Procedures for the synthesis and capping of metal nanoparticles

The increasing impact of metallic nanoparticles in life sciences has stimulated the development of new techniques and multiple improvements of the existing methods of manufacturing nanoparticles with tailored properties. Nanoparticles can be synthesized through a variety of physical and chemical methods. The choice of preparation procedure will depend on the physical and chemical characteristics required on the final product, such as size, dispersion, chemical miscibility, optical properties, among others. Here we review basic practical procedures used for the preparation of protected and unprotected metallic nanoparticles and describe a number of experimental procedures based on colloidal chemistry methods. These include gold nanoparticle synthesis by reduction with trisodium citrate, ascorbic acid, or sugars in aqueous phase; nanoparticle passivation with alkanethiols, cetyltrimethylammonium bromide, or bovin serum albumin. We also describe microwave-assisted synthesis, nanoparticle synthesis in ethylene glycol, template-assisted synthesis with dendrimers and briefly describe how to control nanoparticle shape (star-shaped and branched nanoparticles).