Near‐Infrared‐Plasmonic Energy Upconversion in a Nonmetallic Heterostructure for Efficient H ₂ Evolution from Ammonia Borane

Abstract

Plasmonic metal nanostructures have been widely used to enhance the upconversion efficiency of the near‐infrared (NIR) photons into the visible region via the localized surface plasmon resonance (LSPR) effect. However, the direct utilization of low‐cost nonmetallic semiconductors to both concentrate and transfer the NIR‐plasmonic energy in the upconversion system remains a significant challenge. Here, a fascinating process of NIR‐plasmonic energy upconversion in Yb ³⁺/Er ³⁺‐doped NaYF ₄ nanoparticles (NaYF ₄:Yb‐Er NPs)/W ₁₈O ₄₉ nanowires (NWs) heterostructures, which can selectively enhance the upconversion luminescence by two orders of magnitude, is demonstrated. Combined with theoretical calculations, it is proposed that the NIR‐excited LSPR of W ₁₈O ₄₉ NWs is the primary reason for the enhanced upconversion luminescence of NaYF ₄:Yb‐Er NPs. Meanwhile, this plasmon‐enhanced upconversion luminescence can be partly absorbed by the W ₁₈O ₄₉ NWs to re‐excite its higher energy LSPR, thus leading to the selective enhancement of upconversion luminescence for the NaYF ₄:Yb‐Er/W ₁₈O ₄₉ heterostructures. More importantly, based on this process of plasmonic energy transfer, an NIR‐driven catalyst of NaYF ₄:Yb‐Er NPs@W ₁₈O ₄₉ NWs quasi‐core/shell heterostructure, which exhibits a ≈35‐fold increase in the catalytic H ₂ evolution from ammonia borane (BH ₃NH ₃) is designed and synthesized. This work provides insight on the development of nonmetallic plasmon‐sensitized optical materials that can potentially be applied in photocatalysis, optoelectronic, and photovoltaic devices.