1. Transparent vanadium doped titania-silica films : structural characterization and self-cleaning propertiesAndraž Šuligoj, Nejc Povirk, Ksenija Maver, Andraž Mavrič, Urška Lavrenčič Štangar, Angelja Kjara Surca, 2024, izvirni znanstveni članek Ključne besede: photocatalysis, TiO2-SiO2, vanadium, film, Raman spectroscopy
Objavljeno v RUNG: 09.09.2024; Ogledov: 533; Prenosov: 7
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3. Characterization of atmospheric properties over the Cherenkov Telescope Array at La PalmaMiha Živec, doktorska disertacija Opis: Imaging Atmospheric Cherenkov Telescope (IACT) systems are used in high-energy astrophysics to detect and study gamma-ray sources in the universe. These telescopes measure properties of cosmic gamma rays using Cherenkov radiation emitted by secondary particles produced after interacting with the Earth’s atmosphere. Atmospheric monitoring is crucial for the proper operation of IACT systems. A number of remote sensing and in situ methods are used to understand and correct the effects of the atmosphere on the propagation of Cherenkov radiation from its origin to the telescope. Failure to do so greatly decreases IACT performance, particularly, their energy resolution and threshold. Lidar systems can be used to measure atmospheric optical depth profiles, which are essential for IACT calibration.
The main aim of this thesis is to demonstrate that a prototype lidar for the north-ern site of the Cherenkov Telescope Array Observatory (CTAO), which is a next-generation IACT now under construction, has hardware and software capabilities that would lead to the construction of CTAO Raman lidar. Due to specific require-ments of the CTAO, a Raman lidar, which can provide better atmospheric parameter accuracy, will be used for the first time in an IACT system. In 2021-2022 the BRL was deployed to the future CTAO-North site at the Roque de los Muchachos observatory, La Palma, for testing in its actual operating conditions. During a year and a half long test period, it underwent a number of tests, including manual and remote operation under various environmental conditions. These included hot summers, cold winters, rain, snow, ice, and strong winds, but also some more exotic events, such as desert sand intrusions (Calima) and volcanic eruptions. The latter two are presented in this work as test cases for atmospheric characterization.
Since the main goal of a CTAO lidar is the optical depth measurements, the BRL does not have the full set of features for aerosol characterization. While it can yield the ˚Angstr¨om exponent and lidar ratio, it does not provide depolarization informa-tion, which is one of the key components for aerosol typing. As the atmosphere at La Palma was found to be more complex than initially anticipated, we present the benefits of including depolarization capability by using a conceptually similar Raman lidar system specifically designed for aerosol characterization. We present the results of a campaign focused on the determination of bioaerosol capabilities to act as cloud condensation nuclei and ice-nucleating particles in mixed-phase clouds, where depo-larization information was used to determine the thermodynamic phase of the cloud.
Ključne besede: Cherenkov Telescope Array Observatory, Raman Lidar, atmospheric optical depth, aerosol characterization, Cumbre Vieja, Calima
Objavljeno v RUNG: 23.10.2023; Ogledov: 1728; Prenosov: 49
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4. Order fluctuation induced tunable light emission from carbon nano systemMohanachandran Nair Sindhu Swapna, Sankararaman S, 2019, izvirni znanstveni članek Opis: The paper reports the thermal-induced order fuctuations, in a carbon nanosystem with carbon nanotubes (CNTs) synthesized
by the incomplete combustion of gingelly oil. The sample annealed at diferent temperatures (30–400 °C) is subjected to
various morphological and spectroscopic characterizations. The ultraviolet–visible spectroscopic and thermogravimetric
analyses reveal the CNTs in the sample. The high-resolution transmission electron microscopy (HR-TEM) also confrms the
formation of CNTs in the sample. The Raman spectrum and X-ray difraction pattern show the signature of multi-walled
to single-walled CNT transformation and thus an order fuctuation on annealing. The quantum yield of the sample, measured by integrating sphere method, yields 46.15% at an emission wavelength of 575 nm. When the excitation wavelength
is varied from 350 to 510 nm, the CIE coordinate moves from the white region to the yellowish-green region. The varying
amount of CNTs in the soot, upon annealing is found to vary the luminescence emission from the sample. The study reveals
the thermal-induced oscillatory order in carbon nanosystem with carbon nanotubes (CNTs) leading to tunable excitation/
thermal-dependent luminescence emission and thereby suggesting the possibility of converting the futile soot for fruitful
applications in photonics and nanoelectronics.
