본 논문에서는 다양한 금속 나노 구조를 형성하고 그 응용을 관찰하였다. 구조의 형성은 첨가제와 전처리 없이 간단한 한 단계의 전기화학적 석출 방법을 이용하였다. 형성된 나노 구조에서의 전기화학적 촉매 활성 및 표면 증강 라만 분광법 (Surface enhanced-Raman spectroscopic, SERS) 활성에 대한 연구를 수행하였다.
첫 번째 연구는, 높은 SERS 활성을 보이는 덴드라이트 금 막대 (Dendritic Au rod, DAR) 나노 구조를 짧은 시간 안에 형성하였다. SERS 기판 형성에 대한 연구는 최근 많은 관심을 받고 있다. 다른 금 나노 구조와 활성을 비교해보면 뾰족한 모서리를 갖는 DAR 이 높은 SERS 활성을 보인다. SERS 증가 인자는 105 보다 크게 나타났으며, rhodamine 6G 의 검출 한계는 10-8 M 이었다.
DAR 은 전극 표면에 균일하고 재현성 있게 형성되며, 장기 안정성이 뛰어나다. 또한 DAR 은 electrochemical SERS 에도 응용이 가능하다는 것을 확인하였다.
두 번째 연구는, 선행 연구에서 보고되지 않은 독특한 삼각형 팔라듐 막대 (Triangular Pd rod, TPR) 나노 구조를 형성하였다. 전자 주사 현미경 (Scanning electron microscopy, SEM), 투과 전자 현미경 (Transmission electron microscopy, TEM) 과 전기화학적 방법을 이용하여 형성된 TPR 의 구조적 특성을 확인하였다. 전구체의 농도와 가해주는 전위를 조절하여 전기화학적 석출 속도를 최적화하였다. TPR 구조는 산소 환원과 메탄올 산화에의 뛰어난 촉매적 활성을 보여주었다. 또한 이 구조는 SERS 기판으로써 재현성 있고 균일한 표면을 형성하였으며, electrochemical SERS 으로서의 응용가능성을 보였다.
마지막으로, 백금 나노 나무 구조를 형성하였다. 형성된 구조는 SEM 을 통해 형태학을 관찰하였다. 백금 나노 나무 구조의 SERS 활성과 표면의 접촉각을 알아보았다. 뾰족한 구조는 높은 SERS 활성을 보였다. 또한, 백금 나노 나무 구조는 전체적으로 균일하며 재현성이 뛰어나다. 나노 나무의 독특한 구조와 화학적 표면 처리는 162° 의 높은 접촉각을 보여 초소수성 기판임을 확인하였다.

In this thesis, the formation of various metal nanostructures and diverse applications of nanostructures are reported. Metal nanostructures were prepared by a simple, fast, and one-step electrodeposition without additives or premodification. Electroanalytical and surface-enhanced Raman spectroscopic (SERS) applications of metal nanostructures are reported.
First, the dendritic gold rod (DAR) structures prepared by electrodeposition in a short time were examined as an effective SERS-active substrate. The fabrication of effective SERS substrates has been the subject of intensive research because of their useful applications. The SERS activity of the DAR surfaces was compared to that of other nanostructured Au surfaces with different morphologies. These investigations revealed that highly faceted sharp edge sites on the DAR surfaces play a critical role in inducing a high SERS activity. The SERS enhancement factor was estimated to be greater than 105, and the detection limit of rhodamine 6G at DAR surfaces was 10-8 M. The DAR surfaces exhibit excellent spot-to-spot and substrate-to-substrate SERS enhancement reproducibility, and their long-term stability is very good. It was also demonstrated that the DAR surfaces can be effectively utilized in electrochemical SERS systems.
Second, unique triangular Pd rod (TPR) nanostructures were prepared by a simple one-step electrodeposition. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical techniques were utilized to characterize the structural features of the TPR nanostructures. The precursor concentration and applied potential optimized the electrodeposition rate. The TPR structures exhibited electrocatalytic activities for oxygen reduction and methanol oxidation reactions. These surfaces could be effectively utilized as reproducible SERS-active substrates to produce stable SERS signals for an electrochemical system.
