11. A dual-wavelength photothermal aerosol absorption monitor : design, calibration and performanceLuka Drinovec, Uroš Jagodič, Luka Pirker, Miha Škarabot, Mario Kurtjak, Kristijan Vidović, Luca Ferrero, Bradley Visser, Jannis Röhrbein, Ernest Weingartner, Daniel M. Kalbermatter, Konstantina Vasilatou, Griša Močnik, 2022, izvirni znanstveni članek Opis: There exists a lack of aerosol absorption measurement techniques with low uncertainties and without artefacts. We have developed the two-wavelength Photothermal Aerosol Absorption Monitor (PTAAM-2λ), which measures the aerosol absorption coefficient at 532 and 1064 nm. Here we describe its design, calibration and mode of operation and evaluate its applicability, limits and uncertainties. The 532 nm channel was calibrated with ∼ 1 µmol mol−1 NO2, whereas the 1064 nm channel was calibrated using measured size distribution spectra of nigrosin particles and a Mie calculation. Since the aerosolized nigrosin used for calibration was dry, we determined the imaginary part of the refractive index of nigrosin from the absorbance measurements on solid thin film samples. The obtained refractive index differed considerably from the one determined using aqueous nigrosin solution. PTAAM-2λ has no scattering artefact and features very low uncertainties: 4 % and 6 % for the absorption coefficient at 532 and 1064 nm, respectively, and 9 % for the absorption Ångström exponent. The artefact-free nature of the measurement method allowed us to investigate the artefacts of filter photometers. Both the Aethalometer AE33 and CLAP suffer from cross-sensitivity to scattering – this scattering artefact is most pronounced for particles smaller than 70 nm. We observed a strong dependence of the filter multiple scattering parameter on the particle size in the 100–500 nm range. The results from the winter ambient campaign in Ljubljana showed similar multiple scattering parameter values for ambient aerosols and laboratory experiments. The spectral dependence of this parameter resulted in AE33 reporting the absorption Ångström exponent for different soot samples with values biased 0.23–0.35 higher than the PTAAM-2λ measurement. Photothermal interferometry is a promising method for reference aerosol absorption measurements. Ključne besede: aerosol absorption, calibration, black carbon Objavljeno v RUNG: 28.06.2022; Ogledov: 1134; Prenosov: 25 Povezava na celotno besedilo Gradivo ima več datotek! Več... |
12. Comparing black-carbon- and aerosol-absorption-measuring instruments – a new system using lab-generated soot coated with controlled amounts of secondary organic matterDaniel M. Kalbermatter, Griša Močnik, Luka Drinovec, Bradley Visser, Jannis Röhrbein, Matthias Oscity, Ernest Weingartner, Antti-Pekka Hyvärinen, Konstantina Vasilatou, 2022, izvirni znanstveni članek Opis: We report on an inter-comparison of black-carbon- and aerosol-absorption-measuring instruments with laboratory-generated soot particles coated with controlled amounts of secondary organic matter (SOM). The aerosol generation setup consisted of a miniCAST 5201 Type BC burner for the generation of soot particles and a new automated oxidation flow reactor based on the micro smog chamber (MSC) for the generation of SOM from the ozonolysis of α-pinene. A series of test aerosols was generated with elemental to total carbon (EC TC) mass fraction ranging from about 90 % down to 10 % and single-scattering albedo (SSA at 637 nm) from almost 0 to about 0.7. A dual-spot Aethalometer AE33, a photoacoustic extinctiometer (PAX, 870 nm), a multi-angle absorption photometer (MAAP), a prototype photoacoustic instrument, and two prototype photo-thermal interferometers (PTAAM-2λ and MSPTI) were exposed to the test aerosols in parallel. Significant deviations in the response of the instruments were observed depending on the amount of secondary organic coating. We believe that the setup and methodology described in this study can easily be standardised and provide a straightforward and reproducible procedure for the inter-comparison and characterisation of both filter-based and in situ black-carbon-measuring (BC-measuring) instruments based on realistic test aerosols. Ključne besede: black carbon, aerosol absorption, secondary organic aerosol, coating Objavljeno v RUNG: 01.02.2022; Ogledov: 1613; Prenosov: 48 Celotno besedilo (752,94 KB) |
