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Based on the luminescence spectroscopy data, it was shown that the method of fixing (between two plates of quartz, quartz and brass, quartz and silicon) a vitrified film prepared from a powder of an anisometric europium(III) β-diketonate complex does not affect the photophysical properties of the film in the temperature range of 270–370 K and, accordingly, does not affect the operational characteristics of a reusable and highly sensitive luminescent temperature probe based on it.

YVO4:Yb,Er upconversion nanoparticles (UCNPs) are synthesized to study the possibility of using them as nanoprobes to solve biological problems. Aqueous colloidal solutions of UCNPs are injected into the bodies of grape snails. When preparations from animal organs are irradiated with a continuous wave (CW) laser at a wavelength of 980 nm, luminescence is observed in the region of 520–560 nm, due to radiative transitions in Er3+ ions. A comparative analysis of the behavioral activity of animals with injected nanoparticles and control animals with no nanoparticles reveals no signs of toxicity. The nanoparticles are promising as luminescence nanoprobes in biological problems.

Nanoparticles of YVO4 doped with Yb3+ and Er3+ ions, which exhibit upconversion luminescence upon cw laser excitation at 980 nm, are synthesized according to the familiar hydrothermal procedure. Physical and structural features of intermediate products obtained at different technological stages of creating upconversion nanoparticles are established via electron microscopy, Raman spectroscopy, and luminescence microscopy.

The problem of neural network forecasting of processes with changing laws of their behavior and imperfection of time-series samples is considered on the example of analysis of urban traffic flows. The goal is to improve the accuracy of such forecasting. To achieve this goal, we analyze the applicability of self-learning recurrent neural networks with controlled elements and the spiral structure of layers. Based on the development and application of these neural networks, the new methods and the system implementing them are proposed. These methods, in contrast to known solutions, allow continuous training of neural networks and forecasting of processes. There is no need to interrupt training to perform forecasting. For forecasting, it is possible to continuously take into account the properties of the observed processes. In addition, improved controlling of associative recall of information from the memory of recurrent neural networks is provided to improve the accuracy of forecasting. The results of traffic flow forecasting are presented. The results are compared with estimates obtained using other methods. It is shown that the proposed methods have advantages in accuracy compared to the known solutions. The developed methods are recommended for use in advanced robotic and other intelligent systems.

The results from a comparative analysis of the emission spectra of upconversion YVO4:Yb, Er nanoparticles synthesized in sizes ranging from 10 nm to 1 μm are used to discuss the contribution from high-energy oscillators on the surfaces of nanoparticles to the nonradiative energy transfer between Er3+ ion levels, and to the formation of the red emission band at 660 nm.

Unlike standard nanodiamonds (NDs), boron-doped nanodiamonds (BNDs) have shown great potential in heating a local environment, such as tumor cells, when excited with NIR lasers (808 nm). This advantage makes BNDs of special interest for hyperthermia and thermoablation therapy. In this study, we demonstrate that the negatively charged color center (NV) in lightly boron-doped nanodiamonds (BNDs) can optically sense small temperature changes when heated with an 800 nm laser even though the correct charge state of the NV is not expected to be as stable in a boron-doped diamond. The reported BNDs can sense temperature changes over the biological temperature range with a sensitivity reaching 250 mK/√Hz. These results suggest that BNDs are promising dual-function bio-probes in hyperthermia or thermoablation therapy as well as other quantum sensing applications, including magnetic sensing.

A novel temperature probe with −1.0% K−1 mean relative and −5.4 μs K−1 mean absolute sensitivity of the luminescence decay time in the range of 270–370 K is presented. The probe is a 20 μm thick vitrified film (sandwiched between two quartz plates) fabricated from an amorphous powder of an anisometric europium(III) β-diketonate complex through a melt-processing technique. It is established that the film exhibits bright Eu3+ ion luminescence with the most intense peak at 611 nm caused by efficient ligand-to-metal energy transfer. The observed thermal luminescence sensitivity we associate with a well-known non-radiative relaxation mechanism of the Eu3+ ions through the low-lying ligand-to-metal charge transfer state. The experiments also showed that (i) the luminescence of the film is insensitive to oxygen, (ii) the film is completely resistant to UV-vis light, (iii) there is full reversibility of the temperature dependent luminescence decay time, and (iv) the strong luminescence of the film can be efficiently excited by irradiation in the wavelength range of 280–425 nm (including inexpensive and portable blue-violet light sources). The listed facts allow us to consider the film as a promising probe for reusable luminescent thermometers, suitable for long-term temperature monitoring.

