Although water contamination with drug residues is a threat to public health, there are currently barely any effective methods of purifying water from pharmaceutical substances. In this study, continuous-flow sonoplasma treatment was used for the complete degradation of tetracycline and ciprofloxacin in polluted municipal water. The addition of CeO₂ nanoparticles as catalysts significantly increased the degradation rate of the antibiotics, and a degradation degree of 70% was achieved. The presence of reactive oxygen species in the CeO₂-nanoparticle-containing sonoplasma-treated system was experimentally proven for the first time using the chemiluminescence technique.

The HCN⋯CO complex and its X-ray induced transformation to HNC⋯CO in solid noble gas (Ng) matrices (Ng = Ne, Ar, Kr, Xe) was first characterized by matrix isolation FTIR spectroscopy at 5 K. The HCN⋯CO complex was obtained by deposition of HCN/CO/Ng gaseous mixtures. The assignment was based on extensive quantum chemical calculations at the CCSD(T) level of theory. The calculations predicted two computationally stable structures for HCN⋯CO and three stable structures for HNC⋯CO. However, only the most energetically favorable linear structures corresponding to the co-ordination between the H atom of HCN (HNC) and the C atom of CO have been found experimentally. The HCN⋯CO complex demonstrates a considerable red shift of the H–C stretching vibrations (−24 to −38 cm⁻¹, depending on the matrix) and a blue shift of the HCN bending vibrations (+29 to +32 cm⁻¹) with respect to that of the HCN monomer, while the CO stretching mode is blue-shifted by 15 to 20 cm⁻¹ as compared to the CO monomer. The HNC⋯CO complex reveals a strong red shift of the H–N bending (−77 to −118 cm⁻¹) and a strong blue shift of the HNC bending mode (ca. +100 cm⁻¹) as compared to the HNC monomer, whereas the CO stretching is blue-shifted by 24 to 29 cm⁻¹ with respect to that of the CO monomer. The interaction energies were determined to be 1.01 and 1.87 kcal mol⁻¹ for HCN⋯CO and HNC⋯CO, respectively. It was found that the formation of complexes with CO had a remarkable effect on the radiation-induced transformations of HCN. While the dissociation of HCN to H and CN is suppressed in complexes, the isomerization of HCN to HNC is strongly catalyzed by the complexation with CO. The astrochemical implications of the results are discussed.

Spectroscopic characteristics and X-ray induced transformations of the HCN$\mathrm{\cdots }$ CO₂ complex in solid Ar and Kr matrices were studied by FTIR spectroscopy and ab initio calculations at the CCSD(T) level. The complex was 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$\mathrm{\cdots }$ 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$\mathrm{\cdots }$ CO₂ complex, which was explained tentatively by steric hindrance.