Heteropoly acids triggered self-assembly of cationic peptides into photo- and electro-chromic gels
Jingfang Li, Jing Xu, Xiaodong Li, Wenmei Gao, Liyan Wang, Lixin Wu, Myongsoo Lee, Wen Li
A series of cationic peptides with alternated lysines and hydrophobic residues were designed and synthesized. This kind of short peptides with protonated lysines can complex with anionic heteropoly acids (HPAs) to form stable gel in water/ethanol mixed solution. Circular dichroism spectroscopy showed that the short peptides adopted mixed conformation (-sheet and random-coil) within the gel matrix. Scanning and transmission electron microscopy revealed that the heteropoly acids, acting as nanosized cross-linkers, first initiated the self-assembly of the cationic peptides into spherical nanostructures. Then these nanospheres accumulated with each other through hydrogen bonds and hydrophobic interactions to form large sheet-like assemblies, which further interconnected with each other forming continuous 3D network structures. Fourier-transform infrared spectroscopy showed that the structural integrity of the HPAs was maintained during the gelation process. The resultant hybrid gels showed reversible photo- and elecrtrochromic properties. X-ray photoelectron spectroscopy revealed that the hybrid gels, capable of persistent and reversible changes of their colour, are attributed from the intervalence charge-transfer transition of the HPAs. Reversible information writing and erasing were demonstrated through repeated photo-lithograph or electric voltage without significant loss of the gel performance.
Circular dichroism, Secondary structure, Materials, Biochemistry