Using amplified femtosecond pulses at a wavelength of 1028 nm, the second harmonic is generated at a wavelength of 514 nm by composite polymer films containing D-π-A (push–pull) chromophores with quadratic optical nonlinearity. It is shown that these films are photostable with respect to laser pulses having peak intensities of up to 11.6 GW/cm2. The effective generation of the second harmonic is observed in a wide range of pump beam incidence angles (20°–80°) with a maximum in the vicinity of 60°.

The relationship between the structures of liquid acetonitrile (AN) and dimethyl sulfoxide (DMSO) and rotational contributions in the ultrafast optical Kerr effect is considered. It is shown that the structure of associates in the form of chains impedes the emergence of induced orientational anisotropy of molecules in liquid DMSO. In liquid AN, antiparallel dimers are capable of reorientation under the action of a pump laser field; both dimers and monomers contribute to the libration response.

A new approach to the creation of photostable highly sensitive sensor elements for reusable luminescent thermometers based on vitrified films of mesogenic europium(III) and terbium(III) beta-diketonate complexes that are oxygen insensitive, effectively absorbing light in the region of 390–410 nm and reversibly changing the luminescence decay time in the region of 143–348 K, is proposed.

The signal of the ultrafast optical Kerr effect (OKE) in liquids, including toluene C7H8, nitrobenzene C6H5NO2, and acetonitrile C2H3N is analyzed. It is shown that considering the correlation between the orientational and librational responses allows us to determine the rise time of the orientational response associated with the inertial nature of molecular rotations over a time interval of 300–500 fs after the impact of a laser pulse, and to increase the accuracy of determining the form of the Raman spectral density function.

An analysis of the prospects for creating new luminescent molecular photonics materials based on mesogenic lanthanide(III) β-diketonate complexes is presented. We consider vitrified films that combine intense monochromatic luminescence, high optical quality, and complete resistance to UV radiation with the ability to change their photophysical properties (for example, the absorption band width and luminescence intensity) depending on the local structure and under external actions, such as UV radiation and temperature. The problems of control of the photophysical properties of these films and the possibility of their application as working media of high-tech luminescent materials and devices (for example, luminescent sensors of temperature, oxygen, and UV radiation, as well as light-conversion materials) are discussed.

Experiments on recording the ultrafast optical Kerr effect (OKE) in solution of europium(III) β‑diketonate complexes in toluene at a concentration of 10–2 mol/L showed that the total OKE signal is not a superposition of two contributions, one of which is related to the vibrational–rotational dynamics of toluene molecules, while the other is due to the vibrational–rotational dynamics of the europium(III) complexes. This immediately indicates that the europium(III) complexes essentially change the structure of liquid toluene, which is reflected in the character of an orientational response in picosecond range.

An 18-fold increase in the mean luminescence intensity of Tb3+ ions in a vitrified film of a terbium( III) β-diketonate complex under UV laser radiation in atmospheric oxygen at 300 K was observed. Luminescence and Raman spectroscopy data reveal that the observed effect was caused by photophysical and photochemical processes changing the geometry and structure of the complex.

The decomposition of the recorded signal of the ultrafast optical Kerr effect (OKE) in benzonitrile into its components corresponding to different molecular contributions is considered. An optical scheme based on two-pulse nonresonant pumping with the registration of a test laser pulse is devised for this purpose.

The use of multiple-pulse laser excitation to control molecular responses that produce the ultrafast optical Kerr effect in order to perform selective spectroscopy of the Raman-active motions of molecules in liquids is discussed. Theoretical analysis and experimental data indicate that multiple-pulse laser excitation is a powerful spectroscopic tool that allows unique information to be obtained about low-frequency molecular dynamics in a liquid.

