Au–Ag hollow nanostructures with tunable SERS properties

• Fabrication of hollow Au-Ag nanoparticles is done by the sequential action of galvanic replacement and Kirkendall effect.
• Methodical examination of the SERS enhancement is carried out with these plasmonic nanostructures as substrates and Nile blue chloride (NBC) and Crystal violet (CV) as probe molecules.
• NBC molecules showed a 10-fold increase in enhancement than CV molecules. The SERS enhancement is found to be highly sensitive to the size of cavities and substrates with small cavities shows large enhancement.
• Against all the nanotags fabricated, the Raman enhancement is calculated and it was in the order of ~ 106 and 105 for NBC and CV molecules respectively.
• It is found that it possible to tune the Raman enhancement factor by carefully controlling the size of cavities.
• The enhancement observed for substrates with large cavities is of interest since nowadays Au protected hollow nanostructures are vital and an active area of research in drug delivery systems.

Fabrication of hollow Au–Ag nanoparticles is done by the sequential action of galvanic replacement and Kirkendall effect. Polyol synthesized silver nanoparticles were used as templates and the size of cavities is controlled by the systematic addition of the HAuCl4. Au–Ag nanoparticles carved in different depths were tested for application as substrates for surface enhanced Raman scattering. Two medically important Raman active analytes-Nile blue chloride and Crystal violet were used in the surface enhanced Raman scattering (SERS) performance analysis. A systematic study has been made on the Raman enhancement of hollow nanoparticles fabricated with different cavity dimensions and compared with that of the silver templates used. The enhancement observed for these hollow substrates with cavities is of interest since Au protected hollow nanostructures are vital and an active area of interest in drug delivery systems.

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