Synthesis of monodisperse noble metal nanoparticles

SYNTHESIS OF MONODISPERSE NOBLE METAL NANOPARTICLES ZHANG QINGBO NATIONAL UNIVERSITY OF SINGAPORE 2008 SYNTHESIS OF MONODISPERSE NOBLE METAL NANOPARTICLES ZHANG QINGBO (M. Eng., Tianjin University) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMICAL & BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2008 ACKNOWLEDGEMENTS I would like to express my greatest appreciation to my supervisor, Prof. Lee Jim Yang for his support and guidance throughout the course of this project. He has imparted in me the skill of creative problem solving, the scientific rigor in critiquing experimental results from a myriad of angles, objectivity and optimism that transform apparent problems into new discoveries and opportunities. These skill sets have enabled me to establish the overall direction of the research and to identify the niche areas for more in-depth investigations. I had the great luck to work with a group of wonderful and delightful colleagues in the laboratory, in particular, Dr. Xie Jianping, Dr. Yang Jun, Dr. Yang Jian, Dr. Pong Boon Kin, Dr. Tan Yen Nee, Dr. Zeng Jianhuang, Mr. Yang Jinhua, Mr. Deng Da and Ms. Yu Yue. I thank them for their valuable suggestions and stimulating discussions. I also thank Dr. Zhang Jixuan in Department of Materials Science and Engineering and Dr. Chris Boothroyd in Institute of Materials Research Engineering for their helpful suggestions on TEM measurement. I am indebted to the technical staff in the department, especially Mr. Boey Kok Hong, Ms Lee Chai Keng, Mr. Chia Phai Ann, Mr. Shang Zhenhua, Mr. Mao Ning and Dr. Yuan Zeliang. Their superb technical support and services are essential for the completion of this study. I I acknowledge the generosity of the National University of Singapore for providing the research scholarship throughout my Ph.D candidature. Finally, I would like to show my deepest gratitude to my family. Without their encouragement and understanding, this work could not have been completed successfully. II TABLE OF CONTENTS ACKNOWLEDGEMENTS . I TABLE OF CONTENTS III SUMMARY .VII LIST OF TABLES IX LIST OF FIGURES . X LIST OF SCHEMES . XVII LIST OF ABBREVIATIONS XVIII CHAPTER INTRODUCTION 1.1 Background . 1.2 Top-down and bottom-up approaches 1.3 Problem definitions . 1.4 Objectives and scope . CHAPTER LITERATURE REVIEW . 2.1 Fundamentals of formation of monodisperse nanoparticles . 2.1.1 Nucleation 10 2.1.2 Growth . 13 2.1.3 Oswald ripening . 14 2.2 Syntheses of monometallic Ag and Au nanoparticles 15 2.3 Syntheses of Ag-Au bimetallic nanoparticles . 23 2.3.1 Alloy nanoparticles 23 2.3.2 Core-shell nanoparticles . 27 2.3.3 Hollow nanoparticles . 28 2.4 Size sorting of nanoparticles . 29 CHAPTER TUNING THE CRYSTALLINITY OF GOLD NANOPARTICLES 32 3.1 Introduction . 32 3.2 Experimental section . 33 3.2.1 Synthesis of Au nanoparticles 33 3.2.2 Materials characterizations 34 3.3 Results and discussion 35 3.3.1 Synthesis and characterization of Au nanoparticles 35 3.3.1.1 Single-crystalline nanoparticles 35 3.3.1.2 Decahedral MTPs 37 3.3.1.3 Icosahedral MTPs . 39 3.3.2 Influence of the synthesis conditions on the Au nanoparticle crystallinity . 39 III 3.3.3 Formation mechanism of Au nanoparticles with different crystallinity 44 3.4 Conclusion 46 CHAPTER MONODISPERSE ICOSAHEDRAL SILVER, GOLD AND PALLADIUM NANOPARTICLES: SIZE CONTROL STRAGETY AND SUPERLATTICE FORMATION . 48 4.1 Introduction . 48 4.2 Experimental section: 50 4.2.1 Preparation of polydisperse Ag icosahedral nanoparticles 50 4.2.2 Narrowing the size distribution of Ag icosahedral nanoparticles 51 4.2.3 Preparation of monodisperse Au and Pd icosahedral nanoparticles 51 4.2.4 Manipulating the size of the icosahedral nanoparticles . 52 4.2.5 Materials characterizations 52 4.3. Results and discussion . 