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In this study, a composite silver nanostructure is presented to serve as the platform for highly efficient plasmon-enhanced fluorescence (PEF). The composite nanostructure is realized by first employing nanosphere lithography (NPL) combined with reactive ion etching (RIE) technology to create a silver nanopyramid array, which is then further modified with silver nanoparticles. Utilizing DCJTB as the fluorophore, this composite nanostructure is found to outperform the use of either silver nanoparticles or silver nanopyramid array. Notably, it not only enhances the photoluminescence (PL) but also reduces the carrier lifetime. The influence of the particle size of silver nanoparticles and the height of the silver nanopyramids is also investigated. It is found that larger silver nanoparticles and higher silver nanopyramids lead to stronger local surface plasmon resonance (LSPR), thereby enhancing the PEF phenomenon. Compared with the performance of using bare glass substrate, the PL intensity of using the composite nanostructure is enhanced to 19.4 times and the carrier lifetime is shortened by 61%.

The field of plasmonic sensing has witnessed rapid advancements in recent years. This work proposes an innovative methodology that employs metal–insulator-metal (MIM) nanohole arrays integrated with ring-shaped silver nanoparticles (AgNPs) to serve as an effective plasmonic refractive index sensor. The hybrid substrates are prepared using a combination of nanosphere lithography (NSL), reactive ion etching, and an enhanced plasmonic site-selective photocatalytic reaction, ensuring large-area fabrication, high throughput, and cost-effectiveness. The resonance peaks observed in the visible-NIR spectra are attributed to the coupling of surface plasmon resonance modes between MIM structures and AgNPs. The resonance wavelength exhibits sensitively to changes in the surrounding medium within the refractive index range of 1 to 1.5, with a remarkable sensitivity of 835 nm/RIU. Our findings reveal the significant potential of this technology for advancing optical sensing applications.