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NANO-ARCH Report Summary

Project ID: 240111
Funded under: FP7-IDEAS-ERC
Country: Italy

Final Report Summary - NANO-ARCH (Assembly of Colloidal Nanocrystals into Unconventional Types of Nanocomposite Architectures with Advanced Properties)

The major aim of the ERC starting grant project NANO-ARCH was to develop new colloidal nanocrystal (NC) building blocks, identify unconventional approaches to assemble them into two dimensional and three dimensional architectures, to characterize the various properties of these architectures and to lay the foundations for several applications. From the point of view of synthesis, many original approaches to fabricate NCs have been uncovered, and many new types of NCs have been developed: from new plasmonic copper chalcogenides, to branched NCs, new fluorescent quantum dots of reduced toxicity, Pb and Cd-free NCs for photovoltaics, to various types of nano-heterostructures, i.e. NCs made of several domains of different materials connected together epitaxially. New types of assembly concepts have been discovered. For example, self-assembly of nanorods and tetrapod branched NCs exploiting depletion attraction forces has been shown to yield all-NC superstructures or polymer/NCs composite materials that can be used for many different applications, from lasing devices to photovoltaics. One key achievement was the demonstration of how monodisperse colloidal octapod-shaped NCs self-assemble, via van der Waals interactions, in a suitable solution environment, on two sequential levels. First, linear chains of interlocked octapods are formed, and subsequently the chains spontaneously self-assemble into three dimensional superstructures. Remarkably, all the instructions for the hierarchical self-assembly are encoded in the octapod shape. This is a concept that bears many analogies with biological systems. We could also demonstrate that the mechanical strength of these superstructures is improved by welding the constituent NCs together. Self-organization of octapods in two dimensional films on substrates or at the interface between air and polymer was targeted, and a variety of assembly geometries was found, depending on the experimental conditions. These 2D assemblies might find applications in modified super-hydrophobic surfaces. Assembly of nanocrystals in polymers was intensively studied. Octapod chaining in polymers is expected to yield composite materials with improved mechanical properties. However the challenge there is the ability to image these structures deep inside the polymer matrix. This issue is being tackled by scanning x-ray diffraction microscopy coupled with advanced image retrieval algorithms. Partial or complete removal of the organic ligands covering the surface of the NCs can lead to new types of NC films with improved electrical transport and photo-transport properties, with increase in conductance that can be several orders of magnitude higher than that of the pristine films. In the field of catalysis, we discovered that Au-iron oxide NC heterostructures are good catalysts towards the selective carbon monoxide oxidation reaction, thanks to an efficient electron transfer process in the heterostructure, from the oxide domain toward the metal domain, promoted by the epitaxial junction. Assemblies of semiconductor and metal semiconductor structures have been studied intensively, especially for what concerns electron transport properties, which are enhanced when thermal annealing treatments are applied to them prior to measurements. These treatments have been found to promote the formation of metal-semiconductor epitaxial interfaces. Interesting developments came also from the study of cation exchange reactions in NCs and in thermal annealing of NC heterostructures, which have opened new avenues in NC synthesis and processing. Overall the NANO-ARCH project has been up to its promises of generating ground breaking science and of boosting the research of the PI’s group. NANO-ARCH has generated new knowledge that has been protected with patent applications, but also some of the results of the project have laid the foundations for the new, positively evaluated, ERC grant application of the PI (ERC consolidator grant, 2013 call).

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Gabriele Ballero, (Head of Projects Office)
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Record Number: 180558 / Last updated on: 2016-03-09
Information source: SESAM