53 4.3.1 Synthesis of icosahedral Ag nanoparticles 53 4.3.2 Narrowing the size distribution of icosahedral Ag nanoparticles 59 4.3.3 Synthesis of monodisperse Au and Pd icosahedral nanoparticles . 61 4.3.4 Size Manipulation of monodisperse icosahedral nanoparticles . 65 4.3.5 Self-assembly of monodisperse icosahedral nanoparticles 66 4.4 Conclusions . 69 CHAPTER SIZE AND COMPOSITION TUNABLE HYDROPHILIC SILVER-GOLD ALLOY NANOPARTICLES BY REPLACEMENT REACTIONS . 70 5.1 Introduction . 70 5.2 Experimental Section 72 5.2.1 Synthesis of Ag nanoparticles 72 5.2.2 Synthesis of Ag-Au alloy nanoparticles 73 5.2.3 Materials characterizations 73 5.3 Results and Discussion . 74 5.3.1 Synthesis and characterization of Ag nanoparticles 76 5.3.2 Synthesis and characterization of Ag-Au alloy nanoparticles . 76 5.3.3 Formation mechanism of the homogeneous Ag-Au alloy nanoparticles. 82 5.4 Conclusion 87 CHAPTER SYNTHESIS OF MONODISPERSE HYDROPHOBIC SILVER-GOLD ALLOY NANOPARTICLES WITH INDEPENDENTLY TUNABLE MORPHOLOGY, COMPOSITION, SIZE AND SURFACE CHEMISTRY AND THEIR 3-D SUPERLATTICES . 89 6.1 Introduction . 89 6.2 Experimental section . 90 6.2.1 Synthesis of single-crystalline TO Ag nanoparticles . 90 6.2.2 Synthesis of icosahedral Ag MTPs 90 6.2.3 Narrowing the size distribution of Ag nanoparticles . 91 6.2.4 Tuning the size of single-crystalline TO Ag nanoparticles . 91 6.2.5 Synthesis of Ag-Au alloy nanoparticles 92 6.3 Results and discussion 94 IV 6.3.1 Synthesis of monodisperse Ag nanoparticles with different sizes and morphologies . 95 6.3.1.1 Synthesis of polydisperse single-crystalline TO Ag nanoparticles and icosahedral Ag MTPs . 95 6.3.1.2 Narrowing the size distributions of Ag nanoparticles . 97 6.3.1.3 Enlargement of the size of single-crystalline TO Ag nanoparticles . 102 6.3.2 Synthesis of Ag-Au alloy nanoparticles with independently tunable morphology, composition, size and surface chemistry . 102 6.3.2.1 Synthesis of Ag-Au alloy nanoparticles with different morphologies . 103 6.3.2.2 Synthesis of single-crystalline TO Ag-Au alloy nanoparticles with the same size but different compositions 106 6.3.2.3 Synthesis of Ag-Au alloy nanoparticles with different sizes but the same composition 109 6.3.2.4 Synthesis of Ag-Au alloy nanoparticles with different surface chemistry . 111 6.3.3 Self-assembly of Ag-Au alloy nanoparticles to 3-D superlattices . 114 6.3.3.1 Superlattices of single-crystalline Ag-Au alloy nanoparticles 115 6.3.3.2 Superlattices of icosahedral Ag-Au alloy MTPs 118 6.4 Conclusion 119 CHAPTER SYNTHESIS OF Ag@AgAu METAL CORE-ALLOY SHELL BIMETALLIC NANOPARTICLES WITH TUNABLE SHELL COMPOSITIONS BY THE GALVANIC REPLACEMENT REACTION 121 7. 1. Introduction . 121 7.2. Experimental section 123 7.2.1 Synthesis of Ag nanoparticles 123 7.2.2 Phase transfer of Ag nanoparticles and HAuCl4 124 7.2.3 Replacement reaction . 124 7.2.4 Materials characterizations 125 7.3 Results and discussion 125 7.3.1 Synthesis and characterization of Ag nanoparticles 125 7.3.2 Synthesis and characterization of Ag@AgAu metal core-alloy shell nanoparticles . 126 7.3.3 Formation mechanism of the Ag@AuAu core-shell nanoparticles . 130 7.3.3.1 Microscopic study . 131 7.3.3.2 Spectroscopic study 137 7.4 Conclusion 140 CHAPTER SIZE SORTING OF ELECTROSTATICALLY STABILIZED SILVER NANOPARTICLES 142 8.1 Introduction . 142 8.2 Experimental section . 143 8.2.1 Materials and instrumentations 143 8.2.2 Preparation of polydisperse MBSA-protected Ag nanoparticles . 144 8.2.3 Size sorting of Ag nanoparticles 145 V 8.3 Results and discussion 147 8.3.1 Preparation of MBSA-protected Ag nanoparticles 147 8.3.2 Size sorting of Ag nanoparticles 147 8.3.3 Mechanism of nanoparticle size sorting 150 8.4 Conclusion 152 CHAPTER CONCLUSIONS AND RECOMMENDATIONS . 153 9.1 Conclusions . 153 9.2 Suggestions for future work 159 REFERENCES . 