title: Physically controlled cross-linking in gelated crystalline colloidal array photonic crystals.
abstract: We prepared a poly(vinyl alcohol) (PVA) gelated crystalline colloidal array (GCCA) through physical cross-linking. PVA hydrogel was formed by utilizing a chilling-thawing method while the CCA was physically immobilized within the PVA hydrogel matrix. After being chilled at 2 degrees C for 24 h, the gel could be formed without disturbing the CCA. With the repetition of chilling-thawing cycle, the hydrogel network was reinforced. This photonic crystal material could be shaped as needed and efficiently diffracts visible light, and the diffraction wavelength can be tuned anywhere within the visible spectrum by simply varying the CCA concentration. The GCCA represents sol-gel reversibility as the temperature is cycled. It has been observed that the GCCA retained its ability of diffraction after rehydration, and the sample could be stored for long periods of time. We further functionalized the PVA hydrogel with Chitosan (CS), and the pH sensing behavior of the PVA/CS GCCA was observed. It revealed that the sensitivity of the PVA/CS GCCA correlates with the CS concentration.
authors.affiliation: Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.forename: Yihua
authors.initials: Y
authors.lastname: Zhu
authors.forename: Hua
authors.initials: H
authors.lastname: Bao
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Yang
authors.forename: Chunzhong
authors.initials: C
authors.lastname: Li
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D003460:Crystallization / Q000379:methods*; D005782:Gels / Q000737:chemistry*; D008422:Materials Testing; D044367:Phase Transition; D017785:Photons; D011142:Polyvinyl Alcohol / Q000737:chemistry*
chemical_list: D003102:Colloids; D003432:Cross-Linking Reagents; D005782:Gels; D011142:Polyvinyl Alcohol