Investigation of Amorphous Carbon in Nanostructured Carbon Materials (A Comparative Study by TEM, XPS, Raman Spectroscopy and XRD).

Amorphous carbon (AC) is present in the bulk and on the surface of nanostructured carbon materials (NCMs) and exerts a significant effect on the physical, chemical and mechanical properties of NCMs. Thus, the determination of AC in NCMs is extremely important for controlling the properties of a wide range of materials. In this work, a comparative study of the effect of heat treatment on the structure and content of amorphous carbon in deposited AC film, nanodiamonds, carbon black and multiwalled carbon nanotube samples was carried out by TEM, XPS, XRD and Raman spectroscopy. It has been established that the use of the 7-peak model for fitting the Raman spectra makes it possible not only to isolate the contribution of the modes of amorphous carbon but also to improve the accuracy of fitting the fundamental G and D2 (D) modes and obtain a satisfactory convergence between XPS and Raman spectroscopy. The use of this model for fitting the Raman spectra of deposited AC film, ND, CB and MWCNT films demonstrated its validity and effectiveness for investigating the amorphous carbon in various carbon systems and its applicability in comparative studies of other NCMs.

Interplay of Intra- and Intermolecular Interactions in Solid Iodine at Low Temperatures: Experimental and Theoretic Spectroscopy Study.

This work is devoted to the discussion of structural changes in crystalline iodine under low temperature studied from experimental and theoretic points of view. Experimental Raman spectra in the temperature range 5-300 K demonstrated unusual behavior of stretching vibration at ∼180 cm-1 with temperature. The data allowed obtaining of ω( T) functions for both external translational and internal stretching modes of I2. It was found that ω( T) trends significantly differ in comparison to typical van der Waals crystal α-S8. The observed anomalies are explained from a theoretic point of view because of the strengthening of intralayer halogen bonding between I2 molecules.

Raman spectra of terephthalic acid crystals in the temperature range 5K-300K.

Raman spectra of terephthalic acid crystals were taken in the temperature range 5K-300K. The temperature dependence of the vibrational frequency of the O⋯O hydrogen bond is found to contain information on the mechanism of the proton motion along the bond (hopping and/or tunneling). Onset temperatures of both tunneling and ordering (termination of the hopping) process are determined. Triplet exciton bands observed in the high-wavenumber spectral range also exhibit the relation with proton motions between oxygen atoms. The energy spectra of molecular chains of terephthalic acid, the proton potential energy along the bond, and the probabilities of tunneling as a function of the hydrogen bond lengths are calculated.

Large porous particles for respiratory drug delivery. Glycine-based formulations.

Large porous particles are becoming increasingly popular as carriers for pulmonary drug delivery with both local and systemic applications. These particles have high geometric diameters (5-30µm) but low bulk density (~0.1g/cm3 or less) such that the aerodynamic diameter remains low (1-5µm). In this study salbutamol and budesonide serve as model inhalable drugs with poor water solubility. A novel method is proposed for the production of dry powder inhaler formulations with enhanced aerosol performance (e.g. for salbutamol-glycine formulation the fine particle fraction (FPF≤4.7µm) value is 67.0±1.3%) from substances that are poorly soluble in water. To overcome the problems related to extremely poor aqueous solubility of the APIs, not individual solvents are used for spray freeze-drying of API solutions, but organic-water mixtures, which can form clathrate hydrates at low temperatures and release APIs or their complexes as fine powders, which form large porous particles after the clathrates are removed by sublimation. Zwitterionic glycine has been used as an additive to API directly in solutions prior to spray freeze-drying, in order to prevent aggregation of powders, to enhance their dispersibility and improve air-flow properties. The clathrate-forming spray freeze-drying process in the multi-component system was optimized using low-temperature powder X-ray diffraction and thermal analysis.

Pressure-induced phase transitions in L-alanine, revisited.

The effect of pressure on L-alanine has been studied by X-ray powder diffraction (up to 12.3 GPa), single-crystal X-ray diffraction, Raman spectroscopy and optical microscopy (up to approximately 6 GPa). No structural phase transitions have been observed. At approximately 2 GPa the cell parameters a and b become accidentally equal to each other, but without a change in space-group symmetry. Neither of two transitions reported by others (to a tetragonal phase at approximately 2 GPa and to a monoclinic phase at approximately 9 GPa) was observed. The changes in cell parameters were continuous up to the highest measured pressures and the cells remained orthorhombic. Some important changes in the intermolecular interactions occur, which also manifest themselves in the Raman spectra. Two new orthorhombic phases could be crystallized from a MeOH/EtOH/H(2)O pressure-transmitting mixture in the pressure range 0.8-4.7 GPa, but only if the sample was kept at these pressures for at least 1-2 d. The new phases converted back to L-alanine on decompression. Judging from the Raman spectra and cell parameters, the new phases are most probably not L-alanine but its solvates.

Difference in the dynamic properties of chiral and racemic crystals of serine studied by Raman spectroscopy at 3-295 K.

Single-crystal polarized Raman spectra (60-4000 cm(-1) at 3 < or = T < or = 295 K) were measured for chiral L- and racemic DL-serine, alpha-amino-beta-hydroxypropionic acid, (NH3)+CH(CH2OH)(COO)-. The Raman spectra of dl-serine do not show any striking changes with temperature or on storage. In contrast to that, the dynamical properties of L-serine change at about 140 K. These changes can be interpreted as the reorientation of the side chain -CH2OH fragments of the zwitterions with respect to the backbone C-C bonds, resulting in the positional disorder of the O-H...O intermolecular H-bonds. The redistribution in the intensities of the Raman spectra of the crystals of L-serine stored for a long time (about a year) indicates the changes in the orientation of the molecular fragments in the direction normal to the axes of the head-to-tail chains. The difference in the thermodynamic functions of L- and DL-serine reported previously [Drebushchak, V. A.; Kovalevskaya, Yu. A.; Paukov, I. E.; Boldyreva, E. V. J. Therm. Anal. Calorim. 2007, 89 (2), 649-654] is explained by the difference in the spectra of external vibrations of the crystals.