Papers by Volodymyr Nechytailo
Electrical conductivity and photon emission, as well as electron emission from carbon nanotubes, ... more Electrical conductivity and photon emission, as well as electron emission from carbon nanotubes, have been studied under the passage of current through them before and after their dispersion. It has been shown that the dispersion changes properties of Cnanotubes and causes the appearance of electron and photon emissions in the voltage region, where the conduction currentvoltage characteristic becomes superlinear. There is a maximum in the photon emission spectrum (λ ≈580 nm), which differs from the Planck black-body radiation spectrum registered for the initial C-nanotubes. The model of hot electrons has been proposed to explain the mechanism of electron and photon emissions.
Ukrainian Journal of Physics, 2018
We report on the optical and structural characterization of the two-component vacuum deposited (V... more We report on the optical and structural characterization of the two-component vacuum deposited (VD) rubrene (Rub)-Alq3 films. As is known, Rub-doped OLED active materials demonstrate both promising electroluminescence and transistor characteristics. However, in terms of operational lifetime, the Rub practical application in basic devices has a few draw-backs related to its chemical instability. Our main attention was focused on the role of the Alq3 coverage and the isomeric transformation of a Rub molecule on its chemical stability in these structures. By monitoring the evolution of PL emission in time, we found that the Rub degradation in Rub-Alq3 films is slower than that in vacuum-deposited Rub layers. These results demonstrate that the deposition of an Alq3 layer can be a way to enhance the stability of Rub to the photo-oxidation in optoelectronic devices. The Rub amorphous film crystallization at elevated temperatures in open air was observed for the first time.
Applied Physics Letters, 2014
It is shown that formation of fragments of the structures of massive transition metal cyanoferrat... more It is shown that formation of fragments of the structures of massive transition metal cyanoferrates in mesoporous molecular sieves of MCM-41 type containing high aluminum content does not cause important changes in the porous structures of the inclusion compounds. Over the last two decades considerable success has been achieved in the chemistry of inclusion compounds based on porous substances and "guest" molecules of various types; the characteristics of the synthesis, structure, the mutual effects of components, and the physico-chemical properties of inclusion compounds-zeolites with encapsulated transition metal complexes-have been studied in most detail [1, 2]. At the same time it is to be expected that differences should exist in the structures and mutual interactions of the components of inclusion compounds based on transition metal complexes and porous substances of other structural types, in particular mesoporous molecular sieves [3] which differ from zeolites in the first place by having considerably larger pores, an open structure and sufficient intracrystalline space for relatively large molecules. Such matrices permit the examination of the possibility of encapsulation in the porous space of an assembly of "guest" molecules and also the construction of "guests" without any deformation of the skeleton of the "host." The present work is dedicated to a study of the possibility of forming transition metal hexacyanoferrates in aluminosilicate monogenetic molecular sieves of the MCM-41 type (MCM), and the investigation of characteristics of the structure and mutual interaction of the components in the inclusion compounds formed. Synthesis of MCM-41 aluminosilicates with high aluminum content (Si : Al = 8) was carried out according to [4] from a reaction mixture with the following molar composition 16.2SiO 2 : Al 2 O 3 : 5.4Na 2 O : 13.8CTMABr : 1767H 2 O (CTMABr = cetyltrimethylammonium bromide; hydrothermal synthesis at 423 K for 48 h; the samples obtained were washed with water, dried in air, and then calcined in air at 823 K for 6 h). Compounds Me 2+-MCM (Me = Ni, Cu, Co) were obtained by ion exchange in solutions of the corresponding salts (10-2 mol/L; 100 mL per g of sample, 24 h, 3 treatments). Interaction of Me 2+-MCM with a solution of K 4 [Fe(CN) 6 ] (10-2 mol/L; 100 mL per g of sample, 24 h) gave Fe(CN) 6 4 −-MeMCM-1; a second treatment with transition metal salt solutions followed by K 4 [Fe(CN) 6 ] gave Fe(CN) 6 4 −-MeMCM-2.
Functional Organic Structures with Neutral and Charge Electronic Excitations Transfer for Molecular Electronics
Molecular Crystals and Liquid Crystals, 2008
ABSTRACT Compounds possessing the predicted unidirectional excitation conductivity and metal-orga... more ABSTRACT Compounds possessing the predicted unidirectional excitation conductivity and metal-organic nanostructures based on them are fabricated and investigated. The unidirectional excitation transfer in these compounds is confirmed. Computer simulations of electronic excitations passing through a functional macromolecule are carried out. Spectral investigations confirm that adenosine-thymidine sequences are electronic excitation traps in the nucleotide-containing molecular systems [1]. The formation of a chain of progressively lower energy levels in chromophores along the molecular system predicts not only the unidirectional neutral excitation transfer, but the unidirectional charge carrier current as well. Diode-like VAC-characteristics for the metal-organic systems of gold islands connected by π-electron-containing molecules are observed experimentally.
