Yaser Acikbas

Swelling behavior of the 2-(4-methoxyphenylamino)-2-oxoethyl methacrylate monomer LB thin film exposed to various organic vapors by quartz crystal microbalance technique

Abstract In this work FT-IR, 1H and 13C-NMR spectra are used to analyze the structure of a novel 2-(4-methoxyphenylamino)-2-oxoethyl methacrylate (MPAEMA) materials. MPAEMA LB thin films are characterized by UV-Vis spectroscopy and Quartz Crystal Microbalance (QCM) techniques. The sensing behaviors of the films were investigated with respect to volatile organic compounds (VOCs) at room temperature. The sensing responses of the films against VOCs (dichloromethane, chloroform, benzene and toluene) were measured by the QCM method. It was found that the MPAEMA films exhibited good response, reversibility, stability and faster response and recovery characteristic to VOCs. The changes in resonance frequency associated with mass changes can be attributed to the swelling behavior of monomeric thin films during vapor absorption. This swelling is due to the capturing of organic vapor molecules in the sensor environment. Ficks law for early-time diffusion was adopted to quantify real time QCM data for the swelling processes. It was observed that diffusion coefficients ( ) for swelling obeyed the law and could be correlated with the VOCs used. The response of MPAEMA films to the chosen VOCs has been investigated in conditions of physical properties of the solvents, and the films were obtain to be largely sensitive to dichloromethane vapor compared to other studied vapors.

Organic vapor sensing properties of copolymer Langmuir-Blodgett thin film sensors

ABSTRACT In this study, a novel poly[Styrene (ST)-co-Glycidyl Methacrylate (GMA)] copolymer material is used to fabricate Langmuir-Blodgett (LB) thin films and investigate organic vapor sensing properties. Quartz Crystal Microbalance (QCM) system is used to investigate gas sensing performance of copolymer LB films during exposure to Volatile Organic Compounds (VOCs). The poly[Styrene (ST)-co-Glycidyl Methacrylate (GMA)] LB thin film sensor sensitivities are determined to be between 0.12 and 0.25 Hz ppm−1. Detection limits of the copolymer LB thin film are found to be between 23 and 49 ppm against organic vapors. The copolymer LB thin films are more sensitive to chloroform than other vapors used in this study. The results demonstrated that the poly[Styrene (ST)-co-Glycidyl Methacrylate (GMA)] copolymer material is promising as a organic vapor sensing device at room temperature.

Characterization of N-cyclohexylmethacrylamide LB thin films for room temperature vapor sensor application

ABSTRACT This study reports the synthesis, characterization and gas sensing applications of N-cyclohexylmethacrylamide (NCMA) monomer material using FT-IR, 1H and 13C NMR, UV-visible spectroscopy, Quartz Crystal Microbalance (QCM) and Langmuir-Blodgett (LB) thin film deposition techniques. The thin film deposition conditions of NCMA monomer material, which are prepared by LB film technique, are characterized by UV-visible spectroscopy and QCM system. The sensing behaviors of the LB film with respect to volatile organic compounds (VOCs) at room temperature are investigated. Surface pressure change as a function of surface area of NCMA molecule at the water surface shows a well-organized and stable monolayer at 18 mN m−1 surface pressure value for LB film deposition. Transfer ratio values are found to be ≥ 0.94 for quartz glass and ≥ 0.93 for quartz crystal substrate. The typical frequency shift per layer is obtained 20.10 Hz/layer and the deposited mass onto a quartz crystal is calculated as 824.62 ng/layer. The sensing responses of the LB films against chloroform, dichloromethane, acetone, toluene, benzene and ethanol are measured by QCM system. The sensitivities of the NCMA LB film sensor are determined between 0.085 and 0.029 Hz ppm−1. Sensitivities with detection limits are between 35.29 and 100.33 ppm against organic vapors. These results can be concluded that the monomer LB film sample is found to be significantly more sensitive to chloroform and dichloromethane vapors than others organic vapors used in this work. This material may find potential applications in the development of room temperature organic vapor sensing.

Optical and Vapor Sensing Properties of Calix[4]arene Langmuir-Blodgett Thin Films with Host–Guest Principles

ABSTRACT 25,27-(Dipropylmorpholinoacetamido)-26,28-dihydroxycalix[4]arene was used as a chemical sensor material in this work. The calix[4]arene LB thin films were prepared onto a gold-coated glass and quartz glass substrates to fabricate a thin film chemical sensor element. Atomic Force Microscopy (AFM) and Surface Plasmon Resonance (SPR) techniques were used to characterize all the calix[4]arene LB thin films. The film thickness and the refractive index of thin films can be evaluated with the fitted experimental SPR datas. The refractive index and the thickness per monolayer of LB films were determined as a 1.58 ± 0.04 and 1.27 ± 0.09 nm, respectively. The calix[4]arene LB thin film chemical sensor element was exposed to dichloromethane, chloroform, benzene and toluene vapors. The SPR kinetic measurements displayed that, the photodetector response change, ΔIrf for saturated dichloromethane vapor is much larger than the other vapors with the ΔIrf value of 48 au and the diffusion coefficient value of 5.1 × 10−16 cm2s−1. Swelling process was analyzed by well known Ficks Equations. In this approach diffusion coefficients () for swelling were conformed to the square root of time and were correlated with the volatile organic compounds. Our results showed that calix[4]arene thin film has a highly selective with a large response to dichloromethane vapor.