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.

Control over the surface chemistry and physics of electronic and optical materials is essential for constructing devices and fine-tuning their performance. In the past few years we have started to explore the use of organic molecules for systematic modification of semiconductor surface electronic properties. In this paper, manipulation of silicon surfaces by self-assembly of various quinolinium-based chromophores is reported. The progress of the assembly process is monitored by XPS, UV-Vis, and FTIR spectroscopies as well as with surface wettability. The effect of the monolayer's dipole-moment on the Si surface potential and the interaction with surface states is monitored by CPD measurements. A pronounced effect of a sub-nanometer coupling-agent layer alone on the electron affinity and band-bending of Si was observed. We also show a way to modulate the Si work-function by tuning the dipole strength of the chromophore-containing organic, self-assembled monolayer and of its orientation with respect to the silicon surface.