Acetylcholinesterase-induced fluorescence turn-off of an oligothiophene-grafted quartz surface sensitive to myristoylcholine.

Conjugated polyelectrolytes (CPEs) have recently emerged as label-free materials for biosensing due to their intrinsic ability to transduce an amplified optical signal in response to interactions with different analytes. Herein, the conformational change of an anionic oligothiophene is exploited to generate a unique fluorescent response upon interaction with myristoylcholine (MyrCh). The variations observed in spectroscopic signals are explained in terms of a synergistic combination of hydrophobic and electrostatic forces involving the oligothiophene chains and MyrCh molecules, inducing the disassembling of oligothiophene chains. The enzyme acetylcholinesterase (AChE) is able to reverse this effect by catalyzing the hydrolysis of MyrCh; hence, its enzymatic activity can be monitored through the variation of fluorescence emission of the system. The oligothiophene sensing probe retains its conformational sensitivity with regard to the AChE-mediated cleavage of MyrCh upon immobilization onto a quartz substrate, which is accomplished by a "grafting onto" approach based on click chemistry. These results are encouraging for the further development of such a label-free system towards the fabrication of sensing devices that would incorporate CPEs and would be potentially useful for the specific detection of a wide range of bioanalytes.

Solid state and solution fine tuning of the linear and nonlinear optical properties of (2-pyrene-1-yl-vinyl)pyridine by protonation-deprotonation reactions.

The unexpected and acido-triggered reversible luminescence and nonlinear optical properties of (2-pyrene-1-yl-vinyl)pyridine, a simple and highly transparent chromophore, are studied both in solution and in the solid state. Remarkably, for the first time the acidomodulation of the NLO response of a poled thin film is reported.

Diffusion-mediated resonant energy transfer in lanthanide-based polymer white-light-emitting diodes.

We present a single layer, polymer white light emitting diode (WOLED) based on novel organic lanthanide complexes. The device is solution processed and possesses CIE coordinates of (0.33, 0.38), corresponding to a high color purity white light emission. The electroluminescence in this diode is found to originate from both the direct charge trapping on the lanthanide complexes and from the efficient diffusion-assisted long-range energy transfer between the conductive matrix and these emissive dopants. An expression for the steady-state transfer efficiency is given, the role of excitation diffusion in the system under study is quantitatively evaluated, and the values for the singlet exciton diffusion coefficients and diffusion lengths in the host are determined.