• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.135-138
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• 2001

We report the structural ,optical and electrical properties of ZnO thin films depending on the variation of the film thickness. The properties of the films deposited on sapphire (001) substrates using a pulsed laser deposition technique (PLD) were characterized with XRD, hall measurement and photoluminescence (PL). In our study, the increase of the thickness of ZnO thin films shows the improvement of the structural and optical properties. The electric properties of the films were also well matched with the structural and optical properties

• 한국식품과학회지
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• 제45권2호
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• pp.167-173
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• 2013

국내 다소비 건포류인 오징어채, 쥐포, 멸치를 대상으로 감마선 조사에 의한 이화학적 품질 특성 및 조사여부 확인 시험을 실시하였다. 모든 시료에서 조사선량의 증가에 따라 기계적 색도의 큰 변화는 관찰되지 않았지만 전반적 색차는 다소 증가하였다. 갈색도의 경우 오징어채와 쥐포는 수용성 갈색도가, 멸치는 지용성 갈색도가 높게 확인되었고, 쥐포의 갈색도는 조사선량에 따라 다소 증가하였다. TBA 값은 지방의 함량이 비교적 높은 오징어와 멸치의 경우 조사선량에 따라 증가하는 경향을 나타내었다. 광자극발광(PSL) 분석 결과, 멸치를 제외한 모든 조사시료에서 음성(-)과 중간값(M)을 나타냄에 따라 스크리닝 판정에 적합하지 않는 것으로 확인되었다. 그러나 열발광(TL) 분석에서는 모든 조사시료가 특유의 peak를 나타내었고, 강도 또한 선량에 비례적으로 증가하였으며, TL ratio 역시 기준 값에 만족하여 TL에 의한 조사여부 확인이 가능하였다. 관능평가 결과, 모든 시료에서 조사선량 간 유의적인 차이는 나타나지 않았다.

• Korean Chemical Engineering Research
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• 제49권5호
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• pp.594-599
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• 2011

분무열분해 공정을 이용하여 $SrAl_2O_4:Eu$ 녹색 형광체를 제조함에 있어 붕소의 치환, 유기첨가제 및 건조 조절제의 사용에 따른 발광 특성을 조사하였다. Al 자리에 붕소를 치환시켜 줌으로써 결정상은 순수해지고 발광강도는 크게 향상됨을 확인하였다. 휘도 측면에서 붕소의 함량은 약 1 at%로 하는 것이 가장 바람직하였다. 유기첨가제의 함량 변화에 따른 $Sr_{0.9}Al_{1.98}B_{0.02}O_4:Eu_{0.1}$ 형광체의 휘도 변화를 조사한 결과 0.2M을 사용했을 때 가장 높은 휘도를 얻었다. 유기첨가제와 함께 건조 조절제로 DMF 0.5M을 함께 사용함으로써 $Sr_{0.9}Al_{1.98}B_{0.02}O_4:Eu_{0.1}$ 형광체의 휘도는 약 172% 향상되었다. XRD 분석 결과에 의하면 사용한 유기첨가제와 DMF의 사용은 $Sr_{0.9}Al_{1.98}B_{0.02}O_4:Eu_{0.1}$ 형광체의 결정상 변화 없이 결정성을 크게 향상시켰다. 유기 첨가제만을 사용할 경우 형광체의 표면적은 커졌지만 DMF를 함께 사용함으로써 현저히 줄어들었다. 따라서 유기첨가제와 DMF를 동시에 사용하여 합성한 형광체의 휘도가 크게 향상된 것은 결정성 증가와 표면적 감소에 기인한 것이라고 결론지었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.360.1-360.1
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• 2016

