Photocatalytic reactions on the surface of TiO2 involve not only photo-excited holes and electrons, but also oxidatively or reductively generated reactive oxygen species (ROS) such as OH, O2 -. and H2O2 even in the absence of specific irradiation with UV light. Their behaviour has not yet been fully understood. When ROS desorbs from the TiO2 surface and diffuse into the gas or aqueous phase, their toxicity is questionable. ROS may cause, if produced in excess, oxidative stress or may act as signalling molecules for the immune system. One example is TiO2 powder used in sunscreen formulations, where free radicals generated under sunlight irradiation are responsible for toxic effects. In order to limit the transportation of ROS from the TiO2 surfaces into the gas phase, in this contribution we present new photoactive TiO2-MWCNT nanocomposites with antioxidant modified surfaces, which can capture ROS species. The TiO2-MWCNT nanocomposites were surface functionalized by using laccase as catalyst to attaching gallic acid polymerized molecules on the nanocomposite surface. Structure and surface functionalization was investigated by X-ray, infrared and UV-vis diffuse reflectance spectroscopy analysis. The antioxidant activity was analyzed using 2,2- azino-bis(3-ethylbenzothiazoline-6-sul- phonic acid) and photocatalytic activity toward the liquidphase degradation of methylene blue in aqueous solution under both UV and visible light irradiation.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 18806294Among various semiconductors, titanium dioxide (TiO2) is the most studied photocatalysts because of its high photocatalytic activity, non-toxicity, low cost and photochemical stability in the reaction conditions. However, the low quantum efficiency, owing to the fast recombination of photo generated hole-electron pairs and limited response to sunlight irradiation because of wide band-gap of TiO2 greatly limited its practical application. On the other hand, multiwalled carbon nanotubes (MCNTs) present an appropriate template for materials with field-emission displays and photocatalytic properties. Thus, a combination of TiO2 and MCNTs could potentially create many active sites yielding increased photocatalytic activity. In this work, we focused on the sonochemical, combined with calcination process for the preparation of TiO2-carbon nanotube composites with different mole ratio of titanium and carbon. Synthesised TiO2-carbon nanotubes exhibit an enormous surface area, which is responsible for the high agglomeration tendency. Therefore, we post functionalized TiO2-carbon nanotubes with enzymatic in situ synthesized soluble aromatic polymers. This enzymatic procedure is based on the direct attack of the sp2 carbon on the MCNT surface through a free radical process, allowing having a certain control of the yield of functionalization without destroying the MCNTs original structure. The bare MCNTs and the functionalized TiO2-carbon nanotube composites were characterized by a range of analytical techniques including Raman, ultraviolet-visible (UV-vis) and X-Ray photoelectron (XPS) spectroscopies, scanning electron microscopy (SEM) and thermogravimetric and differential scanning calorimetry analysis (TGA-DSC). The photocatalytic activity was evaluated toward the degradation of methylene blue in aqueous solution under both UV and visible light irradiation. The results indicated that the soluble aromatic polymers were grafted covalently on the surface of MCNTs successfully, and the functionalized TiO2-carbon nanotube composites exhibit higher aquatic solubility.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 18545430Fusing multiwall carbon nanotubes (MWCNTs) with TiO2 at the nano-scale level promotes the separation of the electron-hole charges generated upon UV and day light irradiation. In this study, we investigated facile sonochemical synthesis, combined with calcination process for the preparation of TiO2-MWCNT composites with different mole ratio of titanium and carbon. In order to produce stable nano dispersions, we exploited an innovative biotechnology-based approach for the covalent functionalization of TiO2-MWCNTs with in-situ synthesized soluble phenoxazine dye molecules. The as-prepared TiO2-MWCNTs photocatalyst possessed good adsorptivity of dyes, extended light absorption range and efficient charge separation properties simultaneously. The results indicated that the soluble phenoxazine dyes and amino-benzensulfonic acid monomers were covalently grafted on the surface of TiO2-MCNTs, which promoted good aquatic dispersibility and extended light absorption, issuing in increased photocatalytic efficiency.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 18791702In the contribution we have presented the development and the optimization of the designing the TiO2 hybrids based on combinatorial approaches to both TiO2 structure design and the exploration of TiO2 surface interactions with organic phenolic acids. New findings about the properties, modification and permanent application of inorganic nano-particles such as TiO2 and its hybrids with various organic phenolic compounds have enormous contribution to the enrichments of fundamental knowledge (correlation between reactivity, structure and surface properties) as well as applicable knowledge (introduction of new stable structures and testing methods, and development of new technologies) from this area; and to the development of new nano materials with multi-functional properties.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 17828630