Ključne besede: Carbon nanosystem, Single-walled carbon nanotubes, Multi-walled carbon nanotubes, Raman spectroscopy, Thermogravimetric analysis, CIE plot, Quantum yield, gingelly oil
Objavljeno v RUNG: 05.07.2022; Ogledov: 2035; Prenosov: 0
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5. Particulate Exhaust Analysis from Internal Combustion EnginesMohanachandran Nair Sindhu Swapna, 2017, drugi znanstveni članki Opis: Today the world is worried over the particulate emission from various forms of internal combustion engines. The present work is an attempt to understand the constituents of the particulate emission and its possible use. The particulate exhaust matter containing carbonaceous soot produced from the combustion of
fuel containing hydrocarbons shows the presence of significant amount of carbon Nanomaterials. Hydrocarbons are the most widespread precursors among carbon sources employed in the production of carbon nanotubes (CNTs) and carbon
nanoparticles (CNPs). Carbon nanotubes find application in fuel cells providing improved performance. The soot particles collected from the internal combustion diesel engines are cleaned, powdered and analyzed by various techniques. The
CNPs are characterized by Field Emission Scanning Electron Microscopy (FESEM), X-Ray Powder Diffraction (XRD), Energy Dispersive X ray diffraction (EDS), Raman Spectroscopy, Photoluminescence spectroscopy (PL), Power spectrum and CIE
plot. X Ray Diffraction and Raman spectroscopic analysis show the presence of carbon nanotubes in the amorphous materials.
Ključne besede: HydrocarbonsL Carbon nanotubes, Diesel engines, CIE plot, EDX, Raman spectroscopy
Objavljeno v RUNG: 30.06.2022; Ogledov: 2080; Prenosov: 0
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6. Characterization of electrochemical processes in metal-organic batteries by X-ray Raman spectroscopyAva Rajh, Iztok Arčon, Klemen Bučar, Matjaž Žitnik, Marko Petric, Alen Vižintin, Jan Bitenc, Urban Košir, Robert Dominko, Hlynur Gretarsson, Martin Sundermann, Matjaž Kavčič, 2022, izvirni znanstveni članek Opis: X-ray Raman spectroscopy (XRS) is an emerging
spectroscopic technique that utilizes inelastic scattering of hard Xrays
to study X-ray absorption edges of low Z elements in bulk
material. It was used to identify and quantify the amount of
carbonyl bonds in a cathode sample, in order to track the redox
reaction inside metal−organic batteries during the charge/
discharge cycle. XRS was used to record the oxygen K-edge
absorption spectra of organic polymer cathodes from different
multivalent metal−organic batteries. The amount of carbonyl bond
in each sample was determined by modeling the oxygen K-edge
XRS spectra with the linear combination of two reference compounds that mimicked the fully charged and the fully discharged
phases of the battery. To interpret experimental XRS spectra, theoretical calculations of oxygen K-edge absorption spectra based on
density functional theory were performed. Overall, a good agreement between the amount of carbonyl bond present during different
stages of battery cycle, calculated from linear combination of standards, and the amount obtained from electrochemical
characterization based on measured capacity was achieved. The electrochemical mechanism in all studied batteries was confirmed to
be a reduction of double carbonyl bond and the intermediate anion was identified with the help of theoretical calculations. X-ray
Raman spectroscopy of the oxygen K-edge was shown to be a viable characterization technique for accurate tracking of the redox
reaction inside metal−organic batteries.
Ključne besede: X-ray Raman spectroscopy, meta-organic batteries, oxygen K-edge XANES, electrochemical processes
Objavljeno v RUNG: 24.03.2022; Ogledov: 2443; Prenosov: 21
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10. Raman LIDARs and atmospheric calibration along the line-of-sight of the Cherenkov Telescope ArraySamo Stanič, Longlong Wang, Marko Zavrtanik, 2019, objavljeni znanstveni prispevek na konferenci Opis: The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for
gamma-ray astronomy at very-high energies. Employing more than 100 (north and south sites)
Imaging Atmospheric Cherenkov Telescopes in the northern and southern hemispheres, it was
designed to reach unprecedented sensitivity and energy resolution. Understanding and correcting
for systematic biases on the absolute energy scale and instrument response functions will be a cru-
cial issue for the performance of CTA. The Montpellier group and the Spanish/Italian/Slovenian
collaboration are currently building two Raman LIDAR prototypes for the online atmospheric cal-
ibration along the line-of-sight of the CTA. Requirements for such a solution include the ability
to characterize aerosol extinction at two wavelengths to distances up to 30 km with an accuracy
better than 5%, within exposure time scales of about a minute, steering capabilities and close
interaction with the CTA array control and data acquisition system as well as other auxiliary in-
struments. Our Raman LIDARs have design features that make them different from those used
in atmospheric science and are characterized by large collecting mirrors (∼2.5 m 2 ), liquid light-
guides that collect the light at the focal plane and transport it to the readout system, reduced
acquisition time and highly precise Raman spectrometers. The Raman LIDARs will participate in
a cross-calibration and characterization campaign of the atmosphere at the CTA North site at La
Palma, together with other site characterization instruments. After a one-year test period there, an
in-depth evaluation of the solutions adopted by the two projects will lead to a final Raman LIDAR
design proposal for both CTA sites.
Ključne besede: Raman lidar atmospheric calibration Cherenkov Telescope Array
Objavljeno v RUNG: 29.08.2019; Ogledov: 4446; Prenosov: 104
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