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The effect of surface Fe-doping on the structural, photocatalytic, optical properties of polydisperse anatase and rutile TiO2 has been comprehensively studied. The TiO2 surface has been modified by Fe3+ ions through the adsorption from the diluted FeCl3 aqueous solutions. The prepared powders were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis, temperature programmed desorption techniques (TPD), Raman and UV–vis spectroscopy. With the adsorption isotherms of Fe3+ ions from FeCl3 aqueous solutions, it was found that adsorption of Fe3+ ions on the anatase surface is twice more efficient compared to that one on the rutile. The XRD and Raman spectroscopy measurements confirmed the monophase structure of the Fe-doped TiO2 with a subtle change in the lattice parameters and O/Ti ratio compared to the undoped counterparts. The red shift of the UV absorption edge has been registered for the Fe-doped anatase resulting in a significant decrease of its bandgap from 3.2 to 2.7 eV. The photocatalytic destruction of organic dye Safranin T over the prepared Fe-doped TiO2 under UV irradiation has been investigated. The influence of various energetically nonequivalent active sites on the surfaces of anatase and rutile on their photoactivity is considered.

The phase behaviour and structural organization of hydrogen-bonded liquid crystals were investigated under confinement to mesoporous molecular sieves. As such liquid crystalline compounds, 4 -hexylbenzoic and 4 -butylcyclohexanecarboxylic acids with different head group structure and alkyl chain length where selected and filled in the AlMCM-41 sieves. With FTIR spectroscopy it was found that some part of incorporated acid molecules, presumably located in the inner space of the AlMCM-41 pores, is in undissociated form of open dimers or chain associates and thus shows spectroscopic features characteristic to the bulk-like species. The other FTIR spectra components indicate strong interaction of the incorporated monomeric molecules with the pore surface. Two specific mechanisms are shown to be involved in molecular interactions at the interface: (1) deprotonation of monomeric acid molecules on the pore surface with formation of COO − carboxylate ions and (2) bonding of these ions to the pore surface by a coordinated bond R–COO − …Al + with Lewis acid sites. Differential scanning calorimetry revealed that these near-surface processes lead to complete suppression of mesomorphic properties of the studied acids under confinement to nanopores.

Solid phase complexes containing cetyltrimethylammonium bromide (CTAB) [H3C-(CH2)15-N+(CH3)3]Br− (cationic surfactant) and stearic fatty acid (SA) (H3C-(CH2)16-COOH) (anionic surfactant) were prepared with different SA:CTAB molar ratios ranging from 4:1 to 1:4. The prepared catanionic (CA) surfactants are characterized by using X-ray powder diffraction, DSC analysis, and temperature-variable FTIR spectroscopy. It is shown that the obtained CA complexes in the solid state are assembled into a phase-segregated layered structure. The aggregate composition is close to equimolar with the coexisting excessive SA or CTAB phase, which is confirmed by FTIR spectroscopy. Complicated phase behaviors depending on the SA:CTAB molar ratio are observed in these systems. Upon heating, a series of phase transitions occurs, yielding finally an orientationally disordered hexagonal structure. With DSC analysis, the greatly enhanced stability of the complexes (particularly, the 1:1 one) over pure acid (by about 40 ∘C) is found. The structural effects on the phase diagram and the molecular dynamics of SA:CTAB aggregates are discussed., З метою отримання нових перспективних молекулярних матерiалiв синтезовано та дослiджено катанiоннi речовини на основi комплексних з’єднань цетiлтриметiламмонiум бромiду (СТАВ) [H3C-(CH2)15-N+(CH3)3]Br− та стеаринової кислоти (SA) (H3C-(CH2)16-COOH) при молярних спiввiдношеннях компонент вiд 4:1 до 1:4. Дослiдження рентгенiвської дифракцiї показали, що у всiх випадках утворюється двофазна система, причому обидвi фази мають ламелярну структуру. Сформованi комплекси складаються iз катанiонної еквiмолярної складової (СТАВ:SA = 1:1) та надлишкової фази (СТАВ або SA), що пiдтверджується даними FTIR. На вiдмiну вiд вихiдних речовин в отриманих комплексах з ростом температури вiдбувається декiлька фазових переходiв в твердому станi, параметри яких залежать вiд спiввiдношення компонент. Сформованi комплекси (зокрема, еквiмолярна фаза) характеризуються пiдвищеною стабiльнiстю в порiвняннi iз чистою стеариновою кислотою. Обговорюється вплив структури та складу комплексiв на фазову дiаграму та молекулярну динамiку комплексiв CTAB + SA.

