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Cu and Zr surface sites in photocatalytic activity of TiO [sub] 2 nanoparticles
Olena Pliekhova, O. L. Pliekhov, Mattia Fanetti, Iztok Arčon, Nataša Novak Tušar, Urška Lavrenčič Štangar, 2019, izvirni znanstveni članek

Opis: The present work is focused on the role of ZrO2 modification in the performance of CuO modified TiO2. Zirconia loading leads to formation of more resistant photocatalytic layers compared to samples modified with only copper containing species. Surface modification of mixed phase TiO2 with CuO/ZrO2 improves the degradation of Reactive blue 19 dye under simulated solar irradiation. An in-depth investigation of the catalysts showed that in case of CuO/ZrO2 modification, the covering of the TiO2 surface with zirconium containing species prevents morphological and harmful energetic changes induced by copper species formed on the rutile TiO2 phase at a higher copper loading.
Najdeno v: osebi
Ključne besede: titanium dioxide, surface modification, XAS analysis, surface acidity, Hammett indicators
Objavljeno: 26.03.2019; Ogledov: 726; Prenosov: 0
.pdf Polno besedilo (996,21 KB)

Au and Ag on the Bi2Se3(0001) Surface: Experimental Electronic and Physical Properties
Sandra Gardonio, Mattia Fanetti, Katja Ferfolja, Matjaž Valant, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Binary bismuth chalcogenides, Bi2Se3 and Bi2Te3, have been extensively studied as reference topological insulators (TIs). These materials are bulk insulators with topological surface states (TSS) crossing the Fermi level. In contrast to conventional surface states of metals, the TSS are extremely robust against local modifications at the surface, such as adsorbed adatoms, localized defects or changes in the surface termination. This aspect makes the TIs attractive for applications in spintronics, plasmonics, quantum computing and catalysis. A theoretical model of charge transport by the TI surface states predicts that the TSS survive, provided that bonding at the metal/TI interface is weak. Ab-initio calculations have been done to understand the electronic properties of Au, Ni, Pt, Pd and graphene layers in a contact with Bi2Se3. These calculations showed that for Au and graphene the spin-momentum locking of TSS is maintained at the interface. In another theoretical study, Ag and Au thin layers on Bi2Se3 have been predicted to show a large Rashba splitting and a high spin polarization of the Ag quantum wells, providing a great potential for development of the spintronic devices. Finally, the calculations have foreseen that the presence of the robust TSS affects the adsorption properties of metals (Au bi-layer and clusters of Au, Ag, Cu, Pt, and Pd) supported on TI, in some cases resulting in the enhancement of the catalytic processes. Despite the fundamental importance of the metal/TI interfaces and a number of theoretical studies predicting exotic interfacial phenomena, the experimental knowledge about the metals on the TI surfaces is surprisingly limited, especially concerning combined study of morphology, growth mode, electronic and chemical properties. In order to exploit the predicted physical properties of such systems, it is especially important to extend the study above the diluted coverage regime and to understand what is the growth morphology of the metal on the TI surface, to what extent the metal overlayer interacts with the TI substrate, how the TSS change with the presence of the metal overlayer and what is the reactivity of the system at the different stages of the overlayer growth. Within this frame, we present a comprehensive surface sensitive study, of Au and Ag on Bi2Se3 by means of ARPES, XPS, SEM, LEED and XRD. The obtained results allow us to discuss the relation between electronic and physical properties at two of the most important model metal/TI interfaces
Najdeno v: osebi
Ključne besede: topological insulator, electronic properties, synchrotron radiation
Objavljeno: 27.06.2019; Ogledov: 704; Prenosov: 0
.pdf Polno besedilo (5,72 MB)

A DNA origami plasmonic sensor with environment-independent read-out
Matjaž Valant, Mattia Fanetti, 2019, izvirni znanstveni članek

Najdeno v: osebi
Ključne besede: DNA origami, plasmonic sensor, molecular detection, gold nanoparticle
Objavljeno: 08.11.2019; Ogledov: 554; Prenosov: 0
.pdf Polno besedilo (2,72 MB)

