Fluorescence Imaging with Chemical Sensors

Ratiometric imaging of pH probes reveals their localization in three types of microenvironment (cytosol, endosomes, lysosomes) in live cells

Imaging methods by the means of optical sensors are applied in diverse scientific areas such as medical research and diagnostics, aerodynamics, environmental analysis, or marine research. Prof. Dr. Michael Schäferling and Dr. Vladimir Ondrus from the Laboratory of Photonic Materials give a general introduction to the field. The covered topics include planar sensors (optrodes), nanoprobes, and sensitive coatings. Advanced sensor materials combined with imaging technologies enable the visualization of parameters which exhibit no intrinsic color or fluorescence, such as oxygen, pH, CO2, H2O2, Ca2+, or temperature. The progress on the development of multiple sensors and methods for referenced signal read out is also highlighted, as is the recent progress in device design and application formats using model systems in the lab or methods for measurements' in the field.

M. Schäferling, V. Ondrus: The Art of Fluorescence Imaging with Chemical Sensors: The Next Decade 2012-2022. Chemosensors 12 (2024), 31, DOI: 10.3390/chemosensors12030031

Application of tungstates in solid state lighting

Inorganic high-performance materials are a central part of the light generation chain of modern solid-state lighting devices. In addition to chips based on III/V semiconductors, modern light-emitting diodes (LEDs) contain an application-specific mixture of phosphors. These act as conversion materials, i.e. they are used to convert the output radiation into a desired line spectrum.

Europium-activated tungstates, a class of materials structurally characterized by [WO4] or [WO6] units, show promising optical properties. Among other things, tungstates allow a high activator concentration, show a low degree of thermal quenching and offer the possibility of intrinsic sensitization of activators. This makes them particularly interesting as potential converter materials for the red spectral range.

T. Pier, T. Jüstel: Application of Eu(III) activated tungstates in solid state lighting, Opt. Mater. X 22 (2024) 100299, DOI:

Theranostics with rare earth-doped LuPO4 nanoparticles

Theranostics is a generic term used in medicine and stands for the combination of therapy and diagnostics. During his doctorate, Jan Kappelhoff worked on an efficient method for radiotherapy and the visualization of nanoparticles.

For this purpose, Pr3+ and Nd3+ co-doped nanoscale LuPO4 particles were synthesized and the emitted UV-C radiation spectrum was characterized and optimized. By using the nanoparticles in the A549 lung cancer cell line, it was shown that a higher inactivation rate of the cancer cells was achieved in combination with 4 Gy irradiation than with irradiation alone.

In addition, Eu3+-doped nanoscale LuPO4 particles show a very interesting emission pattern for use in diagnostics. Due to the Lu3+ position and the substitution by Eu3+, this material emits with an emission maximum at 696 nm. This is a "transparent optical window" for the skin. In experiments, the nanoparticles were incubated in A549 cancer cells and could be successfully visualized using a UV-A excitation source.

Thao Tran, Jan Kappelhoff, Thomas Jüstel, Rox Anderson, and Martin Purschke "UV emitting nanoparticles enhance the effect of ionizing radiation in 3D lung cancer spheroids" International Journal of Radiation Biology 98(86) 1-34 (2022), DOI:10.1080/09553002.2022.2027541

New reference book: Applied Inorganic Chemistry (December 2022)

The present book consists of three volumes and is written by experienced authors who give a comprehensive overview on the many chemical and physico-chemical aspects related to application of inorganic compounds and materials in order to introduce senior undergraduate and postgraduate students (chemists, physicists, materials scientists, engineers) into this broad field.

Editors: Rainer Pöttgen, Thomas Jüstel, and Cristian A. Strassert

Release date: 5th December, 2022, first edition, doi: 10.1515/9783110733143

See detailed press release on this subject (only available in German language)

An optical thermometer

Thermometers come in many different shapes and designs. From classic rod thermometers to electronic and decorative thermometers with differently coloured floating bodies.

But what is an optical thermometer and what is it used for?

Optical thermometers are chemical compounds that change their emission patterns when the temperature changes. Such materials are being discussed for example for medical applications. Here, nanometer-sized particles are to be used to determine different cell temperatures. In addition, paints and coatings containing optical thermometers can be used to determine the temperature of components such as aerospace wings.

The below stated publication deals with the solid solution Li3Ba2La3-xPrx(WO4)8 (x = 0-3). The investigation of its photoluminescence revealed that the emission behaviour exhibited a significant temperature dependence. When the temperature changed the intensity ratio of two specific emission lines shifted with respect to each other. This can be used to detect the temperature of the phosphor by recording an emission spectrum.

J.-N. Keil, C. Paulsen, F. Rosner, R. Pöttgen, T. Jüstel: Crystallographic and Photoluminescence Studies on the Solid Solution Li3Ba2La3-xPrx(WO4)8 (x = 0-3), J. Luminescence 252 (2022) 119415, doi: 10.1016/j.jlumin.2022.119415

Photovoltaik - Lehrbuch zu Grundlagen, Theorie und Praxis | 6. Auflage (Juni 2022)

Von der Funktionsweise von Solarzellen bis hin zu Tipps zur Planung einer kompletten Photovoltaikanlage - in seinem Werk "Photovoltaik - Lehrbuch zu Grundlagen, Theorie und Praxis" liefert Prof. Mertens Antworten auf viele Fragen rund um die Photovoltaik. Der Leiter des Labors für Optoelektronik und Sensorik hat nun die sechste, aktualisierte und erweiterte Auflage des Lehrbuchs herausgegeben. Darin geht er auf aktuelle technische und gesellschaftliche Entwicklungen ein.