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., Дослiджено оптичнi та структурнi властивостi двокомпонентних плiвок рубрен-Alq3, одержаних методом вакуумного напорошення (ВН). Вiдомо, що допованi рубреном активнi матерiали для органiчних свiтловипромiнювальних дiодiв та транзисторiв демонструють покращенi електролюмiнесцентнi та електротранспортнi характеристики, але практичному застосуванню таких систем перешкоджає хiмiчна нестабiльнiсть рубрену, що скорочує експлуатацiйний термiн служби вiдповiдних пристроїв. В роботi дослiджено вплив захисного шару Alq3, а також наявностi рiзних iзомерiв молекули рубрену на його хiмiчну стабiльнiсть у двошарових тонкоплiвкових структурах. На основi експериментальних дослiджень спектрiв IЧ поглинання та часової еволюцiї спектрiв фотолюмiнесценцiї було показано, що процес фотодеградацiї (утворення перекису) рубрену у плiвках рубрен-Alq3 вiдбувається бiльш повiльно, нiж у тонких шарах самого рубрену. Результати свiдчать про те, що нанесення захисного шару Alq3 може бути засобом пiдвищення хiмiчної стiйкостi рубрену до фотоокислення у оптоелектронних приладах. Також нами вперше виявлено процес кристалiзацiї аморфної плiвки фотоокисленого рубрену пiд час ї ї високотемпературного вiдпалу, який супроводжуються вiдновленням первiсної хiмiчної структури молекули рубрену.

Nanocrystalline anatase ( A ) and rutile ( R ) TiO 2 were synthesized by the thermal hydrolysis and then were surface doped with Cr ions by adsorption. The samples were characterized by X-ray diffraction, X-ray fluorescence, Raman spectroscopy, optical absorption and photoluminescence (PL) methods. It is found that the PL emission and optical absorption near the band gap edge occur with the same electronic transitions in TiO 2 . The Cr 3+ doping leads to the blue and red shifts of the PL peaks in A /Cr TiO 2 due to the Burstein–Moss and band tailing effects, respectively. The Auger type non-radiative recombination in R /Cr TiO 2 quenches the PL emission intensity. For anatase samples at low concentrations of Cr ions (0.5 at%) the PL emission increases compared to the undoped A TiO 2 due to the formation of additional radiative recombination centers. At higher contents of Cr (1.0 at%), the PL intensity decreases due to the concentration quenching effect.

Titanium dioxide (TiO2) nanocrystalline powders were prepared by the thermal hydrolysis method in the form of pure anatase or rutile and were investigated by X-ray diffraction, X-ray fluorescence, FT-Raman spectroscopy, optical absorption, and photoluminescence (PL) methods. PL spectra were studied under the intense UV laser excitation at 337.1 nm (3.68 eV) at room temperature. Some interesting features in the PL spectra including the well-resolved peaks of excitonic and band-band transitions in TiO2 were observed for the first time. It is shown that PL bands with peaks at 2.71–2.81 eV and its phonon replicas in anatase and rutile TiO2 arise from the excitonic e− − ℎ+ recombination via oxygen vacancies. The excitonic peak at 2.91 eV is attributed to the recombination of self-trapped excitons in anatase or free excitons in rutile TiO2. The PL peaks within 3.0–3.3 eV in anatase TiO2 are ascribed to indirect allowed transitions due to the band-band e− − ℎ+ recombination. The peaks at 3.03 and 3.26 eV are attributed to the free exciton emission near the fundamental band edge of rutile and anatase TiO2, respectively., Оптичне поглинання i фотолюмiнесценцiя дiоксиду титану TiO2 вивчалися при кiмнатнiй температурi. Нанокристалiчнi порошки TiO2 були синтезованi зi структурою чистого анатазу або рутилу. Зразки було дослiджено методами рентгенiвської дифракцiї, рентгенiвської флуоресценцiї, спектроскопiї комбiнацiйного розсiювання свiтла, оптичного поглинання i фотолюмiнесценцiї (ФЛ). Спектри ФЛ дослiджувалися при iнтенсивному УФ (3,68 еВ) збудженнi N2 лазером. Деякi цiкавi особливостi в спектрах ФЛ, в тому числi пiки екситонних i мiжзонних переходiв в TiO2 з високим спектральним роздiленням, спостерiгалися, за нашими даними, вперше. Показано, що смуги ФЛ, в тому числi пiки при 2,71–2,81 еВ, i їх фононнi повторення в спектрах анатазу i рутилу TiO2 виникають внаслiдок екситонної e− − ℎ+ рекомбiнацiї поблизу кисневих вакансiй. Екситонний пiк при 2,91 еВ вiднесено до рекомбiнацiї автолокалiзованих екситонiв в анатазi або вiльних екситонiв в рутилi TiO2. Пiки ФЛ у межах 3,0–3,3 еВ в анатазi TiO2 приписано до непрямих дозволених переходiв внаслiдок зона-зона e−−ℎ+ рекомбiнацiї. Пiки при 3,03 еВ i 3,26 еВ вiднесено до емiсiї вiльних екситонiв поблизу фундаментального краю поглинання рутилу i анатазу TiO2 вiдповiдно. Обговорено вплив кристалiчної структури TiO2 на спектри ФЛ.

