Determination Of Methylene Blue In The Plasma Based On Fluorescence Spectroscopy And Preparation Of Strong Fluorescence Silica Nanoparticles And Their Applications

In the first part of the paper, the fluorescence spectrophotometry has beenestablished to determine directly the trace amount of methylene blue in the plasmabased on the sensitizing effect of β-cyclodextrin on the fluorescence signal of methyleneblue. The linear range of methylene blue was0.089-3.57μmol/L （r=0.9988）, RSD was6.1%, and the recovery rate was95.9-108.3%. The method was simple and accurate,which could be used to determine the trace amount of methylene blue in the plasmawithout pretreatments, such as separation and enrichment.In the second part, this paper has studied the preparation of strong fluorescencesilica nanoparticles and their applicationsThe CdTe quantum dots （QDs） emitting green, yellow, orange and red fluorescencewas obtained in aqueous solution by adjusting the reaction time. The green, yellow andorange CdTe QDs with strong fluorescence could be got easily. But it need long time toprepare red CdTe QDs. At the same time, its fluorescence would become weak and theemission peak would broaden. Therefore, the red CdTe/CdS core-shell QDs with strongfluorescence was synthesized by epitaxial growth the nuclear layer of CdS on thesurface of the orange CdTe QDs. The emission peak of CdTe/CdS QDs was red-shiftedrapidly to615nm and the reaction time was reduced. By self-assembling of CdTe QDsand poly-diallyldimethylammonium chloride （PDADMAC） through electrostaticattraction, the polyelectrolyte-protected CdTe QDs （that is, QDs/PDADMACnanocomposites） was prepared. The QDs/PDADMAC nanocomposites showedstrip-like shape. Because the fluorescence properties of CdTe QDs were not affected andPDADMAC could effectively prevent mercaptoacetic acid ligands dropping out fromthe surface of QDs, the nanocomposites had more significant fluorescence stability than the bare CdTe QDs.Based on CdTe/PDADMAC nanocomposites, the core-shell silica fluorescencenanoparticles （CdTe/PDADMAC@SiO₂） was prepared via a water-in-oil reversemicroemulsion method. All of the particles were almost spherical and there was auniform distribution of the particle size with the average diameter about25nm. Ascompared with the CdTe@SiO₂, the CdTe/PDADMAC@SiO₂had much strongerfluorescence, and their fluorescence stability could be obviously improved. Theremaining fluorescence of CdTe/PDADMAC@SiO₂was up to76.4%by optimizingreaction conditions. The cytotoxicity and staining effect of CdTe@SiO₂andCdTe/PDADMAC@SiO₂nanoparticles were studied using A549lung cancer cell as amodel cell. The results showed that the cytotoxicity of CdTe/PDADMAC@SiO₂waslitter and the staining effect was better than those of CdTe@SiO₂.In order to solve the problem of litter yield, the common reverse microemulsionsystem was magnified five times and the results before amplification were reproducedby regulating the amount of each component. At the same time, we also synthesized redCdTe/CdS/PDADMAC@SiO₂with strong fluorescence and good stability.Thefluorescence spectra of CdTe/PDADMAC@SiO₂and CdTe/CdS/PDADMAC@SiO₂didnot overlap. Since their fluorescence spectra had no interference, they could be used asmarkers simultaneously for quantitative analysis.Ag@SiO₂composite nanoparticles were constructed successfully, of which Agcore was50nm and the thickness of silica shell was10nm. The composite nanoparticlescombined the surface plasmon resonance property of Ag nanoparticles and the perfectqualities of the silica, which was the common platform of metal enhancementfluorescence. Ag@SiO₂/Rh6G complex was formed by combining the positivelycharged rhodamine6G with Ag@SiO₂composite nanoparticles with the negativelycharged surface in the help of electrostatic interaction. Hydrogen peroxide did not affectthe fluorescence of rhodamine6G, and could degrade Ag core through the silica shell.Compared with the SiO₂/Rh6G without Ag core, the fluorescence intensity ofAg@SiO₂/Rh6G complex was enhanced1-fold due to the surface plasmon resonancefluorescence enhancement effect of Ag nanoparticles. Similarly, the fluorescenceintensity of IgG-FITC was enhanced0.7-fold after being assembed on the surface of Ag@SiO₂/PDADMAC composite nanoparticles.