| Nanostructured semiconductor materials with unique optical and electrical properties have attracted a lot of interests in the last two decades. As a direct bandgap II-VI semiconductor, CdS nanoparticles have been paid more attentions for their excellent optical properties. Compared to the conventional organic dyes, CdS nanoparticles appear to be less susceptible to photobleaching with much narrower emission spectra and tunable maximum emission wavelength, which have been successfully used as fluorescent probe for the imaging of biological samples and cells. And the CdS nanoparticles become very sensitive to their local environment, and detections of some inorganic ions, proteins, DNA conformations were thus developed based on this property.On the basis of related literatures, the synthesization of highly luminescent water-soluble CdS nanoparticles was studied. We modified the CdS nanoparticles to be fluorescent probes to detect inorganic ion, DNA and single-base mutations. The main work in this thesis is as follows:(1) Reviews were given firstly on the properties, synthetic methods and applications of CdS nanoparticles.(2) CdS nanoparticles were synthesized by the aqueous solution method. The nanoparticles were of uniformity in size and good dispersancy. CdS nanoparticles were modified with cysteine and cysteamine, respectively. The factors those influencing the CdS nanoparticle fluorescence were tracked and inspected. The interaction mechanism between CdS nanoparticles with cysteine and cysteamine were also discussed. Then characterize the samples. The experimental results showed that CdS nanoparticles were stable and of strong fluorescence intensity in aqueous solution. Furthermore, functionalized CdS nanoparticles with good fluorescence stabilities were obtained under the modification with low concentration of cysteine or cysteamine.(3) A new approach was proposed for the sensitive determination of manganese ions with nanoparticles-modified fluorescence probes. Different influencing factors were studied. Under the optimum conditions, the response is linearly proportional to the concentration of manganese (II) ion in the range from 0.0534 mg/L to 77.6 mg/L. The limit of detection is 0.0168 mg/L for.manganese (II) ion. And it was proved to be a low-cost, simple, rapid, sensitive, low-limit method. Functionalized nanoparticles are hopeful to be used as fluorescence probes in detecting trace elements in biological samples.(4) The CdS/ZnS core-shell structure nanoparticles were synthesized in hydrotropic solution and characterized. The shape of CdS/ZnS core-shell particle approximated to a ball with an average diameter of 20 nm. The fluorescence intensity of the band-side emission of the CdS/ZnS was strengthened, and the surface state emission was weakened. Quantitative determination of DNA by functionalized CdS/ZnS core-shell nanofluorescence probe. Various Factors were assessed and the suitable conditions were optimized for the assay of DNA. Linear relationship was found between the quenched fluorescence intensity and the concentration of DNA in the range of 0.0833～3.33μg/mL and 3.33～16.7μg/mL with the limit of detection of 2.50×10-3μg/mL. The method is also simple, cheap, rapid, sensitive and low toxicity.(5) A novel detection method for single nucleotide polymorphisms (SNPs) based on magnetic nanoparticle and CdS nanoparticle probes has been proposed in this work using fluorescence spectrometry and piezoelectric sensing. Magnetic nanoparticles were used to realize the isolation, separation and purification of DNA probes. Single nucleotide-coded CdS nanoparticles were synthesized and characterized. Magnetic nanoparticles coated by DNA strand with point mutation was immobilized onto the electrode surface with a magnet, ant then the CdS nanoparticle probes was utilized to search the mutation point via base-pairing. The hybridization of DNA with CdS nanoparticle probes caused changes of crystal frequency, whereas nearly no frequency changes for the complementary target could be recorded. Point mutation or single-base mismatch discrimination could be achieved successfully, and then each sample can be simultaneously identified by CdS fluorescent probes. Owing to its easy operation and cost-effectiveness, it was expected that the proposed procedure might hold great promise in both research-based and clinical genetic assays.
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