Dynamics of Confined Short-Chain alkanol in MCM-41 by Dielectric Spectroscopy: Effects of matrix and system Treatments and Filling Factor

The dynamics of n-propanol confined in regular MCM-41 matrix with the pore size Dpore = 40 Å, under various matrix conditioning and sample confining conditions, using broadband dielectric spectroscopy (BDS), is reported. First, various drying procedures with the capacitor filling under air or N2 influence the BDS spectra of the empty MCM-41 and the confined n-PrOH/MCM-41 systems, but have a little effect on the maximum relaxation time of the main process. Finally, various filling factors of n-PrOH medium in the optimally treated MCM-41 system lead to unimodal or bimodal spectra interpreted in terms of the two distinct dynamic phases in the confined states.This research was funded by the EUSMI/Horizon 2020 grants: E181200215 and E 180300076 and E180300077 and by the Slovak Research and Development Agency (SRDA) under the contract No. APVV-16-0369. And J.B. was funded by the VEGA Agency, Slovakia with Grant No. 2/0030/16

Highly Efficient Antibacterial Polymer Composites Based on Hydrophobic Riboflavin Carbon Polymerized Dots

Development of new types of antimicrobial coatings is of utmost importance due to increasing problems with pathogen transmission from various infectious surfaces to human beings. In this study, new types of highly potent antimicrobial polyurethane composite films encapsulated by hydrophobic riboflavin-based carbon polymer dots are presented. Detailed structural, optical, antimicrobial, and cytotoxic investigations of these composites were conducted. Low-power blue light triggered the composites to eradicate Escherichia coli in 30 min, whereas the same effect toward Staphylococcus aureus was reached after 60 min. These composites also show low toxicity against MRC-5 cells. In this way, RF-CPD composites can be used for sterilization of highly touched objects in the healthcare industry

Bactericidal and antioxidant bacterial cellulose hydrogels doped with chitosan as potential urinary tract infection biomedical agent

Therapy of bacterial urinary tract infections (UTIs) and catheter associated urinary tract infections (CAUTIs) is still a great challenge because of the resistance of bacteria to nowadays used antibiotics and encrustation of catheters. Bacterial cellulose (BC) as a biocompatible material with a high porosity allows incorporation of different materials in its three dimensional network structure. In this work a low molecular weight chitosan (Chi) polymer is incorporated in BC with different concentrations. Different characterization techniques are used to investigate structural and optical properties of these composites. Radical scavenging activity test shows moderate antioxidant activity of these biocompatible composites whereasin vitrorelease test shows that 13.3% of chitosan is released after 72 h. Antibacterial testing of BC-Chi composites conducted on Gram-positive and Gram-negative bacteria causing UTIs and CAUTIs (Escherichia coli,Pseudomonas aeruginosa,Klebsiella pneumoniae) and encrustation (Proteus mirabilis) show bactericidal effect. The morphology analysis of bacteria after the application of BC-Chi shows that they are flattened with a rough surface, with a tendency to agglomerate and with decreased length and width. All obtained results show that BC-Chi composites might be considered as potential biomedical agents in treatment of UTIs and CAUTIs and as a urinary catheter coating in encrustation prevention

Physical-Mechanical Properties of Waterproofing Materials Applied to Roofs in the Context of UV Degradation

The subject of the article is a physical-mechanical analysis of waterproofing materials exposed to an external environment. Physical and mechanical properties have a direct impact on the life of waterproofing materials and their later remediation. In the introduction, the factors influencing the properties of waterproofing materials are presented. The main part of the article covers the basic possibilities of testing the materials testing the materials, normative testing conditions, and critical aspects of their implementation. In this article we deal with the laboratory testing of a waterproofing membrane based on PVC-P in terms of its degradation from UV radiation, humidity, and the temperature

Why Natural or Electron Irradiated Sheep Wool Show Anomalous Sorption of Higher Concentrations of Copper(II)

Sorption of higher concentrations of Cu(II) solution onto natural sheep wool or wool irradiated by an electron beam was studied. Sorption isotherms were of unexpected character, showing extremes. The samples with lower absorbed doses adsorbed less than non-irradiated wool, while higher doses led to increased sorption varying with both concentration and dose. FTIR spectra taken from the fibre surface and bulk were different. It was concluded that there was formation of Cu(II)-complexes of carboxylic and cysteic acids with ligands coming from various keratin macromolecules. Clusters of chains crosslinked through the ligands on the surface limit diffusion of Cu(II) into the bulk of fibre, thus decreasing the sorption. After exhausting the available ligands on the surface the remaining Cu(II) cations diffuse into the keratin bulk. Here, depending on accessibility of suitable ligands, Cu(II) creates simple or complex salts giving rise to the sorption extremes. Suggestion of a mechanism for this phenomenon is presented

Some Properties of Electron Beam-Irradiated Sheep Wool Linked to Cr(III) Sorption

We examined the characteristics of an electron beam irradiated wool with an absorbed dose of (21–410) kGy in comparison with natural wool with respect to the determination of the isoelectric point (IEP), zero charge point (ZCP), mechanism of Cr(III) sorption from higher concentrated solutions, and the modelling of the wool-Cr(III) interaction. The data of ZPC and IEP differed between natural and irradiated samples. Increasing the dose shifted the pH of ZPC from 6.85 for natural wool to 6.20 for the highest dosed wool, while the natural wool IEP moved very little, from pH = 3.35 to 3.40 for all of the irradiated samples. The sorption experiments were performed in a pH bath set at 3.40, and the determination of the residual Cr(III) in the bath was performed by VIS spectrometry under optimized conditions. The resulting sorptivity showed a monotonically rising trend with increasing Cr(III) concentration in the bath. Lower doses, unlike higher doses, showed better sorptivity than the natural wool. FTIR data indicated the formation of complex chromite salts of carboxylates and cysteinates. Crosslinks via ligands coming from different keratin chains were predicted, preferably on the surface of the fibers, but to a degree that did not yet inhibit the diffusion of Cr(III)-cations into the fiber volume. We also present a concept of a complex octahedral structure

Photo-induced Electron Emission of Nanostructured Carbon Thin Film Based Transmission Photocathodes at Different Electric Field

Very thin nanostructured carbon films were deposited on quartz substrate by reactive magnetron sputtering using graphite target and gas mixture of Ar and reactive gas N2 or N2+H2. Film thicknesses were in the range of 20–25 nm. Rutherford backscatter- ing spectrometry and Elastic recoil detection analytical method determined the concentration of elements in the films. Scanning electron microscopy scanned the sur- face morphology of carbon films. Raman spectroscopy was used for chemical structural properties determina- tion of very thin carbon films. Raman spectra intensi- ties were fitted with Gaussian peaks. The photo-induced (pulsed laser - 266 nm) electron emission properties of very thin nanostructured carbon films were investigated by the measurement of cathode bunch charge at differ- ent electric field and calculate quantum efficiency. The influence of different electric field on the photo-induced electron emission characteristics of prepared transmis- sion photocathodes are 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 (PE CVD) technique. The flow rates of SiH 4 , CH 4 and NH 3 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.Slovak Research and Development Agency APVV [APVV-0109-10]; Centre of Excellence SAS for Functionalized Multiphase Materials (FUN-MAT), Grant Agency VEGA [2/0151/12]; Centre of Excellence SAS for Functionalized Multiphase Materials (FUN-MAT), MNT-ERA. Net II [794]; European Regional Development Fund; Czech Republic [CZ.1.05/2.1.00/03.0111