21. New strategy for magnetic gas sensingRoberta Ciprian, Piero Torelli, Angelo Giglia, B Gobaut, Barbara Ressel, Janez Štupar, Matija Stupar, Antonio Caretta, Giovanni De Ninno, Tommaso Pincelli, Barbara Casarin, Ganesh Adhikari, G Sberviglieri, C Baratto, Marco Malvestuto, 2016, izvirni znanstveni članek Najdeno v: ključnih besedah Ključne besede: hybrid nanostructures, sensor, absorption spectroscopy Objavljeno: 05.02.2018; Ogledov: 3141; Prenosov: 0
Polno besedilo (2,25 MB) |
22. Conclusively Addressing the CoPc Electronic Structure: A Joint Gas- Phase and Solid-State Photoemission and Absorption Spectroscopy StudyMarcello Coreno, Monica de Simone, Ieva Bidermane, Y. Sassatelli, R. Ovsyannikov, Erika Giangrisostomi, C. Grazioli, J. Lüder, Valeria Lanzillotto, I.E. Brumboiu, Teng Zhang, Barbara Ressel, Matija Stupar, Maddalena Pedio, Petra Rudolf, Barbara Brena, Carla Puglia, 2017, izvirni znanstveni članek Najdeno v: ključnih besedah Ključne besede: Cobalt Phtalocyanine, photoemission spectroscopy, gas phase, solid state Objavljeno: 07.02.2018; Ogledov: 3406; Prenosov: 0
Polno besedilo (1,38 MB) |
23. Giant magneto–electric coupling in 100 nm thick Co capped by ZnO nanorodsGiovanni Vinai, Barbara Ressel, Piero Torelli, Federico Loi, Benoit Gobaut, Regina Ciancio, Barbara Casarin, Antonio Caretta, Luca Capasso, Fulvio Parmigiani, Francesco Cugini, Massimo Solzi, Marco Malvestuto, Roberta Ciprian, 2018, izvirni znanstveni članek Najdeno v: ključnih besedah Ključne besede: ZnO nanorods, Cobalt, X-rays absorption near edge spectroscopy Objavljeno: 07.02.2018; Ogledov: 3143; Prenosov: 0
Polno besedilo (3,44 MB) |
24. Amorphous nanocomposite of polycarbosilanes and aluminum oxideAndraž Mavrič, 2018, doktorska disertacija Opis: This work presents a paradigm for high temperature stabilization of bulk amorphous aluminium oxide. The thermodynamic stabilization is achieved by preparing a nanocomposite, where polymethylsilane dendritic molecules are dispersed in an aluminium hydroxide gel. Upon heat-treatment the gel transforms to the amorphous aluminium oxide that is stable up to 900°C. The dispersion of the macromolecules and their covalent bonding to the alumina matrix induce homogeneously distributed strain fields that keep the alumina amorphous.
The first part of the thesis focuses on the synthesis, characterization and solubility properties of the dendritic polymethylsilane. The polymethylsilane is synthetized by electrochemical polymerization from trichloromethylsilane monomer. The polymerization mechanism, involving a single polymerization pathway, is identified. The polymer growth proceeds through reduction of the monomers to the silyl anions and their addition to the growing polymer.
The solubility of three chemically related but topologically different polysilanes (linear, dendritic and network) were studied by dynamic light scattering. At room temperature the agglomerates in a range from 500 to 1300 nm are present. They undergo de-agglomeration at slightly elevated temperatures of around 40°C. The de-agglomeration results in formation of stable solutions, where a hydrodynamic diameter of the individual polymer molecules was measured to be in a range from 20 to 40 nm.
The obtained diameters of two dendritic polymethylsilane macromolecules, synthesized under different electrolysis conditions, are much larger than the theoretical size estimated for an ideal dendrimer. We determined by 29Si NMR that the reason for this is in a large number of branching irregularities (defects) contained in the molecular structure. Combining the experimental values obtained by DLS and density measurements with a structural model that considers the branching irregularities, it is shown that the inclusion of the defects allows the dendritic polymer to exceed the sterical limitations and form the hyperbranched dendritic structure. The final size depends on a relative amount of the branching defects.
