Tunable emission in poly(4-vinylpyridine)-based gel

We have discovered a new class of smart-gels, poly(4-vinylpyridine) (PVPy) swollen with pyridine (Py), that following photoexcitation (395, 455, 557 nm) emits three independent colors: blue, green, and red (477, 527, 585 nm, respectively). These excitation wavelengths also induced large reversible changes in pH and electrical conductivity. The primary photoexcitation paths within this photo-active gel are singlet-excitons. The origin of this phenomenon is attributed to the combined properties of weak coupling via hydrogen-bonding and high polarizability. Our preliminary model suggests, that C-H'"N based Py associates are formed during the gelation process. Photoexcitation leads to proton transfer within three different kinds of assemblies and to a solid-state-like electronic behavior of the gel. This system, i.e. a photoconducting transparent organic gel with multiple color emission, is very attractive for a wide range of promising applications in the field of optoelectronic devices such as organic LED's and 3D holography.