What is your “sol-gel” background?
I began working in the homogeneous precipitation of oxide precursors by urea decomposition in the mid-‘90s, in Miguel Blesa’s group (Buenos Aires, Argentina). We were inspired by the work of Egon Matijevic, and we went after the controlled synthesis of monodisperse oxide sols. We studied how to tune the hydrolysis and condensation chemistry of Cu(II)-Zn(II) and Cu(II)-Ni(II) pairs, in order to get homogeneous mixed oxides. We found that complex physical-chemical phenomena such as the chemical reactivity at the molecular level, but also the development of surface charges, local concentrations, complexation etc, were in the basis of the control of the particles’ composition, morphology and size. We ended up by understanding that a basic approach was key to develop a successful chemical strategy towards reproducible materials. I then spent almost four years at the Laboratoire de Chimie de la Matière Condensée, Paris, working in Clement Sanchez’s group. The aim was to develop mesoporous titania materials through sol-gel coupled with self-assembled templates. I learned a great deal from the lab’s experience, and again, we analyzed a complex system from very basic sol-gel knowledge, which was a key factor to achieve success in this project. We tackled a complex problem in the synthetic field by developing a rational approach. We focused in understanding the processes that led to small Ti-oxo nanospecies, which in turn co-assembled with an organic template. We used a variety of crossed techniques. I had the great luck to share the laboratory with experienced researchers such as Clément, Jacques Livage, Jean-Pierre Jolivet, Florence Babonneau, Francois Ribot, or Pierre-Antoine Albouy, among others. In addition, I had the pleasure to work with colleagues such as David Grosso or Eduardo Crepaldi, with whom we made a great team. From this experience, I learned that modern advanced materials chemistry is an interdisciplinary subject, and that we should not be afraid of resorting to advanced techniques from the Physics and Materials Science domains to answer relevant scientific questions. After this, I felt strong enough to start my own group, in Argentina, where I returned in 2003, as a staff researcher.
What are the main topics you are working on today?
I am fascinated by the world of nanoporous materials, I just can’t get enough… We are basically developing three lines in the lab: first, how to create oxides with hierarchical pore systems, in the meso- (2-20 nm) and the submicron scale, in order to improve transport properties. To do this, we are combining the supramolecular templating approach with other processes such as controlled phase separation or simultaneous polymerization of an organic phase. Second, we are producing new hybrid mesoporous films, powders or monoliths, which have novel properties due to the synergy between the organic functions and the inorganic framework. This line provides endless possibilities: adding polymers to the mesopores leads to perm-selective membranes, or new catalysts in which the properties can be really tuned by selecting the adequate inorganic and the organic building blocks, and the polymerization degree, for example. Last, but not least, we are focusing in adding metallic nanoparticles to mesoporous thin films; this leads to nanosystems with new electrical and optical properties, for example, photocromics, optoelectronics and new catalysts. We are also incorporating top-down techniques to produce controlled patterns. In summary, we are combining different techniques to produce sol-gel based materials with localized chemical functions that are dependent of the chemical nature, but also in their relative position.
The collaborations you have initiated?
We collaborate with several groups in Argentina and the world. I maintain a very active collaboration with Clément Sanchez’s group, in mesoporous titania films and aerosols, and with Plinio Innocenzi´s lab (University of Sassari) in hierarchically porous films. We are also developing hierarchical monoliths with Rachel Caruso at Melbourne, and we have developed mesoporous aluminophosphates with Venceslav Kaucic’s group in Ljubljana. We hold an active collaboration with Luis Liz-Marzán´s group at Vigo, building metal nanoparticle-mesoporous film composites. We also keep collaborations with experts in several characterization techniques: Heinz Amenitsch for SAXS (Elettra), Matthias Thommes for porosimetry (Quantachrome), Félix Requejo for XAS (INIFTA, La Plata) and others. Within our country, we opened a fruitful collaboration with the University of Buenos Aires (Sara Bilmes, Federico Williams, Ernesto Calvo…), and this was the germ for the formation of several collaboration networks along these years, that helped to build up nanotechnology from bottom-up approaches in Argentina. This included carrying out five Sol-Gel schools that now spread to Latin America. I also maintain collaborations with people from other disciplines. For example, we are working together with Alejandro Faistein and Sara in the optical properties of metal-mesopore composites. And last but not least, we are developing hybrid meso-composites with Omar Azzaroni (INIFTA). Omar is a very solid and inventive chemist from the soft matter area, and it is just a pleasure to work together and create new polymer@mesopore nanocomposites with amazing perm-selective or catalytic properties. This is a very exciting field that is in its very infancy, but has an enormous potential.
Could you let us know the main challenges you foresee for the sol- gel process and the sol-gel materials in the next future?
Sol-gel is a solid pillar for chemical materials processing. In my experience, understanding sol-gel routes is the way to really design complex nanosystems. The way to evolve from serendipity to rational design. For some reason, I think that the community dedicated to nanomaterials has privileged the high impact of fancy systems, without worrying about aspects such as reproducibility, scalability or feasibility. Deep knowledge of the intimate physical-chemical evolution of sol-gel systems, from the reactivity of the molecular precursor to harnessing the processes involved in thermal evolution is just central. There is no other way but understanding if we want to make real nanotechnology. Systematic work has to be done in order to reach this level of understanding. The opportunity for a resurgence of the sol-gel approach is in the near horizon. I believe that we can revisit past works of our community under the new light of the nanomaterials requirements, in order to fully exploit what is behind ultimate control of materials structure and texture at several length scales. A wealth of opportunities in advanced materials design is there, because we “stand in the shoulders of giants”, but we also have had contact with new characterization tools and we have sustained enriching interactions with other communities such as soft matter, photonics or biomimetics.
What is your wish for the sol-gel community?
Nanotechnology-by-design is a great opportunity for us sol-gel scientists. Under this light, we have to keep growing a solid community with strong links and communication among us, trying to incorporate scientists from other fields. Sol-gel is essentially interdisciplinary, and we have the great advantage that we are used to learn, in order to develop a common language. Now is the time to transmit this insight, and to position the community into the heart of modern advanced materials. This is why I took an active part in the formation of human resources and networking, and the development of rational synthesis platforms for complex materials. A whole young generation of brilliant scientists is here to push the limits forward. I think we are lucky to live this moment of excitement.