Light-controlled tuning of the optical properties of nanoporous glass

Varanakkottu, Subramanyan Namboodiri; Engelbart, Hendryk; Joshi, Sumit; Still, M.; Xiao, Wenjia; Hardt, Steffen

doi:10.1364/oe.22.025560

Cited by 5 publications

(3 citation statements)

References 26 publications

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“…It contains regions of filled pores as well as still empty ones, resulting in variations of the refractive index on length scales including the wavelength of visible light. This leads to the scattering of light, a phenomenon well known from the emptying of completely filled Vycor samples via percolating paths [108,109,110] or collective rearrangements of pore condensate induced by phase transitions [111,112,113,114] in porous glass. Its existence in this context shows that there is no sharp interface that separates the filled from the still empty sample, but an extended front separating the two regions.…”

Section: Optical Imagingmentioning

confidence: 99%

Capillary rise dynamics of liquid hydrocarbons in mesoporous silica as explored by gravimetry, optical and neutron imaging: Nano-rheology and determination of pore size distributions from the shape of imbibition fronts

Gruener

Hermes

Schillinger

et al. 2016

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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We present combined gravimetrical, optical, and neutron imaging measurements of the capillarity-driven infiltration of mesoporous silica glass (Vycor) by hydrocarbons. Square-root-of-time Lucas-Washburn invasion kinetics are found for linear alkanes from n-decane (C10) to n-hexacontane (C60) and for squalane, a branched alkane, in porous monoliths with 6.5 nm or 10 nm mean pore diameter, respectively. Humiditydependent experiments allow us to study the influence on the imbibition kinetics of water layers adsorbed on the pore walls. Except for the longest molecule studied, C60, the invasion kinetics can be described by bulk fluidity and bulk capillarity, provided we assume a sticking, pore-wall adsorbed boundary layer, i.e. a monolayer of water covered by a monolayer of flat-laying hydrocarbons. For C60, however, an enhanced imbibition speed compared to the value expected in the bulk is found. This suggests the onset of velocity slippage at the silica walls or a reduced shear viscosity due to the transition towards a behaviour typical of polymer-like flow in confined geometries. Both, light scattering and neutron imaging, indicate a pronounced roughening of the imbibition fronts. Their overall shape and increase in width can be resolved by neutron imaging. The fronts can be described by a superposition of independent wetting fronts moving with pore size-dependent square-root-of-time laws and weighted according to the pore size distributions obtained from nitrogen gas sorption isotherms. This finding indicates that the shape of the imbibition front in a porous medium, such as Vycor glass, with interconnected, elongated pores, is solely determined by independent movements of liquid menisci. These are dictated by the Young-Laplace pressure and hydraulic permeability variations and thus the pore size variation at the invasion front. Our results suggest that pore size distributions can be derived from the broadening characteristics of imbibition fronts.

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Section: Optical Imagingmentioning

confidence: 99%

Capillary rise dynamics of liquid hydrocarbons in mesoporous silica as explored by gravimetry, optical and neutron imaging: Nano-rheology and determination of pore size distributions from the shape of imbibition fronts

Gruener

Hermes

Schillinger

et al. 2016

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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show abstract

“…The latter is crucially reduced in the pressure range at which the condensation occurs in the pores. [ 23,24,34 ] However, all the amplitudes A k are also reduced similarly; in other words, the CARS spectrum profile remains the same despite of transmission of the sample. Therefore, the specific loading of the phase k can be estimated using only the ratio between A k and

λ_{NR}^{(3)}

N_{k} = q \frac{A_{k}}{{normalλ}_{italicNR}^{((), 3)}},

where q is a proportionality factor relating to the current experimental realization.…”

Section: Modeling Of Adsorption Isothermsmentioning

confidence: 97%

CARS‐measurement of adsorption isotherms of carbon dioxide in Vycor glass and CARS‐porosimetry

Arakcheev

Bekin

Morozov

2021

J Raman Spectroscopy

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It has been shown recently that coherent anti‐Stokes Raman scattering (CARS) allows probing the adsorption in optically transparent bulk nanoporous materials. The phases appearing in the pores at different conditions are identified by their resonant spectral contributions characterized by special values of the Raman shift and the linewidth. The present work demonstrates that the spectral amplitudes retrieved from the CARS spectra are the key for numerical description of the specific loadings of the phases. As a result, the adsorption isotherms can be obtained from the spectroscopic data. An essential point here is the presence of the nonresonant background caused by the material of the nanoporous matrix. It is used as the reference to overcome changes in collimated transparency of the sample in the pressure range at which the condensation occurs in the pores. Also, we show that the average pore radius can be estimated by analysis of a single CARS spectrum, allowing for the CARS‐porosimetry.

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“…The strains in its own turn can affect the permeability of nanoporous media [3]. Another example is the change of optical properties of porous glasses during fluids adsorption [4,5]. Thus there is a clear demand to extract the information about fluid distribution from experimental measurements.…”

mentioning

confidence: 99%

Probing Patchy Saturation of Fluids in Nanoporous Media by Ultrasound

Gurevich¹,

Nzikou²,

Gor³

2018

Preprint

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Nanoporous materials provide high surface area per unit mass and are capable of fluids adsorption. While the measurements of overall amount of fluid adsorbed by a nanopororus sample are straightforward, probing the fluid spacial distribution is non-trivial. We consider published data on adsorption and desorption of fluids in nanoporous glasses reported along with the measurements of ultrasonic waves propagation. We analyse these using Biot's theory of dynamic poroelasticity, approximating the patches as spherical shells. Our calculations show that on adsorption the patch diameter is on the order of 10-20 pore diameters, while on desorption the patch size is comparable to the sample size. Our analysis suggests that one can employ ultrasound to probe the uniformity of fluid spatial distribution in nanoporous materials.

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Light-controlled tuning of the optical properties of nanoporous glass

Cited by 5 publications

References 26 publications

Capillary rise dynamics of liquid hydrocarbons in mesoporous silica as explored by gravimetry, optical and neutron imaging: Nano-rheology and determination of pore size distributions from the shape of imbibition fronts

Capillary rise dynamics of liquid hydrocarbons in mesoporous silica as explored by gravimetry, optical and neutron imaging: Nano-rheology and determination of pore size distributions from the shape of imbibition fronts

CARS‐measurement of adsorption isotherms of carbon dioxide in Vycor glass and CARS‐porosimetry

Probing Patchy Saturation of Fluids in Nanoporous Media by Ultrasound

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