A chemical approach to control the refractive index of sol–gel matrices for liquid-crystal dispersion devices

Castellón, Erick; Zayat, Marcos; Lévy, David

doi:10.1007/s10971-015-3940-9

Cited by 3 publications

(2 citation statements)

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“…This transmittance is optimized when the refractive index of the salt solution is close to that of the matrix. In this case, the saturated CaCl 2 solution has a n = 1.45, close to n = 1.50 of the matrix (both at 589 nm) . Above 51% RH, the humidity causes condensation of water drops on the thin‐film surface, increasing light scattering, and reducing the light transmission of the film (Figure c).…”

Section: Discussionmentioning

confidence: 87%

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Novel Reversible Humidity‐Responsive Light Transmission Hybrid Thin‐Film Material Based on a Dispersive Porous Structure with Embedded Hygroscopic and Deliquescent Substances

Castellón

Zayat

Lévy

2017

Adv Funct Materials

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The article describes a new concept of an optical hybrid thin-film material that exhibits reversible humidity-driven light transmittance (scattering) properties. The film consists of a dispersive porous structure, with embedded hygroscopic and deliquescent compounds, that is able to scavenge water molecules from humid air to fill up the pores and become transparent to the incident light. Upon exposure to dry air, water is released from the structure and the material recovers its original light scattering properties. The developed thin films can change their transparency when exposed to air with different relative humidity (RH), adjusting the light throughput. This material can, therefore, be used to design new optical switching systems, having the advantage that they do not require liquid crystal, transparent conductive glass substrates, or complex layer-by-layer architectures for operation. In this work, a thin film was prepared by the sol-gel technique using calcium chloride as deliquescent substance embedded in a hybrid silica-titania matrix. At dry air, the thin films show a highly dispersive state, with a light transmittance T = 0.06, while at 51% RH the film exhibits a transparent state with a transmittance T =0.67 (measured at 633 nm).

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Section: Discussionmentioning

confidence: 87%

“…The material is synthesized by the sol–gel method using silicon and titanium alkoxides as starting substances. This material is obtained after the hydrolysis and polycondensation of the alkoxide precursors, controlling the high reactivity of the titanium tetraisopropoxide toward hydrolysis by its complexation with ethyl acetoacetate …”

Section: Methodsmentioning

confidence: 99%