Fig. 4From: Polymer Microfibers Incorporated with Silver Nanoparticles: a New Platform for Optical SensingXPS a survey, b Li 1s, c Y 3d, d F 1s, e Yb and Er 4d, and f Ag 3d spectra of LiYF4:Yb3+/Er3+ NPs doped with AgBack to article page