In the second part, the synthetized polymethylsilane molecules were successfully used for the nanocomposite formation. The aluminium hydroxide gel with the dispersed polymethylsilane molecules was prepared as a precursor. Upon heat-treatment it gives the amorphous aluminium oxide stable up to 900°C. The dispersed macromolecules induce homogeneously distributed strain fields that keep the aluminium oxide amorphous during the thermal treatment the dispersed macromolecules covalently bind to the matrix, inducing the interface strain. The amorphous state was confirmed by the presence of penta-coordinated aluminium detected by 27Al NMR and a low bandgap measured by UV-vis absorption spectroscopy. Najdeno v: ključnih besedah Ključne besede: amorphous aluminium oxide, polymethylsilane, nanocomposite, electropolymerization, solubility, agglomeration, de-agglomeration, dendrimer, hyperbranched dendritic structure, dynamic light scattering, thermal analysis, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, infrared spectroscopy, UV-Vis spectroscopy Objavljeno: 19.07.2018; Ogledov: 4779; Prenosov: 198
Polno besedilo (5,07 MB) |
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28. PHOTO-EXCITATION ENERGY INFLUENCE ON THE PHOTOCONDUCTIVITY OF ORGANIC SEMICONDUCTORSNadiia Pastukhova, 2018, doktorska disertacija Opis: In this work, we experimentally studied the influence of photoexcitation energy
influence on the charge transport in organic semiconductors. Organic semiconductors
were small molecules like corannulene, perylene and pentacene derivatives, polymers
such as polythiophene and benzothiophene derivatives, and graphene, along with
combinations of these materials in heterojunctions or composites.
The first part of this study is focused on the photoexcitation energy influence on
the transient photoconductivity of non-crystalline curved π-conjugated corannulene
layers. The enhanced photoconductivity, in the energy range where optical absorption
is absent, is deduced from theoretical predictions of corannulene gas-phase excited
state spectra. Theoretical analysis reveals a consistent contribution involving
transitions to Super Atomic Molecular Orbitals (SAMOs), a unique set of diffuse
orbitals typical of curved π-conjugated molecules. More, the photoconductivity of the
curved corannulene was compared to the π-conjugated planar N,N′-1H,1H-
perfluorobutyldicyanoperylene-carboxydi-imide
(PDIF-CN2),
where
the
photoexcitation energy dependence of photocurrent closely follows the optical
absorption spectrum.
We next characterized charge transport in poly(3-hexylthiophene) (P3HT) layers
deposited from solution. Our results indicate that time-of-flight (TOF) mobility
depends on the photoexcitation energy. It is 0.4× 10 −3 cm 2 /Vs at 2.3 eV (530 nm) and
doubles at 4.8 eV (260 nm). TOF mobility was compared to field-effect (FET) mobility
of P3HT field-effect transistors (OFETs). The FET mobility was similar to the 2.3 eV
excitation TOF mobility. In order to improve charge mobility, graphene nanoparticles
were blended within a P3HT solution before the deposition. We found that the mobility
significantly improves upon the addition of graphene nanoparticles of a weight ratio
as low as 0.2 %. FET mobility increases with graphene concentration up to a value of
2.3× 10 −2 cm 2 /Vs at 3.2 %. The results demonstrate that phase segregation starts to
influence charge transport at graphene concentration of 0.8 % and above. Hence, the
graphene cannot form a bridged conduction channel between electrodes, which would
cancel the semiconducting effect of the polymer composite.
