Colloidal photonic crystal (PC)-based anti-counterfeiting materials have been widely studied due to their inimitable structural colors and tunable photonic band gaps (PBGs) as well as their convenient identification methods. In this review, we summarize recent developments of colloidal PCs in the field of anti-counterfeiting from aspects of security strategies, design, and fabrication principles, and identification means. Firstly, an overview of the strategies for constructing PC anti-counterfeiting materials composed of variable color PC patterns, invisible PC prints, and several other PC anti-counterfeiting materials is presented. Then, the synthesis methods, working principles, security level, and specific identification means of these three types of PC materials are discussed in detail. Finally, the summary of strengths and challenges, as well as development prospects in the attractive research field, are presented.

Due to the extreme reflectivity requirements of radiative cooling coatings, these materials often employ ceramic nanoparticles such as TiO₂ due to their high refractive index and scattering efficiency. However, the bandgap of TiO₂ (3.2 eV) is lower than the energy of the most energetic solar light, leading to significant absorption in the UV range (0.25–0.4 μm) and subsequent oxidation aging and yellowing of particles and/or organic binders. To overcome the conflict between high reflective efficiency and UV durability, formulations using high-bandgap materials can be used despite their lower refractive index. In this work, we describe an optimized PRC-Al₂O₃ coating by adjusting the ratio of low refractive index alumina particles to sodium methylsilicate adhesive. The PRC-Al₂O₃ exhibits a high solar reflectance above 0.96 and a high mid-infrared emissivity of 0.91, enabling it to achieve a maximum theoretical cooling power of 109 W m⁻². Following continuous UV irradiation with a power of 0.7 kW m⁻² for 72 hours, only a marginal 0.2% decline in solar reflectance compared to the unaged coatings. The resulting anti-aging cooling paint is scalable and can be spray-coated onto outdoor structures and containers, providing durable radiative cooling towards real-world applications.