Defect-assisted photoluminescence in hexagonal boron nitride nanosheets. (1st September 2020)

• Record Type: Journal Article
• Authors: Ren, Junkai; Stagi, Luigi; Carbonaro, Carlo Maria; Malfatti, Luca; Casula, Maria Francesca; Ricci, Pier Carlo; Del Rio Castillo, Antonio Esau; Bonaccorso, Francesco; Calvillo, Laura; Granozzi, Gaetano; Innocenzi, Plinio
• Is Part Of: 2D materials. Volume 7:Number 4(2020)
• Publication Date: 2020-09-01
• Subjects: hexagonal boron nitride -- defects -- photoluminescence; Graphene -- Periodicals; Materials science -- Periodicals; Nanostructured materials -- Periodicals; 620.115
• DOI: 10.1088/2053-1583/ababf0
• Languages: English
• ISSNs: 2053-1583

Abstract

Abstract: The development of functional optoelectronic applications based on hexagonal boron nitride nanosheets ( h -BNNs) relies on controlling the structural defects. The fluorescent emission, in particular, has been observed to depend on vacancies and substitutional defects. In the present work, few-layer h -BNNs have been obtained by sonication-assisted liquid-phase exfoliation of their bulk counterpart. The as-prepared samples exhibit a weak fluorescent emission in the visible range, centred around 400 nm. Tailored defects have been introduced by oxidation in air at different temperatures. A significant increase in the fluorescent emission of the oxidated h -BNNs has been observed with maximum emissive intensity for the samples treated at 300 °C. A further increase in temperatures (>300 °C) determines a quenching of the fluorescence. We investigated, by means of detailed microscopic and spectroscopic analysis, the relationship between the optical properties and defects of h -BNNs. The investigation of the optical properties as a function of treatment temperature highlights the critical role of hydroxyl groups created by the oxidation process. Only h -BN exfoliated in water allows introducing OH groups with consequent enhancement of fluorescence emission. Quantum chemical calculations support the experimental findings.