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Supporting InformationFigure S1: Raman spectra of graphene and graphene/AuNPs using a 633 nm laser for excitation.Figure S2: Enlarged SEM image of AuNPs on graphene.37528502322195a00a 36957002254885b00b 36099752305050c00cFigure S3: Simulation results detailing the electric field magnitude along the plane on which the graphene and AuNP rest upon. This figure is the separate sets of data from figure 3d, (a) is from a simulation only using the AuNP, (b) is from a simulation using 2 nm of R6G in the gap between the nanoparticles with graphene underneath, and (c) is from a simulation where only the AuNP and graphene were present on the substrate.SI4: Further Sensitivity AnalysesFigure S4: A comparison of the Raman spectra of R6G at 10-5 M and 10-6 M under four sets of conditions. The upper-left corner indicates the general morphology of the substrate, gold nanoparticles (AuNP) on graphene (G) or vice versa. The upper-right corner indicates with which laser energy the scan was carried out. X-axis ranges are the same for all spectra, while each laser energy has the same y-axis range.These scans were carried out using moderate intensity (more than half way to full attenuation of the beams). Each spectrum seen in figure S4 is an average of six spectra. These six spectra were scanned using 3-second integration and averaging 20 accumulations. The laser spot was moved between each scan in order to avoid the change to the R6G concentration by shining a laser on the R6G droplet. Lowering the R6G concentration by an order of magnitude to 10-7 resulted in no discernable signal being seen in the acquired Raman spectra.Originally, our hypothesis was that the graphene being on top would give the biomolecules more surface area to adsorb to, and that the AuNP being so close to the R6G molecules would enhance the signal a greater amount than with graphene under the AuNP. However, as can be seen by our results, it is the opposite. The signal appears to decrease when using graphene on top of AuNP although not to an enormous extent (less than a factor of 2 for most peaks) (Fig S5)Figure S5: Comparison of the 10-5 M R6G spectra excited with 633 nm light with different surface conditions. ................
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