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Spectroscopic characteristics and X-ray induced transformations of the HCN... CO2 complex in solid Ar and Kr matrices were studied by FTIR spectroscopy and ab initio calculations at the CCSD(T) level. The complexwas prepared by deposition of the HCN/CO2/Ng gas mixtures (Ng = Ar or Kr). The comparison of the experiment and calculations prove formation of a linear, H-bonded NCH... OCO complex with a substantial red shift of the C-H stretching band and a blue shift of the H-C-N bending band in respect to the monomer. This result is in contrast with the previous gas-phase observations, where only T-shape complex was found. Irradiation of deposited matrices leads to formation of CN radicals and HNC molecules and subsequent annealing results in appearance of H2CN and trans-HCNH in both matrices plus HKrCN in the case of Kr. In the presence of CO2, the strongest absorption of trans-HCNH radical demonstrates an additional blue-shifted (by 6.4 cm-1) feature, which was assigned to the N-coordinated complex of this radical with CO2 on the basis of comparison with calculations. To our knowledge, it is the first experimentally observed complex of this radical. No evidence was found for HKrCN... CO2 complex, which was explained tentatively by steric hindrance. [ABSTRACT FROM AUTHOR]

The transformations of isolated CH 3 CN molecules in various solid noble-gas matrices (Ne, Ar, Kr, and Xe) under the action of X-ray irradiation at 5 K were investigated by FTIR spectroscopy. The main products are CH 3 NC, CH 2 CNH and CH 2 NCH molecular isomers as well as CH 2 CN and CH 2 NC radicals. The matrix has a strong effect on the distribution of reaction channels. In particular, the highest relative yield of keteneimine (CH 2 CNH) was found in Ne matrix, whereas the formation of CH 3 NC predominates in xenon. It was explained by differences in the matrix ionization energy (IE) resulting in different distributions of hot ionic reactions. The reactions of neutral excited states are mainly involved in Xe matrix with low IE, while the isomerization of the primary acetonitrile positive ions may be quite effective in Ne and Ar. Annealing of the irradiated samples results in mobilization of trapped hydrogen atoms followed by their reactions with radicals to yield parent molecule and its isomers. The scheme of the radiation-induced processes and its implications for the acetonitrile chemistry in cosmic ices are discussed. [ABSTRACT FROM AUTHOR]

In this work we report the results of systematic studies on the radiation-induced transformations in HCN/Ng systems (Ng=Ne, Ar, Kr or Xe) at 7 K using a combination of FTIR and EPR spectroscopy. It was shown that HCN underwent efficient decomposition producing H atoms, CN radicals and HNC isomer. The thermally induced reactions of H atoms in different matrices result in the formation of two isomeric radicals, H 2 CN and trans-HCNH, the former being predominated. The temperature dependent dynamics of CN and H 2 CN radicals in a krypton matrix was observed by EPR spectroscopy in solid krypton. The vibrational frequencies, IR intensities and magnetic resonance parameters of H 2 CN and trans-HCNH radicals calculated at the CCSD(T) level are in reasonable agreement with the experimental results. It was found that HCNH radical could be effectively bleached with visible light. The comparison of experimental and computational data made it possible to assign a new vibrational band at 918 cm −1 in an Ar matrix (and the corresponding bands in Kr and Xe) to trans-HCNH radical. In addition, HKrCN was found in the case of krypton, whereas HXeCN and HXeNC were produced in solid xenon. The reaction mechanisms and contribution of different channels are discussed. [ABSTRACT FROM AUTHOR]

The processes occurring in the X-irradiated C 2 H 2 /Kr and HCl/Kr systems in the temperature range of 7–30 K were studied using a combination of FTIR and EPR spectroscopy. In both cases, irradiation results in effective decomposition of isolated molecules (C 2 H 2 or HCl) and production of trapped H atoms. The thermal decay of trapped atoms in solid krypton was attributed to “local” reactions (below 21 K) and long-range mobility activated in the temperature range of 23–27 K. Two krypton hydrides, HKrCCH and HKrCl, were synthesized from the radiation-induced hydrogen atoms. In the case of C 2 H 2 /Kr system, competitive reaction channels of H atoms at various absorbed doses were investigated in details, and HKrCCH was found to be one of the main reaction products. The X-ray radiolysis in krypton matrices was concluded to be a promising method to obtain krypton hydrides. [ABSTRACT FROM AUTHOR]

The metal and oxide nanoparticles (NPs) containing various elements with high atomic number (Z) are considered as prospective sensitizers for the production of radicals upon X-ray irradiation of aqueous solutions, which can be used for different applications in medical treatment and material modification. The common basis for the sensitizing effect in oxygen-free systems is concerned with increase of the absorbed dose due to the presence of high- Z atoms (known as physical enhancement, relatively insensitive to the NP size). In this work we report the first experimental evidence for extra enhancement of the radical yield in a model oxygen-free aqueous organic system irradiated with X-rays (45 kVp) in the presence of W(VI) compounds, both in homogeneous solutions of Na 2 WO 4 and in the form of ultra-small NPs of WO 3. Meanwhile, in the case of larger WO 3 NPs the radical yield is consistent with physical enhancement mechanism. In the case of systems containing HfO 2 NPs only physical enhancement was observed, independent of the NP size. Unusually large enhancement of radical production and size effect for W(VI) in homogeneous and NP forms was tentatively attributed to the radiation-chemical processes involving intermediate formation of metastable W(V) due to reactions of hydrated electron. • Effect of X-ray irradiation on model aqueous organic systems was studied by spin trapping/EPR. • Increase of radical yield was found in the presence of Na 2 WO 4 and WO 3 nanoparticles. • The size effect on radical yield was observed for WO 3 nanoparticles. • The effect was explained by combination of "physical" and "chemical" enhancement. • The radiation-chemical mechanism of the effect and its implications are discussed. [ABSTRACT FROM AUTHOR]

