  We investigate the time-dependent electronic transport in single-walled
carbon nanotubes (SWCNTs) functionalized with Au clusters on CO gas exposure.
Using a tight-binding Hamiltonian and the nonequilibrium Green's function
(NEGF) formalism the time-dependent zeroth and first order contributions to the
current are calculated. The zeroth order contribution is identified as the
time-dependent Landauer formula in terms of the slow time variable, whereas the
first order contribution is found to be small. The Green's function for the
SWCNT is derived using the equation of motion and Dyson equation technique. The
conductance is explicitly evaluated by considering a form for the hopping
integral which accounts for the effect of dopants on the charge distribution of
the carbon atoms and the nearest-neighbor distance. The effect of dopants is
also studied in terms of fluctuations by calculating the autocorrelation
function for the experimental and theoretical data. These calculations allow
direct comparison with the experiment and demonstrate how the presence of
dopants modifies the conductance of the SWCNT measured experimentally and
provide the only study of fluctuations in the sensor response in terms of the
autocorrelation function.
