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    Fabrication of Langmuir-Blodgett thin films of calix[4]arenes and their gas sensing properties: Investigation of upper rim para substituent effect
    (Elsevier Science Sa, 2014) Ozmen, Mustafa; Ozbek, Zikriye; Buyukcelebi, Sumeyra; Bayrakci, Mevlut; Ertul, Seref; Ersoz, Mustafa; Capan, Rifat
    This study reports the characterization and organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of calix[4] arene derivatives that contain different numbers of tert butyl groups on their upper rims. Surface pressure-area isotherms show that very stable monolayers are formed at the air-water interface. The LB films are deposited onto different substrates, which allowed us to characterize the films by contact angle measurements, quartz crystal microbalance (QCM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results indicate that good quality, uniform LB films can be prepared with transfer ratios of over 0.95. Meanwhile, our QCM results show that the deposition of LB film layers depends heavily on the number of p-tert-butyl groups and calix[4]arene with four p-tert-butyl groups yields the highest slope with a mass value of 1145 ng per layer. Furthermore, our AFM and SEM studies reveal a dense surface morphology for all prepared LB films. The kinetic response of calix[4]arenes containing p-tert-butyl groups and without p-tert-butyl groups as an LB film to chloroform, benzene, toluene, and ethanol vapors were investigated as a function of time. After attaching tert-butyl groups onto the calix[4]arene structure, the response of LB film to chloroform vapor increased. LB films of compounds 1-4 yield a response to all vapors and more often select chloroform with a larger, faster, and more reproducible response. We thus conclude that these calix[4]arenes could be applied to research concerning vapor sensing devices operating at room temperature. (C) 2013 Elsevier B.V. All rights reserved.
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    Preparation and gas sensing properties of Langmuir-Blodgett thin films of calix[n]arenes: Investigation of cavity effect
    (Elsevier Science Sa, 2014) Ozmen, Mustafa; Ozbek, Zikriye; Bayrakci, Mevlut; Ertul, Seref; Ersoz, Mustafa; Capan, Rifat
    Characterization and organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of calix[n]arene (n=4, 6, 8) derivatives are reported in this work. Surface pressure-area isotherm graph shows that very stable monolayers are formed at the water surface. The results indicate that good quality, uniform LB films can be prepared with a transfer ratio of over 0.95. Calix[n]arene LB films have been characterized by contact angle measurements, quartz crystal microbalance (QCM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). LB film of calix[8]arene which has the largest cavity yields a gradient with a mass value of 773 ng per layer according to the QCM results. AFM and SEM images showed a dense surface morphology obtained for all samples. QCM system was used for the measurement of sensor response against chloroform, benzene, toluene and ethanol vapors. These LB film samples yield a response to all vapors with a large, fast, and reproducible due to the adsorption of vapors into the LB film structures. Among them, calix[8]arene LB film has higher sensitivity toward the organic vapors because of a large cavity size. This study can be concluded that the cavity size of calix[n]arene molecule could have an important role in the research area of room temperature vapor sensing devices. (C) 2014 Elsevier B.V. All rights reserved.
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    Preparation of Langmuir-Blodgett thin films of calix[6]arenes and p-tert butyl group effect on their gas sensing properties
    (Elsevier Science Bv, 2015) Ozmen, Mustafa; Ozbek, Zikriye; Bayrakci, Mevlut; Ertul, Seref; Ersoz, Mustafa; Capan, Rifat
    Organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of p-tert-butyl calix[6]arene and calix[6]arene, and their certain characterization are reported in this work. LB films of these calixarenes have been characterized by contact angle measurement, quartz crystal microbalance (QCM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). QCM system was used for the measurement of sensor response against chloroform, benzene, toluene and ethanol vapors. Forming of stable monolayers was observed at the water surface using surface pressure-area isotherm graph. The results indicate that good quality, uniform LB films can be prepared with a transfer ratio of over 0.95. Due to the adsorption of vapors into the LB film structures; they yield a response to all vapors as of large, fast, and reproducible. (C) 2015 Elsevier B.V. All rights reserved.