Noble metal nanoparticles have attracted enormous scientific and technological P C interest because of their unique optical properties, which are related to surface plasmon l o resonances. The interest in nanosized metal particles dates back to ancient societies, a l when metals were used in various forms as decorative elements. From the famous s l Lycurgus cup, made by the Romans in AD 4th century, through thousands of stained o m glasses in churches and cathedrals all over medieval Europe, bright-yellow, green, or i red colors have been obtained by a touch of metallic additions during glass blowing. d o This peculiar interaction of light with nanometals can be widely tuned through the a Colloidal Synthesis of morphology and assembly of nanoparticles, thereby expanding the range of potential n l applications, from energy and information storage to biomedicine, including novel i diagnostic and therapeutic methods. c S Plasmonic Nanometals y N This book compiles recent developments that clearly illustrate the state of the art in n this cutting-edge research field. It comprises different review articles written by the a teams of Prof. Luis Liz-Marzán, an international leader in chemical nanotechnology t n who has made seminal contributions to the use of colloid chemistry methods to h edited by Luis Liz-Marzán understand and tailor the growth of metal particles at the nanoscale. Apart from o e synthesis, the book also describes in detail the plasmonic properties of nanomaterials m s and illustrates some representative applications. This book will appeal to anyone i involved in nanotechnology, nanocrystal growth, nanoplasmonics, and surface- e s enhanced spectroscopies. t o Luis Liz-Marzán is Ikerbasque professor and scientific director of the a f Center for Cooperative Research in Biomateriales, CIC biomaGUNE, in l San Sebastián, Spain, since September 2012. He is also a group leader s of the Biomedical Research Networking Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN). He obtained his PhD in chemistry from the University of Santiago de Compostela, Spain, in 1992. He was a postdoctoral researcher at Utrecht University, the Netherlands, from 1993 to 1995 and a professor at the University of Vigo, Spain, from 2006 to 2012. Prof. Liz-Marzán is a member of several Spanish and European academies, has published more than 450 papers, and has 8 patents to his name. He has received numerous research awards and is one of the few European researchers who were awarded two consecutive European Research Council Advanced Grants. L Prof. Liz-Marzán is considered a pioneer of the synthesis and growth mechanisms iz - of metal nanocrystals has and made significant contributions to the study of their M plasmonic properties, surface chemistry, and directed self-assembly. He also works on a r the biomedical applications of well-defined metal nanoparticles and nanostructures. z á n V715 ISBN 978-981-4800-67-9 Colloidal Synthesis of Plasmonic Nanometals Colloidal Synthesis of Plasmonic Nanometals edited by Luis Liz-Marzán Published by Jenny Stanford Publishing Pte. Ltd. Level 34, Centennial Tower 3 Temasek Avenue Singapore 039190 Email: [email protected] Web: www.jennystanford.com British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Colloidal Synthesis of Plasmonic Nanometals CAlol priygrhitgsh rte s©er v2e0d2. T0h bisy b Joeonkn, oyr S ptaarntfso thrder Peoufb, mlisahyi nnogt Pbete r.e Lptrdod.uced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. ISBN 978-981-4800-67-9 (Hardcover) ISBN 978-0-429-29518-8 (eBook) Contents Preface 1. Na nome tals: Formation and Color xi1x Luis M. Liz-Marzán 1.1 Introduction 2 1.2 Synthesis of Metal Nanoparticles 3 1.3 Optical Properties 7 1.3.1 Dilute Dispersions 8 1.3.2 Thin Films 9 2. 