Resumen de Using Silver Nanoclusters as a New Tool in Nanotechnology: Synthesis and Photocorrosion of Different Shapes of Gold Nanoparticles
Ángel M. Pérez Mariño, María del Carmen Blanco Varela, David Buceta Fernández, Manuel Arturo López Quintela
Until now, the concept of metal (0) atomic quantum clusters or nanoclusters (NCs) and their increasing role in nanotechnology due to their novel and exceptional properties in important industrial fields (such as catalysis) has not been included at the education level. Here, syntheses of both metal nanoparticles (NPs) and metal nanoclusters (with sizes below ≈1–2 nm) are used for understanding the large differences between both types of nanomaterials. In this experiment we highlight the catalytic and photocatalytic properties of silver NCs, as well as the plasmon band, as the main optical difference between metal NPs and NCs. In the first step of the experiment, the synthesis of different sizes and shapes of AuNPs is carried out and changes in their plasmon band are discussed. In a second step, students conduct the anisotropic growth of AuNPs, catalyzed by silver NCs (Agn, where n is the number of atoms forming the cluster), which do not display a plasmon band. Finally, it is shown that Agn NCs can induce AuNP photocorrosion, which can be avoided by introducing molecules with more negative redox potential (called hole scavengers). Redox properties of Agn NCs are used in this laboratory experiment to discuss with the students several important physicochemical issues, such as absolute and hydrogen redox potential scales, electronic and optical properties of nanomaterials, semiconductor band gap, photogenerated electron–hole pairs (excitons), catalysis and photocatalysis, the role of hole scavengers, or spontaneous process and free energy. This very new area at the bottom of nanotechnology is ideal to make chemistry relevant and engaging for students. It allows them to learn fundamentals by using chemistry that is at the frontier of research, and they are able to do this in an accessible way.
