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
This study confirms the enzyme-mediated phosphorylation of cellulose nanofibers (CNF) by using hexokinase and adenosine-5′-triphosphate in the presence of Mg-ions, resulting in a phosphate group’s creation in the cellulose monomer rings. A proof-of-concept is provided using 12C CPMAS, 31P MAS nuclear magnetic resonance, attenuated total reflectance-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) analyzing methods. The degree of substitution (DS) is determined by elemental analysis and compared to DS estimated by XPS analysis. From the thermal degradation measurements using thermo-gravimetric analysis, the C-6-O phosphorylation was found to noticeably prevent the CNF derivatives from weight loss in the pyrolysis process, thus, providing them flame-resistance functionality. Furthermore, phosphorylation significantly enhanced adsorption capacity of Fe3+ ions making them interesting for fabrication of biobased filters and membranes. Finally, the biomimetic growth of Ca–P crystals (hydroxyapatite) in simulated body fluid was characterized by scanning electron microscopy and energy dispersive X-ray, showing potential application as biomedical materials.
COBISS.SI-ID: 17810198