• 통합자연과학논문집
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• 제3권4호
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• pp.202-205
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• 2010

Nanocrystalline porous silicon surfaces have been used to detect nitroaromatic compounds in vapor phase. The mode of photoluminescence is emphasized as a sensing attitude or detection technique. Quenching of photoluminescence from nanocrystalline porous surfaces as a transduction mode is measured upon the exposure of nitroaromatic compounds. Reversible detection mode for nitroaromatics is, too, observed. To verify the detection afore-mentioned, photoluminescent freshly prepared porous silicons are functionalized with different groups. The mechanism of quenching of photoluminescence is attributed to the electron transfer behaviors of quantum-sized nano-crystallites in the porous silicon matrix to the analytes(nitroaromatics). An attempt has been done to prove that the surface-derivatized photoluminescent porous silicone surfaces can act as versatile substrates for sensing behaviors due to having a large surface area and highly sensitive transduction mode.

• 한국전기전자재료학회논문지
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• 제31권7호
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• pp.443-449
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• 2018

We investigated the temperature-dependent photoluminescence spectroscopy of colloidal InZnP/ZnSe/ZnS (core/shell/shell) quantum dots with varying ZnSe and ZnS shell thickness in the 278~363 K temperature range. Temperature-dependent photoluminescence of the InZnP-based quantum dot samples reveal red-shifting of the photoluminescence peaks, thermal quenching of photoluminescence, and broadening of bandwidth with increasing temperature. The degree of band-gap shifting and line broadening as a function of temperature is affected little by shell composition and thickness. However, the thermal quenching of the photoluminescence is strongly dependent on the shell components. The irreversible photoluminescence quenching behavior is dominant for thin-shell-deposited InZnP quantum dots, whereas thick-shelled InZnP quantum dots exhibit superior thermal stability of the photoluminescence intensity.

• 통합자연과학논문집
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• 제3권2호
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• pp.117-121
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• 2010

Silicon quantum dots base on photoluminescent porous silicon were prepared from an electrochemical etching of n-type silicon wafer (boron-dopped<100> orientation, resistivity of 1~10 ${\Omega}-cm$) and used as a alcohol sensor. Silicon quantum dots displayed an emission band at the wavelength of 675 nm with an excitation wavelength of 480 nm. Photoluminescence of silicon quantum dots was quenched in the presence of alcohol vapors such as methanol, ethanol, and isopropanol. Quenching efficiencies of 21.5, 32.5, and 45.8% were obtained for isopropanol, ethanol, and methanol, respectively. A linear relationship was obtained between quenching efficiencies and vapor pressure of analytes used. Quenching photoluminescence was recovered upon introducing of fresh air after the detection of alcohol. This provides easy fabrication of alcohol sensor based on porous silicon.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.157-161
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• 2000

Blue phosphor of Ba-Mg-Al-O:Eu$^{2+}$ phase was fabricated by conventional firing techniques under reducing atmosphere and its photoluminescence properties are studied with varying Eu concentration and phost-annealing temperature under air atmosphere. This phosphors were well crystallized with particle size in the range of 3~5um and emitted a blue light at a dominent wavelength 450nm for 254nm UV irradiation. The concentration quenching wit Eu$^{2+}$ was that with increasing Eu concentration the energy transfer between the activator ions steadily improves, so that the excitation energy is transported over larger distances through the lattice before luminescence can occur. Thermal quenching also occurred in this phosphor means that in a host lattice with the $\beta$-alumina structure the bond of an Eu$^{2+}$ ion with the nearest-neighbour oxygen ion is much stronger than in a lattice with the magnetoplumbite structure.cture.

• Current Photovoltaic Research
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• 제6권4호
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• pp.91-93
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• 2018

Polythiophene-$TiO_2$ composite was synthesized with different molar ratios of thiophene and titaniumisopropoxide ($Ti(OPr)_4$) for flexible solar cell application as a flexible electrode or an active material. The $Ti(OPr)_4$ was stabilized by thiophene. The thiophene was polymerized by ferric chloride catalyst. The synthesized polythiophene exhibited strong UV-visible absorption in the range of the wavelength shorter than 500 nm. Field emission scanning electron microscope (FESEM) image of low concentration of $TiO_2$ film showed smooth surface. However, FESEM image of high concentration of $TiO_2$ film exhibited relatively rough surface. Polythiophene concentration dependent strong photoluminescence quenching of surfrhodamine-B was observed.

• Transactions on Electrical and Electronic Materials
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• 제1권3호
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• pp.6-9
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• 2000

Selectively excited photoluminescence(PL) spectroscopy has been carried out on the ~1540 nm $^{4}$I$_{13}$ 3/ to $^{4}$I/wub 15/2/ emissions of the multiple Er$^{3+}$ centers observed in Er-implante undoped and Mg-doped GAN at temperatures ranging from 6K to 295K. The temperature dependence of the Er$^{3+}$ PL spectra selectively excited by below -gap light demonstrates different quenching rates for the distinct Er$^{3+}$ centers, and indicates that the PL spectra with the most rapid thermal quenching rats do not contribute to the room temperature, above-p-pumped Er$^{3+}$ spectrum. In addition, selective PL spectroscopy has ben carried out on the Er$^{3+}$ emission in Er-implanted undoped and Mg-doped GaN at temperatures ranging 6K to 295K. The results indicate that the previously reported enhancement of the violet-pumped centers contribution to the low temperature above excited Er$^{3+}$ PL in Mg-doped GaN is also evident at room temperature.temperature.

