Nanosystems Built through Self-Assembled Nanobuilding Blocks: towards responsive and programmable materials.

G.J. A. A. SOLER ILLIA

Conferencia; Atlantic Basin Conference; 2018

In the last decade, we are witnessing a significant advance in materials chemistry, reflected in the nowadays wide available palette of nanomaterials. One of the key factors of this impressive progress is the possibility of producing a great variety of nanobuilding blocks (NBB), and harnessing self-assembly processes at the nanoscale. The combination of these two powerful concepts opened the path to achieve control over complex materials with hierarchical architectures at different length scales, which mimick the complexity of those found in Nature. In particular, the combination of sol?gel synthesis, surfactant self-assembly and surface modification leads to obtain mesoporous materials with high surface area (200-2000 m2/g) and highly controlled mesopore diameter (2-50 nm). The synthetic strategies to produce these systems have evolved from the mere production of high surface area materials, to achieve highly controlled pore systems that can be ?decorated? with organic, biological or nanoscale functions located in the inorganic framework, pore surface or interior. The properties of these nanostructures are tuned by the pore size and geometry, wall composition and surface features. The next step is turning these complex nanomaterials to programmable nanosystems, in which confinement effects, responsivity, or collaborative functionality can be imparted into the structure through the control of positional chemistry of different chemical building blocks that represent different functional domains. In this presentation, we will illustrate the richness of this emergent field by analyzing the designed synthesis of Mesoporous Thin Films (MTF), which are finely tuned in their pore size, interconnectivity or wall nature. Control over structure and architecture permits to tailor optical, electronic or catalytic properties, through simple production methods compatible with the electronics or optics industries. Production of MTF relies in the accurate control of the self-assembly of inorganic amorphous or nanocrystaline nano-building blocks (NBB) with supramolecular templates. Mesopores also provide monodisperse cavities that can be modified by adding small molecular species, biomolecules or polymers, leading to hybrid MTF with an amazing variety of chemical behaviors, which include responsivity to temperature, pH, redox potential or the presence of molecules. Nanoparticles (NP) can also be included in the mesopores, leading to NP@MTF nanocomposites with novel catalytic, optical or thermal properties. In addition, sophisticated theoretical models and coarse-grain simulations are an essential tool to understand the complexity of the synthesis paths and the final properties. This in-depth understanding permits the rational evolution from materials synthesis to ultimate complex materials design. The MTF platform can indeed be adapted to generate colloidal systems. The combination and constant feedback of synthetic procedures, thorough characterization and simulation at several length scales leads to pre-designed nanosystems with increasing complexity and responsiveness. In addition, each highly controlled MTF originated from a reproducible and modular synthesis is in itself a building block for more complex structures. For example, pre-designed multilayer MTF structures are tunable, responsive photonic crystals or waveguides that can couple chemical and optical information. MTF multilayers presenting different chemical properties can be used as spatial scaffolds to host different chemical or biochemical groups with well-defined positioning, leading for example to tunable catalysts, or enzyme hosts. In all cases, the adequate understanding of local, colloidal and surface interactions as well as confinement effects permits to achieve a potentially infinite variety of complex nanosystems with externally controllable behavior. Control of the spatial location of pre-designed and well-controlled components at the molecular, mesoscopic or macroscopic lengthscales opens the path to design intelligent matter.