It's hard to say something. Nanoparticles show an intrinsic stretching vibrations of the metal at the tetrahedral site (e.g. for a spinel particle) and this is generally observed at 500-600 cm-1. Peaks at the same region can be seen on your graphs but they can not be treated as a "clear evidence" for your experiment. In order to be sure, it must not be forget to deal with more experimental probes like XRD, SEM and TEM if you have opportunity to work on these facilities.  

This discontinuities are connected with changes of lamp, internal filters, detector in your instrument and are not true absorbance features.

Thanks for your inputs, I'll find more sophisticated UV vis spectrometer.

1. You have instrumental errors.

2. AnNPs depict a characteristic surface plasmon resonance band in the visible region (e.g. 480 nm), depending on the size and quality of the nanoparticles.

Dear Ammar, as i am seeing your result, no intense peak is observed. Generally, Ag nanoparticles exhibit peak in the range of 400 - 500 nm depending upon size of the particles. What i can suggest you is to calibrate the instrument or you can use some other good quality UV-Vis Spectrophotometer. If still the problem persists, then you have to modify your synthesis protocol.

Thanks for your inputs 

Dear Ammar

Follow the Kumar suggestion, but If still the problem persists, then use very dilute solution from the freshly prepared silver nanoparticles.

Thanks dear Ismail.

Welcome