• 한국세라믹학회지
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• 제55권5호
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• pp.510-514
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• 2018

Colloidal semiconductor quantum dots (QDs), because of the novel optical and electrical properties that stem from their three-dimensional confinement, have attracted great interest for their potential applications in such fields as bio-imaging, display, and opto-electronics. However, many semiconductors that can be exploited for QD applications contain toxic elements. Herein, we synthesized non-toxic ZnTe/ZnSe (core/shell) type-II QDs by pyrolysis method. Because of the unique type-II character of these QDs, their emission can range over an extended wavelength regime, showing photoluminescence (PL) from 450 nm to 580 nm. By optimizing the ZnSe shell growth condition, resulting ZnTe/ZnSe type-II QDs shows PL quantum yield up to ~ 25% with 35 nm PL bandwidth. Using a simple two step cation exchange reaction, we also fabricated ZnTe/ZnSe type-II QDs with absorption extended over the whole visible region. The visible-light sensitized heavy metal free ZnTe/ZnSe type-II QDs can be relevant for opto-electronic applications such as displays, light emitting diodes, and bio-imaging probes.

• 한국재료학회지
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• 제14권2호
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• pp.146-151
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• 2004

We investigated the effects of high potential barriers on the optical characteristics of InAs quantum dots (QDs) by using photoluminescence (PL) and photoreflectance (PR) spectroscopy. A sample with regular InAs quantum dots on GaAs was grown by molecular beam epitaxy (MBE) as a reference. Another InAs QDs sample was embedded in single AlGaAs barriers. On the other hand, a sample with GaAs/AlGaAs superlattice barriers was adopted for comparison with a sample with a single AlGaAs layer. In results, we found that the emission wavelength of QDs was effectively tailored by using high potential barriers. Also, it was found that the optical properties of a sample with QDs embedded in GaAs/AlGaAs superlattices were better than those of a sample with QDs embedded in a single layer of AlGaAs barriers. We believe that GaAs/AlGaAs superlattice could effectively prevent the generation of defects.

• 대한두개안면성형외과학회지
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• 제12권1호
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• pp.22-27
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• 2011

Purpose: Packing the nose is a common procedure after the closed reduction of a nasal bone fracture to prevent postoperative complications, such as bleeding and adhesion formation as well as to stabilize the framework of the nasal bone. On the other hand, it is difficult for a patient to endure nasal packing because of breathing difficulties, headaches, chest discomfort, insomnia, general weakness and hypoxia. This study examined the availability of a bronchodilator to improve the decreased oxygen saturation and postoperative symptoms on nasal packing. Methods: From February, 2010 to July, 2010, a prospective randomized comparison of the incidence of a range of postoperative signs and symptoms was conducted on 60 patients, who did (n=30) and did not (n=30) undergo bronchodilator infusion (aminophylline 250 mg/10 mL + normal saline 100 mL IV qd) following nasal packing. The postoperative symptoms and oxygen saturation in the two groups were compared. Results: Patients who had infused the bronchodilator showed improved oxygen saturation. Nevertheless, there were no significant differences in the postoperative uncomfortable symptoms (dyspnea, headache, chest discomfort, insomnia, general weakness) between the two groups. Conclusion: A bronchodilator after nasal packing improves oxygen saturation by dilating the airway tract but it cannot reduce the uncomfortable symptoms caused by nasal obstruction. Overall, the bronchodilator is a useful medication for improving the level of oxygen saturation.

• Applied Science and Convergence Technology
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• 제27권5호
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• pp.109-112
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• 2018

Optical properties of InAs/GaAs submonolayer-quantum dot (SML-QD) have been investigated using excitation intensity ($I_{ex}$)- and temperature-dependent photoluminescence (PL). At a low temperature (13 K) strong PL was observed at 1.420 eV with a very narrow full-width at half maximum, of 7.09 meV. The results of the $I_{ex}$ dependence show that the PL intensities increase with increasing $I_{ex}$. The enhancement factors (k) of PL increment as a function of $I_{ex}$ are 3.3 and 1.22 at low and high $I_{ex}$ regime, respectively. The high k value at low $I_{ex}$, implies that the activation energy of the SML-QDs is low. The calculated activation energy of the SML-QDs from temperature dependence is 30 meV.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.656-662
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• 2021

For the high efficiencies of quantum dot-sensitized solar cells (QDSCs), it is important to control the severe electron recombination at the interface of photoanode/electrolyte. In this work, we optimize the surface passivation process of ZnS/SiO₂ double overlayers for the enhanced photovoltaic performances of QDSCs. The overlayers of zinc sulfide (ZnS) and SiO₂ are coated on the surface of QD-sensitized photoanode by successive ionic layer adsorption and reaction (SILAR) method, and sol-gel reaction, respectively. In particular, for the sol-gel reaction of SiO₂, the influences of temperature of precursor solution are investigated. By application of SiO₂ overlayers on the ZnS-coated photoanode, the conversion efficiency of QDSCs is increased from 5.04% to 7.35%. The impedance analysis reveals that the electron recombination at the interface of photoanode/electrolyte is obviously reduced by the SiO₂ overlayers.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2975-2981
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• 2020

Radiation damage is one of the aging important causes in nuclear reactors. Radiation damage causes changes in material properties. In this study, this effect has been evaluated and analyzed on the clad of the Tehran research reactor (TRR). A grade 6061 aluminum is used as a clad in the TRR. The MCNPX code is used to designate the most sensitive location of the reactor and calculate neutron flux distribution. Then, a software using FORTRAN language programming is developed to process the particle track (PTRAC) output file of the MCNPX code. The SRIM code is used here to calculate the rate of displacement per atom. Moreover, the SPECOMP and SPECTER codes are also applied to estimate the displacement rate and compared with the results attained using the SRIM code. The rate of displacement per atom by the SPECTER and SRIM codes have been obtained 2.54 × 10^-7 dpa/s and 2.44 × 10^-7 dpa/s (QD method), respectively. Also, the mechanical properties have been evaluated using the RCC-MRx code and have been compared with experimental results. Finally, the change in the matter specification has been analyzed as a function of time.

