TiO2掺杂调控聚苯乙烯微球折射率及胶体光子晶体结构色

胶体光子晶体由于其可调变的结构色在绿色印刷、印染等领域备受关注,而其光子带隙的宽度和位置由光子晶体的晶格参数(晶面间距,通常受胶体微球尺寸影响)和介质的折射率决定。现有人工胶体光子晶体主要基于SiO_2和高分子(如聚苯乙烯(PS)等)微球的组装制备,由于胶体微球材质种类有限,折射率调控受限,因而目前调控胶体光子晶体结构色主要靠改变胶体微球的尺寸来实现。本文首先制备高折射率(2.6)的TiO_2纳米晶,在乳液聚合制备单分散的PS(折射率1.6)微球过程中,将所制备的TiO_2纳米晶掺杂于PS微球中,通过TiO_2的掺杂量有效调控胶体微球的折射率,进而实现胶体光子晶体的结构色调控。以多色胶体光子晶体微球的水溶液为墨水,采用彩色喷墨打印技术打印了电脑设计的光子晶体彩画。本文发展的光子晶体结构色调控新技术拓展了胶体光子晶体的应用。

Tuning the Refractive Indexes and Structural Colors of Colloidal Photonic Crystals by Doping TiO2 Nanoparticles into Polystyrene Microspheres

Colloidal photonic crystals have been widely developed due to their novel optical properties, easy-preparation and low-cost. The structural color of colloidal photonic crystals is highly related to the refractive index and size of the microspheres. But the structural color is tuned mainly based on the controlling of the size instead of the refractive index of the microspheres. Herein, we developed a novel strategy to tune the refractive indexes and thus the structural colors of colloidal photonic crystals by doping different amounts of TiO₂ nanoparticles into polystyrene microspheres (PS). After doping with TiO₂, the films of TiO₂-PS composite microspheres with TiO₂-dosages of 0.22% (220 nm), 2.10% (250 nm) and 9.87% (290 nm) demonstrate green, yellow and red structural color, respectively. Finally, colorful photonic crystal patterns were successfully printed with the aqueous colloid solution of these as-prepared TiO₂-PS microspheres as ink. This facile fabrication strategy will be easy to be extended to other composite microspheres by doping different inorganic nanoparticles with different refractive indexes.