Near-infrared to visible photon transition by upconverting NaYF4: Yb3+, Gd3+, Tm3+@Bi2WO6 core@shell composite for bisphenol A degradation in solar light

The effective use of sunlight by photocatalyst systems is challenging. Here, we report an [email protected] nanohybrid composite that converts incompatible near-infrared (NIR) radiation to functional ultraviolet-visible (UV–vis) photons. The active core is composed of NaYF4: Yb3+, Gd3+, and Tm3+ upconverting nanoparticles (UCNPs). An inert bismuth tungstate (Bi2WO6) shell with a narrow band gap (2.65 eV) was grown over the core via ethylenediaminetetraacetic acid-metal complex formation. Solar infrared photons were successfully converted to UV–vis photons, which activated the Bi2WO6 shell via Förster resonance energy transfer (FRET). The high UV–vis-NIR response of the [email protected]2WO6 composite was demonstrated by 94% degradation of Bisphenol A in 180 min. Integrating UCNPs with Bi2WO6 resulted in a high quantum yield of 3.16 × 10−5 molecules/photon, which is superior to the yield of the photocatalysts currently used. High photocurrent density (0.78 mA/cm2) confirmed the excellent photoelectrochemical potential for water splitting. Hydroxyl radicals generated at the valence band and superoxide radicals at defect sites in the Bi2WO6 explain the excellent catalytic activity of [email protected]2WO6. A figure of merit (FOM) reflecting important operational parameters was calculated and compared with previous reports for catalytic performance evaluation. The high FOM value of the [email protected]2WO6 hybrid composite indicates its excellent potential for practical applications.