Polythiophene nanoparticles that display reversible multichromism in aqueous media

The polythiophene nanoparticles exhibit multichromic responses to solvent, temperature and acid/base, which can be detected by the naked eye in tetrahydrofuran/water mixtures. As the concentration of water increases, the nanoparticles turn from yellow to violet by solvatochromism. The nanoparticles display a reversible thermochromic response between 20 and 90 °C, which originates from the morphological changes between an amorphous solid and isotropic liquid. Halochromic behavior of the nanoparticles is achieved by adding hydrobromic acid and bubbling with ammonia gas owing to p-doping and dedoping of the polythiophene nanoparticles, respectively.