Physical and chemical characterization of PANI/SiO2/MPS heterostructure to be used as high sensitivity chemosensor for naphthalene

Abstract Macroporous silicon layer was passivated by chemical oxidation and then polyaniline was deposited chemically within the porous structure in order to fabricate a heterostructure to be used as chemical sensor. The structural characterization of this device by scanning electron microscopy reveals the effectiveness of the chemical method for polyaniline deposition in oxidized porous matrix. The analysis by AT-FTIR and Raman spectroscopy shows that polyaniline was deposited in its emeraldine state, which is the most conductive phase, forming a well-defined replica of the porous structure. However, according to the EDS analysis, this polymer layer is non-homogeneous in depth. This feature was also confirmed by electrical measurements of current-voltage and electrochemical impedance at different points between the polymer surface and silicon substrate. In spite of this fact, the immersion of this structure in an ethanolic solution containing low amounts of naphthalene shown that this structure is excellent to be used as chemical sensor for the detection of low concentrations of naphthalene in the order of 30 ppb.