Luminescent surface-functionalized mesoporous core-shell nanospheres and their cytotoxicity evaluation

Spherical shaped SiO2@Tb(OH)(3) nanospheres (core-shell NSs) with an average grain size of 300-350 nm were successfully synthesized at a large scale via sol-gel process with subsequent heat treatment. XRD results demonstrated the non-crystalline nature of the sample even after coating with terbium hydroxide. TEM and SEM images clearly showed that the prepared sample was highly monodispersed, perfectly spherical in shape, and mesoporous with narrow size distribution (an average crystalline size of 350 nm). XRD, TGA, TEM, SEM, and EDX results demonstrated that the terbium hydroxide layer was effectively grafted over the surface of the silica spheres, which was further verified using FTIR, UV/Visible, and emission spectral results. The emission spectrum of core-shell NSs demonstrates that Tb3+ is strongly bonded covalently to the silica framework with surface anchored oxygen atoms, thus preventing the accumulation of Tb3+ ions to give an efficient luminescence. The emission spectrum was dominated by D-5(4)-> F-4(5) of the Tb3+ ion located in the green region at 2.88 eV along with broad emission of the silica framework. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium) bromide and neutral red uptake assays on MCF-7 and A-549 cells clearly illustrated the high biocompatibility and non-toxic nature of the samples. Because of the high specific surface area, mesoporous nature, and presence of abundant hydroxyl groups on the surface of the particles, these materials can be applied for tagging bioactive molecules or for loading high quantity anti-cancer drugs for biomedical applications.