Thiol-capped nanoparticles are used as conducting filler for poly dimethylsiloxane matrix in detection of organic vapors. In this paper, we describe a method for preparing alkanethiol based monolayer protected clusters (MPCs) of gold (Au), silver (Ag), bimetallic (Au-Ag) nanoparticles of various compositions and different aspect ratios of Au, Ag and core-shell structures of (Au)Ag & (Ag)Au nanorods were studied. Because of the variety of functional groups that can be supported using MPCs techniques and due to the relative stability of the monolayer generated, we believe these materials will be useful for developing chemical and gas sensors.. Thin films of nanocomposite is deposited on the interdigitated microelectrodes (IDE) thus forming “chemiresistors” and are analyzed by exposing to different analytes (N-methyl pyrolidine, tetrahydrofuran, methyl ethyl ketone, and toluene) at very low concentration and different relative humidity (RH%). The chemo resistive response is measured by four probe method for different analytes at different concentrations and the result shows a linear profile of concentration of analyte vs. conductivity at different RH%. The response time and percolation threshold vs. conductivity of this novel chemiresistor compares favorably over conventional carbon black (CB) polymer composite.