Unique molecular identification using two-dimensional response

Nanostructured graphite (NG) layer prepared through mechanical abrasion on a variety of substrates has been investigated as a highly sensitive, versatile, and low-cost sensing material. NO₂ concentration down to 60 ppb was detected in ambient conditions using the NG layer. Simultaneous conductance (G) and surface work function (phi) change transients measured using the NG layer indicated much faster response for the later, which is attributed to its dependence solely on molecular adsorption at the surface. Simultaneous measurements of these two parameters have been performed to detect several gaseous analyte molecules, and it was observed that the gradient of Deltaphi versus DeltaG/G₀ plot for a specific analyte molecule is constant irrespective of its concentration or fractional occupancy of the surface adsorption sites. Changes in phi and G were found to be uncorrelated for different molecules resulting in unique gradients that can be used as 2-dimensional signatures for molecular identification.