Roughly 2 x 10 13 molecules/cm 2 (~0.01 ML) desorbed from Pt-free alumina below 250 K, attributed to binding at alumina defects. CO desorption from Ge/alumina was ~15% weaker but extended to slightly higher temperatures, suggesting that the ~0.04 ML of alumina-bound Ge blocked 150 K adsorption at some alumina defect sites, but also slightly increased the strength of CO binding at some Ge/alumina sites. To facilitate comparison to the cluster-containing samples, the numbers of CO that desorbed from alumina and Ge/alumina samples are tabulated in terms of "molecules/cluster", i.e., and 400 K for Pt4 and Pt7, but not for Pt11. The total 1 st run CO desorption (corrected for alumina-bound CO) ranged from 3.73 CO/Pt4, to 6.22 CO/Pt7,to 6.76 CO/Pt11, i.e., the CO:Pt ratio was nearly unity for Pt4 and Pt7 but only ~0.6 for Pt11, indicating that all Pt atoms in Pt4 and Pt7 were accessible in agreement with DFT studies (see below), while Pt11 retained 3D structure with some Pt atoms buried, even when saturated with CO. Both the total CO/cluster and high T CO/cluster decreased gradually over the 6 TPD runs, with the largest decrease for Pt11. Given that these changes must have resulted from processes like cluster isomerization or sintering, the implication is that Pt11 is less thermally stable than Pt4 and Compared to the Ptn the initial numbers of CO molecules desorbing per cluster were lower for the PtnGem (by ~48% for n=4, 7, ~30% for 11), but both the molecules/cluster and the temperature dependence of the desorption were far more stable in repeated TPD cycles. All five TPD runs had relatively sharp peaks between ~375 and 475 K, along with weaker, featureless desorption at lower temperatures. Thus, the CO TPD results imply that Ge addition reduced the initial numbers of CO binding sites, but stabilized the clusters against sintering or other thermal changes that would have reduced the number or strength of the CO binding sites.