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This chapter describes the shape and structure of Ag and noble-metal nanoparticles, including the shell model for the structure of their nuclei, the shape of single-crystalline metal nanoparticles, shapes and structures of defect-induced anisotropic nanoparticles (nanorods and nano plates), and core/shell nanoparticles of different metals. The shape and structure of photographic Ag and AgX nanoparticles are then described, each of which has a face-centred cubic (fcc) crystal structure. The smallest stable cluster of an Ag nanoparticle is thought to be Ag₂ (nuclei of Ag_n, where n≥ 4, form latent image centres). All possible shapes of single-crystalline nanoparticles with fcc structure are then described. The shape and structure of tabular AgX nanoparticles with {111} and {100} surfaces and composite nanoparticles with different AgXs (uniform, core/shell, and epitaxial) are also discussed. Explanations of the measurements of sizes of nanoparticles and crystallites, interatomic distance, defect observation, and AgX surface structure and morphology, are all provided.

This chapter provides introductory remarks on metal nanoparticles, silver halide photography, and the correspondence between nanoparticles in silver halide photography and plasmonics. Metal nanoparticles form a bridge between bulk materials and atomic or molecular structures, thus providing a unique performance and many applications in plasmonics. Since 1839 silver halide photography has utilized nanoparticles of Ag and silver halide. These are both face-centred cubic in crystal structure, and their fruitful study over many years has led to a wealth of knowledge being accumulated. Nanoparticles of Ag and noble metals in plasmonics are contrasted with those of Ag and silver halide in photography, and their structure, preparation, property, and performance are all addressed.

The preparation of metal nanoparticles for plasmonics according to the LaMer Diagram is described, and this knowledge is extended to single-crystalline nanoparticles with variations in crystal habit, nanorods, and nanoplates. This is reinforced by knowledge of the preparation of photographic Ag and AgX nanoparticles. Formation mechanisms of reduction sensitization and latent image centres (Ag₂ and Ag_n with n≥4) serve as nuclei for Ag nanoparticles. Photographic development provides knowledge of the growth of small Ag_n clusters in the presence of silver ions and reducing agents. Descriptions of the growth of AgX nanoparticles include protective colloids and apparatus for this. Mechanisms for preparing all the possible single-crystalline nanoparticles with fcc structure, tabular nanoparticles, core/shell, and epitaxial nanoparticles with different AgXs, together with methods of preparing nanoparticles with monodispersity and enhanced anisotropy in shape and arranging them, are also discussed.

Metal nanoparticles acting as catalysts are classified into two types (homogeneous and heterogeneous) and characterized. The roles and mechanisms of metal nanoparticles as catalysts and promoters for various reactions are then described systematically and reinforced by knowledge of the use of Ag nanoparticles as catalysts and promoters, which has accumulated in the field of AgX photography over many years. The dependencies of redox potentials and catalytic activity of Ag nanoparticles on their size and shape, as well as on the locations on AgX surfaces at which they are formed, are described. The determination of the size of the smallest Ag nanoparticles required for catalytic activity is also discussed.

This chapter describes the absorption and scattering spectra of Ag and Au nanoparticles. The spectra of small nanoparticles result from transitions between their discrete electronic energy levels. The spectra of medium and large nanoparticles result from excitations of their surface plasmon resonances. The latter includes information on their dependencies on nanoparticle size and shape (nanorod and nanoplate), the coupling of plasmon resonances and the type of linkage between adjacent anisotropic nanoparticles. This knowledge is reinforced by the achievement of the unique arrangement of Ag and AgX nanoparticles and the aggregate formation of chromophores (cyanine dyes) to provide unique absorption spectra in AgX photography, both of which have been studied over many years.

The stability of Ag nanoparticles is described in this chapter by taking into account the following two conflicting facts. On the one hand, Ag nanoparticles are not regarded to be stable enough for use in plasmonics, although they exhibit a stronger plasmonic effect than Au nanoparticles that are representative of plasmonic elements. On the other hand, Ag nanoparticles have aquired an extremely long lifetime in air, being surrounded by gelatin in photographic materials. Analytical studies of gelatin and synthetic polymers have revealed that gelatin has the significant ability to protect Ag nanoparticles from degradation by controlling their Fermi level with respect to that of gelatin phase around them in air. This result led to the idea of protecting metal nanoparticles from degradation by polymers with widely controllable properties.

The mechanism of the photovoltaic effect of metal nanoparticles in contact with inorganic semiconductor nanoparticles is proposed, first for the surface plasmon-induced generation of hot electrons in metal nanoparticles and then for the transfer of the hot electrons to inorganic semiconductor nanoparticles to ultimately bring about charge separation. This explanation is reinforced by knowledge of the photovoltaic effect of Ag nanoparticles on AgX nanoparticles, referred to as the photographic Bequerel effect, which has been studied and analysed for more than a century in photographic systems. This mechanism is verified by the fact that the smallest photon energy for the photovoltaic effect corresponds to the difference between the work function of a metal and the electron affinity of a semiconductor in both Au/TiO₂ and Ag/AgBr systems in photography. Several other possible mechanisms for the photovoltaic effect are also discussed.

This chapter introduces cavity quantum optomechanics with levitated nanospheres with some emphasis on preparing mesoscopic quantum superpositions and testing collapse models. It is divided into three parts: levitated quantum optomechanics: atoms vs. sphere; decoherence in levitated nanospheres; and wave-packet dynamics: coherence vs. decoherence. It is first shown how the master equation describing the dynamics of a polarizable object in a cavity along the cavity axis and that of the cavity mode is derived. Optical levitation is also discussed. It is then shown how most of the decoherence sources in levitated nanospheres can be cast into a relatively simple master equation describing position localization type of decoherence. Such decoherence tends to suppress the centre-of-mass position coherences. Finally, a discussion of wave-packet dynamics is given, with the motivation of using levitated nanospheres for matter-wave interferometry, that is, to create macroscopic quantum superpositions for testing quantum mechanics in unprecedented parameter regimes.

This chapter outlines the fabrication methods of oxide thin films, from the oxidation of the outer layers of bulk elemental solids to thin film deposition methodologies. The classical theories treating the thermal oxidation of metals and silicon are reviewed. A particular focus is put on the oxidation of alloy single crystal surfaces to generate ultrathin oxide films and the formation of surface oxides, the latter as precursor layers for thicker bulk-type oxide phases. The diverse deposition techniques to grow epitaxial thin oxide films are introduced, with a classification into physical and chemical methods for the ease of presentation; the benefits and disadvantages of the different methods are pointed out. The synthesis of oxide nanoparticles is discussed in the gas phase and in liquid phase environments. The fundamental concepts of nucleation and growth of thin films and nanoparticles are introduced, including the classical capillary approach and atomistic descriptions.