13. Structure and population of complex ionic species in FeCl[sub]2 aqueous solution by X-ray absorption spectroscopyUroš Luin, Iztok Arčon, Matjaž Valant, 2022, izvirni znanstveni članek Opis: Technologies for mass production require cheap and abundant materials such as ferrous chloride (FeCl2). The literature survey shows the lack of experimental studies to validate theoretical conclusions related to the population of ionic Fe-species in the aqueous FeCl2 solution. Here, we present an in situ X-ray absorption study of the structure of the ionic species in the FeCl2 aqueous solution at different concentrations (1–4 molL−1) and temperatures (25–80 ◦C). We found that at low temperature and low FeCl2 concentration, the octahedral first coordination sphere around Fe is occupied by one Cl ion at a distance of 2.33 (±0.02) Å and five water molecules at a distance of 2.095 (±0.005) Å. The structure of the ionic complex gradually changes with an increase in temperature and/or concentration. The apical water molecule is substituted by a chlorine ion to yield a neutral Fe[Cl2(H2O)4]0. The observed substitutional mechanism is facilitated by the presence of the intramolecular hydrogen bonds as well as entropic reasons. The transition from the single charged Fe[Cl(H2O)5]+ to the neutral Fe[Cl2(H2O)4]0 causes a significant drop in the solution conductivity, which well correlates with the existing conductivity models. Ključne besede: structure, population, ionic species, aqueous ferrous chloride, in situ X-ray absorption spectroscopy Objavljeno v RUNG: 24.01.2022; Ogledov: 1670; Prenosov: 42 (1 glas) Povezava na celotno besedilo Gradivo ima več datotek! Več... |
14. Carbon and Nitrogen K-Edge NEXAFS Spectra of Indole, 2,3-Dihydro-7-azaindole, and 3-FormylindoleAurora Ponzi, Elisa Bernes, Daniele Toffoli, Giovanna Fronzoni, Carlo Callegari, Alessandra Ciavardini, Michele Di Fraia, Robert Richter, Kevin Charles Prince, Hanan Sa'adeh, Michele Devetta, Davide Faccialà, Caterina Vozzi, Lorenzo Avaldi, Paola Bolognesi, Mattea Castrovilli, Daniele Catone, Marcello Coreno, Oksana Plekan, 2021, izvirni znanstveni članek Ključne besede: Carbon and nitrogen, General description, Hybrid functional, Near-edge X-ray absorption fine structure spectrum, Relevant features, Rydberg character, Theoretical spectra, Time dependent density functional theory Objavljeno v RUNG: 19.01.2022; Ogledov: 1714; Prenosov: 0 Gradivo ima več datotek! Več... |
15. Experimental dataset - A dual-wavelength photothermal aerosol absorption monitor: design, calibration and performanceLuka Drinovec, Uroš Jagodič, Luka Pirker, Miha Škarabot, Mario Kurtjak, Kristijan Vidović, Luca Ferrero, Bradley Visser, Jannis Röhrbein, Ernest Weingartner, Daniel Kalbermatter, Konstantina Vasilatou, Tobias Bühlmann, Celine Pascale, Thomas Müller, Alfred Wiedensohler, Griša Močnik, zaključena znanstvena zbirka raziskovalnih podatkov Ključne besede: photothermal interferometer, aerosol light absorption coefficient Objavljeno v RUNG: 14.01.2022; Ogledov: 1730; Prenosov: 27 Celotno besedilo (531,36 MB) Gradivo ima več datotek! Več... |
16. Contribution of coal combustion to black carbon : coupling tracers with the aethalometer modelC. Blanco-Alegre, Paulo Fialho, A. I. Calvo, A. Castro, E. Coz, F. Oduber, A. S. H. Prevot, Griša Močnik, C. Alves, F. Giardi, G. Pazzi, R. Fraile, 2022, izvirni znanstveni članek Ključne besede: absorption coefficient, coal-mining, equivalent black carbon, meteorological variables, seasonal pattern Objavljeno v RUNG: 03.01.2022; Ogledov: 1517; Prenosov: 0 Gradivo ima več datotek! Več... |
17. Photoexcitation processes in atomsAlojz Kodre, Iztok Arčon, Jana Padežnik Gomilšek, 2021, samostojni znanstveni sestavek ali poglavje v monografski publikaciji Opis: Photoelectric absorption is characterized by a smooth power-law decrease of the
cross section with photon energy. Absorption edges reveal rich structure, which
continues into the high-energy side. The quasiperiodic signal, superposed onto
the smooth basis, due to scattering of the photoelectron on the neighbours of the
target atom provides the basis for the structural (XAFS) analysis of the material.
