Dual-Functional Nonmetallic Plasmonic Hybrids with Three-Order Enhanced Upconversion Emission and Photothermal Bio-Therapy

Plasmonic semiconductor nanoparticles (NPs) with wide-range tailorable localized surface plasmon resonance (LSPR) hold exciting prospects on optical signal amplification. In this work, by precisely controlling oxygen vacancies around W atoms, plasmonic bismuth tungstate Bi₂WO₆ (BWO) nanosheets are constructed to enhance emission of Yb³⁺/Er³⁺ co-doped NaYF₄ upconversion nanoparticles (UCNPs). In the optimal conditions, the UCNPs/BWO-2 hybrids exhibit over three-order (1260-fold) enhancement selectively on the 520 nm emission owing to the strong LSPR-induced electrical field and photothermal effect. Moreover, it is found that the highly efficient emission of UCNPs/BWO-2 allows it to act as a thermometer to monitor the real-time local temperature with high absolute sensitivity of 5.8 × 10⁻³ K⁻¹ in wide temperature range (up to 990 K). For proof-of-concept, the dual functions of plasmonic UCNPs/BWO-2 hybrids on bioimaging and photothermal therapy for cancer cells are demonstrated that can be completely killed within 5 min under 980 nm irradiation. As far as it is known, this work reaches a new level on UCNPs emission enhancement by plasmonic semiconductor, exceeding most plasmonic metals.