Surface plasmon resonance properties of silver nanoparticle 2D sheets on metal gratings

Abstract

Grating-coupled propagating surface plasmons associated with silver-nanoparticle 2D crystalline sheets exhibit sensitive plasmonic resonance tuning. Multilayered silver-nanoparticle 2D crystalline sheets are fabricated on gold or silver grating surfaces by the Langmuir- Blodgett method. We show that the deposition of Ag crystalline nanosheets on Au or Ag grating surfaces causes a drastic change in propagating surface plasmon resonance (SPR) both in angle measurements at fixed wavelengths and in fixed incident-angle mode by irradiation of white light. The dielectric constant of the multilayered silver nanosheet is estimated by a rigorous coupled-wave analysis. We find that the dielectric constant drastically increases as the number of silver-nanosheet layers increases. The experimentally obtained SP dispersions of Ag crystalline nanosheets on Au and Ag gratings are compared with the calculated SP dispersion curves. The drastic change in the surface plasmon resonance caused by the deposition of Ag-nanoparticle 2D crystalline sheets on metal grating surfaces suggests the potential for applications in highly sensitive sensors or for plasmonic devices requiring greatly enhanced electric fields.

Keywords: Localized surface plasmon; Nanosheet; Propagating surface plasmon; Silver nanoparticles.

Figure 1

Schematic of the nanosheet silver nanoparticles on a metal grating surface.

Figure 2

Grating-coupled angular SPR reflectivity curves for multilayered AgMy nanosheets on a gold grating film measured at 632.8 nm, 594 nm, and 543 nm.

Figure 3

Grating-coupled angular SPR reflectivity curves for multilayered AgMy nanosheets on a silver grating film measured at 632.8 nm, 594 nm, and 543 nm.

Figure 4

Plots obtained from SPR reflectivity curves on gold and silver grating films. (a) Shifts in SPR dip angle. (b) Dielectric constant of AgMy nanosheet as a function of the number of layers.

Figure 5

SPR reflectivity curves from a bare Au grating (top) and from three AgMy nanosheet layers on the Au grating (bottom) at fixed angles from 20° to 70° as a function of wavelength.

Figure 6

SPR reflectivity curves from a bare silver grating (top) and from three AgMy nanosheet layers on the Ag grating (bottom) at fixed angles from 20° to 70° as a function of wavelength.

Figure 7

Reflectance curves from one to three AgMy nanosheet layers on the flat Au at fixed angles of 20° and 70° as a function of wavelength at p-polarization.

Figure 8

Experimental dip angles (symbols) and calculated SP dispersion branches (solid lines). (a) on the Au grating. (b) on the Ag grating.