A water-soluble Ir(iii) complex is shown to enhance the ‘remote’ mechanism of the most widely used co-reactant ECL reaction of tris(2,2′-bipyridine)ruthenium(ii) with tripropylamine.

Previously reported annihilation ECL of mixtures of metal complexes have generally comprised Ir(ppy)3 or a close analogue as a higher energy donor/emitter (green/blue light) and [Ru(bpy)3]2+ or its derivative as a lower energy acceptor/emitter (red light). In contrast, here we examine Ir(ppy)3 as the lower energy acceptor/emitter, by combining it with a second Ir(iii) complex: [Ir(df-ppy)2(ptb)]+ (where ptb = 1-benzyl-1,2,3-triazol-4-ylpyridine). The application of potentials sufficient to attain the first single-electron oxidation and reduction products can be exploited to detect Ir(ppy)3 at orders of magnitude lower concentration, or enhance its maximum emission intensity at high concentration far beyond that achievable through conventional annihilation ECL of Ir(ppy)3 involving comproportionation. Moreover, under certain conditions, the colour of the emission can be selected through the applied electrochemical potentials. We have also prepared a novel Ir(iii) complex with a sufficiently low reduction potential that the reaction between its reduced form and Ir(ppy)3+ cannot populate the excited state of either luminophore. This enabled, for the first time, the exclusive formation of either excited state through the application of higher cathodic or anodic potentials, but in both cases, the ECL was greatly diminished by parasitic dark reactions.

Colored and color-changing materials are central to perception and interaction in nature and have been exploited in an array of modern technologies such as sensors, visual displays and smart materials. Attempts to introduce color into carbon fiber materials have been limited by deleterious impacts on fiber properties, and the extension of colored fibers towards 'smart composites' remains in its infancy. We present carbon fibers incorporating structural color, similar to that observed on the surface of soap bubbles and various insects and birds, by modifying the fiber surface through in situ polymerization grafting. When dry, the treated fibers exhibit a striking blue color, but when exposed to a volatile solvent, a cascade of colors across the visible region is observed as the film first swells and then shrinks as the solvent evaporates. The treated fibers not only possess a unique color and color-changing ability, but can also be reversibly formed into complex shapes and bear significant loads even without being encased in a supporting polymer. The tensile strength of treated fibers shows a statistically significant increase (+12%) and evaluation of the fiber-to-matrix adhesion of these polymers to an epoxy resin shows more than 300% improvement over control fibers. This approach creates a new platform for the multifaceted advance of smart composites.