Fabrication and characterization of carbon nanoparticles for polymer based vapor sensors

The working principle of composite polymer vapor sensors is basically to exploit the vapor absorption properties of an insulating polymer whose electrical properties are modulated by a conductive “filler”. Carbon black and graphite powder have already been used as “filler” materials [Sens. Actuators B87 (2002) 130, Anal. Chem. 74 (2002) 1307, Sens. Actuators B66 (2000) 37, Anal. Chem. 70 (1998) 2560]. In this work we fabricate and characterize vapor sensors with a new type of “filler”: carbon nanoparticles obtained by flame synthesis. Electrochemically prepared porous silicon with a 40% porosity has been used as the substrate for the carbon growth. Carbon nanoparticles have been characterized by AFM, SEM, FTIR; XRD, diffraction laser spectroscopy, nitrogen isothermal adsorption and visible optical micrography. The carbon structures seem composed of “units” whose size is in the range 5–20 nm. Composite thin films have been realized using mainly poly(methyl-methacrylate) (PMMA) as polymeric insulating matrix. Thin films of the composite are used to realize chemiresistor sensing devices. The characteristics of the sensors responses to volatile organic compounds (VOCs) are related to filler types in order to optimize the sensing device and show the importance of the filler characteristics.