Papers by Volodymyr Gayvoronsky
Molecular Crystals and Liquid Crystals
It is shown that utilization of electron transitions between quasistationary exciton states of sp... more It is shown that utilization of electron transitions between quasistationary exciton states of spatially separated electron (in spherical germanium quantum dot (QD) core) and hole (localized ot the QD interface with silicon matrix) can provide up to four times enhancement of the radiative intensity against the similar ones among stationary exciton states.
Optical Materials, Apr 1, 2023
We report synthesis and study of E→Z→E photoswitching transformations of methyl-substituted azo-a... more We report synthesis and study of E→Z→E photoswitching transformations of methyl-substituted azo-aldehyde and six novel corresponding azo-azomethines containing electron withdrawing/donating substituents in paraposition to-CH-N-bond, being analyzed by UV-Vis and 1 H NMR spectroscopy techniques. Impact of donor/ acceptor substituent nature on isomerization kinetics was studied in THF solutions by light activation at 390 nm. We obtained high optical quality of PMMA thin films doped with mentioned dyes. It was characterized with both angularly resolved optical elastic scattering data and nonlinear refractive/absorptive optical responses analysis via CW laser beam self-action effects manifestation at wavelength 532 nm. Pronounced self-focusing effect contribution was shown for electron donating substituents (-CH 3 ,-OCH 3) and self-defocusing one for electron withdrawing-NO_2 group. UV irradiation at 254 nm provides switching from self-defocusing to self-focusing mode of-NO 2 substituted dye-doped film with refractive nonlinear optical response efficiency Re(χ (3)) ≈10^(− 2) esu on background of moderate photoinduced absorption effects manifestation.
A typical color change of EtOH (a–c) and (d–e) i-PrOH solutions of Zn(CH3COO)2 × 2H2O, at differe... more A typical color change of EtOH (a–c) and (d–e) i-PrOH solutions of Zn(CH3COO)2 × 2H2O, at different stages of the interaction of components: (a) starting solution 1–2 min after the preparation, (b) 30 min, and (c) 1-h heating at 60 °C; (d) 20 min after the preparation, (e) 60 min, and (f) 2-h heating at 60 °C. Figure S2. The starting i-PrOH solution of Zn(CH3COO)2 × 2H2O (a) and (b–c) luminescence of ZnO NP obtained by hydrolysis. Figure S3 a, b. Comparison of UV-Vis spectra of ZnO NP in solutions and solid precipitates. Figure S4. UV-Vis spectra of ZnO NP in the resulted solutions (a) EtOH, (b) i-PrOH, (c) MeCN, and (d) PPG. (PDF 346 kb)
We search for efficient schemes of second and terahertz harmonic generation in nanocomposites con... more We search for efficient schemes of second and terahertz harmonic generation in nanocomposites consisted of metal-oxide semiconductor quantum dots incorporated into a dielectric matrix, when the quantum dots are in resonance and the dielectric matrix is out of resonance with femtosecond light pulse. It’s established that large efficiency of frequency up-conversion is possible to attain, which may be for the optimal quantum dot concentration in above mentioned nanocomposites by 70% higher than in pure nonlinear dielectric matrix.
This work is aimed at developing nonlinear optical method of non-destructive and surface sensitiv... more This work is aimed at developing nonlinear optical method of non-destructive and surface sensitive, real time (in situ) detection of CBRN agents. Ferroelectric polymer polyvinylidene fluoride PVDF and its copolymer P(VDF-TrFe) film is used as chemical-stabile and sensing element. Results showed that combination of the interface scanning technique at third harmonic, the second harmonic generation readout, and spatial profile analysis is promising for nondestructive remote sensing applications.
Molecular Crystals and Liquid Crystals, 2005
We have examined the efficiency of various techniques for the determination of the nonlinear opti... more We have examined the efficiency of various techniques for the determination of the nonlinear optical response (NLO) of dye-doped liquid crystals. The intensity ranges where each technique is optimal are defined. We propose an approach for precise and detailed NLO response measurements as a function of dye concentration when the optical parameters of samples vary in a wide range and
Optical Materials Express, 2019
We developed a wavelength-tunable second harmonic scattering experimental setup to investigate di... more We developed a wavelength-tunable second harmonic scattering experimental setup to investigate dispersion of the nonlinear optical response of three different nanocrystal suspensions (LiNbO 3 , ZnO and BiFeO 3). Special attention was paid to reproducibility issues with the implementation of a detailed protocol that allows correcting for the setup spectral response. The absolute, orientation-averaged second order susceptibilities of the three nanomaterials were then assessed in the 700-1300 nm spectral range evidencing very specific optical signatures. The well-defined resonances observed for ZnO and BiFeO 3 near their electronic transitions were found to be poorly described by the Miller's rule.
