Tag Archives: honey

Manipulating graphene’s conductivity with honey

Honey can be used for many things, to heal wounds, for advice (You catch more flies with honey), to clean your hair (see suggestion no. 19 here) and, even, scientific inspiration according to a Sept. 22, 2017 news item on phys.org,

Dr. Richard Ordonez, a nanomaterials scientist at the Space and Naval Warfare Systems Center Pacific (SSC Pacific), was having stomach pains last year. So begins the story of the accidental discovery that honey—yes, the bee byproduct—is an effective, non-toxic substitute for the manipulation of the current and voltage characteristics of graphene.

The news item was originated by a Sept. 22, 2017 article by Katherine Connor (who works for  the US Space and Naval warfare Center) and placed in cemag.us,

Ordonez’ lab mate and friend Cody Hayashi gave him some store-bought honey as a Christmas gift and anti-inflammatory for his stomach, and Ordonez kept it near his work station for daily use. One day in the lab, the duo was investigating various dielectric materials they could use to fabricate a graphene transistor. First, the team tried to utilize water as a top-gate dielectric to manipulate graphene’s electrical conductivity. This approach was unsuccessful, so they proceeded with various compositions of sugar and deionized water, another electrolyte, which still resulted in negligible performance. That’s when the honey caught Ordonez’ eye, and an accidental scientific breakthrough was realized.

The finding is detailed in a paper in Nature Scientific Reports, in which the team describes how honey produces a nanometer-sized electric double layer at the interface with graphene that can be used to gate the ambipolar transport of graphene.

“As a top-gate dielectric, water is much too conductive, so we moved to sugar and de-ionized water to control the ionic composition in hopes we could reduce conductivity,” Ordonez explains. “However, sugar water didn’t work for us either because, as a gate-dielectric, there was still too much leakage current. Out of frustration, literally inches away from me was the honey Cody had bought, so we decided to drop-cast the honey on graphene to act as top-gate dielectric — I thought maybe the honey would mimic dielectric gels I read about in literature. To our surprise — everyone said it’s not going to work — we tried and it did.”

Image of the liquid-metal graphene field-effect transistor (LM-GFET) and representation of charge distribution in electrolytic gate dielectrics comprised of honey. Image: Space and Naval Warfare Systems Center

 

Ordonez, Hayashi, and a team of researchers from SSC Pacific, in collaboration with the University of Hawai′i at Mānoa, have been developing novel graphene devices as part of a Navy Innovative Science and Engineering (NISE)-funded effort to imbue the Navy with inexpensive, lightweight, flexible graphene-based devices that can be used as next-generation sensors and wearable devices.

“Traditionally, electrolytic gate transistors are made with ionic gel materials,” Hayashi says. “But you must be proficient with the processes to synthesize them, and it can take several months to figure out the correct recipe that is required for these gels to function in the environment. Some of the liquids are toxic, so experimentation must be conducted in an atmospheric-controlled environment. Honey is completely different — it performs similarly to these much more sophisticated materials, but is safe, inexpensive, and easier to use. The honey was an intermediate step towards using ionic gels, and possibly a replacement for certain applications.”

Ordonez and Hayashi envision the honey-based version of graphene products being used for rapid prototyping of devices, since the devices can be created quickly and easily redesigned based on results. Instead of having to spend months developing the materials before even beginning to incorporate it into devices, using honey allows the team to get initial tests underway without waiting for costly fabrication equipment.

Ordonez also sees a use for such products in science, technology, engineering, and math (STEM) outreach efforts, since the honey is non-toxic and could be used to teach students about graphene.

This latest innovation and publication was a follow-on from the group’s discovery last year that liquid metals can be used in place of rigid electrodes such as gold and silver to electrically contact graphene. This, coupled with research on graphene and multi-spectral detection, earned them the Federal Laboratory Consortium Far West Regional Award in the category of Outstanding Technology Development.

SSC Pacific is the naval research and development lab responsible for ensuring Information Warfare superiority for warfighters, including the areas of cyber, command and control, intelligence, surveillance and reconnaissance, and space systems.

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

Rapid Fabrication of Graphene Field-Effect Transistors with Liquid-metal Interconnects and Electrolytic Gate Dielectric Made of Honey by Richard C. Ordonez, Cody K. Hayashi, Carlos M. Torres, Jordan L. Melcher, Nackieb Kamin, Godwin Severa, & David Garmire. Scientific Reports 7, Article number: 10171 (2017) doi:10.1038/s41598-017-10043-4 Published online: 31 August 2017

This paper is open access.

Graphene like honey

Two teams have published results in Science magazine showing that graphene can flow like a liquid. The UK-Italian team has likened the movement to honey while the US team likened it to water (Feb. 18, 2016 posting). Here’s more about the honey from a Feb. 12, 2016 news item on Nanowerk (Note: A link has been removed),

Electrons which act like slow-pouring honey have been observed for the first time in graphene, prompting a new approach to fundamental physics.

Electrons are known to move through metals like bullets being reflected only by imperfections, but in graphene they move like in a very viscous liquid, University of Manchester researchers have found.

