Final Report Summary - GSOMEN (Growth and Supra-Organization of Transition and Noble Metal Nanoclusters)
Metal nanoclusters are self-assembled particles less than 10-100 nm in diameter. Two classes of metal nanoclusters have been selected as the object of the 'Growth and supra-organization of transition and noble metal nanoclusters' (GSOMEN) project: supported on oxide surfaces, as obtained by metal vapour deposition under UHV coated by a layer of surfactants, as obtained in solution, and subsequently deposited an oxide surfaces.
These materials possess very appealing potential applications, which however still wait to be fully exploited because of the lack of knowledge, and hence lack of control, on their synthesis (the self-assembling and supra-organization processes). The aim of GSOMEN was to produce this knowledge by combining the most advanced techniques in the experimental synthesis and characterisation with the theoretical simulation of the structure, growth and properties of metal nanoclusters. The recent advances in these fields, at the synthetical level (also through the use of external fields), at the characterisation level (e.g. synchrotron-related techniques), at the simulation level (advances in computer hardware, development of accelerated techniques in the study of dynamical processes), if properly coordinated, make this goal feasible, thus allowing one to achieve control and orientation on the fabrication of these materials. Information on the basic metal-support, metal-ligand and nanoparticle-nanoparticle interactions is derived from the interplay of calibrated experiments and first-principle calculations, and is used to build up appropriate inter-particle potentials. These potentials are utilised in molecular dynamics and kinetic Monte Carlo simulations of the various growth processes under realistic conditions, from which a direct comparison with actual growth experiments is immediately possible. The concluding part of the project is also dedicated to the study of general structure / property relationships, to bridge the link with scientific and technological applications.
The basic processes of growth have been thoroughly investigated (both experimentally and via theoretical simulations) as a function of temperature and synthetic conditions: diffusion of single atoms or small clusters in the case of bare metal clusters vs. ligand desorbing (with the presence of ancillary species such as reducing agents) in the case of solvated clusters, aggregation, nucleation and final possible agglomeration. The structure of the resulting particles has been elucidated as a function of their size, employing proper experimental and theoretical simulation tools. In the case of bare metal clusters, the interaction with defects on the oxide surfaces that act as nucleation centres and its influence on the structural evolution of the clusters has been explored, opening the way to the creation of surface magic clusters.
Reactive channels (e.g. interfacial reactivity) have also been considered as a function of the choice of the specific metal-oxide or metal-ligand system. The novel phenomena that occur when the dimension of the oxide layer shrink to the nanoscale have also been pioneered (i.e. considering ultra-thin oxide films grown on metal supports as substrates for the deposition), such as charge transfer effects between the nanoclusters and the underlying metal support. This was directly linked to the theme of surface nanopatterning, as many of these novel ultra-thin oxide films exhibit reproducible patterns at nanometre lengths, and these patterns have been exploited to obtain regular arrays of nearly monodisperse metal particles.
Several nanopatterning techniques have been explored: the creation of networks of interfacial dislocations, Moiré patterns, naturally nanostructured oxide surfaces, and nanofabrication and nanosculpting tools. The organisation of these particles into supra-lattices has been studied in detail, and the conditions that allow the synthesis of extremely regular arrangements have been discovered. The catalytic, optical and magnetic properties of the single metal particles and those arising from their collective behaviour have finally been investigated and in many cases fully rationalised.
To pursue this research, the development of novel characterisation tools and protocols at both the experimental and theoretical levels has been essential. This has allowed the groups involved in GSOMEN to obtain realistic images of a variety of systems with disparate sizes, shapes and morphologies, ranging from single or few-atom species to mesoscale assemblies of particles composed of thousand of atoms. The results have been published in a number of publications on high-impact scientific journals (the complete list is included in the project web site). The synthesis, characterisation and simulation protocols are available upon request to the scientific community.
As most dissemination activities generated within GSOMEN are either publications on top-rank scientific journals or presentations at international conferences, attached is the list of publications and presentations divided according to each team leader of each research unit. The partner involved will thus be immediately apparent; the type of audience will be research; the countries addresses will be potentially all, as international journals and conferences are invariably considered; as for the size of audience, we report the impact factor for publications. The medium (which journal or conference) where to present the research results has been chosen with the goal of achieving the largest dissemination impact, also following the suggestions of the DCC Committee.