The optical absorption and photoluminescence of anatase and rutile TiO2 were studied at room temperature. TiO2 nanocrystalline powders were synthesized in the form of pure anatase or rutile. The samples were characterized by X-ray diffraction, X-ray fluorescence, Raman spectroscopy, optical absorption and photoluminescence (PL) methods. The PL spectra were studied under the intensive UV (3.68 eV) laser excitation. Some interesting features in the PL spectra including the well-resolved peaks of excitonic and band–band transitions in TiO2 were observed, to our knowledge, for the first time. It is shown that PL bands including peaks at 2.71–2.81 eV and its phonon replicas in anatase and rutile TiO2 arise from the excitonic e−−h+ recombination via oxygen vacancies. The excitonic peak at 2.91 eV is attributed to the recombination of self-trapped excitons in anatase or free excitons in rutile TiO2. The PL peaks within 3.0–3.3 eV in anatase TiO2 are ascribed to indirect allowed transitions due to the band–band e−−h+ recombination. The peaks at 3.03 eV and 3.26 eV are attributed to the free exciton emission near the fundamental band edge of rutile and anatase TiO2, respectively. The influence of TiO2 crystal structure and calcination temperature on the PL spectra is discussed.

The effect of nanocrystalline TiO2 doping with transition metal cations (Cu2+, Fe3+, Co2+, Cr3+) on their optical absorption and photocatalytic properties was investigated. The obtained metal-doped TiO2 samples were characterized by X-ray diffraction, scanning electron microscopy, and UV–vis absorption spectroscopy. It is shown that doping effect on anatase (A) and rutile (R) properties is quite different, being much stronger and complicated on A than on R. Contrary to doped R, doped A revealed a significant red shift of the absorption edge along with the band gap narrowing. Photocatalytic activity of anatase increases upon doping in the order: A R/Co>R/Cu>R/Fe>R/Cr, indicating the inhibitory effect of impurity cations. This fact correlates with the decrease in the UV absorption of the doped rutile in the region of the Hg-lamp irradiation at 4.88 eV.

Fourier transform infrared (FTIR) spectroscopy and scanning tunneling microscopy (STM) were used to study the molecular organization and morphology of vacuum-deposited tetracene layers. FTIR and optical measurements confirm that tetracene molecules are not dissociated during vacuum thermal deposition. With STM imaging, a highly ordered, closely packed, lamella-like structure of tetracene monolayer film on the Au(111) surface was observed. Electroluminescence from the nanocomposite consisting of Au nanoparticles and tetracene film is concentrated within submicron luminescent centers and occurs at voltages of 4–5 V in a superlinear section of conduction current–voltage curves. The results can be useful for the design of planar light-emitting devices.

Nanocrystalline titanium–manganese mixed oxides (TMMO) with Mn content of 13–16 at.% were first synthesized by manganese hydroxide precipitation on anatase or rutile particles. The structure, morphology and chemical composition of the samples were characterized using XRD, SEM, EDS and XRF methods showing that the synthesized mixed oxides are polydisperse materials of different phase compositions containing TiO 2 , Mn 2 O 3 and MnTiO 3 . The defect structure and phase formation of the prepared compounds were characterized by FTIR, FT-FIR, FT-Raman spectroscopies. UV–vis absorption spectra were investigated in 2.4–6.0 eV region and revealed that compared with pure TiO 2 the presence of manganese oxides results in an increase of the absorption intensity and significant red shift of the TMMO absorption edge. Photocatalytic activity of pure TiO 2 , Mn 2+ -doped TiO 2 and TMMO during the photocatalytic decomposition of the safranine dye under UV irradiation was studied. A great improvement of photocatalytic activity is registered for Mn 2+ -doped TiO 2 (anatase and rutile), and rutile-based TMMO sample.

