Synthesis Of Gd₂O₃:Eu³⁺ @ Mesoporous SiO₂ Core-shell Nano-composite And Their Application As Drug Carrier

In the past decades, ordered mesoporous silica materials have received great attention due to their attractive features, such as non-toxic nature, stable mesoporous structure, high specific surface area, narrow and tunable pore size distribution. For these reasons, the ordered mesoporous silica materials become the outstanding candidate for drug carrier and some other applications.Lanthanide-doped inorganic nanocrystal has photochemical stability and low toxicity properties for biodetection compared with the organic dyes and the quantum dots.Recently, a lot of researches focus on fabricating the bifunctional materials which combine ordered mesoporous silica materials with the lanthanide-doped inorganic nanocrystal, because these bifunctional materials may have potential application in the fields of drug delivery ,disease diagnosis and therapy. This drug delivery system not only possesses a high pore volume and large specific surface area for storage and bonding drag molecules, but also has photoluminescence properties which can be tracked to evaluate the efficiency of the drug release. But most of the research groups synthesize the ordered mesoporous silica core first, then coat or functionalize the core with the lanthanide-doped nanocrystal Here in this work, we fabricated a new kind of core-shell bifunctional nanosphere with Gd2O3:Eu3+ nanocrystal as the core and the ordered mesoporous silica as the shell. The average size of this material is 180nm with narrow size distribution (170-200nm). Depending on the reports, the"ideal"size requirements for nanoparticles developed for treatment in vivo are between 70 and 200 nm (small particles (<20–30 nm) are eliminated by renal excretion. Larger particles can be rapidly taken up by themononuclear phagocytic system (MPS) cells present in the liver, the spleen, and to a lesser extent, in the bone marrow. Nanoparticles of 150–300 nm are found mainly in the liver and the spleen, whereas particles of 30–150 nm are located in bone marrow, the heart, the kidney and the stomach.). So the size of the nanosphere we fabricated can just meet the demands. And the nanosphere also has some other good properties such as perfect spherical shape, non-agglomeration, high brightness and high resolution.The Gd(OH)3:Eu3+ nanospheres were synthesized by solvothermal method. Then the core was encapsulated with mesoporous silica by sol-gel reactions. After calcination, the Gd(OH)3:Eu3+ core was transformed into Gd2O3:Eu3+ and the surfactant was removed from the mesoporous silica. Many Characterization methods were employed in studying the structure, morphology, porosity, and optical properties of the material, such as XRD, SEM, TEM, N2 adsorption, and PL spectra.According to XRD, the Gd2O3:Eu3+ we fabricated belong to a body-centered cubic structure and the Gd2O3:Eu3+ has crystallized very well; According to N2 adsorption, the existence of the ordered mesoporous structure was obvious. The fact that the Volume Absorbed decreased after loading IBU suggests that the mesoporous channels have been partially filled with IBU. In addition, we found some other conclusion through the experiment as follows:(1) The conclusion about fabricating the Gd(OH)3:Eu3+ core is as follow. using CTAB and PVP as the surfactant, FeCl3·6H2O as the catalyzer, we can fabricate the Gd(OH)3:Eu3+ nanoparticle in DMF system at 200℃by solvothermal method.(2) The conclusions about the ordered mesoporous silica coating are as follows.①The reaction was carried out under the mix system of water and ethanol. The ethanol was necessary in forming the regular morphology, but ethanol act as negative effects in forming the mesoporous channels. So use ethanol as less as possible when it does not affect forming the regular morphology.②Using TEOS moderately. We want to ensure the slower reaction rate, but also to ensure a high concentration of TEOS to form mesoporous.③When you need to expand the aperture in a small area, the slow drip of TEOS can solve the problem.(3) The conclusions about the fabricated material properties are as follows.①The PL emission and excitation intensities of the coated sample are lower than that of the uncoated sample, and the main excitation wavelength was blue-shifted after coating.②The increased lifetime is observed after coating.In General, we fabricated a novel kind of material as drug carrier. This drug delivery system not only possesses slow release property, but also has photoluminescence properties which can be tracked to evaluate the efficiency of the drug release. This kind of material has many potential applications in the future.