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Alignment of liquid crystals using Langmuir?Blodgett films of unsymmetrical bent-core liquid crystals
摘要： The properties of the thin films of liquid crystal (LC) molecules can be governed easily by external fields. The anisotropic structure of the LC molecules has a large impact on the electrical and optical properties of the film. The Langmuir monolayer (LM) of LC molecules at the air–water interface is known to exhibit a variety of surface phases which can be transferred onto a solid substrate using the Langmuir?Blodgett (LB) technique. Here, we have studied the LM and LB films of asymmetrically substituted bent-core LC molecules. The morphology of LB film of the molecules is found to be a controlling parameter for aligning bulk LC in the nematic phase. It was found that the LB films of the bent-core molecules possessing defects favour the planar orientation of nematic LC, whereas the LB films with fewer defects show homeotropic alignment. The defect in LB films may introduce splay or bend distortions in the nematic near the alignment layer which can govern the planar alignment of the bulk LC. The uniform layer of LB film facilitates the molecules of nematic to anchor vertically due to a strong van der Waals interaction between the aliphatic chains leading to a homeotropic alignment.
关键词： field emission scanning electron microscope,atomic force microscope,Langmuir?Blodgett film,liquid crystals,Brewster angle microscopy,Langmuir monolayer
更新于2025-11-21 11:01:37
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Surface FTIR Techniques to Analyze the Conformation of Proteins/ Peptides in H2O Environment
摘要： Proteins/peptides, which are involved in various biochemical processes in biological systems, contain infrared (IR) active vibrations. Among all the IR absorption bands of proteins/peptides, the amide I band arises mainly from the stretching vibration of the carbonyls (C=O) in backbone amide bonds and is sensitive to the conformations (such as α–helix, β–sheet, unstructured conformation, and so on) in a protein/peptide. Therefore, the amide I band has been used to monitor the biophysical/biochemical behavior of proteins/peptides in biological samples (e.g., living cells or tissues). However, obtaining reproducible IR spectra of proteins/peptides in H2O solution was challenging by direct transmission measurement using a liquid cell with milli-meter level path length, due to the intensive IR absorption of H2O around 1620 cm-1 which overlaps the amide I band. Thus, lots of the IR spectra of proteins/peptides were accomplished in D2O, which has IR absorption around 1200 cm-1. Since D2O may not be a favorable solvent for biological samples, the position of the amide I band of various conformations was needed as a reference for biological samples. Consequently, various surface FTIR techniques (such as Infrared Reflection-Absorption Spectroscopy or IRRAS, and Attenuated Total Reflection or ATR) have been developed to obtain the IR spectra of proteins/peptides in H2O environment and have been reviewed here.
关键词： Amide I band,Langmuir monolayer,ATR,13C labels,IRRAS,PM-IRRAS
更新于2025-09-09 09:28:46