Interaction of molecular oxygen with semiconducting oxide surfaces plays a key role in many technologies. The topic is difficult to approach both by experiment and in theory, mainly due to multiple stable charge states, adsorption configurations, and reaction channels of adsorbed oxygen species. Here we use a combination of noncontact atomic force microscopy (AFM) and density functional theory (DFT) to resolveO2adsorption on the rutileTiO2(110) surface, which presents a longstanding challenge in the surface chemistry of metal oxides. We show that chemically inert AFM tips terminated by an oxygen adatom provide excellent resolution of both the adsorbed species and the oxygen sublattice of the substrate. AdsorbedO2molecules can accept either one or two electron polarons from the surface, forming superoxo or peroxo species. The peroxo state is energetically preferred under any conditions relevant for applications. The possibility of nonintrusive imaging allows us to explain behavior related to electron/hole injection from the tip, interaction with UV light, and the effect of thermal annealing.

A photoresist system for 3D two‐photon microprinting is presented, which enables the printing of inherently nanoporous structures with mean pore sizes around 50 nm by means of self‐organization on the nanoscale. A phase separation between polymerizable and chemically inert photoresist components leads to the formation of 3D co‐continuous structures. Subsequent washing‐out of the unpolymerized phase reveals the porous polymer structures. To characterize the volume properties of the printed structures, scanning electron microscopy images are recorded from ultramicrotome sections. In addition, the light‐scattering properties of the 3D‐printed material are analyzed. By adjusting the printing parameters, the porosity can be controlled during 3D printing. As an application example, a functioning miniaturized Ulbricht light‐collection sphere is 3D printed and tested.

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