Octadecylamine Langmuir Blodgett Film Research Articles

Two-Dimensional Layered Organic-Inorganic Hybrid Perovskite Thin-Film Fabrication by Langmuir-Blodgett and Intercalation Techniques.

We demonstrate the formation of a well-organized thin film of two-dimensional (2D) layered (C18H37NH3)2PbI4 hybrid perovskite by immersing octadecyl amine (ODA) Langmuir-Blodgett (LB) films in an aqueous solution of PbI2/HI. The immersed films exhibit a sharp absorption band at 486 nm (2.55 eV), which is assigned to the excitonic absorption. The film exhibits a bright green emission under ultraviolet light at room temperature. The photoluminescence spectrum has a distinct peak at 497 nm (2.49 eV) and is a mirror image of the absorption spectrum. X-ray diffraction (XRD) analyses reveal that the film has a bilayer-like structure with a d-spacing of 6.4 nm, which is equal to that of a (C18H37NH3)2PbI4 perovskite single crystal with a quantum well (QW) structure. Only intense peaks of the (0 0 l) (l = 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24) reflections are observed in the out-of-plane XRD pattern, indicating that the c axis is vertically oriented with respect to the substrate surface, and the orientational order is remarkably high. Fourier transform infrared spectroscopy reveals that the ODA molecules are protonated in the PbI2/HI solution. These results suggest that the nitrogen atoms of the ODA molecules in the film are protonated in the PbI2/HI solution, and then, inorganic layers of the PbI6 octahedra are intercalated in the alkyl ammonium film to neutralize the positive charge and form a QW structure. Fluorescence microscopy observation reveals that the 2D layered (C18H37NH3)2PbI4 film has a relatively uniform surface, reflecting the well-organized layered structure of the base material (ODA LB film). Because the intercalation process can be applied to various metal cations and halogen anions, we believe that the proposed technique will aid in the development of highly efficient 2D layered organic-inorganic hybrid perovskite materials.

Adsorption of Congored in Cationic Langmuir- Blodgett Films : Spectroscopic Investigations

The present paper reports the incorporation of an anionic water soluble dye congo red (CR) in the cationic octadecylamine (ODA) Langmuir-Blodgett (LB) films. ATR-FTIR spectroscopy confirms the presence of CR molecules in the adsorbed LB films. The adsorption kinetics of the CR molecules onto ODA LB films have been demonstrated by UV-Vis absorption spectroscopy. Comparison of fitted curve of the reaction kinetics to that of the observed one reveals that the reaction kinetics between CR and ODA LB films is of first order kinetic process.

Structural characterization and photocatalytic activity of ultrathin TiO 2 films fabricated by Langmuir–Blodgett technique with octadecylamine

TiO 2 thin films with nanometer-scale thicknesses were prepared by the hydrolysis of titanium potassium oxalate using octadecylamine (ODA) Langmuir–Blodgett (LB) films as templates. After optimizing conditions in immersion process, the amount of TiO 2 generated in the ODA LB film was found to be precisely controlled by the number of deposited ODA layers. Morphological measurements showed that uniform TiO 2 film with surface roughness of less than 1.3 nm could be prepared from the monolayer LB films through subsequent heat-treatment process, while generation of cracks became less noticeable on the 5-layer film after heat-treatment at lower holding temperature with slow heating rate. In addition, photocatalytic activities of the TiO 2 films were examined from the decomposition of cadmium stearate (CdSt) LB films and stearic acid (SA) cast films for different time intervals of irradiation with UV light. Atomic force microscopy measurements showed that an almost flat surface of the CdSt LB film changes to a moth-eaten appearance as a result of decomposition under UV light irradiation. Furthermore, the post-heat-treatment at higher temperatures resulted in decreased photocatalytic activity of the TiO 2 film for the decomposition of SA cast film.

Formation of hemoglobin (Hb)-octadecylamine (ODA) Langmuir-Blodgett (LB) film by spreading Hb solution directly onto subphase covered with a layer of ODA and its electrochemical property

The formation of hemoglobin (Hb)–octadecylamine (ODA) Langmuir-Blotgett (LB) film by spreading Hb solution directly onto subphase covered with a layer of ODA and its electrochemical properties were studied in this paper. This method ensured better electrode activity because almost no protein was adsorbed onto electrode surface before depositing Hb–ODA monolayer onto electrode surface. The optimum equilibrium time of Hb interacted with ODA layer, the optimum protein amount spread onto subphase's interface and the optimum ionic strength and pH of subphase were obtained from the experimental results. The compressibility analyses of Hb–ODA films showed that the surface pressure of this film from liquid-expanded to liquid-condensed state ranged between 16 and 40 mN/m. Direct electron transfer of Hb immobilized on gold electrode by LB technique was observed by cyclic voltammetry. Results showed that Hb molecules still kept their electrochemical activity. The electrode with Hb–ODA LB film displayed the fastest electron transfer rate when the film transferred under the surface pressure of 35 mN/m.

A hydrogen peroxide biosensor based on Langmuir–Blodgett technique: Direct electron transfer of hemoglobin in octadecylamine layer

The present paper describes the modification of hemoglobin (Hb)–octadecylamine (ODA) Langmuir–Blodgett (LB) film on a gold electrode surface to develop a novel electrochemical biosensor for the detection of hydrogen peroxide. Atomic force microscopy (AFM) image of Hb–ODA LB film indicated Hb molecules existed in ODA layer in a well-ordered and compact form. The immobilized Hb displayed a couple of stable and well-defined redox peaks with an electron transfer rate constant of 4.58 ± 0.95 s −1 and a formal potential of −185 mV (versus Ag/AgCl) in phosphate buffer (1.0 mM, pH 5.0) contain 0.1 M KCl at a scan rate of 200 mV s −1, characteristic of Hb heme Fe(III)/Fe(II) redox couple. The formal potential of Hb heme Fe(III)/Fe(II) redox couple in ODA film shifted linearly between pH 5 and 8 with a slope of −23.8 mV pH −1, suggesting that proton took part in electrochemical reaction. The ODA could accelerate the electron transfer between Hb and the electrode. This modified electrode showed an electrochemical activity to the reduction of hydrogen peroxide (H 2O 2) without the aid of any electron mediator.

