Polyaniline against black phosphorus degradation: a long-term stability study

The interest in exploring the properties of black phosphorus (BP)1 has been growing as well as the concern in protecting it against its high instability in air. Thus, we have synthesized a BP-polymeric nanocomposite through the liquid/liquid interfacial method2, aiming to overcome BP deterioration. Aniline was polymerized in a deaerated dispersion of BP and, after the solvent exchange to a biphasic system, a self-standing film of BP covered by polyaniline (PANI) was observed at the interface.3 Raman spectroscopy confirmed the coexistence of both materials in the resulting film. Infrared spectra showed the presence of bands related to modes of phosphorus oxidation for bare BP, attesting its unstable nature, and the absence for BP/PANI, suggesting a protective role of PANI on BP. Thus, both bare and capped materials were exposed to the same ambient conditions and evaluated through different techniques (Figure 1). Scanning electron microscopy images alarmed the beginning of degradation of the uncapped material with only 3 days of exposure, showing the characteristic bubbles on BP surface. The same was observed through Raman, indicated by the gradual decrease in the intensity of BP bands that completely disappear with its total degradation (at about 10 days). The PANI-covered material, however, has taken about 50 days for the same process to begin, reaching an increase of about 1500% in the stability, and it is still under monitoring. Overall, this work enlightens to new possibilities towards the development of thin films suitable to be designed and applied in different BP-based materials.