In recent years, metal nanoparticles have been widely exploited for use, for example, in catalysis, magnetic recording media, biological labeling, and formulation of magnetic ferrouids [1-3]. Many methods have been developed to produce metal nanoparticles. Examples include vapor deposition [4], electrochemical reduction [5], radiolytic reduction [6], chemical reduction [7,8], and thermal decomposition [9]. The chemical reduction in solution has been proven to be the most versatile and simple approach for preparation of metal nanoparticles. The reduction agent usually used in this method may be hydrazine [10], sodium boron hydride [11], or formaldehyde [12].