Structural and thermal properties of a solid-state binary mixture of long-chain cationic and anionic surfactants (so-called catanionic complexes) composed of cetyltrimethyl-ammonium bromide, [H3C–(CH2)15–N+(CH3)3]Br−(CTAB), and saturated fatty acid (FA), CH3(CH2)12COOH (lauric acid, kC12), are studied. To clarify the effect of intermolecular interactions on the crystalline structure and phase transitions in this class of supramolecular compounds, the 1 : 1 kC12-CTAB binary mixture is investigated by means of X-ray diffraction, differential scanning calorimetry (DSC), and temperature-variable Fourier transform infrared spectroscopy (FTIR). Based on the comparison of the obtained results with those of other CTAB-FA binary mixtures with different alkyl chain length mismatches, the possible molecular packing in the crystal phase of CTAB-FA complexes and the mechanism of successive phase transitions in the condensed state are proposed., Проведено комплексне дослiдження структурних та термiчних властивостей твердотiльних бiнарних сумiшей довголанцюжкових катiонних i анiонних поверхнево-активних сполук (так званих катанiонних комплексiв), що складаються з бромiду цетилтриметиламмонiю, [H3C(CH2)15-N+(CH3)3]Br−(ЦТАБ), та насичених жирних кислот (ЖК), зокрема CH3(CH2)12COOH (лауринова кислота, kC12). Для з’ясування впливу мiжмолекулярної взаємодiї на особливостi кристалiчної структури та фазових переходiв у цьому класi супрамолекулярних сполук, в представленiй роботi ми придiлили особливу увагу дослiдженню бiнарної сумiшi 1 : 1 кС12-ЦТАБ за допомогою методiв рентгенiвської дифракцiї, диференцiальної скануючої калориметрiї (ДСК) та iнфрачервоної спектроскопiї з перетворенням Фур’є у широкому iнтервалi температур (20–150 ∘С). На пiдставi порiвняння отриманих результатiв з одержаними нами ранiше для iнших бiнарних сумiшей ЦТАБ з ЖК з бiльш довгими алкiльними ланцюжками, запропоновано можливу молекулярну упаковку в кристалiчнiй структурi комплексiв ЖК-ЦТАБ та встановлено механiзм послiдовних фазових переходiв у конденсованому станi таких сполук.

The fluorescence of samples of porous silicon of various morphologies that are filled with a liquid crystal (LC), n-pentyl-n′-cyanobiphenyl (5CB), is studied. The fluorescence spectra of the sample, along with the long-wavelength band of porous silicon with a maximum in the range 627–667 nm, exhibit a short-wavelength band of 5CB with a maximum in the range 385–410 nm. The radiative relaxation times of porous silicon and 5CB lie in the micro- and nanosecond ranges, respectively. It is found that the filling of pores with 5CB enhances the fluorescence of porous silicon by two to three times. This enhancement is caused by non-radiative energy transfer from 5CB to the porous matrix as a result of efficient interactions between LC molecules and pore walls. Using IR spectroscopy, it is shown that the formation of hydrogen bonds between cyano groups of 5CB molecules and silanol groups of pore surface is the predominant type of these interactions. A transfer mechanism is suggested according to which excited associates of 5CB molecules transfer their energy via surface channels to excitons of porous silicon, enhancing its fluorescence.

The phase transitions, intermolecular interactions and electrical percolation behavior in the composites of multiwalled carbon nanotubes (MWNTs) and nematic LC ( p -ethoxybenzylidene- p ′-butylaniline, EBBA) are experimentally investigated in this work. The concentration of nanotubes was between 0 and 1% (wt), and the temperature interval was 273–363 K. The experimental data of differential scanning calorimetry (DSC) and FTIR adsorption spectra evidence the presence of strong interactions inside MWNTs/EBBA nanocomposites. An increase of both isotropic-to-nematic (by 0.5-1 K) and nematic-to-crystalline (by 1.5-3 K) phase transition temperatures was observed for EBBA filled with MWNTs. The FTIR spectroscopic data evidence an enhancement of the strong binding interaction between MWNTs and EBBA with increase of the concentration of MWNTs. It was shown that intermolecular interactions affect noticeably the electrical conductivity of MWNTs/EBBA composites. The percolation transition from non-conductive to high conductive state, and the effect of positive temperature coefficient (PTC effect) were observed at MWNT concentrations exceeding 0.05-0.1 wt.% Within the nematic phase temperature range, the electrical conductivity of the composites reveals a noticeable heating–cooling hysteresis and follows Arrhenius behavior. The activation energy decreases when MWNTs concentration increases, which supports the dominating role of the junction mechanism related to the thermal motion of nanotubes. The electric field dependence of the electrical conductivity was explained by the existence of the field-enhanced charge transport through hopping junctions in the LC gaps.

