Optical Properties Based On Colloidal Microsphere Photonic Crystal Structurally-colored Fibers

Dyeing is a vital process in textile industry,which lets the fabrics appear with the different colors.However,Dyeing process consumes a huge amount of fresh water to dissolve the pigments and flush the fabrics.Eventually the unabsorbed remains of the pigments in the water form the industrial sewage,which gives rise to the severe pollution to the environment.Structural colors are the light in the range of visible light being strongly reflected,diffracted or scattered by the complex interaction between light and intricate nanostructures,which will display gorgeous colors.Compared with the chemical dyes,structural colors have the merits of dye-free,low energy-consuming and non-fading,which could be a promising way to make the fibers colored.In recent years,several attempts have been conducted to fabricate the cylindrical fibers based on the colloidal assembly,while the fabrication methods and understanding on the optical properties of these fibers are still lacking.In this thesis,structurally-colored fibers were fabricated by soaking the superfine capillary tubes into polystyrene(PS)nanosphere dispersion through the feasible colloidal self-assembly.Nanospheres in the capillary tube formed a cylindrical colloidal crystal fiber as water was evaporated slowly.The different colors from the fibers are originated from the Bragg reflection of curved face-centered cubic(f.c.c.)(111)planes of the colloidal crystal interacting with the light.Apparently the colors of colloidal crystal fibers could be easily tuned by altering the size of colloidal nanospheres or changing the diameter of the capillary tubes.The reflective spectra in the radial direction were independent of the incident angle of the light as the incident angles changed from 0° to 30°due to the cylindrical symmetry of the fibers,while the spectra in the longitudinal direction notably blue-shifted.Furthermore,the numerical models were employed to calculate the optical properties of colloidal crystal fibers.The calculated results were in accordance with the results measured by experiment.The calculation demonstrates that reflective spectra are affected by the order of outer layers of colloidal fibers regardless of the inner irregularity.The defects and cracks on the surface layers of the colloidal fibers or the increase of lattice constant of the fibers could blue-shift and broaden the experimental spectra.Also,the energy state density distribute of the fibers were studied to further demonstrate the existence of structural colors of the fibers which coincide well with the reflective spectra.Finally,the PS nanospheres with two distinct diameters in a certain proportion were filled into the capillary tubes to fabricate structurally-colored fibers.As a result,the different colors from the fibers are not as gorgeous as the colloidal fibers assembled by nanospheres with uniform size owing to the arrangement of the colloidal nanospheres which deviated from the ideal f.c.c.structure.