Optical porosimetry and investigations of the porosity experienced by light interacting with porous media

Svensson, Tomas; Alerstam, Erik; Johansson, Jonas; Andersson‐Engels, Stefan

doi:10.1364/ol.35.001740

Cited by 28 publications

(33 citation statements)

References 20 publications

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“…From this point of view, GASMAS is actually a method which can give the mean pathlength through the embedded gas in the porous media. This has been found to be very useful for porosity diagnosis in porous media, as demonstrated in [22,40,41]; we will come back to this issue later. Although L eq depends upon both the gas concentration and pathlength, it can still be used to characterize the gas concentration in porous media.…”

Section: Gasmas Principlementioning

confidence: 91%

“…,

L_{e q}^{O_{2}} = L_{O_{2}}

, as has been discussed above. The optical porosity of the porous medium, defined as the ratio of the light pathlengths through the pores/gas and the whole medium [22,23], is then retrieved by:

ϕ_{o p} = L_{O_{2}} / L_{p m}

L_{p m} = (L_{m} - L_{O_{2}}) / n_{s} + L_{O_{2}}

…”

Section: Pathlength Resolved Gasmasmentioning

confidence: 99%

“…Such a combination method was later utilized to study the optical porosity of porous ceramics and pharmaceutical tablets, where it was found that the optical porosity is linearly proportional to the physical porosity in the low physical porosity regime, e.g., for pharmaceutical tablets [22]. The combination method between TOFS and GASMAS obviously gives significant information about the porous medium.…”

Section: Pathlength Resolved Gasmasmentioning

confidence: 99%

“…In 2001, a variety of the TDLAS technique, referred to as gas in scattering media absorption spectroscopy (GASMAS) [14], was developed to study the gases (mainly O 2 and H 2 O) embedded in open pores of porous scattering media, e.g., in wood materials [15,16], fruits [17], food packages [18,19], human sinus or mastoid cavities [20,21], ceramics [22], and pharmaceutical tablets [23]. The applications of the GASMAS technique are covered in relevant review papers [24,25].…”

Section: Introductionmentioning

confidence: 99%

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Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy

Mei

Somesfalean

Svanberg

2014

Sensors

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Gas in scattering media absorption spectroscopy (GASMAS) has been extensively studied and applied during recent years in, e.g., food packaging, human sinus monitoring, gas diffusion studies, and pharmaceutical tablet characterization. The focus has been on the evaluation of the gas absorption pathlength in porous media, which a priori is unknown due to heavy light scattering. In this paper, three different approaches are summarized. One possibility is to simultaneously monitor another gas with known concentration (e.g., water vapor), the pathlength of which can then be obtained and used for the target gas (e.g., oxygen) to retrieve its concentration. The second approach is to measure the mean optical pathlength or physical pathlength with other methods, including time-of-flight spectroscopy, frequency-modulated light scattering interferometry and the frequency domain photon migration method. By utilizing these methods, an average concentration can be obtained and the porosities of the material are studied. The last method retrieves the gas concentration without knowing its pathlength by analyzing the gas absorption line shape, which depends upon the concentration of buffer gases due to intermolecular collisions. The pathlength enhancement effect due to multiple scattering enables also the use of porous media as multipass gas cells for trace gas monitoring. All these efforts open up a multitude of different applications for the GASMAS technique.

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Section: Gasmas Principlementioning

confidence: 91%

“…,

L_{e q}^{O_{2}} = L_{O_{2}}

, as has been discussed above. The optical porosity of the porous medium, defined as the ratio of the light pathlengths through the pores/gas and the whole medium [22,23], is then retrieved by:

ϕ_{o p} = L_{O_{2}} / L_{p m}

L_{p m} = (L_{m} - L_{O_{2}}) / n_{s} + L_{O_{2}}

…”

Section: Pathlength Resolved Gasmasmentioning

confidence: 99%

Section: Pathlength Resolved Gasmasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy

Mei

Somesfalean

Svanberg

2014

Sensors

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“…In recent years, a method for detection of trapped gases within scattering porous materials has emerged with applications within a large variety of areas [1]. The technique is usually termed gas in scattering media absorption spectroscopy (GASMAS) and has been employed to study, for example, pharmaceutical tablets [2], optical porosimetry [3], gas exchange in human sinuses as a method to diagnose sinusitis [4] and quality control of food packaging [5]. The interaction of light in the optical domain with trapped gas within nanoporous materials is, however, an area that has not been investigated until recently [6].…”

Section: Introductionmentioning

confidence: 99%

Wall-collision broadening of Gas absorption lines in nanoporous materials

Lewander

Svensson

et al. 2010

Asia Communications and Photonics Conference and Exhibition

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Gas in Scattering Media Absorption Spectroscopy

Svanberg

2000

Encyclopedia of Analytical Chemistry

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Gas in scattering media absorption spectroscopy (GASMAS) is a new variety of tunable diode laser spectroscopy (TDLS). It combines concepts from atmospheric trace‐gas monitoring with those pertinent to biological tissue optics. The former field deals with high‐resolution spectroscopy in nonscattering media, whereas the latter area is characterized by broad absorption structures in strongly scattering media. GASMAS provides novel applications in, e.g. the material science and biophotonics fields. The absorptive imprints of free gases inside pores or cavities in surrounding solid or liquid matter are typically many orders of magnitude narrower than those of the host material, a fact that is critically utilized. The gas signals are detected in the weak, multiply scattered light emerging from the illuminated sample. Wavelength‐modulation and phase‐sensitive detection techniques are employed, typically in connection with single‐mode CW lasers. Any gas with useful absorption at wavelengths where the host material does not absorb strongly can be detected. For biological tissue, containing liquid water and blood, this limits the useful region to the “tissue optical window” –650–1400 nm – where, however, the interesting gases oxygen and water vapor absorb at around 760 and 950 nm, respectively. This limitation does not pertain to other materials, particularly not to those that do not contain liquid water. GASMAS experiments, which relate to basic physics, include studies of nanoporous ceramics, where wall collisions influence the line shape and provide information on pore‐size distribution. A small piece of strongly scattering ceramic can serve as an alignment‐free multipass cell with effective path length hundreds of times longer than the physical dimension. Porosity and gas transport studies in construction materials such as polystyrene foams, wood, ceramics, and paper are examples of applications in the material science field. The technique is further very powerful for studying gas in the human body and products that humans eat, such as packaged foods, fruits, and pharmaceutical preparations. A key aspect of food packaging is to prevent oxygen to influence the food. Frequently, modified atmospheres with nitrogen or carbon dioxide as filling gases are used. Applications include monitoring the performance of packaging machines and measurements of the product on the shelf. Porosity in pharmaceutical tablets is important to determine, as it has bearing on controlled release. Following initial work on healthy volunteers, a clinical trial concerning human sinus cavities has been performed. Gas filling and composition can be used as a diagnostic tool in connection with sinusitis, a very common disorder, also related to the problem with heavy overprescription of antibiotics and associated growing bacterial resistance. Following realistic phantom studies, it was shown that it is possible to detect gas in the lungs and intestines of a newborn baby, which could be of considerable interest for future care of prematurely born children. Gas diffusion and transport can be dynamically studied in response to an abrupt change in gas composition in medicine as well as in material science. The GASMAS technique is fully nonintrusive and nondestructive.

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Optical porosimetry and investigations of the porosity experienced by light interacting with porous media

Cited by 28 publications

References 20 publications

Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy

Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy

Wall-collision broadening of Gas absorption lines in nanoporous materials

Gas in Scattering Media Absorption Spectroscopy

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