Solution Growth and Characterization of Layered Nanostructured Materials Towards Electrochemical and Light Emitting Applications

Dang, Lianna C ProQuest Dissertations & Theses The University of 2019 해외박사(DDOD)

Layered materials held together with weak interactions are interesting for the fundamental properties, not limited to anisotropic charge transport and energy transfer, structural tunability, and providing material building blocks for fundamental studies of crystal growth. Instead of the more traditional layered materials held together by van der Waals interactions, I focus on layered materials where the out-of-plane direction relies on Coulombic interactions. This dissertation focuses on the crystal growth of these materials from solution-based methods and ion exchange of the interlayer. I study two model systems: layered double hydroxides (LDHs) and Ruddlesden-Popper (R-P) lead halide perovskites, where the out-of-plane interactions are Coulombic and the host inorganic layers require interlayer ions of opposite charge. Firstly, I discuss the hydrothermal-based syntheses available in the laboratory at moderate and higher temperatures to prepare well-defined LDHs developed in several collaborations, driven by either crystal growth studies or applications in electrochemical oxidations. Within the LDHs, the gallery anions have been considered unreactive and inconsequential to their alkaline water oxidation activity under ambient conditions. I developed new hydrothermal methods to directly synthesize NiFe LDH materials containing non-carbonate anions. Although the different anions do not typically affect the electrocatalytic activity, dodecyl sulfate (incorporated by anion exchange) enhances the activity of the resulting LDH catalysts, even if it is not maintained within the galleries over time in the relevant electrolyte under ambient conditions. For the R-P lead halide perovskites, I first developed a method for observing real-time dislocation-driven growth of these materials at the air-liquid interfaces of precursor droplets. The asymmetric dislocation defects introduce asymmetry at the single-object level, allowing for the observation of circularly polarized photoluminescence. The degree of polarization observed at room temperature is greater than analogous materials synthesized with chiral directing ligands. This provides an alternative strategy to induce chirality and polarized emission from optical materials. Next, I developed a strategy of interconversion between R-P lead halide perovskites with various A’ cations at room temperature. Because the inorganic layers are not completely maintained in these conversions, a dissolution recrystallization mechanism is proposed as a likely pathway, rather than ion exchange analogous to the LDH family of materials. Together, these studies provide a platform for understanding fundamental crystal growth of dislocation-prone 2D materials, and some insights into tuning their properties and applications by interlayer or gallery tuning and by dislocation-driven growth.

Enhancing light-extraction efficiency of OLEDs with high- and low-refractive index organic-inorganic hybrid materials : 고굴절 및 저굴절 유-무기 복합재료를 이용한 OLED 외광추출효율 향상

김기한 경북대학교 대학원 2016 국내석사

High- and low-refractive-index hybrid materials were prepared by an in situ acid-free sol–gel process for internal and external light-extraction layers in organic light-emitting diodes (OLEDs). A random copolymer of methyl methacrylate (MMA) and 3-(trimethoxysilyl) propyl methacrylate (MSMA), poly(MMA-co-MSMA), which was capped with trialkoxysilane in MSMA units, was used as a precursor. The precursor was further reacted with titanium(IV) isopropoxide (TTIP) and tetraethyl orthosilicate (TEOS) to synthesize the high- and low-refractive-index hybrid materials, respectively, in which TiO2 and SiO2 nanoparticles were well dispersed, respectively, in the polymer matrix. After the reactions with TTIP and TEOS, the refractive index increased to 1.81 and decreased to 1.44 from 1.50 of the precursor, respectively. The luminance, power, and current efficiency of the OLED with an external light-extraction layer were enhanced by 21.3, 28.6, and 29.1 %, respectively, and those of the OLED with an internal light-extraction layer were increased by 62.4, 76.9, and 59.2 %, respectively, when compared to values for the reference OLED without an internal or external light-extraction layer. These results indicate that high- and low-refractive-index materials are desirable for enhancement in light-extraction efficiency, and they can provide practical solutions for various applications such as OLED displays and lighting.

