In this work we show dipole-assisted photogated switching by covalent grafting of photoactive molecules to conducting polymers. Photochromic spiropyran molecules were covalently attached to polyaniline (PANI) nanowires via N-alkylation reaction to the quinoic part of PANI. Upon irradiation with ultraviolet light spiropyran transformed to a large dipole containing molecule, merocyanine form. We show that this transformation leads to a substantial (ca. 2 orders of magnitude) increase in conductance of the photochromic PANI nanowires, which were evident by an increase in field-effect mobility and calculated band gap narrowing of the system. Finally, this transformation was found to be fully reversible with no significant photofatigue.

We report on a novel approach to synthesize hybrid nanostructures of meso porous silicon and conjugated organic polymers that are suitable for solar cell applications. Meso-porous silicon substrates with relatively large pores (\~100 nm) have been exploited for electrochemical polymerization of organic monomers, which were introduced into the porous silicon matrices and electro-polymerized to create poly-vinyl-carbazole (PVK). We present electrical characteristics of a device having relatively thin films of the hybrid medium, which exhibits a photovoltaic mode of operation

This paper describes remarkably high sensitivities in the label-free detection of kinase-promoted phosphorylation for 14 different peptide substrates on electrode-immobilized monolayers (gold or nitride) using serine/threonine kinases PKA, PKC, and CaMK2. Peptide substrates were preselected using ³³P-labeling in a microarray of 1024 substrates. The three most active peptides (A1–A3, C1–C3, and M1–M3) were investigated using electrochemical impedance spectroscopy (EIS) and ion-sensitive field effect transistors (ISFETs). Some of the peptide substrates, for example, the PKC-specific substrate PPRRSSIRNAH (C1), showed a remarkably high sensitivity in the EIS-based sensor measurements. Our studies revealed that this high sensitivity is primarily due to the monolayer’s packing density. Nanoscopic studies demonstrated a distinct disordering of the C1-monolayer upon phosphorylation, while phosphatase-promoted dephosphorylation regenerated the highly ordered peptide monolayer. As a matter of fact, the initial surface packing of the peptide monolayer mainly determined the level of sensitivity, whereas electrostatic repulsion of the redox-active species was found to be much less important.

Selectivity is one of the most challenging issues in biosensor design. Several methods have been proposed in the past to overcome nonspecific interference. In particular, it has been shown that temperature curves can be used to simultaneously measure two similar analytes. Here, the performance of such thermal-based systems is analyzed, using least squares estimation and existing models for affinity-based sensing, and it is shown that a D-optimal difference for the sensor temperatures exists. Analysis at this optimized condition yields bounds on the sensitivity and selectivity of this class of sensors. For the first time, thermal discrimination is employed for an affinity-based sensor: an artificial receptor-based system for the detection of the neurotransmitter acetylcholine and its metabolite choline. The system performance demonstrates the practicality of the theoretical results presented.