Chernivtsi University Scientific Herald. Chemistry最新文献

{"title":"Antimicrobial activity of 5-nitrovinylimidazoles","authors":"A. Grozav, S. Y. Deyneka, V. Chornous, V. Antoniychuk","doi":"10.31861/chem-2019-818-07","DOIUrl":"https://doi.org/10.31861/chem-2019-818-07","url":null,"abstract":"A rapid development of the microbial resistance against antibiotics is one of the most acute problems occurring at contagious diseases treatment. That is why the search of new highly active antimicrobial drugs is a problem of the constant and significant scientific importance. Using the “Pass Online” software, a series of compounds with potentially high antimicrobial activity/inactivity efficiency has been selected among the derivatives of the 5-carbofunctionalized imidazoles. It was found that the 5-nitrovinylimidazoles should exhibit the highest activity. Nitrofural and Clotrimazole are used commonly in medicine as antimicrobial and antifungal medicines and they were selected as the reference compounds to compare an activity of the compounds involved into this investigation. Five inhibition activity indexes were used to evaluate a potential antimicrobial efficiency of the proposed compounds: an ability to inhibit the ATPase of the lipid transfer; the chloride peroxidase, the phthalate-1,6-beta-glucosidase; the NADPH-peroxidase and the endo-1,6-beta-glucosidase. The results obtained in this investigation have proven that these indexes are quite high for both the proposed novel compounds and for the reference medicines. All theoretical results have also been verified experimentally and all the reported compounds have shown a sufficient antimicrobial efficiency against reference strains of the bacteria Staphylococcus Aureus, Eschericia Coli and the fungi Candida Albicans when applied as solutions with concentrations 0.24-500 μg/L. Therefore, they may have a significant potential for the further investigations. An acute toxicity of the compounds has been evaluated by using the software «GUSAR Online Acute Rat Toxicity Prediction». An additional relevance control of the toxicity evaluation was realized by the toxicity cross-verification with the reference compounds Clotrimazole and Nitrofural. It was found that the reported 5-nitrovinylimidazoles can be classified as the fourth toxicity class chemicals.","PeriodicalId":9913,"journal":{"name":"Chernivtsi University Scientific Herald. Chemistry","volume":"135 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79568408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heterostructures based on nanodispersed TiO2 and binary systems TiO2-CdTe, TiO2-Cu(In,Ga)Se2 sensitized by polymethyn dye, as photocatalysts of redox processes","authors":"I. Kobasa","doi":"10.31861/chem-2019-819-04","DOIUrl":"https://doi.org/10.31861/chem-2019-819-04","url":null,"abstract":"New light-sensitive heterostructures of semiconductors (TiO2, TiO2-CdTe, TiO2-Cu(In,Ga)Se2) sensitized with an anionic polymethine dye with three conjugated chromophores have been developed. Based on the analysis of the results of spectral, electrochemical and energy characteristics of the studied dye, the possibility of its use as an effective sensitizer of these semiconductor materials is shown. It was found that the deposition of the dye on TiO2 leads to both batochromic and hypsochromic shifts of long wavelength absorption bands, the values ​​of which depend on the dye content in the heterostructure. This leads to a redistribution of the intensities of the absorption bands, they expand and cover almost the entire part of the visible and near-IR regions of the spectrum. This feature of the created heterostructure allows to increase the efficiency of their photocatalytic action through the use of light quanta of a wide energy range. The results of the analysis of the absorption spectra of heterostructures testify to the significant influence of semiconductors on the electronic system of dye molecules. As a result, the angle between the directions of the chromophores changes. The antibate dependence of the degree of conformational changes on the amount of dye in the heterostructure is revealed. This indicates a decrease in the interaction with the semiconductor with increasing concentration and explains the decrease in the photocatalytic activity of heterostructures at a significant content of sensitizer. Using the method of cyclic voltammetry, for the first time the oxidation and reduction potentials of the investigated polymethine dye were determined. The values ​​of HOMO and LUMO energy levels are calculated, a forecast is made regarding the possibility of their use as sensitizers of the studied semiconductors and the creation of highly efficient redox systems. The photocatalytic activity of heterostructures in the reactions of reduction of methylene blue and oxidation of iodide ions under irradiation with light absorbed by a semiconductor and a sensitizer has been revealed. Based on the analysis of energy parameters of electronic processes, the scheme of this photocatalytic transformation is proposed and substantiated.","PeriodicalId":9913,"journal":{"name":"Chernivtsi University Scientific Herald. Chemistry","volume":"571 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78916986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Light-sensitive heterostructures based on TiO2 and squaraine dye-sensitizer","authors":"I. Kobasa, O. Sema, O. I. Panimarchyk","doi":"10.31861/chem-2019-819-03","DOIUrl":"https://doi.org/10.31861/chem-2019-819-03","url":null,"abstract":"On the basis of nanodispersed titanium(IV) oxide and squaraine dye-sensitizer (D), new heterostructures (HS) have been created with a given level of photocatalytic activity and an expanded range of photosensitivity. On the basis of the analysis of the results of the measurement of spectral, electrochemical and energy characteristics, it is concluded that it is possible to use the tested squaraine as an effective TiO2 sensitizer. For the first time, using the method of cyclic voltammetry, the redox potentials of squaraine dye were determined and the redox processes were checked for reversibility. It is shown that the plot of the peak current versus the square root of the velocity sweep