Finally, we fabricated Pt nanotree structures. The morphologies of these nanostructures were observed by SEM. We show that the surface morphology determines the observed contact angle and SERS activities. The sharp sites play a critical role in inducing a high SERS activity. In addition, Pt nanotree structures exhibit excellent uniformity and reproducibility. The unique structure of Pt nanotrees and chemical surface premodification results in a contact angle larger than 160°, so Pt nanotrees can be considered to be superhydrophobic substrates.

• Chapter 1. Introduction 1
• 1.1 Metal Nanostructures 2
• 1.2 Electrochemical Deposition 2
• 1.3 Fuel Cell 4
• 1.3.1 Reduction: Oxygen 5
• 1.3.2 Oxidation: Formic acid and Methanol 6
• 1.4 Surface-enhanced Raman Scattering 6
• 1.5 Specific Aims 7
• 1.6 References 8
• Chapter 2. Highly Reproducible SERS-active Au Nanostructures Prepared by Simple Electrodeposition: Origin of SERS Activity and Applications as Electrochemical Substrates 12
• 2.1 Introduction 13
• 2.2 Experimental Procedures 15
• 2.2.1 Reagents 15
• 2.2.2 Instruments 16
• 2.2.3 SERS Substrate Fabrication 16
• 2.2.4 SERS Substrate Preparation 17
• 2.3 Results and Discussion 18
• 2.3.1 Comparison of SERS Activity of DAR to other Nanostructured Au with Different Morphologies 18
• 2.3.2 Origin of SERS Activity of DAR 24
• 2.3.3 Evaluation of SERS Enhancement Factor (EF) 31
• 2.3.3.1 SERS Substrate EF (SSEF) 31
• 2.3.3.2 Analytical EF 34
• 2.3.4 Reproducibility and Stability of DAR as a SERS Substrate 34
• 2.3.5 Application of DAR to Electrochemical SERS Systems 41
• 2.4 Conclusion 44
• 2.5 References 46
• Chapter 3. Electrodeposition of Triangular Pd Rod Nanostructured and Their Electrocatalytic and SERS Activities 50
• 3.1 Introduction 51
• 3.2 Experimental Procedures 53
• 3.3 Results and Discussion 54
• 3.3.1 Electrochemical Deposition of Pd Nanostructures 54
• 3.3.2 Electrocatalytic Activity 68
• 3.3.2.1 Characterization of Triangular Pd Rod 68
• 3.3.2.2 Oxygen Reduction Reaction 72
• 3.3.2.3 Methanol and Formic Acid Oxidation 75
• 3.3.3 SERS Activity 75
• 3.4 Conclusion 82
• 3.5 References 84
• Chapter 4. Shape-controlled Pt Nanostructures Prepared by Electrodeposition: Their Superhydrophobicity and SERS Activity 88
• 4.1 Introduction 89
• 4.2 Experimental Procedures 90
• 4.3 Results and Discussion 92
• 4.3.1 Electrochemical Deposition of Pt Nanostructures 92
• 4.3.2 Characterization of Pt Nanostructures 96
• 4.3.3 Superhydrophobicity 96
• 4.3.4 SERS Activity of Pt Nanostructures 100
• 4.3.5 Applications of Pt nanotree for Electrochemical Systems 103
• 4.4 Conclusion 107
• 4.5 References 107
• Appendix. Electrocatalysis of Oxygen Reduction on Nanomaterials 109
• A.1 Introduction 110
• A.2 Experimental Procedures 111
• A.2.1 Reagents and Instruments for the Electrochemical Study 111
• A.2.2 Electrode Preparation 112
• A.2.2.1 Ligand-free Pt-on-Au Nanodendrites (Lf-PtND) 112
• A.2.2.2 Pt/Mn3O4 Nanocomposite (PtMONC) 112
• A.2.3 Electrochemical Measurements 113
• A.3 Results and Discussion 114
• A.3.1 Evaluation of Electrocatalytic Activities of Lf-PtND Catalysts toward ORR 114
• A.3.2 Evaluation of Electrocatalytic Performance of PtMONC Nanocomposites 120
• A.4 Summary 132
• A.5 References 132
• List of Publications 135
• Acknowledgments 138