Organization of nanomaterials through self-assembly is an important example of disorder to order evolution of nanoscaled systems. Mesoporous materials show an ordered porous structure at the mesoscale (2-50 nm) whose formation is driven by the fast solvent evaporation during processing. An ordered porous topology is achieved in mesoporous thin films by a combination of sol-gel and supramolecular chemistry using a micelle templated self-assembly process. In the last years an increasing number of scientific articles and reviews have been dedicated to the subject because of its interest for basic science and the envisaged applications in several fields. These materials are obtained through a process which needs controlling of several synthesis and processing parameters; they represent an interesting challenge to our capabilities of understanding orderdisorder transitions in complex systems. Order in mesoporous silica films is, in fact, connected to the structural organization of pores, to transitions between different types of phases, the presence of welldefined building block units, and structure in the pore walls. We have critically reviewed the concepts behind self-organization in mesoporous silica films by discussing several aspects in which order is involved.

One-pot self-assembled hybrid films were synthesized by the cohydrolysis of methyltriethoxysilane and tetraethoxysilane and deposited via dip-coating. The films show a high "defect-free" mesophase organization that extends throughout the film thickness and for domains of a micrometer scale, as shown by scanning transmission electron microscopy. We have defined these films defect-free to describe the high degree of order that is achieved without defects in the pore organization, such as dislocations of pores or stacking faults. A novel mesophase, which is tetragonal I4/mmm (space group), is observed in the films. This phase evolves but retains the same symmetry throughout a wide range of temperatures of calcination. The thermal stability and the structural changes as a function of the calcination temperature have been studied by small-angle X-ray scattering, scanning transmission electron microscopy, and Fourier transform infrared spectroscopy. In situ Fourier transform infrared spectroscopy employing synchrotron radiation has been used to study the kinetics of film formation during the deposition. The experiments have shown that the slower kinetics of silica species can explain the high degree of organization of the mesostructure.

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The knowledge of the physics and the chemistry behind the evaporation of solvents is very important for the development of several technologies, especially in the fabrication of thin films from liquid phase and the organization of nanostructures by evaporation-induced self-assembly. Ethanol, in particular, is one of the most common solvents in sol-gel and evaporation-induced self-assembly processing of thin films, and a detailed understanding of its role during these processes is of fundamental importance. Rapid scan time-resolved infrared spectroscopy has been applied to study in situ the evaporation of ethanol and ethanol-water droplets on a ZnSe substrate. Whereas the evaporation rate of ethanol remains constant during the process, water is adsorbed by the ethanol droplet from the external environment and evaporates in three stages that are characterized by different evaporation rates. The adsorption and evaporation process of water in an ethanol droplet has been observed to follow a complex behavior: due to this reason, it has been analyzed by two-dimensional infrared correlation. Three different components in the water bending band have been resolved.

The reactions of 3-glycidoxypropyltrimethoxysilane in a highly basic aqueous solution have been studied by multinuclear magnetic resonance and light scattering techniques. The study has shown that in this peculiar chemical environment the alkoxy groups of 3-glycidoxypropyltrimethoxysilane undergo a fast hydrolysis and condensation which favor the formation of open hybrid silica cages. The silica condensation reaches 90% at a short aging time but does not go to completion even after 9 days. The highly basic conditions also slow down the opening of the epoxies which fully react only after several days of aging. The epoxy opening generates different chemical species and several reaction pathways have been observed; in particular, the formation of polyethylene oxide chains, diols, termination of the organic chain by methyl ether groups and formation of dioxane species. These reactions are slow and proceed gradually with aging; light scattering analysis has shown that clusters of dimensions lower than 20 nm are formed after two days of reactions, but their further growth is hindered by the highly basic conditions which limit full silica condensation and formation of organic chains.

Patterning mesostructured films is becoming an important area of research for its technological implications. Self-assembled mesoporous materials synthesized through templating of nano-objects offer, in fact, the possibility of hosting active organic molecules or nanoparticles, and several applications in photonics and microelectronics are now emerging. At the same time, new "unconventional" lithographic techniques are also available to design nano-or microscale patterned mesoporous structures. We discuss the recent developments of lithographic methods for patterning mesoporous materials; some applications and future trends are also envisaged in the present review.

Mesostructured films are an ideal material for incorporation of fluorescent dyes; controlling the doping process is, however, a critical step because the dyes will be constrained in a complex chemical environment. We have incorporated rhodamine 6G, a well-known fluorescent dye, in silica mesostructured 2d-hexagonal films at different concentrations. We have used dense silica films as reference material to compare the effect of incorporation of rhodamine 6G in mesostructured and dense materials. We have also prepared mesostructured films at different surfactant concentrations to compare the surfactant effect on dye aggregation state. The dye-doped films have been characterized by UV-vis absorption spectroscopy and emission and excitation fluorescence spectroscopy. At high dye concentrations, nonfluorescent sandwich H-type dimers are formed, but in mesostructured films the amount of this type of aggregates is reduced and the formation of fluorescent J-type dimers is favored. The presence of the surfactant within the mesopores gives rise to fluorescent dimers (J-type) at the expense of the nonfluorescent sandwich H-type.

In situ and time-resolved simultaneous analysis by two different and complementary techniques, Fourier transform infrared spectroscopy (FTIR) and small-angle X-ray scattering (SAXS), has been developed. A conventional source for the infrared light and synchrotron radiation for the X-ray beam have been used. The new technique has been applied to the study of self-assembling mesostructured films during dip-coating. The combined FTIR and SAXS analytical approach has given the possibility of getting a direct correlation between the chemical processes and the structural changes occurring in the film during the deposition.