Colouring glasses using nanoparticles synthesized within polyelectrolyte layer-by-layer films

In this work polyelectrolyte multilayers (PEMs) produced through the layer-by-layer (LbL) method were used for the in situ synthesis of Au and Ag metal nanoparticles on the surface of float glass in order to colour it. The samples were characterized by UV-Vis absorption spectroscopy, Scanning Electron Microscopy (SEM), Rutherford Backscattering Spectrometry (RBS) and Particle Induced X-Ray Emission (PIXE). The use of temperatures slightly above the glass transition temperature (T_g) during the thermal treatment allowed the fixing of the nanoparticles, colouring the glass surface. Pink and blue colours were obtained from Au nanoparticles, yellow colour from Ag, and orange from a mixture of both Au nanoparticles and Ag nanoparticles. Variables such as the pH value during film assembly, the number of layers used to form the PEMs, the time duration of thermal treatment, and the presence or absence of Sn in the surfaces of float glass, all influence its colouration. Thermal treatments shorter than 1 h already promote the diffusion of Ag into the glass and therefore fix it, while longer times are necessary to fix the Au metal. The Ag colour intensity in the glass is easily controlled through the number of layers while in the case of Au this variable influences not only the colour intensity but also the tone.