Poly(sulfur nitride) Nanowires as Short Circuits between Highly Oriented Pyrolytic Graphite Sheets

Highly oriented pyrolytic graphite (HOPG) is intercalated with poly(sulfur nitride) (SN)x. In a first step, HOPG is swollen in N-methyl pyrrolidone (NMP) supported by ultrasonication. Then, HOPG is exposed to disulfur dinitride (S2N2) vapor, which polymerizes to (SN)x nanowires oriented perpendicular to the HOPG platelets, with a thickness of roughly 30 nm. The graphene layers constituting the platelets remain largely intact. The S2N2 ring-opening polymerization is mainly initiated at the lateral edges of the HOPG mosaic crystals, as observed by scanning electron microscopy. The electrical short circuit between the HOPG platelets, caused by the electrically conductive (SN)x nanowires, increases the diamagnetism parallel to the basal HOPG planes, which is perpendicular to the (SN)x nanowires. This results in a strong decrease in the diamagnetic anisotropy, defined as the ratio of the real part of the susceptibility parallel χ∥′ and perpendicular χ⊥′ to the crystallographic c-axis of HOPG. Thus, the ratio χ∥′ / χ⊥′ ≥ 40 for pure HOPG drops to χ∥′ / χ⊥′ ∼ 3 after intercalation with (SN)x.