Special Issue "Optics and Spectroscopy for Fluid Characterization"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: closed (31 January 2018).

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A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Johannes Kiefer
E-Mail Website
Guest Editor
Technische Thermodynamik, Universität Bremen, Badgasteiner Str. 1, 28359 Bremen, Germany
Interests: spectroscopy; combustion; ionic liquid; four-wave mixing; raman; fluorescence; infrared
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Special Issue Information

Dear Colleagues,

All over the world, there is a huge and ever-increasing interest in the development and application of optical and spectroscopic techniques to characterize fluids in engineering and science. Methods in this category have substantially advanced our understanding of fluids (gases, liquids, and multiphase). This is particularly true for the last 50 years, as laser-based techniques became gold standards in the analytical sciences and engineering. A key feature of such light-based methods is that they are usually non-intrusive and hence they do not notably alter the systems under investigation. The list of parameters and characteristics that can be measured by optical and spectroscopic techniques in a fluid is long. It includes macroscopic properties such as temperature, chemical composition, thermophysical quantities, and flow velocity, but also molecular information, e.g., about isomerism and intermolecular interactions can be obtained. The list of techniques is long as well. It includes absorption based methods like FTIR, UV/vis, and fluorescence spectroscopy, scattering based methods like Raman, Rayleigh, PIV, LDA/PDA, static and dynamic light scattering, nonlinear optical methods like CARS, laser-induced gratings, degenerate four-wave-mixing, and many others.

The upcoming Special Issue of Applied Sciences will focus on recent developments in optical and spectroscopic techniques for fluid characterization. It will show the breadth of the field including advances in hardware and instrumentation, methodology, and practical implementation. We would like to invite you to submit or recommend original research papers for the "Optics and Spectroscopy for Fluid Characterization" Special Issue.

Prof. Dr.-Ing. Johannes Kiefer
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Spectroscopy

  • Tomography

  • Holography

  • Imaging

  • Sensing

  • Combustion

  • Hydrogen Bonding

  • Process Analytical Technology

  • Liquid

Published Papers (10 papers)

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Editorial

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Editorial
Optics and Spectroscopy for Fluid Characterization
Appl. Sci. 2018, 8(5), 828; https://doi.org/10.3390/app8050828 - 21 May 2018
Cited by 2 | Viewed by 1177
Abstract
This Editorial provides an introduction to and an overview of the special issue “Optics and Spectroscopy for Fluid Characterization”. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)

