XPS spectrum of AuNPs synthesized via CO gas reduction. The Au 4f7/2 peak appeared at a binding energy of 83.98 eV and the Au 4f5/2 peak appeared at a binding energy of 87.71 eV. This indicates the formation of metallic gold [27,28].
Young et al. Nanoscale Research Letters 2011 6:428 doi:10.1186/1556-276X-6-428