FTIR spectroscopic and STM studies of vacuum deposited aluminium (III) 8-hydroxyquinoline thin films
Journal of Molecular Structure, 2004
FTIR spectroscopy and scanning tunneling microscopy (STM) were used to study the molecular organi... more FTIR spectroscopy and scanning tunneling microscopy (STM) were used to study the molecular organization and morphology of vacuum deposited (VD) thin films of tris (8-hydroxyquinoline) aluminum (Alq3) from metal-organic planar light-emitting ...
Structure and electrochromic properties of ferric aquapentacyanoferrate—a new analogue of Prussian blue
Electrochimica Acta, 1995
A new electrode material of ferric aquapentacyanoferrate (FAPCF) film was fabricated. Its structu... more A new electrode material of ferric aquapentacyanoferrate (FAPCF) film was fabricated. Its structure, optical, electrochemical and electrochromic properties were studied. In comparison with Prussian blue FAPCF exhibits a moderate contraction of the cubic lattice and a different texture of film. The maximum of optical absorption is shifted by 100 nm towards the long wavelength region for FAPCF relatively to Prussian
Structure and electroluminescent properties of planar nanocomposites consisting of metal island film and organics
SPIE Proceedings, 2004
ABSTRACT Electroluminescent (EL) properties of planar light-emitting nanocomposite structures bas... more ABSTRACT Electroluminescent (EL) properties of planar light-emitting nanocomposite structures based on gold island films and semiconducting organic polymers poly(p-pheny!enevinylene) (PPV) and aluminum oxyquinoline (the aluminium (III) 8-hydroxyquinoline complex, Alq3) were studied in 400-600 nm spectral range at room temperature. The chemical composition and structureof vacuum deposited PPV and Alq3 films were determined by IR spectroscopy. According to the obtained data, chemical composition of the deposited A1q3 films corresponds to the initial A1q3. The PPV film is formed of oligomers with smaller molecular weight, which are generated in the course of thermal evaporation in vacuum due to decomposition of initial polymer. It was shown that EL spectra of the nanocomposites consist of two bands, one of them being typical of organic molecules, whereas the second one is related to the luminescence of the island film. Therefore, the obtained planar nanocomposite systems can be used as light emitting structures with controllable electroluminescent properties.
Ukr. J. Phys., 2018
We report on the optical and structural characterization of the two-component vacuum deposited (V... more We report on the optical and structural characterization of the two-component vacuum deposited (VD) rubrene (Rub)-Alq3 films. As is known, Rub-doped OLED active materials demonstrate both promising electroluminescence and transistor characteristics. However, in terms of operational lifetime, the Rub practical application in basic devices has a few drawbacks related to its chemical instability. Our main attention was focused on the role of the Alq3 coverage and the isomeric transformation of a Rub molecule on its chemical stability in these structures. By monitoring the evolution of PL emission in time, we found that the Rub degradation in Rub-Alq3 films is slower than that in vacuum-deposited Rub layers. These results demonstrate that the deposition of an Alq3 layer can be a way to enhance the stability of Rub to the photo-oxidation in optoelectronic devices. The Rub amorphous film crystallization at elevated temperatures in open air was observed for the first time.
