The electrochemical quartz-microbalance in media of changing viscoelastic properties, and the design and characterization of a suitable driver electronics

In this work we develop a new description of the behaviour of the electrochemical quartz-microbalance (EQMB). It takes into account the phase shift introduced by the driver and also the influence of changing visco-elastic properties of the medium in contact with the quartz (i.e. film and/or liquid). Based on these concepts a new driver circuit has been designed. Its electronics is advanced relative to the classical drivers in two points: a) It allows a partial impedance analysis of the quartz, b) it introduces a controllable phase shift into the system driver+crystal. Thus, an evaluation and even correction of the obtained frequency-results becomes possible. Experimental frequency data obtained in liquids with different visco-elastic properties were corrected with the new approach and compared with theory. The capability of determining the resistive component of the quartz' impedance was also used to determine the limits of the rigid-layer approximation for polypyrrole-films

Processing Follows Function: Pushing the Formation of Self-Assembled Monolayers to High-Throughput Compatible Time Scales

Self-assembled monolayers (SAMs) of organic molecules can be used to tune interface energetics and thereby improve charge carrier injection at metal–semiconductor contacts. We investigate the compatibility of SAM formation with high-throughput processing techniques. Therefore, we examine the quality of SAMs, in terms of work function shift and chemical composition as measured with photoelectron and infrared spectroscopy and in dependency on molecular exposure during SAM formation. The functionality of the SAMs is determined by the performance increase of organic field-effect transistors upon SAM treatment of the source/drain contacts. This combined analytical and device-based approach enables us to minimize the necessary formation times via an optimization of the deposition conditions. Our findings demonstrate that SAMs composed of partially fluorinated alkanethiols can be prepared in ambient atmosphere from ethanol solution using immersion times as short as 5 s and still exhibit almost full charge injection functionality if process parameters are chosen carefully. This renders solution-processed SAMs compatible with high-throughput solution-based deposition techniques

The Membrane Properties of Electroactive Polymer Films

Electroactive polymers fall into two categories. The first group are the redox polymers, which consist of an electronically insulating polymer matrix with attached redox sites.(1–4) The PVPy/Ru matrix represented in Fig. 3.1 is a typical example. The second group are the conjugated polymers, such as polypyrrole, polyaniline, or the poly(Nsulfopropylpyrrole-co-pyrrole) represented in Fig. 3.2. These consist of extended π-electron systems from which electrons can be withdrawn (see Fig. 3.2) or into which additional electrons can be injected.(5–12) The unpaired electrons of the produced radical cations or anions are delocalized over several monomer units of the polymer chain, forming polarons that interact with one another. With increasing concentration they associate to form bipolarons, i.e., electronspin-free dimers.(13)</sup