Tag Archives: Zhiwei Peng

First textile to automatically trap or release heat, depending on conditions

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A revolutionary fabric created at UMD reacts to environmental conditions to either trap heat or release it. (Photo by Faye Levine) Courtesy: University of Maryland

This may look like just another gauzy fabric but it has some special properties according to a February 7, 2019 news item on ScienceDaily,

Despite decades of innovation in fabrics with high-tech thermal properties that keep marathon runners cool or alpine hikers warm, there has never been a material that changes its insulating properties in response to the environment. Until now.

University of Maryland researchers have created a fabric that can automatically regulate the amount of heat that passes through it. When conditions are warm and moist, such as those near a sweating body, the fabric allows infrared radiation (heat) to pass through. When conditions become cooler and drier, the fabric reduces the heat that escapes. The development was reported in the February 8, 2019 issue of the journal Science.

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A February 8, 2019 University of Maryland news release (also on EurekAlert [published Feb.7, 2019]) by Kimbra Cutlip delves further into the research,

The researchers created the fabric from specially engineered yarn coated with a conductive metal. Under hot, humid conditions, the strands of yarn compact and activate the coating, while cool, dry conditions reverse the action. The researchers refer to this as “gating”—essentially a tunable blind that transmits or blocks heat.

“This is the first technology that allows us to dynamically gate infrared radiation,” said YuHuang Wang, a professor of chemistry and biochemistry and one of the paper’s corresponding authors who directed the studies.

The base yarn for this new textile is created with fibers made of two different synthetic materials—one absorbs water and the other repels it. The strands are coated with carbon nanotubes, a special class of lightweight, carbon-based, conductive metal.

Because materials in the fibers both resist and absorb water, the fibers warp when exposed to humidity such as that surrounding a sweating body. That distortion brings the strands of yarn closer together, opening the pores in the fabric and creating a minor cooling effect by allowing heat to escape. More importantly, it modifies the electromagnetic coupling between the carbon nanotubes in the coating.

“You can think of this coupling effect like the bending of a radio antenna to change the wavelength or frequency it resonates with,” Wang said. “Imagine bringing two antennae close together to regulate the kind of electromagnetic wave they pick up. When the fabric fibers are brought closer together, the radiation they interact with changes. In clothing, that means the fabric interacts with the heat radiating from the human body.

”Depending on the tuning, the fabric either blocks infrared radiation or allows it to pass through. The reaction is almost instant, so before people realize it, the dynamic gating mechanism is either cooling them down or working in reverse to trap heat.
 
“The human body is a perfect radiator. It gives off heat quickly,” said Min Ouyang, a professor of physics at UMD and the paper’s other corresponding author. “For all of history, the only way to regulate the radiator has been to take clothes off or put clothes on. But this fabric is a true bidirectional regulator.

More work is needed before the fabric can be commercialized, but according to the researchers, materials used for the base fiber are readily available and the carbon coating can be easily added during the standard dyeing process.

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

Dynamic gating of infrared radiation in a textile by Xu A. Zhang, Shangjie Yu, Beibei Xu, Min Li, Zhiwei Peng, Yongxin Wang, Shunliu Deng, Xiaojian Wu, Zupeng Wu, Min Ouyang, YuHuang Wang. Science 08 Feb 2019: Vol. 363, Issue 6427, pp. 619-623 DOI: 10.1126/science.aau1217

This paper is behind a paywall.

Graphene gains metallic powers after laser-burning

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Rice University (Texas, US) researchers have developed a technique for embedding metallic nanoparticles in graphene with the hope of one day replacing platinum catalysts in fuel cells. From an August 20, 2015 news item on ScienceDaily,

Laser-induced graphene, created by the Rice lab of chemist James Tour last year, is a flexible film with a surface of porous graphene made by exposing a common plastic known as polyimide to a commercial laser-scribing beam. The researchers have now found a way to enhance the product with reactive metals.

An August 20, 2015 Rice University news release (also on EurekAlert), which originated the news item, provides further description,

With the discovery, the material that the researchers call “metal oxide-laser induced graphene” (MO-LIG) becomes a new candidate to replace expensive metals like platinum in catalytic fuel-cell applications in which oxygen and hydrogen are converted to water and electricity.

