Dry ball-milling preparation and characterization of graphite–phthalocyanine composites

Abstract

The hybrids of phthalocyanines with carbon nanotubes, graphene and graphene oxide were demonstrated previously to be promising for different catalytical, electrocatalytical and other applications. Nevertheless, the above carbon nanomaterials are toxic and relatively expensive. We attempted to substitute them by low-cost and harmless graphite, using dry ball-milling of graphite–phthalocyanine mixtures under mild conditions. According to scanning electron microscopy imaging and powder X-ray diffraction, the composites obtained exhibit the absence of crystalline phthalocyanine phase, which implies high efficiency of phthalocyanine milling. According to Raman spectroscopy data, the mechanochemical treatment does not provoke the formation of large amounts of defects in graphite, but instead helps its exfoliation. The composites were characterized by UV-visible spectroscopy and thermal gravimetric analysis, which showed that all of them exhibit a reduced thermal stability compared to unprocessed graphite by roughly 100–250 °C. The strength of interaction of phthalocyanines with a graphene sheet (as a graphite surface model), geometries and selected electronic parameters (frontier orbital and spin density distribution, HOMO-LUMO gap energies) of the resulting noncovalent complexes were analyzed at the PBE-D2/DNP theoretical level. The interactions of phthalocyanines with the graphene sheet are strong, with the calculated formation energies (absolute values) for the noncovalent complexes of 62.1–70.1 kcal/mol.

Keywords:

• Graphite
• phthalocyanines
• ball-milling
• composites
• characterization

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

Financial support from the National Autonomous University of Mexico (UNAM, grant DGAPA-IN103622) is greatly appreciated. C. U. M.-D. is indebted to the Doctorate Degree Program in Chemical Sciences of UNAM and the National Council of Science and Technology of Mexico (CONACyT) for a PhD scholarship. The authors are also grateful to the University Laboratory of Spectroscopic Characterisation of UNAM (LUCE-ICAT-UNAM) for the use of Raman equipment, and to MSc José de la Rosa Canales (Unidad de Laboratorio Rafael Navarro González, Departamento de Física de Plasmas e Interacción con la Materia, ICN-UNAM) for the help with TGA measurements. V. A. B. and E. V. B. are on sabbatical leave from UNAM.