*2.2.1. Synthesis of the poly(VP-co-Ru(bpy)3) gel*

The gel was prepared as follows. 0.110g of Ru(bpy)3 as a metal catalyst for the BZ reaction was dissolved in 0.877g of vinylpyrrolidone (VP). 0.012g of N,N'-methylenebisacrylamide (MBAAm) as a cross-linker, and 0.020g of 2,2'-azobis(isobutyronitrile) (AIBN) as an initiator were dissolved in the methanol solution (3ml) (Figure 1). The two solutions were mixed together well, and then the mixed solution purged with dry nitrogen gas. The monomer solution was injected between Teflon plates separated by silicone rubber as a spacer (thickness: 0.5mm), and then polymerized at 60°C for 18 hours. After gelation, the gel strip was soaked in pure methanol for a week to remove unreacted monomers. The gel was carefully hydrated through dipping it in a graded series of methanol-water mixtures, for 1 day each in 75, 50, 25 and 0%.
