In the present work, we had used two methods (solvothermal and seed growth methods) to sense albumin concentration based on the optical and plasmonic characteristics of Au/Ag nanocrystallites and their interaction with bovine serum albumin (BSA). They were studied using UV-Vis spectroscopy, transmission electron microscopy (TEM) techniques. The obtained results indicated that the good interactions between nanocrystallites and BSA happen. With the help of changes in plasmonic peaks and comparison of TEM images before and after the interaction for different concentrations of albumin samples, we had obtained a qualitative method of identifying albumin (down to 0.2 mg/ml) concentration.