(with the same dye solution concentration and uniform NiO
films). The plots recorded the normalized absorption of various
dyes in the solution at their peak wavelengths. By fitting these
curves with an exponential decay equation ( A = a exp(−( t/
τ))), the time (τ) for a saturated adsorption can be estimated to
be 68.2, 41.3, and 31.9 min for CW1, CW2, and P1,
respectively. This result clearly indicates that the dye loading
rate (∼τ−1) is faster for the dye with carboxylic acid than that of
pyridine ring