The radiation-induced transformations of small molecules at low temperatures play an important role in the interstellar, planetary and atmospheric chemistry. This work presents a review of our recent model studies on the radiation chemistry of relevant molecules in solid noble gas (Ng) matrices, including some preliminary new results. Among the triatomic molecules, water and carbon dioxide were studied in detail. The radiation-induced degradation of isolated H 2 O yields hydrogen atoms and OH radicals, while oxygen atoms are produced at higher doses. Isolated CO 2 molecules are decomposed to yield CO and trapped oxygen atoms. Upon annealing the trapped O and H atoms are mobilized selectively at different temperatures and react with other trapped species. The formation of HCO and HOCO radicals was observed in the mixed H 2 O/CO 2 /Ng systems. Other studies were concerned with the radiation-induced degradation of simple organic molecules (methanol, formic acid) and chlorofluorocarbons (CFCl 3 , CF 2 Cl 2 ). Preliminary results for methanol revealed deep dehydrogenation yielding HCO and CO, whereas CO 2 , CO and HOCO were detected as primary products for formic acid. In the case of chlorofluorocarbons, significance of ionic channels was demonstrated. The implications of the results for modeling the processes in astrochemical ices and atmosphere are discussed. [ABSTRACT FROM AUTHOR]

Flexible materials, such as fabric, paper and plastic, with nanoscale particles that possess antimicrobial properties have a significant potential for the use in the healthcare sector and many other areas. The development of new antimicrobial coating formulations is an urgent topic, as such materials could reduce the risk of infection in hospitals and everyday life. To select the optimal composition, a comprehensive analysis that takes into account all the advantages and disadvantages in each specific case must be performed. In this study, we obtained an antimicrobial textile with a 100% suppression of E. coli on its surface. These CeO2 nanocoatings exhibit low toxicity, are easy to manufacture and have a high level of antimicrobial properties even at very low CeO2 concentrations. High-power ultrasonic treatment was used to coat the surface of cotton fabric with CeO2 nanoparticles. [ABSTRACT FROM AUTHOR]

• C 2 H 6 ...HCN complex was obtained in solid Ar by deposition of HCN/C 2 H 6 /Ar gas mixtures. • MP2/CBS ab initio calculations reveal 3 possible structures of the complex. • Complex with NCH...C hydrogen bond was observed by FTIR matrix isolation spectroscopy. • Experimental complexation-induced IR spectroscopic shifts well coincide with theory. Hydrogen bonding between saturated alkanes and HX (X is an electronegative fragment) represents a unique type of interaction of this kind. In this work we report a first experimental and ab initio study on HCN...C 2 H 6 complex using FTIR matrix isolation spectroscopy and MP2/CBS calculations. According to theoretical results, three forms of HCN...C 2 H 6 are possible: two with C(HCN)...C1(C 2 H 6) and H(HCN)...C2(C 2 H 6); C(HCN)...C1(C 2 H 6) and N(HCN)...C2(C 2 H 6) contacts and hydrogen-bonded H(HCN)...C(C 2 H 6) axial symmetry structure (the interaction energies are 0.85, 0.79 and 0.77 kcal/mol respectively). Nevertheless, only the last structure is stabilized upon experimental conditions. The hydrogen-bonded complex is spectroscopically characterized by blue shifts of HCN bending (+9.4 cm−1) and CH 3 rocking (+9.0 and +11.3 cm−1) and red shifts of H−CN stretching (−24.9 and −20.1 cm−1) and CH 3 symmetry stretching (−4.7 cm-1) vibrations. The experiment with deuterated HCN proves this assignment. The obtained results are in good agreement with the previous rotational spectroscopy study. [ABSTRACT FROM AUTHOR]

The nitrogen containing molecules of general structure C 3 H x N are important astrochemical species, which occur in interstellar and other extraterrestrial media. In this work, we have first demonstrated the formation of a number of nitriles and isonitriles (C 2 H 3 CN, C 2 H 3 NC and C 2 H 5 NC) through a direct radiation-induced synthesis from the matrix isolated intermolecular complexes HCN⋯C 2 H n (n = 2, 4, 6) at 6 K. The deposited matrices Ng/HCN/C 2 H n (Ng = Ar, Kr or Xe) were irradiated with X-rays and the formation of products was monitored by FTIR spectroscopy. In addition to synthetic products (C 3 H x N molecules), irradiation results in dehydrogenation of the initial complexes and their isomerization to the corresponding HNC⋯C 2 H n complexes. The formation of propionitrile (C 2 H 5 CN) also cannot be excluded, although this molecule was not detected experimentally, possibly due to its poor IR absorption coefficients. Cyanoacetylene (HC 3 N) is accumulated with an induction period and becomes predominating at high absorbed doses, which points to its formation from the radiation-induced decomposition of the primary products. The obtained results suggest new possible routes for formation of nitriles, isonitriles and cyanoacetylene in complex astrochemical ices. • X-rays radiolysis of HCN/C 2 H n (n = 2, 4, 6) matrix isolated complexes was examined by FTIR spectroscopy. • Radiation-induced synthesis of nitriles and isonitriles from HCN⋯C 2 H n was demonstrated. • Isomerization and dehydrogenation of HCN⋯C 2 H n upon irradiation were found. • Astrochemical implications of the obtained results are discussed. [ABSTRACT FROM AUTHOR]