Critical aspects in the production of periodically ordered mesoporous titania thin films

Abstract

Periodically ordered mesoporous titania thin films (MTTF) present a high surface area, controlled porosity in the 2-20 nm pore diameter range and an amorphous or crystalline inorganic framework. These materials are nowadays routinely prepared by combining soft chemistry and supramolecular templating. Photocatalytic transparent coatings and titania-based solar cells are the immediate promising applications. However, a wealth of new prospective uses have emerged on the horizon, such as advanced catalysts, perm-selective membranes, optical materials based on plasmonics and photonics, metamaterials, biomaterials or new magnetic nanocomposites. Current and novel applications rely on the ultimate control of the materials features such as pore size and geometry, surface functionality and wall structure. Even if a certain control of these characteristics has been provided by the methods reported so far, the needs for the next generation of MTTF require a deeper insight in the physical and chemical processes taking place in their preparation and processing. This article presents a critical discussion of these aspects. This discussion is essential to evolve from know-how to sound knowledge, aiming at a rational materials design of these fascinating systems.

Versatility of Evaporation-Induced Self-Assembly (EISA) Method for Preparation of Mesoporous TiO2 for Energy and Environmental Applications

“…The EISA process was originally designed for the preparation of mesostructured silica thin films and several papers including reviews are available [1,6,21–29]. In recent years, a number of mesostructured materials have been prepared by combining sol-gel chemistry with surfactants.…”

Effect of proton intercalation on photo-activity of WO3 anodes for water splitting

“…Nitrogen-BET measurements are performed commercially to calculate sample surface area and to obtain pore size distribution. However, when dealing with thin films, several milligrams of sample are often essential to obtain accurate results [34] and sometimes the need to scratch the material from the substrate makes the experimental work challenging [35], increasing the inaccuracy of the results [36].…”

From template-assisted mesoporous titania powders to thin films: Differences and similarities

“…Even though literature can be found on controlling the porous properties and formation mechanisms for titania powders [13,20,21] as well as for titania thin films on dense supports [12,14,21], little is described in literature about the differences and similarities in synthesis control mechanisms when going from powders to thin films. Nevertheless, from a development point of view, it is very interesting to know whether optimized powder synthesis can be transferred to thin films directly without loss of the desired structural control and properties.…”

“…Furthermore, next to the differences in needed characterization techniques, there are also differences in the formation mechanism. For a full discussion of the template mechanisms the reader is referred to literature [6,[10][11][12][13] but some general considerations should be kept in mind. The mesoporous powders made by evaporation induced self-assembly (EISA) are formed by gradual evaporation of the reaction solution from a Petri dish in which the initial solution forms a liquid layer in the order of magnitude of millimeters thick.…”