Given the deficit of inexpensive and luminescent materials from compounds containing abundant elements as for instance copper, this ANR-DFG SUPRALUM project targets the preparation and the study of the multifunctional luminescence properties of a large series of new discrete and polymeric polymetallic Cu(I) based supramolecular assemblies. These new inexpensive and stable derivatives will present unprecedented architectures that include enhanced solid-state luminescence properties, which will establish them as a very appealing source of new multifunctional molecular materials incorporating both lighting and sensor applications. A combined experimental and computational approach will be performed that will unify the fundamental understanding and application of coordination and supramolecular chemistry, main-group elements chemistry, photophysics and material sciences. Innovative coordination-driven supramolecular synthetic routes already mastered by the consortium members will be adapted to new straightforward high-yield syntheses of polymetallic Cu(I) derivatives. For the first time, the specific and complementary synthetic tools and characterisation skills available in both the German and the French group (such as the coordination-driven supramolecular chemistry adapted to flexible Cu(I) pre-assembled precursors as well as the innovative use of polytopic assembling main group (P, As, Sb, Bi) ligand complexes and of fully aliphatic and flexible polytopic linkers) will be combined in order to specifically introduce luminescence properties within the targeted polymetallic supramolecular scaffolds, conferring a significant level of novelties to this project. State-of-the-art photophysical investigations and calculations will be executed to highlight luminescence properties and rationalise electronic processes that are inherent in the synthesised new materials. It will thus be possible to execute an unprecedentedly thorough study of the structure-property relationships of such luminescent supramolecular compounds, inducing a significant growth of the family of luminescent Cu(I) derivatives to establish an emerging and promising class of emissive molecular materials. Very encouraging first results have been obtained by both the German and French groups that are the basis of their cooperation, providing substantial guarantees that this project will generate new scientific knowledge and innovative classes of environmentally friendly, multifunctional luminescent materials that are highly relevant in the line of sustainable development.

The optical properties of emitting nanoparticles such as quantum dots (QD) or NV centers in nanodiamonds (ND) have been extensively studied in solution or in vivo, isolated on dielectric or plasmonic substrates, coupled to metallic colloids or even attached to near-field scanning probes. Yet, optical studies have been performed with macroscopic or diffraction limited techniques. One noticeable exception is the cathodoluminescence (CL) study of isolated QD in the 1990s and recently of isolated nanodiamonds. The HYBNAP project proposes to study hybrid structures made by coupling gold nanoparticles with well-defined plasmonic modal properties to emitting nanoparticles with 1-nm probes of electron energy-loss spectroscopy (EELS), CL and photon scanning tunneling microscopy (PSTM) to locally excite and characterize their optical response. The project dedicates particular attention to build the hybrid emitter-metal structure with nanometer controlled geometries by combining colloidal synthesis and self-assembly with advanced templating effects of sub-10 nm patterned substrates structures. Theoretical modelling and numerical simulations is implemented to interpret the experimental data. In order to carry out this widely interdisciplinary research program and reach an unprecedented spatial precision combined with spectral insight, a flexible research platform is created for investigating and tuning nano-optical properties of hybrid emitter / metal nanoplasmonic systems. The work is realized by the joint force of a strong team that combines expertise in colloidal chemistry and self-assembly (CEMES Toulouse & SCR Rennes, Fr), ultimate nanofabrication (SUTD Singapore), nanoplasmonics modelling and simulations (IHPC Singapore & CEMES) and nano-optical characterization (IMRE Singapore & CEMES). The HybNaP partners first focus on acquiring, with nanometer precision, the mapping of surface plasmon (SP) modal distributions in a series of nanoparticles, 1D and 2D crystalline structures produced by CEMES and SCR by using TEM-based electron beams at IMRE. The results are benchmarked to linear and non-linear optical imaging that have been recently shown to probe the partial SP local density of states (LDOS) and confronted to theoretical models associated to numerical simulation tools based on finite element or 3D-Green Dyadic methods. Preliminary work has by IMRE and CEMES has led to a 2015 publication in Nature Mater. IMRE is one of the very few places worldwide where combined EELS / CL measurements are possible. CL is recorded to allow correlating local excitation and photon emission. In parallel, low energy electron excitation with similarly spatial confinement is developed at CEMES by recording luminescence under STM tip excitation. Data interpretation will be supported by STEM measurements and IHPC's modeling of SP emission spectra from a tunnel junction. Meanwhile, metal-emitter hybrid structures composed of gold colloids and QD or ND will be synthesized by CEMES and SCR and coupled by using molecular coupling approaches. Protocols to restrict the assembly to dimers and small oligomers are targeted. Alternatively, a colloidal epitaxy approach in which quantum nanorods are used as templates to grow metallic nanoparticles at the tips is explored. Hybrid structures of increasing complexity are obtained by doping plasmonic nanoparticle networks with QD or ND. Finally, hybrid plasmon-emitter with improved topology will be produced by combining colloidal chemistry with high resolution electron-beam lithography. Mix & matching will allow to tune the relative location of the emitter and the nodes of the SP modal distribution and to place it where the SP-LDOS is intense. Structures will be made that can be measured both in the near- and far-field. Simulation routines guide the design of efficient hybrid structures able to excite dark plasmon modes that are otherwise inaccessible, leading to hybrid materials with unique, tunable optical properties.