Angela Kleinová

A new route for chitosan immobilization onto polyethylene surface.

Low-density polyethylene (LDPE) belongs to commodity polymer materials applied in biomedical applications due to its favorable mechanical and chemical properties. The main disadvantage of LDPE in biomedical applications is low resistance to bacterial infections. An antibacterial modification of LDPE appears to be a solution to this problem. In this paper, the chitosan and chitosan/pectin multilayer was immobilized via polyacrylic acid (PAA) brushes grafted on the LDPE surface. The grafting was initiated by a low-temperature plasma treatment of the LDPE surface. Surface and adhesive properties of the samples prepared were investigated by surface analysis techniques. An antibacterial effect was confirmed by inhibition zone measurements of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The chitosan treatment of LDPE led to the highest and most clear inhibition zones (35 mm(2) for E. coli and 275 mm(2) for S. aureus).

Photo‐Oxidation of sPP/Organoclay Nanocomposites

Photo‐oxidation of syndiotactic polypropylene–sPP/organoclay nanocomposites was performed. Nanocomposites were prepared in situ by melt compounding of sPP, compatibilizer (iPP grafted with maleic anhydride–iPP‐g‐MAN) and organoclay filler ME C18 (modified with octadecyl ammonium chains in intergaleries of layered silicate, of which silicate layers (about 1 nm thin) were exfoliated). The influence of ME C18 nanoparticles alone (in content region 1 to 15 wt%) and together with compatibilizer iPP‐g‐MAN on the photostability of the sPP nanocomposite was studied. It was found that the silicate ME C18 nanoparticles alone catalyze the photooxidation and shorten the induction period of photo‐oxidation to one fourth (at the content of 5 wt% of ME C18) in comparison with unfilled sPP) and the presence of compatibilizer supports the photo‐oxidation of sPP nanocomposite. The ME C18 nanoparticles decrease the efficiency of UV stabilizers. The rate of photo‐oxidation of sPP/clay nanocomposite after the induction period is significantly higher than unfilled sPP. The mechanism of photo‐oxidation is discussed.

HYDROGENATED AMORPHOUS SILICON CARBON NITRIDE FILMS PREPARED BY PECVD TECHNOLOGY: PROPERTIES

Hydrogenated amorphous silicon carbon nitride films were grown by plasma enhanced chemical vapor deposition (PECVD) technique. The flow rates of SiH4 , CH4 and NH3 gases were 6 sccm, 30 sccm and 8 sccm, respectively. The deposition temperatures were 350, 400 and 450 ◦C. The RBS and ERD results showed that the concentrations of Si, C, N and H are practically the same in the films deposited at substrate temperatures in the range 350-450 ◦C. In photoluminescence spectra we identified two peaks and assigned them to radiative transitions typical for amorphous materials, ie band to band and defect-related ones. The electrical characterization consists of I(V ) measurement in sandwich configuration for voltages up to 100 V. From electrical characterization, it was found that with increased deposition temperature the resistivity of the amorphous SiCN film was reduced.

A tertiary amine in two competitive processes: reduction of graphene oxide vs. catalysis of atom transfer radical polymerization

Electrically conductive graphene oxide–polystyrene hybrids (GO–PS) were prepared by reduction of graphene oxide (GO) in one step during covalent modification of graphene oxide surface using surface-initiated atom transfer radical polymerization (SI-ATRP) of styrene. The reduction of the GO surface was proven by Raman spectroscopy, electrical conductivity measurements, thermogravimetric analysis and X-ray photoelectron spectroscopy. Electrical conductivity of the synthesized GO–PS particles increased in eight orders of magnitude, depending on the polymerization period. Detailed studies were performed to determine that the tertiary amine, such as N,N,N′,N′,N′′-pentamethyldiethylenetriamine (PMDETA), used in SI-ATRP as a ligand complexing copper catalyst, was responsible for the GO surface reduction. It was shown that due to participation of PMDETA in reduction of graphene oxide, the ATRP in the presence of GO can proceed only above a certain PMDETA–GO ratio.

Classification of plum spirit drinks by synchronous fluorescence spectroscopy.

Synchronous fluorescence spectroscopy was used in combination with principal component analysis (PCA) and linear discriminant analysis (LDA) for the differentiation of plum spirits according to their geographical origin. A total of 14 Czech, 12 Hungarian and 18 Slovak plum spirit samples were used. The samples were divided in two categories: colorless (22 samples) and colored (22 samples). Synchronous fluorescence spectra (SFS) obtained at a wavelength difference of 60 nm provided the best results. Considering the PCA-LDA applied to the SFS of all samples, Czech, Hungarian and Slovak colorless samples were properly classified in both the calibration and prediction sets. 100% of correct classification was also obtained for Czech and Hungarian colored samples. However, one group of Slovak colored samples was classified as belonging to the Hungarian group in the calibration set. Thus, the total correct classifications obtained were 94% and 100% for the calibration and prediction steps, respectively. The results were compared with those obtained using near-infrared (NIR) spectroscopy. Applying PCA-LDA to NIR spectra (5500-6000 cm(-1)), the total correct classifications were 91% and 92% for the calibration and prediction steps, respectively, which were slightly lower than those obtained using SFS.

