Graphene quantum dot-coated polystyrene microsphere multilayer colloidal crystals with distributed Bragg reflector absorption

Abstract Distributed Bragg reflector (DBR) absorptive materials have broad application prospects in lasers, optical fibre communications , LEDs, solar cells, and optoelectronic devices. This study used dispersion polymerization to prepare monodisperse polystyrene (PS) microspheres of different particle sizes. Graphene quantum dots (GQDs) dispersion was prepared using the ultrasonic dispersion method, and GQDs were self-assembled on the surface of modified PS spheres to form PS@GQDs mi-crospheres. By precise titration and surface tension uniform gravity sedimentation, the volume ratio (GQDs:PS) and thickness of GQDs colloidal crystals were controlled. The results showed that the potential modification of the PS surface significantly red-shifted the near-infrared characteristic peak of PS@GQDs colloidal crystals. The interference fringes of GQDs of various sizes with PS microspheres formed Bragg reflectors, creating longer wavelength intervals and larger resonance amplitudes below 1200 nm. The regulation of the photonic bandgap and the quantum confinement effect of GQDs showed a clear dependency. The lattice constant significantly influenced the near-infrared optical properties of colloidal crystals. Colloidal crystals exhibited different sensitivities to internal structural defects and orderliness across various spectral ranges. Raman studies indicated that increased GQD concentration formed magic-angle graphene, and increased thickness enhanced local electromagnetic field effects, multiple scattering effects, and optical gain. Therefore, this study provides a method to achieve tunable near-infrared shielding or optical absorption materials by adjusting the concentration of GQDs, the particle size of PS@GQDs microspheres, and the thickness of colloidal crystals, which can be applied to distributed Bragg reflector absorptive devices.