Youngjune Hur

Detection of Uranyl Ion Using Polymeric Membrane Containing Calix[6]arene Uranophile

To detect a low concentration of uranyl ions using a surface plasmon resonance (SPR) sensor system, a polymeric sensing membrane containing a water-soluble calix[6]arene was coated on the Au surface of a sensor chip. On the uranyl ion selective molecular-recognition function of the calix[6]arene, the constructed polymeric thin film as a sensing interface showed good sensitivity even in very low concentrations of uranyl ions ranging from 1.0 x 10 -5 M to 1.0 x 10 -12 M (0.1 M Tris-HCl Buffer, pH = 7.0).

Synthesis and Optical Properties of Cycloolefin Copolymers for Plastic Substrates

Cycloolefin copolymers comprise a new class of polymer materials showing properties, of high glass transition temperature, optical clarity, low shrinkage, low moisture absorption and low birefringence. There are several types of cyclic olefin copolymers based on different type of cyclic monomers and polymerization methods. In ethylene/norbornene (E/NB) copolymerization, iPr(Cp)(Flu)ZrCl2 catalyst exhibited more activity than Cp2ZrCl2 and rac-Et(Ind)2ZrCl2 catalysts. By the incorporation of Norbornene in copolymer, the glass transition temperature (Tg) of copolymer became higher. The Tg of copolymer increased up to 190°C. The transmission of copolymers was above 90% over 300 ∼ 900 nm. The RI of ethylene/tetracyclododecene (E/TCD) copolymer was higher than that of E/NB copolymer. The RI of E/NB copolymer could not changed increasing NB contents, however, the RI of E/TCD copolymer increased with increasing of TCD contents. The E/NB copolymer has very low birefringence and that film has very smooth surface.

Uranyl ion sensing by a self-assembled calix[6]arene monolayer

A Self-assembled hydrophilic calix[6]arene monolayer was designed for uranyl ion detection. The uranyl ion recognition-function of the calix[6]arene monolayer was evaluated using surface plasmon resonance (SPR) at various concentrations of uranyl ions (1.0 × 10 −4 ∼ 1.0 × 10 −12 M) in 0.1 M Tris-HCl buffer solution (pH=7.0). Calix[6]arene monolayer showed good sensitivity and selectivity to detect very low concentrations of uranyl ions.

Surface plasmon resonance study on the interaction between the fructose and phenylboronic acid monolayer

Phenylboronic acid derivatives were synthesized and their self-assembled monolayers (SAMs) were formed on a gold surface. The interaction between fructose and phenylboronic acid monolayers was evaluated using surface plasmon resonance (SPR). These phenylboronic acid monolayers showed good sensitivity to fructose at a low concentration range and the resonance angle shifts increased in accordance with the alkyl chain length.

Characteristics of ITO Thin Films for Organic Light Emitting Diode by using a Low-Frequency Magnetron Sputtering Method

In this study, we have tried the growth of indium tin oxide (ITO) thin films by using low-frequency magnetron sputtering method (LFMSM). Characteristics of ITO thin films deposited on polyethersulfone (PES) and polyetyleneterephthalate (PET) substrates are investigated. Experiments were carried out as a function of deposition time. With increasing the deposition time of the ITO thin films on PES substrate, the sheet resistance is decreased. ITO thin films on polymer substrates were amorphous structure.

Photosensitive Paste Formulation and Photolithographic Process for the Fabrication of Barrier Ribs in PDP: Effect of Surface-Treated Fumed Silica

In this work, formulation of photosensitive pastes was investigated to fabricate barrier ribs of PDP by a photolithographic process. Optimum paste compositions could be achieved by the formulation of alkali-developable polymeric binders, functional monomers, a photoinitiator, and a solvent with barrier rib powders of which surface was treated with fumed silica particles. It was applied to the paste and was found that photolithographic patterns of barrier ribs could be obtained with good resolution up to 110 ∼ 120 μm of height and 60 ∼ 80 μm of width after sintering. This could be explained by increased light transmittance efficiency through UV light guide channel formed with an aid of nano-sized fumed silica used for surface treatment of barrier rib powders.

Electroluminescent Properties of Heterocyclic Conjugated Random Copolymers Containing Phenothiazine and Carbazole Moieties

Electroluminescent properties of polymer light-emitting diode (PLED)s fabricated from heterocyclic conjugated random copolymers, poly(PZV-ran-CZV), containing (N-2-ethylhexyl)-3,6-phenothiazinylene vinylene (PZV), (N-2-ethylhexyl)-3,6-carbazolylene vinylene (CZV) and phenylene vinylene (PV) unit as a light emitting layer were investigated. PLEDs made with corresponding alternating copolymers, poly(PZV-PV) and poly(CZV-PV), as a light emitting layer were also studied and exhibited EL maximum at 570 nm and 500 nm, respectively. Single-layered PLEDs made with poly(PZV-ran-CZV) copolymers, however, showed EL maxima shifted to longer wavelength. Double-layered PLED made with poly(PZV-ran-CZV) copolymer as a light emitting layer and Alq3 as an electron transporting layer exhibited enhanced EL emission compared to that of single-layered PLED.

Development of an SH-SAW sensor for detection of DNA immobilization and hybridization

We have developed SH (shear horizontal) surface acoustic wave (SAW) sensors for detection of the immobilization and hybrdization of DNA (deoxyribonucleic acid) on the gold coated delay line of transverse SAW devices. The experiments of DNA immobilization and hybridization were performed with 15-mer oligonucleotides (probe and complementary target DNA). The sensor consists of twin SAW delay line oscillators (sensing channel and reference channel) operating at 100 MHz fabricated on 36° rotated Y-cut X-propagation LiTaO3 piezoelectric single crystals. The relative change in the frequency of the two oscillators was monitored to detect the immobilization of probe DNA with thiol group on the Au coated delay line and the hybridization between target DNA and immobilized probe DNA in a pH 7.4 PBS (phosphate buffered saline) solution. The measurement results showed a good response of the sensor to the mass loading effects of the DNA immobilization and hybridization with the sensitivity up to 1.5 ng/ml/Hz.

Conductivity Measurement of a π-Conjugated Polymer Based on Refractive Index Change

The evaluation of electrical conductivity for π-conjugated polymers is one of the most important areas for several electronic applications. To measure the electrical conductivity (σ) of a π-conjugated polymer thin-film, we attempted to use surface plasmon resonance (SPR). DC conductivity of the polymer thin-film was also measured by the traditional van der Pauw method and compared with the results derived from SPR method. These two conductivity values of the polymer thin-film obtained by different methods were very similar.

Layer Encapsulation of Quantum Dots on Chip on Board Type White LEDs

The chip on board (COB) types LED modules were fabricated by using metal core printed circuit board (mcPCB), aluminium oxide (Al2O3) and aluminium nitride (AlN) as submounts of LED chips. The radiant flux of the LEDs exhibited slight difference in terms of the LED chip bonding process in which eutectic bonding gave higher radiant flux than Ag epoxy bonding in both AlN and Al2O3 substrates. However the LED modules fabricated on AlN ceramic substrate exhibited higher radiant flux than the one on Al2O3 substrate at high current due to more effective heat dissipation in case of AlN substrate. The WLED modules encapsulated with YAG phosphor and red QD by layer-by-layer mode showed both high total luminous flux and high color rendering index.