Application of NMR spectroscopy for analysis of the composition of pine needle essential oil

We have used ¹H and ¹³C NMR spectroscopy to analyze the chemical composition of essential oils of pine needles grown in different regions of the Republic of Belarus. We consider the change in the composition of the oils depending on the area where the pines were grown. We suggest using pine essential oil as a biological indicator of environmental conditions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 246–249, March–April, 2006.     

Characterization of the essential oil of Agastache rugosa by NMR spectroscopy

The composition of essential oil from Agastache rugosa (Fish. et Mey) O.Kuntze was studied by ¹H and ¹³C NMR spectroscopy. Essential oil was isolated from the aerial part of plants growing in the Central Botanical Garden of the NAS of Belarus during flowering and fruiting. The oil chemical composition was found to depend little on the sampling time. It was shown that NMR spectroscopy could be successfully used to both monitor the content of the hepatotoxic substance (pulegone) and characterize the quality and authenticity of essential oils.     

Vertically aligned carbon nanotubes from natural precursors by spray pyrolysis method and their field electron emission properties

Vertically aligned carbon nanotubes have been synthesized from botanical hydrocarbons: Turpentine oil and Eucalyptus oil on Si(100) substrate using Fe catalyst by simple spray pyrolysis method at 700°C and at atmospheric pressure. The as-grown carbon nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Raman spectroscopy. It was observed that nanotubes grown from turpentine oil have better degree of graphitization and field emission performance than eucalyptus oil grown carbon nanotubes. The turpentine oil and eucalyptus oil grown carbon nanotubes indicated that the turn-on field of about 1.7 and 1.93 V/μm, respectively, at 10 μA/cm². The threshold field was observed to be about 2.13 and 2.9 V/μm at 1 mA/cm² of nanotubes grown from turpentine oil and eucalyptus oil respectively. Moreover, turpentine oil grown carbon nanotubes show higher current density in relative to eucalyptus oil grown carbon nanotubes. The maximum current density of 15.3 mA/cm² was obtained for ∼3 V/μm corresponding to the nanotubes grown from turpentine oil. The improved field emission performance was attributed to the enhanced crystallinity, fewer defects, and greater length of turpentine oil grown carbon nanotubes.     

NMR determination of the composition of balsams from scotch pine resin

We have used ¹H and ¹³C NMR spectroscopy to study the composition of pine resin balsams from Scotch pines grown in different regions of the Republic of Belarus. We have established that their chemical composition does not depend very much on the region where they are grown or the level of contamination of the forests by radioactive and industrial emissions. Prolonged storage of the balsams leads to a substantial change in their compositions, due to isomerization of the resin acids. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 411–415, May–June, 2008.     

The use of photoinduced light scattering for the evaluation of photoelectric fields in Lithium Niobate Crystals

The photovoltaic and diffusion fields in nominally pure single crystals of stoichiometric composition (R = Li/Nb = 1) grown from the melt with 58.6 mol % of Li₂O (LiNbO₃ stoich), in the nominally pure single crystals of congruent composition (LiNbO₃), and in congruent single crystals doped with Cu²⁺, Zn²⁺, and Gd³⁺ are found from the parameters of the photoinduced light scattering indicatrix obtained with the use of a 60-mW He-Ne laser.     

Radiation-induced phase transition in a film of niobium-tin solid solution

A 5-μm-thick film of a niobium-tin solid solution (18.3 at % Sn) grown by ion-plasma sputtering with subsequent codeposition of ultrafine metal particles is irradiated by a fast proton flux with a fluence of 10¹⁹ p ⁺/cm². X-ray diffraction analysis carried out using CuK _α (λ = 0.154178 nm), CoK _α (λ = 0.179021 nm), and MoK _α (λ = 0.071069 nm) radiations shows the presence of a radiation-induced stannide niobium (Nb₃Sn) phase in the region of proton energy dissipation (at a depth of 2.5 μm from the surface of the solid solution film). It is found that at the end of the particle range, nonlocal interaction between the protons and the concentrated matrix solid solution takes place. When interacting with the supersaturated solid solution, a bombarding particle covers a tangible area of the solution, so that an intermetallic phase greater than critical in size nucleates. The feasibility is demonstrated of using a fast particle flux to produce an intermetallic (superconducting) phase inside a solid solution layer with a composition close to the stoichiometric composition of the intermetallic.     

