EPR spectroscopy of low-dimension structures produced in natural diamonds and synthetic diamond films by ion implantation (review)

We give a brief overview of the results of investigations that gave birth to new trends in radiospectroscopy, physics of interactions of atomic particles with condensed materials, and solid-state physics, especially, physics of superhard materials. The main factors that provided the basis for these trends are as follows.

1. High-energy ion implantation into solids plays a constructive role with respect to the solid matrix. A modified structure composed of matrix atoms and characterized by both short-range and long-range orders different from the initial one is formed as a result of this implantation. Low-dimension systems of a new class, whose properties are described in the present work, were produced in diamonds. A distinguishing feature of this new class of elements is that one-dimensional elements possesing their own spatial ordering of atoms constitute a volume superlattice composed of the same atoms in a three-dimensional crystalline matrix.
2. Radiospectroscopy methods can be used to identify formations with sizes greater than 0.1 μm in one dimension (along with traditional objects with sizes within the nanorange in three dimensions) and study their properties. These objects are characterized by a number of essentially new radiospectroscopic properties: superlinear kinetics of resonance absorption, an additional nonzero phase angle in the recorded absorption signal relative to the hf modulation field in the absence of saturation, (“phase angle”), an anomalous increase in the intensity of absorption with an increase in the modulation frequency of the static field (in the absence of saturation), and a super-Lorentizian shape of the resonance absorption line. These properties provide a basis for radiospectroscopic identification of mobile quasiparticles with nonzero spin (like to solitons) in solids.
3. A system of “channels” with high electroconductivity (in the microwave range) can be produced in dielectric solids, specifically in superhard materials. Individual channels can have cross-sectional sizes of up to sizes of the nanorange. This can serve as a basis for the development of electronic devices with elements having cross-sectional sizes that are significantly smaller than those of elements of traditional microelectronics as small as the sizes of elements of nanotechnology.

     

Programmable dispersion compensation and pulse shaping in a 26-fs chirped-pulse amplifier

We have constructed a 26-fs chirped-pulse amplifier that incorporates a programmable liquid-crystal spatial light modulator in the pulse stretcher. The modulator serves a dual purpose. First, we apply frequency-dependent phase shifts to compensate for cubic, quartic, and nonlinear phase dispersion in the amplifier, which results in a reduction in pulse duration from 32 to 26 fs, in agreement with the transform limit of the amplified pulse spectrum. Second, we are able to produce high-fidelity compressed amplified shaped pulses by applying phase masks directly within the stretcher. Shaped pulse energies of greater than 1 mJ are routinely obtained.     

Enhanced Electrochemical Response of Isoniazid Electrocatalytic Oxidation on RGO-PPD-SiW Modified Electrode

The electroactive composites based on reduced graphene oxide (RGO), poly-o-phenylenediamine (PPD) and heteropolyacids – H₄SiW₁₂O₄₀nH₂O (SiW) and H₃[PW₁₂O₄₀] ⋅ nH₂O (PW) was applied to a screen-printed carbon electrode (SPCE) as a planar three-electrode cell as the first step to creating various devices, in particular, sensors and catalysts. We studied potential use of the modified and unmodified SPCE planar electrode in determining the concentration of antitubercular antibiotic isoniazid (isonicotinic acid hydrazide C₆H₇N₃O or INH). The best result was observed for SPCE+RGO-PPD-SiW. CV of normal saline with various concentrations of C₆H₇N₃O demonstrated linear dependence of the relevant anodic peak current either in the bulk solution upon immersion of the modified electrode or in a droplet on the electrode surface.     

Oxazolo[3,2-a]pyridinium and oxazolo[3,2-a]pyrimidinium salts in organic synthesis

The methods for the synthesis of oxazolo[3,2-a]pyridinium and oxazolo[3,2-a]pyrimidinium salts and their reactivities are reviewed. Both systems exhibit ambident properties in reactions with nucleophiles; depending on the substituents and the reagents, both the oxazole and azine rings can undergo opening and transformations. A number of new methodologies involving oxazolopyridinium and oxazolopyrimidinium salts for the design of functionalized oxazoles, imidazoles, fused pyrroles, and other heterocyclic systems are generalized. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 831–848, April, 2008.     

