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. 2011 May 2;108(20):8157–8161. doi: 10.1073/pnas.1016530108

Fig. 2.

Fig. 2.

Optical properties of the nanorod supercrystals. (A–C) Optical, SEM, and dark-field images of an NR supercrystal, respectively, after plasma-etching removal of surfactant coating of the NRs. (D) Localized surface plasmon resonance bands of the rods in solution (gray) and within a supercrystal, either at the center or at the edges (red and black boxes of Fig. 2C, respectively) . Dotted arrows indicate the excitation laser lines used for SERS. (E and F) Electric field enhancement maps calculated for the top part of a three layer rod-stacked supercrystal (E) and for the same location in a single monolayer (F). (G–J) SERS intensity maps at 1,072 cm-1 (BT ring breathing) corresponding to the supercrystal in A, for BT as excited with a 633 (G), 785 (H), and 830 nm (I) laser lines, representative SERS spectra for each laser being presented in J. (K) Comparison of the SERS intensities at 1,072 cm-1 provided by a gold rod supercrystal (Au-RSC) film with common SERS substrates, including aggregated ultralong nanowires (Au-NW), single rods, parallel and fractally aggregated gold NRs (Single Au-NR, Parallel Au-NR, and Fractal Au-NR, respectively). The intensity is the result of averaging over 50 different randomly distributed spots in the supercrystal and those corresponding to maximum intensity for the rest of substrates. More information about the different substrates can be found in the Supporting Information.