Growth of TiO₂ nanocrystals in the presence of alkylpyridinium salts: the interplay between hydrophobic and hydrophilic interactions

Abstract

TiO 2 nanoparticles were prepared by combining a sol-gel precipitation with growth steps performed in the presence of cationic surfactants, dodecylpyridinium chlorides (DPC), and cetylpyridinium chlorides (CPC). Solutions at concentrations pertaining to the existence of either surfactant monomers or aggregates (micelles) were employed. XPS analyses were performed both on the surfactant salts and on the aged, dried precursors to study the surfactant films adsorbed onto the oxide. The crystal structures of the calcined samples and the phase composition were examined by X-ray diffraction. The role played by the presence of the surfactant in affecting the physicochemical properties of the powders is discussed.

A New Frontier of Photocatalysis Employing Micro-Sized TiO2: Air/Water Pollution Abatement and Self-Cleaning/ Antibacterial Applications

“…No significant differences can be appreciated among all the investigated samples in the Ti 2p region concerning both binding energies (BE) and full width at half-maximum (FWHM) values. The Ti 2p 3/2 peak is always present as a single doublet and the BE (forth column in Table 1) compares A New Frontier of Photocatalysis Employing Micro-Sized TiO 2 : Air/Water Pollution Abatement and Self-Cleaning/ Antibacterial Applications http://dx.doi.org/10.5772/62892 well with the data for Ti(IV) in TiO 2 [48]. The analysis of the oxygen peaks exhibits the presence of two different components, which can be attributed to lattice oxygen in TiO 2 (529.9 eV) and to surface OH species (>531.5 eV), respectively [49].…”

Synthesis and properties of cationic surfactants with tuned hydrophylicity

“…Within biological applications, they show a good antimicrobial activity [6] and can be used as drugs [7], gene delivery agents [8] or in DNA extraction methods [9]. Quite recently, cationic pyridinium surfactants have found applications in the synthesis of TiO 2 nanoparticles [10], in ionic liquids synthesis [11] or as electrolytes for dye-sensitized solar cells [12].…”

Mesoporous Titania Nanocrystals by Hydrothermal Template Growth

“…Several liquid-crystal templating (LCT) techniques, exploiting three-dimensional structures of ionic/nonionic surfactants [5][6][7][8][9][10] and block copolymers [11][12][13] have been proposed to synthesize mesoporous titanium oxides. The presence of mesoscopic pores in TiO 2 for dye-sensitized solar cells is of great importance; in fact when the pores are filled with a conducting medium, charge carriers can easily percolate across the mesoscopic particle network making the whole internal surface area electronically accessible [14].…”

“…Together with the surface area/porosity, also the grain size and relative enrichment in the different oxide polymorphs should be controlled through template routes to promote the best efficiency of the TiO 2 -based semiconductors [9,10]. Crystallite sizes in the range of 10-80 nm are considered optimal for both optical absorption and electron transport in the conversion of solar light to electric current, by dye-sensitized solar cells [14,17,18].…”

“…Here we report on the synthesis, of TiO 2 nanocrystals, through a simple process implying a sol-gel starting reaction, followed by a growth step in solution, performed, also, in the presence of monomeric or dimeric "gemini-like" alkylpyridinium surfactants. The latter ones are composed by two conventional single-tail amphiphilic moieties chemically connected by spacer groups, usually polymethylene or short poly(oxyethylene) chains [10,21]. Recently, many studies concerning the practical use of gemini molecules appeared in the literature [22][23][24][25], showing that the first speculative interests were followed by practical applications, due to their unusual properties, such as the lower critical micellar concentration (CMC) values, the better adsorption behavior at both the air/water and the solid/water interfaces with respect to their single monomers, and the tendency to form micelles of different shapes and dimensions (i.e., spherical, rodlike, threadlike, vesicles), even at low concentration, when compared with similar nongemini surfactants.…”