Montmorillonite (MMT) clay modified with octadecylbenzyldimethylammonium chloride (OBDM), B2, and its composites with nematic liquid crystal (LC) 4‐pentyl‐4′‐cyanobiphenyl (5CB), 5CB–B2, with different concentration of the clay (3–8 wt %) were investigated by X‐ray diffraction, polarizing optical microscopy, differential scanning calorimetry, FTIR spectroscopy and atomic force microscopy. Modification of Na‐MMT with OBDM surfactant results in an increase of the chemical affinity of the clay for 5CB. This results in considerable increase of the basal spacings of the clay, giving a possibility for 5CB dimers to penetrate into the interlayer space. Better affinity of the clay for LC allows clay nanoparticles to disperse homogeneously in the LC, and affects thermodynamic and optical properties of the nanocomposites. For 5CB–B2 composites, the structure formation and the strength of the interface interactions were practically independent on B2 concentration. A comparison with 5CB–B3 composites (B3 is MMT modif...

FTIR spectroscopy, atomic force microscopy (AFM) and electro-optical measurements were used to study nanocomposites consisting of nematic liquid crystal (LC) ZLI-2293 and organophilic montmorillonite (MMT) nanoparticles. The initial MMT was modified by two different surfactants: octadecylbenzyldimethylammonium chloride (OBDM) and dioctadecylldimethylammonium chloride (DODM). According to spectroscopic results, Van der Waals interactions between the components of the LC/clay composites are stronger in OBDM-MMT case. AFM images of two types of the LC/clay nanocomposites showed different morphology consisting of large-scale structures. Correlation between the spectroscopic results and electro-optical behaviour of the LC/clay nanocomposites was observed. It was inferred that the memory effect is more pronounced for composites with OBDM-MMT due to colloid network formation, whereas the electro-optical contrast is higher for DODM-MMT, where the clay particles are not organized in any ordered structure.

Molecular organization and morphology of vacuum deposited (VD) thin films of the europium complex of europium(dibenzoylmethanato) 3 (bathophenanthroline) (Eu(DBM) 3 bath) from metal-organic planar light-emitting nanocomposites consisting of gold island films and VD Eu(DBM) 3 bath film were investigated by FTIR spectroscopy and scanning tunneling microscopy (STM). It has been found that thermal evaporation in vacuum does not cause chemical decomposition of Eu(DBM) 3 bath, and that the obtained films are essentially amorphous. Reflection–absorption IR spectra show no predominant orientation of Eu(DBM) 3 bath molecules in the films with respect to the substrate. With the STM method, the morphology and structure of the near-surface layers of Eu(DBM) 3 bath films were characterized, and it was found that they consist of self-assembled molecular dimers closely packed along the Au [110] steps on the Au(111) terrace. With increase of the Eu(DBM) 3 bath film thickness, the ordered structure is lost.

We have investigated the temperature dependences (in the 4.2–180 K range) of the phosphorescence spectra of benzophenone (BP) in the presence of nanodisperse particles of the clay mineral montmorillonite (MMT) modified by different surface-active substances: dioctadecyldimethylammonium (DODM) and octadecylbenzyldimethylammonium (OBDM) chlorides. The MMT-OBDM sample has a stronger affinity for the given organic medium (BP) in the composite compared to the MMT-DODM sample due to the presence of a benzyl radical in the composition of the first modifier molecule. It has been shown that in the investigated heterosystems BP is present in both the crystal phase and the amorphous phase, and the latter thereby is formed in the near-surface layers of nanoparticles in the form of a thin shell due to the disordering action of inorganic particles on their adjacent BP layers. An increase in the chemical affinity between the organic clay surface and the BP molecules promotes the relaxation processes in the amorphous films of BP and increases the decay rate of its phosphorescence.

The effect of montmorillonite (MMT) clay modification with surfactant cations on the electrooptical properties of the LC–clay nanocomposites consisting of MMT and 4-pentyl-4′-cyanobiphenyl (5CB) nematic liquid crystal was investigated depending on the composite preparation method. We showed that only composites consisting of MMT modified with organic surfactants (alkylbenzyldimethylammonium chlorides with alkyl chain length C14–C18) display electrooptical memory effect and contrast. Adding a polar additive (acetone) to the mixture during the composite preparation considerably improves the homogeneity of the composites and their electrooptical performance. Using IR and Raman spectroscopy methods it was shown that in the LC-organoclay composites mutual interaction between the components takes place, which results in alignment of the near-surface layers of both organic and inorganic components of the composite. Due to such interaction, these systems display electrooptical contrast and memory effect. The LC–clay composites consisting of organophobic Na-MMT do not display electrooptical effect because of the absence of interaction between the components, which is confirmed by the IR and Raman spectroscopy data.

The 127 I NQR, IR absorption and Raman spectra of impurity-doped and mixed lithium iodate Li 1− x H x IO 3 crystals grown from water solutions with different LiIO 3 /HIO 3 ratios were investigated depending on the content of the impurity hydrogen x . The NQR results suggested that, at small concentration of doping iodic acid x x 1− x H x IO 3 are formed.

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.

