Single-crystalline and monodisperse LaF3 triangular nanoplates (2.0 x 16.0 nm) in trigonal tysonite structure were synthesized by the thermolysis of a single-source precursor (SSP), La(CF3COO)3, in a hot oleic acid/octadecene solution. The combined use of SSP and coordinating and noncoordinating solvents was demonstrated to have played key roles in the formation of such high-quality nanoplates, which could spontaneously organize into two types of superlattices (edge-to-edge and face-to-face) on a large area. This SSP approach has advantages of one-step, mass production, and easy operation, and may represent a rather general route toward metal fluoride nanocrystals.

Two-dimensional (2D) layered hybrid perovskites of (RNH)PbX (R is an alkyl and X is a halide) have been recently synthesized and exhibited rich optical properties including fluorescence and exciton effects. However, few studies on transport and optoelectronic measurements of individual 2D perovskite crystals have been reported, presumably owing to the instability issue during electronic device fabrications. Here we report the first photodetector based on individual 2D (CHNH)PbBr perovskite crystals, built with the protection and top contact of graphene film. Both a high responsivity (∼2100 A/W) and extremely low dark current (∼10 A) are achieved with a design of interdigital graphene electrodes. Our study paves the way to build high-performance optoelectronic devices based on the emerging 2D single-crystal perovskite materials.

Metallic copper, which is normally considered as a contaminant in the growth of single-walled carbon nanotubes (SWNTs), was found to be an efficient catalyst to grow SWNTs under suitable conditions. It showed very high catalytic activity for the growth of both random SWNT networks and horizontally aligned SWNT arrays. Especially, high-quality SWNT arrays were obtained when monodispersed copper nanoparticles were used. The catalytic behavior of copper for the growth of SWNTs was discussed. The weaker interaction between the copper and silica surfaces plays an important role in the growth of high-quality horizontally aligned SWNT arrays. This new synthesis process of SWNTs with a non-ferromagnetic catalyst brings more convenience to the study of magnetic properties of SWNTs and gives more insight in structure-controlled synthesis of SWNTs.