Progetto CANDL2

CANDL2: CArbon NanoDots for Light-emitting materials and Lasing applications _ PRIN2017

Research project title CANDL²: CArbon NanoDots for Light-emitting materials and Lasing applications
Principal Investigator                                     Prof. Luca Malfatti
Duration                      36 months
Main ERC field                       PE - Physical Sciences and Engineering
ERC subfields                           PE8_8 Materials engineering (metals, ceramics, polymers, composites, etc.);PE3_10 Nanophysics: nanoelectronics, nanophotonics, nanomagnetism, nanoelectromechanics, etc., PE5_6 New materials: oxides, alloys, composite, organic-inorganic hybrid, nanoparticles
Research Units Università degli Studi di Sassari, Università degli Studi di Cagliari, Università degli Studi di Palermo, Consiglio Nazionale delle ricerche – Area della Ricerca di Bari






Recently, a lot of effort has been made to synthesize highly luminescent and nonhazardous nanomaterials that can effectively represent an alternative to semiconductor quantum dots or rare earth based
nanoparticles, in order to reduce the use of toxic heavy metals (Cd, Sb, Pb, etc.) or La, Er, Ga, etc., in accordance with the Horizon 2020 priorities. Nowadays the fluorescent quantum yields of carbon dots (CDs) in the green/blue range is almost competitive to those of semiconductor nanocrystals, envisaging the use of these nanoparticles as a non-toxic and low-cost substitute of rare earth- or heavy metalbased alternatives, currently used in optical technologies. Despite these promising results, however, the control on the CDs structure and photoluminescence is far to be optimized. Several important issues such as the inhomogeneity at the chemical and spectroscopic level, the poor reproducibility of the synthesis, and the limited quantum yield, especially in the red range, need to be tackled before this new class of light-emitter materials can be technologically harnessed to its full potential. In addition, while the study of CDs-related nanocomposites is a crucial step for industrial applications, the interactions between CDs and hosting matrix, both polymeric or inorganic, are largely unexplored.
The CANDL² project aims to fill the gap between fundamental knowledge and technological development of such nano-objects to developing CDs based nanocomposites that can be effective for solid-state lighting and lasing applications.
To realize its ambitious goals, CANDL² puts together a team of recognized experts in CD synthesis methods, quanto-mechanic and atomistic simulations, chemical-physical characterization and incorporation in sol gel matrixes, all based in the South of Italy, which are already involved in a large network of international collaborations focused on this topic.
The first target of the project is the design of luminescent CDs showing high quantum yield, narrow emission bandwidth and tunable chromaticity. To fulfill this ambitious aims we will make use of cutting-edge techniques in the synthesis of carbon dots, using both chemical and physical processing, in order to tune their physical chemical properties, including their surface chemistry. In particular, the emission will be tuned to achieve a variety of colours and these will be blended to compose the complete palette of tints in the visible range. Alternatively, proper synthetic procedures will be optimized to provide white emission in single carbon dots.
Up to now, most of studies dealt with CDs in solutions while only few examples report CDs dispersed into polymeric or inorganic matrices for solid-state applications. The second target of the CANDL² project is rationalizing the outstanding optical performances of CDs in solutions and transferring to CD-based solid-state systems for lighting and lasing applications. Based on our recent results, sol-gel chemistry demonstrated to be effective in introducing carbon-based nanostructures in mechanically stable matrices for obtaining highly performing optical materials. One-pot synthesis and post-functionalization approach will be used to prepare highly CD-loaded matrices made of hybrid organic-inorganic or pure inorganic materials. The emission will be also maximized through a coupling in the sol gel matrices with suitably synthesized plasmonic nanoparticles, capable of increasing the photoluminescence efficiency through metal enhanced fluorescence (MEF). The overall properties of the nanocomposites, colour rendering and temperature, thermal and chemical stability, will be tuned using the wide flexibility offered by the sol-gel approach, towards LED applications.
Besides lighting, the project also aims to produce lasing from CDs based nanocomposites. Despite some recent achievements in solution phase, this is still a challenging task, as the percentage of CDs involved in a lasing process is limited by the strong inhomogeneity of the nanoparticles. In fact, CDs display widely variable chemical structures, sizes and morphologies, associated to equally variable optical responses. Efficient lasing would be only achieved in monoliths with large volumes and high optical qualities, incorporating high concentrations of CDs with well-controlled and homogeneous optical characteristics. The use of sol-gel chemistry, with a careful design of the chemical precursors involved in the synthesis and a proper surface functionalization of the nanoparticles is expected to provide strong improvements in the possibility of incorporating high concentrations of luminescent CDs without causing aggregation.
The outcomes of the CANDL² are expected to disclose a new generation of environmental-friendly light-emitting materials with a wide range of colour tuning.