Graded Nanowell Arrays: Fine Plasmonic “Library” with Adjustable Spectral Range
We present an effective approach for fabricating graded plasmonic arrays based on ordered micro-/nano-structures with geometric gradient. Ag nanowell arrays with graded geometric parameters were fabricated and systematically investigated. The order of the graded plasmonic arrays is generated by colloidal lithography, while geometric gradient is the result of inclined reactive ion etching. The surface plasma resonance (SPR) peaks were measured on different positions, which move gradually along Ag nanowell arrays with geometric gradient. Such micro-/nano-structure arrays with graded and integrated SPR peaks can work as a fine plasmonic “library” (FPL), and the spectral range can be controlled by “coarse adjustment knob” (lattice constant) and“fine adjustment knob” (pore diameter). Additionally, the spectral resolution of FPL is high, which benefits from the high value of full height/full width at half-maximum and small step size of wavelength shift (0.5 nm). Meanwhile, the FPL could be effectively applied as a well-defined model to verify the plasmonic enhancement in surface enhanced Raman scattering. As the FPL is an integrated optical material with graded individual SPR peaks, it can not only be a theoretical model for fundamental research, but also has great potential in high-throughput screening of optical materials, and multiplex sensors, etc.