Fusing 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 none and functionalized TiO2-MWCNTs composites were analyzed by a range of analytical techniques including XRD, Raman, XPS, SEM and UV-vis diffuse reflectance spectroscopy (DRS), and dynamic light scattering (DLS). The photocatalytic activity was evaluated toward the liquid-phase degradation of methylene blue in aqueous solution under both UV and visible light irradiation. TiO2-MWCNTs with optimized mole ratio exhibit much higher photocatalytic activity and stability than bare TiO2. 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.
COBISS.SI-ID: 19155734
The adsorption of chemically similar but differently oxygen reactive phenolic-acid derivatives on the Ti-nanotubes (TiNTs) surfaces to increase and/or broaden their photo-induced activity was studied using Raman and X-ray photoelectron spectroscopies combined with zeta-potential analyses. Photo-catalytic activities and stabilities of newly synthesized particles were evaluated by using high-resolution capillary electrophoresis in combination with cyclic voltammetry and spin-trapping EPR spectroscopy. The modification with caffeic acid (CA) resulted in well-oriented and dense but oxygen semi-stable thin layer (1-3 nm) of self-assembled mono-molecular and/or bi-dentate coordinated molecules on the TiNTs' surfaces, which narrowed the band gap from 2.9 eV (for un-modified TiNTs) to 1.55 eV, but however restrict the hydroxyl radicals generation under both UV (320 nm) and VIS (450 nm) source radiations. On the other hand, the gallic acid (GA) resulted in situ polymerized GA layer through bi-dentate binding as highly-oxygen-stabilized surface structure yielding narrower band gap of 2.25 eV and increased hydroxyl radical's generation under both exposure lights. The third tested hydroxybenzoic acid (HA), resulted to an unstable layer bonded thorough single-hydrogen bonding mechanism. This work offers a new modification strategy for stable (oxygen and photo-induction related) and highly visible-light responded TiNTs as photocatalyst.
COBISS.SI-ID: 18155542