31. 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: 3333; Downloads: 0
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32. 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: 3661; Downloads: 114
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33. 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: 3736; Downloads: 0
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35. 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: 3622; Downloads: 0
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37. Trace Detection and Photothermal Spectral Characterization by a Tuneable Thermal Lens Spectrometer with White-Light ExcitationHumberto Cabrera, Dorota Korte, Mladen Franko, 2018, original scientific article Abstract: In the thermal lens experimental set-up we replaced the commonly employed pump laser by a halogen lamp, combined with an interference lter, providing a tuneable, nearly monochromatic pump source over the range of wavelengths 430–710 nm. Counter-propagating pump and probe beams are used and a 1 mm path-length sam- ple cell together with the interference lter makes an optical cavity, providing ampli cation of the thermal lens signal, which leads to enhancement of the measurement sensitivity, and enables detection of absorbances on the order of 5×10− 6. Ampli ed thermal lens signal allows us to replace the typical lock-in ampli er and digital os- cilloscope with a silicon photodetector, Arduino board, and a personal computer, offering the possibility for a compact, robust and portable device, useful for in- eld absorption measurements in low concentration or weakly absorbing species. The use of a white light source for optical pumping, an interference lter for wavelength selection and direct diagnostic of the thermal lens signal increase the versatility of the instrument and simpli- es substantially the experimental setup. Determination of Fe(II) concentrations at parts per billion levels was performed by the described white-light thermal lens spectrophotometer and the absorption spectrum for 50μg/ L Fe(II)-1,10-phenanthroline was well reproduced with an average measurement precision of 4%. The obtained limits of detection and quantitation of Fe(II) determination at 510nm are 3μgL− 1 and 11μgL− 1, respectively. The calibration curve was linear in the concentration range of LOQ-500μgL− 1 with reproducibility between 2% and 6%, con rming that this instrument provides good spectrometric capabilities such as high sensitivity, tune- ability and good reproducibility. In addition, the versatility of the instrument was demonstrated by recording the photothermal spectrum of gold nanostructured material and determination of excitation wavelength with most ef cient optical to thermal energy conversion, which differs considerably (cca 100 nm) from the absorption maximum of the investigated sample.
Keywords: thermal lens spectrometry, Fe(II) determination, photothermal technique, multi-wavelength excitation
Published in RUNG: 21.02.2018; Views: 4080; Downloads: 0
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