In The last years, nanostructures of materials, as the porous silicon nanowires (PSiNWs), have been used extensively studiedfor the development of several chemical, electro-chemical and biologic sensors, because of their physical and chemicalcharacteristics. The PSiNWs present a unique property, like the biocompatibility and the multifunctional. The PSiNWs canbe elaborated from lightly n-type (100) silicon substrate by Ag assisted chemical etching method. The obtained surfaces weregrafted with organic functional groups; first, we proceed by the grafting of acid monolayer on hydrogenated PSiNWs surfaceby hydrosylilation reaction to form Si-C covalent bond. Then, a reactive ester is generated from the terminal acid groups andsubsequently this activated surface is coupled with peptide containing amines by the formation of amide bond. This strategyis based on that used for the immobilization of biomolecules (DNA, proteins, antibodies ...) to elaborate biosensors [1-3]. Ateach step of the modification, the resulting surfaces were characterized by X-ray photoelectron spectroscopy (XPS). Differentcharacterization techniques were used to investigate the resulting nanostructures, such as SEM, XPS, FTIR and electrochemicalmeasurements.Finally, the obtained results can find application in low-cost and high efficiency porous silicon nanowires based applicationswere envisaged in environmental area. The obtained hybrid structure was tested as probe electrode to the electrochemicaldetection of mercury in solution.