Before going to take spectra of nanoparticles, took spectra of your starting materials. I think this is region of your reactant absorbance otherwise it will be Ag2O.
The UV-vis peak position of AGNPs depends on particles size, shape, concentration, synthetic methods, used reducing agents, solvent, capping agents etc. Generally the UV-vis peak of AgNPs appears at around 390 to 450 nm. You did not mention how did you synthesize AgNPs. What were the reducing and capping agent? Almost same question arises by Md. Sayedur Rahman in researchgate 3 years ago. Please see the discussion:
Before going to take spectra of nanoparticles, took spectra of your starting materials. I think this is region of your reactant absorbance otherwise it will be Ag2O.