Dual LSPR of Au/W18O49 heterostructures for upconversion enhancement and application of molecular detection†
A nano-heterostructure composed of the noble metal Au and the semiconductor W18O49 enhances the localized electric field due to the strong coupling of localized surface plasmon resonance (LSPR). The Au/W18O49 nano-heterostructures have been further explored to enhance the upconversion luminescence (UCL) of NaYF4:Yb,Er nanoparticles. An enhancement up to 1108-fold is achieved for the overall UCL intensity of Er3+, which is primarily due to the improvement of the excitation field and partly due to the coupling of LSPR with emission light. Finally, based on the intense UCL caused by the excellent synergetic LSPR, a dual detection method of qualitative before quantitative detection of rhodamine 6G (R6G) using SERS signal monitoring and fluorescence sensing is established. This novel detection method with a high sensitivity of 10−11 M (100 aM), a good linear relationship and a wide concentration range of 10−11 M to 10−3 M can potentially be applied in accurate molecular detection.