Seung-Yeop Yoo

Effect of Complex On Electrical Properties of Dendrimer Langmuir-Blodgett Films Containing 48 Pyridinealdoxime

Dendrimers represent a new class of synthetic macromolecules characterized by a regularly branched treelike structure. Peculiar features of the dendritic geometry are the large number of end groups as well as the shape persistence in higher generations, approaching spherical geometry. And one of the most peculiar characteristics of dendritic macromolecules is their controlled molecular structure and orientation, which means that they have a practical application in achieving a highly organized molecular arrangement. We attempted to fabricate a G4-48PyA dendrimer Langmuir–Blodgett (LB) films containing 48 pyridinealdoxime functional end group that could form a complex structure with metal ions. Also, we investigated the surface activity of dendrimer films at air-water interface. And we have studied the electrical properties of the ultra-thin dendrimer LB films. The electrical properties of the ultra-thin dendrimer LB films were investigated by studying the current–voltage characteristics of metal/dendrimer LB films/metal (MIM) structure. The rectifying behavior of the devices was occurred in applied field. And result in change of electrical properties by the effect of complex with metal ions.

Effects of Complex on Electrical Properties of LB Films Using Dendritic Macromolecules

One of the most peculiar characteristics of dendritic macromolecules is their controlled molecular structure and orientation, which means that they have a practical application in achieving a highly organized molecular arrangement. We attempted to fabricate the G4-48PyP dendrimer Langmuir-Blodgett (LB) films containing 48 pyridinepropanol functional end group that could form a complex structure with metal ions. Also, we have investigated the surface activity at the air-water interface as well as the electrical properties for the monolayers of pure G4-48PyP dendrimer and its complex with Fe 2+ ions. The electrical properties of the ultra-thin dendrimer LB films were investigated by studying the current-voltage characteristics of metal/dendrimer LB films/metal (MIM) structure. The calculated conductivity σ values and barrier height Φ b values of pure G4-48PyP dendrimer and its complexes with Fe 2+ ions are 9.56×10 -16 and 1.46×10 -14 S/cm, 1.18 and 1.10 eV, respectively. As a result, the metal ion around G4-48PyP dendrimer can contribute to the formation of network structure among dendrimers and the change of electrical properties.

The response characteristics of organic gas using QCA coated with polymeric materials

Abstract The new system for identification of organic vapours and analysis method of mechanism between organic vapours and sensitive materials were attempted using the resonant resistance and resonant frequency of Quartz Crystal Analyzer (QCA). The resonant resistance shift means rheological changes in sensitive LB films occurred by the adsorption of organic vapours, while the resonant frequency shift represent the mass of organic vapour loaded in or on the sensitive LB films. Thus we can obtain more accurate response mechanism of organic vapour using the resonant frequency and resonant resistance diagram. The organic vapour response mighit be devided by two type; surface adsorption and penetration into sensitive material. The interface between inner side and surface of sensitive LB films is not clear yet. Organic vapours had different positions in the Frequency-Resistance (F-R) diagram as to the kinds and concentrations. Thus F-R diagram can be applied to the development of one-channel gas sensing system...

Electrical properties of dendritic macromolecule containing azo-groups

We synthesized the G4-48Azo dendrimer functionlized with azobenzene groups, fully reversible photo-isomerization reaction, in their periphery. We investigated monolayer behavior and its characteristics at air-water interface by LB method. And we observed the difference of molecular behavior and measured the surface pressure shift by 365[nm]light irradiation because of the photo-isomerization of the azobenzene group in their periphery. The electrical properties of the G4-48Azo dendrimer were compared with between trans form and cis form using metal/dendrimer LB film/metal(MIM)structure and STM system. And we obtained the difference of values in I-V characteristics using STM originating from the photo-isomerization of the azobenzene.