Soft Matter, 2019
Based on the experimental evidence of aggregation of dye molecules, the effect of strong enhancem... more Based on the experimental evidence of aggregation of dye molecules, the effect of strong enhancement of the light-induced director reorientation in a dye-doped nematic liquid crystal is explained by the interaction of supramolecular aggregates.
Journal of Materials Chemistry C
Set of azo- and azomethine dyes with antipyrine fragments, including one bent shaped azomethine, ... more Set of azo- and azomethine dyes with antipyrine fragments, including one bent shaped azomethine, its homo- and copolymers with MMA were synthesized. The materials demonstrated efficient refractive nonlinear optical response via self-action effect.
We search for efficient schemes of second and terahertz harmonic generation in nanocomposites con... more We search for efficient schemes of second and terahertz harmonic generation in nanocomposites consisted of metal-oxide semiconductor quantum dots incorporated into a dielectric matrix, when the quantum dots are in resonance and the dielectric matrix is out of resonance with femtosecond light pulse. It's established that large efficiency of frequency up-conversion is possible to attain, which may be for the optimal quantum dot concentration in above mentioned nanocomposites by 70% higher than in pure nonlinear dielectric matrix.
Ukrainian Journal of Physics, 2016
For the first time, a contactless express method, which is based on the self-action of picosecond... more For the first time, a contactless express method, which is based on the self-action of picosecond range laser pulses at 1064 nm, is used for the characterization of an optically dense porous layer of carbon material (CM) bulk particles obtained from a lignocellulosic source. It is found that the oxidation treatment reduces the Brunauer-Emmett-Teller (BET) surface area from 9.52 × 10 5 m 2 /kg to 2.73 × 10 5 m 2 /kg. This reduction occurs due to the destruction of the carbon matrix fraction and to the formation of novel O-containing surface groups. The concentrated 30-mass% HNO3 is found to be the most efficient oxidant giving the highest yield of carboxylic (Cb), anhydridic, lactonic, and phenolic surface functionalities. The concentration of the surface functional groups is determined in a dynamic argon atmosphere by thermogravimetric (TG) analysis and thermoprogrammed desorption coupled with IR (TPD-IR) spectroscopy. The surface acidity defined from data of the Boehm titration shows the acceptable agreement with the data of TG-TPD-IR examination. An enhancement of the surface hydrophilicity allows the use of carbon matrix for the covalent binding of bioligands, amino acids, their residues, and proteins to the oxygen-containing functionalities, such as Cb groups. The observed photoinduced absorption efficiency of the bulk carbon particles Im((3) C) ∼ 10 −16 m 2 /W is in the range of that of nanosized carbons. A slight variation of the ratio Im((3) C)/ BET within the limits of experimental errors indicates a certain correlation between the absorptive NLO response and the CM specific surface. We suggest to utilize Im((3) C) as a quality parameter for carbon materials subjected to the oxidation, which is a typical initial step of the most commonly used functionalization routes for the preparation of biomedical materials.
Applied Physics B, 2016
An efficient application of fast remote diagnostics for carbon material (CM) bulk particles was d... more An efficient application of fast remote diagnostics for carbon material (CM) bulk particles was demonstrated. Porous layers of CM particles with different oxidation levels were characterized by self-action of picosecond laser pulses at 1064 nm. Nitrogen adsorption, Boehm titration, and thermal analysis of the oxidized CMs revealed diverse specific surface area $$S_\mathrm {BET}$$SBET, reasonable surface acidity, and high concentration of surface oxygen-containing groups. Dense CM porous layers showed a monotonous reduction of the absorptive nonlinear optical (NLO) response efficiency versus the oxidation level with characteristic magnitude Im($$\chi _\mathrm{C}^{(3)})\sim 10^{-10}$$χC(3))∼10-10 esu for the carbon particles fraction. The obtained Im($$\chi _\mathrm{C}^{(3)})/S_\mathrm {BET}$$χC(3))/SBET ratio remains approximately constant, which indicates the certain proportion between the absorptive NLO response efficiency and the specific surface area. We suggest to use Im($$\chi _\mathrm{C}^{(3)})$$χC(3)) as a figure of merit for carbons subjected to the oxidation—the route to enhance the CM surface reactivity.