YVO4:Yb,Er luminescent nanoparticles (NPs) with sizes of 10–700 nm are produced. The use of laser excitation wavelengths of 980 and 257 nm results in the emission of Er3+ ions in the spectral region of 527 and 555 nm. No spectral line of Er3+ ions is recorded at 660 nm, which is indirect evidence of the low efficiency of nonradiative multiphonon intra-ion transitions and the insensitivity of NPs to luminescence quenchers in an aqueous solution.

Spectroscopic data are presented for the motion of molecules in a liquid during double-pulse excitation and registration of the ultrafast optical Kerr effect (OKE). It is shown that selective spectroscopy of individual molecular motions can be achieved by choosing certain parameters of the double-pulse sequence.

We report on a novel 5 µm thick vitrified film prepared from the amorphous powder of the mesogenic terbium(III) β-diketonate complex and supported on a quartz plate through melt-processing technique. For the first time a 16-fold increase in the mean photoluminescence intensity of Tb3+ ions in the film was observed after a prolonged irradiation of the film by 337 nm pulsed nitrogen laser in air at room temperature. The analysis of optical spectroscopy data has shown that the main reason responsible for the observed phenomenon was a change in the inner coordination spheres of Tb3+ ions. It resulted in an increase in energy gaps between the emitting 5D4 level of the Tb3+ ions and triplet states of ligands. In this way the efficiency of the energy back transfer from the 5D4 level of the Tb3+ ions to the triplet state of the ligands was decreased and the mean photoluminescence intensity of the Tb3+ ions in the film was enhanced.

A novel temperature-sensitive luminescent material was fabricated from a powder of a mesogenic terbium(III) β-diketonate complex, [Tb(CPDK3–7)3phen] (CPDK3–7 = 1-(4-(4-propylcyclohexyl)phenyl)decane-1,3-dione, phen = 1,10-phenanthroline) by a melt-processing technique. The material is a 20 μm thick vitrified film sandwiched between two quartz plates. The film effectively absorbs light in the wavelength range of 280–405 nm and exhibits a green narrow-band luminescence of Tb3+ ions due to efficient ligand-to-metal energy transfer. The average luminescence decay time varies reversibly with temperature from 373 μs at 143 K to 33 μs at 253 K having the mean absolute sensitivity of −3.3 μs K−1. The simplicity in design, the high optical transmittance (around 90%) in the visible wavelength region of 450–800 nm, the insensitivity to atmospheric oxygen and the complete resistance to UV light provide technological and operational advantages of the proposed material. The findings demonstrated that the material is promising as a sensing element for luminescent thermometers suitable for long-term temperature monitoring in the range of 143–253 K.

We have proposed a novel temperature-sensitive luminescent material which is a 20 μm thick vitrified film (sandwiched between two quartz plates) fabricated from an amorphous powder of a mesogenic europium(III) β-diketonate complex through a melt-processing technique. The film photoexcited by a 337 nm pulsed nitrogen laser displays a typical Eu3+ ion luminescence bands with the strongest peak at 612 nm and with the decay time of 537 μs at 298 K. It is obtained that both the mean luminescence intensity and the luminescence decay time at 612 nm decrease significantly with temperature increasing from 298 to 348 K; the average values of the relative and absolute temperature sensitivities of the luminescence decay time in the range of 298–348 K are −1.2%·K−1 and −6.5 μs·K−1, respectively. The thermal quenching mechanism of the luminescent properties was analyzed and discussed. The experiments showed that, the luminescent properties of the film is insensitive to oxygen, the film is photostable under UV light, there is full reversibility of the temperature-dependent luminescence intensity and the decay time, and the high luminescence brightness of the film can be observed with violet light excitation. These factors indicated that the film is promising material for reusable luminescent thermometers, suitable for long-term monitoring in the range of 298–348 K.

