• Journal of Microbiology and Biotechnology
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• v.33 no.1
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• pp.127-134
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• 2023

Laccase activity is influenced by copper (Cu) as an inducer. In this study, laccase was immobilized on Cu and Cu-magnetic (Cu/Fe₂O₄) nanoparticles (NPs) to improve enzyme stability and potential applications. The Cu/Fe₂O₄ NPs functionally activated by 3-aminopropyltriethoxysilane and glutaraldehyde exhibited an immobilization yield and relative activity (RA) of 93.1 and 140%, respectively. Under optimized conditions, Cu/Fe₂O₄ NPs showed high loading of laccase up to 285 mg/g of support and maximum RA of 140% at a pH 5.0 after 24 h of incubation (4℃). Immobilized laccase, as Cu/Fe₂O₄-laccase, had a higher optimum pH (4.0) and temperature (45℃) than those of a free enzyme. The pH and temperature profiles were significantly improved through immobilization. Cu/Fe₂O₄-laccase exhibited 25-fold higher thermal stability at 65℃ and retained residual activity of 91.8% after 10 cycles of reuse. The degradation of bisphenols was 3.9-fold higher with Cu/Fe₂O₄-laccase than that with the free enzyme. To the best of our knowledge, Rhus vernicifera laccase immobilization on Cu or Cu/Fe₂O₄ NPs has not yet been reported. This investigation revealed that laccase immobilization on Cu/Fe₂O₄ NPs is desirable for efficient enzyme loading and high relative activity, with remarkable bisphenol A degradation potential.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.400-401
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• 2012

그래핀(Graphene)은 열 전도도가 높고 전자 이동도(200 000 cm2V-1s-1)가 우수한 전기적 특성을 가지고 있어 전계 효과 트랜지스터(Field effect transistor; FET), 유기 전자 소자(Organic electronic device)와 광전자 소자(Optoelectronic device) 같은 반도체 소자에 응용 가능하다. 그러나 에너지 밴드 갭이 없기 때문에 소자의 전기적 특성이 제한되는 단점이 있다. 최근에는 아크 방출(Arc discharge method), 화학적 기상 증착법(Chemical vapor deposition; CVD), 이온-조사법(Ion-irradiation) 등을 이용한 이종원자(Hetero atom)도핑과 화학적 처리를 이용한 기능화(Functionalization) 등의 방법으로 그래핀을 도핑 후 에너지 밴드 갭을 형성시키는 연구 결과들이 보고된 바 있다. 그러나 이러한 방법들은 표면이 균일하지 않고, 그래핀에 많은 결함들이 발생한다는 단점이 있다. 이러한 단점을 극복하기 위해 자가조립 단층막(Self-assembled monolayers; SAMs)을 이용하여 이산화규소(Silicon oxide; SiO2) 기판을 기능화한 후 그 위에 그래핀을 전사하면 그래핀의 일함수를 쉽게 조절하여 소자의 전기적 특성을 최적화할 수 있다. SAMs는 그래핀과 SiO2 사이에 부착된 매우 얇고 안정적인 층으로 사용된 물질의 특성에 따라 운반자 농도나 도핑 유형, 디락 점(Dirac point)으로부터의 페르미 에너지 준위(Fermi energy level)를 조절할 수 있다[1-3]. 본 연구에서는 SAMs한 기판을 이용하여 그래핀의 도핑 효과를 확인하였다. CVD를 이용하여 균일한 그래핀을 합성하였고, 기판을 3-Aminopropyltriethoxysilane (APTES)와 Borane-Ammonia(Borazane)을 이용하여 각각 아민 기(Amine group; -NH2)와 보론 나이트라이드(Boron Nitride; BN)로 기능화한 후, 그 위에 합성한 그래핀을 전사하였다. 기판 위에 NH2와 BN이 SAMs 형태로 존재하는 것을 접촉각 측정(Contact angle measurement)을 통해 확인하였고, 그 결과 NH2와 BN에 의해 그래핀에 도핑 효과가 나타난 것을 라만 분광법(Raman spectroscopy)과 X-선 광전자 분광법(X-ray photoelectron spectroscopy: XPS)을 이용하여 확인하였다. 본 연구 결과는 안정적이면서 패턴이 가능하기 때문에 그래핀을 기반으로 하는 반도체 소자에 적용 가능할 것이라 예상된다.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.2
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• pp.133-139
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• 2018

Chemically damaged hair is vulnerable to external stimuli in daily life due to the weakened physical properties of the hair strand itself. The purpose of this work was to determine whether chemical conjugation between hair keratin proteins restores tensile strength and thus results inpreventing further deterioration under repeated combing. A model damaged hair tress was produced by a typical perm-process. Then, it was internally crosslinked by the bifunctional crosslinker (3-aminopropyl)triethoxysilane (APTES), via both silane coupling and carbodiimide chemistry. Physical properties, including tensile strength, Young's modulus, and plateau stress, were measured to verify the effect of internal crosslinking, and the existence of crosslinking was verified by Fourier transform infrared (FT-IR) spectroscopy. The degrees of hair breakage and split ends were evaluated by repeated combing-drying tests. Physical properties of chemically damaged hair were restored by internal crosslinking. Successful crosslinking of APTES via both silane coupling and carbodiimide chemistry was verified by FT-IR spectra. Prevention of breakage and split ends after repeated combing with heat was observed. Human hair can be weakened by chemical damage including perm-processing, so restoring such properties is a major issue in the hair care industry. This work shows that internal crosslinking of damaged hair via chemical conjugation would be a potent method to restore the healthy hair.