Among organic semiconductors, rubrene (C42H28, 5,6,11,12-tetraphenyltetracene, Rub) is extensivel... more Among organic semiconductors, rubrene (C42H28, 5,6,11,12-tetraphenyltetracene, Rub) is extensively studied in recent years, since it exhibits interesting physical properties such as very high charge carrier mobilities in organic field-effect transistors at room temperature. Rub is used as a laser dye and as a fluorescent dopant in other organic light-emitting diodes (OLEDs) to improve the characteristics such as lifetime, stability, color, and brightness. However, there are controversies as to the Rub degradation both in the bulk state and thin layers. So, the better understanding of these phenomena is crucial for improving the performance of organic devices. In this work, we present the results on complex studies of the molecular structure, morphology, and photoluminescence (PL) of Rub layers deposited on freshly cleaved KBr(100) and Au(111) substrates by vacuum thermal evaporation. Additionally, the two-component vacuum deposited (VD) Rub-tetracene (Tc) films were studied. Special attention was paid to the susceptibility of films to the oxidation under ambient conditions. The chemical structure and molecular ordering in the obtained VD thin organic films were evaluated by FTIR spectroscopy, and the structure of the very first Rub layers on atomically smooth Au(111) surfaces was studied with scanning tunneling microscopy (STM). From the changes in the peaks position and the intensity of room-temperature PL spectra of the films with time, the degradation kinetics of the Rub emission is analyzed. K e y w o r d s:
The molecular structure, morphology, and electrical conductivity of thin tetracene layers obtaine... more The molecular structure, morphology, and electrical conductivity of thin tetracene layers obtained by the thermal vacuum de-position have been studied with the help of FTIR spectroscopy and STM/STS techniques as well. It has been shown that this preparation method does not change the tetracene molecular structure. The tetracene thin layers on the atomically smooth pyrolytic graphite surface demonstrate an amorphous structure. The local current-voltage characteristics (CVC) measured for tetracene films ∼ 10 monolayers thick show a well-defined asymmetry relative to a tunnel voltage. A study of the electrical conductivity and the electrolumines-cence (EL) of a planar composite consisting of gold island films and tetracene layers has revealed that EL from submicron lumi-nescent centers is observed on a superlinear section of conduction current I–V curves. The EL intensity grows with increasing voltage and becomes maximal at the CVC saturation. It is found that the EL from the nanocomposite has a 560-nm wavelength emission maximum.
Electrical conductivity and photon emission, as well as electron emission from carbon nanotubes, ... more Electrical conductivity and photon emission, as well as electron emission from carbon nanotubes, have been studied under the passage of current through them before and after their dispersion. It has been shown that the dispersion changes properties of C-nanotubes and causes the appearance of electron and photon emissions in the voltage region, where the conduction current-voltage characteristic becomes superlinear. There is a maximum in the photon emission spectrum (λ ≈580 nm), which differs from the Planck black-body radiation spectrum registered for the initial C-nanotubes. The model of hot electrons has been proposed to explain the mechanism of electron and photon emissions.
Applied Physics Letters, 2014
A method of preparation of a linear close-packed array of point-like light sources based on a nan... more A method of preparation of a linear close-packed array of point-like light sources based on a nanocomposite of gold nanoparticles and tetracene is proposed. Ordered system of microleads to the light sources with packing density up to 1000 mm-1 consists of linear conducting chains of cobalt nanoparticles self-assembled in a magnetic field. The electroluminescence from the gold-tetracene nanocomposite occurs in the visible range typical of organic light-emitting field-effect transistors based on tetracene. A theoretical substantiation of the possibility of excitation of tetracene molecules by hot electrons emitted from the gold nanoparticles is suggested and compared with other possible physical mechanisms.
Journal of Molecular Structure, 2004
FTIR spectroscopy and scanning tunneling microscopy (STM) were used to study the molecular organi... more FTIR spectroscopy and scanning tunneling microscopy (STM) were used to study the molecular organization and morphology of vacuum deposited (VD) thin films of tris (8-hydroxyquinoline) aluminum (Alq3) from metal-organic planar light-emitting nanocomposites consisting of gold island films and VD Alq3 film. It was found that thermal evaporation in vacuum does not cause dissociation of Alq3, and that the obtained films are essentially amorphous. Reflection-absorption (RA) IR spectra show predominantly perpendicular orientation of quinoline groups of Alq3 molecules in the films towards the substrate. With the STM method, a thickness-dependent structure of the films was found and the first near-surface layers of Alq3 films were characterized. It has been revealed that VD deposited Alq3 films of small thickness (5–15 nm) consist of molecular domains with a particular orientation along the Au[112] direction.
Functional Organic Structures with Neutral and Charge Electronic Excitations Transfer for Molecular Electronics
Mol. Cryst. Liq. Cryst., 2008
Compounds possessing the predicted unidirectional excitation conductivity and metal-organic nanos... more Compounds possessing the predicted unidirectional excitation conductivity and metal-organic nanostructures based on them are fabricated and investigated. The unidirectional excitation transfer in these compounds is confirmed. Computer simulations of electronic excitations passing through a functional macromolecule are carried out. Spectral investigations confirm that adenosine-thymidine sequences are electronic excitation traps in the nucleotide-containing molecular systems. The formation of a chain of progressively lower energy levels in chromophores along the molecular system predicts not only the unidirectional neutral excitation transfer, but the unidirectional charge carrier current as well. Diodelike VAC-characteristics for the metal-organic systems of gold islands connected by p-electron-containing molecules are observed experimentally.