We analyzed nonlinear emission properties of oxide nanocrystals YVO4 doped with Yb3+ and Er3+ ions which are one of the most interesting types of upconverting nanoparticles (UCNPs). As is widely believed the deviation of the power-dependent upconversion phosphorescence intensity from a quadratic character is attributed to a saturation effect occurring at the relatively high pump power. In this paper, we focused on studying upconversion nonlinearity at the low pump power when excited states populations are considerably less then ground states populations. The analysis of actual energy transfer channels allowed us to propose a reduced model having simple solutions. The obtained analytic expressions for the dependences of upconversion photoluminescence intensity and its nonlinearity on the pump power revealed that multiphonon transitions are a main factor responsible for the variation of upconversion nonlinearity in a range between 1 and 2. This result could be used in spectroscopic experiments for simple and direct identification of the non-radiative relaxation efficiency in YVO4:Yb, Er UCNPs.

Results from the nonresonance spectroscopy of CdS/CdSe quantum dots (composites of CdSe–CdS nanoparticles (core–shell)) are presented. The nonlinear optical properties of CdS/CdSe QDs in PMMA are studied with fs pulses at 1053 nm using the transient lens technique. QDs generate rapidly oscillating signals with amplitude rise times of around 200 fs and decay times of around 500 fs, while pure PMMA polymer only generates an oscillating signal whose envelope coincides with its autocorrelation function.

The quantum size effects of colloid water-organic media synthesized nanocomposites (CdSe–CdS core–shell) in toluene solution is studied. Femtosecond fluorescence up-conversion spectroscopy is used to establish that quantum dots are characterized by a biexponential decay of luminescence kinetics: the decay times are 1.8 and 26.8 ps for nanoparticles with average sizes of 2 nm and 4.5, and 68 ps for nanoparticles with an average size of 2.9 nm.

Structural modifications following long-term UV irradiation with a pulsed nitrogen laser led to a decrease/increase in the luminescence intensities of vitrified films with the thickness of 8/20 µm, respectively. The films were prepared from a terbium(III) β-diketonate complex. Optical spectroscopic studies revealed that these features are associated with different structures of the films. The 20 µm film includes the aggregates hindering the non-radiative relaxation of the T1 states of ligands. Such a phenomenon is not observed in the 8 µm film. A comparative analysis of the luminescent data indicates that the redistribution of the T1 energies of the ligands under UV modification is the predominant reason for the changes of the luminescent properties of the films.

We have fabricated the upconversion nanoparticles (NPs), which are nanocrystallites of 10 nm, doped with Yb3+ and Er3+ ions, prepared through hydrothermal method. Monitoring of their photophysical properties had been realized at different fabrication stages by using electron microscopy and luminescence spectroscopy under photoexcitation of the NPs with the 100 mW laser at 980 nm wavelength. The performed monitoring allows us to observe dramatic changes in the upconversion properties of the NPs during the sequence of the fabrication stages and revealed very strong correlation between the NPs’ upconversion efficiency and their structural specificities.

The presented model shows that for any trap distribution in semiconductor quantum dots (QDs) the evolution of photoinduced charge carriers (as a rule, responsible for observed signals in optical spectroscopic studies of QDs) consists of two prominent components. The fast component lying in the picosecond range reflects the increase and the fast decay of the charge carrier population, and the slow one exhibits the profile of a long-time mono-exponential decay with a decay time ranging from tens ns to few µs. It is important, that the decay time of the slow component depends not only on relaxation processes in QDs but also on a profile of a trap distribution. This finding opens up promising possibilities to gain a new insight into the role of traps in QDs photophysical characteristics by carrying out a detailed analysis of the long-time mono-exponential decay of experimental signals associated with the charge carrier population.

Using the hydrothermal method, we synthesized water soluble YVO4: Yb, Er nanoparticles with a size less than 10 nm. Nanoparticles exhibit intense luminescence in the green region due to Er3+ ions when excited by laser radiation at a wavelength of 980 nm as a result of the up-conversion process. Bright and stable luminescence also persists in an aqueous solution of nanoparticles. Based on experimental data, it can be argued that the objects obtained are promising in biological applications, as well as up-conversion phosphors.

Bulk SrTiO3 doped by 40 keV Cr+ ions and substrate temperature Timp = 600°C is studied. This sample exhibits supercontinuum generation by amplified femtosecond laser pulses (λ = 800 nm; repetition rate, 3 kHz; pulse duration, 150 fs; pulse energy 4 µJ), recorded by a monochromator with a PMT. The blue edges of the supercontinuum spectra differ, depending on the location of the focused laser beam spot on the sample.