Optical and electrical properties of SnS semiconductor crystals grown by physical vapor deposition technique

Tin sulfide (SnS) is a material of interest for use as an absorber in low cost solar cells. Single crystals of SnS were grown by the physical vapor deposition technique. The grown crystals were characterized to evaluate the composition, structure, morphology, electrical and optical properties using appropriate techniques. The composition analysis indicated that the crystals were nearly stoichiometric with Sn-to-S atomic percent ratio of 1.02. Study of their morphology revealed the layered type growth mechanism with low surface roughness. The grown crystals had orthorhombic structure with (0 4 0) orientation. They exhibited an indirect optical band gap of 1.06 eV and direct band gap of 1.21 eV with high absorption coefficient (up to 10³ cm⁻¹) above the fundamental absorption edge. The grown crystals were of p-type with an electrical resistivity of 120 Ω cm and carrier concentration 1.52×10¹⁵ cm⁻³. Analysis of optical absorption and diffuse reflectance spectra showed the presence of a wide absorption band in the wavelength range 300-1200 nm, which closely matches with a significant part of solar radiation spectrum. The obtained results were discussed to assess the suitability of the SnS crystal for the fabrication of optoelectronic devices.     

Morphology,chemical composition,and electrical characteristics of hybrid (Ni-C) nanocomposite structures grown on the van der Waals GaSe(0001) surface

The morphology and chemical composition of metal (Ni), carbon, and composite (Ni-C) nanostructures grown on oxidized and unoxidized (0001) surfaces of a layered GaSe crystal by electron beam vacuum evaporation of the material from a liquid ion source in an electric field have been investigated using atomic force microscopy and X-ray photoelectron spectroscopy. It has been demonstrated that this technology makes it possible to grow nanostructures with different morphologies depending on the growth mode and substrate surface state. Dense homogeneous arrays of nickel nanoparticles (Ni@C) (with geometrical sizes of ～1–15 nm and a lateral density of higher than 10¹⁰ cm^?2) encapsulated into carbon shells, as well as carbon layers (with a thickness of the order of several nanometers), are grown on the unoxidized van der Waals GaSe(0001) surface, whereas Ni-C composite nanostructures are grown on the oxidized surface. The formation of oxide nanostructures on the van der Waals surface and their chemical composition have been examined. Vertical hybrid Au/Ni/(Ni-C)/n-Ga₂O₃(Ni@C)/p-GaSe structures grown on the GaSe(0001) surface contain Ni@C nanoparticles embedded in the wide-band-gap n-Ga₂O₃ oxide. The current-voltage characteristics of these structures at temperatures close to T = 300 K exhibit specific features of the Coulomb blockade effect.     

High-quality InAlN/GaN heterostructures grown by metal–organic vapor phase epitaxy

We fabricated high-quality InAlN/GaN heterostructures by metal–organic vapor phase epitaxy (MOVPE). X-ray diffraction measurements revealed that InAlN/GaN heterostructures grown under optimal conditions have flat surfaces and abrupt heterointerfaces. Electron mobility from 1200 to 2000 cm²/V s was obtained at room temperature. To our knowledge, this mobility is the highest ever reported for InAlN/GaN heterostructures. We also investigated the relationship between the Al composition and sheet electron density (N_s) for the first time. N_s increased from 1.0×10¹² to 2.7×10¹³ cm⁻² when the Al composition increased from 0.78 to 0.89.     

Morphology of InN nanorods using spectroscopic Raman imaging

We report the vibrational properties of vertical and oblique InN nanorods (NRs) grown by molecular beam epitaxy (MBE). Surface optical (SO) Raman mode at 561 cm⁻¹, belonging to E₁ symmetry [SO(E₁)], is identified along with symmetry allowed Raman modes of E₂(low), E₂(high), and E₁(LO) at 87, 489, and 589 cm⁻¹, respectively, corresponding to wurtzite InN phase. Usually, SO phonon modes arise due to breakdown of translational symmetry of surface potential at surface defects, which are attributed by the surface roughness. Intensity distribution of E₁(LO) and SO(E₁) phonon modes over a specified area have been analysed using Raman area mapping with an optical resolution of 400 nm. Imaging with E₁(LO) phonon mode, originating from the bulk of the sample, distinguishes the vertical NRs alone. We are able to resolve NR morphologies in both vertical and oblique cases with additional Raman mapping analysis of SO(E₁) phonon mode, emerging from the surface irregularities, which are confined to the tip of MBE grown NRs. Copyright © 2013 John Wiley & Sons, Ltd.     

Magneto-optical activity of crude oil and its heavy fractions

We have experimentally studied optical and magneto-optical spectra of solutions of crude oils of different origin and their heavy fractions in the visible spectral range. Magnetic circular dichroism of oil in the wavelength range ??550 nm has been revealed. We show that the shape of the spectra of this dichroism depends on the origin of crude oil, with the magnetic dichroism magnitude being proportional to the concentration of the oil in the solution. A comparison of the data of magneto-optical spectroscopy with electron paramagnetic resonance spectra and chemical composition of samples has allowed us to conclude that the observed magneto-optical activity is determined by the occurrence of VO²⁺ complexes in the oil samples. The revealed magneto-optical activity of crude oil can form the basis of a unique method of analysis of the composition and properties of oils of different origin and heavy fractions thereof.     