For getting more information about the behavior of hydrogen atoms in partially occupied sites in δ-KIO 3 ·HIO 3 , we have measured temperature-dependent infrared spectra of this crystal at 14–300 K in the spectral range of OH stretching and bending vibrations. It was found that ν (OH) band (centered at ∼2800 cm −1 ) has complicated profile which, at temperatures below 220 K, includes weak low-frequency satellites at its low-frequency slope. At 14 K, we have main peak ν (OH) at 2766, satellites at 2606, 2485, and 2387 cm −1 , and strong 2 δ (OH) overtone peak at 2274 cm −1 enhanced due to Fermi resonance. At the same time, the low-frequency slope of δ (OH) band (centered at 1189 cm −1 ) shows equidistant satellites separated with period of approximately 25 cm −1 . The observed features suggest anharmonic coupling between OH high-frequency vibrations and various low-frequency motions of the crystal lattice.

Two types of heterogeneous systems containing nitrobenzene (NB) as a filler (the first one is based on mesoporous molecular sieves of the MCM-41 type and the second one includes TiO 2 particles of different crystalline modifications—anatase and rutile) have been investigated by means of IR spectroscopy. The interactions of NB molecules with the surface active centers have been studied. According to obtained results the suggestion has been made that the possible mechanisms of molecular interactions in these complex systems are a creation of hydrogen bonds of –NO⋯HO–Al(Si) and –NO⋯HO–Ti types correspondingly.

Heterogeneous systems based on TiO 2 rutile powders and benzophenone (BP) as a dispersive medium have been investigated by Raman and IR spectroscopy. Rutile particles have been obtained by thermal hydrolysis of titanium tetrachloride hydrochloric acid solutions and subsequent temperature treatment at 573 K (Ru300) and 1173 K (Ru900). Loading with BP results in changes of TiO 2 polarizability. Porous and defective surface of Ru300 induces disordering to BP crystal which becomes glassy-like. BP molecules form hydrogen bonds with the TiO 2 surface active centers (Ti–OH) via phenyl ring π-electron systems. In adsorbing on TiO 2 particles, the BP displaces adsorbed water molecules. These changes in structure and molecular interactions are reflected in the corresponding Raman and IR spectra which allow to compare two heterogeneous systems (BP-Ru300 and BP-Ru900).

First observation of the effect of the pore surface treatment on molecular dynamics of novel nanocomposites based on aluminosilicate molecular sieves MeMCM-41 (Me=Mn, Co, Ni, Cu, Zn) trapped in pores of 4- n -pentyl-4′-cyanobiphenyl (5CB) nematogenic compound. The pore surface properties of the matrices with unidimensional hexagonal channels of about 4 nm in diameter were modified by incorporation of different transition-metal ions into silica-based framework of the sieves. Variable temperature (23–180 °C) FTIR spectroscopic (400–4000 cm −1 ) and calorimetric studies showed specific interactions between the 5CB molecules and surface active centers. In addition to previously reported interaction of some part of the 5CB molecules with surface hydroxyl groups (Bronsted acid sites) of the molecular sieve via H-bonds, some part of the 5CB molecules are coordinated to Me 2+ ions via semipolar –CN⋯Me 2+ bonds. This is evident from the appearance of new Q(CN) band shifted to the higher frequencies by 26–47 cm −1 against the frequency of Q(CN) band seen in the spectra of nematic 5CB depending on the Me 2+ cation. It was found that the frequency shift of this new band depends on the Me 2+ cation, and is proportional to the sum of two first ionization potentials of the transition metal, which determines the stability of the metal complexes in Irving–Williams raw. The nematic-to-isotropic phase transition seen in the bulk 5CB is absent in all studied MeMCM–5CB nanocomposites.

The paper deals with the investigation of IR absorption spectra of a pure 4- n -pentyl-4′-cyanobiphenyl (5CB) liquid crystal in nematic liquid crystalline (LC) state, pure aluminosilicate molecular sieves of MCM-41 type (with channels about 40 A in diameter) and their heterogeneous binary systems. It was shown that 5CB molecules are able to interact with active centers in the MCM-41 channels forming sufficiently strong hydrogen bonds of the —CN⋯H—O— type. This conclusion was confirmed by the data obtained from DSC measurements. Relative amount of the 5CB molecules interacting with the channel walls and that of the molecules retaining the LC state when encapsulated in molecular sieves MCM-41 and CuMCM-41 were estimated.