Fabrication and Electrical Properties of Dendrimer Langmuir-Blodgett Films Based on Metal Complex

We attempted to fabricate dendrimer Langmuir-Blodgett (LB) films containing a 48 pyridylpropoxy functional end group. The pyridylpropoxy functional group could form a complex structure with metal ions; in this study, the samples for the electrical measurement were fabricated using two types of metal complexes with Pt4+ and Fe2+ ions by the LB method. In addition, we investigated the surface activity at the air-water interface as well as the electrical properties of the mono layers of a pure G4-48PyP dendrimer and its complex with metal ions (Pt4+ and Fe2+ ions). In the surface pressure-area (?-A) isotherms of the dendrimers, the s table condensed films formed at the air-water interface and the metal ions effect showed a difference in molecular behavior. We also investigated the electrical properties of ultrathin dendrimer LB films by studying the current-voltage (I?V) characteristics of the metal/insulator/metal (MIM) structure. In conclusion, it is shown that the metal ion around the G4-48PyP dendrimer can contribute to the formation of the network structure of dendrimers, which results from the change in electrical properties.

Preparation and properties of the crosslinked phenol-formaldehyde thin films

We fabricated insulating LB films using p-hexadecoxyphenol (p-Hp), which is amphiphilic phenol and can form polyion complexes with formaldehyde at the air-water interface. Also, the possibility for insulation layers of electronic devices was investigated such as conductivity, dielectric constant and activation energy. The conductivity, dielectric constant and activation energy of p-HP LB films are as follows: pure water > 1% formaldehyde subphase > heat-treatment of 1% formaldehyde subphase.

Structure Analysis of Langmuir and Langmuir-Blodgett Films with Metal Complexes

Abstract We fabricated IMI-O polymer containing imidazole group that forms a complex structure between the monolayer and the metal ions at the air-water interface. Also, the monolayer behavior at the air-water interface and Langmuir-Blodgett (LB) films by complex formation have been investigated by π-A isotherm and the scanning Maxwell-stress microscope.

Electrical Properties of G4-48PyP Dendrimer LB Films

We attempted to fabricate a G4-48PyP dendrimer LB films containing 48 pyridinepropanol functional end group that could form a complex structure with metal ions. Also, we investigated the surface morphology activity of dendrimer films. And we have studied the electrical properties of the ultra-thin dendrimer LB films. The electrical properties of the dendrimer LB films were investigated by studying the current-voltage characteristics of metal/dendrimer LB films/metal (MIM) structure. Rectifying behavior of the devices was occurred in applied field.

The monitoring of J-aggregate behavior of merocyanine dye based on electrochemical QCM

Abstract In this paper, the electrical behavior of a quartz crystal microbalance (QCM) with dye LB film in UV irradiation has been examined by the impedance analysis method. The equivalent electrical parameters, such as resonant frequency ( f 0 ) and resistance ( R 1 ), were investigated. The preparation conditions, using a mixing ratio of fatty acids, subphase effect, and π-A isotherms were investigated to obtain the J-aggregated dye LB film and its optical characteristics were evaluated by UV spectroscopy. The resonant frequency was originated without considering mass adsorption and dependence on the mixing ratio with arachidic acid or resultant absorbance peak at the J-band (optical characteristics). This result could be described by the observation of morphological change before and after UV irradiation, i.e. the resonant frequency shift had a connection with the morphological change. This result strongly suggests that the QCM can be applied to monitor the structural change or optical characteristics of an organic film on the QCM.

Fabrication of Crosslinked Phenolic Polymer LB Films and Its Electrical Properties

Abstract We fabricated the crosslinked films using p-hexadecoxyphenol (p-Hp), which is amphiphilic phenol and can form polyion complexes with formaldehyde at the air-water interface. The behavior of monolayers at the air-water interface and the surface structure of LB films was investigated by Brewster angle microscope (BAM) and scanning Maxwell-stress microscope (SMM), respectively. We have provided evidence for the high insulating performance of phenol-formaldehyde thin films by the LB method.