Ions In Subphase Research Articles

Морфология и электрофизические свойства модифицированных ленгмюровских пленок оксида графена

The work devoted to study of the electrical properties and morphology of Langmuir-Blodgett films of modified graphene oxide (GO). The Langmuir-Blodgett method was used for studying of formation process of Langmuir monolayers formed on the subphase contained dissolved ions of tin chloride salt. The compression isotherms of monolayers formed in the presence of tin ions shifted towards larger occupied areas. Langmuir monolayers of graphene oxide formed under various conditions were transferred on solid substrates and studied by atomic force microscopy and voltammetry. It has been established that the presence of tin ions in the aqueous subphase leads to changes in the morphology of the formed films. Thus, the average roughness and surface area of such films increased from 0.2 nm and 0.04 μm2 to 5.4 nm and 0.46 μm2, respectively. The presence of tin ions dissolved in the aqueous subphase influenced the type of current-voltage characteristics of the films under study. The maximum reverse current increases from 075 nA to -0.3 nA and the resistance increases from 11 GOhm to 700 GOhm. Temperature annealing of the graphene oxide film at 300°C leads to a decrease in the maximum forward current and an increase in the reverse current from 0.0407 nA and -0.071 nA to 0.0065 nA and 0.0616 nA, respectively. For a film formed in the presence of ions in the subphase, annealing does not affect the maximum forward current, and the current of the reverse branch of the current-voltage characteristic increases from -0.1669 nA to 0.0468 nA.

Langmuir-Blodgett deposition selects carboxylate headgroup coordination

Infrared reflection-absorption spectroscopy results on stearic acid Langmuir monolayers containing Mn, Co, and Cd ions show that on the water surface, the ions induce unidentate and bidentate (both chelate and bridged) coordination in the carboxylate headgroup with some trace of undissociated acid. Moreover, with Cd and Mn ions in subphase, the preferred coordination is found to be unidentate, whereas for Co, bidentate chelate is most preferred. After transfer onto amorphous substrate, not all coordinations are found to exist in the same ratio for the deposited metal stearate monolayers. More specifically, after transfer, Mn is found to coordinate with the carboxylate group as bidentate chelate, Cd as unidentate and bidentate bridged (with unidentate as the preferred coordination), and Co as preferably bidentate bridged (although all coordinations are present). Results suggest a specific interaction in each case, as the metal-carboxylate pair at the water surface is transferred to the substrate surface during Langmuir-Blodgett deposition.

Studies on behaviors of dipalmitoylposphatidylcholine and bilirubin in mixed monolayer at the air/water interface

Mixed monolayers of dipalmitoylposphatidylcholine (DPPC) and bilirubin (BR) were prepared on different subphases. The properties of DPPC/BR monolayer, such as collapse pressure ( π coll), limiting area per molecule ( A lim), surface compressibility modulus, free energy (Δ G mix) and excess free energy (Δ G ex), were investigated based on the analysis of the surface pressure–area isotherms on pure water. The results showed that DPPC and BR were miscible and formed non-ideal mixed monolayers at the air/water interface. With the molar fraction of BR ( X BR) increasing, the LE–LC coexistence region of DPPC monolayer was eliminated gradually. The DPPC/BR complex (M D–B) of 1:2 stoichiometry formed as a result of the strong hydrogen bonds between the polar groups of DPPC and BR. The studies of effects of pH values and calcium ions in subphase on the DPPC/BR monolayers showed that the mixed monolayer became expanded on alkali aqueous solution and on 1 mmol/L CaCl 2 aqueous solution. The orientation of DPPC and BR at air/water interface was also discussed.

Fabrication and electrical properties of dendritic macromolecule thin films based on metal complexes

We attempted to fabricate the dendrimer LB films containing a 48 pyridylpropoxy end functional group. The pyridylpropoxy functional group could form a complex structure with metal ions. The samples for electrical properties were fabricated in two ways using metal ions complex by the LB method. In addition, we have investigated the surface activity at the air–water interface as well as the electrical properties for the monolayers LB films of pure G4-48PyP dendrimer and its complex with metal ions (Pt 4+ and Fe 2+ ions). In the π– A isotherms of the dendrimers, the stable condensed films formed at the air–water interface and the effect of metal ions showed a difference in molecular behavior. And we have investigated the electrical properties of the ultra-thin dendrimer LB films by the I– V characteristics of metal/insulator/metal structure. There is a difference between pure G4-48PyP dendrimer LB film and its complex metal ions. This has been generated by the metal ions’ effect. We think that these differences occur by the build up of multi-layers by complex process in the flask and concentration of metal ions in subphase. Therefore, the metal ion around G4-48PyP dendrimer can contribute to the formation of network structure among dendrimers and this result affects the change in electrical properties.

Multi-purpose nonlinear optical microscope. Its principle and applications to polar thin-film observation

Multi-purpose nonlinear optical microscope is an optical microscope which images 2D distribution of the optical second harmonic (SH) waves from a specimen. Image contrast can be obtained either by inhomogeneous distribution of nonlinear optical tensor components or by the interference between SH waves from a specimen and a standard plate. This microscope also functions as a fl uorescence (FL) microscope, and SH and FL images can be obtained from same part of a specimen. Absorption and FL spectra from a specifi c part of a specimen are measured through an optical fi ber, which connects an ocular with a polychromator. These functions are especially useful to investigate the J-aggregate state of polar dye molecules. Several photographs taken by the microscope revealed the structure of merocyanine dye / arachidic acid mixed monolayer and the role of bridge ions in subphase. Experiments started in the 1970s for visualizing inhomogeneous distributions in a specimen using the second harmonic (SH) waves which the specimen produces [1,2]. Recent developments of the spatial resolution and sensitivity of Charge Coupled Device (CCD) camera and image processing techniques enable us to obtain more easily high quality images of various kinds of bulk materials and surfaces. We made good use of development of the technology and constructed a multinpurpose nonlinear optical microscope called SHCM and successfully applied it to observations of ferroelectric domain structures [3n5] and periodically inverted domain structures in quasinphase match devices for frequencynconverter [6]. Recently we have installed a Langmuir trough to the SHGM and performed innsitu observations of monolayer molecules at airnwater interface, in particular, those of the J-aggregate state of polar dye molecules. In this paper, we discuss the principle of the SHGM, describe its structure and show several photographs taken by the SHGM, emphasizing useful application to polar thin fi lm studies.

The Monolayer Behavior of Amphiphilic Polymer and Heterostructure of Polymer LB Film/CdS Clusters

In this paper we report the behavior of an amphiphilic polymer monolayer on pure water and Cd2+ subphase. This polymer was composed of hydrophilic ethylene diamine epichlorohydrin slightly crosslinked microgel and hydrophobic stearic chains, noted as ES-1. The introduction of Cd2+ ions in subphase had a marked effect on the process of the organization of the amphiphilic polymer at the air/water interface due to the association of Cd2+ ions with the hydrophilic network, which could be indicated by the pressure–area isotherms and Brewster Angle Microscopy. Ordered ES-1/Cd2+ LB multilayers were fabricated. After the multilayers reacted with H2S gas, CdS clusters were synthesized within the film, which was characterized by X-ray diffraction and UV–visible spectroscopy.