δ-KIO 3 ·HIO 3 , obtained by slowly cooling a concentrated solution of KIO 3 and HIO 3 , has been investigated by means of single crystal X-ray diffraction measurements at ambient temperature and temperature dependent powder X-ray diffraction, dielectric, calorimetric and FT–IR and FT-Raman measurements. From the single crystal X-ray measurements, the I–O bonding scheme of the iodine atoms and the hydrogen bond system were determined. The crystal structure of δ-KIO 3 ·HIO 3 was found to consist of [I 3 O 9 H 3/2 ] 3/2− ions possibly originating from occupationally disordered [I 3 O 9 H 2 ] − and [I 3 O 9 H] 2− anions. These ions are connected via hydrogen bonds to form plane grids parallel (100) with the K + ions placed between them. Thus δ-KIO 3 ·HIO 3 should be formulated as K 3/2 [I 3 O 9 H 3/2 ]. The temperature dependent FT–IR data give an evidence for a dynamic proton disorder at room temperature and for a proton ordering below 220 K, which may be regarded as a structural phase transition in the proton sublattice.

The ferroelectric crystal of ammonium iodate NH4IO3 was investigated by the methods of Raman and IR spectroscopy. Powder IR and Raman temperature dependent spectra of the title crystal were measured in the temperature range 300–400 K near the Curie temperature (Tc=367 K). The 127I nuclear quadruple resonance (NQR) spectra of the NH4IO3 crystal, which were measured in the same temperature range, are discussed. The effect of hindered rotation of NH4+ and IO3− ions was revealed in the pretransition temperature range and is explained by anomalous crystal thermal expansion.

Temperature-dependent structure modification of organised organic thin films (OOTF) built of sodium (NaSt) and lithium (LiSt) stearates was investigated by DSC and vibrational spectroscopy. Structural phases found for the bulk specimens of substances by DSC measurements, correspond to those previously known [1] . The pre-transitional structural changes observed for thin films in the first crystalline phase were investigated by using temperature dependent FTIR spectroscopy. Changes in orientation of stearate long axis and alkyl chain conformation in NaSt and LiSt thin films with temperature are reported. It was found that film heating from 20 up to 110°C leads to decrease of the tilt of alkyl radicals with respect to the surface for NaSt films. With temperature increasing, in the IR absorption spectra of NaSt and LiSt films, the frequency of methylene symmetric C-H stretching IR band change from 2849 to 2851 cm −1 upon the temperature variation in the range 70–90°C and at 100°C, respectively. This indicates the onset of partial melting of the chains at this temperatures which are lower as compared to those of bulk specimens. It is suggested that this may be caused by a peculiar structural organisation of the films near the substrate surface.

We propose a new approach to the band shape formation in crystals with strong symmetric hydrogen bonds. Our consideration is based on the assumption that the interaction between the incident light applied to the crystal and polarized optical photons is stronger than that between molecular excitations and the photons. In this case the formation of polaritons takes place and hence molecular excitations begin to interact with the polaritons. As a result, a new kind of correction to the absorption coefficient caused by the beam of the spectroscopic instrument appears. The complete band shape of the OH stretching band is computed. A comparison with the available experimental data is carried out.

FT-IR (4000-400 cm −1 ) and FIR (400-10 cm −1 ) spectra of α-modification of acid potassium iodate (α-KIO 3 ·HIO 3 ) were measured in the paraelectric (at 300-220 K) and ferroelectric (at 223-20 K) phases. FIR spectra of the ferroelectric phase were found to exhibit doublet structure of many bands while FT-IR spectra mainly remain invariable. The results are in good agreement with the order-disorder mechanism of ferroelectric phase transition connected with localization of the proton within a strong hydrogen bond.

Nanocrystalline titanium-manganese mixed oxides (TMMO) with Mn content of 13–16 at. % were first synthesized by manganese hydroxide precipitation on anatase or rutile particles. UV-vis absorption spectra were investigated in 2.4–6.0 eV region and revealed that compared with pure TiO 2 the presence of manganese oxides results in an increase of the absorption intensity and significant red shift of the TMMO absorption edge. Photocatalytic activity of pure TiO 2 , Mn2+ doped TiO 2 and TMMO during the photocatalytic decomposition of the safranine dye under UV irradiation was studied. A great improvement of photocatalytic activity is registered for Mn2+-doped TiO 2 (anatase and rutile), and rutile-based TMMO sample.

This paper presents the data of investigations of the structure and property changes of amorphous WO3 (a-WO3) films as a result of their interaction with the protonic electrolyte based on the H2SO4 aqueous solution by means of scanning electron microscopy (SEM), reflection of high energy electron diffraction (RHEED), optical and IR spectroscopy techniques. It is shown that the storage of a-WO3 films in the aqueous electrolyte leads to the formation of crystalline hydrates WO3·m(SO4)·n(H2O). The crystallization and hydratation of the a-WO3 films decrease considerably their electrochromic efficiency.

