Aging Induced Ag Nanoparticle Rearrangement under Ambient Atmosphere and Consequences for Nanoparticle-Enhanced DNA Biosensing

摘要

Localized surface plasmons of metallic nanoparticles cannstrongly amplify the magnitude of the surrounding electricnfield. This in turn enhances fluorescence from nearbynfluorophores. However, little is known regarding howntime-dependent changes in nanoparticle structure due tonexposure to the ambient environment affect their behaviornin plasmonic devices. Here, we report the interestingnfinding that the aging of a nanostructured Ag substrate innambient atmosphere markedly improves the fluorescencensignal of a plasmonic-based DNA detection system. Theneffect can be observed with an exposure time as short asntwo days, and a nearly 17-fold signal enhancement cannbe achieved with 30 days of aging. Analysis of substratensurface topography by atomic force microscopy (AFM)nreveals a substantial change in nanoparticle morphologynas the substrates age despite being covalently attached tona solid dry substrate. Nanoparticle morphological changesnalso manifest in extinction spectra. This process can benfurther accelerated by light. Together, our findings addressnthe important question of Ag nanoparticle stabilitynover time and its potential ramifications for plasmonenablednsensors. They also imply that nanoparticle agingnmay be used strategically to tune nanoparticle size andngeometry and plasmon spectrum, which may be beneficialnfor studies on plasmonics as well as sensor optimization.