Low-toxic quantum dots with modulated light emission in the near infrared region

• Applicant: Dr. Vladimir Lesnyak
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 326707061

Aim: 1) to develop low-toxic colloidal copper chalcogenide based quantum dots (QDs) with tunable size, composition and shape, and exhibiting photoluminescence (PL) extended over the whole near infrared (NIR) spectral region (700-2500 nm) with high quantum yields reaching 80%; 2) to design hybrid PL-localized surface plasmon resonance (LSPR) systems based on these QDs and plasmonic copper chalcogenide nanocrystals (NCs) with controllable exciton dynamics. Motivation: whilst the visible range is completely covered by various QDs possessing quite efficient light absorption and fluorescence characteristics, the NIR active materials are limited by PbA (A = S, Se, Te), InAs, Cd3P2, CdHgTe, and HgTe. As all these compounds contain toxic elements, their potential technological applications face serious restrictions. A valuable alternative is copper chalcogenide-based ternary and quaternary QDs, such as CuIn(Zn)S(Se). However, the range of light absorption/emission of these QDs is limited to ca. 1200 nm, i.e. the currently emerging CuInS(Se) QDs, fluorescing farther in the NIR are not developed yet. This is exactly where the present project aims to bring a major contribution. Furthermore, these low-toxic QDs exhibit complex exciton dynamics which can be used as an additional handle to tune their photophysical properties. One of the means for this tuning is the interaction of excitons formed in QDs with electromagnetic field generated by materials exhibiting a strong LSPR. This coupling has been demonstrated to result either in the PL quenching or enhancement. Although this interaction has already been investigated in the visible region, it remains still unexplored for the NIR spectral range. Such investigation of the coupling of NIR luminescing QDs and appropriate NIR plasmonic nanomaterials constitutes the second major part of the project. Objectives: to develop new synthetic approaches to CuIn(Zn)Se(Te) QDs, based on cation exchange reactions; to enhance their stability and improve their optical properties via ZnS or ZnSe shelling; to design hybrid structures combining the NIR PL QDs with NIR plasmonic copper chalcogenide NCs with well controlled distance between them; to study the interactions between excitons and plasmons in the NIR region aiming at a PL enhancement and acceleration of the exciton recombination. Implementation: work program of the project is divided into four work packages relative to each objective. Each of them includes detailed tasks precisely assigned to two doctoral researchers. Potential Impact: innovative optoelectronic materials and opestructures with tunable photophysical properties, which will be developed, are very promising candidates for applications in bio-imaging, multiphoton imaging, fluorescence-lifetime imaging microscopy, photovoltaics, nanophotonics, solar concentrators, and sensing.

• DFG Programme: Research Grants