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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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Influence of the supramolecular arrangement of iron phthalocyanine thin films on catecholamine oxidation
摘要： The versatility of iron phthalocyanine (FePc) to form distinct supramolecular arrangements in thin films, characterized by their thickness, molecular organization, morphology, and crystallinity, can be used to tune the electrochemical oxidation of catecholamines, becoming a promising material for sensing applications. Here, Langmuir-Schaefer (LS) and electrodeposition (ED) techniques have been used to produce thin films of FePc with different supramolecular arrangements on ITO electrodes. Both types of modified electrode were evaluated for the electrochemical oxidation of L-Dopa, dopamine (DA), norepinephrine (NEp), and epinephrine (Ep) in aqueous solution. The effect of scan rate, potential range, presence of oxygen, and pH were also evaluated, having an influence on the electrochemical oxidation of catecholamines. The FePc/ED modified electrodes showed two distinct peaks in the presence of mixtures of DA/L-Dopa and DA/Ep, while for FePc/LS modified electrodes an overlap of the oxidation waves was observed. This behaviour reveals the influence of the supramolecular arrangement of FePc on catecholamine oxidation. The FePc/LS modified electrodes showed a limit of detection of 0.024 μmol L-1 for DA and 0.168 μmol L-1 for L-Dopa, while FePc/ED showed limits of detection of 0.288 μmol L-1 and 0.564 μmol L-1, respectively. The FePc films showed suitable properties for future application as catecholamine sensors.
关键词： electrodeposition,Langmuir-Schaefer,iron phthalocyanine,catecholamines
更新于2025-09-23 15:23:52
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Haloalkanes and aromatic hydrocarbons sensing using Langmuir–Blodgett thin film of pillar[5]arene-biphenylcarboxylic acid
摘要： Here, a pillar[5]arene derivative including biphenylcarboxylic acid groups was designed for obtaining a macrocycle with an ideal cavity for volatile organic compounds. The pillar[5]arene-biphenylcarboxylic acid (P5-BPCA) based Langmuir-Blodgett (LB) thin films were produced onto 50 nm thick gold-coated glass and 3.5 MHz quartz crystal substrates to form a thin film chemical sensor element. Surface plasmon resonance (SPR) and Quartz crystal microbalance (QCM) techniques were employed to characterize all the P5-BPCA LB thin film layers. The mass of LB film layer loaded onto a quartz crystal and the resonance frequency shifts per layer were determined to be 711.71 ng per layer (2.68 ng mm?2) and 48.24 Hz per layer, respectively. The P5-BPCA LB thin film sensor element was exposed to various haloalkane and aromatic hydrocarbon vapors. The sensitivities of the P5-BPCA LB film sensor were determined between 1.776 and 3.976 Hz ppm-1. Sensitivity with detection limits were obtained between 0.754 and 1.689 ppm against organic vapors. The results showed that P5-BPCA LB thin film was highly selective with a large response to chloromethane vapor.
关键词： Quartz Crystal Microbalance,Pillararene,Langmuir-Blodgett,Volatile Organic Compounds,Swelling,Surface Plasmon Resonance
更新于2025-09-23 15:23:52
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Supramolecular arrangements of an organometallic forming nanostructured films
摘要： Drganometallic materials have become subject of intensive research on distinct technological applications. The Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) techniques have proven to be suitable to address challenges inherent to organic devices, in which the film properties can be tuned at molecular level. Here, we report on the supramolecular arrangement of zinc(OO)-protoporphyrin(OX) dimethyl ester (ZnPPOX-DME) using the Langmuir, LB and LS techniques, leading to nanostructured films. The π-A isotherms showed that π-π stacking interaction among ZnPPOX-DME molecules takes place at the air/water interface, favoring the formation of Langmuir films closely packed. The controlled growth of the LB and LS films was monitored via UV-Vis absorption spectroscopy, with the thickness per monolayer within 1.3 and 1.7 nm. The homogeneous topography found at microscale is no longer preserved at nanoscale, which is found rougher according to AFM data. The FTOR indicated that the ZnPPOX-DME is isotropically arranged on both LB and LS films.
关键词： ZnPPIX-DME,Langmuir film,Langmuir-Blodgett (LB),Langmuir-Schaefer (LS)
更新于2025-09-23 15:22:29
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Humidity sensing properties of metal organic framework-derived hollow ball-like TiO2 coated QCM sensor
摘要： This paper demonstrates three kinds of TiO2 with hollow ball, nanosphere, and nanoflower nanostructures coated quartz crystal microbalance (QCM) humidity sensors, which were synthesized by metal organic framework (MOF)-derived, hydrothermal and solvothermal route, respectively. The compositional and morphological characteristics of three kinds of TiO2 nanostructures were characterized by means of X-ray diffraction (XRD), specific surface area analysis (BET), scanning electron microscopy (SEM) and water contact angle measurement. We found that the surface structure plays a crucial role in the humidity-sensing response properties of QCM sensors. The humidity sensing experiment was performed at room temperature. The MOF-derived hollow ball-like TiO2 coated QCM sensor exhibited excellent humidity sensing characteristics over a wide RH range (0%-97%RH), such as high sensitivity (33.8 Hz/%RH), good repeatability and short dynamic response/recovery times (5 s/2 s). In addition, Langmuir adsorption model was developed to explain the humidity-sensing properties of the TiO2-based QCM sensor. This work proves that MOF-derived hollow-ball TiO2 is a potential candidate nanomaterial for humidity sensor fabrication.
