Abstract:

The Nobel Prize in Chemistry 2023 recognises the discovery and synthesis of nanometresised semiconductor crystals, the properties of which are determined by quantum size effects [1]. When 2023 Laureates, Alexei Ekimov, Louis Brus and Moungi Bawendi carried out their first work on quantum dots over 40 years ago, none of them anticipated the enormous impact these tiny crystals would have on our daly life. Their work [2-4], alongside the others, was part of the birth of nanoscience and nanotechnology. The name, quantum dots was given by Mark Reed in 1986, and marks nanoparticles so small that their physical size determines the quantum mechanical states of the material’s charge carriers. Quantum dots constitute a new class of materials that is neither molecular nor bulk. They have the same structure and atomic composition as bulk materials, but their properties can be tuned using a single parameter, the particle’s size. Changing the size of a quantum dot changes its properties, in particular its fluorescence, meaning that they can be tuned to different coloyrs. For example, the smallest dots will emit more shorter-wavelength blue light than longer-wavelength red light. The principle of quantum confinement, used to describe the QD, also referred to as the ‘particle in-a-box’ problem, was theoretically proposed in the 1930s by H. Fröhlich [5]. He has shown that particles when become extremely small there is less and less “space” for electrons to reside, hence electrons are squeezed together forming the discrete spectra in order to find the space for themselves. It is less known that Institute Vinča played the pioneering role in the discovery of quantum dots. In 1986 some of the most fundamental quantum properties were discovered there, like, light matter interaction in QD, ionisation potentials of QD, and redox potentials of QD, all as they change with the QD size [6]. Along the overview of the historical context, I will review my contribution to the current QD technology: (1) luminescence solar concentrates, (2) utilisation of QD as very efficient energy conversion sources for high efficiency solar cells with the intermediate band, (3) physics of the “Russian Doll” QD and its multi-excitonic properties, and (4) QD as single photon sources in quantum information processes [7]. And while quantum dots already have an array of applications – from QLED television displays to medical imaging – we are still just scratching the surface of their full potential [8].

References

1. https://www.nobelprize.org/prizes/chemistry/2023/
2. A. I. Ekimov, A. A. Onushchenko, V. Tsekhomskii, Sov. Glass Phys. Chem. 6, 511 (1980) (in Russian).
3. L. E. Brus, J. Chem. Phys. 79, 5566 (1983).
4. C. B. Murray, D. J. Norris, M. G. Bawendi, J. Am. Chem. Soc. 115, 8706 (1993).
5. H. Frölich, Physica IV 5, 406 (1937).
6. J. M. Nedeljković, M. T. Nenadović, O. Micić, A. J. Nozik, J. Phys. Chem. 90, 12 (1986).
7. S. Tomić, Phys. Rev. B 82, 195321 (2010).
8. S. Tomić, Elementi 35, 10 (2024) (in Serbian).