Morphological transformations of native petroleum emulsions. I. Viscosity studies

Emulsions of water in as-recovered native crude oils of diverse geographical origin evidently possess some common morphological features. At low volume fractions varphi of water, the viscosity behavior of emulsions is governed by the presence of flocculated clusters of water droplets, whereas characteristic tight gels, composed of visually monodisperse small droplets, are responsible for the viscosity anomaly at varphi approximately 0.4-0.5. Once formed, small-droplet gel domains apparently retain their structural integrity at higher varphi, incorporating/stabilizing new portions of water as larger-sized droplets. The maximum hold-up of disperse water evidently is the close-packing limit of varphi approximately 0.74. At higher water contents (up to varphi approximately 0.83), no inversion to O/W morphology takes place, but additional water emerges as a separate phase. The onset of stratified flow (W/O emulsion gel + free water) is the cause of the observed viscosity decrease, contrary to the conventional interpretation of the viscosity maximum as a reliable indicator of the emulsion inversion point.     

Specific features of the structure,reactivity, thermolysis,and magnetism of cymantrenecarboxylate complexes of lanthanides

The properties of the cymantrenecarboxylate (containing (CO)₃ Mn(η⁵-C₅H₄CO₂ ^- group) complexes of lanthanides obtained and studied by the authors in the years 2009–2015 are reviewed. The complexes represent a new type of heterometallic 3d–4f compounds. Both binuclear and polymer complexes of various types are synthesized. The variation of the synthesis conditions and the use of additional ligands make it possible to successively change the Mn: Ln ratio in a molecule of the compounds and to obtain the ratio equal to 3: 1, 2: 1, and 1: 1. The polymeric heteroleptic derivatives, acetate and acetyacetonate cymantrenecarboxylates, are synthesized. Using the photolabile cymantrene fragment as a source of Mn²⁺ ions, polynuclear Mn–Ln heterometallic cymantrenecarboxylates are obtained under the oxidative photolysis conditions. The influence of binuclear neodymium cymantrenecarboxylate on the polymerization of dienes is studied. The structures of the complexes, their physicochemical properties, and possibilities of practical application are considered.     

Direct solventless supercritical fluid extraction of chlorbiphenyls from aqueous solutions at 0.1 × 10–12 g/g level and whole extract analysis by GC/ECD

A method of PCB determination in water based on direct supercritical fluid extraction (SFE) and off-line solventless SFE/GC coupling has been developed. High SFE recovery of the targeted compounds from water and high efficiency of their solventless transfer into GC were achieved. The method can be used for fast screening of water samples for PCBs at ultratrace levels.     

Heterocycles containing a bridge nitrogen atom. 11. Recyclization of 5-methyloxazolo[3,2-apyridinium cation under the action of nucleophiles containing NH2 group. Crystal structure of 3-(p-nitrophenyl)-1,4-dihydropyrido-[2,1-c]-as-triazinium perchlorate

Reactions of 5-methyl-2-(p-nitrophenyl)oxazolo[3,2-a]pyridinium perchlorate with ammonia and hydrazine, in contrast to the reaction with secondary amines, do not produce indolizines. The reaction with ammonia produces 5-methyl-2-(p-nitrophenyl)imidazo[1,2-a]pyridine; with hydrazine, 3-(p-nitrophenyl)-1,4-dihydropyrido[2,1-c]-as-triazinium semiperchlorate (2 moles of base per one mole of acid). The structure of the latter is solved by X-ray structural studies. Dedicated to Professor Henk van der Plas on his 70th birthday. For No. 9, see [1]. M. V. Lomonosov Moscow State University, Moscow 119899, Russia Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 550–556, April, 1999.     

Minimization of dispersion in an ultrafast chirped pulse amplifier using adaptive learning

Minimizing residual frequency dispersion that accompanies pulse stretching, amplification, and recompression is an important consideration in ultrashort chirped-pulse amplifiers. Here we show how an adaptive learning algorithm can be used in conjunction with a pulse shaper to compensate for higher-order and nonlinear dispersion in a chirped-pulse amplifier. Using spectral blueshifting as a sensitive diagnostic for pulse shape, we implement a 'learning loop' comprised of the pulse shaper, strong field laser ionization, and a genetic algorithm to minimize dispersion through the amplifier. We verify our optimization results using frequency-resolved optical gating (FROG) measurements and also show theoretically and experimentally that spectral blueshifting is indeed a sensitive diagnostic for pulse shape, and specifically, for higher-order dispersion.