Sequential In-Situ Growth of Layered Conjugated Polymers for Optoelectronics Under Electrochemical Control.

Layered optoelectronic devices are manufactured using multistep procedures that require high precision in the spatial positioning of individual materials. Current technology uses costly and tedious procedures and instrumentation. In this work instead, we propose an approach which exploits the fundamental properties of the substrate to direct the growth of the next layer, here controlled by an electrochemical potential. We have electrochemically synthesized and characterized a series of polymeric materials that are most commonly used in the field. The films produced show gradient monomer ratios embedded in the polymeric film as a function of the distance from the working electrode. Under the optimized conditions, reproducible construction of simple electronic elements, e. g., rectifying diodes, is achieved. We argue that the sequential in situ method leads to gradient composition of polymer chains and the film resulting in the rectification of electric current. We discuss how this system can open new avenues in advanced optoelectronic applications, such as organic light-emitting diodes (OLEDs) or field-effect transistors (OFETs).

Acid-assisted polymerization: the novel synthetic route of sensing layers based on PANI films and chelating agents protected by non-biofouling layer for Fe2+ or Fe3+ potentiometric detection.

A new synthetic method for the fabrication of a sensing layer is presented. PANI films as an ion-to-electron transducer were prepared via acid-assisted polymerization in concentrated formic acid (HCOOH) in the presence of ethanol and ammonium persulfate (APS, as the initiator). The ratio of monomer to ammonium persulfate was 1 : 0.1. 2,2-Bipyridyl, 1,10-phenanthrolin-5-amine, and 8-hydroxyquinoline were used as chelating agents that can complex Fe2+ or Fe3+ ions. The proposed sensors demonstrated an appropriate reproducibility with a rapid response to the presence of Fe2+ or Fe3+ ions, even at T ∼ 37 °C. It was revealed that the method of deposition of a chelating molecule affects the response of sensors. The in situ deposition during acid-assisted polymerization leads to a fast response compared to the layer-by-layer deposition. PMeOx/X1-PANI@FTO and PMeOx/Z1-PANI@FTO sensors exhibit rapid response and are considered a promising detection layer for Fe2+ or Fe3+ ions respectively. We envision that this system can contribute to the next generation of advanced bio-sensors for the potentiometric detection of iron.

Potentiometric Performance of Ion-Selective Electrodes Based on Polyaniline and Chelating Agents: Detection of Fe2+ or Fe3+ Ions.

We constructed a sensor for the determination of Fe2+ and/or Fe3+ ions that consists of a polyaniline layer as an ion-to-electron transducer; on top of it, chelating molecules are deposited (which can selectively chelate specific ions) and protected with a non-biofouling poly(2-methyl-2-oxazoline)s layer. We have shown that our potentiometric sensing layers show a rapid response to the presence of Fe2+ or Fe3+ ions, do not experience interference with other ions (such as Cu2+), and work in a biological environment in the presence of bovine serum albumin (as a model serum protein). The sensing layers detect iron ions in the concentration range from 5 nM to 50 µM.