The paper describes results of comparative testing spray-coated layers of water-dispersible polyaniline (PANI) complexes with polyacids of different chemical structure as hole-injection layers (HILs) in an organic light-emitting diode (OLED) based on a poly(1,4-phenylenevinylene) copolymer (Super Yellow) as an emissive layer. OLEDs using HILs made of poly(3,4-ethylenedioxythiophene) complex with polystyrene sulfonate prepared by spin and spray coating were used as references. OLEDs using HILs based on PANI complexes with poly(4,4 '- (2,2 '-disulfonic acid)-diphenylene-tere-phthalamide) (t-PASA) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) demonstrated the highest current efficiencies of 6-7 cd/A, that is about 20% higher than this value in the best reference sample. The results were discussed in terms of crucial influence of the HIL morphology (analyzed in two scales) on the OLEDs' efficiency. Morphology of the HILs made of PANI:t-PASA and PANI:PAMPSA complexes were found to be most favorable in the following scales: few microns scale-moderately rough (but not completely smooth) intrinsic film texture derived from intermolecular packing; tens of microns scale-weak manifestation of irregularities induced by the spray coating method.

The properties of single-component Langmuir monolayers based on 10,12-pentacosadiynoic acid (PCDA) and films formed by its photopolymerization (polyPCDA) have been compared with analogous monolayers and polymer films based on the mixture of PCDA and a boron difluoride complex with hemicurcuminoid (CurBF2). Structural, morphological, and optical properties of both systems are investigated using Langmuir monolayer compression isotherms, atomic force microscopy (AFM), Brewster angle microscopy, UV-Vis spectroscopy, fluorescence spectroscopy, and fluorescence microscopy. It was discovered that presence of the CurBF2 complex in the system profoundly influences the film morphology and its optical properties. Furthermore, CurBF2 substantially lowers the activation barrier for polymerization at the air-water interface. This study demonstrates that the structural and chromatic characteristics of planar polyPCDA polymer assemblies are significantly altered by the incorporation of the CurBF2 complex into the polymer structure. This results in the emergence of novel morphologies and unique optical properties and opens up prospects for improving the functional characteristics of the mixed system. In particular, the mixed film exhibits synergistically enhanced fluorescent response to Pb2+ compared to polyPCDA itself. Moreover, the revealed effect of CurBF2 on the above properties of the mixed films allows monitoring the fluorescence response to lead ions through two fluorescence channels.

An efficient, simple, and convenient method for Suzuki polycondensation using a diaminocarbene palladium(II) catalyst under aerobic conditions was developed. Reactions between aromatic diboronic acid bis(pinacol) ester and different aromatic dibromides, both with electron-donating and electron-withdrawing fragments in the structure, were carried out. Various reaction conditions, such as the effect of catalyst concentration and solvent, were investigated. The molecular weight characteristics, photo- and electroluminescence properties of the synthesized polymers were studied.

Four new donor-acceptor conjugated polymers based on the acceptor block 8,10-bis(2-octyldodecyl)-8H-dithieno[3 ',2 ':5,6;2 '',3 '':7,8]naphtho[2,3-d]imidazole-9(10H)-one and various donor moieties were synthesized. Binary and ternary composites comprising new polymers, PC71BM fullerene and non-fullerene acceptors based on indacenodithiophene, were developed. The mobility of electrons and holes in thin films of the ternary composites is balanced in contrast to that in binary composite films. This is explained by less aggregation in the ternary composite films and good matching of the frontier orbital energy levels of the composite components.

Chemical polymerization of aniline was carried out in aqueous solutions of sulfonated polysulfone (SPS) at different concentration ratios of aniline and SPS sulfo groups. The polymerization progress was investigated by in situ spectroscopy in the UV–visible–near-IR region. It has been shown that, with increasing concentration of SPS, the rate of polymerization increases. Films of water-dispersible complexes of polyaniline (PANI) with SPS were obtained by spray coating. The electronic and chemical structure, morphology and sensory (ammonia) properties of films of PANI–SPS complexes were studied for the first time.

