Helmholtz-Gemeinschaft Deutscher Forschungszentren eV

For nanomedical targeting and drug delivery purposes, the noncovalent assembly of polymer building blocks into defined nanostructures is an intense area of research. One of the key assets desirable to know for the potential nanocarrier is the stability under conditions close to those in application scenarios. Here, a series of polymer building blocks based on poly(ethylene glycol) (PEG), which comprise a functional end group facilitating self-assembly into supramolecular polymer bottlebrushes (SPBs), is hydrodynamically studied. The building blocks, and consequently the assemblies, are labeled with a cyanine5 (Cy5) dye enabling selective tracing of the materials in human serum (HS) in analytical ultracentrifugation (AUC) experiments. Our experiments reveal a long-term stability of the noncovalent assemblies over one month of storage of the materials in HS at body temperature. At the same time, the interaction of some of the Cy5 moieties with the transport protein human serum albumin (HSA) is evidenced.

For energy storage in 2D MXenes using hydrogen, it is crucial to understand the relevant diffusion mechanisms. Density functional theory was used to determine hydrogen migration barriers, hopping frequencies, enthalpy and entropy of vacancy formation, and the diffusion coefficient of various possible migration paths. The results show that H diffusion is primarily governed by interstitial diffusion. For all investigated diffusion paths, the diffusion coefficients and prefactors, D₀, the corresponding activation energy, E, and the hopping frequencies are calculated from the ab initio approach.

Printing perovskite films typically involves a high-temperature treatment exceeding 150 °C, which limits the manufacturing of flexible devices.All inorganic CsPbI₃ perovskite is particularly promising for commercialization due to its high thermal stability.Herein, we discovered that when using DMF precursors containing CsI and HPbI₃ for fabricating CsPbI₃ films, an isopropanol (IPA) antisolvent bath immersion treatment of the wet films can enable a direct and rapid formation of optically active perovskite black phases at room temperature without annealing.In situ photoluminescence and in situ transmission techniques were employed to monitor and characterize the transition from the wet film to the final perovskite phase.It can be concluded that the relatively fast nucleation and slow grain growth during the IPA-bath treatment result in films with small grains and pronounced pinholes on the surface.Furthermore, FTIR, Raman, and NMR techniques were used to investigate changes in the chem. bonds.The characterization results revealed that the hydrogen in HPbI₃ can form a chem. bond with the oxygen in DMF, resulting in mutual attraction.As DMF is extracted by IPA, the DMF mol. simultaneously induces the hydrogen to leave its original position, and then free cesium easily fills the vacancy left by hydrogen, forming the black-phase CsPbI₃ perovskite.This finding reveals the mechanism of the room-temperature phase transition of CsPbI₃ facilitated by IPA post-treatment, and it explains why the use of HPbI₃ instead of PbI₂ in the precursor solution effectively lowers the reaction energy barrier for CsPbI₃ in previous works.