Correlating the Morphological Properties and Structural Organization of Monodisperse Spherical Silica Nanoparticles Grown on a Commercial Silica Surface

Abstract

A variety of nanosilicas have been widely used to fabricate rough surfaces with superhydrophobic and superhydrophilic properties. In this context, we prepared mixed silica and mixed nanosilica that were generated by the growth and self-assembly of synthesized monodisperse silica nanospheres (11-30 nm, 363 m(2) g(-1) ) on the surface of Sylopol-948 and Dispercoll S3030 by using a base-catalyzed sol-gel route. Using this process, the interactions and hierarchical structure between the nano- and microsized synthesized silica particles were studied by changing the amount of tetraethoxysilane. The resulting materials were characterized by BET analysis, small-angle X-ray scattering (SAXS), dynamic light scattering, FTIR spectroscopy, and SEM. The mixed silica presented a higher specific surface area (326 m(2) g(-1) ), a six-fold higher percentage of (SiO)6 (44-68 %), and a higher amount of silanol groups (14.0-30.7 %) than Sylopol-948 (271 m(2) g(-1), 42.6 %, and 12.5 %, respectively). The morphological and hierarchical structural differences in the silica nanoparticles synthesized on the surface of commercial silica (micrometric or nanometric) were identified by SAXS. Mixed micrometric silica exhibited a higher degree of structural organization between particles than mixed nanosilica.

Alternative Approaches in Development of Heterogeneous Titania-Based Photocatalyst

“…However, both approaches are valid for the degradation of organic pollutants from supports such as silicas synthesized by sol-gel, because nano-micrometer photocatalysts (25.4-30.1%) also were better than the P25 under visible radiation. The advantage of a nano-micrometric system resides in the possibility of reusing the catalyst several times as have already studied (27,28,50), which is a current limitation of nanoscale catalysts.…”

“…Functionalized nanosilicas were prepared by the hydrolysis of TEOS using a standard procedure described in the literature (21,27). Thereafter, SiCl 4 was added to the nanoparticles in solution.…”

“…Small-angle X-ray scattering (SAXS) measurements were performed at the SAXS1 beamline at the National Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The scattered X-ray beam presenting a wavelength (λ) of 1.488 Å was detected on a Pilatus 300 k detector (27). I(q) vs. q scattering profiles were fit by multi-level of structural organization using the Beaucage model (41-43) in the Irena routine (44).…”

“…The broadband between 1300-1000 cm −1 was deconvoluted via Gaussian functions into four independent components: two (TO 4 and TO 6 ) associated with the transverse-optic (TO) modes and two (LO 4 and LO 6 ) with the longitudinal-optic (LO) modes of Si-O-Si using a nonlinear least-squares fitting method [39]. The percentage of sixfold rings (SiO 6 ) in the silica network (Q 6 ) was estimated using the following ratio of fitted areas (27,48,49…”

“…Phenol, drugs, pesticides, and dyes have been investigated as the target pollutant. In parallel, some alternative approaches in the development of potential heterogeneous photocatalyst, namely (i) the use of industrial wastes as source of photocatalyst systems which were impregnated on commercial supports (20)(21)(22); (ii) the use of the concept of molecular imprinting (MI) to afford selectivity to the adsorption and photocatalyst degradation of target molecules (23)(24)(25), and (iii) combination of nano-and micro-particles as supports (26)(27)(28) for the impregnation of titania active species were explored. Regarding to the former, the rationale was that several photocatalyst systems imply the use of metal doping to guarantee a better photocatalyst activity or to shift the spectrum of actuation toward the visible spectrum region.…”