흑연으로부터 박리된 그래핀 나노재료의 제조와 응용

학위논문 (박사)-- 서울대학교 대학원 : 화학생물공학부, 2013. 2. 장정식.Graphene nanomaterials are fabricated by chemical exfoliation from graphite. In particular, one-dimensional fibrous graphene oxide is obtained by ice-templating of graphene oxide solution, and is reduced by vapor phase reduction without any morphological changes. When the atmospheric Ar plasma is introduced to the one-dimensional graphene oxide, it is also possible to reduce the one-dimensional graphene oxide in less than 10 seconds without toxic reducing agents. The graphene model for dissipative particle dynamics is proposed by adding additional forces between graphene beads, and is calibrated by structural characteristics analysis. The self-assembly phenomenon between graphene model and surfactants in aqueous solution is analyzed by dissipative particle dynamics. The self-assembly phenomena of a graphene nanosheet in SDS surfactant solution is predicted, and diverse self-assemblies of graphene/surfactants are also predicted with concentration of surfactants. Graphene/copper(II) oxide nanocomposite is synthesized using exfoliated graphene oxide by aqueous-phase chemical method. The synthesized CuO had an urchin-like shape densely composed of nano-needles, and the synthesized nanocomposites presented excellent antibacterial performance against both Gram-positive and Gram-negative bacteria. In addition, graphene oxide solution is reduced without reducing agents by mechanical mixing with high speed. It is possible to reduce in diverse solvents, and the product shows high dispersion stability. Reduced graphene oxide solution based ethylene glycol is applied to nanofluids, and the thermal conductivity of the nanofluid with 1 wt% has increased 16.4% compared to that of base fluid.Abstract i List of Abbreviations iii List of Figures v List of Tables xiii Contents xiv Chapter 1 Introduction 1 1.1 Background 1 1.1.1 Graphene 1 1.1.1.1 General properties of graphene 1 1.1.1.2 Synthetic methods of graphene 3 1.1.1.3 Graphene oxide 5 1.1.1.4 Reduction of graphene oxide 7 1.1.2 Coarse grained molecular dynamics 9 1.1.2.1 Dissipative particle dynamics 9 1.1.2.2 Carbon nanomaterials in molecular dynamics 11 1.1.3 Application fields 13 1.1.3.1 Antimicrobial nanomaterials 13 1.1.3.2 Nanofluids 15 1.2 Objectives and Outline of the study 18 1.2.1 Objectives 18 1.2.2 Outline 18 Chapter 2 Experimental Details 24 2.1 Facile synthesis of one-dimensional graphene network 24 2.1.1 Fabrication of one-dimensional graphene network 24 2.1.2 Reduction of graphene oxide network via argon plasma 26 2.2 Coarse grained molecular dynamics for graphene/surfactant nanostructure 28 2.2.1 Coarse grained graphene model for dissipative particle dynamics 28 2.2.2 Self-assembly phenomenon between graphene and surfactant by dissipative particle dynamics simulation 32 2.3 CuO/graphene nanocomposite as an antimicrobial nanomaterial 34 2.3.1 Fabrication of CuO/graphene nanocomposite 34 2.3.2 Antimicrobial properties of CuO/graphene nanocomposite 36 2.4 Graphene-based nanofluid for enhancement of thermal conductivity 38 2.4.1 Fabrication of mechanical reduced graphene oxide using nanodispersion technique 38 2.4.2 Enhancement of thermal conductivity for the graphene-based nanofluid 40 Chapter 3 Results and Discussion 41 3.1 Facile synthesis of one-dimensional graphene network 41 3.1.1 Fabrication of one-dimensional graphene network 41 3.1.2 Reduction of graphene oxide network via argon plasma 50 3.2 Coarse grained molecular dynamics for graphene/surfactant nanostructure 67 3.2.1 Coarse grained graphene model for dissipative particle dynamics 67 3.2.2 Self-assembly phenomenon between graphene and surfactant by dissipative particle dynamics simulation 83 3.3 CuO/graphene nanocomposite as an antimicrobial nanomaterial 98 3.3.1 Fabrication of CuO/graphene nanocomposite 98 3.3.2 Antimicrobial properties of CuO/graphene nanocomposite 115 3.4 Graphene-based nanofluid for enhancement of thermal conductivity 121 3.4.1 Fabrication of mechanical reduced graphene oxide using nanodispersion technique 121 3.4.2 Enhancement of thermal conductivity for the graphene-based nanofluid 130 Chapter 4 Conclusions 137 References 141 국문초록 149Docto

Theoretical Study on Enhancement of Sensing Capability of Plasmonic Dimer Au Nanoparticles with Amphiphilic Polymer Brushes

Au nanoparticle (Au-NP) sensors need a high surface plasmon resonance intensity and a low steric effect for efficient labeling in sensors. Since dimers meet these requirements,we have theoretically studied the self-assembly of monomer and dimer Au-NPs by considering influential factors such as Au-NP size, polymer thickness, and gap distancebetween dimer Au-NPs. In order to control the monomerization and dimerization of spherical Au-NPs and their sizes via self-assembly, two polymers (hydrophilic PEG and hydrophobic PMMA) were grafted on the Au-NPs as amphiphilic brushes. Computational methods of dissipative particle dynamics and discrete dipole approximation were employed for virtual selfassembly and theoretical analyses of plasmons related to sensing properties, respectively. We found that the bigger Au-NPs were obtained when the amounts of each polymer were roughly identical and the gap distance between Au-NPs in the dimer was shorter when the amount of PMMA was reduced within the condition of dimerization. This theoretical study revealed an optimal near-contact distance for Au-NPs@PMMA/PEG, where the electron tunneling effect was minimized, and reported unseen roles of polymers and plasmons, which consequently allowed achieving a highly efficient Au-NP dimer senso