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  • Author: Lavinia Berţa x
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Lavinia Berta, Andrei Gâz, Francisc Boda and Augustin Curticapean

Abstract

Objective: The main objective of this research is to find the coordination ratio between AsW9 and Ag+, as a preliminary study for synthesizing a new silver-arsenotungstate complex. Material and method: The ligand:cation molar ratio in complexes was determined by conductometric and potentiometric titrations of AsW9 with silver salts: CH3COOAg, AgNO3. Results: The ratio was obtained from the inflexion points of the curves when molar ratio was plotted versus conductivity, or from the equivalence point when silver added volume was plotted versus pH value. Each graphic shows one point of inflexion corresponding to 1:1.54 ratio of AsW9:Ag+. In the same manner, the equivalent volumes determined by graphical method gave the ratio 1:1.53. The spectral results confirmed that a AsW9:Ag+ complex was formed since the ligand absorption maxima values have been changed from 190 nm to 197 nm in the case of using AgNO3 and 196 nm for CH3COOAg corresponding to the W=Od bond, and from 246.5 nm to 274 nm (AgNO3) and 270 nm (CH3COO-Ag+) for the W-Ob,c-W bond. Conclusions: Silver cation exhibit a preference for AsW9 in a ratio of 3 to 2. This ratio can be associated to a sandwich type arrangement, with two trilacunary Keggin building blocks incorporating 3 metal cations in a tetrahedral geometry.

Open access

Șerban Andrei Gâz-Florea, Eleonora Mircia and Lavinia Berţa

Abstract

Objective: Development of new electronic devices with applications in computer science as well as new medical devices pushed the researcher to find new technologies. Based on those new techniques we have designed and synthesized compounds with possible application in the field of advanced materials. Material and method: Compounds were analyzed by TLC and NMR. Routine 1H NMR (250 MHz) spectra were recorded at room temperature in deuterated acetone, unless stated otherwise. Thin-layer chromatography (TLC) was carried out on aluminum sheets coated with silicagel 60 F254 Merck TLC plates. Results: Starting from commercial available compounds intermediates were obtained in a good yield. 4,4′-(2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)diphenol was obtained starting from pentaerythritol and p-hydroxy-benzaldehyde in the presence of catalytic amounts of APTS (p-toluensulfonic acid). The product was purified by recrystallization and characterized by NMR spectroscopy. The structure exhibit 2 different signals for equatorial and axial position. Furthermore di, tri and tetra ethylene glycol were obtained by microwave assisted synthesis in a matter of minutes. Compounds were separated by recrystallization. Conclusions: In conclusion, several intermediates were synthesized and characterized from spectroscopic point of view. Further analyses should be carried out and the compounds should be tested as advanced materials.

Open access

Adrian Man, Andrei Şerban Gâz, Anca Delia Mare and Lavinia Berţa

Abstract

Alcohol based solutions are among the most convenient and wide spread aid in the prevention of nosocomial infections. The current study followed the efficacy of several types and isomers of alcohols on different bacterial species. Seven alcohols (ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl alcohol, and ethylene glycol) were used to evaluate their minimal inhibitory and bactericidal effects by microdilution method on bacteria that express many phenotypical characteristics: different cell-wall structure (Gram positive/negative bacteria), capsule production (Klebsiella pneumoniae), antibiotic resistance (MRSA vs MSSA) or high environmental adaptability (Pseudomonas aeruginosa). Results: The best inhibitory effect was noticed for n-propyl, followed by iso-propyl, n-butyl, and iso-butyl alcohols with equal values. Ethylene glycol was the most inefficient alcohol on all bacteria. In K. pneumoniae and P. aeruginosa, the bactericidal concentrations were higher than the inhibitory one, and to a level similar to that encountered for most of the Gram-positive bacteria. Among Gram-positive cocci, E. faecalis presented the lowest susceptibility to alcohols. Conclusions: All alcohols presented good effect on bacteria, even in low concentrations. Compared to ethanol as standard, there are better alternatives that can be used as antimicrobials, namely longer-chain alcohols such as propyl or butyric alcohols and their iso- isomers. Ethylene glycol should be avoided, due to its toxicity hazard and low antimicrobial efficacy. Bacterial phenotype (highly adaptable bacteria, biofilm formation) and structure (cell wall structure, presence of capsule) may drastically affect the responsiveness to the antimicrobial activity of alcohols, leading to higher bactericidal than inhibitory concentrations.