Hyocheol Jung

Excimer emission based on the control of molecular structure and intermolecular interactions

Three triple-core chromophore derivatives based on anthracene and pyrene or chrysene moieties, 1,6-bis-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-pyrene (1,6 DAP-TP), 6,12-bis-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-chrysene (DAC-TP), and 2,7-bis-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-pyrene (2,7 DAP-TP), were designed and synthesized. For 1,6 DAP-TP, anthracene was attached to the 1,6 positions of pyrene. In the case of DAC-TP, two anthracenes were connected to chrysene, located at the center position within the core, whereas in 2,7 DAP-TP anthracene was connected to the 2,7 positions of pyrene. All three materials had highly twisted core structures and bulky m-terphenyl side groups introduced into the core. Excimer emission was observed in the solid film state and can be interpreted as the result of anisotropic intermolecular alignment (orientation effect). The wavelength of excimer formation was controlled through the change of the center position of the triple-core chromophore, and the color coordinate of white light and efficiency could be controlled when the materials were used in an electroluminescence (EL) device. Excimer EL emissions of 1,6 DAP-TP, DAC-TP, and 2,7 DAP-TP were at 591 nm, 556 nm, and 538 nm, respectively, and CIE coordinate values of the devices were (0.37, 0.31), (0.30, 0.37), and (0.32, 0.44), respectively, showing single molecular white emission. 2,7 DAP-TP showed a white OLED efficiency of 6.01 cd A−1 at 10 mA cm−2.

Effect of Continuous Cuff Pressure Regulator in General Anaesthesia with Laryngeal Mask Airway

Postoperative pharyngolaryngeal complications (PPLC) occur during anaesthesia due to increased cuff pressure following the insertion of laryngeal mask airways. The use of a pressure regulator to prevent PPLC was evaluated in a prospective, randomized study. Sixty patients scheduled to receive general anaesthesia were randomly assigned to two equal groups of 30, either with or without the regulator. The ‘just seal’ cuff pressure (JSCP), cuff pressure at 5-min intervals during anaesthesia, incidence of pharyngeal sore throat (PST), dysphagia, dysphonia and other complications were evaluated at 1 and 24 h postoperatively. The combined mean ± SD JSCP of both groups was 20.3 ± 3.2 mmHg. In the group with the regulator, cuff pressure was maintained at a constant level during anaesthesia. This study demonstrated that the regulator is a simple, functional device that can reduce the incidence of PST significantly at 1 h postoperatively, following general anaesthesia.

Hybrid White Organic Light Emitting Diodes Using Dual Core Blue Fluorescent Emitter

White OLED (WOLED) devices were fabricated using blue emitting materials, TP-AA-TP, TP-AA-TPB, and TPB-AA-TPB, and yellow emitting material polyphenylenevinylene derivative (PDY 132). Three devices were fabricated with the following structure: ITO/PEDOT:PSS (50 nm)/PDY-132 (40 nm)/NPB (10 nm)/Blue EML (30 nm)/Alq₃ (20 nm)/LiF (1 nm)/Al (200 nm). PDY-132 was used by spin coating, and then three blue fluorescent materials were used by vapor deposition to form a white light emitting device. The color coordinates of WOLED using TP-AA-TP, TP-AA-TPB and TPB-AA-TPB were (0.291, 0.317), (0.317, 0.371) and (0.345, 0.457), respectively. Device using TP-AA-TP as blue emitting material showed the highest efficiencies at 10 mA/cm², L.E of 5.58 cd/A, P.E of 2.16 lm/W and E.Q.E of 2.96%.

Synthesis and property of diazocine derivatives substituted with imidazole in various positions

ABSTRACT TIACA-I, TIACA-II were synthesized by changing the substitution position of the imidazole group in the diazocine core. TIACA-I, TIACA-II in the film state showed absorption in the range of 354 to 392 nm and exhibited blue photoluminescence (PL) emissions at 448 and 462 nm, respectively. The PL wavelength of TIACA-II is red-shifted by 14 nm than that of TIACA-I due to the electron-donating intensity depending on the position of the imidazole group. The use of TIACA-II in a non-doped OLED device resulted in blue emission with current efficiency of 2.84 cd/A and CIE of (0.15, 0.18).