Hydroxyapatite (Ca10(PO4)6(OH)2, HAP) particles have attracted a great deal of attention in biomedical fields due to their good biocompatibility, bioactivity and fairly broad applications as drug delivery, dental implant, bone cement, and etc. Thus, many researchers have made an effort to add new functionalities such as luminescence, drug delivery, and bone regeneration properties up to HAP powders by controlling their nanostructure as well as composition. In this research, the mesoporous strontium substituted HAP (Sr-HAP) microspheres were synthesized using a hydrothermal method. In this synthesis, aspartic acid monomers were utilized to form microsphere by controlling surface energy of HAP particles and Sr ions were substituted into Ca ion sites, which induced luminescence property in HAP powders. Moreover, the change in the amount of Sr substitution was found to influence the particle size, morphology, and concurrently surface area, which led to changing drug loading as well as drug release property. The amount of Sr influences the morphology, luminescent properties, particle size, surface area cell viability and drug loading property, which are investigated by SEM, TEM, XRD, FTIR, BET, XPS and in vitro test such as MTT assay and drug release test. In particular, the multifunctional Sr-HAP with molar ratios of 0.25 (Sr/(Ca+Sr)) possessed the strongest luminescent property as well as the superior drug loading and sustained release properties that were correspondent with large surface area and pore size. Our study indicates that the fabricated multifunctional Sr-HAP microspheres are quite useful for bone regeneration and drug delivery.

• Bulletin of the Korean Chemical Society
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• 제28권6호
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• pp.965-969
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• 2007

The spectral properties, namely the circular dichroism, electric absorption and luminescence properties, of Λ- and Δ-[Ru(II)(1,10-phenanthroline)2benzodipyrido[b:3,2-h:2',3'-j]phenazine]2+ ([Ru(phen)2BDPPZ]2+) in the presence and absence of single stranded poly(dA) and poly(dT) were compared in this work. In the presence of single stranded DNAs, hypochromism in the absorption spectrum and significant changes in the circular dichroism spectrum in the ligand absorption band were apparent, indicating the strong interaction of the [Ru(phen)2BDPPZ]2+ complex with the single stranded DNAs. The luminescence intensity of the Ru(II) complex decreased stoichiometrically with increasing concentrations of the single stranded DNAs. All of these spectral changes were independent of the configuration of the Ru(II) complex and the nature of the DNA bases. Therefore, it is conceivable that both enantiomers of the [Ru(phen)2BDPPZ]2+ complex interact electrostatically with the negatively charged phosphate groups of DNA. However, the spectral properties of [Ru(II)(1,10-phenanthroline)3]2+ were not altered even in the presence of single stranded DNAs. Therefore, the size of the ligand involved in the interaction of the metal complex with the phosphate group of DNA may play an important role, even when the nature of the interaction is electrostatic.

• Current Optics and Photonics
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• 제3권2호
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• pp.164-171
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• 2019

Photoluminescence (PL) properties of GaN-based light-emitting diodes (LEDs) were analyzed to study the effects of carrier leakage on the luminescence properties at room temperature. The electrical leakage and PL properties were compared for LEDs showing leakages at forward bias and an LED with an intentional leakage path formed by connecting a parallel resistance of various values. The leakages at the forward bias, which could be observed from the current-voltage characteristics, resulted in an increase in the excitation laser power density for the maximum PL efficiency (ratio of PL intensity to excitation power) as well as a reduction in the PL intensity. The effect of carrier leakages on PL properties was similar to the change in PL properties owing to a reduction of the photovoltage by a reverse current since the direction of the carrier movement under photoexcitation is identical to that of the reverse current. Valid relations between PL properties and electrical properties were observed as the PL properties deteriorated with an increase in the carrier leakage. The results imply that the PL properties of LED chips can be an indicator of the electrical properties of LEDs.

• BMB Reports
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• 제40권4호
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• pp.453-458
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• 2007

Bacterial luciferase is a heterodimeric enzyme, which catalyzes the light emission reaction, utilizing reduced FMN (FMNH2), a long chain aliphatic aldehyde and $O_2$, to produce green-blue light. This enzyme can be readily classed as slow or fast decay based on their rate of luminescence decay in a single turnover. Mutation of Glu175 in $\alpha$ subunit to Gly converted slow decay Xenorhabdus Luminescence luciferase to fast decay one. The following studies revealed that changing the luciferase flexibility and lake of Glu-flavin interactions are responsible for the unusual kinetic properties of mutant enzyme. Optical and thermodynamics studies have caused a decrease in free energy and anisotropy of mutant enzyme. Moreover, the role of Glu175 in transition state of folding pathway by use of stopped-flow fluorescence technique has been studied which suggesting that Glu175 is not involved in transition state of folding and appears as surface residue of the nucleus or as a member of one of a few alternative folding nuclei. These results suggest that mutation of Glu175 to Gly extended the structure of Xenorhabdus Luminescence luciferase, locally.

