XPS spectra of Pb 4f core levels to identify oxidized species. (a) CTAB-treated PbS CQDs film (0 day), (b) OA-treated PbS CQDs film (0 day), (c) CTAB-treated PbS CQDs film (3 days), and (d) OA-treated PbS CQDs film (3 days). The dark curve is the original data and the orange asterisk is the superposition of fitted peaks. Peaks are indicated for elemental lead (red squares), lead in PbS (orange circles), lead in PbS linked to capping ligands (green triangles), and lead in PbSOx (blue stars).
Heo et al. Nanoscale Research Letters 2013 8:488 doi:10.1186/1556-276X-8-488