“The wonderful thing about this process is that we can use commercial polymers, with simple inexpensive metal salts added,” Tour said. “We then subject them to the commercial laser scriber, which generates metal nanoparticles embedded in graphene. So much of the chemistry is done by the laser, which generates graphene in the open air at room temperature.

“These composites, which have less than 1 percent metal, respond as ‘super catalysts’ for fuel-cell applications. Other methods to do this take far more steps and require expensive metals and expensive carbon precursors.”

Initially, the researchers made laser-induced graphene with commercially available polyimide sheets. Later, they infused liquid polyimide with boron to produce laser-induced graphene with a greatly increased capacity to store an electrical charge, which made it an effective supercapacitor.

For the latest iteration, they mixed the liquid and one of three concentrations containing cobalt, iron or molybdenum metal salts. After condensing each mixture into a film, they treated it with an infrared laser and then heated it in argon gas for half an hour at 750 degrees Celsius.

That process produced robust MO-LIGs with metallic, 10-nanometer particles spread evenly through the graphene. Tests showed their ability to catalyze oxygen reduction, an essential chemical reaction in fuel cells. Further doping of the material with sulfur allowed for hydrogen evolution, another catalytic process that converts water into hydrogen, Tour said.

“Remarkably, simple treatment of the graphene-molybdenum oxides with sulfur, which converted the metal oxides to metal sulfides, afforded a hydrogen evolution reaction catalyst, underscoring the broad utility of this approach,” he said.

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

In situ Formation of Metal Oxide Nanocrystals Embedded in Laser-Induced Graphene by Ruquan Ye, Zhiwei Peng, Tuo Wang, Yunong Xu, Jibo Zhang, Yilun Li, Lizanne G. Nilewski, Jian Lin, and James M. Tour. ACS Nano, Just Accepted Manuscript DOI: 10.1021/acsnano.5b04138 Publication Date (Web): August 18, 2015
Copyright © 2015 American Chemical Society

This paper is open access provided you have an ACS ID, which is a free registration. ACS is the American Chemical Society.

James’ bond (Rice University research team creates graphene/nanotube hybrid)

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I have to give credit to Mike Williams’ Nov. 27, 2012 Rice University news release for the “James’ bond” phrase used to describe this graphene/nanotube hybrid,

A seamless graphene/nanotube hybrid created at Rice University may be the best electrode interface material possible for many energy storage and electronics applications.

Led by Rice chemist James Tour, researchers have successfully grown forests of carbon nanotubes that rise quickly from sheets of graphene to astounding lengths of up to 120 microns, according to a paper published today by Nature Communications. A house on an average plot with the same aspect ratio would rise into space.

Seven-atom rings (in red) at the transition from graphene to nanotube make this new hybrid material a seamless conductor. The hybrid may be the best electrode interface material possible for many energy storage and electronics applications. Image courtesy of the Tour Group

The Rice hybrid combines two-dimensional graphene, which is a sheet of carbon one atom thick, and nanotubes into a seamless three-dimensional structure. The bonds between them are covalent, which means adjacent carbon atoms share electrons in a highly stable configuration. The nanotubes aren’t merely sitting on the graphene sheet; they become a part of it.

“Many people have tried to attach nanotubes to a metal electrode and it’s never gone very well because they get a little electronic barrier right at the interface,” Tour said. “By growing graphene on metal (in this case copper) and then growing nanotubes from the graphene, the electrical contact between the nanotubes and the metal electrode is ohmic. That means electrons see no difference, because it’s all one seamless material.

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In the new work, the team grew a specialized odako that retained the iron catalyst and aluminum oxide buffer but put them on top of a layer of graphene grown separately on a copper substrate. The copper stayed to serve as an excellent current collector for the three-dimensional hybrids that were grown within minutes to controllable lengths of up to 120 microns.

Electron microscope images showed the one-, two- and three-walled nanotubes firmly embedded in the graphene, and electrical testing showed no resistance to the flow of current at the junction.

“The performance we see in this study is as good as the best carbon-based supercapacitors that have ever been made,” Tour said. “We’re not really a supercapacitor lab, and still we were able to match the performance because of the quality of the electrode. It’s really remarkable, and it all harkens back to that unique interface.”

