Ligand removal from supported nanocrystals by room temperature ozone treatment and evolution of surface coordination state

Removal of capping ligands on metal nanocrystals (NCs) is important for studying structure-property relationship with supported NCs. Herein, we demonstrate a room temperature ozone treatment to remove poly(N-vinyl-2-pyrrolidone) (PVP) and poly(vinyl alcohol) (PVA) on metal NCs. With Fourier transform infrared spectroscopy of CO as a probe molecule (CO-FTIR) method, the changes of surface coordination numbers on Pt NCs during ozone treatment and thermal calcination are probed. A room temperature ozone treatment method was used to remove PVP on Pt NCs and PVA on Au NCs. Compared with thermal calcination, ozone treatment can preserve the particle size of Pt and Au. CO-FTIR is used to characterize the evolution of the surface coordination state of Pt NCs during ozone treatment or thermal calcination. Little changes of Pt coordination numbers occur during ozone treatment, while a significant proportion of well-coordinated (WC; terraces) sites develop during thermal calcination. Ozone treatment is advantageous in maintaining the size and surface coordination state of metal NCs during ligand removal for further investigation of structure-property relationship.