Looking for a topological insulator in the tetradymite family
Matjaž Valant, Paolo Moras, P. M. Sheverdyaeva, Mattia Fanetti, Zipporah Rini Benher, Sandra Gardonio, 2019, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Materials that are topological insulators (TI) manifest a novel state for their electrons. They possess topological surface states that are not destroyed by the presence of non-magnetic impurities on their surfaces. This unique property lies in the bulk band structure and it is typically found in narrow gap semiconductor with strong spin-orbit coupling. Bi2Se3 and Bi2Te3 belong to the class of compounds called tetradymites and are considered as the 3D-prototypical TI materials. However, these compounds are not usually insulators but have metallic bulk conductivity as a consequence of intrinsic defect doping: vacancies and anti-site defects. For these reasons, it is difficult to electrically gate these materials for the manipulation and control of charge carriers for realizing devices. This led to the search for other topological materials, which might have better insulating behavior in their bulk. Theoretical studies have pointed out that ternary variants of the Bi2Se3 and Bi2Te3, such as Bi2Te2Se, Bi2Te2S, Bi2Se2S Sb2Te2Se and Sb2Te2S, should be stable TIs and potentially offer a chemical way to control TI behavior, in particular by lowering native doping. Among the cited ternary compounds, Bi2Se2S should manifest a genuine topological spin-transport regime hosting an isolated Dirac cone with the Dirac point in the gap as well. However, it has been poorly studied from the TI experimental perspective. Therefore, to uncover the full potential of the predicted topological electronic properties of the Bi-Se-S system, in this presentation we will revisit the crystallographic and electronic structure of Bi2Se3-Bi2S3 solid solutions. The combined use of bulk and surface sensitive techniques such as X-ray diffraction (XRD), low energy electron diffraction (LEED), scanning electron microscopy (SEM) with Energy Dispersive X-ray spectroscopy (EDX) and X-ray photoemission spectroscopy (XPS) was applied to analyze single crystal samples grown by us. The quality of the single crystals was suitable for rigorous measurement of the electronic properties by means of Angle Resolved Photoemission Spectroscopy. We unambiguously showed that within a certain solid solution range, the single crystals of Bi-Se-S have a rombohedral structure with the topological surface states as theoretically predicted.
Najdeno v: osebi
Ključne besede: topological insulators, ternary tetradymite, electronic properties.
Objavljeno: 19.12.2019; Ogledov: 635; Prenosov: 0
.pdf Polno besedilo (6,45 MB)

Interfacial reaction, morphology and growth mode of metals on topological insulator surfaces
Sandra Gardonio, Mattia Fanetti, Katja Ferfolja, Matjaž Valant, 2019, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: osebi
Ključne besede: topological insulators, surfaces, metals
Objavljeno: 19.12.2019; Ogledov: 587; Prenosov: 0
.pdf Polno besedilo (18,68 MB)

Improved photocatalytic activity of anatase-rutile nanocomposites induced by low-temperature sol-gel Sn-modification of TiO2
Ksenija Maver, Iztok Arčon, Urška Lavrenčič Štangar, Mattia Fanetti, Saim Emin, Matjaž Valant, 2020, izvirni znanstveni članek

Opis: The Sn-modified TiO2 photocatalysts are prepared by low-temperature sol-gel processing based on organic titanium and tin precursors with varied Sn concentrations (from 0.1–20 mol .%). The role of Sn dopant as the promotor of the formation of TiO2 rutile crystalline phase is explained and the optimal Sn concentration for preparation of efficient Sn-modified titania photocatalyst is determined. Up to 40 % increase in photocatalytic activity is achieved in Sn-modified TiO2 photocatalytic thin films dried at 150 °C with low Sn concentrations in the range from 0.1 to 1 mol .%. At low Sn concentrations optimal ratio between anatase and rutile (nano)crystals is obtained, which facilitates charge separation at the TiO2 photocatalyst’s surface. When the concentration of Sn increases above 5 mol.% or when the films are calcined at 500 °C, the relative amount of rutile phase with inferior photocatalytic activity, increases and the nanocrystals of titania grow, leading to fewer active sites per unit mass and the reduction of activity in comparison to unmodified TiO2.
Najdeno v: osebi
Ključne besede: Anatase-rutile Sn-modified TiO2 XAS analysis Photocatalytic activity
Objavljeno: 10.02.2020; Ogledov: 401; Prenosov: 0
.pdf Polno besedilo (537,61 KB)

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