Here’s the citation and a link for the article,

A seamless three-dimensional carbon nanotube graphene hybrid material by Yu Zhu, Lei Li, Chenguang Zhang, Gilberto Casillas,  Zhengzong Sun, Zheng Yan, Gedeng Ruan, Zhiwei Peng, Abdul-Rahman O. Raji, Carter Kittrell, Robert H. Hauge & James M. Tour in Nature Communications 3, Article number:1225 doi:10.1038/ncomms2234 Published 27 November 2012

This article is behind a paywall.

Graphene dreams of the Morph

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For anyone who’s not familiar with the Morph, it’s an idea that Nokia and the University of Cambridge’s Nanoscience Centre have been working on for the last few years. Originally announced as a type of flexible phone that you could wrap around your wrist, the Morph is now called a concept.  Here’s an animation illustrating some of the concepts which include flexibility and self-cleaning,

There have been very few announcements of any kind about the Morph or the technology that will support this concept. A few months ago, they did make an announcement about researching graphene as a means of actualizing the concept (noted in my May 6, 2011 posting [scroll down about 1/2 way]).

Interestingly the latest research published  on graphene and the flexible, transparent screens that are necessary to making something like the Morph a reality has come from a lab at Rice University. From the August 1, 2011 news item on Nanowerk,

The lab of Rice chemist James Tour lab has created thin films that could revolutionize touch-screen displays, solar panels and LED lighting. The research was reported in the online edition of ACS Nano (“Rational Design of Hybrid Graphene Films for High-Performance Transparent Electrodes”).

Flexible, see-through video screens may be the “killer app” that finally puts graphene — the highly touted single-atom-thick form of carbon — into the commercial spotlight once and for all, Tour said. Combined with other flexible, transparent electronic components being developed at Rice and elsewhere, the breakthrough could lead to computers that wrap around the wrist and solar cells that wrap around just about anything. [emphasis mine]

The lab’s hybrid graphene film is a strong candidate to replace indium tin oxide (ITO), a commercial product widely used as a transparent, conductive coating. It’s the essential element in virtually all flat-panel displays, including touch screens on smart phones and iPads, and is part of organic light-emitting diodes (OLEDs) and solar cells.

Here’s James Tour and Yu Zhu, the paper’s lead author, explaining how the flexible screen was developed,

There are other flexible screens and competitors to the Morph notably the PaperPhone mentioned in my May 6,2011 posting (scroll down about 2/3 of the way) and in my May 12, 2011 posting featuring an interview with Roel Vertegaal of Queen’s University, Ontario, Canada, about the PaperPhone. (We did not discuss the role that graphene might or might not play in the development of the Paperphone’s screens.)

I wonder what impact this work at Rice will have not only for the Morph and the PaperPhone but on the European Union’s pathfinder research competition (the prize is $1B Euros), mentioned in my June 13, 2011 posting about graphene (scroll down about 1/3 of the way). Graphene is one of the research areas being considered for the prize.

ETA Aug. 5, 2011: Tour’s team just published another paper on graphene, one that proves you can make it from anything containing carbon according the Aug. 4, 2011 news item, One Box of Girl Scout Cookies Worth $15 Billion: Lab Shows Troop How Any Carbon Source Can Become Valuable Graphene, on Science Daily,

The cookie gambit started on a dare when Tour mentioned at a meeting that his lab had produced graphene from table sugar.

“I said we could grow it from any carbon source — for example, a Girl Scout cookie, because Girl Scout Cookies were being served at the time,” Tour recalled. “So one of the people in the room said, ‘Yes, please do it. … Let’s see that happen.'”

Members of Girl Scouts of America Troop 25080 came to Rice’s Smalley Institute for Nanoscale Science and Technology to see the process. Rice graduate students Gedeng Ruan, lead author of the paper, and Zhengzong Sun calculated that at the then-commercial rate for pristine graphene — $250 for a two-inch square — a box of traditional Girl Scout shortbread cookies could turn a $15 billion profit.

Here’s the full reference for this second paper,

Gedeng Ruan, Zhengzong Sun, Zhiwei Peng, James M. Tour. Growth of Graphene from Food, Insects and Waste. ACS Nano, 2011; 110729113834087 DOI: 10.1021/nn202625c

The article is behind a paywall.