• Journal of Powder Materials
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• v.22 no.6
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• pp.385-390
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• 2015

We report a synthesis of non-toxic InP nanocrystals using non-pyrolytic precursors instead of pyrolytic and unstable tris(trimethylsilyl)phosphine, a popular precursor for synthesis of InP nanocrystals. In this study, InP nanocrystals are successfully synthesized using hexaethyl phosphorous triamide (HPT) and the synthesized InP nanocrystals showed a broad and weak photoluminescence (PL) spectrum. As synthesized InP nanocrystals are subjected to further surface modification process to enhance their stability and photoluminescence. Surface modification of InP nanocrystals is done at $230^{\circ}C$ using 1-dodecanethiol, zinc acetate and fatty acid as sources of ZnS shell. After surface modification, the synthesized InP/ZnS nanocrystals show intense PL spectra centered at the emission wavelength 612 nm through 633 nm. The synthesized InP/ZnS core/shell structure is confirmed with X-ray diffraction (XRD) and Inductively Coupled Plasma - Atomic Emission Spectrometer (ICP-AES). After surface modification, InP/ZnS nanocrystals having narrow particle size distribution are observed by Field Emission Transmission Electron Microscope (FE-TEM). In contrast to uncapped InP nanocrystals, InP/ZnS nanocrystals treated with a newly developed surface modified procedure show highly enhanced PL spectra with quantum yield of 47%.

• Journal of Powder Materials
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• v.21 no.3
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• pp.179-184
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• 2014

In this study, we prepare polymer solar cells incorporating organic ligand-modified Ag nanoparticles (O-AgNPs) highly dispersed in the P3HT:PCBM layer. Ag nanoparticles decorated with water-dispersible ligands (WAgNPs) were also utilized as a control sample. The existence of the ligands on the Ag surface was confirmed by FT-IR spectra. Metal nanoparticles with different surface chemistries exhibited different dispersion tendencies. O-AgNPs were highly dispersed even at high concentrations, whereas W-AgNPs exhibited significant aggregation in the polymer layer. Both dispersion and blending concentration of the Ag nanoparticles in P3HT:PCBM matrix had critical effects on the device performance as well as light absorption. The significant changes in short-circuit current density ($J_{SC}$) of the solar cells seemed to be related to the change in the polymer morphology according to the concentration of AgNPs introduced. These findings suggested the importance of uniform dispersion of plasmonic metal nanoparticles and their blending concentration conditions in order to boost the solar cell performance.

• Journal of Pharmaceutical Investigation
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• v.31 no.4
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• pp.233-239
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• 2001

Local drug delivery by using biocompatible polymers has been developed in the treatment of periodontitis for many years. In the field of dental therapy, doxycycline is usually a first choice because of its broad-spectrum antibiotic activity. The strip releases antibiotics for a week, and the polymer should be degradable after a week. In this study, we prepared and evaluated the chitosan strips and nanoparticle strips containing doxycycline hydrochloride, and studied their antiacterial activity, dissoultion, and degrability in vitro. The weight of cast strip containing a 5 mg of doxycycline hydrochloride and a 45 mg of chitosan polymer was $57.67{\pm}0.17\;mg$. The release rate of doxycycline hydrochloride from the strip was measured by HPLC. The drug released from chitosan strip and nanoparticle strip was shown to be $50\;{\mu}g/mL$ in first 24 hours. In antibacterial test showed growth inhibitory activity after 24 hrs anaerobic incubation. In vitro degradability showed demolished weight of $93.74{\pm}0.08%$ chitosan strip, $82.48{\pm}1.29%$ chitosan nanoparticle strip, $2.47{\pm}1.99%$ polycarprolactione strip (control). These results showed that, with this doxycycline hydrochloride strip, it is feasible to obtain a sustained release of the drug within the periodontal pocket for seven days which may be improve for local drug delivery system for treatment of periodontal disease.

• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.17-23
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• 2007

For the purpose of antibacterial and photocatalystic deodorization functions, the papermaking inorganic fillers and pigments were surface-modified with Ag nano-colloidal solution and $TiO_2$ by using the hybridization technique. The functional specialty sheets and coating papers were produced with the surface-modified fillers and pigments, and evaluated by halo test and inhibition growth test in their antibacterial and photocatalystic characteristics. For the application of specially produced antibacterial handsheet to the wallpaper usages, the photocatalyst efficiency test of benzene in volatile organic compound dissolution experiment of antibacterial and deodorization function wallpaper showed that the efficiency was 45~50% for 80 min of reaction time and 90% of attained resolution was reached at approximately 30 min of response time.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.24-29
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• 2004

Nanocomposite of Te doped $SiO_2$ films was prepared for the new functional materials like non-linear optic materials, selective absorption and transmission films. The effects of particle size and morphology with different hydrolysis conditions on the properties were examined with TGA/DTA. XRD. UV-spectrometer, SPM, SEM and EDS. It was found that Te/$SiO_2$ films showed high absorption peak at 550nm visible region by plasma resonance of Te fine particles. The Rm surface roughness of the films was about 2.5 nm and the size of Te particles was 5~10nm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.47-53
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• 2015

In this paper, a novel fluid controlled phase tunable line using inkjet printed microfluidic composite right/left-handed(CRLH) transmission line(TL) is proposed. A CRLH-TL prototype has been inkjet-printed on a paper substrate using silver nano particle ink. In addition, a laser-etched microfluidic channel in poly methyl methacrylate(PMMA) has been integrated with the CRLH TL using inkjet-printed SU-8 as a bonding material. The proposed TL provides excellent phase-tuning capability that is dependent on the different fluidic materials used. As the fluid is changed, the proposed TL can have negative-phase, zero-phase, and positive-phase characteristics at 900 MHz and reflection coefficient is maintained to below -10 dB. The performance of the proposed TL is successfully validated using simulation and measurement results.