New Materials for the Immobilization, Generation, and Characterization of Reactive Intermediates

Ezazi, Andrew A Texas A&M University ProQuest Dissertations & Thes 2023 해외박사(DDOD)

Reactive intermediates invoked in the functionalization of strong C-H bonds are difficult to characterize. The high energy required to break C-H bonds often means the lifetime of the intermediates is fleeting due to opportunities to engage in undesired reactivity. One method of suppressing undesired reactivity pathways is to immobilize the reactive intermediate in a solid. While doing so may result in longer-lived intermediates, ensconcing a molecule in a material introduces other issues, namely several homogeneous characterization methods are unavailable in the context of heterogeneous materials.This dissertation will present efforts to develop new materials to immobilize and characterize reactive nitride intermediates. The first chapter discusses strategies to synthesize Metal-Organic Frameworks (MOFs) based on kinetically inert ions. In the second chapter, we leverage the metalloligand strategy advanced in the first chapter to synthesize new MOFs based on Ru2 paddlewheel molecules, which we hope will serve as platforms to interrogate nitrogen atom transfer in confined environments. The third chapter discusses the synthesis of optically transparent thin films of Ru2 paddlewheel molecules, their photochemistry, and attempts at apical ligand metathesis to introduce photoprecursor groups. The fourth chapter builds upon the synthesis of porous, optically transparent thin films demonstrated in the third chapter, but instead with porphyrin molecules. We explored the growth mechanism of our polyelectrolyte films and explore solid-state photochemistry of our films. The final chapter presents a prospectus of future film targets for solid-state photochemistry.

Synthesis and application of inorganic functional adsorbents and polymer composites for anionic contaminant removal from water

김재현 서울대학교 대학원 2017 국내박사

This thesis deals with the synthesis, characterization, and application of an inorganic functional materials as adsorbents for phosphorous, chromium, and fluorine removal from aqueous solutions. The inorganic functional materials presented in this study include iron oxide nanoparticle-chitosan composite, triamine-functionalized mesoporous silica-polymer composite, calcined Mg-Fe layered double hydroxide-PVDF/PVA composite, and quintinite. Iron oxide nanoparticle(ION)-chitosan composites were prepared using acidified chitosan, an environmentally friendly polymer, suspension to blend iron oxide nanoparticles by a cross-linking method. The removal of phosphate by ION-chitosan composites was verified by batch experiments, column experiments and pilot-scale adsorption tower experiment. The adsorption properties were analyzed and quantified using kinetic and equilibrium models and thermodynamic analysis. ION-chitosan composites successfully removed phosphate from aqueous solution and showed good reversibility, multicycle stability. It is a good candidate for environmentally friendly inorganic composites as adsorbents. The characterization of triamine-functionalized mesoporous silica-polymer composites for Cr(VI) removal was also studied. The mesoporous material with various amounts of functional group had high surface area. The kinetics of the functionalized mesoporous silica were found to be sufficiently fast and it was observed that maximum sorption capacity was 330.88 mg/g. The composites showed good performance of chromate removal from real industrial wastewater. The calcined Mg-Fe layered double hydroxide(LDH) was prepared through a co-precipitation and calcination at 300 oC. The calcined LDH could be used repeatedly for phosphate removal through desorption with 0.1 M NaOH solution. MgFe calcined LDH-PVDF/PVA composites also could be used for phosphate removal from aqueous solutions with regeneration and repeated use. The phosphate removal was relatively constant at an acidic and alkaline pHs. Quintinite was applied as adsorbents for removal of phosphate and fluoride. The maximum phosphate adsorption capacity was 4.77 mgP/g. The phosphate adsorption to quintinite was not varied at pH 3.0 – 7.1 (1.50 –1.55 mgP/g) but decreased considerably at a highly alkaline solution (0.70 mgP/g at pH 11.0). Experimental results showed that the maximum adsorption capacity of fluoride to quintinite was 7.71 mg/g. The adsorption of fluoride to quintinite was not changed at pH 5 – 9 but decreased considerably at the highly acidic (pH < 3) and alkaline (pH > 11) solution conditions. Therefore, this study elucidated that the inorganic functional materials removed phosphorous, chromium, and fluorine from aqueous solutions, effectively. These results also demonstrate that the functional polymer composites developed in this study can be applied to water treatment system.

