Intense and stable room-temperature photoluminescence from nanoporous vanadium oxide formed by in-ambient degradation of VI3 crystals

Vanadium oxides have attracted research interest because their optoelectronic properties make them optically active with room-temperature photoluminescence (PL) emission, which, however, is not sufficiently intense for real applications. For this reason, many nanostructured vanadium oxides are currently fabricated through several precursors and different treatments to improve the PL efficiency and enhance the PL intensity. Herein, we propose an alternative and facile route to the fabrication of nanoporous vanadium oxide flakes through the spontaneous in-ambient degradation of layered van der Waals VI crystal, which is composed of a mixture of VO and VO phases. The as-grown VI crystals and the formed nanostructured vanadium oxide have been thoroughly studied using X-ray diffraction (XRD) and Raman spectroscopy to access the structural properties, X-ray photoemission spectroscopy (XPS) and synchrotron-based XPS to analyze the electronic core levels and valence bands, scanning electron microscopy (SEM) to access the morphology, and PL spectroscopy to grasp the optoelectronic properties. The nanoporous vanadium oxide system reveals an intense room-temperature PL emission in the red light visible range between 1.7 and 2.0 eV (620 and 730 nm), which is consistent with the VO PL response. Remarkably, the PL emission reaches high intensity compared with those of different VO nanostructures and is stable for months without intensity quenching and energy shifting. This discovery easies the integration of nanostructured vanadium oxides in optoelectronic nanodevices. Besides, the facile methodology proposed here promises to be applied to realize other nanostructured transition metal oxides.