An Insight into Ionic Conductivity of Polyaniline Thin Films

The work addresses an issue of the conductivity phenomenon in conductive polymer thin films. Polyaniline was chosen as a broadly used and thoroughly investigated conductive polymer in order to test and show capabilities of the developed original approach based on impedance spectra analysis. A number of films of different thickness were deposited onto a Pt electrode surface and consequently investigated in aqueous solution containing perchloric acid as an electrolyte. The processes that occur in polyaniline film were studied by cyclic voltammetry, electrochemical quartz crystal microgravimetry (EQCM) and electrochemical impedance spectroscopy (EIS). The role of incorporated ions as charge carriers was investigated with respect to the control of the conductivity properties of the film. Along with detailed polyaniline behavior study, the work makes up a fundamental scientific impact on theoretical electrochemistry and electroanalytical techniques.

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Synthesis and photophysical properties of novel oxadiazole substituted BODIPY fluorophores

Using 3-phenyl-5-(5-phenyl-1H-pyrrol-3-yl)-1,2,4-oxadiazole, BODIPYs with the oxadiazole groups at the 1,7-positions were prepared and their photophysical properties were characterized.

Three Destinies of Solution-Processable Polymer Light-Emitting Diodes under Long-Time Operation

The article describes three different ways of polymer light-emitting diode (PLED) degradation, caused by damage of the protective layer. The electroluminescence and charge-transport properties of a completely encapsulated diode, the diodes with a leaky protective layer and diodes without encapsulation were compared under long-time exploitation. The studied devices incorporated Super Yellow light-emitting poly-(1,4-phenylenevinylene) PPV copolymer as an electroluminescence component, and (poly-(3,4-ethylenedioxythiophene)–poly-(styrene sulfonate) (PEDOT:PSS) as a charge-transport layer between the indium tin oxide (ITO) anode and aluminum–calcium cathode. To analyze the PLED degradation mechanism regarding charge transport, impedance spectroscopy was used. The values of resistance and capacitance of the internal layers revealed an effect of applied voltage on charge carrier injection and recombination. The factors responsible for the device degradation were analyzed on a macromolecular level by comparing the plots of voltage dependence of resistance and capacitance at different operation times elapsed.

Synthesis and in vitro cytotoxic activity of dye-linker-macrocycle conjugates with variable linker length and components

The study investigated the structure-activity relationship of newly synthesized dye-linker-macrocycle (DLM) conjugates and the effect of each component on various biological properties, including cytotoxicity, cellular uptake, intracellular localization, interaction with DNA and photodynamic effects. The conjugates were synthesized by combining 1,8-naphthalimide and thioxanthone dyes with 1,4,7,10-tetraazacyclododecane (cyclen) and 1-aza-12-crown-4 (1A12C4) using alkyl linkers of different lengths. The results revealed significant differences in biological activity among the various series of conjugates. Particularly, 1A12C4 conjugates exhibited notably higher cytotoxicity compared to cyclen conjugates. Conjugation with 1A12C4 proved to be an effective strategy for increasing cellular uptake and cytotoxicity of small-molecule conjugates. In addition, the results highlighted the critical role of linker length in modulating the biological activity of DLM conjugates. It became clear that the choice of each component (dye, macrocycle and linker) could significantly alter the biological activity of the conjugates.

Investigating perimidine precursors for the synthesis of new multiredox polymers

We present a new simple approach for electrochemical synthesis of semi-condensed ambipolar perinone polymers with phthaloperine (p1) or phenanthroline (p2) skeleton from available and cheap perimidine precursors. Polymerization of perimidine derivatives varies in efficiency depending on the monomer, but overall is highly efficient, especially when electropolymerization is used. Electrooxidation is well controllable and provides a certain characteristic share of new bonds in the structure of perimidine polymers: semi-ladder bis-perimidine unit, ladder bis-perimidine unit, and protonated bis-perimidine unit. Polymer p2 obtained with higher efficiency was put through broader analysis (UV-Vis, IR, ESR and quantum-chemical calculations). As indicated, donor-acceptor structure and specific intermolecular interactions of p2 assure its electrical conductivity and complex redox activity. Although protonated bonds break π-conjugation in the structure of the macromolecule, there is also a diradical state that favors intermolecular interactions and intermolecular π-conjugation channels within bis-perimidine segments. It has been proven that there is a diradical state which appears as an intermediate state between the oxidized and reduced states of the protonated polymer unit. This work positions perimidine polymers as a versatile ambipolar multiredox p- and n-type conductor, indicating a potential for expanding perinone-based perylene-diperimidine polymers for innovative electronics and (bio)sensors.

New Benzo[h]quinolin-10-ol Derivatives as Co-sensitizers for DSSCs

New benzo[h]quinolin-10-ol derivatives with one or two 2-cyanoacrylic acid units were synthesized with a good yield in a one-step condensation reaction. Chemical structure and purity were confirmed using NMR spectroscopy and elemental analysis, respectively. The investigation of their thermal, electrochemical and optical properties was carried out based on differential scanning calorimetry, cyclic voltammetry, electronic absorption and photoluminescence measurements. The analysis of the optical, electrochemical and properties was supported by density functional theory studies. The synthesized molecules were applied in dye-sensitized solar cells as sensitizers and co-sensitizers with commercial N719. The thickness and surface morphology of prepared photoanodes was studied using optical, scanning electron and atomic force microscopes. Due to the utilization of benzo[h]quinolin-10-ol derivatives as co-sensitizers, the better photovoltaic performance of fabricated devices compared to a reference cell based on a neat N719 was demonstrated. Additionally, the effect of co-adsorbent chemical structure (cholic acid, deoxycholic acid and chenodeoxycholic acid) on DSSC efficiency was explained based on the density functional theory.