• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2505-2511
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• 2014

Indium oxide nanocrystals ($In_2O_3$ NCs) with sizes of 5.5 nm-10 nm were synthesized by hot injection of the mixture precursors, indium acetate and oleic acid, into alcohol solution (1-octadecanol and 1-octadecence mixture). Field emission transmission electron microscopy (FE-TEM), High resolution X-Ray diffraction (X-ray), Nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FT-IR) were employed to investigate the size, surface molecular structure, and crystallinity of the synthesized $In_2O_3$ NCs. When covered by oleic acid as a capping group, the $In_2O_3$ NCs had a high crystallinity with a cubic structure, demonstrating a narrow size distribution. A high mobility of $2.51cm^2/V{\cdot}s$ and an on/off current ratio of about $1.0{\times}10^3$ were observed with an $In_2O_3$ NCs thin film transistor (TFT) device, where the channel layer of $In_2O_3$ NCs thin films were formed by a solution process of spin coating, cured at a relatively low temperature, $350^{\circ}C$. A size-dependent, non-monotonic trend on electron mobility was distinctly observed: the electron mobility increased from $0.43cm^2/V{\cdot}s$ for NCs with a 5.5 nm diameter to $2.51cm^2/V{\cdot}s$ for NCs with a diameter of 7.1 nm, and then decreased for NCs larger than 7.1 nm. This phenomenon is clearly explained by the combination of a smaller number of hops, a decrease in charging energy, and a decrease in electronic coupling with the increasing NC size, where the crossover diameter is estimated to be 7.1 nm. The decrease in electronic coupling proved to be the decisive factor giving rise to the decrease in the mobility associated with increasing size in the larger NCs above the crossover diameter.

• 한국식품과학회지
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• 제51권4호
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• pp.330-335
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• 2019

Moth bean (MB), navy bean (NB), soybean (SB)에서 분리된 arabinogalactans (AGs)의 성분과 유변학적 성질을 조사하였다. AGs의 주성분은 갈락토즈(galactose)와 아라비노즈(arabinose)로 총합이 약 59-89%를 나타내었고 갈락토즈와 아라비노즈의 비율(G/A)은 MB는 0.21, NB는 0.38, SB는 1.09로 계산되었다. 유변학적 거동을 살펴보기 위하여 1-5% (w/v) AG 용액들의 전단속도(shear rate) $0.1-100s^{-1}$에 따르는 전단응력(shear stress)을 측정하였을 때 MB의 경우 항복점(yield stress)이 없었으나, 5% NB 용액에서는 2.10 Pa, 2.5% SB용액에서는 1.98 Pa의 항복점이 각각 측정되었다. 순환 전단 측정 결과 5% MB 용액의 경우는 점성도는 전단 속도가 증가할 때에 비해 감소할 때 더 큰 값을 나타내어 rheopexy인 유변학적 성질이 나타났다. 반면 5% NB와 SB 용액의 유변학적 성질은 전단속도가 증가할 때의 점성도가 감소할 때의 점성도보다 더 큰 값을 가지는 thixotrophy로 나타났다. 저장탄성률(G'), 손실탄성률(G")을 측정한 결과 MB 분산액은 탄성율이, NB 분산액은 점성율이 높게 나타났고 SB 분산액은 비교적 낮은 농도에서는 탄성율이 비교적 높은 농도에서는 점성율이 크게 나타났다. 사전전단(pre-shearing)을 $500s^{-1}$에서 600초 동안 가공 후에 실시한 진동 테스트로 AGs의 구조 회복을 살펴본 결과 MB 5% 용액은 G', G" 모두 감소하였고 특히 탄성 부분이 많이 감소하였다. NB 5% 용액의 G'는 감소하였으나 MB에 비하여 그 폭은 작았고 G"는 거의 변화가 없었다. SB 2.5% 용액의 G', G" 모두 증가하는 현상을 나타내었다. AGs 용액의 전단 응력과 진동수에 따라 나타나는 점성 및 탄성의 변화 현상을 이용하여 식품 및 약품 제조에 첨가제 및 가소제로서 물질의 특성을 결정하는데 도움을 줄 수 있다. MB, NB, SB 물질의 유변학적 거동과 화학적 구조 관계를 밝히기 위하여 알디톨 아세테이트 결합 분석과 NMR분석(de Oliveira 등, 2013; Wang 등, 2015)을 통한 분자구조연구를 추가적으로 진행하고자 한다.

• Bulletin of the Korean Chemical Society
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• 제28권1호
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• pp.33-40
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• 2007

We have designed and synthesized three Zn(II)-porphyrin derivatives, such as Zn(II) porphyrin ([G-0]Zn-P1) and aryl ether-typed dendron substituted Zn(II)-porphyrin derivatives ([G-1]Zn-P1 and [G-1]Zn-P-CN1). Their chemical structures were characterized by 1H-NMR, FT-IR, UV-vis absorption, EI-mass, and MALDI-TOF mass spectroscopies. Their electrochemical properties were studied by cyclic voltammetry measurement. These Zn(II)-porphyrin derivatives have been used to fabricate dye-sensitized solar cells (DSSCs) based on solid polymeric electrolytes as dye sensitizers and their device performances were evaluated by comparing with that of a standard Ru(II) complex dye. [G-1]Zn-P-CN1 showed the enhanced power conversion efficiency than those of other porphyrin derivatives, as expected. Short-circuit photocurrent density (Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (η) of solid-typed DSSC for [G-1]Zn-P-CN1 were evaluated to be Jsc = 11.67 mA/cm2, Voc = 0.51 V, FF = 0.46, and η = 2.76%, respectively.