Determination of the adulterants in adulterant–brandy blends using fluorescence spectroscopy and multivariate methods

The addition of water or ethanol to brandy is an easy way to adulterate brandy. To avoid the misleading of consumers, it is necessary to develop a reliable method to detect the adulteration of brandy. In this work excitation–emission matrix fluorescence in combination with parallel factor analysis (PARAFAC) and partial least squares (PLS) regression was used to determine the content of water, ethanol and methanol in adulterated brandy samples. Excitation–emission matrix fluorescence spectra were measured in the emission wavelength range of 510–600 nm and in the excitation wavelength range of 393–497 nm. The model created using PARAFAC-PLS was able to predict the water, ethanol and methanol level in adulterated brandy with root mean square error of prediction values of 0.24%, 0.20% and 0.22%,respectively, and coefficients of determination of prediction between the reference content and the predicted values of 0.993, 0.997 and 0.995, respectively.

Surface Behavior of Polyamide 6 Modified by Barrier Plasma in Oxygen and Nitrogen

Polyamide (PA) 6 was modified by diffuse coplanar surface barrier discharge (DCSBD) plasma in an atmosphere of nitrogen and oxygen. The surface roughness decrease of PA 6 was detected by AFM and nano-indentation after modification in DCSBD plasma. A significant increase in O/C and N/C ratios of plasma-modified PA 6 using XPS analysis was found. The results show the importance of introducing oxygenic polar functional groups on the polymeric surface in order to increase its surface energy during a short time of plasma activation. The modification of PA 6 by DCSBD oxygen plasma was more efficient than by nitrogen plasma.

FTIR spectroscopy of silicon carbide thin films prepared by PECVD technology for solar cell application

The plasma CVD reactor with parallel plate electrodes was used for plasma enhanced chemical vapor deposition (PECVD) of two type’s silicon carbide thin films on Si substrates. The concentration of elements in the films was determined by RBS and ERD analytical method simultaneously. The chemical compositions of the samples were analyzed by FTIR method. RBS and ERD results showed that the films contain silicon, carbon, hydrogen and small amount of oxygen. FTIR results confirmed the presence of Si-C, Si-H, C-H, and Si-O bonds. From the FTIR spectra the main following vibration frequencies were determined: the band from 2800 to 3000 cm-1 is attributed to stretching vibration of the CHn group in both the sp2 (2880 cm-1) and sp3 (2920 cm-1) configurations. The band at 2100 cm-1 is due to SiHm stretching vibrations. The band at 780 cm-1 can be assigned to Si-C stretching vibration. Main features of FTIR spectra were Gaussian fitted and detailed analyses of chemical bonding in SiC films were performed. Differences between two types of SiC films were discussed with the aim to using these films in the heterojunction solar cell technology.

On the use of the fluorescence, ultraviolet–visible and near infrared spectroscopy with chemometrics for the discrimination between plum brandies of different varietal origins

This paper investigates the use of synchronous fluorescence, UV-Vis and near infrared (NIR) spectroscopy coupled with chemometric methods to discriminate samples of high-quality plum brandies (Slivovica) of different varietal origins (Prunus domestica L.). Synchronous fluorescence spectra (SFS) for wavelength differences in the range of 70-100nm, NIR spectra in the wavenumber range of 4000-7500cm-1 and UV-Vis spectra in the wavelength interval of 220-320nm were compared. The best discrimination models were created by linear discriminant analysis based on principal component analysis applied to SFS recorded with wavelength difference either 80nm or 100nm, allowing the classification of plum brandy according to harvest time as early (summer) and late (autumn) plum varieties; the total correct classifications were 96% and 100% for the calibration and prediction steps, respectively.

Synthesis of cinnamic acid-derived 4,5-dihydrooxazoles

A range of cinnamic units containing 4,5-dihydrooxazoles was prepared using two different synthetic routes. The first method was based on the transformation of substituted cinnamic or benzoic acids to 2-styryl-4,5-dihydrooxazoles. Several derivatives containing phenolic groups were prepared in this manner. The second approach consisted of a reaction between the 4,5-dihydrooxazole moiety and double bond-containing compounds. These compounds contain two or more reactive centres capable of providing polymerisations and also organic reactions.