Colloidal nanoplatelets (NPLs) have recently been introduced as semiconductor emissive materials for the fabrication of quantum dot light-emitting diodes (QLED) on account of their ultra-narrow photoluminescence (PL) linewidth. In this paper, we report a multilayer all solution-processed green QLED based on colloidal CdSe/CdS core/shell NPLs with a narrow PL full-width-at-half-maximum (FWHM) of 12 nm. Our characterization results reveal that this kind of NPL containing QLED exhibit a low operating voltage of 2.25 V and a maximum luminance up to 33 000 cd m(-2), and peak external quantum efficiency (EQE) of 5%, corresponding to 12.5 cd A(-1) in luminance efficiency. Particularly, these devices show ultra-high color purity for electroluminescence (EL) with FWHM of 14 nm. As extremely narrow EL and ultra-pure color is highly attractive in the applications of LED industries, this work signifies the unique potential application of one new class of colloidal core/shell NPLs in achieving bright and efficient LEDs with superior color saturation.

This report presents the fabrication and pressure-driven processing of heterostructural nanocrystal superlattices (HNC-SLs) self-assembled from quantum-dot-Au (QD-Au) satellite-type HNCs. In situ small/wide-angle X-ray scattering and electron microscopic measurements showed that the HNC-SLs underwent structural transformation at both atomic- and mesoscales during the pressure processing. Upon deviatoric stress-driven orientational migration, the intraparticle coalescence of Au satellites at QD surfaces transforms individual HNCs into heterodimers, whereas the interparticle fusion drives assembled HNCs into ordered heterorod arrays. These results demonstrate high-pressure-processing as a clean and fast means for conversion of HNCs into novel heteromaterials that are difficult to achieve through conventional synthetic routes.

Self-assembly of nanocrystals is a promising route for creating macroscale materials that derive function from the properties of their nanoscale building blocks. While much progress has been made assembling nanocrystals into different superlattices, controlling the relative orientations of nanocrystals in those lattices remains a challenge. Here, we combine experiments with computer simulations to study the self-assembly of patchy heterostructural nanocrystals (HNCs), consisting of near-spherical quantum dots decorated with regular arrangements of small gold satellites, into close-packed superlattices with pronounced orientational alignment of HNCs. Our simulations indicate that the orientational alignment is caused by van der Waals interactions between gold patches and is sensitive to the interparticle distance in the superlattice. We demonstrate experimentally that the degree and type of orientational alignment can be controlled by changing ligand populations on HNCs. This study provides guidance for the design and fabrication of nanocrystal superlattices with enhanced structural control.

Traditional shape memory polymers (SMPs) are mostly thermoresponsive, and their applications in nano-optics are hindered by heat-demanding programming and recovery processes. By integrating a polyurethane-based shape memory copolymer with templating nanofabrication, reconfigurable/rewritable macroporous photonic crystals have been demonstrated. This SMP coupled with the unique macroporous structure enables unusual all-room-temperature shape memory cycles. "Cold" programming involving microscopic order-disorder transitions of the templated macropores is achieved by mechanically deforming the macroporous SMP membranes. The rapid recovery of the permanent, highly ordered photonic crystal structure from the temporary, disordered configuration can be triggered by multiple stimuli including a large variety of vapors and solvents, heat, and microwave radiation. Importantly, the striking chromogenic effects associated with these athermal and thermal processes render a sensitive and noninvasive optical methodology for quantitatively characterizing the intriguing nanoscopic shape memory effects. Some critical parameters/mechanisms that could significantly affect the final performance of SMP-based reconfigurable photonic crystals including strain recovery ratio, dynamics and reversibility of shape recovery, as well as capillary condensation of vapors in macropores, which play a crucial role in vapor-triggered recovery, can be evaluated using this new optical technology.

The development of an analytical method for selective and sensitive detection of chlortetracycline (CTC), an often overused broad spectrum antibiotic, is important and challenging in environmental and health monitoring. This paper reports a zinc based metal–organic framework of pyromellitic acid (Zn-BTEC), which has been found to greatly enhance the aggregation-induced emission (AIE) of chlortetracycline. The unique emission response of CTC on Zn-BTEC has been extensively examined and applied for the sensitive detection of CTC on the basis of fluorescence intensity of AIE, and a limit of detection (LOD) was estimated to be 28 nM. A rational mechanism has been proposed based on the porous structure of Zn-BTEC, and the CTC molecules would defuse into the rigid MOF structure and assemble or aggregate, leading to fluorescence enhancement of CTC. Interestingly, the Zn-BTEC materials could discriminate CTC from other TC antibiotics with high selectivity. We have further demonstrated that the Zn-BTEC materials are successfully applied for the sensitive and selective determination of CTC in real samples of fish and urine.