Synthesis of yellow synergist based on pigment yellow 74 for inkjet applications

ABSTRACT New yellow synergist was synthesized for pigment dispersion in pigment ink. 1,4-Butanesultone was applied to Pigment Yellow 74 (PY74) as a hydrophilic functional group in order to synthesize 4-[{2-[(2-Methoxy-4-nitro-phenyl)-(4-sulfo-butyl)-hydrazono]-1-methylene-3-oxo-butyl}-(2-methoxy-phenyl)-amino]-butane-1-sulfonic acid (PY74ASA-2). Whereas pigment showed extremely low solubility in water and organic solvents such as DMSO, DMF and methanol, the synergist was found to have higher solubility than pigment. This result can be interpreted as reduction of particle aggregation by increasing polarity. This synergist applied to pigment ink is expected to improve dispersion property and storage stability of ink.

Synthesis of new yellow synergists based on pigment yellow 150 for inkjet applications

ABSTRACT Inkjet technology using pigment requires pigment dispersity as well as the stability in solvents. New synergist PY-150ASA2 was synthesized by substituting 1,4-butane sultone in order to give the dispersity and the stability. The original pigments showed very low solubility in water and organic solvents. PY-150ASA2 has better solubility and stability in water compared to the pigment. Through the storage stability test, PY-150ASA2 disperses well in the pigment and has a smaller particle size than that of the solsperse 22000, a commercialized synergist. Synergest is expected to be applied to pigment inks for the improved performance.

Synthesis and Electroluminescence Properties of New Type Multi-Chromophore Emitting Materials for Organic Light-Emitting Diodes

New three emitting compounds, AK-1, AK-2 and AK-3 including diazocine moiety were synthesized through Suzuki-coupling reaction. Physical properties such as optical, electroluminescent properties were investigated. UV-visible spectrum of AK-1, AK-2 and AK-3 in film state showed maximum 392, 393 and 401 nm. PL spectrum of AK-1, AK-2 and AK-3 showed maximum emission wavelength of 472, 473 and 435 nm. Three compounds were used as EML in OLED device: ITO/2-TNATA (60 nm)/NPB (15 nm)/EML (35 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (200 nm). AK-3 OLED device showed C.I.E value of (0.18, 0.26) and luminance efficiency of 0.51 cd/A at 10 mA/cm2. New derivatives including diazocine moiety were introduced as OLED emitting material and the EL efficiency was increased by the proper combination of core and side group.

Synthesis and Electroluminescence Properties of New Dual-Core Derivatives

New blue emitting materials based on dual core concept, TP-AF-TP and TP-HAF-TP were synthesized through boronylation and Suzuki coupling reactions. In the thin film state, TP-AF-TP and TP- HAF-TP exhibited maximum PL values at 445 and 440 nm, respectively. A non-doped OLED device based on TP-AF-TP and TP-HAF-TP showed current efficiency of 3.16 and 2.67 cd/A, respectively. TP-AF-TP exhibited a higher EL efficiency than that of TP-HAF-TP.

New Yellow Synergist for Stable Pigment Dispersion of Inkjet Ink

Minimizing ink droplet and self-dispersed pigment mixture are becoming hot issues for high resolution of inkjet printing. New synergist including sulfonic acid group of PY-74 was suggested and synthesized. Pigment itself did not show water solubility but new synergist, SY-11 exhibited good solubility in water and organic solvents such as DMSO and DMF. When aqueous pigment ink was prepared with SY-11, storage stability of the ink has been remained for 7 days under periodically repeated heating and cooling conditions. Particle size of formulated ink was around 150 nm.

Synthesis and Electroluminescent Properties of New Dibenzo-Diazocine Derivatives

AK-1NA and AK-2NA based on dibenzo-diazocine and anthracene moieties were designed and synthesized. Normalized UV-visible spectra of AK-1NA and AK-2NA in film state showed maximum absorption wavelength of 394 and 393 nm. PL spectra of AK-1NA and AK-2NA showed maximum emission wavelength of 429 and 444 nm. At a current density of 10 mA/cm2, OLED devices of AK-1NA and AK-2NA exhibited luminance efficiency of 2.39 and 1.50 cd/A, power efficiency of 1.01 and 0.81 lm/W. Also, OLED devices of AK-1NA and AK-2NA devices exhibited CIE(x, y ) of (0.16, 0.22) and (0.23, 0.42).