The possibility of a highly viscous flow of electrons in metals was predicted several decades ago but despite numerous efforts never observed, until now as reported in the journal Science (“Negative local resistance caused by viscous electron backflow in graphene”).

The observation and study of this effect allows better understanding of the counterintuitive behaviour of interacting particles, where the human knowledge and developed mathematical techniques are lacking.

A Feb. 11, 2016 University of Manchester press release, which originated the news item, offers more technical detail,

One-atom thick material graphene, first explored a decade ago by a team at The University of Manchester, is renowned for its many superlative properties and, especially, exceptionally high electrical conductivity.

It is widely believed that electrons in graphene can move ‘ballistically’, like bullets or billiard balls scattering only at graphene boundaries or other imperfections.

The reality is not quite so simple, as found by a Manchester group led by Sir Andre Geim in collaboration with Italian researchers led by Prof Marco Polini.

They observed that the electric current in graphene did not flow along the applied electric field, as in other materials, but travelled backwards forming whirlpools where circular currents appeared.Such behaviour is familiar for conventional liquids such as water which makes whirlpools when flowing around obstacles, for example, in rivers.

The scientists measured the viscosity of this strange new liquid in graphene, which consists not of water molecules but electrons. To the researchers surprise, the electron fluid can be 100 times more viscous than honey, even at room temperature.

The scientific breakthrough is important for understanding of how materials work at increasing smaller sizes required by the semiconducting industry because such whirlpools are more likely to appear at micro and nanoscale.

The observation also questions our current understanding of the physics of highly conductive metals, especially graphene itself.

The simultaneous existence of such seemingly incompatible properties, with electrons behaving like bullets and a liquid in the same material prompts a fundamental rethinking about our understanding of materials properties.

Professor Polini commented: “Giving decades long efforts to find even minor signs of a viscous flow in metals, we were flabbergasted that graphene exhibited not just some small blip on an experimental curve but the clear qualitative effect, a large backflow of electric current.”

Sir Andre Geim, who received a Nobel Prize for graphene, added: “Graphene cannot stop amazing us. Now we need to think long and hard how to connect such contradictory behaviour as ballistic motion of electrons, which is undoubtedly seen in graphene, with this new quantum weirdness arising from their collective motion. A strong adjustment of our understanding of the physics is due.”

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

Negative local resistance caused by viscous electron backflow in graphene by D. A. Bandurin, I. Torre, R. Krishna Kumar, M. Ben Shalom, A. Tomadin, A. Principi, G. H. Auton, E. Khestanova, K. S. Novoselov, I. V. Grigorieva, L. A. Ponomarenko, A. K. Geim, M. Polini. Science  11 Feb 2016: pp. DOI: 10.1126/science.aad0201

This paper is behind a paywall.

Here’s an image supplied by the University of Manchester illustrating the discovery,

Courtesy University of Manchester

Courtesy University of Manchester

Making carbon nanoparticles at home with honey or molasses

No need to rush and buy any ingredients as the University of Illinois at Urbana-Champaign researchers do not provide a recipe for cooking up carbon nanoparticles. However, it is diverting to think that one day we might be able to make these items at home. From a June 19, 2015 news item by Stuart Milne on the Azonano website,

Researchers at the University of Illinois have discovered an easy method to produce carbon nanoparticles for biomedical applications. These carbon nanoparticles can be made at home within a couple of hours using easily available ingredients and molasses.

A June 19 (?), 2015 University of Illinois at Urbana-Champaign news release (also on EurekAlert) provides more detail about the research,

“If you have a microwave and honey or molasses, you can pretty much make these particles at home,” Pan [professor Dipanjan Pan] said. “You just mix them together and cook it for a few minutes, and you get something that looks like char, but that is nanoparticles with high luminescence. This is one of the simplest systems that we can think of. It is safe and highly scalable for eventual clinical use.”

These “next-generation” carbon spheres have several attractive properties, the researchers found. They naturally scatter light in a manner that makes them easy to differentiate from human tissues, eliminating the need for added dyes or fluorescing molecules to help detect them in the body.

The nanoparticles are coated with polymers that fine-tune their optical properties and their rate of degradation in the body. The polymers can be loaded with drugs that are gradually released.

The nanoparticles also can be made quite small, less than eight nanometers in diameter (a human hair is 80,000 to 100,000 nanometers thick).

“Our immune system fails to recognize anything under 10 nanometers,” Pan said. “So, these tiny particles are kind of camouflaged, I would say; they are hiding from the human immune system.”

The team tested the therapeutic potential of the nanoparticles by loading them with an anti-melanoma drug and mixing them in a topical solution that was applied to pig skin.

Bhargava’s [professor Rohit Bhargava] laboratory used vibrational spectroscopic techniques to identify the molecular structure of the nanoparticles and their cargo.

“Raman and infrared spectroscopy are the two tools that one uses to see molecular structure,” Bhargava said. “We think we coated this particle with a specific polymer and with specific drug-loading – but did we really? We use spectroscopy to confirm the formulation as well as visualize the delivery of the particles and drug molecules.”