Mol. Cryst. Liq. Cryst., Vol. 496, pp. 39–50, 2008
DOI: 10.1080/15421400802451360
Formation of Transition Metal Cyanoferrates in Mesoporous Molecular Sieves of the MCM-41 Type
Theoretical and Experimental Chemistry, 2000
It is shown that formation of fragments of the structures of massive transition metal cyanoferrat... more It is shown that formation of fragments of the structures of massive transition metal cyanoferrates in mesoporous molecular sieves of MCM-41 type containing high aluminum content does not cause important changes in the porous structures of the inclusion compounds.
Theoretical and Experimental Chemistry (2000) 36: 295.
doi:10.1023/A:1005234814644
Structure and electrochromic properties of ferric aquapentacyanoferrate—a new analogue of Prussian blue
Electrochimica Acta, 1995
A new electrode material of ferric aquapentacyanoferrate (FAPCF) film was fabricated. Its structu... more A new electrode material of ferric aquapentacyanoferrate (FAPCF) film was fabricated. Its structure, optical, electrochemical and electrochromic properties were studied. In comparison with Prussian blue FAPCF exhibits a moderate contraction of the cubic lattice and a different texture of film. The maximum of optical absorption is shifted by 100 nm towards the long wavelength region for FAPCF relatively to Prussian blue.
Electrochimica Acta
Volume 40, Issue 15, October 1995, Pages 2501-2504
Thesis Chapters by Volodymyr Nechytailo
Nechytaylo V. B. Optical and Electrochemical Properties of Structures with Variable Composition ... more Nechytaylo V. B. Optical and Electrochemical Properties of Structures with Variable Composition and Valency on the base of transition metal oxides and cyanoferrates. - Manuscript.
Thesis for Candidate's Degree in Physics and Mathematics on the Speciality 01.04.07 - Solid State Physics. Institute of Physics of NAS of Ukraine, Kyiv, 2004.
The results of experimental studies of the structure, optical and electrochemical properties of the ferric, cobalt, nickel, cupric aquapentacyanoferrates and tungsten trioxide are reported. A new approach for a modification of composition and properties of ferric hexacyanoferrate (FHCF)-like compounds has been developed. Electrochromic effect in ferric aquapentacyanoferrate (FAPCF) films has been discovered and studied. The suggestion on the reasons of the differences in the electrochromic behavior of FAPCF and FHCF has been made. The formation of the nanostructures of cobalt, nickel, cupric hexa- and aquapenta- cyanoferrates inside mesoporous MCM-41 template is shown. Factors that control the response time and cycle life of tungsten trioxide electrochromic devices are investigated. A new electrochromic device, in which the great stability of tungsten trioxide film is ensured, has been developed.
Key words: electrochromic effect, tungsten trioxide, Prussian blue, thin films, porous materials, nanostructures, MCM-41.
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Papers by Volodymyr Nechytailo
Mol. Cryst. Liq. Cryst., Vol. 496, pp. 39–50, 2008
DOI: 10.1080/15421400802451360
Theoretical and Experimental Chemistry (2000) 36: 295.
doi:10.1023/A:1005234814644
Electrochimica Acta
Volume 40, Issue 15, October 1995, Pages 2501-2504
Thesis Chapters by Volodymyr Nechytailo
Thesis for Candidate's Degree in Physics and Mathematics on the Speciality 01.04.07 - Solid State Physics. Institute of Physics of NAS of Ukraine, Kyiv, 2004.
The results of experimental studies of the structure, optical and electrochemical properties of the ferric, cobalt, nickel, cupric aquapentacyanoferrates and tungsten trioxide are reported. A new approach for a modification of composition and properties of ferric hexacyanoferrate (FHCF)-like compounds has been developed. Electrochromic effect in ferric aquapentacyanoferrate (FAPCF) films has been discovered and studied. The suggestion on the reasons of the differences in the electrochromic behavior of FAPCF and FHCF has been made. The formation of the nanostructures of cobalt, nickel, cupric hexa- and aquapenta- cyanoferrates inside mesoporous MCM-41 template is shown. Factors that control the response time and cycle life of tungsten trioxide electrochromic devices are investigated. A new electrochromic device, in which the great stability of tungsten trioxide film is ensured, has been developed.
Key words: electrochromic effect, tungsten trioxide, Prussian blue, thin films, porous materials, nanostructures, MCM-41.