Biosensors are hot topic in recent years because of their versatility to different fields. Porous silicon devices are optical transducer sensitive to biological and chemical species which penetrate inside the pores after a proper functionalization with specific bioprobes. In this work, we reported a functionalization approach to obtain optical biosensors for heavy metal detection. Oligopeptides, namely Phytochelatins, were selected due to their ability to detect heavy metal ions. Spectroscopic reflectometry and Fourier transform infrared spectroscopy were used as characterization techniques. Data show successful and repeatable functionalization process. These results are very good starting step in development of heavy metal ions optical biosensors.