concentration of4-NP couldbe obtained in the range from1.0to8.0μmol/L, the detection limit was41nmol/L. The hybrid membrane is stable and can be regenerated by immersinginto ethanol. The method was also used in the real water samples, and therecoveries can fall in the range of95.5%~103.0%.(3) We prepared ferulic acid-doped Mn in ZnS composite nanoparticles,to build a rational fluorescent probes. ZnS:Mn QDs was as an "internalstandard", and capped by a layer of silica shell, while ferulic acid would be asthe sensing part in the outermost layer of quantum dots. Because of hydrogenbonding, uric acid can quench the fluorescence of ferulic acid, while thefluorescence of ZnS:Mn QDs would not be quenched, due to the protection ofthe silica shell. The ratio of the quantum dot fluorescent probes based on thereference materials, the internal standard with automatic calibration functioncan reduce impaction of devices, sensors and analyte interference of externalfactors on the determination result, increase the accuracy of the detectionmethod.