1G.o4l d NaCnoonrocdluss: iSoynn thesis, Characterization and 11 Applications 15 Jorge Pérez-Juste, Isabel Pastoriza-Santos, Luis M. Liz-Marzán, and Paul Mulvaney 2.1 Introduction 16 2.2 Optical Properties of Metal Nanorods 18 2.2.1 Absorption by Small Metal Spheres 19 2.2.2 Absorption by Small Metal Ellipsoids 22 2.2.3 The Effect of Aspect Ratio 24 2.2.4 The Effect of the Refractive Index of the Solvent 26 2.2.5 The Effect of a Shell Layer 28 2.2.6 Orientation Effects 29 2.3 Synthesis and Mechanism for Au Nanorod Formation 30 2.3.1 Template Method 31 2.3.2 Electrochemical Methods 32 2.3.3 Seeded Growth Method 34 2.3.3.1 Synthesis without AgNO3 35 2.3.3.2 Synthesis with AgNO3 41 2.3.4 Other Methods 46 2.4 Structural Characterization 47 2.4.1 Electrochemical Method 48 vi Contents 2.4.2 Seed-Mediated Method 51 2.5 Reactivity and Surface Modification 54 2.5.1 Anisotropic Chemical Reactivity 54 2.5.2 Au@Ag Core-Shell Nanorods 55 2.5.3 Silica Coating 57 2.5.4 Self-Assembly of Gold Nanorods 58 2.6 Gold Nanorods and Lasers 61 2.6.1 Ultrafast Dynamics of Gold Nanorods 62 2.6.2 Laser-Induced Structural and Morphological Transitions in Gold Nanorods 68 2.7 Nanocomposites 74 3. 2Th.8e AsseAmppblliyc aotfi Coonast ed Nanocrystals 7899 Luis M. Liz-Marzán and Paul Mulvaney 3.1 Introduction 90 3.2 Coated Nanocrystals 95 3.2.1 Coating of Nanocrystals with Silica 96 3.2.2 Coating of Metal Nanocrystals with Semiconductors 101 3.3 Assembly of Coated Nanocrystals into Thin Films 104 3.3.1 Fe3O4@SiO2 Thin Films 106 3.3.2 Au@SiO2 Thin Films 107 3.3.3 Hollow TiO2 Thin Films 111 3.4 Doped Glass from Coated Nanoparticles 113 3.5 Ordered Nanocrystal Assemblies 116 3.5.1 Au@SiO2 Opals 116 3.5.2 Inverse Opals from Au@SiO2 Particles 119 3.6 Nanomechanics 121 4. 3Ta.7il oringC oSunrcflaucseio Pnlas samnodn Osu tthlorooukg h the Morphology 122 and Assembly of Metal Nanoparticles 131 Luis M. Liz-Marzán 4.1 Introduction 132 4.2 Surface Plasmon Resonance 134 4.2.1 Optical Effects 134 Contents vii 4.3 AuAg Bimetallic Nanoparticles 137 4.3.1 Alloys vs. Core-Shells 137 4.4 Gold Nanorod Alignment and Patterning 142 4.5 Isotropic vs. Anisotropic Colloidal Assemblies 145 4.6 Metal Nanoprisms: Colloids and Assemblies 149 5. 4Co.7l loidaCl oSnilvcelurs Nioannso plates: State of the Art and 153 Future Challenges 159 Isabel Pastoriza-Santos and Luis M. Liz-Marzán 5.1 Introduction 160 5.2 Optical Properties 161 5.2.1 Surface Plasmons 161 5.2.2 Numerical Methods: DDA and BEM 163 5.2.3 Theoretical Analysis and Comparison with Experimental Data 167 5.3 Synthesis and Formation Mechanisms 173 5.3.1 Light-Mediated Methods 174 5.3.2 Chemical Reduction Method 178 5.3.3 Nanosphere Lithography 181 5.4 Structural Characterization 183 5.5 Reactivity and Stability 187 5.6 Applications 189 6. 5Sh.7a pe CCoonntrcolul isnio Gnosl da nNda Onouptlaorotikc le Synthesis 119917 Marek Grzelczak, Jorge Pérez-Juste, Paul Mulvaney, and Luis M. Liz-Marzán 6.1 Introduction 198 6.2 Anisotropic Gold Nanoparticles in Water 199 6.2.1 Nanorods 199 6.2.2 Platonic Nanoparticles 202 6.2.3 Nanoplates 203 6.2.4 Branched Nanostructures 204 6.3 Growth Mechanisms 205 6.3.1 Growth Mechanisms for Gold Nanorods in the Absence of Silver Ions 205 6.3.2 Growth Mechanisms for Gold Nanorods in the Presence of Silver Ions 207 viii Contents 6.3.3 Silver Halide Mechanism and Growth of Planar Structures 212 6.4 Anisotropic Gold Nanoparticles in Other Solvents 214 7. 6N.,5N -DimCeotnhcyllufosriomnasm aindde Paes ras pReecatcitvieosn Medium for 217 Metal Nanoparticle Synthesis 221 Isabel Pastoriza-Santos and Luis M. Liz-Marzán 7.1 Introduction 222 7.2 Redox Chemistry of DMF 223 7.3 Nanoparticle Synthesis 226 7.3.1 Capping Agents Other Than PVP 226 7.3.2 PVP as Stabilizer 229 7.3.2.1 Interaction of metal colloids with PVP chains 229 7.3.2.2 Growth of particles on in situ generated seeds 230 7.3.2.3 Particle growth on preformed seeds 234 7.4 Tuning the Optical Response through Particle Size and Shape 240 8. 7Re.5c ent PCroongcrleusssi oonn sS ilica Coating of Nanoparticles 242 and Related Nanomaterials 247 Andres Guerrero-Martínez, Jorge Pérez-Juste, and Luis M. Liz-Marzán 8.1 Introduction 248 8.2 Silica Coating in Water-in-Oil Microemulsions 250 8.2.1 Coating of Pre-synthesized Nanoparticles 253 8.2.2 Coating in situ Synthesized Nanocrystals 256 8.3 Polymer and Surfactant-Mediated Silica Coating 258 8.3.1 Polymer Aggregates 260 8.3.2 Surfactant Vesicles 263 8.3.3 Polymer- and Surfactant-Stabilized Inorganic Particles 265