162 PUBLICATIONS 178 VI SUMMARY Preparation of monodisperse nanoparticles on a large quantity is important for identifying the properties of the nanoparticles without ambiguity and for beseeching reliable application performance. This thesis work therefore focuses on developing new preparation methods to produce monodisperse noble metal nanoparticles with controllable morphology, size, surface chemistry, composition and composition distribution within each particle. Several types of zero-dimensional Ag, Au and Pd monometallic nanoparticles and Ag-Au bimetallic nanoparticles as well as their 3-D superlattices were fabricated. A kinetic control strategy was adopted to vary the crystallinity of monometallic Au nanoparticles formed by polyol synthesis. Single-crystalline nanoparticles, decahedral multiply twinned particles (MTPs) as icosahedral MTPs were all obtainable by simply adjusting the HAuCl4 concentration while keeping other environmental factors fixed. This kinetic control strategy was then combined with digestive ripening to produce highly monodisperse Ag icosahedral MTPs. These Ag icosahedral MTPs were useful as seeds in replacement reactions with Au and Pd precursors to form monodisperse Au and Pd icosahedral MTPs. The size of Ag, Au and Pd icosahedral MTPs could be varied without changes in their morphology and size distribution by fine tuning the conditions of seedmediated growth. The as-synthesized Ag, Au and Pd icosahedral MTPs could easily selfassemble into 3-D superlattices with long-range order because of their similarity in size and shape. VII Ag-Au bimetallic nanopartaicles with homogeneous alloy structure and heterogeneous Ag@AgAu metal core-alloy shell structure were synthesized by the replacement reaction between Ag nanoparticles and HAuCl4. The structure of the final product from the replacement reaction depended on the functional attributes of the starting Ag nanoparticles as well as the reaction conditions. The synthesis of Ag-Au alloy nanoparticles was then improved by a stepwise procedure consisting of reduction of Ag ions, digestive ripening, seed-mediated growth and replacement reaction to produce highly monodisperse alloy nanoparticles with independently tunable morphology, composition, size and surface chemistry. Both truncated octahedral single-crystalline and icosahedral multiply twinned Ag-Au alloy nanoparticles were obtained by this procedure. Both of them could self-assemble into 3-D superlattices. The packing pattern of the nanoparticles comprising the superlattices was dependent on the morphology of the nanoparticles. A simple methodology based on double-layer compression was also used to sort electrostatically-stabilized nanoparticles by size, using Ag nanoparticles as an example. By progressively changing the ionic strength in the aqueous nanoparticle solution, Ag nanoparticles could be sorted into several fractions by size with small size variations in each “cut”. 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Journal of the American Chemical Society, 2006. 128(36): p. 11921-11926. 179 [...]... distribution 2.2 Syntheses of monometallic Ag and Au nanoparticles There are a large number of publications on the synthesis of Au and Ag nanoparticles Most of the synthesis methods for Au nanoparticles and Ag nanoparticles share many common features Hence the discussion on the synthesis of Au and Ag nanoparticles will be based on the methods of preparation rather than the type of nanoparticles produced... Au or Ag monometallic nanoparticles as well as Ag-Au bimetallic nanoparticles These topics are presented in four sections The discussion begins with the general principles of monodisperse nanoparticle formation This is followed by a survey of current methods of preparation of monometallic Au and Ag nanoparticles; and Ag-Au bimetallic nanoparticles including alloy, core-shell