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

Distributed Bragg reflector (DBR) absorptive materials have broad applications in optical fibre communications, solar cells, and other fields. This study adopts dispersion polymerization to prepare monodisperse polystyrene (PS) microspheres. Graphene quantum dots (GQDs) are prepared using the ultrasonic dispersion method. By coating GQDs on surfaces of PS spheres, the micron-sized core-extremely thin shell, PS@GQDs structures are self-assembled successfully. Finally, using the improved gravity sedimentation, the unconventional colloidal crystals of PS@GQDs structures are fabricated and characterized for the first time. The unconventional colloidal crystals of PS@GQDs exhibit tunable DBR scattering absorption, ranging from near-ultraviolet to near-infrared, which is unlike the conventional DBR. The experimental observations and measurements indicate that the modification of the PS surface significantly red-shifted in the ultraviolet-near infrared bands (300–1200 nm). The interference fringes of GQDs of various sizes with PS spheres formed Bragg reflectors, creating larger amplitudes below 1200 nm. Raman spectra show that the colloidal crystals display the peaks of polystyrene with a red-shift. The numerical simulations indicate that the DBR phenomena can be understood as the topological excitations at the structure transitions in the plasmon resonances and photonic band crossovers.