2: It is quite standard to use a calibration curve SPR value vs concentration
Please have a look our related paper and similar SPR peak with ours then you can use that calibration curve. The second approach of AgNPs evaluation is AAS. Article Antimicrobial and antioxidant activity of AgNPs stabilized w...
Article Green synthesis of silver nanoparticles using paper wasp‘s h...
I would suggest performing ICP-OES, will give you the exact concentration of Silver ions in the given solution. Based on the value, you need to prepare a working stock and you can proceed for MIC/MTT and other quantitative assay.