We employ a fluorescence bilayer method to directly measure the glass transition temperature (T-g) of the irreversibly adsorbed layer of polystyrene (PS) buried in bulk films as a function of adsorption time, t(ads). This bilayer geometry allows for the examination of interfacial effects on T-g of the adsorbed nanolayer. In the presence of a free surface, we observe a substantial reduction in T-g from bulk that lessens with t(ads) as a result of increased chain adsorption at the substrate. Submerging the adsorbed layer and effectively removing the free surface results in a suppression of the T-g deviation at early t(ads), suggesting chain adsorption dictates T-g at long t(ads). Annealing in the bilayer geometry promotes recovery of bulk T-g on a time scale reflecting the degree of adsorption. Our data are quantitatively rationalized via the free volume holes diffusion model, which explains adsorbed nanolayer T-g in terms of the diffusion of free volume pockets toward interfacial sinks.