Additionally, a European patent has been applied by CNR-ICCOM and a connected spin-off initiative is in an advanced stage, as described below under the appropriate item.
Along the direction of technological applications, it is foreseen that the partners will soon publish results or summary of the project on industry-related journals and magazines. Actions have already been taken to this effect.
These materials possess very appealing potential applications, which however still wait to be fully exploited because of the lack of knowledge, and hence lack of control, on their synthesis (the self-assembling and supra-organization processes). The aim of GSOMEN was to produce this knowledge by combining the most advanced techniques in the experimental synthesis and characterisation with the theoretical simulation of the structure, growth and properties of metal nanoclusters. The recent advances in these fields, at the synthetical level (also through the use of external fields), at the characterisation level (e.g. synchrotron-related techniques), at the simulation level (advances in computer hardware, development of accelerated techniques in the study of dynamical processes), if properly coordinated, make this goal feasible, thus allowing one to achieve control and orientation on the fabrication of these materials. Information on the basic metal-support, metal-ligand and nanoparticle-nanoparticle interactions is derived from the interplay of calibrated experiments and first-principle calculations, and is used to build up appropriate inter-particle potentials. These potentials are utilised in molecular dynamics and kinetic Monte Carlo simulations of the various growth processes under realistic conditions, from which a direct comparison with actual growth experiments is immediately possible. The concluding part of the project is also dedicated to the study of general structure / property relationships, to bridge the link with scientific and technological applications.
The basic processes of growth have been thoroughly investigated (both experimentally and via theoretical simulations) as a function of temperature and synthetic conditions: diffusion of single atoms or small clusters in the case of bare metal clusters vs. ligand desorbing (with the presence of ancillary species such as reducing agents) in the case of solvated clusters, aggregation, nucleation and final possible agglomeration. The structure of the resulting particles has been elucidated as a function of their size, employing proper experimental and theoretical simulation tools. In the case of bare metal clusters, the interaction with defects on the oxide surfaces that act as nucleation centres and its influence on the structural evolution of the clusters has been explored, opening the way to the creation of surface magic clusters.
Reactive channels (e.g. interfacial reactivity) have also been considered as a function of the choice of the specific metal-oxide or metal-ligand system. The novel phenomena that occur when the dimension of the oxide layer shrink to the nanoscale have also been pioneered (i.e. considering ultra-thin oxide films grown on metal supports as substrates for the deposition), such as charge transfer effects between the nanoclusters and the underlying metal support. This was directly linked to the theme of surface nanopatterning, as many of these novel ultra-thin oxide films exhibit reproducible patterns at nanometre lengths, and these patterns have been exploited to obtain regular arrays of nearly monodisperse metal particles.
Several nanopatterning techniques have been explored: the creation of networks of interfacial dislocations, Moiré patterns, naturally nanostructured oxide surfaces, and nanofabrication and nanosculpting tools. The organisation of these particles into supra-lattices has been studied in detail, and the conditions that allow the synthesis of extremely regular arrangements have been discovered. The catalytic, optical and magnetic properties of the single metal particles and those arising from their collective behaviour have finally been investigated and in many cases fully rationalised.
To pursue this research, the development of novel characterisation tools and protocols at both the experimental and theoretical levels has been essential. This has allowed the groups involved in GSOMEN to obtain realistic images of a variety of systems with disparate sizes, shapes and morphologies, ranging from single or few-atom species to mesoscale assemblies of particles composed of thousand of atoms. The results have been published in a number of publications on high-impact scientific journals (the complete list is included in the project web site). The synthesis, characterisation and simulation protocols are available upon request to the scientific community.
As most dissemination activities generated within GSOMEN are either publications on top-rank scientific journals or presentations at international conferences, attached is the list of publications and presentations divided according to each team leader of each research unit. The partner involved will thus be immediately apparent; the type of audience will be research; the countries addresses will be potentially all, as international journals and conferences are invariably considered; as for the size of audience, we report the impact factor for publications. The medium (which journal or conference) where to present the research results has been chosen with the goal of achieving the largest dissemination impact, also following the suggestions of the DCC Committee.
Additionally, a European patent has been applied by CNR-ICCOM and a connected spin-off initiative is in an advanced stage, as described below under the appropriate item.
Along the direction of technological applications, it is foreseen that the partners will soon publish results or summary of the project on industry-related journals and magazines. Actions have already been taken to this effect.
