Study On Synthesis Of Two Nano Inorganic Phosphates In SDS-PVP System

In many kinds of inorganic phosphates, hydroxyapatite (HAP) and lanthanide phosphates, as the main components of hard issues and as one of the most important luminescent materials respectively, have attracted extensive research attention due to their excellent application prospect. Comparing with bulk materials, nano materials have many special characteristics, so the reaserch works about the synthesis and applicaion of nano HAP and LnPO₄ have become one of the focuses of material science.In this dissertation, definition and properties of nano materials are reviewed, the properties, application and main synthetic methods of nano HAP and nano lanthanide phosphates LnPO₄ (LnPO₄ = LaPO₄: Ce, Tb) are introduced. The following topics were explored: how to investigate the characteristics of sodium dodecyl sulfate- polyvinylpyrrolidone (SDS-PVP) aqueous system, how to prepare nano HAP with uniform morphology, narrow distribution of particle size and good biosafety and how to synthesize one-dimensional LnPO₄ with good aspect ratio and excellent optical performance in SDS-PVP system, and how to get LaPO₄-LnPO₄ core-shell structure material with low cost and good luminescence.Surface tension properties of Ca²⁺-SDS-PVP and La³⁺-SDS-PVP systems were measured by drop volume method. The results showed that theγ-lgc curves of these two systems all had two critical concentrations. The mechanism of SDS and PVP interaction in aqueous solution was also explored. The suitable SDS concentrations for preparing nano HAP and nano LnPO₄ were also discussed.In SDS-PVP system, the nano HAP obtained by microwave-assistance in controlled temperature had higher crystalline degree and more regular morphology, comparing with the products synthesized in ordinary water bath. It indicates that microwave-assisted method is an ideal way for rapid preparation of nano hydroxyapatite. Then the mechanism of nano HAP growth and the possible influence of SDS-PVP template and microwave effects are discussed. The characterization results and drug-loading experiments of nano HAP obtained by 700 W microwave irradiation for 100 min with refluxing prove that our products are rod-like hexagonal nano crystals with about 15-25 nm in width, 50-100 nm in length. After alternately washing by ultrapure water and ethanol many times, SDS and PVP have been thoroughly removed. With good thermal stability and good drug loading performance, and also with good biosecurity and good biocompatibility, our nano HAP is expected to be an excellent slow-release drug carrier material.The influence of soft template SDS-PVP to the formation of nano LnPO₄ was investigated. In SDS-PVP system, nano LnPO₄ was synthesized by three different methods: ordinary water bath, microwave-assisted route and hydrothermal treatment method, respectively. The luminescence mechanism of nano LnPO₄ was also discussed. TEM results show that the soft template of SDS-PVP can effectively controls the particle size of nano LnPO₄ and prevents the reunion of nano particles. XRD and fluorescence spectra analysis reveal that microwave method can produces hexagonal nano LnPO₄ with better crystallinity and higher fluorescence intensity, comparing with the properties of nano hydroxyapatie obtained in water bath. Fluorescence spectra and photoluminescence figures indicate that the fluorescence emission intensity of products prepared by hydrothermal treatment is the highest. This demonstrates that the optical performance of monoclinic crystal nano LnPO₄ is greatly improved . This nano LnPO₄ is expected to get potential application in the future in luminescence field.In SDS-PVP system, nano crystals of green luminescent material LnPO₄ growed around the cheap core material LaPO₄, the core-shell structure, LaPO₄-LnPO₄, was obtained by heterogeneous nucleation approach. This product has both low synthetic cost and good luminescence property. This method might has important application in fluorescent lighting industry.