This paper presents systematic studies of the C1s signal in the X-ray photoelectron spectra of commercial Cu-phthalocyanine (CuPc) commonly used as a major commercial cyan pigment in a variety of printing applications. Although the CuPc pigment has been widely employed for many decades, the correct interpretation of the C1s signal in non-stoichiometric CuPc pigments has not yet been agreed upon. Our work demonstrates that the composite C1s CuPc signal consists of five components: two related to principal C positions within the CuPc macrocycle, two associated with shake-up transitions accompanying the principal C positions, and one due to mostly aliphatic impurities. A detailed analysis showed that magnitude of shake-up peaks was approximately equal 10% to 12% of their principal transitions, in agreement with theoretical calculations, while the impurities C1s signal corresponded to IR measurement of the aliphatic C-H vibrations. The proposed C1s interpretation has been successfully tested for a large number of commercial CuPc pigments and provides a guideline for routine XPS analysis of the CuPc that can provide a reliable pigment quality control.
K. Nauka, Hou T Ng, "X-ray photoelectron spectroscopy of carbon in commercial copper phthalocyanine pigments" in Proc. IS&T Int'l Conf. on Digital Printing Technologies and Digital Fabrication (NIP26), 2010, pp 159 - 162, https://doi.org/10.2352/ISSN.2169-4451.2010.26.1.art00045_1