1. Measuring thermal diffusivity of azoheteroarene thin layers by photothermal beam deflection and photothermal lens methodsAmeneh Mikaeeli, Dorota Korte, Humberto Cabrera, Dariusz Chomicki, Dariusz Dziczek, Oksana Kharchenko, Peng Song, Junyan Liu, Andreas D. Wieck, Michal Pawlak, 2023, original scientific article Keywords: thin films, photothermal spectroscopy, thermal transport, thermal wave, thermal conductivity, thermal diffusivity
Published in RUNG: 21.09.2023; Views: 1814; Downloads: 6
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3. Time series analysis of duty cycle induced randomness in thermal lens systemMohanachandran Nair Sindhu Swapna, 2020, original scientific article Abstract: The present work employs time series analysis, a proven powerful mathematical tool, for investigating the complex molecular dynamics of the thermal lens (TL) system induced by the duty cycle (C) variation. For intensity modulation, TL spectroscopy commonly uses optical choppers. The TL formation involves complex molecular dynamics that vary with the input photothermal energy, which is implemented by varying the duty cycle of the chopper. The molecular dynamics
is studied from the fractal dimension (D), phase portrait, sample entropy (S), and Hurst exponent (H) for different duty cycles. The increasing value of C is found to increase D and S, indicating that the system is becoming complex and less deterministic, as evidenced by the phase portrait analysis. The value of H less than 0.5 conforms the evolution of the TL system to more anti-persistent nature with C. The increasing value of C increases the enthalpy of the system that appears as an increase in full width at half maximum of the refractive index profile. Thus the study establishes that the sample entropy and thermodynamic entropy are directly related.
Keywords: Time series analysis
Fractal analysis
Photothermal lens spectroscopy
Fractal dimension
Hurst exponent
Sample entropy
Published in RUNG: 05.07.2022; Views: 1899; Downloads: 0
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4. Chemical (in)stability of interfaces between different metals and Bi[sub]2Se[sub]3 topological insulatorKatja Ferfolja, Mattia Fanetti, Sandra Gardonio, Matjaž Valant, 2018, published scientific conference contribution abstract Abstract: In recent years a classification of materials based on their topological order gained popularity due to the discovery of materials with special topological character – topological insulators (TI). TI have different band structure than regular insulators or conductors. They are characterized by a band gap in the bulk of the material, but at the surface they possess conductive topological surface states (TSS) that cross the Fermi level. TSS are a consequence of the non-trivial bulk band structure and have properties that differ from ordinary surface states. They are robust toward contamination and deformation of the surface. Additionally, they are also spin polarized, which means that an electron spin is locked to a crystal momentum and, therefore, backscattering during transport is suppressed [1]. Due to their specific properties the TI could be used in fields of spintronics, quantum computing and catalysis [2].
The investigation of the interfaces between metals and the TI has not been given much attention even though its characterization is interesting from fundamental physics and applicative point of view. (In)stability of the contacts with metal electrodes, in a form of a chemical reaction or diffusion, has to be taken into account since it can affect the transport properties of the material or increase the contact resistance. Our research is dedicated to the study of the metal/TI interfaces, in particular to Bi2Se3 with deposited metals that are relevant for electrical contacts (Au, Ag, Pt, Cr, Ti). The thermal and chemical stability of the interfaces are of fundamental importance for understanding the contact behavior, therefore, we focused our work to the characterization of these properties. The metal/TI interfaces are investigated mainly with an electron microscopy (SEM, TEM, STM), EDX microanalysis and XRD. Our previous studies showed that the interface between Bi2Se3, and Ag deposited either chemically or from a vapor phase, results in the formation of new phases already at room temperature [3]. On the contrary, Au deposited on the Bi2Se3 surface shows very limited reactivity and is stable at RT, but diffusion and coalescence of the metal are observed starting from 100 °C [4]. In this contribution, we will present further characterization on the evolution of the Ag/Bi2Se3 and Au/Bi2Se3 interfaces, show preliminary results about recently investigated systems (Pt/Bi2Se3, Ti/Bi2Se3) and compare the thermal and chemical stability of the systems under investigation.