• 한국재료학회지
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• 제28권6호
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• pp.355-360
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• 2018

$LuNbO_4:0.2Yb^{3+},xTm^{3+}$ powders were prepared using a solid-state reaction process. The effects of the amount of Tm on up-conversion(UC) and down-conversion(DC) luminescence properties are investigated. X-ray diffraction patterns confirm that $Yb^{3+}$ and $Tm^{3+}$ ions are successfully incorporated into Lu sites. Under 980 nm excitation, the UC spectra of the powders predominantly exhibit strong near-infrared emission bands that peak at 805 nm, whereas weak 480 nm emission bands are observed as well. The emission bands are assigned to the $^1G_4{\rightarrow}^3H_6$ (480 nm) and 3 $^3H_4{\rightarrow}^3H_6$ (805 nm) transitions of the $Tm^{3+}$ ions via an energy transfer from $Yb^{3+}$ to $Tm^{3+}$; two- and three-photon UC processes are responsible for the 805 and 480 nm emissions, respectively. The DC emission spectra exhibit blue emission ($^1D_2{\rightarrow}^3F_4$) of $Tm^{3+}$ at 458 nm. The amount of Tm affects the emission intensity with the strongest emissions at x = 0.007 and 0.02 for the UC and DC luminescence, respectively. The results demonstrate that $LuNbO_4:Yb^{3+},Tm^{3+}$ phosphors are suitable for bio-applications.

• 한국분말재료학회지
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• 제12권4호
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• pp.279-283
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• 2005

In this study, the ZnS composite powders for host material in phosphor was synthesized in situ by mechanical alloying. As the mechanical alloying time increases, particle size of ZnS decreases. ZnS powders of $1.85\;\mu{m}$ in a mean size was fabricated by mechanical alloying for 10h. The crystal structures of ZnS powders were investigated by X-ray diffraction and the photo-luminescence properties was evaluated with the optical spectra analyzer. The steady state condition of mechanically alloyed ZnS was obtained as a mean particle size of $2\;\mu{m}$ in 5h milling. The sphalerite and wurtize structures coexist in the ZnS mechanically alloyed for 5h. The ZnS powder mechanically alloyed for 10h grows to the sphalerite structure. And the strong emission peaks of ZnS are observed at 480 nm wave length at the powders of mechanically alloyed for 10h, but the sphalerite and wurtize structures in ZnS coexist and emission peaks are not appeared at the powders of mechanically alloyed for 10h.

• 한국세라믹학회지
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• 제41권5호
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• pp.406-409
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• 2004

교류 구동 분산형 EL(ACPEL)에 사용되는 ZnS:Cu 청색 형광체를 고상 반응법으로 제조하였다. 1차 소성 후 인위적 결함을 형광체 표면에 도입함으로서 2차 소성 중에 의해 일어나는 ZnS의 상전이 및 EL 발광 휘도에 미치는 영향을 연구하였다. 즉 1차 소성된 형광체를 ball-mill 공정에서 인위적으로 표면에 defect를 형성시켜 ZnS의 저온상인 cubic으로의 전이가 용이하게 하여 EL구동하에서 발광 휘도를 증가시켰다. Ball-mill의 공정 변수로는 milling 시간과 rpm 등을 고려하여 각 조건에 따른 효과를 고찰하였으며, 발광 spectrum을 측정한 결과, 최적 조건에서 인위적인 결함을 형성하지 않은 형광체 보다 발광 휘도가 약 30% 이상 증가하였다. 또한 각기 다른 ball-mill 조건으로 합성된 형광체의 결정상을 분석하고 비교하였으며 상전이 특성에 따른 발광 휘도 변화를 고찰하였다.