From ESRF: “Let there be light: how silver clusters in nano-cages produce light “

ESRF bloc
The European Synchrotron

24-06-2016
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Future LEDs might have been partly brewed at the ESRF’s beamline DUBBLE. An international team of researchers has shown that highly luminescent clusters of silver atoms can be assembled in the porous framework of minerals known as zeolites. The high efficiency of light emission from the materials, along with cheap and scalable synthesis makes them very attractive for next generation fluorescent lamps and LEDs or for biological imaging.

Silver clusters are small ensembles of just a few silver atoms (<10), which have remarkable catalytic and optical properties. Current applications for silver clusters are limited due to a natural tendency to aggregate into larger particles which do not exhibit these enhanced properties. To overcome this limitation, researchers from the Université de Strasbourg & CNRS and KU Leuven (Belgium) assembled and stabilised the clusters in nano-scale confined spaces. In particular, they used the pores in carefully chosen minerals, called zeolites.

Zeolites can be found naturally or produced synthetically on an industrial scale. Owing to their rigid and well-defined framework made of molecular-scale channels and cavities, zeolites are already used for a wide range of domestic and industrial applications (e.g. laundry detergent, water purification, gas separation, catalysis).

In this study, the researchers investigated silver clusters assembled in four different types of zeolite. Silver ions were introduced into the zeolites by means of ion-exchange, leading to the partial or total replacement of the native sodium or potassium ions in the parent zeolites. Thermal treatment at elevated temperature allowed the controlled assembly of the silver ions into well-defined clusters within the confined space of the zeolite cavities.

The team used the Dutch-Belgian beamline BM26 at the ESRF to carry out an in-depth characterisation of these heat-treated silver-exchanged zeolites using X-ray absorption fine structure (EXAFS). Wim Bras, responsible for the beamline, explains that "these results show that X-ray spectroscopy really is an unique tool and required for the characterization of technologically important new materials".

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Photoluminescence properties of heat-treated silver-exchanged zeolites.

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ESRF

The ESRF – the European Synchrotron Radiation Facility – is the most intense source of synchrotron-generated light, producing X-rays 100 billion times brighter than the X-rays used in hospitals. These X-rays, endowed with exceptional properties, are produced at the ESRF by the high energy electrons that race around the storage ring, a circular tunnel measuring 844 metres in circumference. Each year, the demand to use these X-ray beams increases and thousands of scientists from around the world come to Grenoble, to access the 43 highly specialised experimental stations, called “beamlines”, each equipped with state-of-the-art instrumentation, operating 24 hours a day, seven days a week.

Thanks to the brilliance and quality of its X-rays, the ESRF functions like a “super-microscope” which “films” the position and motion of atoms in condensed and living matter, and reveals the structure of matter in all its beauty and complexity. It provides unrivalled opportunities for scientists in the exploration of materials and living matter in a very wide variety of fields: chemistry, material physics, archaeology and cultural heritage, structural biology and medical applications, environmental sciences, information science and nanotechnologies.

Following on from 20 years of success and excellence, the ESRF has embarked upon an ambitious and innovative modernisation project, the Upgrade Programme, implemented in two phases: Phase I (2009-2015) and the ESRF-EBS (Extremely Brilliant Source) (2015-2022) programmes. With an investment of 330 million euros, the Upgrade Programme is paving the way to a new generation of synchrotron storage rings, that will produce more intense, coherent and stable X-ray beams. By constructing a new synchrotron, deeply rooted in the existing infrastructure, the ESRF will lead the way in pushing back the boundaries of scientific exploration of matter, and contribute to answering the great technological, economic, societal and environmental challenges confronting our society.