Engineering Multi-Wavelength Luminescent Photonic Crystals through Eutectic Crystallization for Next-Generation Authentication

• Applicant: Professor Dr. Alexander Kühne
• Subject Area: Polymer Materials ; Synthesis and Properties of Functional Materials
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 566871760

The development of new anti-counterfeiting materials is of paramount importance in various industries, including finance, pharmaceuticals, electronics, and luxury goods. As counterfeiting techniques become increasingly sophisticated, conventional security measures are often insufficient to prevent fraud and ensure authenticity. Innovative anti-counterfeiting materials enhance security by incorporating advanced optical, chemical, or structural properties that are difficult to replicate. These materials not only protect brands and intellectual property but also safeguard consumers from fraudulent products that may pose health and safety risks. Moreover, the integration of cutting-edge technologies, such as photonic structures, smart inks, or nano-engineered materials, can provide dynamic and interactive authentication features, improving real-time verification. In an era where digital and physical security threats continue to evolve, the development of novel anti-counterfeiting materials is essential to maintaining trust, ensuring regulatory compliance, and mitigating economic losses associated with counterfeit goods. Colloidal crystals are among the most promising anti-counterfeiting materials. [2] Monodisperse colloidal particles self-assemble into crystalline lattices with controlled interparticle interaction. The regular 3-dimensional colloidal crystal lattice endows the particle arrangement with photonic bandgap properties, enabling selective reflection of incident light wavelengths, resulting in vibrant, chemically pigment-free coloration, known as structural colors. Notably, these structural colors from colloidal crystals exhibit remarkable iridescence and dynamic tunability, all while maintaining resistance to bleaching or degradation. This positions colloidal crystals as promising candidates for next-generation anti-counterfeiting materials. The incorporation of light emitters within these colloidal crystals markedly modulates their emission spectra beyond spontaneous emission, driven by suppressed emission within the bandgap and enhanced emission at the band edges. This effect, particularly the stimulated emission at the band edges when optically pumped, is attributed to the slow photon effect, with colloidal crystals acting as optical resonators. Given their facile processability from liquids, spontaneous self-assembly into period nano- and microstructures, and scalable production potential, colloidal crystals hold promise for powerful applications in optics and photonics.

• DFG Programme: Research Grants
• International Connection: South Korea
• Partner Organisation: National Research Foundation of Korea, NRF
• Cooperation Partner: Professor Dr. Shin-Hyun Kim