Ultraviolet emission from 2D tellurium nanosheets synthesised using diverse exfoliation techniques

Abstract

We report the reproducible synthesis of ultraviolet (UV) photoluminescence (PL) emission from tellurium nanosheets (TeNS) through three distinct top-down exfoliation methods, probe sonication, cryo-assisted synthesis and shear-induced fracturing. Despite differing synthesis processes, all approaches yield few-layer thick (0.6–6.4 nm) TeNS with consistent structural integrity and prominent UV emission centred at 340 nm (3.65 eV). Systematic optical characterisation reveals transitions from p-bonding triplets to p-antibonding triplets, manifested as two characteristic absorption peaks around ~ 230–240 nm (5.16–5.39 eV) and ~ 270–280 nm (4.43–4.60 eV). XRD and Raman studies confirm the crystalline features of TeNS, while FTIR spectra indicate surface/ edge hydroxylation, which enhances their dispersion stability in an aqueous medium. The method-independent reproducibility of UV emission can be attributed to the surface states influenced by hydroxyl functionalisation rather than arising from the intrinsic bandgap of TeNS. These findings suggest solution-processed TeNS as UV emitters with potential for optoelectronic applications.