Room-Temperature Doping of CsPbBr3 Nanocrystals with Aluminum.

B-site doping is an emerging strategy for tuning the emission wavelength of cesium lead halide ABX3 nanocrystals. We present a simple method for the postsynthetic doping of CsPbBr3 nanocrystals with aluminum at room temperature by exposing them to a solution of AlBr3 in dibromomethane. Despite the much smaller ionic radius of Al3+ compared to that of Pb2+, nominal doping levels in a range from 8.1% to 24.3% were obtained when increasing the Al/Pb feed ratio from 1 to 4.5. Al3+ introduction leads to a hypsochromic shift of the photoluminescence (PL) emission of the CsPbBr3 nanocrystals. The PL peak position is highly stable over at least 6 months and tunable in a range of 510 to 480 nm by increasing the doping level. Structural analyses revealed a linear correlation between the PL energy and the lattice parameter with a slope of -1.96 eV/Å.

Practice of electron microscopy on nanoparticles sensitive to radiation damage: CsPbBr3 nanocrystals as a case study.

In-depth and reliable characterization of advanced nanoparticles is crucial for revealing the origin of their unique features and for designing novel functional materials with tailored properties. Due to their small size, characterization beyond nanometric resolution, notably, by transmission electron microscopy (TEM) and associated techniques, is essential to provide meaningful information. Nevertheless, nanoparticles, especially those containing volatile elements or organic components, are sensitive to radiation damage. Here, using CsPbBr3 perovskite nanocrystals as an example, strategies to preserve the native structure of radiation-sensitive nanocrystals in high-resolution electron microscopy studies are presented. Atomic-resolution images obtained using graphene support films allow for a clear comparison with simulation results, showing that most CsPbBr3 nanocrystals are orthorhombic. Low-dose TEM reveals faceted nanocrystals with no in situ formed Pb crystallites, a feature observed in previous TEM studies that has been attributed to radiation damage. Cryo-electron microscopy further delays observable effects of radiation damage. Powder electron diffraction with a hybrid pixel direct electron detector confirms the domination of orthorhombic crystals. These results emphasize the importance of optimizing TEM grid preparation and of exploiting data collection strategies that impart minimum electron dose for revealing the true structure of radiation-sensitive nanocrystals.

Insights into the Electrochemical Polymerization of [Mo3 S13 ]2- Generating Amorphous Molybdenum Sulfide.

Amorphous molybdenum sulfide is an attractive electrode material for Li/Mg batteries and an efficient Pt-free catalyst for the hydrogen evolution reaction in water. By using the electrochemical quartz crystal microbalance (EQCM) analysis, new insights were gained into the electrochemical polymerization of the [Mo3 S13 ]2- cluster, which generates amorphous molybdenum sulfide thin films. In this work, it is shown that, at the anodic potential, a two-electron oxidative elimination of the terminal disulfide ligand within the [Mo3 S13 ]2- cluster induces the polymerization. A reductive elimination of the terminal disulfide ligand also occurs at the cathodic potential, inducing the polymerization. However, in sharp contrast to the anodic polymerization, according to which the film growth is rapid, the cathodic polymerization competes with the electrochemical reductive corrosion of the readily grown film, therefore occurring at a significant lower growth rate.