We report on the fabrication of a siloxane-encapsulated quantum dot (QD) film (QD-silox film), which exhibits stable emission intensity for over 1 month even at elevated temperature and humidity. QD-silox films are solidified via free radical addition reaction between oligosiloxane resin and ligand molecules on QDs. We prepare the QD-oligosiloxane resin by sol-gel condensation reaction of silane precursors with QDs blended in the precursor solution, forgoing ligand-exchange of QDs. The resulting QD-oligosiloxane resin remains optically clear after 40 days of storage, in contrast to other QD-containing resins which turn turbid and ultimately form sediments. QDs also disperse uniformly in the QD-silox film, whose photoluminescence (PL) quantum yield (QY) remains nearly unaltered under harsh conditions; for example, 85 °C/5% relative humidity (RH), 85 °C/85% RH, strongly acidic, and strongly basic environments for 40 days. The QD-silox film appears to remain equally emissive even after being immersed into boiling water (100 °C). Interestingly, the PL QY of the QD-silox film noticeably increases when the film is exposed to a moist environment, which opens a new, facile avenue to curing dimmed QD-containing films. Given its excellent stability, we envision that the QD-silox film is best suited in display applications, particularly as a PL-type down-conversion layer.
Sodium ion batteries have been considered a promising alternative to lithium ion batteries for large-scale energy storage owing to their low cost and high natural abundance. However, the commercialization of this device is hindered by the lack of suitable anodes with an optimized morphology that ensure high capacity and cycling stability of a battery. Here, we not only demonstrate that copper sulfide nanoplates exhibit close-to-theoretical capacity (~560 mAh g–1) and long-term cyclability, but also reveal that their sodiation follows a non-equilibrium reaction route, which involves successive crystallographic tuning. By employing in situ transmission electron microscopy, we examine the atomic structures of four distinct sodiation phases of copper sulfide nanoplates including a metastable phase and discover that the discharge profile of copper sulfide directly reflects the observed phase evolutions. Our work provides detailed insight into the sodiation process of the high-performance intercalation–conversion anode material.
Graphene
liquid cell electron microscopy (GLC-EM), a cutting-edge
liquid-phase EM technique, has become a powerful tool to directly
visualize wet biological samples and the microstructural dynamics
of nanomaterials in liquids. GLC uses graphene sheets with a one carbon
atom thickness as a viewing window and a liquid container. As a result,
GLC facilitates atomic-scale observation while sustaining intact liquids
inside an ultra-high-vacuum transmission electron microscopy chamber.
Using GLC-EM, diverse scientific results have been recently reported
in the material, colloidal, environmental, and life science fields.
Here, the developments of GLC fabrications, such as first-generation
veil-type cells, second-generation well-type cells, and third-generation
liquid-flowing cells, are summarized. Moreover, recent GLC-EM studies
on colloidal nanoparticles, battery electrodes, mineralization, and
wet biological samples are also highlighted. Finally, the considerations
and future opportunities associated with GLC-EM are discussed to offer
broad understanding and insight on atomic-resolution imaging in liquid-state
dynamics.
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