Purpose is to analyze influence mechanisms of physicochemical coal properties on the degree of outburst risk as well as desorption kinetics of methane. Methods of scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and Raman scattering (RS) have been applied. The samples have been taken from Donbas coal seams varying in their ranks (i.e. carbonization degree). Findings. It has been identified that in the context of outburst hazardous zones, the ratio between integral intensity of spectral RS bands D and G, K = I(D)/I(G) shows abnormal dependence upon the nominal amount of volatile compounds connected with the impact by iron impurities. It has been defined that within the ferriferous coal samples, concentration of spins ns (i.e. the broken carbon bonds) correlates with iron content. Methane adsorption/desorption processes in the studied coal samples have been studied with the help of NMR method; in addition, they have been described using superposition of diffusion and filtration mechanisms. Originality. It has been understood that high iron content is typical for coal with a greater outburst hazardous degree. The abovementioned iron content and I(D)/I(G) and Ns correlation between the values determines the key role of iron impurities for coal metamorphism processes. For the first time, correlation between the outburst hazardous degree of coal seam and intensity of 3030 cm-1 IR band, stipulated by aromatic CH groups where hydrogen is in atomic status, has been identified. Practical implications. Predictability of outburst risk has been improved in the context of coal seam mining.

Atmospheric pressure metal–organic chemical vapour deposition was used to synthesize Ag-containing ZnO nanostructures of different morphology on Si substrates coated by Ag. Ag from Ag/Si substrates and Ag from silver acetylacetonate after its decomposition were used as a catalyst for ZnO nanocrystal growth for deposition of ZnO nanostructures with different morphologies. We investigated the relation of the structural parameters and chemical composition probed by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy with the photoluminescence (PL) properties and electron–phonon coupling (EPC) reflected in the multi-phonon Raman spectra. The Raman and PL spectra were studied at different powers of the exciting laser radiation (P _exc). The spectral position and width of the phonon Raman peaks and the near bandgap PL band at low P _exc are supposed to be determined by the structural quality of the surfaces/boundaries of the crystallites. The intensity of the near-bandgap and defect-related PL and the magnitude of the EPC are additionally affected by the dopant concentration. Because of the large crystallite size (>30 nm, determined from XRD), the effects of phonon or electron confinement are negligible in these nanostructures. The behaviour of the position and width of phonon and PL bands with increasing P _exc indicates that the heat dissipation in the film, which is dependent on the nanostructure morphology and Ag content, plays an important role. In addition, the cytotoxicity of ZnO:Ag nanostructures was investigated by using monolayer cell cultures of epithelioid origin Madin-Darby bovine kidney and Madin-Darby canine kidney cells at a MTT assay revealing that the level of silver doping of ZnO nanostructures, their morphology, and geometric dimensions determine their toxic effects.

The parameters of the shell and interface in semiconductor core/shell nanocrystals (NCs) are determinant for their optical properties and charge transfer but are challenging to be studied. Raman spectroscopy was shown earlier to be a suitable informative probe of the core/shell structure. Here, we report the results of a spectroscopic study of CdTe NCs synthesized by a facile route in water, using thioglycolic acid (TGA) as a stabilizer. Both core-level X-ray photoelectron (XPS) and vibrational (Raman and infrared) spectra show that using thiol during the synthesis results in the formation of a CdS shell around the CdTe core NCs. Even though the spectral positions of the optical absorption and photoluminescence bands of such NCs are determined by the CdTe core, the far-infrared absorption and resonant Raman scattering spectra are dominated by the vibrations related with the shell. The physical mechanism of the observed effect is discussed and opposed to the results reported before for thiol-free CdTe Ns as well as CdSe/CdS and CdSe/ZnS core/shell NC systems, where the core phonons were clearly detected under similar experimental conditions.