Electrochemical sensor of organics pollutants based on polythiophene and silicon nanowire

Hybrid devices based on silicon nanowires (SiNW) and polythiophene (PTh) as conductive polymer was prepared by electrochemical way and was used as working electrodes to investigate the redox behavior of para-nitrophenol... [ view full abstract ]

Hybrid devices based on silicon nanowires (SiNW) and polythiophene (PTh) as conductive polymer was prepared by electrochemical way and was used as working electrodes to investigate the redox behavior of para-nitrophenol (p-NPh), phenol and aniline by cyclic voltammetry (CV). p-NPh, phenol and aniline are common organic pollutants found particularly in the effluents from pesticides, pharmaceuticals, petrochemicals and other industries. Owing to their toxicity and reactivity, there is an urgent to develop analytical and simple devices to monitor these pollutants for environmental control and protect human health. SiNW-based sensor devices have gained considerable interest as a general platform for sensors. Metal-assisted chemical etching has successfully been applied for the fabrication of large-area aligned SiNW arrays on single crystal silicon wafers. It is simple and fast method. Hydrogen-passivated surface of SiNW shows a poor stability in water [1]. Surface modification with organic species confers the desired stability and enhances the surface properties. For this reason, this work proposes a covalent grafting of organic conductive polymer such as PTh onto SiNW surface. The choice of conductive polymer allows an improvement of interfacial charge transfer ensuring continuity in the conduction mechanism for a better detection. PTh was covalently grafted on SiNW surface using an electrochemical polymerization which offers several advantages such as simplicity and rapidity. The sensitivity of hybrid structure to different concentration of para-nitrophenol, phenol and aniline was studied by cyclic voltammetry in buffer PBS solution and in p-NPh/PBS, phenol/PBS and aniline/PBS solutions. Figure 1 shows a set of cyclic voltammograms recorded at 50mVs−l, between -1 and 2V in PBS solution for different concentrations from 1.5×10−8 to 1.5×10−4M of p-NPh. In order to check the surface after the electrodetection, the SEM morphology of SiNW/PTh surface was observed after applying a complete cycle.