The lattice dynamics of pseudo-binary system LiIO 3 ·HIO 3 has been investigated by means of IR spectroscopy and NQR technique. It is shown that at compositions close to 0.2 ≤ x ≤ 0.34 mixed crystals Li 1-x H x IO 3 based on 2LiIO 3 ·HIO 3 are formed. The spectral changes observed in the 2600 and 400 cm −1 region indicate the formation of “intermolecular” hydrogen bondings between the components. The concentration phase transition to amorphous glass phase at x near 0.26 has been detected.

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.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In the present, photoluminescence of δ-KIO 3 HIO 3 crystals has been studied for the first time in the temperature range of 4.2-77K. It was shown experimentally that at T=4.2 K the edge of self-absorption band is located near 295 nm. In the luminescence spectra of the title crystal, two bands are found which differ in their spectral position and lifetime. The short-wave luminescence band centered at 367.5 nm. This band appears only in the csae of the crystal excitation by the light with the wavelength that does not fall in the region of self-absorption of the crystal, eg λexc = 340 nm. When the temperature increases from 4.2 to 34 K, the intensity of this band falls down almost to the background value, whereas the position of its maximum remains practically unchanged. The long-wave luminscence band of the δ-KIO 3 HIO 3 crystal with peak position at 410-420 nm and the lifetime of about 1 s is attributed to phosphorescence. This spectrum appears only in the case of excitation within the region of self-absorption of the crystal, eg λ3xc = 275 nm. On the basis of experimental data analysis, the assumption has been made that the short-wave band originates from the emission of excitons located at the defects of the crystal structure, and the long-wave band is related to radiation decay of autolocated bihalide excitons. Possible photoprocesses in the title crystal caused by light absorption of different wavelength are discussed.

IR spectra of polycrystalline δ-KIO3 HIO3 have been studied in the temperature range from 13 to 300 K. A systematic temperature dependent study has been performed for the hydrogen bond stretching and bending vibrations. Features observed in the high frequency region of vibrational spectra of the title crystal are discussed with respect to possible formation of new charge compensating protonic species in the proton sublattice.

Raman scattering and IR spectra of tungsten trioxide electrochromic amorphous thin films are studied to clarify structural changes caused by interaction with the aqueous electrolyte used in electrochromic cells. It is shown that exposure of amorphous films in the electrolyte leads to the formation of tungsten trioxide crystalline hydrates. The composition of formed crystalline hydrates varies in accordance with amount of adsorbed water and size of micropores in the film. Electrochromic efficiency of crystalline hydrates strongly decreases due to the induced by charge injection shift of the optical absorption band into infrared region of the spectrum.

Fourier transform infrared spectroscopy (FTIR) is applied to study photochemical transformations in poly(p-methacryloylaminophenyl methacrylate), a material with pronounced liquid crystal photoalignment capability. The characteristic bands corresponding to photosensitive groups of this polymer are identified by comparing its FTIR spectra with the spectra of model compounds having a reduced number of photochemical transformations. The changes in FTIR spectra of this material under ultraviolet illumination give evidence of two Fries rearrangements (in arylamide and arylester groups) and a conversion of C˭CH2 methacrylic bonds. This allows one to refine the microscopic model of photoinduced ordering in this class of polymers.

Structure, photo-, electroluminescence and electron transport properties of planar nanoscale light-emitting metal-organic device consisting of Au nano-islands and Tb(thd)3 is reported. FTIR and photoluminescence measurements confirm stable vacuum deposition behavior of Tb(thd)3 in a monomeric form. With STM imaging, a thickness-dependent structure of Tb(thd)3 layers was observed and local current-voltage characteristics of organic films were found to be non-linear at voltages exceeding 1.0 V. Electroluminescence from the nanocomposite was observed at voltages 15–30 V, showing the emission features both of Tb(thd)3 and Au nano-islands. The results can be useful for design of planar light-emitting devices with controllable spectral characteristics.

On the basis of the absorption coefficient calculation it is shown that strong optical and mechanical anharmonicity of the OH group vibrations and the interaction between the main tone and the overtone of the other vibration of the same OH group and the same symmetry (Fermi-resonance) leads to the formation of two-phonon bound states (biphonons) seen in spectra as “additional” sharp bands. The IR and Raman bands half-width and shape of the main tone and the bound state is measured as a function of temperature and a possible theoretical treatment is proposed. The anharmonicity parameters and low-frequency vibrations responsible for the temperature behavour of the main tone and the biphonons are determined.

An experimental curve in the region of the stretching νOH(D) vibrations of an acetic acid crystal is compared with the frequency dependence of the absorption coefficient K (ν) calculated on the basis of Fermi resonance theory for crystals taking into account two-particle excitations (TPE). The theory is shown to be suitable for description of peculiarities of the νOH band substructure in crystals with H-bonds.