• 한국초전도ㆍ저온공학회논문지
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• 제24권4호
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• pp.29-35
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• 2022

We fabricated MHOS (multi-HTS layers on one substrate) high-temperature superconducting (HTS) REBCO conductors using HTS REBCO coated conductor (CC) A-specimen, which induces an artificial magnetic flux pinning effect, and HTS REBCO CC B-specimen, that does not induce this effect. The superconducting magnetic properties of the fabricated MHOS conductors were examined by measuring their magnetic moment m(H) curves using a physical property measurement system (QD PPMS-14). The critical current density (J_c) characteristics of our four-layered MHOS HTS REBCO conductor specimens such as BAAB, BBBB, and AAAA were lower than those of their two-layered and three-layered counterparts. At a temperature T of 30 K the magnetic flux pinning physical indicator δ values (obtained from the relationship J_c ∝ H^-δ) of the three-layer ABA (δ = 0.35) and two-layer AB (δ = 0.43) specimens were found to be significantly lower than those of the four-layer ABBA (δ = 0.51), BAAB (δ = 0.60), AAAA (δ = 0.78) and BBBB (δ = 0.81) structures.

• 센서학회지
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• 제31권2호
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• pp.125-130
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• 2022

We describe the importance of zinc oxide nanoparticle (ZnO NP) concentration in the enhancement of electrical properties in a lead sulfide quantum dot (PbS QD)-based shortwave infrared (SWIR) photodetector. ZnO NPs were synthesized using the sol-gel method. The concentration of the ZnO NPs was controlled as 20, 30 and 40 mg/mL in this study. Note that the ZnO NPs layer is commonly used as an electron transport layer in PbS QDs SWIR photodetectors. The photo-to-dark ratio, which is an important parameter of a photodetector, was intensively examined to evaluate the electrical performance. The 20 mg/mL condition of ZnO NPs exhibited the highest photo-to-dark ratio value of 5 at -1 V, compared with 1.8 and 0.4 for 30 mg/mL and 40 mg/mL, respectively. This resulted because the electron mobility decreased when the concentration of ZnO NPs was higher than the optimized value. Based on our results, the concentration of ZnO NPs was observed to play an important role in the electrical performance of the PbS QDs SWIR photodetector.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.189-189
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• 2016

Recently, many researchers have shown an increased interest in colloidal quantum dots (QDs) due to their unique physical and optical properties of size control for energy band gap, narrow emission with small full width at half maxima (FWHM), broad spectral photo response from ultraviolet to infrared, and flexible solution processing. QDs can be widely used in the field of optoelectronic and biological applications and, in particular, colloidal QDs based light emitting diodes (QDLEDs) have attracted considerable attention as an emerging technology for next generation displays and solid state lighting. A few methods have been proposed to fabricate white color QDLEDs. However, the fabrication of white color QDLEDs using single QD is very challenging. Recently, hybrid nanocomposites consisting of CdTe/ZnO heterostructures were reported by Zhimin Yuan et al.[1] Here, we demonstrate a novel but facile technique for the synthesis of CdTe/ZnO/G.O(graphene oxide) quasi-core-shell-shell quantum dots that are applied in the white color LED devices. Our best device achieves a maximum luminance of 484.2 cd/m2 and CIE coordinates (0.35, 0.28).

• 셀메드
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• 제1권1호
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• pp.6.1-6.4
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• 2011

For cancer patients undergoing radiation therapy (RT) or systemic chemotherapy (CHT), cancer-related fatigue (CRF) is a common problem that can negatively impact their quality of life. Guarana (Paullinia cupana) is a plant native to the Amazon basin that has been used as a stimulant since pre-Columbian times. PURPOSE: To evaluate the effectiveness of guarana extract on fatigue in BC patients undergoing either CHT or RT. A total of 137 cancer patients (85% with Breast Cancer) undergoing either CHT (101) or RT (36) were randomized to receive either a placebo or guarana. In all 3 studies, the guarana was given as an unmanipulated dry extract at a dose of 75 mg PO QD in the first two studies or 50 mg PO BID in the third study. Patients were crossed over to the other experimental arm, and we evaluated fatigue with the Chalder Scale in all three studies. Guarana significantly improved the The Chalder Scale Global Scores (- 0.85; 95% CI:-1.31 to -0.40; p = 0.0002); Physical Fatigue Scores (-0.44; 95% CI: - 0.74 to - 0.13; p = 0.005) and Mental Fatigue Scores (-0.93; 95% CI: - 1.14 to - 0.72; p < 0.00001). Guarana did not produce any CTCAE grades 3 or 4 toxicities in any of the studies. Guarana is an effective, cheap and non-toxic alternative for the treatment of fatigue in cancer patients undergoing treatment.