nanostructured-ag-zeolite-composites-as-luminescence-based-humidity

Nanostructured Ag-zeolite Composites as Luminescence-based Humidity Sensors

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high ...

KU Leuven

Here we present a simple route to produce well-defined photo-reduced silver nanoparticles on TiO2 containing zeolites. We used natural and artificial irradiation sources to study their effect on the particle size distribution. The samples were investigated by electron microscopy, X-ray diffraction, fluorescence microscopy and UV-Vis diffuse reflectance spectroscopy.

Fabrication of silver nanoparticles with limited size distribution on TiO2 containing zeolites.

The integration of metal atoms and clusters in well-defined dielectric cavities is a powerful strategy to impart new properties to them that depend on the size and geometry of the confined space as well as on metal-host electrostatic interactions. Here, we unravel the dependence of the electronic properties of metal clusters on space confinement by studying the ionization potential of silver clusters embedded in four different zeolite environments over a range of silver concentrations. Extensive characterization reveals a strong influence of silver loading and host environment on the cluster ionization potential, which is also correlated to the cluster's optical and structural properties. Through fine-tuning of the zeolite host environment, we demonstrate photoluminescence quantum yields approaching unity. This work extends our understanding of structure-property relationships of small metal clusters and applies this understanding to develop highly photoluminescent materials with potential applications in optoelectronics and bioimaging.

Tuning the energetics and tailoring the optical properties of silver clusters confined in zeolites.

One of the ultimate goals in the study of metal clusters is the correlation between the atomic-scale organization and their physicochemical properties. However, direct observation of the atomic organization of such minuscule metal clusters is heavily hindered by radiation damage imposed by the different characterization techniques. We present direct evidence of the structural arrangement, at an atomic level, of luminescent silver species stabilized in faujasite (FAU) zeolites using aberration-corrected scanning transmission electron microscopy. Two different silver clusters were identified in Ag-FAU zeolites, a trinuclear silver species associated with green emission and a tetranuclear silver species related to yellow emission. By combining direct imaging with complementary information obtained from X-ray powder diffraction and Rietveld analysis, we were able to elucidate the main differences at an atomic scale between luminescent (heat-treated) and nonluminescent (cation-exchanged) Ag-FAU zeolites. It is expected that such insights will trigger the directed synthesis of functional metal nanocluster-zeolite composites with tailored luminescent properties.

Article	Year
Fabrication of silver nanoparticles with limited size distribution on TiO2 containing zeolites. Physical chemistry chemical physics : PCCP\| PubMed ID: 25083739	2014
Tuning the energetics and tailoring the optical properties of silver clusters confined in zeolites. Nature materials\| PubMed ID: 27270964	2016
Direct Observation of Luminescent Silver Clusters Confined in Faujasite Zeolites. ACS nano\| PubMed ID: 27391548	2016

Wouter Baekelant

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