Tag Archives: Tao Zhang

Converting carbon dioxide into fuel with blinking nanocrystals

A July 16, 2020 news item on Nanowerk announces some work from Rutgers University (New Jersey, US) where carbon dioxide could one day be converted into fuel or perhaps be used in quantum computers,

Imagine tiny crystals that “blink” like fireflies and can convert carbon dioxide, a key cause of climate change, into fuels.

A Rutgers-led team has created ultra-small titanium dioxide crystals that exhibit unusual “blinking” behavior and may help to produce methane and other fuels, according to a study in the journal Angewandte Chemie (“A Blinking Mesoporous TiO2-x Composed of Nanosized Anatase with Unusually Long-Lived Trapped Charge Carriers”).

The crystals, also known as nanoparticles, stay charged for a long time and could benefit efforts to develop quantum computers.

I don’t think I have the imagination necessary for this image, which illustrates the work according to the researchers,

The arrows point to titanium dioxide nanocrystals lighting up and blinking (left) and then fading (right). Images: Tewodros Asefa and Eliska Mikmekova

A July 16, 2020 Rutgers University news release (also on EurekAlert), which originated the news item, delves further into the topic,

“Our findings are quite important and intriguing in a number of ways, and more research is needed to understand how these exotic crystals work and to fulfill their potential,” said senior author Tewodros (Teddy) Asefa, a professor in the Department of Chemistry and Chemical Biology in the School of Arts and Sciences at Rutgers University-New Brunswick [in New Jersey]. He’s also a professor in the Department of Chemical and Biochemical Engineering in the School of Engineering.

More than 10 million metric tons of titanium dioxide are produced annually, making it one of the most widely used materials, the study notes. It is used in sunscreens, paints, cosmetics and varnishes, for example. It’s also used in the paper and pulp, plastic, fiber, rubber, food, glass and ceramic industries.

The team of scientists and engineers discovered a new way to make extremely small titanium dioxide crystals. While it’s still unclear why the engineered crystals blink and research is ongoing, the “blinking” is believed to arise from single electrons trapped on titanium dioxide nanoparticles. At room temperature, electrons – surprisingly – stay trapped on nanoparticles for tens of seconds before escaping and then become trapped again and again in a continuous cycle.

The crystals, which blink when exposed to a beam of electrons, could be useful for environmental cleanups, sensors, electronic devices and solar cells, and the research team will further explore their capabilities.

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

A Blinking Mesoporous TiO2−x Composed of Nanosized Anatase with Unusually Long‐Lived Trapped Charge Carriers by Dr. Tao Zhang, Dr. Jingxiang Low, Prof. Jiaguo Yu, Dr. Alexei M. Tyryshkin, Dr. Eliška Mikmeková, Prof. Tewodros Asefa. Angewandte Chemie DOI: https://doi.org/10.1002/anie.202005143 First published [online]: 22 May 2020

This paper is behind a paywall.

There’s more than one black gold

‘Black gold’ is a phrase I associate with oil, signifying its importance and desirability. These days, this analogic phrase can describe a material according to a July 24, 2015 news item on Nanowerk,

If colloidal gold [gold in solution] self-assembles into the form of larger vesicles, a three-dimensional state can be achieved that is called “black gold” because it absorbs almost the entire spectrum of visible light. How this novel intense plasmonic state can be established and what its characteristics and potential medical applications are is explored by Chinese scientists and reported in the journal Angewandte Chemie …

A July 24, 2015 Wiley (Angewandte Chemie) press release, which originated the news item, provides more details,

Metal nanostructures can self-assemble into superstructures that offer intriguing new spectroscopic and mechanical properties. Plasmonic coupling plays a particular role in this context. For example, it has been found that plasmonic metal nanoparticles help to scatter the incoming light across the surface of the Si substrate at resonance wavelengths, therefore enhancing the light absorbing potential and thus the effectivity of solar cells.

On the other hand, plasmonic vesicles are the promising theranostic platform for biomedical applications, a notion which inspired Yue Li and Cuncheng Li of the Chinese Academy of Science, Hefei, China, and the University of Jinan, China, as well as collaborators to prepare plasmonic colloidosomes composed of gold nanospheres.

As the method of choice, the scientists have designed an emulsion-templating approach based on monodispersed gold nanospheres as building blocks, which arranged themselves into large spherical vesicles in a reverse emulsion system.

The resulting plasmonic vesicles were of micrometer-size and had a shell composed of hexagonally close-packed colloidal nanosphere particles in bilayer or, for the very large superspheres, multilayer arrangement, which provided the enhanced stability.

“A key advantage of this system is that such self-assembly can avoid the introduction of complex stabilization processes to lock the nanoparticles together”, the authors explain.

The hollow spheres exhibited an intense plasmonic resonance in their three-dimensionally packed structure and had a dark black appearance compared to the brick red color of the original gold nanoparticles. The “black gold” was thus characterized by a strong broadband absorption in the visible light and a very regular vesicle superstructure. In medicine, gold vesicles are intensively discussed as vehicles for the drug delivery to tumor cells, and, therefore, it could be envisaged to exploit the specific light-matter interaction of such plasmonic vesicle structures for medical use, but many other applications are also feasible, as the authors propose: “The presented strategy will pave a way to achieve noble-metal superstructures for biosensors, drug delivery, photothermal therapy, optical microcavity, and microreaction platforms.” This will prove the flexibility and versatility of the noble-metal nanostructures.