关键词： humidity sensor,Langmuir adsorption model,quartz crystal microbalance,hollow ball-like TiO2
更新于2025-09-23 15:22:29
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Spectroscopic Studies of Magnetron Sputtering Plasma Discharge in Cu/O2/Ar Mixture for Copper Oxide Thin Film Fabrication
摘要： Magnetron sputtering plasma for the deposition of copper oxide thin film has been investigated using optical emission spectroscopy and Langmuir probe. The intensity of the light emission from atoms and radicals in the plasma were measured using optical emission spectroscopy (OES). Then, Langmuir probe was employed to estimate the plasma density, electron temperature and ion flux. In present studies, reactive copper sputtering plasmas were produced at different oxygen flow rate of 0, 4, 8 and 16 sccm. The size of copper target was 3 inches. The dissipation rf power, Ar flow rate and working pressure were fixed at 400 W, 50 sccm and 22.5 mTorr, respectively. Since the substrate bias plays an important role to the thin film formation, the substrate bias voltages of 0, -40, -60 and -100 V were studied. Based on OES results, oxygen emission increased drastically when the oxygen flow rate above 8 sccm. On the other hand, copper and argon emission decreased gradually. In addition, Langmuir probe results showed a different ion flux when substrate bias voltage was applied. Based on these plasma diagnostic results, it has been concluded that the optimized parameter to produce copper oxide thin film are between -40 to -60 V of substrate bias voltage and between 8 to 12 sccm of oxygen flow rate.
关键词： optical emission spectroscopy,Langmuir probe,thin film,magnetron sputtering,Copper oxide
更新于2025-09-23 15:22:29
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Photocatalytic Degradation of Anthracene in Aqueous Dispersion of Metal Oxides Nanoparticles: Effect of Different Parameters
摘要： Contamination with anthracene, as one of polycyclic aromatic hydrocarbons (PAHs), was considered as an important health issue due to its carcinogenic and mutagenic activity. In this paper, we focused on the photocatalytic degradation of anthracene in different media and in presence of various photocatalysts. Zinc oxide nanoparticles (ZnO NPs) and nickel oxide nanoparticles (NiO NPs) were prepared and utilized as efficient photocatalysts to convert anthracene into safer compounds. The as-prepared photocatalysts were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-VIS spectroscopy. The factors affecting the efficiency of photocatalytic degradation, including irradiation time, loading catalyst doses, pH value and H2O2 as an oxidizing agent, were investigated. The optimum photocatalytic degradation of 23 mg/L anthracene in different media was carried out at pH 7.2 with loading catalyst dose of 55.6 mg/L. In case of anthracene emulsion solution, a faster photochemical kinetic was observed in presence of ZnO NPs and more than 90% of photocatalytic degradation percentage was reached in 230 min. However, in case of anthracene aqueous solution and in presence of ZnO NPs/H2O2, a degradation efficiency of 84 % was obtained within 50 min. The byproducts of 4- formyl-benzoic acid ethyl ester (98.23%) and 1,2-Benzenedicarboxylic acid, isopropyl methyl ester (0.85%)) were detected by gas chromatography-mass spectrometry (GC-MS). The kinetic studies were achieved and revealed that the photocatalytic degradation process obeyed a Langmuir–Hinshelwood model and followed a pseudo-first order rate expression.
关键词： Pseudo-first order,Langmuir–Hinshelwood model,Anthracene,Metal oxide nanoparticles,Photocatalysis
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Suppression of electron emission from cathode in photoemission-assisted Ar plasma
摘要： In order to improve the efficiency of the surface flattening process using photoemission-assisted plasma ion source, current-bias voltage characteristic and Ar+ ions/Ar atoms ratio in the plasma was investigated. The glow discharge starting voltage decreases by UV irradiation and a great number of Ar+ ions were irradiated to the substrate. On the other hand in PA Townsend discharge, the number of Ar+ ions reached at the substrate is smaller than that in glow discharge due to space charges near the cathode substrate.
关键词： space charge effect,Langmuir probe,photoemission-assisted plasma
更新于2025-09-23 15:21:21
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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
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Molecular information on the potential of europium complexes for local recognition of a nucleoside-based drug by using nanostructured interfaces assembled as Langmuir- Blodgett films
摘要： Production of nanostructured materials for biological and medical applications may be applied towards the conjugation of adequate substances to boost the stimulus-response of sensors and diagnostic probes. In this sense, Langmuir-Blodgett films constituted of bioinspired and biomimetic materials have attracted attention because of the ease manipulation of the molecular architecture. In this paper, we employed a nucleoside-based drug, which was linked with a sterol hydrophobic moiety (3’,4’-acetonide-uridine-succinate-cholesterol conjugate) to provide it an amphiphilic character. The drug was spread on the air-water interface, alone or mixed with stearic acid, forming Langmuir monolayers, and the complex Eu(tta)3(H2O)2 was incorporated in the drug-containing monolayer. Interactions at the air-water interface between stearic acid, the drug and the europium complex were then investigated with tensiometry, surface potential, infrared spectroscopy, and Brewster angle microscopy. The Langmuir films were transferred to solid supports as Langmuir-Blodgett films, which presented luminescent properties that could be tuned according to the molecular architecture. We believe that these results can serve as a novel approach to characterize and assemble materials organized in the molecular scale for medical applications.
关键词： Eu(tta)3(H2O)2,PM-IRRAS,derivative uridine PNM4,BAM,Langmuir,Langmuir-Blodgett
更新于2025-09-23 15:21:01