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(Color online) (a) Spectral sensitivity vs the angle of incidence for 2D nanohole array SPR sensor for different SPP modes by employing SPP dispersion relation to a periodicity of . Refractive index change from 1.32 to 1.36 was used to extract the sensitivities from the shift of SPP mode resonant wavelength. Discrete points show the spectral sensitivity obtained from using RCWA applied to transmission through a one-dimensional metallic grating with the same parameters of periodicity and refractive index change; duty ratio of the hole is chosen to be 0.2. (b) Dispersion relationship of SPP liquid-metal modes to reveal the relation between SPP excitation wavelength and the angle of incidence for a fluid refractive index of 1.32. For clarity, higher order SPP modes are not shown. The pink belt shows the wavelength range of current setup from . Dash-dot lines indicate the angles of incidence, at which or (1, 0) liquid-metal SPP modes are excited at a wavelength of .
(Color online) (a) SPP resonant wavelength evolves with time to calibrate the sensitivity of the nanohole array SPR sensor. The ethylene glycol water solutions with different concentrations in volume (V/V) flow through the channel on top of the Au nanohole array with periodicity and hole size. The blue and red curves correspond to (1, 0) and SPP modes, respectively, with angles of incidence of about 9 and from the normal of the array surface. (b) SPP resonant wavelength vs the refractive indices of the corresponding solutions. The solid lines are linear fits for the (1, 0) mode and modes, respectively.
(Color online) (a) Schematic illustration of label-free, real-time nanohole array SPR biosensor. The SPP resonant wavelength is extracted and plotted to show real-time measurement. A nanohole array is also shown. (b) SPP resonant wavelength evolves with time to monitor the process of a series of biological reactions from surface cleaning, protein attachment, and specific binding.
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