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We report herein a simple ligand-assisted reprecipitation method at room temperature to synthesize mixed-cation hybrid organic–inorganic perovskite nanocrystals with low structural dimensionality., We report herein a simple ligand-assisted reprecipitation method at room temperature to synthesize mixed-cation hybrid organic–inorganic perovskite nanocrystals with low structural dimensionality. The emission wavelength of iodide-based perovskites is thus tuned from the near-infrared to the red part of the visible spectrum. While this is mostly achieved in the literature by addition of bromide, we demonstrate here a controllable blueshift of the band gap by varying the chain length of the alkylammonium ligands. Furthermore, an antisolvent washing step was found to be crucial to purify the samples and obtain single-peak photoluminescence with a narrow linewidth. The so-formed nanocrystals exhibit high and stable photoluminescence quantum yields exceeding 90% over 500 hours, making these materials ideal for light-emitting applications.

We developed a facile synthesis of nanocomposite powders of CsPbX

We report the frictional response of few-layer graphene (FLG) flakes obtained by liquid phase exfoliation (LPE) of pristine graphite. To this end, we inkjet print FLG on bare and hexamethyldisilazane-terminated SiO2 substrates, producing micrometric patterns with nanoscopic roughness that are investigated by atomic force microscopy. Normal force spectroscopy and atomically resolved morphologies indicate reduced surface contamination by solvents after a vacuum annealing procedure. Notably, the printed FLG flakes show ultralow friction comparable with micromechanically exfoliated graphene flakes. Lubricity is retained on flakes with lateral size of a few tens of nanometres, and with thickness as small as ~ 2 nm, confirming the high crystalline quality and low defects density in the FLG basal plane. Surface exposed step edges exhibit the highest friction values, representing preferential sites for originating secondary dissipative processes related to edge straining, wear or lateral displacement of the flakes. Our work demonstrates that LPE enables fundamental studies on graphene friction to the single-flake level. The capability to deliver ultralow-friction-graphene over technologically relevant substrates, using a scalable production route and a high-throughput, large-area printing technique, may also open up new opportunities in the lubrication of micro- and nano-electromechanical systems., Comment: 31 pages, 18 figures