Tag Archives: University of Marburg

Nanoavalanches in glass

An Aug. 24, 2016 news item on Nanowerk takes a rather roundabout way to describe some new findings about glass (Note: A link has been removed),

The main purpose of McLaren’s exchange study in Marburg was to learn more about a complex process involving transformations in glass that occur under intense electrical and thermal conditions. New understanding of these mechanisms could lead the way to more energy-efficient glass manufacturing, and even glass supercapacitors that leapfrog the performance of batteries now used for electric cars and solar energy.

“This technology is relevant to companies seeking the next wave of portable, reliable energy,” said Himanshu Jain, McLaren’s advisor and the T. L. Diamond Distinguished Chair in Materials Science and Engineering at Lehigh and director of its International Materials Institute for New Functionality in Glass. “A breakthrough in the use of glass for power storage could unleash a torrent of innovation in the transportation and energy sectors, and even support efforts to curb global warming.”

As part of his doctoral research, McLaren discovered that applying a direct current field across glass reduced its melting temperature. In their experiments, they placed a block of glass between a cathode and anode, and then exerted steady pressure on the glass while gradually heating it. McLaren and Jain, together with colleagues at the University of Colorado, published their discovery in Applied Physics Letters (“Electric field-induced softening of alkali silicate glasses”).

The implications for the finding were intriguing. In addition to making glass formulation viable at lower temperatures and reducing energy needs, designers using electrical current in glass manufacturing would have a tool to make precise manipulations not possible with heat alone.

“You could make a mask for the glass, for example, and apply an electrical field on a micron scale,” said Jain. “This would allow you to deform the glass with high precision, and soften it in a far more selective way than you could with heat, which gets distributed throughout the glass.”

Though McLaren and Jain had isolated the phenomenon and determined how to dial up the variables for optimal results, they did not yet fully understand the mechanisms behind it. McLaren and Jain had been following the work of Dr. Bernard Roling at the University of Marburg, who had discovered some remarkable characteristics of glass using electro-thermal poling, a technique that employs both temperature manipulation and electrical current to create a charge in normally inert glass. The process imparts useful optical and even bioactive qualities to glass.

Roling invited McLaren to spend a semester at Marburg to analyze the behavior of glass under electro-thermal poling, to see if it would reveal more about the fundamental science underlying what McLaren and Jain had observed in their Lehigh lab.

An Aug. 22, 2016 Lehigh University news release by Chris Quirk, which originated the news item, describes the latest work,

McLaren’s work in Marburg revealed a two-step process in which a thin sliver of the glass nearest the anode, called a depletion layer, becomes much more resistant to electrical current than the rest of the glass as alkali ions in the glass migrate away. This is followed by a catastrophic change in the layer, known as dielectric breakdown, which dramatically increases its conductivity. McLaren likens the process of dielectric breakdown to a high-speed avalanche, and uses spectroscopic analysis with electro-thermal poling as a way to see what is happening in slow motion.

“The results in Germany gave us a very good model for what is going on in the electric field-induced softening that we did here. It told us about the start conditions for where dielectric breakdown can begin,” said McLaren.

“Charlie’s work in Marburg has helped us see the kinetics of the process,” Jain said. “We could see it happening abruptly in our experiments here at Lehigh, but we now have a way to separate out what occurs specifically with the depletion layer.”

“The Marburg trip was incredibly useful professionally and enlightening personally,” said McLaren. “Scientifically, it’s always good to see your work from another vantage point, and see how other research groups interpret data or perform experiments. The group in Marburg was extremely hard-working, which I loved, and they were very supportive of each other. If someone submitted a paper, the whole group would have a barbecue to celebrate, and they always gave each other feedback on their work. Sometimes it was brutally honest––they didn’t hold back––but they were things you needed to hear.”

“Working in Marburg also showed me how to interact with a completely different group of people. “You see differences in your own culture best when you have the chance to see other cultures close up. It’s always a fresh perspective.”

