Jung-Hyuk Im

Photoinduced refractive index change of self-assembled spiroxazaine monolayer based on surface plasmon resonance

Abstract The self-assembly of a photochromic, spiroxazine-containing alkanethiol monolayer on a gold surface is described. Contact angle measurements confirm the presence of a hydrophilic surface in the self-assembled monolayer. Atomic force microscopy (AFM) images and measurements confirm that this monolayer was formed by stepwise chemical assembly. Evidence for self-assembled monolayer-photochromism was gathered from UV–visible spectral evaluation before and after irradiation at 366 nm. Surface plasmon resonance (SPR) revealed that a resonance angle change of 0.13° which corresponded to a refractive index change, Δ n , of 0.0034.

Characterization of electro-optic properties of self-assembled monolayer by attenuated total reflection

The electro-optic (E-O) effect was investigated in a self-assembled monolayer by use of the attenuated total reflection technique. The self-assembled monolayer was composed of a pair of layers, cationic polymer with hemicyanine pendent group and anionic molecule. The surface plasmon resonance spectroscopy enabled the determination of the anisotropic dielectric constants and the thickness of each organic layer. A linear change in the modulation of the reflection curve upon application of a modulating electric field was observed, which is from the E-O response of polar-ordered hemicyanine pendent group.

Preparation and spectroscopic characterization of a self-assembled monolayer of squarylium dye on gold

New squarylium dye-containing alkanethiol self-assembled monolayers (SAMs) on gold have been prepared. An unsymmetrical squarylium (SQ) dye for SAM has been synthesized from squaric acid. SQ dye monolayer was deposited on a gold surface by a stepwise method that includes covalent linkage of SQ dye to a cystamine monolayer-modified gold. The molecular structure of a SAM of SQ dye was investigated using visible absorption and Fourier-transform reflection absorption spectra (RAS).

Surface-enhanced Raman scattering spectroscopy and AFM studies of amphiphilic nitroaniline derivatives

Abstract Surface-enhanced Raman scattering (SERS) Spectroscopy and atomic force microscopy (AFM) were employed to characterize the Langmuir-Blodgett (LB) monolayers of an amphiphilic nitroaniline derivatives, n-docosyl-2-methyl-4-nitroaniline (DCMNA) on both Ag surface and mica. DCMNA formed a stable, organized and homogeneous monolayer at the air-water interface only under the specific conditions. Structural changes at the interface induced by surface pressure, temperature and pH of the subphase, and the mole ratio of mixed molecules have been studied. The stable monolayers of DCMNA were obtained on a neutral subphase maintained lower than 10°C. The compressibility of the monolayer was improved by addition of arachidic acid or spreading the monolayer on an alkaline subphase. Micro-Raman and AFM studies indicated that pure DCMNA on a neutral subphase spontaneously formed a well ordered crystalline phase as well as an organized monolayer even under a lower surface pressure. AFM and lateral force microscopy...

Electric poling in ultra-thin films of side group non-linear optical polymers studied by surface-enhanced Raman scattering

Abstract We have shown that surface-enhanced Raman scattering (SERS) techniques may be successfully applied to the corona poling process of ultra-thin films to explain the poling behaviors of the side group non-linear optical (NLO) polymers. The poling kinetics for a flexible backbone based on poly(methyl methacrylate) (PMMA) was described by the usual bi-exponential function. However, the poling kinetics for a rigid backbone system, poly( p -phenyleneterephthalates) to which the NLO chromophores, N -(4-nitrophenyl)-( l )-prolinol(NPP) were attached through flexible spacers were governed by a single rate process. This observation is explained in terms of a strong coupling between the rigid backbone and its side groups.

Isomerically-Featured Aggregate Images of Phenol-Formaldehyde Monolayers by BAM and SMM

Brewster angle microscopy (BAM) and scanning Maxwell-stress microscopy (SMM) were applied to investigate the characteristic aggregate patterns of reactive phenolic resin monolayers. For the two-dimensional condensation reaction in the monolayer at the air-water interface, amphiphilic phenols of structural isomers, o -, m - and p -hexadecoxyphenol ( o -, m - and p -HP), were synthesized by the reaction of catechol, resorcinol, and hydroquinone, respectively, with 1-iodohexadecane. Monolayers of the HPs were spread on aqueous 1% formaldehyde subphases. The surface pressure-area isotherms revealed characteristic monolayer phases and collapse pressures according to the structural isomers at the air-water interface. The optical images of the HP-formaldehyde monolayers were monitored by BAM. The noticeable image was not observed until the monolayer collapse began. The images similar to dots, entangled threads, and blood vessels were respectively produced from o -, m -, and p - HP-formaldehyde monolayers after monolayer collapse. The HP-formaldehyde monolayers were transferred onto silicon wafers, and the morphologies of LB monolayers were observed by SMM. The SMM images have also supported the characteristic aggregate patterns of isomeric HP-formaldehyde monolayers.

Spectroscopic probe of metal complexation of imidazole in the Langmuir monolayer

Abstract An imidazole ring containing amphiphilic molecule, N-[2-(4-imidazolyl) ethyl] 11-mercap-toundecanamide (IMA) was synthesized and constructed into a Langmuir monolayer at the air-water inte...