Self-assembly into tubular structures typically proceeds by helical winding of ribbon intermediates, however, only the central parts of the tubes, that retain no information on the ribbon geometry, have received attention so far. We propose the procedure of establishing the crystal structure of ribbons and ribbon-based tubes on the basis of crystallographic analysis of the tube-end geometry, where the terminal parts of the ribbons fold and form characteristic mono/bilayer polygonal shapes. The terminal parts of flattened J-aggregate nanotubes of trimethine cyanine dye were clearly resolved in electron microscopy and atomic force microscopy images, and the original parallelogram shape of ribbons was reconstructed and interpreted as a two-dimensional [1-10]/[010] facetted crystal with inclined molecular pi-stacks parallel to the long ribbon side. The back-reconstructed molecular orientations in a tube wall tend to be close to the tube normal. A two-stage "nucleation and growth" type model of the ribbon to tube transition is proposed that takes into account the established ribbon mechanical asymmetry. The model includes closure of the single ribbon loop as a nucleation event and explains, mostly observed in experiments, nearly rectangular shapes of tubes by the transition kinetics. Due to its universal character, the suggested approach can be applied to any ribbon-based tubes, regardless of their chemical composition.

Polymer composites based on poly(N,N′-bis-4-butylphenyl-N,N′-bisphenyl)benzidine (poly-TPD) with PCBM and copper(II) pyropheophorbide derivative (Cu-PP) were developed. In thin films of the poly-TPD and Cu-PP composites, the charge carrier mobility was investigated for the first time. In the ternary poly-TPD:PCBM:Cu-PP composite, the electron and hole mobilities are the most balanced compared to binary composites and the photoconductivity is enhanced due to the sensitization by Cu-PP in blue and red spectral ranges. The new composites are promising for use in the development of photodetectors.

The article represents a translated, revised, and updated excerpt from the book Electroluminescent Organic Light-Emitting Diodes Based on Metal Coordination Compounds, Rostov-on-Don: Yuzhn. Fed. Univ., 2015; ISBN 978-5-9275-1469-4 (see Additional Information). The main technological stages for manufacturing of laboratory samples for electroluminescence are described in general terms. The most popular laboratory techniques for the formation of thin semiconducting organic films, such as solution spin coating and vacuum thermal deposition, are considered in more detail. Some methodological approaches used in our laboratory are outlined. Measurements of the polymer layer thickness by the interference method and by atomic force microscopy are considered in detail. For the interference method, the principal sources of systematic errors are examined. Concerning atomic force microscopy (AFM), two techniques for measuring thickness are considered: the express technique (macro-needle scratching) and scratching with an AFM probe in contact mode. Systematic errors associated with the first technique are determined, followed by recommendations regarding its potential application. The last section highlights the necessary adjustment for calibrating thickness sensors during film deposition if the calibration is conducted based on macro-needle scratching results.

Stable nanosized germanium particles were synthesized in a liquid medium (acetone) by laser irradiation of single-crystal germanium plates under aerobic and anaerobic conditions at room temperature. Various experimental methods—optical spectrophotometry, atomic force microscopy, and dynamic light scattering—made it possible to detect stable nanosized Ge particles in acetone and record optical absorption and luminescence spectra depending on the time of laser irradiation in the presence and absence of oxygen. Particular attention is paid to the results of the effect of laser irradiation on the physicochemical properties of pure acetone.

The immobilization of N,N-diallyl-N,N-dimethylammonium chloride (DADMAC) on low-density polyethylene (LDPE) films was carried out by the method of postradiation grafting using x-ray radiation. The introduction of polycation exchanger links provided the appearance of hydrophilicity of the surface of the modified film. By measuring the wetting contact angle, IR and SEM, the island-type character of the coating from grafted polyDADMAC was detected. The death of Gram-negative bacteria Pseudomonas aeruginosa, Gram-positive bacteria Staphylococcus aureus, and yeast (eukaryotes) Yarrowia lipolytica on the surface of the film with grafted polyDADMAC was demonstrated.

