Synthesis And Properties Of ZnO Nanocrystals With Biocompatibility

Research on photoluminescent semiconductor nanocrystals has receivedconsiderable interest owing to their potential applications as biological fluorescencelabeling during the past decades. ZnO is environmentally friendly semiconductor andis inexpensive luminescent material compared with traditionally used nanocrystals ofCdSe or CdTe, which makes it more attractive for the applications in biologicalfluorescence labeling. However, only a little research work has been reported on thesuccessful application of ZnO nanoparticles in biolabeling so far. Since almost allexperiments involving biolabeling require water-soluble materials, the major problemof ZnO nanoparticles arises from their poor stability in water.ZnO nanocrystals with strong blue emission have been synthesized via a facileroute. The as-synthesized ZnO nanocrystals were stable in water, even at basic oracidic aqueous conditions. The water stability of such ZnO nanocrystals was providedby the hydroxyl groups of triethylene glycol （TREG） and also the carboxyl group ofoleic acid （OA） on their surfaces. We found that heat temperatures, heat times andconcentrations of OA were all important factors that influence the particle size and thecrystallinity of the ZnO nanocrystals. Interestingly, the photoluminescence propertiesof ZnO nanocrystals were not dependent on the particle size, but were attributed to thesurface defects on ZnO which were closely related to the process of ZnO nanocrystalscoated by TREG.Silanization has been widely applied to provide colloids with stability andfunctionalized surfaces. Here, we used3-Aminopropyl triethoxysilane （APTES） tomodify the ZnO nanoparticles surface, and fabricated water-stable ZnO nanoparticleswith new facile synthesis method, which has yellow fluorescence. The as-synthesizedZnO nanocrystals were stable in water. However, they are unstable at basic or acidicaqueous conditions. We found that more APTES concentration resulted higherintensity of the UV emission and lower intensity of the yellow emission. Moreover,with the concentration of APTES increased, the UV emission peaks distinctlyblue-shifted, and more emission peaks appeared.A facile method was developed for synthesizing water-stable ZnO nanoparticleswith green emission.3-（2-Aminoethylamino） propyldimethoxymethylsilane was employed as capping agent. The as-synthesized ZnO nanoparticles were shown to behighly stable and soluble in water. Orthogonal experiment was employed to optimizethe correlated parameters of the reaction of capping ZnO nanocrystals with3-（2-Aminoethylamino） propyldimethoxymethylsilane. The effects of the quantity of3-（2-Aminoethylamino） propyldimethoxymethylsilane, KOH, ethanol, and reactiontime on the aqueous stability of the ZnO nanocrystals were investigated by orthogonalexperiment.ZnO/MgO quantum dots have been synthesized and capped with3-Aminopropyltriethoxysilane （APTES）. Orthogonal experiment was employed to optimize thecorrelated parameters of the reaction of capping ZnO/MgO nanocrystals with APTES.The water-soluble APTES-ZnO/MgO quantum dots emit strongly in the visibleregion on excitation by UV radiation and are stable over extended periods. Theaqueous-stability of the nanocrystals is attributed to the exposed hydrophilic groups（-NH₂,-OH）. Hemolytic results indicate that APTES-ZnO/MgO nanocrystals havegood biocompatibility, which is especially important for ensuring their potential inbiomedical applicationsTransmission electron microscopy （TEM）, X-ray diffraction （XRD）, UV-vis, andfluorescence spectrophotometer （PL） were employed to investigate the structures andproperties of all ZnO nanoparticles. Furthermore, hemolysis assay was performed toevaluate the biocompatibility of these ZnO nanoparticles in vitro.