Research

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Article
Nature Inspired Plasmonic Structures: Influence of Structural Characteristics on Sensing Capability
Appl. Sci. 2018, 8(5), 668; https://doi.org/10.3390/app8050668 - 26 Apr 2018
Cited by 2 | Viewed by 1854
Abstract
Surface enhanced Raman scattering (SERS) is a powerful analytical technique that allows the enhancement of a Raman signal in a molecule or molecular assemblies placed in the proximity of nanostructured metallic surfaces, due to plasmonic effects. However, laboratory methods to obtain of these [...] Read more.
Surface enhanced Raman scattering (SERS) is a powerful analytical technique that allows the enhancement of a Raman signal in a molecule or molecular assemblies placed in the proximity of nanostructured metallic surfaces, due to plasmonic effects. However, laboratory methods to obtain of these prototypes are time-consuming, expensive and they do not always lead to the desired result. In this work, we analyse structures existing in nature that show, on a nanoscale, characteristic conformations of photonic crystals. We demonstrate that these structures, if covered with gold, change into plasmonic nanostructures and are able to sustain the SERS effect. We study three different structures with this property: opal, a hydrated amorphous form of silica (SiO2·nH2O); diatoms, a kind of unicellular alga; and peacock tail feather. Rhodamine 6G (down to 10−12 M) is used to evaluate their capability to increase the Raman signal. These results allow us to define an alternative way to obtain a high sensitivity in Raman spectroscopy, currently achieved by a long and expensive technique, and to fabricate inexpensive nanoplasmonic structures which could be integrated into optical sensors. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)
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Article
Infrared Spectroscopy as Molecular Probe of the Macroscopic Metal-Liquid Interface
Appl. Sci. 2017, 7(12), 1229; https://doi.org/10.3390/app7121229 - 28 Nov 2017
Cited by 1 | Viewed by 1877
Abstract
Metal-liquid interfaces are of the utmost importance in a number of scientific areas, including electrochemistry and catalysis. However, complicated analytical methods and sample preparation are usually required to study the interfacial phenomena. We propose an infrared spectroscopic approach that enables investigating the molecular [...] Read more.
Metal-liquid interfaces are of the utmost importance in a number of scientific areas, including electrochemistry and catalysis. However, complicated analytical methods and sample preparation are usually required to study the interfacial phenomena. We propose an infrared spectroscopic approach that enables investigating the molecular interactions at the interface, but needing only minimal or no sample preparation. For this purpose, the internal reflection element (IRE) is wetted with a solution as first step. Second, a small plate of the metal of interest is put on top and pressed onto the IRE. The tiny amount of liquid that is remaining between the IRE and the metal is sufficient to produce an IR spectrum with good signal to noise ratio, from which information about molecular interactions, such as hydrogen bonding, can be deduced. Proof-of-concept experiments were carried out with aqueous salt and acid solutions and an aluminum plate. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)
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Article
Distinguishing Different Cancerous Human Cells by Raman Spectroscopy Based on Discriminant Analysis Methods
Appl. Sci. 2017, 7(9), 900; https://doi.org/10.3390/app7090900 - 01 Sep 2017
Cited by 11 | Viewed by 2232
Abstract
An approach to distinguish eight kinds of different human cells by Raman spectroscopy was proposed and demonstrated in this paper. Original spectra of suspension cells in the frequency range of 623~1783 cm−1 were acquired and pre-processed by baseline calibration, and principal component [...] Read more.
An approach to distinguish eight kinds of different human cells by Raman spectroscopy was proposed and demonstrated in this paper. Original spectra of suspension cells in the frequency range of 623~1783 cm−1 were acquired and pre-processed by baseline calibration, and principal component analysis (PCA) was employed to extract the useful spectral information. To develop a robust discrimination model, a linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA) were attempted comparatively in the work. The results showed that the QDA model is better than the LDA model. The optimal QDA model was generated with 12 principal components. The classification rates are 100% in the calibration and prediction set, respectively. From the experimental results, it is concluded that Raman spectroscopy combined with appropriate discriminant analysis methods has significant potential in human cell detection. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)
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Article
Probing Structures of Interfacial 1-Butyl-3-Methylimidazolium Trifluoromethanesulfonate Ionic Liquid on Nano-Aluminum Oxide Surfaces Using High-Pressure Infrared Spectroscopy
Appl. Sci. 2017, 7(8), 855; https://doi.org/10.3390/app7080855 - 18 Aug 2017
Cited by 13 | Viewed by 1877
Abstract
The interactions between 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TFS]) and nano-Al2O3 are studied using high-pressure infrared spectroscopy. The thickness of the [BMIM][TFS] interfacial layer on the aluminum oxide are adjusted by controlling the number of washes with ethanol. In contrast to the results [...] Read more.
The interactions between 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TFS]) and nano-Al2O3 are studied using high-pressure infrared spectroscopy. The thickness of the [BMIM][TFS] interfacial layer on the aluminum oxide are adjusted by controlling the number of washes with ethanol. In contrast to the results obtained under ambient pressure, local structures of both the cations and anions of [BMIM][TFS] are disturbed under high pressures. For example, bands due to C-H stretching motions display remarkable blue-shifts in frequency as the pressure of the [BMIM][TFS]/Al2O3 composites is increased to 0.4 GPa. The bands then undergo mild shifts in frequency upon further compression. The discontinuous jump occurring around 0.4 GPa becomes less obvious when the amount of ionic liquid on the Al2O3 is reduced by washing with ethanol. The nano-Al2O3 with surfaces may weaken the cation/anion interactions in the interfacial area as a result of the formation of pressure-enhanced Al2O3/ionic liquid interactions under high pressures. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)
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Article
Collinear FAST CARS for Chemical Mapping of Gases
Appl. Sci. 2017, 7(7), 705; https://doi.org/10.3390/app7070705 - 08 Jul 2017
Cited by 8 | Viewed by 2284
Abstract
We examine the concentration dependence of the Coherent Anti-Stokes Raman Scattering (CARS) signal obtained for gas mixtures at various conditions using the Femtosecond Adaptive Spectroscopic Technique (FAST). We use the CARS signal of the Q-branch vibrational oscillation of molecular oxygen (1556 cm−1 [...] Read more.
We examine the concentration dependence of the Coherent Anti-Stokes Raman Scattering (CARS) signal obtained for gas mixtures at various conditions using the Femtosecond Adaptive Spectroscopic Technique (FAST). We use the CARS signal of the Q-branch vibrational oscillation of molecular oxygen (1556 cm−1) to confirm the quadratic dependence of the coherent signal on the number of molecules in a test volume. In addition, we demonstrate multi-shot FAST CARS imaging of a gas flow in free space by raster-scanning the area of interest. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)
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Article
Infrared Spectroscopy for Studying Structure and Aging Effects in Rhamnolipid Biosurfactants
Appl. Sci. 2017, 7(5), 533; https://doi.org/10.3390/app7050533 - 22 May 2017
Cited by 8 | Viewed by 2692
Abstract
Biosurfactants are produced by microorganisms and represent amphiphilic compounds with polar and non-polar moieties; hence they can be used to stabilize emulsions, e.g., in the cosmetic and food sectors. Their structure and its changes when exposed to light and elevated temperature are yet [...] Read more.
Biosurfactants are produced by microorganisms and represent amphiphilic compounds with polar and non-polar moieties; hence they can be used to stabilize emulsions, e.g., in the cosmetic and food sectors. Their structure and its changes when exposed to light and elevated temperature are yet to be fully understood. In this study, we demonstrate that attenuated total reflection infrared (ATR-IR) spectroscopy is a useful tool for the analysis of biosurfactants, using rhamnolipids produced by fermentation as an example. A key feature is that the analytical method does not require sample preparation despite the high viscosity of the purified natural product. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)
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Article
In Situ Measurement of Alkali Metals in an MSW Incinerator Using a Spontaneous Emission Spectrum
Appl. Sci. 2017, 7(3), 263; https://doi.org/10.3390/app7030263 - 09 Mar 2017
Cited by 15 | Viewed by 2426
Abstract
This paper presents experimental investigations of the in situ diagnosis of the alkali metals in the municipal solid waste (MSW) flame of an industrial grade incinerator using flame emission spectroscopy. The spectral radiation intensities of the MSW flame were obtained using a spectrometer. [...] Read more.
This paper presents experimental investigations of the in situ diagnosis of the alkali metals in the municipal solid waste (MSW) flame of an industrial grade incinerator using flame emission spectroscopy. The spectral radiation intensities of the MSW flame were obtained using a spectrometer. A linear polynomial fitting method is proposed to uncouple the continuous spectrum and the characteristic line. Based on spectra processing and a non-gray emissivity model, the flame temperature, emissivity, and intensities of the emission of alkali metals were calculated by means of measuring the spectral radiation intensities of the MSW flame. Experimental results indicate that the MSW flame contains alkali metals, including Na, K, and even Rb, and it demonstrates non-gray characteristics in a wavelength range from 500 nm to 900 nm. Peak intensities of the emission of the alkali metals were found to increase when the primary air was high, and the measured temperature varied in the same way as the primary air. The temperature and peak intensities of the lines of emission of the alkali metals may be used to adjust the primary airflow and to manage the feeding of the MSW to control the alkali metals in the MSW flame. It was found that the peak intensity of the K emission line had a linear relationship with the peak intensity of the Na emission line; this correlation may be attributed to their similar physicochemical characteristics in the MSW. The variation trend of the emissivity of the MSW flame and the oxygen content in the flue gas were almost opposite because the increased oxygen content suppressed soot formation and decreased soot emissivity. These results prove that the flame emission spectroscopy technique is feasible for monitoring combustion in the MSW incinerator in situ. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)
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Article
A Geometric Dictionary Learning Based Approach for Fluorescence Spectroscopy Image Fusion
Appl. Sci. 2017, 7(2), 161; https://doi.org/10.3390/app7020161 - 09 Feb 2017
Cited by 27 | Viewed by 2131
Abstract
In recent years, sparse representation approaches have been integrated into multi-focus image fusion methods. The fused images of sparse-representation-based image fusion methods show great performance. Constructing an informative dictionary is a key step for sparsity-based image fusion method. In order to ensure sufficient [...] Read more.
In recent years, sparse representation approaches have been integrated into multi-focus image fusion methods. The fused images of sparse-representation-based image fusion methods show great performance. Constructing an informative dictionary is a key step for sparsity-based image fusion method. In order to ensure sufficient number of useful bases for sparse representation in the process of informative dictionary construction, image patches from all source images are classified into different groups based on geometric similarities. The key information of each image-patch group is extracted by principle component analysis (PCA) to build dictionary. According to the constructed dictionary, image patches are converted to sparse coefficients by simultaneous orthogonal matching pursuit (SOMP) algorithm for representing the source multi-focus images. At last the sparse coefficients are fused by Max-L1 fusion rule and inverted to fused image. Due to the limitation of microscope, the fluorescence image cannot be fully focused. The proposed multi-focus image fusion solution is applied to fluorescence imaging area for generating all-in-focus images. The comparison experimentation results confirm the feasibility and effectiveness of the proposed multi-focus image fusion solution. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)
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Review