Keywords: thermal lens spectrometry, photothermal beam deflection spectroscopy, dye remediation, photothermal technique, photocatalytic degradation, reactive blue 19, TiO2 modification
Published in RUNG: 20.08.2021; Views: 2905; Downloads: 0
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6. Photothermal lens technique: a comparison between conventional and self-mixing schemesHumberto Cabrera, Imrana Ashraf, Fatima Matroodi, Evelio E. Ramírez-Miquet, Jehan Akbar, Jose Juan Suárez-Vargas, John Fredy Barrera Ramírez, Dorota Korte, Hanna Budasheva, Joseph J. Niemela, 2019, original scientific article Abstract: This work focuses on assessing the analytical capabilities of a new photothermal lens method based on the self-mixing effect to reliably measure metallic traces in water-ethanol solutions. We compare it with the conventional thermal lens scheme, considering the low detection limit and versatility. A theoretical model is presented to describe the laser power variations as a function of the photothermal parameters of the analyzed sample. The experimental results demonstrate that the laser intensity variations, induced by the external optical feedback, are governed by
the photothermal lens effect. Measurements of Fe(II)-1,10-phenanthroline in water–ethanol solutions show a favourable correspondence and agreement with the theory. The low detection limits obtained by the two analytic techniques also agree very well. Nevertheless, our instrument presents advantages regarding compactness and simplicity, suggesting that this platform could be potentially useful as a robust analytical tool for metallic trace detection. In addition, calibration of the method is performed by measuring the so-called self-mixing constant.
Keywords: thermal lens, photothermal spectroscopy, self-mixing effect, trace detection
Published in RUNG: 05.04.2019; Views: 4232; Downloads: 0
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7. Determination of Dissolved Iron Redox Species in Freshwater Sediment using DGT Technique Coupled to BDSHanna Budasheva, Aleksander Kravos, Dorota Korte, Arne Bratkič, Yue Gao, Mladen Franko, 2019, original scientific article Abstract: In this work we have developed a novel method for determination of iron redox species by the use of diffusive gradients in thin-film (DGT) technique coupled to photothermal beam deflection spectroscopy (BDS). The combination of both methods achieved low limit of detection (LOD) of 0.14 μM for Fe (II) ions. The total Fe concentration determined in the Vrtojbica river sediment (Slovenia, Rožna Dolina, 5000 Nova Gorica) was 49.3 μgL–1. The Fe (II) and Fe (III) concentra- tion amounted to 12.8 μgL–1 and 39.9 μgL–1, respectively. Such an approach opens new opportunities for monitoring the content of iron species in natural waters and sediments and provides highly sensitive chemical analysis and an accurate qualitative and quantitative characteristic of the materials under study.
Keywords: Beam deflection spectroscopy, diffusive gradients in thin-film technique, iron redox species, photothermal techniques, sediment
Published in RUNG: 26.02.2019; Views: 4522; Downloads: 117
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8. Optimization of DGT technique for determination of iron species in natural water and sediments by photothermal beam deflection spectroscopyHanna Budasheva, Arne Bratkič, Dorota Korte, Mladen Franko, 2018, published scientific conference contribution abstract Keywords: beam deflection spectroscopy, diffusive gradients in thin-film technique, iron redox species, photothermal techniques, natural water, sediments
Published in RUNG: 23.11.2018; Views: 4524; Downloads: 0
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10. Photocatalytic properties of metal modified TiO2 by photothermal techniquesZeinab Ebrahimpour, Olena Pliekhova, Humberto Cabrera, Dorota Korte, Urška Lavrenčič Štangar, Mladen Franko, 2018, published scientific conference contribution abstract Keywords: Thermal lens spectrometry, Photothermal beam deflection spectroscopy, Dye remediation, Photothermal technique, Photocatalytic degradation, Reactive Blue 19, TiO2 modification
Published in RUNG: 09.11.2018; Views: 4435; Downloads: 0
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