Studies on the formation of Langmuir monolayer and Langmuir–Blodgett films of octadecyl amine-bromocresol purple dye complex

Properties of the monolayer of octadecyl amine (ODA) molecules on aqueous solution of bromocresol purple (Bcp) dye have been studied over a wide range of pH by measuring the surface pressure-area isotherms. A strong interaction of ODA molecule was observed with the dye molecule in the pH range of 4–9. Under the present study, the dye molecules were adsorbed on the ODA monolayer at the water surface and subsequently a Langmuir–Blodgett (LB) film of ODA–dye complex was transferred from the air–water interface onto a solid substrate. Alternatively, dye molecules were incorporated into LB film by immersing the predeposited LB film of pure ODA into the dye solution, i.e. by adsorption of dye molecule at the solid–liquid interface. The adsorption behavior of ODA–Bcp dye complexes obtained through these two different routes was characterised with the help of UV–Visible spectroscopy. The nature of the ODA–dye complex deposited from air–water interface using the LB technique was found to be quite different from that of the complex formed by the adsorption of the dye into the pure ODA LB film. The adsorption spectra of the ODA–dye complex obtained from the air–water interface did not change with pH, while those of the ODA–dye complex formed from the solid–liquid interface showed pH dependence.

Adsorption Behavior and Structural Characterization of Azo Dyes on a Langmuir−Blodgett Film of Octadecylamine

The adsorbability of the Langmuir−Blodgett (LB) film of octadecylamine (ODA) has been investigated using α-naphthol orange (NO) and methyl orange (MO) as adsorbates. It was found that the specific adsorptions of these azo dyes occurred on the ODA LB film predominantly by ionic interaction, and also that the adsorption behavior depended on pH according to the ionic states of NO and MO as well as that of the ODA LB film. The structural characteristics of the LB films such as orientation, layer−layer distance, and topography of the film surface have been evaluated by means of FTIR and UV−vis spectroscopies, X-ray diffraction in the low-angle region, and atomic force microscopy (AFM), respectively. The results obtained indicated that the adsorption of dyes induced rearrangements of the layer structure, where the hydrocarbon chains took an interdigitated structure and the dye molecules in the LB film exhibited remarkable distinction in the adsorbing state, i.e., a lie-flat configuration of NO and an edge-on co...

Structural Characterization of an Octadecylamine Langmuir–Blodgett Film Adsorbed with Methyl Orange

The adsorption characteristics of a Langmuir–Blodgett (LB) film of octadecylamine (ODA) transferred from the surface of an alkaline subphase were investigated by employing dye material of methyl orange (MO) as an adsorbate. As a result, specific adsorbability of the ODA LB film was observed, similarly to that of the LB film of long-chain quaternary alkylammonium salt. The structural characterizations of the ODA LB films before and after MO adsorption were also carried out by applying spectroscopic methods. It was found that the MO molecules took the specific molecular arrangements of edge-on orientation on the LB film and that the bilayer in the LB films had an interdigitated structure. Furthermore, the layer–layer distance of the LB film was fairly decreased by the MO adsorption, indicating the formation of another layer structure.

Adsorption Behavior of Methyl Orange on the Monolayer and Langmuir–Blodgett Films of Octadecylamine

Abstract The monolayer properties of octadecylamine (ODA) on both distilled water and aqueous Methyl Orange (MO) solution were studied from the measurements of surface pressure–area (π–A) isotherms. From the π–A isotherms at various pHs, hydroxide ions, and MO anions in the subphase were confirmed to interact competitively with the ODA monolayer. Furthermore, Langmuir–Blodgett (LB) film of ODA was fabricated from the surface of an alkaline subphase, and the adsorption characteristics of the ODA LB film were investigated by using MO as an adsorbate. As a result, the ODA LB film exhibited specific adsorbability for the MO anion, similar to that of the LB film of long-chain quaternary alkylammonium salt, but the adsorption rate of the MO on the ODA LB film was slower than that on the LB film of long-chain quaternary alkylammonium salt. In addition, adsorbability of the ODA LB film showed pH dependence.

Photochemical Generation of Gold Nanoparticles in Langmuir−Blodgett Films

Gold nanoparticles were generated by ultraviolet irradiation of Langmuir−Blodgett (LB) films of octadecylamine (ODA), 4-hexadecylaniline (HDA), and benzyldimethylstearylammonium chloride monohydrate (BDSAC) deposited from aqueous HAuCl4 subphases. In contrast, no gold crystals were observed in irradiated LB films prepared from monolayers of dipalmitoyl-dl-α-phosphatidyl-l-serine (DPPS) and dipalmitoyl-l-α-phosphatidylcholine (DPPC). X-Ray photoelectron spectroscopy, UV−visible absorption spectroscopy, atomic force microscopy, and transmission electron microscopy measurements indicated the marked influence of the surfactants used to prepare the LB matrix on the shape of the gold particles. Particles formed in ODA and BDSAC LB films were grown with well-defined crystal faces, while particles generated in HDA LB films were irregular in shape.