Improving Optical and Charge Separation Properties of Nanocrystalline TiO₂ by Surface Modification with Vitamin C

Abstract

The structural and electrochemical properties of nanoparticles were found to be different from those of the corresponding bulk semiconductors. Due to the specific binding of modifiers to “corner defects”, the optical properties of small titania particles were red shifted 1.6 eV compared to unmodified nanocrystallites. It was found using electron paramagnetic resonance (EPR) that, as with organic charge transfer superconductors, these novel nanocrystallites operate with a charge-transfer mechanism, and exhibit semiconducting properties through both constituents (large band gap semiconductor and organic modifier). The EPR spectra were consistent with hole trapping on the surface modifier and electron trapping on shallow interstitial and partially delocalized Ti sites. These systems have an important feature in that charge pairs are instantaneously separated into two phasesthe holes on the donating organic modifier and the electrons in the conduction band of TiO2.

Effect of surface modified TiO2 nanoparticles on thermal, barrier and mechanical properties of long oil alkyd resin-based coatings

“…It can be seen that synthesized TiO 2 NPs have anatase crystal form and it has been estimated that their coherent domain size is around 3.6 nm, which is in good agreement with TEM result. According to the literature, TiO 2 NPs have on their surface some Ti atoms which are not in octahedral, but in square-pyramidal position [42]. The coordination number of such Ti atoms is therefore five and not six, and one of these five bonds between Ti and oxygen is shorter than others.…”

Preparation and characterization of whey protein isolate films reinforced with porous silica coated titania nanoparticles

“…Titania is a nontoxic and inexpensive material exhibiting bactericidal activity against a wide variety of microbes due to its photocatalytic activity. When incorporated into a polymer matrix, TiO 2 can provide protection against foodborne microorganisms as well as odor, staining, deterioration, and allergens in the presence of relatively low-wavelength radiation near the ultraviolet region (Rajh et al, 1999 andZhou et al, 2009). However, TiO 2 particles easily aggregate and thus deteriorate the properties of the film (Zhou et al, 2009).…”

In-Situ Versus Post-Synthetic Stabilization of Metal Oxide Nanoparticles

“…The post-synthetic modification of metal oxide nanoparticles has been investigated in a large number of cases, and with very different goals, not only for an enhancement of colloidal stability of the nanoparticles, but also to adjust many other properties, for example the optical and photocatalytic performance (Rehm et al, 1996;Rajh et al, 1999Rajh et al, , 2002Stowdam & van Veggel, 2004). Different classes of surface modifiers that have shown to be especially suitable for metal oxides include alkoxysilanes and chlorosilanes (Sanchez et al, 2001), carboxylic acids (Bourlinos et al, 2002;Arita et al, 2010), or phosphonic/phosphoric acid derivatives (Rill et al, 2007;Lomoschitz et al, 2011).…”