The article represents a translated, revised, and updated excerpt from the book Electroluminescent Organic Light-Emitting Diodes Based on Metal Coordination Compounds, Rostov-on-Don: Yuzhn. Fed. Univ., 2015; ISBN 978-5-9275-1469-4 (see Additional Information). The measurement of performance characteristics of organic light-emitting diodes (OLEDs), including current–voltage, luminance–voltage, and spectral characteristics is described in detail in relaton to the laboratory measuring facility existing at the Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences. A detailed description of this setup, including the essential minimum set of instruments required for characterizing OLEDs, can serve as a guide for researchers embarking on experiments in the field of electroluminescence. The second part of the article describes the principal limiting factors for OLED efficiency.

Cu (II) protoporphyrin Cu-PP-IX and chlorin Cu-C-e6 were found to have both thin solid film formation and charge carrier transport abilities. In the layers deposited by resistive thermal evaporation, the mobilities of holes and electrons are on the order of 10−5 cm2 V−1 s−1. Organic light-emitting diodes incorporating the dye molecules as emitting dopants demonstrate electroluminescence in the UV and near-IR ranges.

Using palladium-catalyzed Suzuki polycondensation, we synthesized new light-emitting fluorene copolymers containing the dicyano derivatives of stilbene and phenanthrene and characterized them by gel permeation chromatography, UV-vis absorption spectroscopy, spectrofluorimetry, and cyclic voltammetry. The photoluminescence spectra of the synthesized polymers show significant energy transfer from the fluorene segments to the dicyanostilbene and 9,10-dicyanophenanthrene units, which is in agreement with the data of theoretical calculations. OLEDs based on these polymers were fabricated with an ITO/PEDOT-PSS (35 nm)/p-TPD (30 nm)/PVK (5 nm)/light emitting layer (70–75 nm)/PF-PO (20 nm)/LiF (1 nm)/Al (80 nm) configuration. Examination of their electroluminescence revealed that copolymers of fluorene with dicyanostilbene show yellow-green luminescence, while polymers with 9,10-dicyanophenanthrene have a greenish-blue emission. The 9,10-dicyanophenanthrene units have a more rigid structure compared to dicyanostilbene and, in OLEDs based on them, an increase in maximum brightness is observed with an increase in the content of the additive to the polymer chain. In particular, the device using fluorene copolymer with 9,10-dicyanophenanthrene (2.5 mol%) exhibited a maximum brightness of 9230 cd/m2 and a maximum current efficiency of 3.33 cd/A.

The structures of J -aggregates of two monomethine dyes are compared at the meso- and nanoscale by using fluorescence and atomic force microscopy. The J -aggregates of the two dyes are found to have solely a monolayer structure and to be polymorphic. Morphologically, monolayers represent narrow skew-symmetric strips and symmetric rhombi in the case of the first and the second dyes. The second morphological type is the tubular type in both cases. For monolayers of both dyes, atomic force microscopy imaging at the ultimate resolution reveals the presence of a quasi-one-dimensional substructure consisting of densely packed nanostrips with a width in the range of 7–10 nm. The nanostrips are interpreted as building blocks emerging at early stages of monolayer crystallization that proceeds via a nonclassical multistep mechanism.

The effect of addition of J -aggregates of polymethine dye into the hole-transport layer of an organic light-emitting diode (OLED) on its characteristics and operational stability was studied. Water-soluble PEDOT:PSS (poly(3,4-ethylenedioxythiophene)) and the interpolymer complex of polyaniline and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAn-PAMPSA) were used as the matrices of polymer nanocomposites. The highest efficiency characteristics of the OLEDs with the considered structure were achieved using PAn-PAMPSA at a particular component ratio in the interpolymer complex. Additives of J ‑aggregates did not significantly affect the efficiency characteristics of the OLEDs; however, an increase in the operational stability of devices was recorded.

