Titania/polypyrrole hybrid nanocomposites built from in-situ generated organically functionalized nanoanatase building blocks

A bifunctional capping ligand is used to obtain pyrrol-functionalized monodispersed nano-crystalline TiO2 (anatase) particles in a single step. The pyrrole functionalities in the shell are then (electro)chemically polymerized to create a polypyrrole (PPy)/TiO2 hybrid nano-composite film (see Figure). Further electronic modification of the conducting polymer is possible, leading to a great variety of potential applications

Striving for order and compositional homogeneity in bulk mesoporous zirconium titanium mixed metal oxides from triblock copolymers and metal chlorides.

Under consideration in this work is the prospect for the preparation of ordered, thermally stable, compositionally homogenous bulk zirconium titanate mesophases using a triblock copolymer template (F-I 27). As a starting point, well established evaporation-induced self-assembly procedures for the production of thin films have been adapted to the preparation of bulk materials. The composition of the precursor solution was fixed at ZrxTi1-xCl4:40 EtOH:0.005 F127:h H2O (x = 0.28, h = 10) and ambient humidity was varied in a systematic and precise fashion. It has been demonstrated that while it was possible to prepare materials with localized order at humidities exceeding about 20% relative humidity, these materials showed macroscopic phase segregation with very little zirconium entering the mesophase structure instead precipitating as zirconium oxide. This phase segregation resulted in poor thermal stability at 500 degrees C. In contrast, at humidities below about 20%, more thermally stable worm-like materials with compositional homogeneity on the transmission electron microscope length scale could be prepared. For comparison with bulk materials, thin films were also prepared from the similar precursor solutions. The results of these preparations were unexpectedly very similar to those of the bulk preparations. It has been clearly demonstrated that attempts to incorporate about 30 mol% zirconium resulted in destruction of long range mesoscopic ordering under the conditions used. An additional important result of this study is the observation that the pore size distribution (PSD) was shifted from about 2.5 nm to about 6.5 nm for an increase in relative humidity from 0% to 20% and from 6.5 to about 7.6 nm for relative humidity increase from 20% to 70% for a calcination temperature of 300 degrees C. At this temperature all materials remained stable although similar overall trends were observed in the pore diameter with humidity when the calcination temperature was increased to 500 degrees C even though there was evidence of phase segregation and pore collapse at this temperature especially for samples prepared at the higher humidities. The present results suggest therefore that regulation of humidity during evaporation step affords a certain level of control over porosity. © 2008, Elsevier Ltd

Chemical Design of Efficient Photoelectrodes by Heterogeneous Nucleation of Carbon Dots in Mesoporous Ordered Titania Films

The design of efficient and highly durable photoelectrodes requires innovative solutions that can be integrated into thin-film-based technologies. Mesoporous ordered titania, which is characterized by an organized porosity in the 2-10 nm range, represents an ideal matrix for such a purpose. One of the main challenges is the homogeneous and controlled incorporation of photoactive nanoparticles inside the matrix. Titania-carbon dots (C-dots) heterostructures represent promising candidates, but a method to homogeneously introduce C-dots in mesoporous films is still missing. In the present work, C-dots have been nucleated and grown within a mesoporous titania film through in situ solvothermal synthesis. The process promotes the crystallization of titania anatase at low temperatures and at the same time allows the formation of carbon dots without disruption of the porous ordered structure. The process allows building a high-performance nanocomposite as an electrode for oxygen evolution reactions. Photocurrent production under different illumination conditions was measured by linear sweep voltammetry and chronoamperometry. When exposed to a solar simulator, the nanocomposite electrodes yield an increase in photocurrent compared to bare TiO2 matrices. The better performance has been associated with the presence of C-dots acting as active light-harvesting sites and as charge donors to the photoactive centers of the titania film

Tin-based hybrid materials with a two-level structural hierarchy

Self-assembled tin-based hybrid materials with two levels of hierarchy were obtained spontaneously from the hydrolysis of hexaalkynylorganoditins bridged with an aromatic spacer, while in the case of an aliphatic spacer this phenomenon occurred only in the presence of a surfactant