Nobel Prize in Chemistry 2023 and a material platform for exciton (photon) manipulation

The Nobel Prize in Chemistry 2023 was awarded to Moungi G. Bawendi, Louis E. Brus, and Aleksey Ekimov for their pioneering work in the "discovery and synthesis of quantum dots". In this paper, we explore the significance of this Nobel Prize to the discipline of chemistry from the perspective of the development history and the future of quantum dots. We also discuss the unique opportunities for the development of chemistry, especially synthetic chemistry, triggered by this type of "atypical" chemical synthesis targets. Exciton (electron-hole pair) is a key element in quantum dots, and the ability to control the behavior of excitons forms the basis for many applications of quantum dots. Unlike conventional synthetic chemistry goals, which focus on the ground state properties like composition, morphology and size, the ultimate goal of quantum dot synthetic chemistry is to control excitons generated by excitation in semiconductor nanocrystals. Meanwhile, it should be noted that the ground state properties of quantum dots do not always have one-to-one correspondences with the excited states (i.e. various types of excitonic states). Furthermore, unlike the Wannier excitons bounded by weak Coulomb interaction in bulk semiconductors, which can hardly exist stably, the excitons generated by excitation in semiconductor nanocrystals are dynamic excitons confined by the crystal boundaries. The electrons and holes of the confined dynamic excitons behave as "particle-in-a-box", and the kinetic energy is quantized, resulting in a generalized quantum confinement effect. This effect makes the electronic energy levels show strong size dependence, causing various properties of quantum dots, such as photoluminescence peak position, redox potential and charge transfer dynamics to be determined not only by their composition but also by their size. Based on their unique properties, dynamic excitons in semiconductor nanocrystals can be utilized as an effective material platform for manipulating photon annihilation, generation, and transformation. With the continuous progress of synthetic chemistry, mono-dispersed high-quality quantum dots were synthesized and the synthesis route has been developed from being dangerous and expensive to environment-friendly and scalable. It promotes the vigorous development of quantum dots in both academy and industry, and proves the diversity of synthetic chemistry of inorganic materials can be as rich as that of organic chemistry: Relying on a limited number of elements, massive inorganic nanomaterials with various properties can be fabricated through the control of the number of primitives and the way they are assembled, serving energy, communication, medicine and many other fields.