engleski

Hollow metal island films as plasmonic sensors produced by galvanic replacement

Hollow nanoparticles show enhanced plasmonic response with respect to their solid counterparts. Formation of hollow nanostructures is usually carried out in nanoparticle solutions via galvanic replacement and Kirkendall effect driven by the redox potential difference between metals of a redox couple. In this work, the formation of hollow nanoparticle layers using metal island films fabricated by physical vapor deposition as templates is demonstrated. Ag metal island films on glass and silicon substrates are titrated with a solution containing tetrachloroauric acid as oxidizing agent. The islands morphology and their plasmonic properties gradually change with the increase of titration solution concentration due to the effects of galvanic replacement. In comparison to untreated samples, a four-fold enhancement of the refractive index sensitivity factor (360 nm/RIU vs 92 nm/RIU) and two and a half times increase of the figure of merit (1.37 vs 0.56) are observed for hollow island films obtained with large titration concentration. The presented approach merges the advantages of large area coverage and high particle density of island films with the plasmonic properties of hollow nanoparticles in a straightforward way that is suitable for cost-effective fabrication of plasmonic sensors.

Hollow nanoparticles ; Plasmonics ; Metal islands ; Refractive index sensors ; Galvanic replacement

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