and hollow nanoparticles, ... nanoparticles; C: TEM image of monodisperse Au icosahedral nanoparticles; D: HRTEM image of an isolated Au icosahedral nanoparticle 61 Figure 4.6 A: UV/Vis absorption spectrum of Pd icosahedral nanoparticles The inset is the digital photo of the Pd nanoparticles in toluene B: EDX spectrum of the Pd icosahedral nanoparticles; C: TEM image of monodisperse Pd icosahedral nanoparticles; D: HRTEM image of an isolated... noble metal nanoparticles in chemical and electrochemical reactions (Roucoux et al, 2002; Astruc et al., 2005) The properties of noble metal nanoparticles can be tuned by their size, crystallinity, morphology and surface chemistry (Burda et al., 2005) In addition, the properties of 1 Chapter 1 noble metal nanoparticles can also be modified by combining two metals within a single particle to form bimetallic... image of the mixture of icosahedral and decahedral Ag MTPs and single-crystalline TO nanoparticles 57 Figure 4.4 A: TEM image of monodisperse Ag icosahedral nanoparticles; B: HRTEM image of an isolated Ag icosahedral nanoparticle 59 Figure 4.5 A: UV/Vis absorption spectrum of Au icosahedral nanoparticles The inset is the digital photo of the Au organosol; B: EDX spectrum of the Au icosahedral nanoparticles; ... 7.6 Evolution of the absorption spectra of bimetallic nanoparticles 137 Figure 8.1 A: UV-visible absorption spectra of citrate-stabilized and MBSA-capped Ag nanoparticles; B: Digital pictures of citrate-stabilized and MBSA-capped Ag nanoparticles 146 Figure 8.2 TEM image and histogram of MBSA-protected Ag nanoparticles before size-sorting 146 Figure 8.3 TEM image and histogram of Ag nanoparticles after... representation of the two-layer superlattice; F: SEM image of a superlattice formed in the solution; G: high-magnification SEM image of the superlattice formed in the solution 67 Figure 5.1 TEM image of Ag nanoparticles; Inset shows the HRTEM image of a Ag nanoparticle 75 Figure 5.2 A: EDX spectrum of alloy nanoparticles from AgAu-2; B: The change of atomic percentage of Au with the volume of 1 mM HAuCl4... Normalized UV-Visible spectra of Ag, Au and alloy nanoparticles The inset shows the change of absorbance peak with the atomic percentage of Au; B: photos of Ag1, AgAu-1, 2, 3 and 4 and Au nanoparticles (from right to left) 77 Figure 5.4 A-D: TEM images of nanoparticles from AgAu-1, 2, 3 79 and4 Figure 5.5 A: HRTEM image of a nanoparticle in AgAu-2; B: Electron diffraction(ED) pattern of nanoparticles from AgAu-2;... after the addition of HAuCl4 as viewed from the , , and directions; D-F: 133 XV corresponding schematic illustrations of the bimetallic nanoparticles Figure 7.5 A-C: HRTEM images of the bimetallic nanoparticles formed 360 seconds after the addition of HAuCl4 as viewed from the , , and directions; D-F: corresponding schematic illustrations of the bimetallic nanoparticles 135... Schematic illustration of the total free energy of a nanoparticle as a function of the nucleus radius (Cao, 2004) 10 Figure 2.2 Schematic illustration of the formation process of colloidal particles (Haruta and Delmon, 1986) 11 Figure 3.1 Crystallinity tunable synthesis of Au nanoparticles A-B: TEM and HRTEM images of single-crystalline Au nanoparticles; C-D: TEM and HRTEM images of round decahedral Au . SYNTHESIS OF MONODISPERSE NOBLE METAL NANOPARTICLES ZHANG QINGBO NATIONAL UNIVERSITY OF SINGAPORE 2008 SYNTHESIS OF MONODISPERSE NOBLE METAL NANOPARTICLES. size distribution of icosahedral Ag nanoparticles 59 4.3.3 Synthesis of monodisperse Au and Pd icosahedral nanoparticles 61 4.3.4 Size Manipulation of monodisperse icosahedral nanoparticles 65. illustrations of the bimetallic nanoparticles. Evolution of the absorption spectra of bimetallic nanoparticles. A: UV-visible absorption spectra of citrate-stabilized and MBSA-capped Ag nanoparticles;