Photoelectric fields in lithium niobate crystals

Photovoltaic and diffusion fields in nominally pure single crystals of stoichiometric composition (R = Li/Nb = 1) grown in the presence of 6 wt% K₂O flux (LiNbO₃ stoich. K₂O) in nominally pure single crystals of complementary composition (LiNbO₃), complementary single crystals doped with Zn²⁺, Er³⁺ at wavelength of 476, 514.5, 530 nm are defined according to parameters of photo induced light scattering indicatrix. Photo induced changes of crystals’ refractive index are defined.     

Influence of surface strain on the MOVPE growth of InGaP epitaxial layers

In this paper, we present a study of the influence of strain on the composition uniformity, phase separation and ordering of compressive and tensile strained InGaP epitaxial layers grown on GaP and GaAs substrates. The paper demonstrates how strain, caused by lattice mismatch, influences the spinodal-like decomposition and ordering in InGaP layers. We concentrated our efforts on an alloy with the lattice mismatch close to a value of Δa/a=10^-2. Transmission electron microscopy (TEM), low temperature photoluminescence and atomic force microscopy (AFM) were used to demonstrate that epitaxial layers grown under compressive strain have additional properties in comparison to those ones grown under tensile strain. The presence of ordering, spinodal-like decomposition and compositional fluctuations was studied in relation to the sign of strain. PACS 61.72.Lk; 68.35.Ct; 68.37.Lp; 68.35.Dv; 78.30.Fs     

Growth by laser ablation of Ti-based oxide films with different valency states

x La_2/3+yTiO_3-δ perovskite (with δ≤0.5) were deposited by the laser ablation technique from Li_0.33La_0.56TiO₃ targets. Their growth onto MgO substrateswas studied as a function of the oxygen pressure. For films grown in vacuum (10^-6 mbar), a La_0.63TiO_2.5 composition was obtained, meaning that Ti³⁺ alone is present in the films, while Li ions are not incorporated under these conditions. This material shows good electric conductivity (ρ=500 mΩ cm). By contrast, insulating films with a Li_0.1La_0.70TiO₃ composition corresponding to the Ti⁴⁺ species were obtained at high oxygen pressures (>0.05 mbar). For all conditions, textured films were grown with different orientations depending on the temperature and the oxygen pressure. Received: 10 September 1997/Accepted: 24 November 1997     

Growth of GaAs nanostructures by area selective epitaxy by migration-enhanced epitaxy

We have carried out area selective epitaxial growth of GaAs nanostructures using solid source molecular-beam epitaxy (MBE) which makes it possible to achieve ‘damage-free’ structures. However, area selective epitaxy by MBE is very difficult unless the substrate temperature is very high. This problem has been solved by using migration-enhanced epitaxy (MEE) deposition sequence. To achieve well-defined nanostructures, lateral growth beyond the SiO₂ mask boundaries has to be strictly prohibited. By MEE method, uniform two-dimensional lattice structures with vertical sidewalls can be fabricated without shrinking holes, even though the mask diameter is as small as 30 nm with a dot density as high as 5.0×10⁹ cm⁻². Also uniform one-dimensional channel structures have been successfully grown.     

AgGaS2- and Al-doped GaSe Crystals for IR Applications

We report a systematic study of AgGaS₂- and Al-doped GaSe crystals in comparison with pure GaSe and S-doped GaSe crystals. AgGaS₂-doped GaSe (GaSe:AgGaS₂) crystal was grown by Bridgman technique from the melt of GaSe:AgGaS₂ (10.6 wt.%). Its real composition was identified as GaSe:S (2 wt.%). Al-doped GaSe (GaSe:Al) crystals were grown from the melt of GaSe and 0.01, 0.05, 0.1, 0.5, 1, 2 mass % of aluminium. Al content in the grown crystals is too small to be measured. The hardness of GaSe:S (2 wt.%) crystal grown from the melt of GaSe:AgGaS₂ is 25% higher than that of GaSe:S (2 wt.%) crystal grown by a conventional S-doping technique and 1.5- to 1.9-times higher than that of pure GaSe. GaSe:Al crystals are characterized by 2.5- to 3-times higher hardness than that of pure GaSe and by extremely low conductivity of ≤ 10^− 7 Om^− 1 cm^− 1. A comparative experiment on SHG in AgGaS₂-, Al-, S-doped GaSe and pure GaSe is carried out under the pumps of 2.12-2.9 μm fs OPA and 9.2−10.8 μm ns CO₂ laser. It was found that GaSe:S crystals possess the best physical properties for mid-IR applications among these doped GaSe crystals. GaSe:Al crystals have relatively low conductivity which have strong potential for THz application.     

