Facile synthesis and fine morphological tuning of dendritic mesoporous silica & titania nanospheres

Abstract

In comparison with traditional mesoporous materials, dendritic mesoporous silica&titania nanospheres (DMSTNs) with three-dimensional central radial pore channels and multiscale pores have larger pore volume, higher specific surface area, and easier accessible surfaces, making them promising carrier platforms for the applications in catalysis, drug delivery, heavy metals adsorption, etc. In this study, DMSTNs have been manufactured by a one-pot co-condensation method using titanium(diisopropoxide)bis(2,4-pentanedionate) (TDA) as the titanium source. Their morphologies and structures have been finely tuned by TDA content, reaction temperature, stirring rate, solvents, and so forth. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been utilized to directly reveal their differences. Two typical kinds of DMSTNs synthesized at different temperatures have been compared, covering N₂ adsorption-desorption isotherms, X-ray photoelectron spectroscopy (XPS), Raman spectrum, ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis-DRS), Fourier Transform Infrared spectroscopy (FT-IR), etc. XPS and Raman results testify that the chemical composition and architecture of these DMSTNs resemble those of titanium silicalite-1 (TS-1) zeolite. The hydrogen yield and the corresponding rate of DMSTNs synthesized at 120 ℃ are 3.56 µmol·g^-1 and 0.71 µmol·g^-1·h^-1, being about 2.99 times higher than those of DMSNs that solely own SiO₂ in the skeleton. Nevertheless, DMSTNs synthesized at 70 ℃ possess a 10.08 µmol·g^-1 yield and a 2.04 µmol·g^-1·h^-1 rate, nearly 8.47 times higher than those of DMSNs.