Lanthanide/transition metal-doped luminescent materials are advanced materials with broad application potential. This type of material achieves control and optimization of luminescence performance by introducing lanthanide/transition metal ions into the host material and utilizing its unique electronic structure and optical properties. Luminescent materials are suitable for optical communication devices, biological imaging, and photodetectors. The combination of lanthanide/transition metals with various matrix materials provides a new platform for creating new chemical and physical properties in materials science and device applications. In this paper, we summarize the latest progress in the research of lanthanide/transition metal-doped luminescent materials and explain their roles in biological imaging, sensing, and optoelectronic applications. It starts with various synthesis techniques and explores how to cleverly incorporate rare earth/transition metals into various matrices, thereby endowing them with unique properties. Then, the advantages and disadvantages of each synthesis technique are discussed. Subsequently, the focus will be on functional strategies and their applications. Finally, strategies for lanthanide/transition metal ion-doped luminescent materials to address challenges are proposed, and insights from each section are summarized.

Responsive photonic crystals, as a class of intelligent photonic materials that can generate optical signals in response to external stimuli including temperature, pH, humidity, electric fields, magnetic fields, and specific molecules, exhibit great application potential in sensing and detection, drug delivery, environmental monitoring, and other fields. This is attributed to their unique tunable photonic band gaps and visual sensing characteristics. In this paper, we systematically review the main preparation methods, including the sol–gel method, photolithography, electrochemical deposition, self-assembly, and 3D printing, and compare the advantages and limitations of each method in terms of key performance indicators, cost, applicable material systems, and scalability for large-scale production. The design strategies of photonic crystals based on different response mechanisms are discussed in detail, revealing the structure–activity relationship between external stimuli and the modulation of photonic band gaps. Meanwhile, the typical applications of responsive photonic crystals in the sensing field are comprehensively summarized, with an emphasis on the latest advances in biomedical sensing, environmental monitoring, and intelligent detection. Finally, in view of the current challenges facing responsive photonic crystals, future development directions are prospected, which provides a reference for promoting the translation of responsive photonic crystals from laboratory research to industrial applications.