Developing of N-(4-methylpyrimidine-2-yl)methacrylamide Langmuir-Blodgett thin film chemical sensor via quartz crystal microbalance technique.

In the present work, the characterization and gas sensing properties of newly synthesized N-(4-methylpyrimidine-2-yl)methacrylamide (N-MPMA) monomer Langmuir-Blodgett (LB) thin films were investigated. The UV-visible spectroscopy, quartz crystal microbalance (QCM), and atomic force microscopy were utilized to characterize N-MPMA LB thin films. The surface behavior of N-MPMA monolayer was stable and allowed an effective transfer at a surface pressure of 14 mN/m. The mass change/unit area value of the N-MPMA LB thin film deposited quartz crystal surfaces was investigated. The amount of N-MPMA LB thin film deposited on the substrate for bilayer was calculated as 228.72 ng (86.31 ng/mm2 ) and 12.5 Hz frequency shift was observed for each layer of the N-MPMA film. The kinetic responses of N-MPMA LB film against chloroform, dichloromethane, benzene, and toluene were measured via QCM system at room temperature. N-MPMA QCM sensor results displayed that chloroform has the largest frequency shifts compared with the other vapors used in the present work and these results can be illuminating in terms of physical properties of organic vapors.

Preparation of pillar[5]arene-quinoline Langmuir-Blodgett thin films for detection of volatile organic compounds with host-guest principles.

In this study, a novel pillar[5]arene-quinoline (P5-Q) as an organic material is used to fabricate Langmuir-Blodgett (LB) thin films and its organic vapor sensing properties have been investigated. The LB deposition process is characterized by UV-visible spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and quartz crystal microbalance (QCM) techniques. The typical frequency shift per layer is obtained as 31.75 Hz per layer and the deposited mass onto a quartz crystal is calculated to be 539.69 ng per layer (2.03 ng mm-2). The fitted surface plasmon resonance (SPR) data were utilized to calculate the film thickness of this material. The thickness of a single layer is calculated to be 1.26 ± 0.09 nm. QCM and SPR systems are used to investigate gas sensing performance of macrocyclic LB films during exposure to Volatile Organic Compounds (VOCs). The macrocyclic LB thin films are more sensitive to dichloromethane than that of other vapors used in this study. The sensitivity and detection limit performance of the P5-Q QCM sensor to dichloromethane vapor were calculated to be 14.751 Hz ppm-1 and 0.203 ppm, respectively. These results demonstrated that the P5-Q material is promising as an organic vapor sensing device at room temperature. Despite Langmuir-Blodgett being a traditional technique in colloid and interface science, this study presents the first gas sensor application for pillararene LB films. Because of the unique symmetric pillar architecture of P5-Q, self-assembly of pillar[5]arene molecules should afford various characteristic nanometer-scale architectures such as micelles, vesicles, and tubes.

Influence of atomic force microscopy acquisition parameters on thin film roughness analysis.

A reliable procedure for measuring parameters connected to surface roughness is needed to compare the gas sensing properties of various thin films or the effect of different fabrication procedures on the surface roughness and the sensing properties. In this article, we propose to investigate how the acquisition parameters specific to atomic force microscopy investigations such as pixel size, scan area and scan speed influence the roughness parameters, namely root mean square and surface area ratio, commonly used for characterizing the gas sensing properties of porphyrins and other materials.