Agnieszka Wanag

Antibacterial properties of TiO2 modified with reduced graphene oxide

In this paper, the antibacterial activity of titanium dioxide modified with reduced graphene oxide (rGO) was presented. TiO2/rGO photocatalysts were prepared by the hydrothermal method under elevated pressure at 180°C and heated at 100°C in Ar flow. The obtained photocatalysts were characterized by means of XRD, FTIR/DRS, UV-vis/DR, Raman spectroscopy and scanning electron microscopy (SEM). The carbon content was also examined. FTIR/DRS and Raman analysis confirmed the presence of rGO in the TiO2 structure, suggesting a successful modification. The antimicrobial photoactivity of photocatalysts was conducted against E. coli under an artificial solar light. The results show that all TiO2/rGO photocatalysts exhibited an antibacterial activity higher than unmodified TiO2. The best result was found for sample with 1.5wt% additive of reduced graphene oxide. In this case, total inactivation of E. coli was noticed after 75min of irradiation. It was found that the presence of rGO in sample improves the antimicrobial activity.

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.

Nitrogen-Modified Titanium Dioxide as an Adsorbent for Gaseous SO2

In this study, sorption of gaseous SO2 on nitrogen-modified titanium dioxide (TiO2/N) materials was investigated. The TiO2/N materials were prepared by thermal modification of commercial TiO2 in gaseous ammonia flow. First, TiO2 was calcined at 100–700 °C (Δt = 200 °C). The obtained samples were then rinsed with water to remove the residual ammonium groups adsorbed on the TiO2 surface. The influence of modification temperature, BET surface area, pore volume and nitrogen content on the efficiency of SO2 sorption on TiO2 surface was discussed. The best result was obtained for nitrogen-modified material that is heat treated at 100 °C. The total sorption capacity calculated for this sample was 20.96 mg SO2/1 g TiO2. It was shown that TiO2 modified with nitrogen at low temperature can be a very effective sorbent in capturing SO2 particles.