Preparation And Application Of Oil-Soluble Inorganic Nanoparticle Modified With Silica

The oil-soluble nanoparticles have good dispersion stability in the organic phase and can be successfully applied to various non-aqueous media,but its application in aqueous environments is limited.Therefore,some methods are needed to transfer oil soluble nanoparticles into aqueous media?phase transfer?.Silica has the advantages of strong chemical inertness,good photochemical stability,good biocompatibility,and easy to modify in surface.Therefore,silica coating has some unique advantages in phase transfer.Based on this,the water-dispersible Cu@SiO₂ composite microspheres and the carboxy-functionalized SiO₂-CdSe/ZnS quantum dot?QDs?composite microspheres were prepared by silica coating.Because the surface of Cu@SiO₂ composite microspheres contains a large amount of Si-OH,it has good dispersion stability in water,and silica and Cu nanoparticles have good antifriction and antiwear properties,so Cu@SiO₂ composite microspheres can be used as a water-based lubricant additive.Due to the carboxyl-functionalization of SiO₂-CdSe/ZnS QDs composite microspheres has good biocompatibility,it can be successfully applied in the field of biological detection.The following results have been obtained in this paper:1.Preparation of water-base Cu@SiO₂ composite microspheres and their tribological properties in water based lubricating systemUsing reverse microemulsion method and Igepal CO-520 as surfactant,cyclohexane and trace amounts of water formed a microemulsion system.Under the catalysis of ammonia water,hydrolysis and condensation reaction of the silica precursor TEOS occurred,and water-soluble Cu@SiO₂ composite microspheres were prepared.The effects of the amount of tetraethoxysilane?TEOS?,the amount of ammonia water and several methods of preventing the oxidation of Cu nanoparticles on the morphology of the composite microspheres have been investigated.The colloidal stability of Cu@SiO₂ composite microspheres is monitored by dynamic light scattering.After storage for 30 days,Cu@SiO₂ composite microspheres exhibits little size variation,and its hydrodynamic diameter remains at 230 nm.This indicates that Cu@SiO₂ composite microspheres have good dispersion stability in distilled water and no agglomeration phenomenon occurs.The oxidation stability of Cu@SiO₂ composite microspheres was investigated by oven oxidation experiments.The distilled water which containing Cu@SiO₂ composite microspheres was continuously treated in an oven at 80?for 7 h.It was found that there is no obvious change in color,indicating that copper nanoparticles were not oxidized,proven that prepared Cu@SiO₂composite microspheres had excellent resistance to oxidation in distilled water.In several methods for preventing Cu nanoparticles from oxidation,it was found that adoption Ar as a protective gas is the best method to prepare Cu@SiO₂ composite microsphere with good morphology and not oxidized.In the meantime,the tribological properties of as-prepared Cu@SiO₂ composite microspheres as a lubricant additive in distilled water were investigated with a UMT-2MT and UMT-5 MT tribometer.The friction test results show that the prepared Cu@SiO₂ composite microspheres as a water-based additive can effectively improve the tribological properties of distilled water.2.Preparation of water-base SiO₂-CdSe/ZnS QDs composite microspheres and their application in detection of procalcitonin?PCT?in microporous immunochromatographic systemUsing reverse microemulsion method and Igepal CO-520 as surfactant,cyclohexane and trace amounts of water formed a microemulsion system.Under the catalysis of ammonia water,hydrolysis and condensation reaction of the silica precursor TEOS occurred,water-soluble SiO₂-coated single core oil-soluble CdSe/ZnS QDs composite microspheres were prepared.Because the prepared SiO₂-CdSe/ZnS QDs composite microspheres have good water solubility,so after carboxy-functionalization the SiO₂-CdSe/ZnS QDs composite microspheres can be successfully applied into the bio-detection.Previous studies have shown that the detection sensitivity of SiO₂-coated single core oil-soluble CdSe/ZnS QDs composite microspheres is poor,so it is necessary to prepare SiO₂-CdSe/ZnS QDs composite microspheres with multi-core to improve the sensitivity of biological detection.We prepared SiO₂-CdSe/ZnS QDs composite microspheres with multi-core by two-step reaction.The specific process is as follows:the first step was to form seeds by using ligand exchange between hydrophobic ligand on CdSe/ZnS QDs surface and?3-mercaptopropyl?trimethoxysilane.The second step was to introduce of silica precursor TEOS,hydrolysis and condensation reactions occur around the seeds formed in the first step,silica growth was performed and water-soluble SiO₂-CdSe/ZnS QDs nanocomposite microspheres coated multi-core of hydrophobic CdSe/ZnS QDs were successfully prepared.We synthesized water-soluble SiO₂-CdSe/ZnS QDs nanocomposite microspheres coated with 5,11 and 23 CdSe/ZnS QDs,respectively,by adjusting the concentration of hydrophobic CdSe/ZnS QDs.SiO₂-CdSe/ZnS QDs nanocomposite microspheres with different silica shell thicknesses were prepared by adjusting the amount of TEOS.The prepared SiO₂-CdSe/ZnS QDs composite microspheres were carboxyl-functionalized with 3-?triethoxysilyl?propylsuccinic anhydride,these fluorescent microspheres at different pH values,different NaCl concentrations,and different temperatures can both stably exist and maintain good fluorescence stability,which can meet the needs of biological detection.The combination of carboxyl-functional composite microspheres with immunochromatographic strip technology was successfully used to detect procalcitonin?PCT?.Relative to single core composite microspheres?sensitivity 2 ng/mL?,multi-core composite microspheres?11,sensitivity 0.05 ng/mL?can significantly increase the detection limit of the detection system.However,by comparing the detection limits of the prepared SiO₂-coated multi-core?5 cores,11cores,23 cores?CdSe/ZnS QDs composite microspheres,we found that the detection sensitivity of the carboxy-functionalized composite microspheres did not increase linearly with the number increase of oil-soluble CdSe/ZnS QDs coated with silica.However,after the number of CdSe/ZnS QDs was increased to a certain range,the effect of improving the detection sensitivity was no longer obvious because of fluorescence quenching and the competition effect between fluorescence emission and light absorption.The silica shell thickness of SiO₂-CdSe/ZnS QDs composite microspheres has not obvious effect on the stability in physiological environment,and it has no obvious effect on the detection sensitivity of the detection system.