• Korean Journal of Materials Research
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• v.14 no.4
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• pp.270-275
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• 2004

Due to the luminescence by$ Er ^{ 3+}$ activator, Er-doped $LaPO_4$ powders can be applied for optical amplification materials. In this study, $LaPO_4$:Er nanoparticles were synthesized in solution system using a high-boiling coordinating solvent and their properties were investigated through various spectroscopic techniques. The nanoparticles were to take a single phase of monazite structure by a X-ray diffraction analysis and to have the 5-6 nm of particles size with narrow size distribution by a TEM. And it was confirmed by the EA and FT-IR analyses that the surfaces of nanoparticles are coordinated with the solvent molecules, which will possibly keep from agglomerating between LaPO$_4$:Er nanoparticles. In the emission spectrum of $LaPO_4$:Er nanoparticle at NIR region, on the other hand, it was measured that the emission intensity is very weak, which is due to the transition from $^4$$I_{(13/2)}$ to $^4$$I_{(15/2)}$ of $Er^{3+ }$ion. It was interpreted that the weak luminescence of $LaPO_4$:Er is originated from the hydroxyl groups adsorbed on the surfaces of the nanoparticles, because OH group acts as an efficient quencher for the $^4$$I_{(13/2)}$ \longrightarrow $^4$$I_{(15/2)}$ emission of $Er^{3+}$ activator. But the co-doping of Yb$^{3+}$ as a sensitizer in this nanoparticle results in the increase of the emission intensity at 1539 nm due to the effective energy transfer from $Yb^{3+}$ to $Er^{3+}$ . In addition, the synthesized nanoparticles exhibited good dispersibility with some polymers and effective luminescence at NIR region.n.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.67-71
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• 2013

Porous $Al_2O_3$ dispersed with nano-sized Cu was fabricated by freeze-drying process and solution chemistry method using Cu-nitrate. To prepare porous $Al_2O_3$, camphene was used as the sublimable vehicle. Camphene slurries with $Al_2O_3$ content of 10 vol% were prepared by milling at $50^{\circ}C$ with a small amount of oligomeric polyester dispersant. Freezing of the slurry was done in a Teflon cylinder attached to a copper bottom plate cooled to $-25^{\circ}C$ while unidirectionally controlling the growth direction of the camphene. Pores were subsequently generated by sublimation of the camphene during drying in air for 48 h. The green body was sintered in a furnace at $1400^{\circ}C$ for 1 h. Cu particles were dispersed in porous $Al_2O_3$ by calcination and hydrogen reduction of Cu-nitrate. The sintered samples showed large pores with sizes of about $150{\mu}m$; these pores were aligned parallel to the camphene growth direction. Also, the internal walls of the large pores had relatively small pores due to the traces of camphene left between the concentrated $Al_2O_3$ particles on the internal wall. EDS analysis revealed that the Cu particles were mainly dispersed on the surfaces of the large pores. These results strongly suggest that porous $Al_2O_3$ with Cu dispersion can be successfully fabricated by freeze-drying and solution chemistry routes.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.53-58
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• 2013

Superhydrophobic $SiO_2$ layers with a micro-nano hierarchical surface structure were prepared. $SiO_2$ layers deposited via an electrospray method combined with a sol-gel chemical route were rough on the microscale. Au particles were decorated on the surface of the microscale-rough $SiO_2$ layers by use of the photo-reduction process with different intensities ($0.11-1.9mW/cm^2$) and illumination times (60-240 sec) of ultraviolet light. With the aid of nanoscale Au nanoparticles, this consequently resulted in a micro-nano hierarchical surface structure. Subsequent fluorination treatment with a solution containing trichloro(1H,2H,2H,2H-perfluorooctyl)silane fluorinated the hierarchical $SiO_2$ layers. The change in surface roughness factor was in good agreement with that observed for the water contact angle, where the surface roughness factor developed as a measure needed to evaluate the degree of surface roughness. The resulting $SiO_2$ layers revealed excellent repellency toward various liquid droplets with different surface tensions ranging from 46 to 72.3 mN/m. Especially, the micro-nano hierarchical surface created at an illumination intensity of $0.11mW/cm^2$ and illumination time of 60 sec showed the largest water contact angle of $170^{\circ}$. Based on the Cassie-Baxter and Young-Dupre equations, the surface fraction and work of adhesion for the micronano hierarchical $SiO_2$ layers were evaluated. The work of adhesion was estimated to be less than $3{\times}10^{-3}N/m$ for all the liquid droplets. This exceptionally small work of adhesion is likely to be responsible for the strong repellency of the liquids to the micro-nano hierarchical $SiO_2$ layers.

• Journal of Adhesion and Interface
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• v.20 no.4
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• pp.146-154
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• 2019

In this study, alkoxysilane-functionalized amphiphilic polymer (AFAP), which have hydrophilic segment and hydrophobic segment functionalized by alkoxysilane group at the same backbone, was synthesized and used as a dispersant and control agent for reaction rate in the preparation of colloidally stable organic-inorganic (O-I) hybrid sols. After reaction with fluorosilane compounds, fluorinated O-I hybrid sols were prepared and coated onto glass substrate to form hydrophobic O-I hybrid coating films through low-temperature curing process. Surface hardness and hydrophobicity of cured coating films were varied with type of solvent and composition of AFAP and fluorinated alkoxysilane compounds. At appropriate solvent and composition of fluorinated alkoxysilane compounds, O-I hybrid coating film having high transparency and surface hardness could be prepared, which could be applicable to cover window of solar cell and displays.