Nanocrystal-in-glass composite (NGC): A powerful pathway from nanocrystals to advanced optical materials

Transparent nanocrystal-in-glass composite (NGC) comprising functional nanocrystals in transparent inorganic glass creates a new bridging from nano/microscale structure to multifunctional macroscale devices with advanced optical properties. In this review, we outline the key scientific advances in the development of transparent NGC, from the perspectives of fundamental design principles, new synthetic strategies and their substantial progress in advanced optical applications. To generate desired transparent NGC materials, we start with the design principles to describe the transformation process from nano/micro to macro, providing an in-depth insight into the structure-property relationship and the underlying problem in particle binding and network reconstruction in the composite materials. Emerging techniques based on the "top-down" or "bottom-up" strategies have advanced the ability to fabricate nanocomposites with controllable composition, phases, fraction, morphology, spatial distribution, and orientation. We also provide an overview of recent advances in optical applications, including solid-state lighting, high-performance lasers, optical data storage, and fluorescence sensing. The remaining scientific challenges, for example, the important trade-off between functional performance and chemical compatibility when bridging the nanocrystals to transparent NGC and their devices, are also highlighted. Addressing these questions will provide a clear pathway to design and manufacture multifunctional inorganic materials based on these NGC materials.