- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
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
-
Semiconducting Langmuir-Blodgett Films of Porphyrin Paddle-Wheel Frameworks for Photoelectric Conversion
摘要： Understanding the photocurrent transportation within porphyrin-containing metal-organic frameworks (PMOFs) will be a critical step for applying these materials in light-harvesting molecular devices in the future. Two copper porphyrin paddle-wheel frameworks (Cu-PPFs) were employed to study the influence of metal ions coordinated into the porphyrin ligands on conductivity and photoelectron transfer capability. To compare the electronic and optical properties of both materials, we prepared an ultra-thin film of each PPF via a Langmuir-Blodgett method. The resulting films exhibited uniform morphology and single-crystalline domains, in addition to photoelectric conversion capabilities. We confirmed both Cu-PPFs have semiconducting properties with an optical bandgap around 2.7 eV. The current density generated by both Cu-PPFs were studied through a mercury drop junction approach. We observed a slightly higher conductivity from the Cu-PPF film consisting of metalloporphyrins than the one without copper doping in the porphyrin centers. In addition, the copper ions coordinated porphyrins were found to be more favorable for facilitating photo-induced electron transfer from the Cu-PPF film to a conductive glass substrate. This work presents a new approach of combining thin film fabrication and electro-heterojunction measurement to study electron transfer within an ultra-thin film.
关键词： Metal-Organic Framework (MOF),2D Material,Langmuir-Blodgett Film,Self-Assembly,Semiconductor,Porphyrin Thin Film,Photoelectric Conversion
更新于2025-09-23 15:21:21