Direct synthesis of CsPbX3 perovskite nanocrystal assemblies.

Inorganic CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (NCs) possess many advantageous optoelectronic properties, making them an attractive candidate for light emitting diodes, lasers, or photodetector applications. Such perovskite NCs can form extended assemblies that further modify their bandgap and emission wavelength. In this article, a facile direct synthesis of CsPbX3 NC assemblies that are 1 µm in size and are composed of 10 nm-sized NC building blocks is reported. The direct synthesis of these assemblies with a conventional hot-injection method of the NCs is achieved through the judicious selection of the solvent, ligands, and reaction stoichiometry. Only under selective reaction conditions where the surface ligand environment is tuned to enhance the hydrophobic interactions between ligand chains of neighbouring NCs is self-assembly achieved. These assemblies possess narrow and red-shifted photoluminescence compared to their isolated NC counterparts, which further expands the colour gamut that can be rendered from inorganic perovskites. This is demonstrated through simple down-converting light emitters.

Macroporous perovskite nanocrystal composites for ultrasensitive copper ion detection.

Accumulation of heavy metal ions, including copper ions (Cu2+), presents a serious threat to human health and to the environment. A substantial amount of research has focused on detecting such species in aqueous solutions. However, progress towards ultrasensitive and easy-to-use sensors for non-aqueous solutions is still limited. Here, we focus on the detection of copper species in hexane, realising ultra-sensitive detection through a fluorescence-based approach. To achieve this, a novel macroporous composite material has been developed featuring luminescent CsPbBr3 nanocrystals (NCs) chemically adhered to a polymerized high internal phase emulsion (polyHIPE) substrate through surface thiol groups. Due to this thiol functionality, sub-monolayer NC formation is realised, which also renders outstanding stability of the composite in the ambient environment. Copper detection is achieved through a direct solution based immersion of the CsPbBr3-(SH)polyHIPE composite, which results in concentration-dependent quenching of the NC photoluminescence. This newly developed sensor has a limit of detection (LOD) for copper as low as 1 × 10-16 M, and a wide operating window spanning 10-2 to 10-16 M. Moreover, the composite exhibits excellent selectivity among different transition metals.

Endoscopically Assisted En Bloc Resection of Anterior Knee Lipoma.

Open resection of a large lipoma requires a large incision that may result in disfigurement from the scar. Endoscopic resection of the lipoma can have better cosmetic results. However, piecemeal removal of the lipoma has the disadvantage of fragmentation of the tumor before it can be determined whether it is benign or malignant. In this Technical Note, the technical details of endoscopically assisted en bloc resection of an anterior knee lipoma are described. This can provide a whole-block specimen for histologic examination.

Correction of Crossover Toe Deformity by Plantar Plate Tenodesis and Arthroscopic Release of Lumbrical.

Plantar plate deficiency is the major cause of instability of the metatarsophalangeal joint. As the joint subluxates dorsally, the lumbrical is tethered on the medial side of the joint by the deep metatarsal ligament and becomes a deforming force for the development of crossover toe deformity. Release of the lumbrical is needed to achieve adequate medial soft-tissue release. Plantar plate tenodesis has been described to correct the deformity by suturing the plantar plate to the extensor digitorum longus tendon. The purpose of this Technical Note is to incorporate the technique of arthroscopic release of the lumbrical tendon into the technique of plantar plate tenodesis.

Scalable synthesis of colloidal CsPbBr3 perovskite nanocrystals with high reaction yields through solvent and ligand engineering.

The ligand assisted reprecipitation (LARP) technique is an accessible and facile method that can synthesize metal halide perovskite nanocrystals (PNCs) under ambient conditions. However, low product yields of less than 30% for LARP and its contemporary methods are indicative of highly inefficient reactions. In this work we apply the principles of green chemistry to the LARP technique for synthesizing CsPbBr3 PNCs and help address this issue. Through these efforts, high product yields of ∼70% are achieved using stochiometric Cs : Pb precursor ratios. This is realized by (i) substituting the conventional toluene (TOL) anti-solvent with ethyl acetate (EA) and (ii) replacing the conventionally used unsaturated oleylamine ligand with the shorter saturated octylamine ligand. These changes also result in a 60% molar reduction in total ligand concentration and a 62.5% reduction in solvent waste during purification. The synthesized PNCs are comparable to the TOL-LARP reference in crystal quality, morphology and phase, with their photoluminescence quantum yields being readily enhanced to over 80% through additions of RNH3Br ligands. The spectral versatility of these materials is demonstrated through post-synthetic chloride and iodide halide anion exchange, which readily yields tunable CsPbX3 derivatives across the visible spectrum. Our EA-LARP protocol is further shown to be readily upscaled to ∼0.5 L, while maintaining good nanocrystal properties and a product yield of 60%.

Synthetic Evolution of Colloidal Metal Halide Perovskite Nanocrystals.

Metal halide perovskite semiconductor nanocrystals have emerged as a lucrative class of materials for many optoelectronic applications. By leveraging the synthetic toolboxes developed from decades of research into more traditional semiconductor nanocrystals, remarkable progress has been made across these materials in terms of their structural, compositional, and optoelectronic control. Here, we review this progress in terms of their underlying formation stages, synthetic approaches, and postsynthetic treatment steps. This assessment highlights the rapidly maturing nature of the perovskite nanocrystal field, particularly with regard to their lead-based derivatives. It further demonstrates that significant challenges remain around precisely controlling their nucleation and growth processes. In going forward, a deeper understanding of the role of precursors and ligands will significantly bolster the versatility in the size, shape, composition, and functional properties of these exciting materials.