V. S. Lobkov

Mesogenic and Luminescent Properties of Lyotropic Liquid Crystals Containing Eu(III) and Tb(III) Ions

Lyotropic metallomesogens containing trivalent rare-earth metal ions have unique attractive behavior due to the combination of some specific properties of the lanthanide ions with anisotropic supramolecular organization liquid crystal and provide new promises in biochemistry and materials science. In this article, we have studied the liquid crystal and luminescence properties of lyotropic systems containing Eu(III) and Tb(III) ions based on nonionic surfactants. The type, the structural parameters of the mesophases, and the structure of a liquid crystal complex have been investigated using polarized optical microscopy (POM), X-ray diffraction, and Fourier transform infrared. In addition, on the basis of the luminescence lifetime, the structure of the first coordination sphere was determined. The results obtained based on time-resolved spectroscopy data are discussed in the light of the influence ligand environment, ion type, and the type of supramolecular organization on the luminescence efficiency of lyotropic lanthanide containing systems. The first time was reported for Eu(III) complexes increasing the luminescence efficiency in the hexagonal phase compared to the lamellar mesophase.

Comparison of spin and electron diffusion coefficients in a two-dimensional electron gas

The results from femtosecond four-wave-mixing experiments carried out in two-dimensional gas at the GaAs/AlGaAs heterojunction boundary under room temperature conditionsare presented. The obtained values of the spin and electron diffusion coefficients are 163.2 and 200 cm2/s respectively. The spin and electron relaxation times are found to be 50.7 ps and 3 ns respectively.

Implementation of room temperature femtosecond echo-processing

Conditions for implementing room temperature femtosecond echo-processing in a phtalocyanine-doped polyvinylbutyral film were studied. A logical operation of bit-by-bit multiplication on the basis of the nonlinear third-order optical response (primary photon echo) of the medium was performed in a time of less than 1 ps.

Femtosecond non-resonance double-pulse spectroscopy of molecular librations in ortho-dichlorobenzene

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.

Femtosecond photon echo and four-wave mixing in dye-doped polymer films, semiconductors and heterostructures

A review of femtosecond experiments on photon echo (PE) and four-wave mixing (FWM) performed at room temperature is presented. The Weiner–Ippen technique of FWM spectroscopy is demonstrated in dye-doped polymer films (such as polyvinilbutural doped with phthalocyanine), semiconductors (CdS) and heterostructures (GaAs/AlGaAs). The experimental setup used in these experiments is described. The dephasing times are estimated and the relaxation mechanisms are discussed.

Femtosecond multipulse polarization spectroscopy of molecular vibrations and rotations in liquids

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.

Femtosecond laser control of intramolecular vibrations in a liquid

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.

Femtosecond selective optical Kerr-effect spectroscopy: Molecular dynamics study of chloroform

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).

A photostable vitrified film based on a terbium(III) β-diketonate complex as a sensing element for reusable luminescent thermometers

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.

Ultrafast spectroscopy of CdS/CdSe quantum dots

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.