The SA-NANO STREP proposes to advance self assembly of state of the art shape-controlled nanocrystals to a high level
of complexity and versatility that will enable in the long term a new class of functional devices that can be mass-produced in parallel
fashion. There is already a remarkable technological interest in nanocrystals, and this interest will vastly grow once viable approaches
to produce ordered nanocrystal assemblies will be clearly identified as we target here. Colloidal nanocrystals made of semiconductor materials,
the focus of our work, can be fabricated with high-efficiency emission from UV to IR wavelengths.
So far, nanocrystals have been exploited in areas ranging from genomic and proteomic bio-assays, cell-staining and high-throughput screening,
applications in which they serve as fluorescence markers. This directly demonstrates the applicative potential of fundamental developments
in this area. Unfortunately, the commercialization of these technologies has so far been carried out outside Europe, primarily in the USA.
Yet, the field of nanotechnology applications stemming from nanocrystals is still at its infancy. For example, additional applications have
been proposed for nanocrystal materials in LEDs, lasers, optical switches, photovoltaics, data storage devices, catalysis, and drug delivery
which have not been commercialized so far.
Moreover, European research groups, and in particular the members of the present submission, are
at the forefront of the nanoscience activities involving nanocrystals. We therefore strongly believe that by proper allocation of resources
it is possible to bring the new scientific knowledge developed in this project to industrial applications in broad fields and on a rapid timescale.
We envision the strategic impact of the proposed project on the future technological and economical development of Europe in several directions.
We will discover and develop new principles, concepts and methods to self assemble shape-controlled nanocrystals. These discoveries are going
to be the key for developments of future nanocrystal-based devices. We intend to develop intellectual property related to the fundamental
processes developed in this project. Since these processes lie at the foundation of self assembly of shape-controlled nanocrystals, this will
grant a very powerful basis for future commercialization in broad areas. To this end, we allow ourselves in the following to look ahead onto
the next decade projecting some potential applications that will strongly depend on the ability to self assemble nanocrystals.
These applications will span diverse fields, from novel electronic, paper-like displays, to revolutionary new concepts for drug-delivery,
to new optical devices, to solar cells, and in catalysis.
In materials science, composites of nanocrystals with polymers can provide materials that allow the
processability and chemical tailorability of polymeric materials (i.e. plastics) but have all of the most desirable
characteristics of traditional inorganic semiconductors. Even more important, these characteristics can be tuned independently,
enabling the development of unique materials and capabilities that presently do not exist. This technology can lead, for example,
to LED screens that consist of flexible foils and could be folded or rolled up like a newspaper. Such devices potentially could
substitute colored light bulbs in novel lighting applications where aside from the new feature of flexibility, the low-power
needs would reduce the power consumption significantly. An even more elaborate application of such new media can evolve into
an electronic paper-like display.
In the biomedical research, three-dimensional assemblies of shape-controlled nanocrystals with different functionalities such as groupings of
fluorescent and magnetic nanocrystals, both of which will be targeted here, bearing various biomolecules attached to them, can open new fields
in the diagnosis and cure of diseases. One can imagine using them to deliver specific drugs at well-defined locations in a living body.
External fields can be used, for instance, to direct these assemblies by interaction with their magnetic portion, while tracking will be
possible via their fluorescent portion. Biomolecules attached to nanocrystals could be used to selectively target specific cells (i.e. cancer tissues).
Then, once on/in the cell, another metal portion of the nanocrystal (such as a gold section) could be selectively heated by applying an external
RF field, thus killing only the cancer cells. Once they have accomplished their task, nanocrystals could then be re-concentrated by magnetic
fields in another region of the body and re-extracted. Also medical sensors that are implemented into normal clothing can be envisioned,
thus providing a convenient way to monitor the functionality of the human body during motion.
Additional applications are in the area of wavelength-selectable optical devices. Potentially, nanocrystal lasers can be tuned to arbitrary
wavelengths from the UV to the IR. Although we are still in the beginning of understanding the optical-gain properties of nanocrystals, it is already clear that nanorods have demonstrated advantages over nanocrystals in prototype lasing devices (lower lasing threshold, lower rate of Auger recombination). Enhanced performance is expected from the realization of ordered assemblies of rods. Applications in this area can potentially range from high-brightness polarized displays, lasers, and waveguides. In particular, the ability to fabricate shape-controlled nanocrystals in the important near-IR telecommunications wavelengths (1400-1700nm), and the ability to incorporate these materials as composites into arbitrarily configuration (for instance in a preferential geometry as part of a waveguide device on a Si substrate), makes them interesting for expanding the bandwidth needs of the telecommunications industry.
Tetrapods, because of their unique shape (which causes them to self-align on a substrate) and of their
electronic structure, are being exploited as components in thin-film photovoltaic devices where they are incorporated in a
host matrix made of a conductive polymer. Low-cost photovoltaics is today regarded as one of the promising applications of nanocrystals.
The rapid evolution of this technology will be of tremendous benefit for the isolated communities in poor and underdeveloped countries,
especially in tropical areas, in which the availability of low power, not to mention environmental friendly electricity, at low cost,
will provide such communities reliable access to some domestic power needs, and to wireless communication services (internet, telephones). Needless to say those photovoltaic devices have also tremendous advantages with respect to the environmental impact in energy conversion. Compared to other energy sources, solar energy is a very clean and green approach.
Ordered assemblies of shape-controlled nanocrystals will also be useful in catalysis.
Shape-controlled nanocrystals are grown such that certain
crystallographic facets have much larger surface area than others. In addition, such facets might have higher catalytic activity towards the
photodegradation of some pollutant species. The possibility of growing composite nanocrystals, such as the metal-tipped nanorods and tetrapods
envisaged in this proposal, will enhance this activity even further. In these materials separate redox processes will likely occur in different
regions of the nanocrystal, thus vastly enhancing the catalytic activity, as has been demonstrated in metal-patched TiO2 nanocrystals. Networks
of tetrapods (or of other three-dimensional shaped nanocrystals), either free-standing or supported on a surface, could then serve as robust,
re-usable, highly porous media for the rapid degradation of pollutants, both in the liquid and in the gas phase.