rate is described by a linear function. It has been found that the electrochemical processes are reversible and diffusion controlled. It is established that the values ​​of redox potentials can be used to calculate the values ​​of standard potentials and free energy. Based on the measured oxidation and reduction potentials of polymethine, the values ​​of the HOMO and LUMO energies were calculated and diagrams of the energy levels of squaraine relative to the electrophysical characteristics of titanium (IV) oxide were constructed. The peculiarities of the sensitizing ability of the studied squaraine dye were analyzed, the mechanism of photocatalytic action was proposed and its confirmation was obtained during the study of the methylene blue recovery reaction. The dependences of the photocatalytic activity of HS D/TiO2 on the dye concentration and irradiation conditions were revealed. It is shown that, when irradiated with heterostructures by light absorbed by the dye, at low concentrations of the latter (0.02÷0.2 mg/g), the photocatalytic activity increases, and at the content of the sensitizer 1.0÷2.0 mg/g, it decreases. When irradiated with HS by light absorbed by titanium(IV) oxide, photocatalytic activity decreases with increasing squaraine content.","PeriodicalId":9913,"journal":{"name":"Chernivtsi University Scientific Herald. Chemistry","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90676504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetic parameters of Cd0.85-xMnxZn0.15Te (x = 0.05-0.20) alloys melting and crystallization processes","authors":"S. M. Rusnak, A. V. Matviy, V. V. Kopach, O. Kopach, L. Shcherbak, P. Fochuk","doi":"10.31861/chem-2019-819-10","DOIUrl":"https://doi.org/10.31861/chem-2019-819-10","url":null,"abstract":"The kinetic parameters of melting and crystallization of Cd0.85-xMnxZn0.15Te (x = 0.05-0.20) alloys were investigated by the differential thermal analysis (DTA) method at different heating/cooling rates. Cd0.85-xMnxZn0.15Te alloys were synthesized from elementary materials in a vertical furnace with a high-gradient temperature that prevented the sublimation of the components. The DTA was carried out in an automatic system. The heating and cooling rates were 5 and 10°С/min, and the dwell time was 10, 30 and 60 minutes. The DTA were processed in two different ways. Using the first treatment method we found that the melt of the Cd0.80Mn0.05Zn0.15Te alloy crystallize with the supercooling, and it occurs at melt superheating higher than 12 °С. But the melt’s “negative” supercooling effect is present for alloy when the melt are superheated to 12 °C compared to the melting temperature of the alloy, which is evidence of two-phase alloy (solid phase - melt) at these temperatures. Also we determined that as the holding temperature increases the crystallization temperature decreases and the crystallization rate increases. We investigated that the area of the crystallization effect increases with increasing holding temperature. Concerning on the second treatment method we found the dependence of the solid-state volume fraction (φsolid state) versus the intermediate dwell temperature of the alloy during the heating process for Cd0.80Mn0.05Zn0.15Te. It shows that increasing of the melt-dwell temperature led to the melts full homogenization only near 1117 °C. Thus according to our previous researches we can say that the Cd1-x-уMnxZnyTe alloy’s melting temperature increases with ZnTe concentration increasing: ~1100-1102°С for Cd0.95-xMnxZn0.05Te alloys (x=0.05-0.30), ~1102-1104°С for Cd0.90-xMnxZn0.10Te alloys (x=0.05-0.30) and ~1116-1119°С for Cd0.80Mn0.05Zn0.15Te alloys.","PeriodicalId":9913,"journal":{"name":"Chernivtsi University Scientific Herald. Chemistry","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76092113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reduction of the Cd0.9Zn0.1Te surface conductivity by chemical treatment","authors":"L. Kanak, V. G. Ivanitska, A. Kanak, P. Fochuk","doi":"10.31861/chem-2019-819-05","DOIUrl":"https://doi.org/10.31861/chem-2019-819-05","url":null,"abstract":"The influence of Cd0.9Zn0.1Te crystals pretreatment on the effectiveness of the passivation was studied. The optimal conditions of passivation process are determined. Samples of Cd0.9Zn0.1Te were treated with Br2-DMF solution before the investigation. After treatment the surface of the sample was smooth without visible irregularities, which indicates the good polishing properties of this etching solution and the possibility of using the samples for further study. Passivation of samples surface was carried by the NH4F-H2O2 solution. The qualitative and quantitative composition of the Cd0.9Zn0.1Te sample surface was investigated by means of energy-dispersive X-ray spectroscopy (EDX). The formation of a uniform oxide surface layer was confirmed. The electrical characteristics of the passivated samples were investigated by measurent the current-voltage dependences. The expediency of applying of the Cd0.9Zn0.1Te sample treatment in 50% KOH solution after their chemical treatment in the NH4F-H2O2 solution was proved. It was shown that after etching, excess tellurium appears on the surface of the specimens and causes increasing surface conductivity. Measurement of current-voltage dependencies for pre-treated specimens with and without KOH solution showed that the application of this additional chemical treatment step leads to a significant increase in the surface resistance of the specimen. Visual changes in the surface are also observed. It was found that the optimal conditions for Cd0.9Zn0.1Te crystals surface passivation are chemical treatment with NH4F-H2O2 solution for 2 min at a temperature of 18 °C. The current-voltage characteristics of the sample Cd0.9Zn0.1Te were measured at different stages of surface treatment: after polishing, after etching and after passivation. It was done for compares the overall effect of the semiconductor's surface quality on their electrical properties.","PeriodicalId":9913,"journal":{"name":"Chernivtsi University Scientific Herald. Chemistry","volume":"119 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80322462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}