Determination of excess of zinc in ZnS above the stoichiometric composition

It was shown directly by chemical experiments that zinc sulfide crystals grown at high temperatures usually contain zinc in amounts above that required by the stoichiometric composition, and very pure specimens may contain no less than 10¹⁷ atoms/cm³.     

N2O concentration and isotope signature along profiles provide deeper insight into the fate of N2O in soils†

Nitrous oxide is an important greenhouse gas and its origin and fate are thus of broad interest. Most studies on emissions of nitrous oxide from soils focused on fluxes between soil and atmosphere and hence represent an integration of physical and biological processes at different depths of a soil profile. Analysis of N₂O concentration and isotope signature along soil profiles was suggested to improve the localisation of sources and sinks in soils as well as underlying processes and could therefore extend our knowledge on processes affecting surface N₂O fluxes. Such a mechanistic understanding would be desirable to improve N₂O mitigation strategies and global N₂O budgets. To investigate N₂O dynamics within soil profiles of two contrasting (semi)natural ecosystem types (a temperate acidic fen and a Norway spruce forest), soil gas samplers were constructed to meet the different requirements of a water-saturated and an unsaturated soil, respectively. The samplers were installed in three replicates and allowed soil gas sampling from six different soil depths. We analysed soil air for N₂O concentration and isotope composition and calculated N₂O net turnover using a mass balance approach and considering diffusive fluxes. At the fen site, N₂O was mainly produced in 30–50 cm soil depth. Diffusion to adjacent layers above and below indicated N₂O consumption. Values of δ¹⁵N and δ¹⁸O of N₂O in the fen soil were always linearly correlated and their qualitative changes within the profile corresponded with the calculated turnover processes, suggesting further reduction of N₂O. In the spruce forest, highest N₂O production occurred in the topsoil, but there was also notable production occurring in the subsoil at a depth of 70 cm. Changes in N₂O isotope composition as to be expected from local production and consumption processes within the soil profile did hardly occur, though. This was presumably caused by high diffusive fluxes and comparatively low net turnover, as isotope signatures approached values measured for ambient N₂O towards the topsoil. Our results demonstrate a highly variable influence of diffusive versus production/consumption processes on N₂O concentration and isotope composition, depending on the type of ecosystem. This finding indicates the necessity of further N₂O concentration and isotope profile investigations in different types of natural and anthropogenic ecosystems in order to generalise our mechanistic understanding of N₂O exchange between soil and atmosphere.     

Crystal growth, FTIR and thermal characterization of bis(ethyltriphenylphosphonium) tetrabromomanganate(II) dihydrate crystals

Single crystals of a novel compound, bis(ethyltriphenylphosphonium) tetrabromomanganate(II) dihydrate (BTP-Mn) were grown by solution growth-slow evaporation technique from aqueous solution of the compound at ambient temperature. The grown crystals were characterized by elemental analysis, powder X-ray diffraction, thermal analysis, nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infra-red spectroscopy (FTIR) techniques. The chemical composition of the compound was revealed by elemental analysis and its crystallinity was confirmed by powder X-ray diffraction. Thermal analysis confirmed that the compound was stable up to 125°C. The various kinds of protons and carbons present in the compound were confirmed by ¹H NMR and ¹³C NMR technique respectively and the presence of phosphorous was confirmed by ³¹P NMR spectrum in the compound. The modes of vibration of different molecular groups present in the compound were identified by FTIR spectral analysis. The second harmonic generation behaviour was tested by Nd:YAG laser source.     

Effect of growth temperature on the morphology and bonded states of SnO2 nanobaskets

The nanobaskets of SnO₂ were grown on in-house fabricated anodized aluminum oxide pores of 80 nm diameter using plasma enhanced chemical vapor deposition at an RF power of 60 W. Hydrated stannic chloride was used as a precursor and O₂ (20 sccm) as a reactant gas. The deposition was carried out from 350 to 500 °C at a pressure of 0.2 Torr for 15 min each. Deposition at 450 °C results in highly crystalline film with basket like (nanosized) structure. Further increase in the growth temperature (500 °C) results in the deterioration of the basket like structure and collapse of the alumina pores. The grown film is of tetragonal rutile structure grown along the [1 1 0] direction. The change in the film composition and bonded states with growth temperature was evident by the changes in the photoelectron peak intensities of the various constituents. In case of the film grown at 450 °C, Sn 3d_5/2 is found built up of Sn⁴⁺ and O-Sn⁴⁺ and the peaks corresponding to Sn²⁺ and O-Sn²⁺ were not detected.