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Self-doping organic semiconductors provide a promising route to avoid instabilities and morphological issues associated with molecular n-type dopants. Structural characterization of a naphthalenetetracarboxylic diimide (NDI) semiconductor covalently bound to an ammonium hydroxide group is presented. The dopant precursor was found to be the product of an unexpected base catalyzed hydrolysis, which was reversible. The reversible hydrolysis had profound consequences on the chemical composition, morphology, and electronic performance of the doped films. In addition, we investigated the degradation mechanism of the quaternary ammonium group and the subsequent doping of NDI. These findings reveal that the products of more than one chemical reaction during processing of films must be considered when utilizing this promising class of water-soluble semiconductors.

The ability to control the charge density of organic mixed ionic electronic conductors (OMIECs) via reactions with redox-active analytes has enabled applications as electrochemical redox sensors. Their charge density-dependent conductivity can additionally be tuned via charge injection from electrodes, for instance in organic electrochemical transistors (OECTs), where volumetric charging of the OMIEC channel enables excellent transconductance and amplification of low potentials. Recent efforts have combined the chemical detection with the transistor function of OECTs to achieve compact electrochemical sensors. However, these sensors often fall short of the expected amplification performance of OECTs. Here, we investigate the operation mechanism of various OECT architectures to deduce the design principles required to achieve reliable chemical detection and signal amplification. By utilizing a non-polarizable gate electrode and conducting the chemical reaction in a compartment separate from the OECT, the recently developed Reaction Cell OECT achieves reliable modulation of the OECT channel's charge density. This work demonstrates that systematic and rational design of OECT chemical sensors requires understanding the electrochemical processes that result in changes in the potential (charge density) of the channel, the underlying phenomenon behind amplification.

Rapid and efficient measurement of sodium ion concentrations will benefit future studies and healthcare due to the importance of sodium to many biological processes. Ratiometric optical probes, where light absorption wavelengths shift according to ion concentration, can be used as a quick measurement method. In contrast to the currently available UV absorbing probes, we have synthesised a series of sensors which absorb in different regions of the visible spectrum. In addition to measurement by conventional UV-Vis spectroscopy, this also enables analysis of sodium ion concentration from colorimetry, opening the door to faster and cheaper analysis. Finally, the optical properties of the dyes were well reproduced by computational methods, with and without the presence of sodium, enabling acceleration of design of future materials.

The lipid bilayer is the elemental structure of a cell membrane, forming a stable barrier between the interior and exterior of the cell while hosting membrane proteins that enable selective transport of biologically important compounds and cellular recognition. Monitoring the quality and function of lipid bilayers is thus essential and can be performed using electrically active substrates that allow for transduction of signals. Such a promising electronic transducer material is the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) which has provided a plethora of novel bio transducing architectures. The challenge is, however, in assembling a bilayer on the conducting polymer surface, which is defect-free and has high mobility. Herein, we investigate the fusion of zwitterionic vesicles not only on a variety of PEDOT:PSS films, but also on an electron transporting, negatively charged organic semiconductor, in order to understand the surface properties that trigger vesicle fusion. The PEDOT:PSS films are prepared from dispersions containing different concentrations of ethylene glycol included as a formulation additive, which gives a handle to modulate the surface physicochemical properties without a compromise on the chemical composition. A strong correlation between the polarity of the surface, the fusion of the vesicles and the mobility of the resulting bilayer aids in extracting the design principles for the development of future conducting polymers that will enable the formation of lipid bilayers.