(A) Novel Synthetic Route for the Layered Zinc Hydroxide Nitrate by Electron Beam Irradiation and Synthesis and Characterization of Various Shaped Gold Nanostructures

배효선 동국대학교 2012 국내석사

In chapter &#1030;, we developed a novel and eco-friendly synthetic route for the preparation of two-dimensional layered zinc hydroxide with intercalated nitrate anions. The layered zinc hydroxide nitrate which is called ‘zinc basic salt’ in general was successfully synthesized using electron beam irradiation technique. The 2-propanol solutions containing hydrated zinc nitrate were directly irradiated with an electron-beam radiation at room temperature under atmospheric condition without any stabilizer or base molecules. Under electron beam irradiation, the reactive radicals such as hydrated electron (eaq-), H&#8729; and OH&#8729; were generated by radiolysis of water molecule in precursor. The strong reductive radical species, eaq- and H&#8729;, were quickly scavenged by oxygen to produce relatively lower reactive radicals such as O2- and HO2. On the other hand, OH&#8729;, oxidative radical, was scavenged by 2-propanol. During these complex reactions, the hydroxyl anions might be formed from these reactive radicals. After reaction of the precursor zinc ion and hydroxyl anions, the Zn5(OH)8(NO3)2&#8729;2H2O was precipitated. Structure and morphology of obtained compounds were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). The chemical components of products were determined by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA). The thermal behavior of products was studied by thermogravimetric (TG) and differential thermal analysis (DTA). In chapter II, we successfully synthesized various shaped gold nanostructures which have a controlled ‘Surface plasmon resononance’ property. Gold nanostructures prepared in this study are ultimately intend to photo-thermal therapy of cancer cells remained after surgery to remove the thyroid cancer. In varied shaped gold nanostructures, we prepared gold nanoshell and gold nanorod, of which absorption wavelength is controlled to about 760 nm. To synthesize various shaped gold nanostructures, seed-mediated growth method is used generally. Gold seed nanoparticles of which size is about 2 ~ 4 nm were prepared first and further gold ion source was reduced in solution containing gold seed particles by reducing agent such as formaldehyde, sodium borohydride and ascorbic acid. The particle size of gold nanoshell synthesized in here is about 140 nm and the thickness of gold shell is about 19 nm. And the size of gold nanorod which has the controlled absorption property is about 40 nm in length and its aspect ratio is 2.9. The size and morphology of varied gold nanostructures were