Optics Communications, 2016
Abstract Optical properties and nonlinear optical response due to the CW and pulsed laser radiati... more Abstract Optical properties and nonlinear optical response due to the CW and pulsed laser radiation self-action at 532 nm were studied in composites based on KDP single crystals with incorporated nanofibriles of nanostructured oxyhydroxide of aluminum (NOA). It was shown a high optical quality and structural homogeneity of nanocomposites KDP:NOA by the transmittance spectra, elastic optical scattering and XRD analysis. It was observed manifestation of the second harmonic generation efficiency enhancement in the KDP:NOA versus the nominally pure KDP ( λ =1064 nm, τ =1 ns) that is correlated with efficient refractive index self-modulation Δ n ∼ 10 − 4 ( λ =532 nm, τ =30 ps). In the pyramidal and prismatic growth sectors of the nominally pure KDP crystal it was shown opposite signs of the photoinduced variations both of the refractive index and of the optical absorption/bleaching due to resonant excitation of the native defects at 532 nm. It should be considered for the wide-aperture laser frequency KDP family based convertors fabrication.
… Workshop, 2008
Results and discussions In order to study the influence of PS layers morphology on optical proper... more Results and discussions In order to study the influence of PS layers morphology on optical properties, the test structures has been fabricated using different process parameters. By changing the electrochemical current, the electrolyte composition, and the dopant characteristics of ...
Micromachines
Polyvinylidene fluoride and its copolymers are a well-known family of low-cost ferroelectric mate... more Polyvinylidene fluoride and its copolymers are a well-known family of low-cost ferroelectric materials widely used for the fabrication of devices for a wide range of applications. A biocompatibility, high optical quality, chemical and mechanical durability of poly(vinylidene fluoride–trifluoroethylene), (P(VDF–TrFE)), makes it particularly attractive for designing of effective coating layers for different diagnostic techniques. In the present work, the nonlinear optical characterization of P(VDF-TrFE)-coating films deposited onto a glass substrate was done. Advantages of the coating application for cells/substrates in the field of multiphoton imaging the efficiency of such coating layer for long-duration characterization of so-called harmonic nanoparticles (HNPs) were shown. The influence of glass surface protection by P(VDF-TrFE) film from an effect of HNPs sticking to the walls of the flow-cell was analyzed for effective studying of the optical harmonics generation efficiency of H...
Optical Materials, 2016
Abstract Present paper is devoted to the investigation of the nanosilicon films internal structur... more Abstract Present paper is devoted to the investigation of the nanosilicon films internal structure effect on optical properties. Atomic force microscopy results reveal that the films with different thickness have fundamentally different grain size distribution (samples with the film thickness less than 50 nm have single-mode grain size distribution, while samples with the film thickness more than 50 nm have multi-mode distribution of grain size). The correlation between grain size of nanosilicon films, photoluminescence and scattering indicatrix was shown. Well-isolated vibronic structures were observed on the ultraviolet–visible photoluminescence spectrum from nanosilicon films with the thickness more than 10 nm. The photoluminescence spectra in the red range correlate with the nanosilicon grain size distribution due to the effect of the quantum confinement. However, due to the complex shape of the grains mathematical modeling of photoluminescence spectrum is complicated. Both scattering indicatrix and photoluminescence reveal the multi-mode grain size distribution of the films with thickness more than 50 nm. The comparative analysis of theoretical results of optical radiation scattering by nanosilicon films with experimental ones is illustrated. Mathematical modeling of the scattering indicatrix shows the correlation of average grain size from scattering and photoluminescence data.
EPJ Web of Conferences, 2018
Characterization methods of nanocomposites consisted of semiconductor metal-oxide quantum dots (Q... more Characterization methods of nanocomposites consisted of semiconductor metal-oxide quantum dots (QD) incorporated into a dielectric matrix have been elaborated on the base of time resolved fourwave mixing and photon echo. Large permanent dipole moment, inherent to QDs under study, local field effect, the QD spatial dispersion and distribution function of the transition dipole moments in QDs are taken into account. New responses at multiple frequencies in directions differed from spatial synchronism conditions of well-known signals have been predicted.
Ukrainian Journal of Physical Optics
We report the studies of third harmonic generation efficiency using an interface-scanning techniq... more We report the studies of third harmonic generation efficiency using an interface-scanning technique for colloidal suspensions of harmonic ZnO nanoparticles under nanosecond-range pulsed laser excitation at 1064 nm. The harmonic nanoparticles represent a new type of biomarkers for multiphoton imaging, which generate efficiently second-, third-and higher-order optical harmonics. Using the reference data for fused silica, the characteristic orientationaveraged nondegenerate cubic nonlinear optical susceptibility ~ 10-10 esu is obtained for the ZnO nanoparticles with the mean sizes 40-150 nm. The third harmonic generation efficiency increases with increasing nanoparticle size and achieves the reference data known for the bulk ZnO crystals. The technique suggested by us can be applied in nondestructive express diagnostics of nanoparticles, when characterizing their nonlinear optical properties, studying the effect of their size and shape, and further improving their harmonic generation efficiency.
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Papers by Volodymyr Gayvoronsky