Here are links and citations for both the papers mentioned. The first link is for the most recent paper and second link is for the earlier work,

Depletion Layer Formation in Alkali Silicate Glasses by
Electro-Thermal Poling by C. McLaren, M. Balabajew, M. Gellert, B. Roling, and H. Jain. Journal of The Electrochemical Society, 163 (9) H809-H817 (2016) H809 DOI: 10.1149/2.0881609jes Published July 19, 2016

Electric field-induced softening of alkali silicate glasses by C. McLaren, W. Heffner, R. Tessarollo, R. Raj, and H. Jain. Appl. Phys. Lett. 107, 184101 (2015); http://dx.doi.org/10.1063/1.4934945 Published online 03 November 2015

The most recent paper (first link) appears to be open access; the earlier paper (second link) is behind a paywall.

Labeling 5nm gold nanoparticles with gold isotopes (soft core, hard shell)

There’s a lot of talk about using gold nanoparticles (and others) to deliver drugs to specific locations in the body but this research at Helmholtz Zentrum Muenchen (Munich, Germany) and the University of Marburg (Marburg, Germany) appears to be the first successful attempt at tracking how this potential delivery system might actually work. From a June 23, 2015 news item on Azonano,

Nanoparticles are the smallest particles capable of reaching virtually all parts of the body. Researchers use various approaches to test ways in which nanoparticles could be used in medicine – for instance, to deliver substances to a specific site in the body such as a tumor.

For this purpose, nanoparticles are generally coated with organic materials because their surface quality plays a key role in determining further targets in the body. If they have a water-repellent shell, nanoparticles are quickly identified by the body’s immune system and eliminated.

How gold particles wander through the body

The team of scientists headed by Dr. Wolfgang Kreyling, who is now an external scientific advisor at the Institute of Epidemiology II within the Helmholtz Zentrum Muenchen, and Prof. Wolfgang Parak from the University of Marburg, succeeded for the first time in tracking the chronological sequence of such particles in an animal model. To this end, they generated tiny 5 nm gold nanoparticles radioactively labeled with a gold isotope*. These were also covered with a polymer shell and tagged with a different radioactive isotope. According to the researchers, this was, technically speaking, a very demanding nanotechnological step.

A June 22, 2015 Helmholtz Zentrum Muenchen press release, which originated the news item, provides more detail,

After the subsequent intravenous injection of the particles, however, the team observed how the specially applied polymer shell disintegrated. “Surprisingly, the particulate gold accumulated mainly in the liver,” Dr. Kreyling recalls. “In contrast, the shell molecules reacted in a significantly different manner, distributing themselves throughout the body.” Further analyses conducted by the scientists explained the reason for this: so-called proteolytic enzymes** in certain liver cells appear to separate the particles from their shell. According to the researchers, this effect was hitherto unknown in vivo, since up to now the particle-conjugate had only been tested in cell cultures, where this effect had not been examined sufficiently thoroughly.

“Our results show that even nanoparticle-conjugates*** that appear highly stable can change their properties when deployed in the human body,” Dr. Kreyling notes, evaluating the results. “The study will thus have an influence on future medical applications as well as on the risk evaluation of nanoparticles in consumer products and in science and technology.”

* Isotopes are types of atoms which have different mass numbers but which represent the same element.

** Proteolytic enzymes split protein structures and are used, for example, to nourish or detoxify the body.

*** Conjugates are several types of molecules that are bound in one particle.

Here’s a link to and a citation for the paper,

In vivo integrity of polymer-coated gold nanoparticles by Wolfgang G. Kreyling, Abuelmagd M. Abdelmonem, Zulqurnain Ali, Frauke Alves, Marianne Geiser, Nadine Haberl, Raimo Hartmann, Stephanie Hirn, Dorleta Jimenez de Aberasturi, Karsten Kantner, Gülnaz Khadem-Saba, Jose-Maria Montenegro, Joanna Rejman, Teofilo Rojo, Idoia Ruiz de Larramendi, Roser Ufartes, Alexander Wenk, & Wolfgang J. Parak. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.111 Published online 15 June 2015

This paper is behind a paywall.