Metallic nanoparticles metals in the embryonic state

Metals (mostly silver and gold) in nanometric dispersions have been known since Roman times. The most beautiful example of application of these materials is the Lycurgus cup. This masterpiece of glass-blowing appears green in reflected light, but 

Synthesis of metallic nanoparticles proceeds in many ways they can be divided into physical and chemical. Physical methods include inert gas condensation, arc discharge, ion sputtering, and laser ablation. The main idea behind these methods is condensation of solid particles from the gas phase, the substrate for nanoparticle generation being pure metals (or their mixtures/alloys in the case of complex particle composition). Chemical methods, in turn, include various methods utilizing 

Optical properties of metal nanoparticles embedded in dielectric media can be derived from the electrodynamic calculations within solid state theory. A simple model of electrons in metals, based on the gas kinetic theory, was presented by Drude in 1900 [9]. It assumes independent and free electrons with a common relaxation time. The theory was further corrected by Sommerfeld [10], who incorporated corrections originating from the Pauli exclusion principle (Fermi-Dirac velocity distribution). This so-called free-electron model was later modified to include minor corrections from the band structure of matter (effective mass) and termed quasi-free-electron model. Within this simple model electrons in metals are described as 

The optical properties of metals (ie their response to alternating electromagnetic waves) is described by the dielectric function [11]  

For the same particles, the volume plasmon is located at very high energies (6-9 eV). The surface obviously plays a very important role for the observation of the surface plasmon resonance because it alters the boundary conditions for the polarizability of the metal and therefore shifts the resonance to optical frequencies. In this sense, the surface plasmon absorption is a small particle (or thin layer) effect but is definitely not a quantum size effect [14]. 

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