Preface This book is a result of the symposium Nanoparticles: Synthesis, Stabilization, Passivation, and Functionalization held at the 233 American Chemical Society (ACS) National Meeting in Chicago, Illi nois on March 25-29, 2007. The symposium was sponsored by the A C S Division of Colloid and Surface Chemistry as part of its continuing series of symposia focusing on various aspects of nanoscience and nanotechnology. Approximately 100 papers were presented at this symposium and the papers included in this book contain a sampling of various problems addressed in this symposium. Every chapter in this book emphasizes one or more of the themes— synthesis, stabilization, passivation, and functionalization of nano particles. The shapes of nanoparticles considered are diverse and include spheres, cubes, nanorods, nanowires, nanopyramids, and so on. Equally diverse are the methods to synthesize, stabilize, passivate, and functionalize the nanomaterials described in these chapters. Most of the chapters also provide discussion of many nanoparticle characterization methods, identify novel properties displayed by the functionalized nanoparticles, and provide the scientific basis for potential applications of these nanoparticles. The book is divided into sections that are based on the chemical feature of the nanoparticles emphasized; for example, antibody conjugated gold nanorods are included under bionanoparticles rather than under metal nanoparticles. Clearly, the chapters can be moved from one grouping to another and the classification is not rigid. Chapter 1 presents a general introduction to nanoparticles as buil ding blocks for nanotechnology, emphasizing the diversity of nano particles and drawing attention to the growing activity in scientific studies as well as providing practical applications. The first section describes metal nanoparticles, with gold nano particles being predominant. Chapter 2 describes the colloidal approach to synthesize gold nanoparticles and the performance of various rd
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stabilizing agents as they impact on the near infrared surface-enhanced Raman scattering activity of the nanoparticles. Chapter 3 shows how a controlled number of functional groups can be attached to gold nano particles by the solid phase place exchange reaction. Methods to synthesize thiol surfactants of various lengths are outlined in Chapter 4. These thiols can spontaneously assemble as monolayers on gold nano particles and can act as stabilizers of gold nanoparticle dispersions in organic solvents. In Chapter 5, the use of a mixture of thiols and charged thiols that self-assemble on gold nanoparticles is shown to lead to phase separation of the thiols on the particle surface and to provide water dispersibility of the nanoparticles essential for many biological and medical applications. Chapter 6 demonstrates ways to tune plasmon resonance of metal nanoparticles by changes in the shape of gold nanoparticles with gold nanorods and bipyramids and by the synthesis of gold/silver or gold/silver sulfide core/shell particles. The formation of nanotubes and nanocapsules from silver using wet chemical methods are described in Chapter 7. Chapter 8 describes the synthesis of tannic acidfunctionalized, iron tannate magnetic nanoparticles, their surface charac terization, and their ability to complex with other metal atoms. In Chap ter 9 time-dependent density functional theory is used to evaluate the adsorption properties of passivating ligands on a 20-atom gold nano particle. The second section focuses on metal oxide nanoparticles. The for mation of iron oxide nanoparticles and their size are shown to be affected by a surfactant added as the stabilizing agent, in Chapter 10. The synthesis of titania nanotubes and growth of anatase thin films are described in Chapter 11. It is shown that the amorphous and polycrystalline surfaces lead to marked differences in the thermal desorption of various molecules, indicating a structure-binding activity relationship relevant for catalytic applications. Chapter 12 describes a hydrothermal condensation method to prepare nanowires of vanadium pentoxide. The third section of the book (Chapters 13 to 19) deals with semi conductor and other inorganic nanoparticles. The preparation of quan tum dot surfactants and their properties as Langmuir-Blodgett films with controlled nanoparticle separations are described in Chapter 13. The synthesis of composite nanoparticles with fluoroalkyl end-capped acrylic acid oligomers grafted on silica nanoparticles is described in Chapter 14, which also shows that antimicrobial agents can be encapsulated in this composite particle to provide efficient antibacterial activity. Chapter 15 presents a kinetic study of silver sulfide nanoparticle formation using xii
stopped flow technique. The preparation of ultrabright silica nano particles, which have potential applications in tagging, tracing, and labeling by physical entrapment of a fluorescent dye, is described in Chapter 16. Chapter 17 presents a comprehensive view of the microwave irradiation method to produce passivated and stabilized nanoparticles, nanowires, and nanorods from metals, metal oxides, and various semiconductors and rare earth oxides. The creation of nanoporous mem branes using silica nanoparticle crystalline films and their permeability properties to ions are discussed in Chapter 18. In Chapter 19, the convectional, sedimentation and drying patterns of nanoparticle dispersions showing the nanoparticle assemblies that can be generated by different means are described. The fourth section of the book concentrates on polymeric and polymer-stabilized nanoparticles. A general strategy to synthesize ferromagnetic nanoparticles coated with end-functionalized polystyrene surfactants is described in Chapter 20. Using ligand exchange, a versatile approach to the functionalization of the ferromagnetic nano particles is achieved. Chapter 21 describes the synthesis of amphiphilic polymer conetworks and the characterization and swelling properties of the resulting nanodomains. Ring-opening metathesis polymerization methods to produce polymer overlayers on solid nanoparticles are discussed in Chapter 22. Four different methods of preparing polysaccharide-covered polymer nanoparticles using amphiphilic poly saccharides and the properties of the synthesized nanoparticles are correlated to the methods of their preparation are covered in Chapter 23. Chapter 24 describes ways to produce stable polymer nanoparticles of controlled size from amphiphilic block copolymers, using a binary sol vent mixture of a good solvent and a selective solvent. The last section focuses on organic, carbon, and biofunctionalized nanoparticles. A novel method to crystallize organic nanorods of arachidic acid as branches on cadmium selenide nanoparticles is described in Chapter 25. In Chapter 26, the use of a biological nanoparticle, tobacco mosaic virus, as a template to prepare composite nanofibers as well as to carryout polymerization of aniline are de scribed. The potential to surface modify the tobacco mosaic virus in order to manipulate the assembly and structural patterns of the com posite material are explored. The synthesis of gold nanorods of various aspect ratios and their functionalization with antibodies are discussed in Chapter 27. Biosensing based on surface plasmon resonance with these biofunctionalized nanoparticles is modeled. Chapter 28 presents an xiii
experimental and simulation study of stabilization of aqueous dis persions of single wall carbon nanotubes using gamma cyclodextrins. The stabilizing interaction forces are estimated using A F M and com pared to the simulations. The reviewers of individual chapters contributed prompt critical reviews that have helped improve the quality of the manuscripts. The Editors acknowledge the support from their institutions, Natick Soldier Research, Development, and Engineering Center and Massachusetts Institute of Technology, that allowed them to organize the symposium and develop this book based on selected contributions.
R. Nagarajan Molecular Sciences and Engineering Team Natick Soldier Research, Development, and Engineering Center Natick, MA 01760
[email protected] T. Alan Hatton Department of Chemical Engineering Massachusetts Institute of Technology Cambridge, MA 02139
[email protected] xiv
