Quantum dots (QDs) are semiconductor crystal structures of diameters less than ten nanometers. They exhibit excellent optical properties, such as bright luminescence and narrow emission band, which make them suitable for a number of applications, i.e. optoelectronics, sensing, photovoltaics and bioimaging. Over the recent two decades, special attention has been paid to cadmium-based QDs. However, their negative biological and environmental impact incessantly raise doubts regarding their potential practical and large-scale applications. In this regard, ZnO nanocrystals (ZnO NCs) have enjoyed a particular attention due to their biocompatibility as well as their intrinsic physical and chemical properties. The sol-gel process has played a key role in advancing research on nanocrystalline ZnO. However, the traditional inorganic sol-gel method has several drawbacks, which extremely limit the QDs' further usage. An entirely new ZnO QDs' synthetic approach has been developed by the Lewinski group. The novel organometallic one-pot two-step strategy provides nanostructures with a well-passivated surface, characterized by high quality and stability, as well as remarkable physicochemical properties. For example, the unusual character of ZnO QDs derived from the organometallic method was substantiated by their ultra-long photoluminescence lifetime. Moreover, the unique character of the inorganic-organic interface of ZnO QDs' derived from the organometallic approach and their vast processability were substantiated by the free-standing, self-supporting films the ZnO QDs formed at the air/water interface, while retaining their luminescent properties. In conclusion, the new synthetic procedure paves the way for colloidal semiconductor quantum-sized crystals as a new class of extraordinary processable building blocks for the next generation of hybrid devices.
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