Luminescent nanomaterials give car headlights a high brightness.
Source: iStock / chinaface
Luminescent nanoparticles are used in an increasing number of products. Precise knowledge of their luminescence efficiency or so-called quantum yield is crucial for industry. Therefore, Ute Resch-Genger and her team are developing reliable measurement methods for this purpose.
Luminescent materials have a wide range of applications: They are used in medical technology, for example in computer tomography, in photovoltaic systems, in the security codes of banknotes, the displays of television sets, smartphones and in lighting technology. The trend is towards ever smaller particles: from the micrometer range to the nano size, which is only a few millionths of a millimeter. These materials have particularly advantageous scattering properties and can be highly luminescent.
Luminosity is key
“Decisive for all applications of these materials are their luminescence properties, in other words, their luminescence color and luminescence efficiency,” explains Ute Resch-Genger, an expert in biophotonics, nanotechnology, and luminescent materials. “To do this, we measure the number of light quanta that the particles first absorb and then emit and relate these two to each other. This key parameter, termed luminescence quantum yield, describes the luminescence efficiency of a compound. It is a decisive quality criterion for companies that produce or use luminescent materials, as this property can be used to evaluate and compare the performance and suitability of different luminescent nanoparticles.”
BAM determines the brightness of materials. It is an important quality criterion.
Source: BAM
The determination of the luminescence quantum yield is complex. It depends on many external factors, such as the temperature or the environment of the particles. Therefore, only one international standard exists so far for this purpose. Complicated measurements of scattering particles are not very well covered. Often particularly such materials are of increasing interest for industrial applications.
However, developing and optimising such measurement methods is frequently too time-consuming even for large companies. BAM has been doing research on different types of luminescent materials for many years, developing reference methods and materials in this field and providing reference data. Currently, Ute Resch-Genger coordinates a joint project on the reliable determination of the luminescence quantum yield of luminescent nanoparticles which aims to timely transfer these scientific findings in standardization to support industry. It is funded by the Federal Ministry for Economic Affairs and Climate Action as a part of the funding programme “Knowledge and Technology Transfer through Patents and Standards”.
Focus on new converter materials
“In cooperation with Schott AG, which has been producing optical materials for more than 100 years, we are developing reliable methods for determining the quantum yield of luminescent particles. The focus is on novel converter materials which, for example, give car headlights a pleasant yellowish glow in combination with a blue laser or light emitting diode (LED). These materials are in high demand in industry for many different applications,” says Resch-Genger.
With this focus, the BAM scientist and her team are developing measurement procedures and reference materials which are suitable for industrial process control. The aim is to determine the influences of the measuring device on the result and at the same time to provide samples with known luminescence spectra and quantum yields which can be used for calibration. The measurement procedures, in turn, should be standardisable so that they can be transferred to international standardisation in a timely manner.
“With this project, we are closing an important gap in order to strengthen the market position of German companies in this field,” says Ute Resch-Genger. “Because we are making it easier for them to select particularly high-performance luminescent materials and to validate and control their measurement technology.”