An alternative approach to enhance mobility is to optimize the molecular ordering
of organic semiconductors. For that purpose, we studied an innovative nanomesh
device. Free-standing nanomesh devices were used to form nanojunctions of N,N′-
iiDioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) nanowires and crystalline
bis(triisopropylsilylethinyl)pentacene (TIPS-PEN). We characterized the photocurrent
response time of this novel nanomesh scaffold device. The photoresponse time
depends on the photon energy. It is between 4.5 − 5.6 ns at 500 nm excitation
wavelength and between 6.7 − 7.7 ns at 700 nm excitation wavelength. In addition, we
found that thermal annealing reduces charge carrier trapping in crystalline nanowires.
This confirms that the structural defects are crucial to obtaining high photon-to-charge
conversion efficiency and subsequent transport from pn junction in heterostructured
materials.
Structural defects also influence the power conversion efficiency of organic
heterostructured photovoltaics (OPVs). Anticipating that polymers with different
backbone lengths produce different level of structural defects, we examined charge
transport
dependence
on
the
molecular
weight
of
poly[4,8-bis(5-(2-
ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-
ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl]
(PTB7-Th)
from 50 kDa to 300 kDa. We found p-type hopping transport in PTB7-Th,
characterized by 0.1 – 3× 10 −2 cm 2 /Vs mobility, which increases with temperature and
electric field. The polymer molecular weight exhibits a non-trivial influence on charge
transport. FET mobility in the saturation regime increases with molecular weight. A
similar trend is observed in TOF mobility and FET mobility in the linear regime,
except for the 100kDa polymer, which manifests in the highest mobility due to reduced
charge trapping. The lowest trapping at the dielectric interface of OFET is observed at
200 kDa. In addition, the 200 kDa polymer exhibits the lowest activation energy of the
charge transport. Although the 100 kDa polymer indicates the highest mobility, OPVs
using the 200 kDa polymer exhibit the best performance in terms of power conversion
efficiency. Najdeno v: ključnih besedah Povzetek najdenega: ...organic
semiconductors,
optical
absorption
spectroscopy,
time-of-flight
photoconductivity, transient photocurrent spectroscopy, organic thin film transistors,
atomic... Ključne besede: organic
semiconductors, optical
absorption
spectroscopy, time-of-flight
photoconductivity, transient photocurrent spectroscopy, organic thin film transistors, atomic force microscopy, superatomic molecular orbitals, pn heterojunction, organic
nanowires, graphene, composites, charge mobility, charge trapping, temperature
dependence, photodetector, photovoltaic, solar cell, organic electronics Objavljeno: 08.10.2018; Ogledov: 4365; Prenosov: 151
Polno besedilo (4,56 MB) |
29. Photocatalytic properties of metal modified TiO2 by photothermal techniquesMladen Franko, Dorota Korte, Urška Lavrenčič Štangar, Olena Pliekhova, Humberto Cabrera, Zeinab Ebrahimpour, 2018, objavljeni povzetek znanstvenega prispevka na konferenci Najdeno v: ključnih besedah Povzetek najdenega: ...Thermal lens spectrometry, Photothermal beam deflection spectroscopy, Dye remediation, Photothermal technique, Photocatalytic degradation, Reactive... Ključne besede: Thermal lens spectrometry, Photothermal beam deflection spectroscopy, Dye remediation, Photothermal technique, Photocatalytic degradation, Reactive Blue 19, TiO2 modification Objavljeno: 09.11.2018; Ogledov: 2805; Prenosov: 0
Polno besedilo (208,76 KB) |
30. Determination of iron in natural waters using DGT technique coupled to phototermal beam deflection spectroscopyHanna Budasheva, Arne Bratkič, Dorota Korte, Mladen Franko, 2018, objavljeni povzetek znanstvenega prispevka na konferenci Najdeno v: ključnih besedah Ključne besede: Beam deflection spectroscopy, diffusive gradients in thin-films, iron species, photothermal techniques, natural waters. Objavljeno: 09.11.2018; Ogledov: 2841; Prenosov: 0
Polno besedilo (40,53 KB) |