High pressure (HP) techniques (0.1-100 GPa) are powerful methods to strongly modify the properties of condensed matter and produce unique materials with great impact on fundamental and applied sciences. Synthesis of new materials avoiding catalysts and any substances other than the reactants, has become a milestone in materials science. We want to use this approach in combination with the world of meso/micro-porous materials to create a HP laboratory at the subnano-scale by playing on densified simple molecular systems, such as water, methane, carbon dioxide, carbon monoxide, and light within the small space enclosed in the nano cages and channels of porous materials such as zeolites. Pressure-tuning the pore size can give rise to clean synthesis procedures of novel technological useful nano-composites with possible further extension to large scale production. In addition, a deep understanding of matter under strong confinement and even reduced dimensionality will be obtained. Materials exhibiting up to an order of magnitude increase in technologically interesting properties (electrical conductivity, optical generation, etc.) are expected to be discovered. A team of experimental and computational experts in high pressure techniques, molecular systems and new functional materials will pursue the design and synthesis of thus new class of nano-composites through HP polymerization of simple organic molecules or by suitable doping in zeolites channels. Composites possessing tailored mechanical and thermal properties, and unique transport and non-linear optical properties will be obtained. Hydrothermal synthesis of zeolites, diamond anvil cells for the HP synthesis of composites, neutron and optical spectroscopy, X-ray diffraction, electrical conductivity measurements, and computer simulations for designing synthesis strategies and interpreting experimental results will be used.
The project aims at understanding the deep effect that nano-cavities and nano-channel can have on the structural thermal and dynamical properties of simple molecular systems like water methane ammonia carbon dioxide, carbon oxide, nitrogen, which are among the most abundant molecules on earth and at the same to find a new way to synthesize isolated, single-chain polymeric nanostructures, featuring one-dimensional (1D) quantum-confined properties, in configurations suitable for exploitation as functional devices, with electrical, optical, mechanical readout.
The capability to prepare isolated and densely packed nanomaterials with a real one-dimensional structure in a way suitable for exploitation in functional devices is a major challenge in nanoscience and nanotechnology. Resolution limits and disorder effects are the main factors hindering the achievement of such results in inorganic materials when downsized to the sub-nm scale. Concerning organic materials, which are intrinsic 1D molecular-sized nanostructures, stability and inter-chain interactions, are the principal effects shadowing their 1D nature.
Our key elements to obtain such still unachieved materials are:
the use of inert zeolites with porosity controlled at the nm- and Å-scale, acting as ordered, templating, protective environment, suitable to host isolated, 1D polymeric chains and compatible with solid-state device fabrication;
the unprecedented use of high-pressure (HP) as the driving force to induce the polymerization of 1D nanostructures, namely conjugated polymers (CPs), such as polyacetylene, and carbon nanowires (CNWs), inside the zeolite cavities;
the use of HP-conditions to exploit excited states of precursors promoting the synthesis and stabilization of polymeric materials ¿ together with temperature light exposure. This will allow the exploration of a broad range of synthesis routes which cannot be performed through other methods.
The uniqueness of our project for a practical understanding of crystallization in nano-confinement and for future device development arise from:
The inertness of the zeolite-host and sub-nm pores, enabling the stabilization of unperturbed 1D nanostructures (minimal host-guest interaction);
The hierarchical porous structure of the zeolite material to host 1D materials and provide access to the external environment for exploitation as a device;
Zeolites prepared as powders and large (up to 0.1 mm long) crystals for easy integration in device substrates and functional measurements set-ups.
The joint exploitation of such key-elements and the expected features of the target materials hold the potential to overcome the limitations of current scientific and technological approaches which still hinder the development of 1D nanostructures and their full exploitation as devices.
The preparation and exploitation of materials with an effective and unperturbed 1D character has been, and still is, a fundamental but unfulfilled issue in nanoscience and nanotechnology:
Carbon nanotubes (CNTs) suffer strong reproducibility issues arising from poor control over their features such as chirality, single and multi-wall structures and require expensive, serial nano-manipulation techniques (inside electron microscopes), being parallel processing methods such as dielectrophoresis still not satisfactory [Angew. Chem. Int. Ed. 47 (2008) 6550; Nano Lett. 6 (2006) 263];
Inorganic nanowires (bottom-up prepared) suffer synthesis challenges as the diameter is shrunk down to the nm and sub-nm scale and share the same manipulation difficulties of CNTs [Nano Lett. 6 (2006) 263];
Inorganic nanowires (top-down prepared) suffer disorder effect at the nm- and sub-nm scale [Nature Phys. 2 (2006) 15];
Conjugated polymers, despite their intrinsic 1D nature, suffer aggregation or chain bending/branching phenomena in free-standing materials and polymer-host interactions in templated systems. These are among the most common effects introducing external forces superimposing to such intra-chain interactions responsible for the pure 1D behaviour [Nature 523 (2015) 196; Adv. Mater. 14 (2002) 553]. As a result, real 1D polymeric chains are nowadays stabilized in proper solutions or polymeric matrix [Science 331 (2001) 565], which make these ideal materials hardly available for technological exploitation, especially in gas-sensing, in which the polymeric chains are required to come in contact with the external environment.
In this scenario, our project aims to exploit HP-technology combined with finely tuned zeolite materials to overcome these challenges and make 1D polymeric nanostructures available as guest materials arranged in ordered arrays of isolated chains inside the crystallites of powdered or large single crystalline samples, suitable for integration in devices with optical/electrical/gravimetric readout mechanism.