The team found that the nanoparticles did not release the drug payload at room temperature, but at body temperature began to release the anti-cancer drug. The researchers also determined which topical applications penetrated the skin to a desired depth.

In further experiments, the researchers found they could alter the infusion of the particles into melanoma cells by adjusting the polymer coatings. Imaging confirmed that the infused cells began to swell, a sign of impending cell death.

“This is a versatile platform to carry a multitude of drugs – for melanoma, for other kinds of cancers and for other diseases,” Bhargava said. “You can coat it with different polymers to give it a different optical response. You can load it with two drugs, or three, or four, so you can do multidrug therapy with the same particles.”

“By using defined surface chemistry, we can change the properties of these particles,” Pan said. “We can make them glow at a certain wavelength and also we can tune them to release the drugs in the presence of the cellular environment. That is, I think, the beauty of the work.”

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

Tunable Luminescent Carbon Nanospheres with Well-Defined Nanoscale Chemistry for Synchronized Imaging and Therapy by Prabuddha Mukherjee, Santosh K. Misra, Mark C. Gryka, Huei-Huei Chang, Saumya Tiwari, William L. Wilson, John W. Scott, Rohit Bhargava, and Dipanjan Pan. Small
DOI: 10.1002/smll.201500728 Article first published online: 20 MAY 2015

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

This paper is behind a paywall.

Honey nanofibres tested as scaffolding for wound dressing in an Iran-Netherlands collaboration

It’s taken me a while to get to this one but I can’t resist this honey-enabled technology any longer. According to a Sept. 19, 2013 news item on Nanowerk, honey, a well known antibiotic, has been used in a new technique for wound dressings (Note: A link has been removed),

Researchers applied electrospinning process and produced a drug-carrying nanofibrous web to be used in wound dressing by using an artificial and biodegradable polymer and honey as a natural polymer (“A novel honey-based nanofibrous scaffold for wound dressing application”).

A wide range of biological and biodegradable materials have been electrospun in recent years to produce nanofibers. In this research, a drug carrying nanofibrous web was produced to be used in wound dressing by using an artificial and biodegradable polymer and a natural polymer through electrospinning method.

The Sept. 19, 2013 Iran National Nanotechnology Initiative Council (INIC) news release, which originated the news item, mentions honey’s antibiotic properties and explains how its application in this new technique for wound dressing,

Honey has antibacterial and anti-inflammation properties. Many studies have been published on the effects of honey in the treatment of infections and in prevention of the wound from being infected. Therefore, the combination of the unique properties of nanofibers and the natural properties of honey in the production of wound dressing is the most important characteristic of this research.

SEM [scanning electron microscope] and AFM [atomic force microscope] results showed that the fibers were completely homogenous with relatively smooth surface. However, spindle-like beads were observed in nanofibers containing 60% honey. As the concentration of honey increased in the mixture, a decrease was observed in the diameter of nanofibers. Drug-loaded nanofibers, too, had relatively smooth and homogenous surface, and as the amount of drug increases, the diameter of the nanofibers decreased. Drug release behavior studies demonstrated a sudden initial release. Statistical analyses showed that the presence of honey did not have significant effect on the process or on the behavior of drug release. Therefore, electrospun nanofibers that contain honey are appropriate option to be used in wound dressing.

Wounds can be dressed faster by using the achievements of this research. Honey is considered as a well-known drug in traditional medical sciences, which has been loaded with drugs in this research.

The research paper’s (a link and citation will be provided further down) abstract provides a bit more detail,

In this study, nanofiber meshes were produced from aqueous mixtures of poly(vinyl alcohol) (PVA) and honey via electrospinning. The Electrospinning process was performed at different PVAs to honey ratios (100/0, 90/10, 80/20, 70/30, and 60/40). Dexamethasone sodium phosphate was selected as an anti-inflammatory drug and incorporated in the electrospinning solutions. Its release behavior was determined. Uniform and smooth nanofibers were formed, independent of the honey content. In case honey content increased up to 40%, some spindle-like beads on the fibers were observed. The diameter of electrospun fibers decreased as the ratio of honey increased. The release characteristics of the model drug from both the PVA and PVA/honey (80/20) nanofibrous mats were studied and statistical analysis was performed. All electrospun fibers exhibited a large initial burst release at a short time after incubation. The release profile was similar for both PVA and PVA/honey (80/20) drug-loaded nanofibers. This study shows that an anti-inflammatory drug can be released during the initial stages and honey can be used as a natural antibiotic to improve the wound dressing efficiency and increase the healing rate.

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

A novel honey-based nanofibrous scaffold for wound dressing application by  H. Maleki, A. A. Gharehaghaji, and P. J. Dijkstra.
Journal of Applied Polymer Science, Volume 127, Issue 5, pages 4086–4092, 5 March 2013 (Article first published online: 29 MAY 2012) DOI: 10.1002/app.37601

Copyright © 2012 Wiley Periodicals, Inc.

This article is behind a paywall.

One final note, the researchers are from (Maleki and Gharehaghaji) Amirkabir University of Technology, Tehran, Iran and (Dijkstra) the University of Twente, Enschede, The Netherlands