Efficient Upconverting Multiferroic Core@Shell Photocatalysts: Visible-to-Near-Infrared Photon Harvesting

We report the two-step synthesis of a core@shell nanohybrid material for visible-to-near-infrared (NIR) photocatalysis. The core is constituted of NaGdF₄:Er³⁺, Yb³⁺ upconverting nanoparticles (UCNPs). A bismuth ferrite (BFO) shell is assembled around the UCNPs via a hydrothermal process. The photocatalytic degradation assays of methylene orange and 4-chlorophenol reveal that these core@shell nanostructures possess remarkably enhanced reaction activity under visible and NIR irradiation, compared to the BFO powder alone and the BFO-UCNP mixture. Photo-charge scavenger tests and fluorescent assays indicate that hydroxyl radicals play a pivotal role in the photodegradation mechanism. The enhanced photoactivity of the core@shell structure is attributed to the NIR radiation which is converted into visible light by UCNPs, and which is then captured by BFO via a nonradiative luminescence resonance energy transfer process. Therefore, this core@shell architecture optimizes solar energy use by efficiently harvesting visible and NIR photons.