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

Black Gold: Plasmonic Colloidosomes with Broadband Absorption Self-Assembled from Monodispersed Gold Nanospheres by Using a Reverse Emulsion System by Dilong Liu, Dr. Fei Zhou, Cuncheng Li, Tao Zhang, Honghua Zhang, Prof. Weiping Cai, and Prof. Yue Li. Angewandte Chemie International Edition Article first published online: 25 JUN 2015 DOI: 10.1002/anie.201503384

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This article is behind a paywall.

There is an image illustrating the work but, sadly, the gold doesn’t look black,

BlackGold

© Wiley-VCH

That’s it!

A planet-satellite model for nanoparticles

For anyone who visualizes atoms as planets (many of us were taught to think of atoms and their electrons in that way) then, the planet-satellite model for nanoparticles proposed by scientists at the Nanosystems Initiative Munich (NIM) will have a comforting familiarity, Here’s the model as per a Dec. 13, 2013 news item from Nanowerk,

Nanosystems Initiative Munich (NIM) physicists have developed a “planet-satellite model” to precisely connect and arrange nanoparticles in three-dimensional structures. Like photosystems of plants and algae, the model might in future serve to collect and convert energy.

If the scientists‘ nanoparticles were one million times larger, the laboratory would look like an arts and crafts room at Christmas time: gold, silver and colorful shiny spheres in different sizes and filaments in various lengths. For at the center of the nanoscale “planet-satellite model” there is a gold particle which is orbited by other nanoparticles made of silver, cadmium selenide or organic dyes.

A Dec. 2, 2013 NIM press release, which originated the news item, describes the proposed model in detail,

As if by magic, cleverly designed DNA strands connect the satellites with the central planet in a very precise manner. The technique behind this, called “DNA origami”, is a specialty of physics professor Tim Liedl (LMU Munich) and his team. The expertise on the optical characterization of the individual nanosystems is contributed by Professor Jochen Feldmann, Chair of Photonics and Optoelectronics at LMU and Coordinator of the Nanosystems Initiative Munich (NIM).

Large or small, near or far

A distinctive feature of the new model is the modular assembly system which allows the scientists to modify all aspects of the structure very easily and in a controlled manner: the size of the central nanoparticle, the types and sizes of the “satellites” and the distance between planet and satellite particle. It also enables the physicists to adapt and optimize their system for other purposes.

Artificial photosystem

Metals, semiconductors or fluorescent organic molecules serve as satellites. Thus, like the antenna molecules in natural photosystems, such satellite elements might in future be organized to collect light energy and transfer it to a catalytic reaction center where it is converted into another form of energy. For the time being, however, the model allows the scientists to investigate basic physical effects such as the so-called quenching process, which refers to the changing fluorescence intensity of a dye molecule as a function of the distance to the central gold nanoparticle.

“The modular assembly principle and the high yield we obtained in the production of the planet-satellite systems were the crucial factors for reliably investigating this well-known effect with the new methods,” explains Robert Schreiber, lead author of the study.

A whole new cosmos

In addition, the scientists succeeded in joining individual planet-satellite units together into larger structures, combining them as desired. This way, it might be possible to develop complex and functional three-dimensional nanosystems in future, which could be used as directed energy funnels, in Raman spectroscopy or as nanoporous materials for catalytic applications.

The physicists have supplied an image illustrating their model,

 

[downloaded from http://www.nano-initiative-munich.de/index.php?eID=tx_cms_showpic&file=uploads%2Fpics%2FBasiccover_6_Zeilen_02.jpg&md5=aec790fc11262dc94b41a440fa6788baeacfac97&parameters[0]=YTo0OntzOjU6IndpZHRoIjtzOjQ6IjUwMG0iO3M6NjoiaGVpZ2h0IjtzOjM6IjUw&parameters[1]=MCI7czo3OiJib2R5VGFnIjtzOjI0OiI8Ym9keSBiZ0NvbG9yPSIjZmZmZmZmIj4i&parameters[2]=O3M6NDoid3JhcCI7czozNzoiPGEgaHJlZj0iamF2YXNjcmlwdDpjbG9zZSgpOyI%2B&parameters[3]=IHwgPC9hPiI7fQ%3D%3D] Courtesy NIM

[downloaded from http://www.nano-initiative-munich.de/index.php?eID=tx_cms_showpic&file=uploads%2Fpics%2FBasiccover_6_Zeilen_02.jpg&md5=aec790fc11262dc94b41a440fa6788baeacfac97&parameters[0]=YTo0OntzOjU6IndpZHRoIjtzOjQ6IjUwMG0iO3M6NjoiaGVpZ2h0IjtzOjM6IjUw&parameters[1]=MCI7czo3OiJib2R5VGFnIjtzOjI0OiI8Ym9keSBiZ0NvbG9yPSIjZmZmZmZmIj4i&parameters[2]=O3M6NDoid3JhcCI7czozNzoiPGEgaHJlZj0iamF2YXNjcmlwdDpjbG9zZSgpOyI%2B&parameters[3]=IHwgPC9hPiI7fQ%3D%3D] Courtesy NIM

 

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

Hierarchical assembly of metal nanoparticles, quantum dots and organic dyes using DNA origami scaffolds by Robert Schreiber, Jaekwon Do, Eva-Maria Roller, Tao Zhang, Verena J. Schüller, Philipp C. Nickels, Jochen Feldmann, & Tim Liedl. Nature Nanotechnology (2013) doi:10.1038/nnano.2013.253 Published online 01 December 2013

It is behind a paywall but you can preview it for free via ReadCube Access.