Enhanced photoluminescence of DCJTB with ordered Ag-SiO₂ core–shell nanostructures via nanosphere lithography

We have fabricated Ag-SiO₂ core–shell nanostructure set in the hexagonally ordered Ag nanohole array by nanosphere lithography with reactive ion etching, and followed by Ag deposition. The resulting nanostructure includes the triangular-shaped plates with sharp edges on the top, the Ag-SiO₂ core–shell nanospheres, the hexagonally arranged nanohole array, a SiO₂ buffer layer and a DCJTB (4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran) fluorescent dye layer, respectively. Six patterns of substrates (i.e., Types 1–6) were fabricated and their photoluminescence enhancement performance was compared to substrate layered with pure DCJTB. The experimental results show that photoluminescence enhancement can be 15.69 times, and the lifetime can be shortened from 0.97 ns to 0.41 ns for Type 3 when compared to the pure DCJTB one. The finite element method revealed four structure conditions which are the effects of edge enhancement, gap plasmon resonance, hollow plasmon resonance, and core–shell hybridization plasmon resonance and can contribute to the photoluminescence enhancement factor. The proposed substrates provide a practical detecting platform with plasmon-enhanced photoluminescence, and the fabrication methods used are technically simple and low cost.