Sintered Pt nanoparticles are encapsulated by an atomically thin TiO1.1 over-layer (I) / (III). This process is driven by a high density of Ti3+ interstitial forming a stable cluster below the surface. This cluster is broken up above ~800K, dissolving the overlayer (II) reversibly. The overlayer leads to particle burial (IV) in O2, due to their reduced mobility.