• 한국재료학회지
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• 제31권10호
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• pp.582-585
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• 2021

Y₂O₃:Eu_x (x = 0.005, 0.01, 0.02, 0.03, 0.05, 0.1 mol) phosphors are synthesized with different concentrations of Eu³⁺ ions by solvothermal method. The crystal structure, surface and optical properties of the Eu doped Y₂O₃ phosphors are investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) and photoluminescence excitation (PLE) analyses. From X-ray diffraction (XRD) results, the crystal structure of the Eu doped Y₂O₃ phosphor is found to be cubic. The maximum emission spectra of the Eu doped Y₂O₃ phosphors are observed at 0.05 mol Eu³⁺ concentration. The photoluminescence of 615 nm in the Eu doped Y₂O₃ phosphors is associated with ⁵D₀ → ⁷F₂ transition of Eu³⁺ ions. The decrease in emission intensity of 0.1 mol Eu doped Y₂O₃ is interpreted by concentration quenching. The International Commission on Illumination (CIE) coordinates of 0.05 mol Eu doped Y₂O₃ phosphor are X = 0.6547, Y = 0.3374.

• 대한화학회지
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• 제60권2호
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• pp.131-136
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• 2016

CdSe 기반 나노결정의 구리이온에 의한 형광 소광 특성 및 아연이온에 의한 형광 회복 특성을 관찰하였다. 구리이온이 첨가되었을 경우, CdSe 양자점에서는 매우 빠르고 급격한 형광 소광 특성을 보이는 반면에 CdSe 나노라드의 경우에서는 형광이 서서히 소광되는 특성을 보인다. 구리이온으로 형광을 소광시킨 CdSe/CdS(핵/껍질) 양자점에 아연이온이 첨가되면 소광된 양자점의 형광이 회복된다. 용액 내 1 μM의 아연농도에서 양자점의 형광이 50% 증가됨을 확인하였으며, 아연 농도가 증가함에 따라 양자점의 형광세기가 증가되며 이는 Langmuir binding isotherm 모델로 해석할 수 있다. 이러한 연구를 바탕으로 CdSe 기반의 나노결정을 이용한 형광 화학 센서를 구현할 수 있을 것으로 기대한다.

• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1491-1504
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• 2012

InP quantum dot (QD)-organosilicon nanocomposites were synthesized and their photoluminescence quenching was mainly investigated because of their applicability to white LEDs (light emitting diodes). The as-synthesized InP QDs are capped with myristic acid (MA), which are incompatible with typical silicone encapsulants. We have introduced a new ligand, 3-aminopropyldimethylsilane (APDMS), which enables embedding the QDs into vinyl-functionalized silicones through direct chemical bonding. The exchange of ligand from MA to APDMS does not significantly affect the UV absorbance of the InP QDs, but quenches the PL to about 10% of its original value with the relative increase in surface related emission intensities, which is explained by stronger coordination of the APDMS ligands to the surface indium atoms. InP QD-organosilicon nanocomposites were synthesized by connecting the QDs using a short cross-linker such as 1,4-divinyltetramethylsilylethane (DVMSE) by the hydrosilylation reaction. The formation and changes in the optical properties of the InP QD-organosilicon nanocomposite were monitored by ultraviolet visible (UV-vis) absorbance and steady state photoluminescence (PL) spectroscopies. As the hydrosilylation reaction proceeds, the QD-organosilicon nanocomposite is formed and grows in size, causing an increase in the UV-vis absorbance due to the scattering effect. At the same time, the PL spectrum is red-shifted and, very interestingly, the PL is quenched gradually. Three PL quenching mechanisms are regarded as strong candidates for the PL quenching of the QD nanocomposites, namely the scattering effect, F$\ddot{o}$rster resonance energy transfer (FRET) and cross-linker tension preventing the QD's surface relaxation.

• 한국진공학회지
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• 제2권3호
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• pp.294-298
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• 1993

CuGaSe2 단결정을 고순도(99.9999%)의 Cu, Se 원소를 화학조성비로 칭량한 후 Se을 3mole% 과잉으로 첨가하여 합성된 ingot를 사용하여 iodine(99.9999%)을 수송매체로 한 화학수송법으로 성장시켰다. 성장된 단결정은 검정색을 띠고 있었으며, 10K에서 optical energy gap이 1.755eV로 주어졌다. Ar-ion laser로 여기시켜 측정한 photoluminescence(PL) 스펙트럼으로부터 1.667eV, 1.085eV, 1.025eV에 위치한 세 개의 PL peak를 얻었다. Thermally stimulated current(TSC) 측정에서 0.660eV, 0.720eV의 deep donor level을 관측하였으며, PL peak intensity의 thermal quenching으로 구한 activation energy는 0.010eV이었다. CuGaSe2 단결정에서 PL mechanism은 edge emission 및 donor-acceptor pair recombination임을 규명했다.