Three new benzothiadiazole (BTD)-containing luminophores with different configurations of aryl linkers have been prepared via Pd-catalyzed cross-coupling Suzuki and Buchwald–Hartwig reactions. Photophysical and electroluminescent properties of the compounds were investigated to estimate their potential for optoelectronic applications. All synthesized structures have sufficiently high quantum yields in film. The BTD with aryl bridged carbazole unit demonstrated the highest electrons and holes mobility in a series. OLED with light-emitting layer (EML) based on this compound exhibited the highest brightness, as well as current and luminous efficiency. The synthesized compounds are not only luminophores with a high photoluminescence quantum yield, but also active transport centers for charge carriers in EML of OLED devices.

New unsymmetrically substituted benzothiadiazoles were synthesized from 4,7-dibromo-2,1,3-benzothiadiazole via the sequence of Pd-catalyzed Suzuki and Buchwald–Hartwig cross-coupling reactions with 4-methoxyphenylboronic acid and heterocyclic amines, respectively. Based on initially performed photophysical study as well as DFT calculation, these compounds, in particular with dibenzoazepine core, can be selected as promising scaffolds for further fine-tuning of their properties to be used in optoelectronics including OLED technologies.

(`)Application of back-scattering geometry in Raman spectroelectrochemistry of laser-absorbing polymer films on reflective metallic electrodes results in different degrees of doubling of excitation (by the incident and reflected beams) of the electrode/film/solution interfaces. Taking this into account, this method was first applied to study in situ galvanostatic polymerization of aniline on Pt-electrode in aqueous solutions of polymeric sulfonic acids distinguished by different rigidity of the main chain. Firstly, it was found that 532 nm laser radiation caused fluorescence in the solutions of phenyl-containing polyacids resulted in the Raman spectrometer overload. One can reduce fluorescence by increasing the incident angle of the laser beam on the electrode up to 20 degrees (perpendicular direction is taken as 0 degrees). Secondly, some of the polyacids were found to have intensive Raman bands in the range of characteristic Raman frequencies (1000-1800 cm(-1)) of polyaniline (PANI). In this case, subtraction of the solution background spectrum before starting the electropolymerization monitoring causes appearance of ever-growing negative Raman signals as the laser-absorbing PANI film grows on the reflective electrode. The above two issues are due to the double excitation of the thin solution layer before the electrode by the incident and reflected laser beams, the degree of this doubling decreasing as (1) the incident angle is increased and (2) the PANI film thickness grows. The distortive influence of the solution Raman spectrum on the real shape of PANI spectrum may be estimated and diminished by using the amplitude of ever-growing negative Raman signal in the area of water O-H vibration (near 3440 cm(-1)) as a measure of the ever-decreasing reflectance of the working electrode. Using the developed approach, it was shown that evolutions of the relative portions of the imine nitrogen (near 1490 cm(-1)) and the radical-cation nitrogen (near 1340 cm(-1)) fragments in the Raman spectra of PANI recorded in the course of electropolymerization can be used as informative criteria for the explanation of the differences in the aniline polymerization rate in the presence of polyacids of different chemical structure. (C) 2020 Elsevier B.V. All rights reserved.

Abstract—J-aggregates of a carbocyanine dye (pyridinium salt of 3,3'-di-(γ-sulfopropyl)-4,5,4',5'-di(tieno-3'',2'')-9‑ethyl-tiatrimethine cyanine betaine) (CC) were studied via the high-resolution AFM method at the mesoscale and nanoscale. They were found to exist in two structurally different polymorphic forms of single layers and fibrils. The class of single-layer J-aggregates consists of irregular micron sheets and giant submicron tubes, whose structure is identical to tubular J-aggregates of other cyanine dyes. The fibrillar J-aggregates are composed of 3-nm-high fibrils forming the networks owing to merging and branching, as well as of “elementary” fibrils with a height close to the molecular sizes of dye. Structural models of elementary fibril with molecular “staircase” and “ladder” stacking types were proposed as well.

A crystallographic analysis of the images of destruction fragments of tubular monomethine dye J -aggregates has been performed for the first time. It is shown that the formation of characteristic zigzag fragments is caused by the unwrapping of cylindrical surface on plane. Possible cleavage directions for the monolayer forming the tube walls are considered and an interrelation between the destruction products and molecular packing of this monolayer is established.