As title suggests, can anyone explain what's the phenoma behind this? I know that I should be getting better SERS signal with dried samples (to promote analyte/nanoparticle proximity), but what is happening is that I can guarantee much better peak intensity and reproducibility while a droplet is formed.
I also tested on a passive substrate vs. my active (SERS) substrate, in the same measurement conditions, to make sure what I'm getting is indeed SERS signal, rather than normal Raman signal, as suggested in the attached figure (following Rhodamine 6 G 1510 cm-1 peak).
Thanks for your time!
You have to show us Raman and SERS spectra in a drop and in a dry state. 4 of the spectrum.
Dear Nuno,
1) please, specify substrate, rhodamine concentration, laser, and spectrometer you used.
2) it would be better if you could subtract the fluorescence background from your spectra - they will be easier to compare.
3) your SERS spectrum of R6G is not particluarly good, why peaks at 1312 and 1362 cm-1 are overlapping? they usually form nice instantly recognizable doublet.
As for the question - it is not surprising, because you have more active nanostructures (hot spots) in laser waist in droplet, than in laser focus on the dried substrate. Substrates are usually dried because of the required storage stability, not because of "proximity" (good SERS reporters are almost immediately adsorbed onto the nanoparticles anyway).
Hey Andrei,
I'm using bacterial cellulose substrates with in situ silver nanoparticles, so the aditional peaks come from the substrates signal itself. Rhodamine is 10^-6 M in this example, but the results are similar with lower concentions (up to 10^-11 M, being my LOD). Laser im using is the 633nm one.
The idea of the spectrum on the right is to show that I only get signal from the cellulose substrate, that's why i didnt subtract the baseline.
On the dried samples, the peak at 1510 cm-1 is gone.
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