Irregular tiny resonances and edges that appear over the same general range as
XAFS are recognized as intra-atomic effects: multielectron excitations (MEE)
owing to correlated motion in the electronic cloud. The systematic study of MEE
began on noble gases and metallic vapours, both of which are gases of free
atoms. With some extremely strong MEE, mostly coexcitations of the subvalence
d and f electrons, the structural XAFS analysis may be compromised;
hence, there is a need to independently determine the MEE signal, the atomic
absorption background (AAB) for the analyzed element, and remove it prior to
analysis. In view of the scarcity of elements which can practically be prepared in
a free-atom gas state, several approaches to approximate the AAB have been
developed: analysis of disordered compounds, where the weak and simple
XAFS signal can be modelled and removed, and correlation analysis of the
absorption spectra of several independent samples, where the AAB is extracted
in an iterative procedure. Ključne besede: photoexcitation, XAFS, multielectron excitations, atomic
absorption background Objavljeno v RUNG: 15.12.2021; Ogledov: 1618; Prenosov: 0 Gradivo ima več datotek! Več... |
18. Monitoring of chemical processes at the atomic level by X-ray absorption spectrometry using extremely bright synchrotron radiation sourcesIztok Arčon, vabljeno predavanje na konferenci brez natisa Opis: X-ray absorption spectroscopy (XAS) is a powerful tool for characterisation of local structure and chemical state of selected elements in different new functional materials and biological or environmental samples. The XAS spectroscopy is based on extremely bright synchrotron radiation X-rays sources, which allow precise characterisation of bulk, nanostructured or highly diluted samples. The rapid development of extremely bright synchrotron sources of X-ray and ultraviolet light in recent years has opened new possibilities for research of matter at the atomic or molecular level, indispensable in the development of new functional nanostructured materials with desired properties. The lecture will present the possibilities offered by X-ray absorption spectroscopy with synchrotron light for ex-situ and in-situ or operando characterization of various functional porous and other nanomaterials before, after and during their operation. With the operando micro-XANES and EXAFS methods it is possible to track changes in the valence states and local structures of selected elements in different energy storage materials or in various (photo)catalysts, during chemical reactions under controlled reaction conditions, thus gaining insight into the dynamic functional properties and reaction mechanisms of these materials. New synchrotron light sources also opened the possibility of combining X-ray absorption or emission spectroscopy and microscopy with a resolution of up to a few tens of nanometres, crucial for analysis of environmental and biological samples on sub-cellular level, to understand the mechanisms of uptake, transport, accumulation, and complexation of metal cations on subcellular level in various plant tissues or accumulation in environment, to develop effective remediation approaches. Ključne besede: X-ray absorption spectroscopy, EXAFS, XANES, synchrotron radiation sources, operando Objavljeno v RUNG: 15.12.2021; Ogledov: 1715; Prenosov: 0 Gradivo ima več datotek! Več... |
19. The role of substrate on thermal evolution of Ag/TiO[sub]2 nanogranular thin filmsVincenzo Balzano, Emanuele Cavaliere, Mattia Fanetti, Sandra Gardonio, Luca Gavioli, 2021, izvirni znanstveni članek Ključne besede: nanogranular composite thin film, substrate driven properties, morphology, optical absorption, Ag/TiO2 Objavljeno v RUNG: 03.12.2021; Ogledov: 1734; Prenosov: 134 Povezava na celotno besedilo Gradivo ima več datotek! Več... |
20. Detection of mineral dust concentration in Mediterranean and Central Europe by measuring optical absorption of dust particlesMatic Ivančič, Irena Ježek, Martin Rigler, Asta Gregorič, Balint Alfoldy, Luka Drinovec, JEAN SCIARE, Michael Pikridas, FLORIN UNGA, Andrés Alastuey, Marco Pandolfi, Jesús Yus-Díez, Griša Močnik, 2020, prispevek na konferenci brez natisa Ključne besede: mineral dust, optical absorption, virtual impactor Objavljeno v RUNG: 22.11.2021; Ogledov: 1797; Prenosov: 0 Gradivo ima več datotek! Več... |