Paula C. Angelomé

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

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.

Ordered mesoporous hybrid thin films with double organic functionality and mixed oxide framework

Highly ordered mixed framework mesoporous cubic (Im3m) or 2D hexagonal (p6m) thin films of (M1−x(Si–R)x)O2−x/2 bearing organic groups (M = Ti or Zr, R = propylamine, mercaptopropyl or phenyl, x ≤ 0.2) are obtained by one-pot dip-coating. A second organic function (R′ = hexadecyl, phenyl, sulfonate…) can be added by post-grafting with a molecule presenting a chelating group capable of anchoring to the M sites (phosphate, phosphonate, polyhydroxyphenol, carboxylate…) and a second organic group. This two-step procedure leads to bifunctional accessible mesopores. The role of post-synthesis stabilisation treatments, the alternative processes for template extraction, and the pore accessibility towards a second function are presented and discussed.

Hybrid non-silica mesoporous thin films

Large-pore TiO2 and ZrO2 mesoporous films with 2D-Hex or cubic mesostructures were prepared by dip-coating. Organic bifunctional molecules presenting an organic function and a complexing grafting group (phosphate, carboxylate) were explored as surface modifiers. The incorporation of these functions into the mesoporous network was monitored by crossed FT-IR and EDS techniques. Leaching experiments in different conditions were performed to assess the anchoring of the grafted groups. While phosphate or phosphonate groups are strongly grafted, carboxylate functions can be released in a pH-dependent way.

Synthesis and applications of mesoporous nanocomposites containing metal nanoparticles

AbstractMetal nanoparticles (NP) and mesoporous (MP) oxides are complementary materials, since the size scale of pores in MP oxides matches that of NP and both systems have potential applications in similar fields. Besides, nanocomposites obtained through their combination possess not only the intrinsic properties of each component, but also new features derived from the synergy between them, mainly due to the high interfacial area between the metal and the oxide. Thus, new optical, catalytic and sensing properties can be achieved that are not easily available from the individual components. In this review, we focus our attention on such NP@MP composites, not only from the point of view of the most common synthesis pathways but also briefly describing their applications in fields as diverse as (photo)catalysis, sensing, photochromism and other optical properties, as well as patterning.

Selective SERS Sensing Modulated by Functionalized Mesoporous Films

A hybrid material comprising metal nanoparticles embedded in functionalized mesoporous thin films was constructed, and its use as a selective SERS-based sensor was demonstrated. The presence of specific functional groups in the pore network allows control over the surface chemistry of the pores, tuning the selectivity for specific molecules. Amino-functionalized hybrid mesoporous thin films were used in a proof of concept experiment, to discern the presence of methylene blue (MB) in mixtures with acid blue (AB), with no need for any sample pretreatment step. Selective detection of MB was possible through entrapment of AB in the mesoporous matrix, based on its high affinity for amino groups. The sensor selectivity can be tuned by varying the solution pH, rendering a pH responsive surface and thus, selective SERS-based sensing. The developed sensors allow specific detection of molecules in complex matrixes.

Tethering Luminescent Thermometry and Plasmonics: Light Manipulation to Assess Real-Time Thermal Flow in Nanoarchitectures

The past decade has seen significant progresses in the ability to fabricate new mesoporous thin films with highly controlled pore systems and emerging applications in sensing, electrical and thermal isolation, microfluidics, solar cells engineering, energy storage, and catalysis. Heat management at the micro- and nanoscale is a key issue in most of these applications, requiring a complete thermal characterization of the films that is commonly performed using electrical methods. Here, plasmonic-induced heating (through Au NPs) is combined with Tb3+/Eu3+ luminescence thermometry to measure the thermal conductivity of silica and titania mesoporous nanolayers. This innovative method yields values in accord with those measured by the evasive and destructive conventional 3ω-electrical method, simultaneously overcoming their main limitations, for example, a mandatory deposition of additional isolating and metal layers over the films and the previous knowledge of the thermal contact resistance between the heating and the mesoporous layers.

Mesoporous Hybrid Thin Films: Building Blocks for Complex Materials with Spatial Organization

Mesoporous Hybrid Thin Films (MHTF) of a variety of compositions and embedded organic functions are produced by combining sol-gel synthesis, template self-assembly and surface modification. One-pot or post-grafting strategies permit to modify the pore surface behavior. Highly controlled MHTF issued from a reproducible and modular synthesis can be used as building blocks for more complex structures, presenting order at larger scales, and novel properties derived from this multiscale order. Multilayer stacks of MHTF presenting specific and different functions and frameworks located in a well-defined position have been produced by combining sequential film deposition, selective functionalization and dissolution. These systems present new properties such as localized chemistry or modulable photonic crystal behavior.