Micron-sized SiO₂ hollow microspheres were prepared by a hard template encapsulation method and an ethyl acetate etching process with polystyrene (PS) as a template, hexadecyltrimethylammonium bromide (CTAB) as a surface modifier, and tetraethyl orthosilicate (TEOS) as a silicon source, and vertically deposited self-assembled into micron-sized SiO₂ hollow microsphere photonic crystals. The effects of TEOS content and etching conditions on the morphology of hollow microspheres, as well as the effect of vertical deposition self-assembly solution concentration on the infrared properties of micrometer sized SiO₂ hollow microsphere photonic crystals were investigated.

For the preparation of micron-sized PS@SiO₂ microspheres, 0.15 g of polystyrene microspheres with the size of 1.5 μm were dissolved in 160 mL of deionized water and 80 mL of anhydrous ethanol. After ultrasonic dispersion, 0.03 g of CTAB was added to modify the surface of the polystyrene template under stirring. After 30 min, 3 mL of 25% ammonia water was added to prepare solution A. 0.2 mL of ethyl orthosilicate was dissolved in 5 mL of anhydrous ethanol to prepare solution B. Solution B was mixed with solution A under stirring at room temperature for 24 h. The reacted solution was filtered and washed with anhydrous ethanol and deionized water for three times. PS@SiO₂ material was obtained after drying.

For the preparation of micron-sized SiO₂ hollow microspheres, 0.5 g of PS@SiO₂ microspheres were dispersed in 20 mL of ethyl acetate, and heated at 60 ℃ for 10 min after ultrasonic dispersion. The PS template was etched off by ethyl acetate. Subsequently, the slurry was filtered and washeda with anhydrous ethanol and deionized water for three times to obtain micron-sized SiO₂ hollow microspheres.

For the preparation of micron-sized SiO₂ hollow microsphere photonic crystals, a microsphere suspension was dispersed for a certain time, and then a cleaned hydrophilic glass substrate was vertically immersed into the microsphere suspension, and dried at 60 ℃. As the mixed solvent evaporates, the microspheres self-assemble on the surface of the substrate into a photonic crystal thin film with an opal structure.

Micron-sized SiO₂ hollow microspheres with a low damage rate, a good dispersibility, and a high sphericity were prepared with PS spheres as a template, CTAB as a surfactant, and TEOS as silicon source. PS template was removed via ethyl acetate etching. At TEOS content of 0.2 mL, PS@SiO₂ microspheres are tightly coated, and there are no secondary microspheres. When ethyl acetate is used for etching for 10 min, the hollow SiO₂ microspheres with the diameter of 1 570 nm and thickness of 65 nm are prepared. Moreover, micron-sized SiO₂ hollow microspheres are self-assembled into photonic crystal materials by a vertical deposition method. As the concentration of self-assembly solution increases, the arrangement of SiO₂ hollow microspheres is tightly ordered without obvious vacancies and with a hexagonal periodic structure. The number of layers increases from 6 to 16, and the reflectivity gradually increases. When the solubility of the self-assembled solution is 0.005 g/mL, the maximum reflectivity is 85%.

The micron-sized SiO₂ hollow microspheres with a good dispersion, a high uniformity, a less damage, and a high sphericity were prepared by a template encapsulation method and an ethyl acetate etching process. Also, micron-sized SiO₂ hollow microsphere photonic crystals with a good thermal insulation performance, a low density, and a reflectivity of 85% as infrared band hollow microsphere photonic crystals were prepared by a vertical deposition self-assembly method.