Transparent Silica Aerogels: Optical and Chemical Design, Controlled Synthesis, and Emerging Applications

Transparent silica aerogel, serving as one typical porous and transparent material, possesses various unique features (e. g., large amounts of pores and interfaces, super‐lightweight, super thermal insulation, low refractive index similar to gas), and it has attracted great attention in the fields of science, technology, engineering, art, and others. Transparency is one important evaluation index of transparent silica aerogel, and it was influenced by various factors such as raw materials, sol‐gel reactions, phase separation, and drying methods. The structure design and fabrication of transparent silica aerogel is one huge and fine engineering. In this review, the optical/chemical guidance and design for the preparation of transparent silica aerogels are discussed, and typical applications, such as Cherenkov detectors, solar energy collection, lighting systems, and transparent fabric, were also discussed. Finally, a future outlook on the opportunities and challenges of transparent silica aerogels was proposed. Transparent silica aerogels play important roles in many fields owing to its unique structure and properties. This review encompasses the optical and chemical design of these aerogels along with various synthetic factors that influence transparency. Discussion on different configurations, physical properties and emerging applications are also provided. Finally, an outlook on the opportunities and challenges of these aerogels is proposed.