Ewelina Kusiak-Nejman

Comparison of Methods for Evaluation of the Bactericidal Activity of Copper-Sputtered Surfaces against Methicillin-Resistant Staphylococcus aureus

ABSTRACT Bacteria can survive on hospital textiles and surfaces, from which they can be disseminated, representing a source of health care-associated infections (HCAIs). Surfaces containing copper (Cu), which is known for its bactericidal properties, could be an efficient way to lower the burden of potential pathogens. The antimicrobial activity of Cu-sputtered polyester surfaces, obtained by direct-current magnetron sputtering (DCMS), against methicillin-resistant Staphylococcus aureus (MRSA) was tested. The Cu-polyester microstructure was characterized by high-resolution transmission electron microscopy to determine the microstructure of the Cu nanoparticles and by profilometry to assess the thickness of the layers. Sputtering at 300 mA for 160 s led to a Cu film thickness of 20 nm (100 Cu layers) containing 0.209% (wt/wt) polyester. The viability of MRSA strain ATCC 43300 on Cu-sputtered polyester was evaluated by four methods: (i) mechanical detachment, (ii) microcalorimetry, (iii) direct transfer onto plates, and (iv) stereomicroscopy. The low efficacy of mechanical detachment impeded bacterial viability estimations. Microcalorimetry provided only semiquantitative results. Direct transfer onto plates and stereomicroscopy seemed to be the most suitable methods to evaluate the bacterial inactivation potential of Cu-sputtered polyester surfaces, since they presented the least experimental bias. Cu-polyester samples sputtered for 160 s by DCMS were further tested against 10 clinical MRSA isolates and showed a high level of bactericidal activity, with a 4-log10 reduction in the initial MRSA load (106 CFU) within 1 h. Cu-sputtered polyester surfaces might be of use to prevent the transmission of HCAI pathogens.

Preparation and characterisation of TiO2 thermally modified with cyclohexane vapours

In this study a simple method of preparation of UV-vis light-active TiO2 photocatalysts is presented. The new photocatalysts were obtained by thermal modification of the anatase TiO2 powder (Police, Poland) with cyclohexane. The obtained materials were investigated by means of UV-vis/DR, FTIR/DRS, XRD. BET specific surface area and carbon content was also measured. Furthermore, photocatalytic activity of the new photocatalysts were investigated under UV-vis irradiation with high UV light intensity during of phenol degradation. TiO2/C photocatalysts show higher photocatalytic activity in comparison with TiO2-starting and commercial KRONOClean 7000, regardless of calcination temperature. It was found that the smaller amount of carbon in TiO2/C photocatalyst sample the better photocatalytic activity of tested nanomaterials.

The Photocatalytic Performance of Benzene- Modified TiO2 Photocatalysts under UV-vis Light Irradiation

Abstract In this study a photocatalytic performance of new carbon-modified titanium dioxide photocatalysts was discussed. Benzene was used as carbon precursor. It was found that the photocatalytic activity of obtained samples increases with the increase of modification temperature and decrease of carbon concentration present in TiO2/C samples. This could be related to the kind of interactions between TiO2 surface and carbon from thermal decomposition of benzene. The higher calcination temperature the less carbon deposits on the surface of modified samples and the higher probability of the Ti and C interaction confirmed by means of UV-vis/DR studies. It was proved that the photocatalytic activity of carbon modified titania nanomaterials strongly depends on carbon content in TiO2/C photocatalysts. Modification of starting TiO2 with benzene is a promising method especially by taking into account the mineralization of phenol and the co-products of its degradation.

Modification of Titanium Dioxide with Graphitic Carbon from Anthracene Thermal Decomposition as a Promising Method for Visible- Active Photocatalysts Preparation

Abstract This work investigated the photocatalytic performance of TiO2 photocatalysts modified with graphitic carbon under visible light with a very small component of UV. The graphitic carbon modification was conducted at 200-500 °C using thermal anthracene decomposition. The increase of calcination temperature leads to typical increase of crystallites size, decrease of the specific surface area and carbon content in modified samples. The characteristic peak for a skeletal in-plane vibrations of the anthracene ring located at 1522 cm-1 as well as the band at 1410 cm-1 assigned to C=C aromatic stretching vibrations mode were possible to observe. The analysis of the morphology using SEM confirmed the presence on new multi-layer carbonaceous flakes decorated with TiO2 nanoparticles. TEM analysis and Raman studies proved the presence of graphitic structures covering the surface of the prepared TiO2/C photocatalysts. The highest photocatalytic activity, calculated on the basis of phenol photodegradation under visible light, was found for the photocatalyst modified with graphitic carbon at 400 °C (TiO2/C-400).

Assessment of the Suitability of the One-Step Hydrothermal Method for Preparation of Non-Covalently/Covalently-Bonded TiO2/Graphene-Based Hybrids

A hybrid nanocomposites containing nanocrystalline TiO2 and graphene-related materials (graphene oxide or reduced graphene oxide) were successfully prepared by mechanical mixing and the hydrothermal method in the high-pressure atmosphere. The presented X-ray photoelectron spectroscopy (XPS) study and quantitative elemental analysis confirm similar content of carbon in graphene oxide GO (52 wt% and 46 wt%, respectively) and reduced graphene oxide rGO (92 wt% and 98 wt%, respectively). No chemical interactions between TiO2 and GO/rGO was found. TiO2 nanoparticles were loaded on GO or rGO flakes. However, Fourier transform infrared-diffuse reflection spectroscopy (FTIR/DRS) allowed finding peaks characteristic of GO and rGO. XPS study shows that since the concentration of TiO2 in the samples was no less than 95 wt%, it was assumed that the interactions between TiO2 and graphene should not influence the lower layers of titanium atoms in the TiO2 and they occurred as Ti4+ ions. Hydrothermal treatment at 200 °C did not cause the reduction of GO to rGO in TiO2-GO nanocomposites. In general, the one-step hydrothermal method must be considered to be inefficient for preparation of chemically-bonded composites synthesized from commercially available TiO2 and unfunctionalized graphene sheets obtained from graphite powder.

Cementitious Plates Containing TiO2-N,C Photocatalysts for NOx Degradation

Abstract Studies of photocatalytic decomposition of NOx on cementitious plates modified by TiO2-N,Cphotocatalysts are presented. The cementitious plates were obtained by addition of 10 or 20 wt. % of different types of titanium dioxide, such as commercial P25, pure TiO2 and carbon and nitrogen modified TiO2 (TiO2-N,C) to cement.TiO2- N,C photocatalysts were obtained by heating up the starting TiO2 (Grupa Azoty Zakłady Chemiczne Police S.A) in the atmosphere of ammonia and carbon at the temperature 100, 300 i 600 °C. Used photocatalyst were characterized by FTIR/DRS, UV-Vis/DR i XRD methods. Surfaces of modified cementitious plates were studied by optical scanning microscope and the contact angle measurements. Photocatalytic activity of tested materials was done during NOx decomposition. The highest photocatalytic activity has cementitious plate with 20wt.% addition of TiO2-N,C obtained at 300°C.