The first experimental results on selective detection of the collective (libration) response in a liquid using a scheme of non-resonance double-pulse spectroscopy based on detecting the ultrafast optical Kerr effect (OKE) in ortho-dichlorobenzene at room temperature are presented. Nonrelevant vibrational and rotational responses are dumped and the relevant libration molecular responses are amplified by varying the duration, delay, and relative intensities of linearly polarized pump pulses.

The energy transfer mechanism, which provides the feeding of the excited 5 D 4 level of Tb(III), has been studied by photoluminescence spectroscopy in the Tb(III) complex with p-sulfonato-thiacalix[4]arene doped into the silica nanoparticles. The quantitative evaluation of the rate constants of each energy transfer step highlights two channels of the energy transfer from the singlet ligand-centered level to the 5 D 4 level. The channel one occurs via the triplet ligand level S 1 →T 1 → 5 D 4 , the second channel comes about via the higher levels of Tb(III) S 1 → 5 D 3 → 5 D 4 . The latter channel determines the rate of the luminescence decay of the 5 D 4 level. The high luminescence efficiency and enhanced thermo- and photo-stabilities make the Tb(III) complexes doped into the silica nanoparticles a promising nanomaterial for medical and bioanalytical applications.

We report on the decomposition of the molecular contribution to the optically heterodyne-detected optical Kerr effect (OHD-OKE) in benzonitrile C6H5CN in the process of double-pulse laser excitation. The pump pulses with linear orthogonal polarizations, controllable intensities and timing enable us to manipulate the amplitudes of various molecular responses due to the fact that the OHD-OKE signal is formed by the superposition of independent third-order responses associated with each pump pulse. We apply this technique to detect the intermolecular response selectively by using an excitation scenario with suppression of orientational and intramolecular responses. A detailed comparative analysis of third-order optical responses indicates strongly that the double-pulse excitation of the OHD-OKE is the useful spectroscopic technique to obtain precise information on the intermolecular spectrum in liquids.

The study of the terbium(III) and gadolinium(III) β-diketonate complexes by photoluminescence spectroscopy reveals considerable changes of the photophysical properties of the complexes under the UV laser irradiation. The measurements show the enhancement of the luminescence intensities in the vitrified transparent film of the terbium(III) complex as well as the gadolinium(III) complex under the 337 nm laser irradiation at room temperature. The irradiated film of the terbium(III) complex restores the initial photophysical properties after heating close to the melting temperature (∼353 K) and cooling. We observe no change of the luminescent properties of the irradiated film for months. These features can be used for the design of new lanthanide-based photostable systems with laser control of the luminescence intensity.

Simultaneous control over the vibrational and rotational molecular responses in ultrafast optical Kerr-effect signals in acetonitrile, toluene, and chloroform at room temperature is achieved by means of non-resonance excitation with two 30-fs orthogonal linearly polarized laser pulses. It is shown that the orientational response of the molecules can be suppressed and their vibrational response isolated by enhanced the delay between the exciting pulses and their relative intensity.

We revealed the effect of the prolonged UV laser irradiation on luminescent behavior of photonic materials based on mesogenic lanthanide(III) β-diketonate complexes by using a novel 3 μm vitrified film of an europium(III) β-diketonate complex. We used the Eu3+ ions to monitor the UV laser-induced photophysical processes in the film. Despite the fact that usually prolonged UV irradiation leads to irreversible photofragmentation of ligands, we had observed no photodecomposition of the complexes after the irradiation of the film with the 337 nm laser for 5 h. The spectroscopic study revealed (i) a 16.5-fold luminescence intensity decrease due to laser-induced changes in inner coordination spheres of the Eu3+ ions and (ii) the main channel of non-radiative energy losses from the Eu3+ ions through the multiphonon relaxation. These features open up new possibilities for designing advanced photonics materials with excellent photostability and luminescent properties controlled during operation.

