Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bologna study programme

Options:
  Reset


1 - 3 / 3
First pagePrevious page1Next pageLast page
1.
The role of lattice defects on the optical properties of TiO[sub]2 nanotube arrays for synergistic water splitting
Manel Machreki, Takwa Chouki, Georgi Tyuliev, Mattia Fanetti, Matjaž Valant, Denis Arčon, Matej Pregelj, Saim Emin, 2023, original scientific article

Abstract: In this study, we report a facile one-step chemical method to synthesize reduced titanium dioxide (TiO2) nanotube arrays (NTAs) with point defects. Treatment with NaBH4 introduces oxygen vacancies (OVs) in the TiO2 lattice. Chemical analysis and optical studies indicate that the OV density can be significantly increased by changing reduction time treatment, leading to higher optical transmission of the TiO2 NTAs and retarded carrier recombination in the photoelectrochemical process. A cathodoluminescence (CL) study of reduced TiO2 (TiO2–x) NTAs revealed that OVs contribute significantly to the emission bands in the visible range. It was found that the TiO2 NTAs reduced for a longer duration exhibited a higher concentration of OVs. A typical CL spectrum of TiO2 was deconvoluted to four Gaussian components, assigned to F, F+, and Ti3+ centers.
Keywords: TiO2 nanotubes, defects, cathodoluminescence
Published in RUNG: 13.12.2023; Views: 481; Downloads: 7
.pdf Full text (5,75 MB)
This document has many files! More...

2.
Unraveling the arrangement of Al and Fe within the framework explains the magnetism of mixed-metal MIL-100(Al,Fe)
Gregor Mali, Matjaž Mazaj, Iztok Arčon, Darko Hanžel, Denis Arčon, Zvonko Jagličić, 2019, original scientific article

Abstract: Properties of mixed-metal MOFs depend on the distribution of different metals within their frameworks. Determination of this distribution is often very challenging. Using an example of aluminum- and iron-containing MIL-100, we demonstrate that 27Al NMR spectroscopy, when combined with first-principles calculations and magnetic, X-band electron paramagnetic resonance, Fe K-edge extended X-ray absorption fine structure, and Mössbauer measurements, enables one to accurately determine the arrangement of Al and Fe within the metal trimers, which are the basic building units of MIL-100. In this particular material, the incorporation of Fe and Al on the framework metal sites is random. Crucial for deciphering the arrangement is detecting NMR signals, shifted because of the strong hyperfine interaction between the 27Al nuclei and the unpaired electronic spins of Fe3+ ions, assigning the shifted signals aided by first-principles calculations of hyperfine couplings, and quantitatively evaluating the NMR intensities and the measured effective magnetic moment.
Keywords: Fe EXAFS, XANES, MIL100, MOF, magnetizem
Published in RUNG: 26.03.2019; Views: 3323; Downloads: 0
This document has many files! More...

3.
Surface modified titanium dioxide using transition metals : nickel as a winning transition metal for solar light photocatalysis
Andraž Šuligoj, Iztok Arčon, Matjaž Mazaj, Goran Dražić, Denis Arčon, Pegie Cool, Urška Lavrenčič Štangar, Nataša Novak Tušar, 2018, original scientific article

Abstract: Titanium dioxide has been widely used as an antimicrobial agent, UV-filter and catalyst for pollution abatement. Herein, surface modifications with selected transition metals (Me) over colloidal TiO2 nanoparticles and immobilization with a colloidal SiO2 binder as composite films (MeTiO2/SiO2) on a glass carrier were used to enhance solar-light photoactivity. Colloidal TiO2 nanoparticles were modified by loading selected transition metals (Me ¼ Mn, Fe, Co, Ni, Cu, and Zn) in the form of chlorides on their surface. They were present primarily as oxo-nanoclusters and a portion as metal oxides. The structural characteristics of bare TiO2 were preserved up to an optimal metal loading of 0.5 wt%. We have shown in situ that metal-oxo-nanoclusters with a redox potential close to that of O2/O2 were able to function as co-catalysts on the TiO2 surface which was excited by solar-light irradiation. The materials were tested for photocatalytic activity by two opposite methods; one detecting O2 (reduction, Rz ink test) while the other detecting OH (oxidation, terephthalic acid test). It was shown that the enhancement of the solar-light activity of TiO2 by the deposition of transition metal oxo-nanoclusters on the surface depends strongly on the combination of the reduction potential of such species and appropriate band positions of their oxides. The latter prevented excessive self-recombination of the photogenerated charge carriers by the nanoclusters in Ni and Zn modification, which was probably the case in other metal modifications. Overall, only Ni modification had a positive effect on solar photoactivity in both oxidation and reduction reactions.
Keywords: surface modified TiO2, XANES, EXAFS, Nickel, solar light photocatalyst
Published in RUNG: 01.06.2018; Views: 3604; Downloads: 0
This document has many files! More...

Search done in 0.02 sec.
Back to top