Nanometric Metallic Particles Research Articles

Photoelectric quantum yield of nanometer metal particles

The absolute photoelectric quantum yield of nanometer metal particles (Ni, Pd, Cu, Ag, Au) is measured from threshold up to photon energies hν of 10 eV. The particles are produced and measured in ultrapure helium at atmospheric pressure. Yield Y and photothreshold φ are compared to bulk data. The shape of Y(hν) is similar for particle and bulk with all investigated materials except Ag. All metals have in common that the particle yield is larger by a factor ≊100 compared to the bulk yield. Apart from electrostatic corrections due to the image and Coulomb potential, the photoelectric threshold is identical for the bulk and the particle.

Physicochemical properties of small metal particles in solution: "microelectrode" reactions, chemisorption, composite metal particles, and the atom-to-metal transition

The study of nanometer and subnanometer colloidal metal particles in aqueous solution complements the investigation of small particles in molecular beams, frozen solutions, and inorganic clusters. The electronic properties of the metal particles are changed by surface modification, for example by chemisorption of a nucleophilic molecule or by deposition of a second metal. The resulting changes in the chemical, photochemical, and optical properties are discussed. Methods are described which enable one to store excess electrons or positive holes on the particles in a controlled manner and to investigate the accompanying changes in the optical properties. Metal particles carrying excess electrons initiate electrochemical reactions such as the reduction of water or the deposition of metals

Small metal particles

This review article is devoted to results of theoretical and experimental investigations of properties of nanometer metal particles. First, the modern theory of equilibrium structures and shapes of small particles is presented. The next Section deals with the thermodynamics of small particles. It reflects the present state of the theory of surface forces for small particles, including crystalline ones. Validity conditions are pointed out for the standard approach, and an alternative approach is described which is adequate for particles surrounded by their saturated vapor. In it the Laplace pressure is not a real physical force, but a formal quantity that describes the size dependence of the chemical potential. Specific features are described of melting and interphase fluctuations in small particles. In describing the electron properties of the particles emphasis is laid on the smoothed level density and the size dependence of the Fermi energy. Some effects caused by this dependence are presented, in particular the mutual charging of particles of different sizes which manifests itself in an anomalously strong attraction between particles and so on. Magnetic properties of small particles are also described including macroscopic quantum tunneling of magnetization.