New reference book: Applied Inorganic Chemistry

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

Erleuchtete Bakterien

Auf die weltweit zunehmende Bedrohung durch gefährliche Bakterien haben wir in der Vergangenheit bereits hingewiesen, siehe Artikel "Licht als Heilserum" im IOT-Archiv. Neben den "really bad guys" (MRSA) gibt es allerdings eine ungleich größere Zahl an "good guys", die sowohl wichtige physiologische Funktionen erfüllen als auch überaus annehmliche Seiten (z.B. in der Käseherstellung) aufweisen. Der schnellen Überwachung von Mikrobenzahlen kommt u. a. in der Lebensmittelherstellung größte Bedeutung zu. Das sogenannte Plattieren, die Mikroskopie und die Flowcytometrie sind darin wichtige mikrobiologische Analysetechniken; ein bedeutsamer Parameter ist die Bestimmung von Gesamtbakterienzahlen. Besonders für trübe Medien (z.B. Milch) entwickeln wir gemeinsam mit der Quantum Analysis GmbH, Münster, neuartige Bakterienfärbungen auf der Basis von Seltenerdkomplexen, die sich u.a. aufgrund ihrer einmalig langanhaltenden Lumineszenzsignale von Störungen des Trübungs-Hintergrunds abtrennen lassen.

M. M. Lezhnina, W. Rochowiak, W. Göhde, R. Kuczius, U. Kynast: The microbial threat: Can rare earths help? J. Biophotonics, 9 (2020), doi: 10.1002/jbio.202000068

W. Rochowiak, E. Kasprzycka, I.P. Assunção, U. Kynast, M. Lezhnina: Long-lifetime green-emitting Tb3+ complexes for bacterial staining. Aust. J. Chem., 75, 754-759 (2022). DOI:10.1071/CH21315

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

UV emitting nanoparticles for medical applications

Praseodymium-doped LuPO4 emits UV-C radiation between 225 and 280 nm, where DNA shows strong absorption bands. Due to the low penetration-depth of UV-C in biological tissues, and the small size of the particles new treatment with cell-damaging UV-C radiation is possible. The goal is to achieve the best compromise between efficient UV emission upon X-ray excitation and small particle size. We propose the use of these particles as novel radiation sensitizers to the well-known radiation therapy, especially for the treatment of hypoxic tumor cells.

Sara Espinoza, Max-Fabian Volhard, Heike Kätker, Heike Jenneboer, Anne Uckelmann, Markus Haase, Matthias Müller, Martin Purschke, Thomas Jüstel: Deep Ultraviolet Emitting Scintillators for Biomedical Applications: The Hard Way of Downsizing LuPO4:Pr3+, Particle & Particle Systems Characterization, 1800282 (2018), doi: 10.1002/ppsc.201800282

Michael R. Squillante, Thomas Jüstel, R. Rox Anderson, Charles Brecher, Daniel Chartier, James F. Christian, Nicolas Cicchetti, Sara Espinoza, Daniel R. McAdams, Matthias Müller, Brooke Tornifoglio, Yimin Wang, Martin Purschke: Fabrication and characterization of UV-emitting nanoparticles as novel radiation sensitizers targeting hypoxic tumor cells, Optical Materials 80, 197-202 (2018), doi: 10.1016/j.optmat.2018.04.033


More power through colloid chemistry

From studies on luminescent nanocomposites the importance of precise control of their nanostructure is well known. Aleksandra Szydło now has shown, that such insight gained from optical materials can be transferred to a very different application of nanocomposites: low temperature fuel cells. Using methodology developed for the assembly of optical nanocomposites she prepared colloidal precursor systems for electrocatalytic layers leading to fuel cells with improved electrical performance.

Michael Bredol, Aleksandra Szydło, Ivan Radev, Wladimir Philippi, Roland Bartholomäus, Volker Peinecke, Angelika Heinzel: How the colloid chemistry of precursor electrocatalyst dispersions is related to the polymer electrolyte membrane fuel cell performance, Journal of Power Sources 402, 15-23 (2018), doi: 10.1016/j.jpowsour.2018.09.005


Lösungen für Unlösliches: Tone als Nanotransporter

Wasser-Unlöslichkeit von Substanzen ist eines der häufigsten Probleme des Chemiealltags - besonders lästig, wenn es sich um wertvolle Substanzen wie Farb- und Leuchtstoffe handelt, die sich in wässrigem Milieu sehr häufig zusammenlagern und dabei ihre Funktion verlieren. Besondere Bedeutung hat dies für Leuchtstoffe, die als Biomarker diagnostische Aufgaben übernehmen könnten, aber an der vorwiegend wässrigen Umgebung an und in Zellen scheitern. Die eher zufällige Beobachtung, dass Leuchtstoffe mittels sogenannter Nano-Schichtsilikate (Tone mit Abmessungen weniger Nanometer) auch in Wasser "funktionieren" hat uns zu einer ganzen Reihe von Untersuchungen stimuliert. Beispiele:

M. Buhl, M. Staniford, S. Lamping, M. Körsgen, H. F. Arlinghaus, U. Kynast, B. J. Ravoo: Patterning of Nanoclays on Positively Charged Self-Assembled Monolayers via Micromolding in Capillaries, Langmuir 33, 8799-8804 (2017) --> zum Aufsatz

T. Felbeck, S. Mundinger, M. M. Lezhnina, M. Staniford, U. Resch-Genger, U. H. Kynast: Multifold Fluorescence Enhancement in Nanoscopic Fluorophore-Clay Hybrids in Transparent Aqueous Media, Chemistry - A European Journal 21, 7582-7587 (2015) --> zum Aufsatz

D. K. Dinga, M. Bredol, U. Kynast: Novel Approach toward Water-Soluble Singlet Oxygen Monitors Based on Hybrid Inorganic-Organic Nanoclay. The Journal of Physical Chemistry C 2021, 125, 21496-21502 (2021), doi: 10.1021/acs.jpcc.1c04785.


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