Optical properties and photo-oxidation of tetraphenylethene-based fluorophores.

We report the optical properties of tetraphenylethene (TPE) and other TPE derivatives functionalised with an octyl group (TPE-OCT) and polyethyleneglycol group (TPE-PEG) in the side chain. We compared TPE-OCT and TPE-PEG with TPE in both organic solvents and under aqueous conditions. All materials exhibit aggregation-induced emission, however, uncommonly, TPE-PEG seems to aggregate in aqueous solution with enhanced photoluminescence quantum efficiency (PLQE) relative to that in organic solvents. All three materials can be photo-oxidised in solution to their diphenylphenanthrene derivative by irradiation with UV light (at both ≈1 and ≈5 mW cm(-2)), with a subsequent enhancement in PL efficiency. The electron-donating ether group increases the rate of oxidation relative to bare TPE and also photo-oxidation was shown to be solvent and concentration dependent. Finally, photo-oxidation was also demonstrated in the aggregate state.