analyzed by high resolution-transmission electron microscopy (HR-TEM) and field emission-scanning electron microscopy (FE-SEM). The optical properties of the gold nanoshells and nanorods were analyzed by ultraviolet-visible spectroscopy (UV). The elemental composition of gold nanoshell was characterized by fourier transform infrared spectroscopy (FT-IR), thermogravimetry-differential thermal analysis (TG-DTA) and energy dispersive spectrometry (EDS). Zeta-potential measurement was also performed to check the surface charge transition during the preparation of gold nanoshell. Chapter I은 질산 이온이 층간에 삽입된 이차원 층상형의 아연 수산화염을 합성하기 위한 새롭고 친환경적인 합성 방법의 개발에 대한 연구이다. 층상형의 아연 수산화염은 일반적으로 “zinc basic salts”라고 불리는 물질로 본 연구에서는 전자빔의 조사를 통하여 성공적으로 합성할 수 있었다. 본 연구에서 고안된 합성 방법은 수화된 아연 질산염을 2-프로판올에 녹인 용액을 상온, 상압의 조건하에서 어떠한 염기나 안정제의 첨가 없이, 직접 전자빔을 조사하게 된다. 전자빔의 조사 과정에서, 수화된 전자 (eaq-), H&#8729; 또는 OH&#8729;과 같은 활성 라디칼이 전구체 염에 포함된 물 분자의 방사분해에 의해 형성된다. eaq-이나 H&#8729;과 같은 강한 환원성 라디칼들은 산소에 의해 O2- 또는 HO2 형태의 상대적으로 낮은 활성 라디칼을 생성하며 빠르게 사라진다. 반면, OH&#8729;과 같은 산화형 라디칼은 용매인 2-프로판올에 의해 사라지게 되는데, 이러한 복잡한 반응이 일어나는 동안에 아마도 활성 라디칼들로부터 수산화 이온이 형성될 것이다. 전구체 아연 이온과 수산화 이온의 반응 후엔 Zn5(OH)8(NO3)2&#8729;2H2O의 화학식을 갖는 층상형 아연 수산화염이 침전된다. 생성물의 구조와 형태에 대한 특성 분석은 분말 엑스레이 회절분석법, 주사 현미경, 고성능 투과 전자 현미경을 이용하여 수행되었고, 생성물의 화학적 구성물에 대한 분석은 적외선 분광법 및 원소 분석을 이용하여 수행하였다. 또한 생성물의 열적 특성은 열중량 분석법과 시차 열분석법을 이용하여 분석하였다. Chapter II에서는 갑상선 수술 후 잔여 암세포의 광열치료 (photo-thermal therapy)를 궁극적인 목적으로 하여, 표면 플라즈몬 공명 (surface plasmon resonance) 특성을 조절한 다양한 형태의 금 나노입자를 합성하였다. 표면 플라즈몬 공명 특성은 입자의 모양이나 크기에 따라 최대 흡수 파장을 조절할 수 있는 특성을 갖는데 이러한 특성은 입자의 크기보다는 모양, 즉 입자의 aspect ratio에 따라 더욱 뚜렷하게 변화한다. 본 연구에서는 다양한 형태의 금 나노입자 중에서도 근적외선 영역에서 최대 흡수파장을 갖는 금 나노쉘과 금 나노막대를 합성하였다. 금 나노쉘은 유전상수가 큰 핵 입자 (본 연구에서는 실리카 나노입자를 사용)를 금 껍질로 둘러싼 형태로 핵 입자와 금 껍질의 두께를 조절함으로써 표면 플라즈몬 공명 특성을 조절 할 수 있게 된다. 또한 금 나노막대의 경우엔 불순물로 첨가해 주는 AgNO3의 함량 조절을 통하여 쉽게 입자의 aspect ratio를 조절할 수 있다. 이러한 금 나노입자를 합성하는데에는 일반적으로 시드 매개 성장 (seed-mediated growth) 방법이 사용된다. 이 방법은 약 2 ~ 4 nm의 크기를 갖는 금 시드 입자를 먼저 합성하고 이러한 시드를 첨가한 용액 상에서 포름알데히드나 소듐 보로하이드라이드, 아스코빅산과 같은 환원제를 이용하여 더 첨가한 금 이온을 환원시키게 된다. 이 연구에서 합성한 금 나노쉘은 약 140 nm의 크기로 금 껍질의 두께는 약 19 nm이다. 또한 금 나노막대의 경우엔 그 크기가 약 40 nm이고 이것의 aspect ratio는 약 2.9로 나타났다. 다양한 형태의 금 나노입자의 크기와 형태는 고분해능 투과 전자현미경 (HR-TEM)과 전계 방출 주사 전자현미경 (FE-SEM)을 통해 분석하였다. 금 나노쉘과 나노 막대의 광학적 특성은 자외선-가시광선 분광기를 통해 분석하였다. 금 나노쉘의 경우, 입자의 구성요소에 대한 분석을 적외선 분광법과 열중량-시차열 분석법 (TG-DTA), 에너지분산 분광분석법 (EDS)을 통하여 수행하였고 금 나노쉘을 합성하는 각 단계에서 일어나는 표면 전하는 제타-전위 (Zeta-potential) 측정을 통해 확인하였다.

Bio-inorganic and inorganic-inorganic nanohybrids via nanospace modification of 2D inorganic compounds

양재훈 서울大學校 大學院 2005 국내박사

Cone-shaped dendrimer molecular layer for analysis of protein-ligand interaction

최영서 Pohang Univ. of Science & Technology 2004 국내박사