No abstract

Since the beginning of the 1980s, colloidally synthesized quantum dots (QDs) have been in the focus of interest due to their possible implementation for color conversion, luminescent light concentrators, and lasing. For all these applications, the QDs benefit from being embedded into a host matrix to ensure stability and usability. Many different host materials used for this purpose still have their individual shortcomings. Here, we present a universal, fast, and flexible approach for the direct incorporation of a wide range of QDs into inorganic ionic crystals using cold flow. The QD solution is mixed with a finely milled salt, followed by the removal of the solvent under vacuum. Under high pressure (GPa), the salt powder loaded with QDs transforms into transparent pellets. This effect is well-known for many inorganic salts (e.g., KCl, KBr, KI, NaCl, CsI, AgCl) from, e.g., sample preparation for IR spectroscopy. With this approach, we are able to obtain strongly luminescent QD-salt composites, have precise control over the loading, and provide a chemically robust matrix ensuring long-term stability of the embedded QDs. Furthermore, we show the photo-, chemical, and thermal stability of the composite materials and their use as color conversion layers for a white light-emitting diode (w-LED). The method presented can potentially be used for all kinds of nanoparticles synthesized in organic as well as in aqueous media.

No abstract

Improving the performance of Ag nanowire electrodes by adjusting the reaction conditions and the molar mass of PVP.

In the past decades cadmium-free quantum dots (QDs), among which are quaternary colloidal Cu-Zn-In-S/ZnS (CZIS/ZnS) core/shell nanocrystals (NCs), have attracted great scientific interest. Particularly, their low toxicity and the possibility to tune their photoluminescence (PL) properties by varying the composition in the multicomponent system make them highly attractive for applications in light-emitting diodes (LEDs). Thus, the demands for high quality CZIS/ZnS QDs and methods to process them into bulk materials stimulate investigations of these nanomaterials. Herein, we demonstrate the synthesis of CZIS/ZnS core/shell NCs via a surfactant induced nucleation process, which emit in various colors covering the range from 520 nm to 620 nm possessing high photoluminescence quantum yields (PLQYs) up to 47%. Furthermore, the as synthesized NCs were successfully integrated into two different salt matrices [Na2B4O7 (Borax) and LiCl] using two different approaches. The commonly used incorporation of the NCs into Borax salt led to salt crystals emitting from 540 nm to 600 nm with PLQYs up to 24%. By encapsulating the QDs into LiCl, brightly emitting NCs-in-LiCl powders with the PL covering a range from 520 nm to 650 nm with PLQYs of up to 14% were obtained. As a proof of concept, the fabrication of a color conversion LED using NCs encapsulated into LiCl demonstrated the applicability of the encapsulated NCs.