Swelling of Gel-Immobilized Colloidal Photonic Crystals in Ionic Liquids

A study was conducted to demonstrate the use of hydrophilic ionic liquids as suitable swelling solvents for gel-immobilized colloidal crystals. The optical stop band of the colloidal crystals had the potential to be adjusted over a wide range of wavelengths by varying the mixing ratio of hydrophilic and hydrophobic ionic liquids. It was also demonstrated that the stop-band wavelength was linearly dependent on the mixing ratio, making it more advantageous in practical applications. The system used to conduct the investigations consisted of loosely packed colloidal crystals immobilized in a hydrogel film. It was demonstrated that a gel film shrunk considerably when it was soaked in hydrophobic ionic liquids, such as 1,3-diallylimidazolium bis(trifluoromethanesulfonyl)imide. It was observed that the structure of the colloidal crystal immobilized in the gel was destroyed, the sample turned cloudy, and the Bragg peak in the spectrum disappeared in such a case.