• 한국결정성장학회지
• /
• 제30권3호
• /
• pp.91-95
• /
• 2020

본 연구는 BaTiO₃ 나노입자의 용액 공정의 분산성을 확보하기 위해 합성 시간과 온도 증가를 통한 입자들의 핵생성 속도 및 확산 속도를 동시에 증가시켜 수열합성을 진행하였다. 상대적으로 연구가 부족했던 20 nm 이하 균일한 크기의 BaTiO₃ 나노입자를 oleic acid 리간드를 매개로 180℃, 30시간의 조건에서 추가 공정 없이 합성하였다. 수열합성을 저온에서 짧은 시간 동안 진행하였을 시 입자의 응집과 크기의 불균일함을 확인하였으며, 고온에서 장시간 진행하였을 시 입자가 잘 분산되고 크기가 균일한 것을 확인하였다. 이는 고온에서 TiO₂ 입자의 핵 생성 속도와 Ba²⁺ 이온의 확산 거리 증가에 기인한다. 비극성 용매인 mesitylene에서 향상된 분산도를 보여준 BaTiO₃ 나노입자의 크기와 결정도 및 흡광도는 투과전자 현미경과 X-ray diffraction 및 자외/가시선 분광광도계를 통해 분석하였다. 본 연구 결과로 수열합성을 통한 BaTiO₃ 나노입자의 크기의 균일성과 분산성을 개선하고 다양한 전자소자에 응용 가능할 것이라 예상한다.

• Bulletin of the Korean Chemical Society
• /
• 제32권1호
• /
• pp.141-144
• /
• 2011

We report the synthesis of $SrTiO_3$, $BaTiO_3$ and $Ba_xSr_{1-x}TiO_3$ (BST) nanoparticles (NPs) in various compositions (x = 0.25, 0.5 and 0.75) by an inorganic sol-gel method under a basic condition. Highly crystalline nanoparticles were formed at the reaction temperature of 25 - $100^{\circ}C$ from a stabilized titanium alkoxide in tetramethylammonium hydroxide (TMAH) and barium or strontium acetate in aqueous solution. Morphology and particle structure of the synthesized BST NPs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The BST nanoparticles in various compositions were monodispersed without mutual aggregation, and their average sizes were in the range of 70 - 80 nm. Furthermore, they showed highly crystallized perovskite phase over the whole composition range from $SrTiO_3$ to $BaTiO_3$. We also proposed a mechanism for the low-temperature formation of BST NPs.

• Natural Product Sciences
• /
• 제26권3호
• /
• pp.207-213
• /
• 2020

Characterization and in vitro inhibition studies of protease inhibitor from the mushroom Pleurotus floridanus (PfTI) towards the pest Papilio demoleus is studied. The addition of 1 mM Mn²⁺, Na²⁺, Ba²⁺ and Ni ²⁺ enhanced the PfTI activity. The ICP-atomic emission spectrum showed the presence of Ca²⁺, Mg²⁺ and Zn²⁺ in the PfTI. Surfactants SDS and CTAB at a concentration of 1% reduced the PfTI activity whereas, the nonionic detergents Triton X and Tween 80 increased the activity. The inhibitory activity gradually decreased with increase in concentration of DMSO and H₂O₂. The activity was increased by dithiothreitol up to a concentration of 80 μM and inactivated at 140 μM. The activity of PMSF modified PfTI was drastically reduced to 0.234 U/mL at 4 mM concentration and similar results were obtained for modification of cysteine by N-Ethylmaleimide at slightly higher concentrations. The complex of trypsin and PfTI showed complete loss in fluorescence intensity at 343 nm compared with control. In vitro inhibition studies of PfTI with midgut proteases isolated from citrus pest P. demoleus with protease activity of 1.236 U was decreased to 0.613 U by 50 μL (0.1 mg/mL) of the inhibitor. Inhibitor was stable up to 0.04 M concentration of HCl.

• 한국분말재료학회지
• /
• 제31권1호
• /
• pp.16-22
• /
• 2024

Composite-based piezoelectric devices are extensively studied to develop sustainable power supply and self-powered devices owing to their excellent mechanical durability and output performance. In this study, we design a lead-free piezoelectric nanocomposite utilizing (Ba_0.85 Ca_0.15)(Ti_0.9Zr_0.1)O₃ (BCTZ) nanomaterials for realizing highly flexible energy harvesters. To improve the output performance of the devices, we incorporate porous BCTZ nanowires (NWs) into the nanoparticle (NP)-based piezoelectric nanocomposite. BCTZ NPs and NWs are synthesized through the solid-state reaction and sol-gel-based electrospinning, respectively; subsequently, they are dispersed inside a polyimide matrix. The output performance of the energy harvesters is measured using an optimized measurement system during repetitive mechanical deformation by varying the composition of the NPs and NWs. A nanocomposite-based energy harvester with 4:1 weight ratio generates the maximum open-circuit voltage and short-circuit current of 0.83 V and 0.28 ㎂, respectively. In this study, self-powered devices are constructed with enhanced output performance by using piezoelectric energy harvesting for application in flexible and wearable devices.

• 한국전기전자재료학회논문지
• /
• 제35권1호
• /
• pp.72-79
• /
• 2022

Piezoelectric energy harvesting technologies, which can be used to convert the electricity from the mechanical energy, have been developed in order to assist or power the wearable electronics. To realize non-toxic and biocompatible electronics, the lead-free (Ba_0.85Ca_0.15)(Ti_0.90Zr_0.10)O₃ (BCTZ) nanoparticles (NPs) are being studied with a great attention as flexible energy harvesting device. Herein, piezoelectric hybrid nanocomposites were fabricated using BCTZ NPs-embedded poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] matrix to improve the performance of flexible energy harvester. Output performance of the fabricated energy device was investigated by the well-optimized measurement system during the periodically bending and releasing motions. The generated open-circuit voltage and the short-circuit current of the piezoelectric hybrid nanocomposite-based energy harvester reached up to ~15 V and ~1.1 ㎂, respectively; moreover, the instantaneous power of 3.5 ㎼ is determined from load voltage and current at the external load of 20 MΩ. This research is expected to cultivate a new approach to high-performance wearable self-powering electronics.