Semiconductor Plasmon Induced Up-Conversion Enhancement in mCu_2–xS@SiO₂@Y₂O₃:Yb³⁺/Er³⁺ Core–Shell Nanocomposites

The ability to modulate the intensity of electromagnetic field by semiconductor plasmon nanoparticles is becoming attractive due to its unique doping-induced local surface plasmon resonance (LSPR) effect that is different from metals. Herein, we synthesized mCu 2– x S@SiO 2 @Y 2 O 3:Yb 3+ /Er 3+ core–shell composites and experimentally and theoretically studied the semiconductor plasmon induced up-conversion enhancement and obtained 30-fold up-conversion enhancement compared with that of SiO 2 @Y 2 O 3:Yb 3+ /Er 3+ composites. The up-conversion enhancement was induced by the synthetic effect: the amplification of the excitation field and the increase of resonance energy transfer (ET) rate from Yb 3+ ions to Er 3+ ions. The experimental results were analyzed in the light of finite-difference time-domain (FDTD) calculations, confirming the effect of the amplification of the excitation field. In addition, up-conversion luminescence (UCL) spectra, up-conversion enhancement, and dynamics dependent on concentration (Yb 3+ and Er 3+ ions) were investigated, and it was found that the resonance ET rate from Yb 3+ ions to Er 3+ ions increased ∼25% in the effect of LSPR waves. Finally, the power dependence of fingerprint identification was successfully performed based on the mCu 2– x S@SiO 2 @Y 2 O 3:Yb 3+ /Er 3+ core–shell composites, the color of which can change from green to orange with excitation power increasing. Our work opens up a new concept to design and fabricate the up-conversion core–shell structure based on semiconductor plasmon nanoparticles (NPs) and provides applications for up-conversion nanocrystals (UCNPs) and semiconductor plasmon NPs in photonics.