Fig. 4. Nanorectangle (NR) performance comparison with a circular zero-mode waveguide (ZMW) nanoaperture for the UV fluorescent dye p-terphenyl. Here the NR size is 60 × 45 nm2 and the ZMW diameter is 70 nm. Both are milled in the same 50 nm thick aluminum layer deposited on quartz substrate. (a) Absorption and emission spectra of p-terphenyl (shaded curves). The curves for the ZMW and NR indicate their computed transmission spectra (normalized at by the peak transmission). The 310–410 nm region used for fluorescence collection is indicated. (b) FCS correlation traces for the NR and ZMW taken at 10 μM concentration in ethanol solution with 40% glycerol. The confocal reference data is recorded at 290 nM and multiplied by 10 for clarity. The insert shows the amplitude-normalized correlations, indicating a clear shortening of the diffusion time in the NR. Black lines are numerical fits; the results are summarized in Table 3. (c) Fluorescence lifetime decay traces for the different cases, together with the instrument response function (IRF). Again, the black lines are numerical fits; the results are summarized in Table 4. (d) Average brightness per molecule measured by dividing the average fluorescence intensity by the number of molecules monitored by FCS in (b). (e) Fluorescence lifetime extracted from the data fits in (c). For the ZMW and the NR, the lifetime of the second component is shown as it is the one representative of the nanostructure influence.