Zur ausführlichen Pressemitteilung

K. Mertens: Photovoltaik - Lehrbuch zu Grundlagen, Technologie und Praxis, 6. Auflage (2022) --> Webseite zum Lehrbuch


Nanocomposites are not just combining the properties of different classes of materials, they also allow to fine-tune the properties of individual building blocks. But how can we plan and understand the behaviour on the nano-scale? Dominik Voigt has investigated exactly this for composites made from carbon nanotubes and ternary semiconductor nanoparticles: using chemical spacers of various lengths he could study and clarify the influence of the carbon partner on the optical properties of the semiconductor system.

D. Voigt, G. Primavera, H. Uphoff, J. A. Rethmeier, L. Schepp, M. Bredol: Ternary chalcogenide-based quantum dots and carbon nanotubes: establishing a toolbox for controlled formation of nanocomposites, J. Phys. Chem. C, 126 (2022), 9076-9090, doi: 10.1021/acs.jpcc.2c01142

"PV-iTeach": development of online courses on photovoltaics

In collaboration with colleagues from Germany, Denmark and Sweden Prof. Mertens is working on installing an online study platform about photovoltaics. A comparable platform does not exist, yet. The two years project is sponsored by the DAAD Deutscher Akademischer Austauschdienst (German Academic Exchange Service).

In 2019, Prof. Mertens organized a summer school about photovoltaics in the Ivory Coast. The summer school was very successful and the interest in photovoltaics was unexpectedly high. Often, students from developing countries do not have access to topical issues in the field of photovoltaics. The new online study platform shall improve the knowledge on solar plants and measurement techniques of students worldwide.

On the time and temperature dependent photoluminescence of Pr3+ and Gd3+ doped Lu3Al5O12

Decay times of (Lu2.82Pr0.03Gd0.15)Al5O12 at 487.0 nm from 77 to 500 K.

This work concerns the energy transfer between gadolinium and praseodymium hosted by the garnet Lu3Al5O12. A solid solution of (Lu2.97-xPr0.03Gdx)Al5O12 (x = 0.003, 0.006, 0.015, 0.03, 0.06, 0.15, 0.3, 0.6) was synthesized with solution combustion method and investigated with respect to its phase purity, and reflection properties. It turned out that the emission intensity strongly relies on the Gd3+ concentration. Furthermore, the energy transfer between praseodymium and gadolinium in (Lu2.82Pr0.03Gd0.15)Al5O12 was investigated by measuring the time and temperature dependent luminescence from 77 to 500 K of the 6P7/28S7/2 and 3P03H4 transition of Gd3+, and Pr3+ respectively. It was found that the emission intensity and decay properties of gadolinium and praseodymium highly depend on the temperature.

M. Laube, T. Jüstel: On the temperature and time dependent photoluminescence of Pr3+ and Gd3+ doped Lu3Al5O12, Journal of Luminescence, 236 (2021), 118112, doi: 10.1016/j.jlumin.2021.118112

Editor's Pick: Fast focus-shifter based on a unimorph deformable mirror

To be selected as "Editor's Pick" by the Editorial Office of the Optical Society of America (OSA) adds value to a publication and is quite a honorable award for the authors. Editor's Picks serve to highlight articles with excellent scientific quality and are representative of the work taking place in a specific field. Our recent publication on a unimorph deformable mirror in Applied Optics was selected as Editor's Pick.

On-the-fly remote laser processing plays an increasingly important role in modern fabrication techniques. These processes require guiding of the focus of a laser beam along the contours of the workpiece in three dimensions. State-of-the-art galvanometer scanners already provide highly dynamic and precise transverse x—y beam steering. However, longitudinal focus shifting ("z-shifting") relying on conventional optics is restricted to a bandwidth of a few hundred Hz. We have developed and manufactured a fast piezo-based z-shifting mirror with diffraction-limited surface fidelity providing a focus shift of > 60mm with an actuation rate of 2 kHz.

S. Verpoort, M. Bittner and U. Wittrock: Fast focus-shifter based on a unimorph deformable mirror, Appl. Opt. 59, 6959-6965 (2020), doi: 10.1364/AO.397495 | ✔ Editor's Pick

Laser-induced nanocrowns improve detection limits of Raman spectroscopy

Applications and physical formation mechanisms of metallic crown-like nano-patterns were studied in a collaborative research paper recently published together with the Far Eastern Federal University in Vladivostok, Russia, in Applied Surface Science. Metal nanocrowns appear upon nanosecond laser patterning of thin metal layers deposited on a glass or silicon substrates. They are formed due to Rayleigh-Plateau hydrodynamic instability in the molten metallic rim around the laser-induced crater. Such structures can be used to increase the detection sensitivity of Raman spectroscopy.

D.V. Pavlov, S.O. Gurbatov, S.I. Kudryashov, E.L. Gurevich, A.A. Kuchmizhak: Laser-induced surface relief nanocrowns as a manifestation of nanoscale Rayleigh-Plateau hydrodynamic instability, Appl. Surf. Sci. 511, 145463 (2020), doi: 10.1016/j.apsusc.2020.145463

Monitoring the corrosion of concrete structures with optical pH sensors

The carbonation of reinforced concrete leads to undesirable material damage by the corrosion of the steel beams due to the impact of CO2 and the associated drop in pH. A pH value below 11.5 indicates the occurrence of carbonation and consequential damage. Prof. Schäferling from the Laboratory for Photonic Materials has developed in cooperation with the Federal Institute for Materials Research and Testing (BAM) a fiber-optic sensor for non-destructive monitoring of the pH in concrete which is now studied in test specimens with regard to long-term functionality.

J. Bartelmess, D. Zimmek, M. Bartholmai, C. Strangfeld, M. Schäferling: Fibre optic ratiometric fluorescence pH sensor for monitoring corrosion in concrete, Analyst (2020), doi: 10.1039/C9AN02348H

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