Calix[4]arene-triazine conjugate intermediate: optical properties and gas sensing responses against aromatic hydrocarbon
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Calix[4]arene‑triazine conjugate intermediate: optical properties and gas sensing responses against aromatic hydrocarbons in Langmuir–Blodgett films Erkan Halay1,2 · Selahattin Bozkurt1,3 · Rifat Capan4,5 · Matem Erdogan4 · Ridvan Unal3 · Yaser Acikbas6 Received: 4 May 2020 / Accepted: 6 July 2020 © Springer Nature B.V. 2020
Abstract The detection of organic vapors by chemically based sensors was achieved with macromolecules having convenient molecular cavities. Addressed herein, a calix[4] arene derivative 25,27-(4-chloro-2-phenylamino-1,3,5-triazine)-26,28-dihydroxycalix[4]arene (C4AsTr) was synthesized and Langmuir–Blodgett (LB) thin films of this compound modified with heterocyclic units were examined for its optical properties and gas sensing capabilities against trace vapor of aromatic BTX hydrocarbons (benzene, toluene, xylene) through surface plasmon resonance technique. In line with this purpose, the experimental SPR data were fitted using the Winspall software to evaluate optical properties of the C4AsTr film. Such thickness and refractive index values of C4AsTr LB films were determined as 1.19 ± 0.02 nm for the thickness per monolayer, and 1.60 ± 0.04 for the refractive index. Exposed to above-mentioned organic vapors were measured with SPR technique, and the photodetector responses of these optical sensors, ΔI, were recorded as a function of time during kinetic process. In order to quantify real-time SPR data, early time Fick’s diffusion law was handled to extract the diffusion coefficients. There were two different regions observed with two slopes indicating that one belongs to fast surface diffusion and second one slow for bulk diffusion into C4AsTr LB film. All SPR results both theoretical and experimental indicated that C4AsTr optical LB thin-film sensors exhibit high response, a good sensitivity and selectivity for saturated benzene vapor than others. These optical thin-film sensors with aniline substituted triazine heterocycle have been potential candidates for organic vapor sensing applications with simple and low-cost preparation at room temperature. Keywords Sensors · Gas response · π-Conjugated heterocycle · Calixarene · Surface plasmon resonance
* Erkan Halay [email protected] Extended author information available on the last page of the article
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Introduction As a result of increased toxic gas production in various industries, constructing optical sensors with efficient gas response property has become a subject of increasing awareness in scientific community since the last quarter century [1, 2]. In this sense, as sensor candidates, much more attention has been directed toward organic materials and for this purpose, large spectrum of multifunctional organic molecules with tunable optical properties have been developed to monitor various analytes like toxic gases [3–5]. Among these toxic gases, despite their widespread use in the industry, aromatic hydrocarbons are often ignored. As a sub-category of volatile organic compounds (VO
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