Browsing by Subject "Mesostructures"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Electrospun Fe2O3 entrenched SiO2 supported N and S dual incorporated TiO2 nanofibers derived from mixed polymeric template/surfactant: enriched mesoporosity within nanofibers, effective charge separation, and visible light photocatalysis activity
    (American Chemical Society, 2019) Pradhan, Amaresh C.; Uyar, Tamer
    The α-Fe2O3 promoted and SiO2 supported N and S dual incorporated TiO2 nanofibers (FeSiNST NFs) along with neat oxide NFs have been synthesized by electrospinning via sol–gel. The keen approach is that mixed polyvinylpyrrolidone (PVP) as template and cetyltrimethylammonium bromide (CTAB) as surfactant are responsible for the creation of mesoporosity within NFs. The photoluminescence (PL) spectrum and UV–visible diffuse reflectance spectroscopic (DRS) result revealed the role of α-Fe2O3 as catalytic promoter in FeSiNST NFs by suppressing electron–hole (e––h+) recombination, red shifting, and oxygen vacancies (Ovs). The design of FeSiNST NFs by combining with SiO2 as catalytic support and N and S as visible light absorbers in TiO2, beautifies the present study. The high photocurrent (3.2 mA/cm2), high Efb value (−1.0 V), and low Rct value (∼74 Ω) support the enhanced photocatalysis (photoreduction and photodegradation) by FeSiNST in visible light. Charge transfer phenomena, Ovs, mesoporosity, and separation of e––h+ are the vital factors for an effective photocatalysis achievement.
  • Thumbnail Image
    ItemOpen Access
    Periodic mesoporous hydridosilica-synthesis of an "impossible" material and its thermal transformation into brightly photoluminescent periodic mesoporous nanocrystal silicon-silica composite
    (2011) Xie, Z.; Henderson, E. J.; Dag, Ö.; Wang, W.; Lofgreen, J. E.; Kübel, C.; Scherer, T.; Brodersen, P. M.; Gu, Zhong-Ze; Ozin, G. A.
    There has always been a fascination with "impossible" compounds, ones that do not break any rules of chemical bonding or valence but whose structures are unstable and do not exist. This instability can usually be rationalized in terms of chemical or physical restrictions associated with valence electron shells, multiple bonding, oxidation states, catenation, and the inert pair effect. In the pursuit of these "impossible" materials, appropriate conditions have sometimes been found to overcome these instabilities and synthesize missing compounds, yet for others these tricks have yet to be uncovered and the materials remain elusive. In the scientifically and technologically important field of periodic mesoporous silicas (PMS), one such "impossible" material is periodic mesoporous hydridosilica (meso-HSiO1.5). It is the archetype of a completely interrupted silica open framework material: its pore walls are comprised of a three-connected three-dimensional network that should be so thermodynamically unstable that any mesopores present would immediately collapse upon removal of the mesopore template. In this study we show that meso-HSiO1.5 can be synthesized by template-directed self-assembly of HSi(OEt)3 under aqueous acid-catalyzed conditions and after template extraction remains stable to 300 °C. Above this temperature, bond redistribution reactions initiate a metamorphic transformation which eventually yields periodic mesoporous nanocrystalline silicon-silica, meso-ncSi/SiO2, a nanocomposite material in which brightly photoluminescent silicon nanocrystallites are embedded within a silica matrix throughout the mesostructure. The integration of the properties of silicon nanocrystallinity with silica mesoporosity provides a wealth of new opportunities for emerging nanotechnologies.