​Par le Professeur Gi-Ra Yi
Soft Matter Research Lab, School of Chemical Engineering
SungKyunKwan University (SKKU)
Republic of Korea

Hollow silica nanospheres can be prepared by removing cores from silica-coated polystyrene particles. Their colloidal crystals showed a strong but angle-dependent color. For colloidal glasses, we have mixed bidisperse hollow silica nanospheres with the same cores and then backfilled interstices between hollow nanospheres with index-matched polymers forming inverse colloidal glasses. When interparticle distance corresponds to the wavelength of visible (λ~2nd), they show a strong reflectance peak in visible from ‘structure factor  and another peak in UV from ‘form factor . By varying shell thickness and the average distance between air voids, the peak from the structure factor can be tuned in visible while another peak from form factor can be kept in UV. Furthermore, we can increase the particle size for shifting form factor and structure factor to visible and IR, respectively, which can be potentially useful as IR-reflective paints. In order to avoid multiple scatting, a hydrocarbon part in the organosilica shell was carbonized during thermal annealing. In addition, we have demonstrated UV reflective paints by reducing particle size and interparticle distance of which structure factor corresponds to UV wavelength.