NANOELECTRONIC CHEMICAL SENSORS FOR CHEMICAL AGENT AND EXPLOSIVES DETECTION

A new class of nanometer-scale, low power, solid-state devices is being investigated for the detection of CW agents and other hazardous vapors. These nanoelectronic chemical vapor sensors, or "chemiresistors" are comprised of nanometer-sized gold particles (1.2-2.4nm) encapsulated by monomolecular layers of functionalized alkanethiols (R-SH) deposited as thin films on interdigitated microelectrodes. When chemical (agent, explosive) vapors reversibly absorb into these thin films, a large modulation of the electrical conductivity of the film is observed. The measured current between gold clusters is extremely sensitive to very small amounts of monolayer swelling or dielectric alteration caused by absorption of vapor molecules. For chemical agent simulants, a large dynamic range (5-logs) of sensitivities is observed and extends down to ppb (parts-per-billion) vapor concentrations. For explosive vapors of TNT/DNT detection limits in the femtogram range have been observed. Complete reversibility has been observed for all analyte vapors and the devices exhibit relatively low sensitivity to water vapor (a major interferent). Tailored selectivities of the sensors are accomplished by incorporation of chemical functionalities at the terminal structure of the alkanethiol or substitution of the entire alkane structure.