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Review
Imaging Flow Velocimetry with Laser Mie Scattering
Appl. Sci. 2017, 7(12), 1298; https://doi.org/10.3390/app7121298 - 13 Dec 2017
Cited by 9 | Viewed by 2143
Abstract
Imaging flow velocity measurements are essential for the investigation of unsteady complex flow phenomena, e.g., in turbomachines, injectors and combustors. The direct optical measurement on fluid molecules is possible with laser Rayleigh scattering and the Doppler effect. However, the small scattering cross-section results [...] Read more.
Imaging flow velocity measurements are essential for the investigation of unsteady complex flow phenomena, e.g., in turbomachines, injectors and combustors. The direct optical measurement on fluid molecules is possible with laser Rayleigh scattering and the Doppler effect. However, the small scattering cross-section results in a low signal to noise ratio, which hinders time-resolved measurements of the flow field. For this reason, the signal to noise ratio is increased by using laser Mie scattering on micrometer-sized particles that follow the flow with negligible slip. Finally, the ongoing development of powerful lasers and fast, sensitive cameras has boosted the performance of several imaging methods for flow velocimetry. The article describes the different flow measurement principles, as well as the fundamental physical measurement limits. Furthermore, the evolution to an imaging technique is outlined for each measurement principle by reviewing recent advances and applications. As a result, the progress, the challenges and the perspectives for high-speed imaging flow velocimetry are considered. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)
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