New Inorganic Hybrid Systems with Optochemical and Electrochemical Properties

Abstract

New inorganic-inorganic and inorganic-organic hybrid systems with enhanced optochemical and electrochemical properties have been successfully prepared by applying two different kinds of methods such as electrochemical deposition and exfoliation-reassembling reaction. In particular, electrochromic materials such as metal oxides, metal hexacyanoferrates and conducting polymers were electrochemically deposited onto the conducting glass substrates, and each thin film was assembled into full-cell electrochromic devices where each parts were intentionally designed to have proper patterns for desired applications. On the other hand, exfoliated layered metal oxide nanosheets were reassembled with metal oxide nanoparticles to make highly porous inorganic-inorganic nanohybrids. The physicochemical properties of the fabricated hybrid systems could be finely tailored at a molecular level to optimize their applicability as electrochromic devices (ECDs), lithium secondary batteries, and photocatalysts. In chapter 1, an inorganic-inorganic hybrid ECD as an optical iris for lens applications was developed by photolithography and wet etching techniques primarily for fabricating the patterned electrodes, and subsequent electrodeposition of WO₃ and PB, which showed ideally matched charge capacity ratio confirmed by UV spectroscopy and cyclic voltammetry (CV) measurement. It is clearly demonstrated that the patterned WO3-PB ECD could control the optical transmittance simply with 28 %, 51 %, 75 %, and 95 % at 600 nm by applying proper voltage to each of patterns, and was highly stable with only less than 10 % contrast loss even after 5000 times switching. On the other hand, an inorganic-organic hybrid ECD with enhanced optical contrast was also prepared successfully by assembling a PEDOT cathode with controlled thickness and a PB anode. The optimized PEDOT-PB ECD exhibited a noticeable increase in the transmittance change (Δ%T) of 30.8 ~99.3 % at 600 nm. Moreover, according to the circuit analysis, the average response time of electric current for the present ECD was about 420 ms, indicating that such a full cell system could have highly potential applications as fast responding optical devices. Finally in chapter 2, an inorganic-inorganic pillared hybrid material of colloidal manganate nanosheets with titania nanoparticle has been synthesized via exfoliation and reassembling route. X-ray diffraction and cross-sectional transmission electron microscopy (TEM) analyses clearly showed that the titania nanoparticles with a diameter of 1 nm were successfully intercalated into the two dimensional manganate lattice to form highly ordered pillared structure. Moreover, according to the Mn K-edge X-ray adsorption near edge structure (XANES) analysis, the absorption edge energy corresponding to the transitions from the core 1s to unoccupied 3d or 4p states was found to be unchanged, indicating that the electronic structure and local symmetry of Mn ion were maintained even after exfoliation-reassembling reaction.;본 연구에서는 향상된 광화학적, 전기화학적 특성을 갖는 새로운 무기-무기, 무기-유기 하이브리드 시스템을 전기화학증착법과 박리화-재조합법을 통해 개발하였다. 구체적으로, 전기변색물질인 메틸 옥사이드, 메탈 헥사사이아노페레이트, 전도성 고분자 등을 전도성 유리기판에 전기화학증착법으로 박막화시키고, 이를 전극으로 이용하여 무기-무기, 무기-유기 하이브리드 전기변색소자를 제조하였으며, 박리화된 층상무기격자물질을 무기산화물 나노입자와 재조합하여 높은 다공특성을 가지는 무기-무기 나노하이브리드 물질을 개발하였다. 이와 같이 개발된 새로운 하이브리드 시스템은 전기변색소자, 리튬 2차전지 양극물질, 광촉매 등의 특정 반응을 위하여 인위적으로 설계되었으며, 각각의 효율측정 결과, 향상된 물리화학적 특성을 지니고 있음을 확인하였다. 제 1장에서는 포토리소그라피와 습식 식각 기술을 이용하여 패턴 기판을 형성하고, 상호보완적인 산화텅스텐과 프러시안블루를 패턴 기판에 전기층착 방법으로 박막화 하여, 조리개로 응용 가능한 무기-무56기 전기변색소자를 개발하였다. 개발된 소자는 600 nm 영역에서 투과도가 28 %, 51 %, 75 %, 95 %로 조절되었으며, 변색효율이 5000번의 사이클링 이후에도 약 10 % 정도만 감소함을 보여 상당히 안정한 소자임을 증명하였다. 한편, 환원발색형 전도성고분자인 피돗과 상대전극인 프러시안블루 박막을 상호보완적으로 최적화한 후 조립하여 향상된 변색효율과 응답속도를 갖는 유기-무기 하이브리드 전기변색소자 또한 개발하였다. 이는 600 nm 영역에서 약 70 %의 투과도 변화를 보였으며, 약 420 ms의 응답속도를 보였다. 제 2장에서는 박리화된 망간 산화물 콜로이드를 1 나노미터 크기의 이산화티탄 나노졸과 재조합하여 가교화된 무기-무기 나노하이브리드 물질을 개발하였다. X-선 회절분석 및 투과전자현미경 분석을 통해 이산화티탄 나노졸입자가 층상 망간산화물 사이에 균일하게 가교화 되어있음을 확인하였고, X-선 흡수분광법을 통해 박리화-재조합 과정에도 무기물의 결정구조 및 국부구조가 유지됨을 확인하였다.