3D assembly of silica encapsulated semiconductor nanocrystals

Abstract

Non-ordered porous networks, so-called aerogels, can be achieved by the 3D assembly of quantum dots (QDs). These materials are well suited for photonic applications, however a certain quenching of the photoluminescence (PL) intensity is observed in these structures. This PL quenching is mainly attributed to the energy transfer mechanisms that result from the close contact of the nanoparticles in the network. Here, we demonstrate the formation of a novel aerogel material with non-quenching PL behaviour by non-classical, reversible gel formation from tetrazole capped silica encapsulated QDs. Monitoring of the gelation/degelation by optical spectroscopy showed that the optical properties of the nanocrystals could be preserved in the 3D network since no spectral shifts and lifetime shortening, which can be attributed to the coupling between QDs, are observed in the gels as compared to the original colloidal solutions. In comparison with other QD-silica monoliths, QDs in our gels are homogeneously distributed with a distinct and controllable distance. In addition we show that the silica shell is porous and allows metal ions to pass through the shell and interact with the QD core causing detectable changes of the emission properties. We further show the applicability of this gelation method to other QD materials which sets the stage for facile preparation of a variety of mixed gel structures.

Modern Inorganic Aerogels

“…[65,66] Forp ure quantum dots assembled into gels ac hange in the emission properties attributed to FRET has been reported (see Figure 9l eft). [65,66] Forp ure quantum dots assembled into gels ac hange in the emission properties attributed to FRET has been reported (see Figure 9l eft).…”

“…[70] First they synthesized CdSe/CdS core/crown nanoplatelets,w hich were then transferred into an aqueous phase.The destabilization was induced by the addition of hydrogen peroxide as an oxidizing agent to remove the thiolated stabilizers.Final aerogels were obtained Figure 9. [65,66] Reproducedwith permission from Ref. In contrast, for quantum dots having asilica shell, the emissionc olor does not change during gelation (right).…”

Tetrazoles: Unique Capping Ligands and Precursors for Nanostructured Materials

“…[ 40 ] These shells grown by the reverse microemulsion method were functionalized with a specially designed tetrazole ligand, 5-(3-(trimethoxysilyl)propylaminomethyl) tetrazole, which has the ability to bind to the silica surface via a silane group. The strategy developed is quite general and allows for effi cient encapsulation and subsequent gelation of different nanoparticle materials, such as core/shell CdSe/ CdS, core/shell/shell CdSe/CdS/ZnS, In(Zn)P/GaP/ZnS, and alloyed CdSeZnS quantum dots originally capped with long hydrocarbon chain containing ligands that provide solubility in organic solvents.…”

Moderne Anorganische Aerogele

“…[65,66] FürG ele,d ie aus reinen Quantenpunkten gebildet wurden, konnte eine durch Fçrster-Resonanz-Energietransfer (FRET) verursachte Veränderung in den Emissionseigenschaften beobachtet werden (Abbildung 9, links). [65,66] FürG ele,d ie aus reinen Quantenpunkten gebildet wurden, konnte eine durch Fçrster-Resonanz-Energietransfer (FRET) verursachte Veränderung in den Emissionseigenschaften beobachtet werden (Abbildung 9, links).…”

“…[74,75] Des Weiteren publizierten sie die Herstellung transparenter,l eit-Abbildung 9. [66] (rechts). Im Unterschied dazu verändert sich die Emissionsfarbe der Quantenpunkte mit einer Siliciumoxidschale während der Gelierung nicht (rechts).…”