We have studied picosecond dynamics of photo-induced charge carriers in CdSe/CdS nanoparticles with sizes of 2.0 and 2.9 nm in toluene colloidal solutions using femtosecond up-conversion spectroscopy. The kinetics of nanoparticles luminescence excited by laser pulses of 50 fs duration at 350 nm were observed. The simulation of experimental data showed that electron thermalization occurs within 0.5 ps, while recombination processes have characteristic times of 5 and 20 ns, although these cannot be unequivocally identified using the simplest recombination model with direct transitions and single type of traps. However, a comparative analysis indicates a fundamental difference in the mechanisms responsible for the dynamics of charge carriers in the time interval up to 5 ps after laser excitation, which we associate with different structures of traps in 2.0 and 2.9 nm particles.

We have synthesized YVO4: Yb, Er nanoparticles in the size range of 100-500 nm, which form aqueous colloidal solutions and are luminescent when excited by femtosecond light pulses at a wavelength of 263 nm. It was established that the luminescence occurs due to the emission of Er3+ ions in characteristic spectral lines at 525 nm and 550 nm. However, an effective quenching channel for metastable levels of Er3+ ions is evident, so that the characteristic luminescence line of Er3+ ions in the 660 nm region is absent. We associate this quenching channel with a large concentration of lattice defects with possible localization of high-frequency quenchers.

The control of the coherent vibrational and rotational molecular motions in acetonitrile C2H3N was achieved by using the optically heterodyne-detected optical-Kerr-effect spectroscopy. A sequence of the two pump pulses with parallel and orthogonal polarizations was used for the non-resonant selective excitation of the molecular motions. The measurements showed that it is possible to control the molecular motions through the key parameters: the separation time, the relative intensities and polarization of the sequential pulses. The variation of the key parameters specifies the regimes of amplification and the suppression of the molecular responses. Two excitation scenarios with the amplification and suppression of the rotational responses were used as an example. The vibrational response was amplified in both cases.

Two-pulse control of time-dependent anisotropy in liquid carbon tetrachloride at room temperature is implemented by using femtosecond polarisation spectroscopy. The liquid is excited by a train of two linearly polarised laser pulses, and the state of anisotropy is probed by a weak third pulse with registration of the optical Kerr effect. It is shown that by varying the delay between the exciting pulses and their relative intensity, selection of contributions of individual intramolecular modes into the recorded signal is achieved.

Optical control of coherent intramolecular oscillations in chloroform CHCl3 and dimethyl sulfoxide (CH3)2SO is attained experimentally under normal conditions by means of femtosecond polarization spectroscopy. Nonresonant excitation of the medium is accomplished by a sequence of two linearly polarized laser pulses. The state of the medium is probed by the third pulse via the optical Kerr effect. We show that control over the vibrational dynamics of molecules on a sub-picosecond scale can be achieved by varying the delay between the excitation pulses and their relative intensity.

A novel molecular polarization spectroscopy method of processing the strengthened femtosecond signals, based on the ultrafast optical Kerr effect, is proposed. The processing of the reference chloroform signal by the novel method at a room temperature is demonstrated. It is shown that due to the manipulation by individual molecular motions through the constructive or destructive interference of corresponding wave packets it is possible to determine directly from the experiment such constants of molecular dynamics as the relaxation times of the coherent vibrations (≈1.5 ps) and orientation anisotropy (≈1.2 ps).

We report the results of core-shell (CdSe/CdS) quantum dots study. Quantum dots sizes were evaluated as 2.0 and 2.9 nm from absorbance edge position. We suggest two types of traps, predict properties of these traps based on upconversion luminescence data and previous studies of quantum dots (CdSe cores only) and bulk CdS.

The femtosecond selective spectroscopy of vibrational-rotational dynamics of molecules in a liquid was realized using optical Kerr effect registration under two-pulse nonresonant excitation. The object chosen for the study was the chloroform at room temperature. It was shown that control of the separate molecular motions by creating the constructive or destructive interference of corresponding wave packets allows one to determine directly from the experiment such constants of molecular dynamics as the relaxation times of the coherent vibrations (≈1.5 ps) and those of orientational anisotropy (≈1.2 ps).