I want to perform SERS for bacteria, i want to know what should be the ideal size of Au or Ag nano-particles which can create optimum plasmonic effect considering also the stability of the particles.
Dear Priyanka Mishra,
The optimum size and inter-particle gap between plasmonic nanoparticles (Ag and Au NPs) required for better SERS effect have been reported theoretically and experimentally by many researchers. Theoretically, the SERS enhancement increases with increase in particle size of Ag NPs; however, the SERS effect decreases for higher particles size beyond 50 nm. Experimentally, the optimum particle size for better SERS effect is also up 40-50 nm. The inter-particle gap plays a major role for SERS effect. The tuning of inter-particle gap among the NPs in the regime of 10 nm, mostly 1-4 nm gap is a critical value for higher SERS enhancement. If you are using NPs in colloidal form, the above particle size may be considered. And if you are using a thin film of NPs, then you need to look into particle size as well as inter-particle gap.
Dear Anil,
Thanks for this information, i would like to know if i want to have glass slide with SERS active spot ( may be of Au or Ag) what do you think should be diameter of the particles and inter particles gap. I am not sure if it is same like having a thin film of NPs.
Dear Priyanka,
For a thin film, the better size of the NPs (Ag and Au NPs) could be between 20-40 nm, not beyond 50 nm and may be below 20 nm. And, the inter-particle gap among the NPs must be below 10 nm.
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