Sciencemadness Discussion Board - Would someone like to try this? Graphene Production

Would someone like to try this? Graphene Production

Manifest - 19-4-2014 at 17:30

http://cen.acs.org/articles/92/web/2014/04/Solution-Graphene-Production.html
Graphene is easy to acquire, at least in small amounts. The first scientists to isolate the strong, two-dimensional carbon material simply pressed a piece of Scotch tape to a chunk of graphite and peeled it off. But mass production of graphene for commercial uses remains a challenge. Now, scientists have shown they can rapidly produce large quantities of graphene using a bath of inorganic salts and an electric current (J. Am. Chem. Soc. 2014, DOI: 10.1021/ja5017156).
Several other methods have been developed for producing graphene, but each has its drawbacks. Growing the carbon sheets takes too long, and chemical vapor deposition requires a metal catalyst, with a second step to remove the metal. Other methods using solvents or surfactants can harm the electronic properties of graphene or produce lower yields.
Xinliang Feng and Klaus Müllen of the Max Planck Institute for Polymer Research, in Mainz, Germany, and their colleagues decided to improve upon an electrochemical technique for producing graphene. Instead of using acids, which oxidize the graphene and reduce its conductivity, the researchers prepared solutions of various salts, including ammonium sulfate, potassium sulfate, and sodium sulfate. Into their mixtures they placed two electrodes, one made of platinum and the other of graphite, which is essentially a conglomeration of many layers of graphene. When they ran 10 V of direct current through the graphite electrode, it began to shed layers into the solution, a process called exfoliation. They kept the current running for three to five minutes, separated the exfoliated flakes from the solution, and washed away excess salt with water.
The process turned more than 75% of the graphite electrode into graphene flakes. Approximately 85% of the flakes consisted of one to three layers of graphene—the most desirable electrical properties come from single and double layers of graphene.
Of the solutions they tested, the ammonium sulfate worked the best, producing the highest quality graphene in the fastest time. In one test, the researchers were able to produce approximately 16.3 g of graphene in 30 minutes. But Feng sees the potential to scale up production to the kilogram scale needed for industrial use.
James M. Tour, a synthetic organic chemist at Rice University, calls the work “very nice—not the first time such electrochemical exfoliation has been done, but the authors here get it to work more efficiently.”
The exfoliation process is also more environmentally friendly than previous methods for generating graphene, Feng says, and doesn’t require high temperatures. He plans to test other electrolytes as well as different forms of graphite in an effort to scale up the process. The individual sheets of graphene, however, are still very small, at most a few millimeters across. Producing sheets on the centimeter scale, to build something like a transparent electrode, remains difficult, Feng says.
To demonstrate a use of their graphene, the team mixed the powder they produced into N,N’-dimethylformamide to produce a graphene ink, which they painted in a thin film on a piece of paper. They used two pieces of treated paper to make a supercapacitor, showing the material’s potential use in flexible electronics.

WGTR - 19-4-2014 at 18:23

Wow. Thanks for posting that (both you and Morgan). I'll definitely be trying it, but probably not right away. I have a
few things on my plate already.

I need to read through the article in a quiet moment (don't forget the supplementary article too). The main thing is that
the surface area needs to be very high, and it needs to stay that way once deposited on a substrate. I'll look into it when I
get the chance.

IrC - 20-4-2014 at 00:39

Chemistry is not my area of study but I do dabble somewhat with what I know. So hopefully this question is not too dumb to ask since making Graphene really interests me. I cannot afford Platinum electrodes. If I used ammonium sulfate with graphite for one electrode, would it work to use Titanium or Tungsten for the other electrode. Or is there some undesired chemical reaction going to take place? Or would it not work at all without Platinum?

Baffled - 20-4-2014 at 02:54

Please, if you try any of this yourself, do so in a fume-hood. Graphene might be a lot less benign than previously assumed:
http://news.brown.edu/pressreleases/2013/07/graphene

Small scale human testing has already begun, given the absence of any "don't try this at home, you might get cancer" warning: http://www.scientificamerican.com/slideshow/diy-graphene-how...

Mildronate - 20-4-2014 at 04:13

How do you will know that is graphene? YOu need SEM then.

forgottenpassword - 20-4-2014 at 08:03

I have made graphene with sellotape and a graphite pencil. It is a useless product!

HgDinis25 - 20-4-2014 at 08:22

Baffled, I think that calling Graphene a potential carcinogenic is way out of line. C'mon we all use pencils. Pencils are made of Graphite and simply painting your skin with it will make tiny quantities of Graphene. So, let's brand pencils as non benign objects?

I would find it quite disturbing that the odds of Graphene going through cell membranes and entering the nucleus were to be that high, like described in the articles.

one atom thick

quantumchromodynamics - 20-4-2014 at 08:22

what can the home scientist do with one atom thick carbon sheets?

IrC - 20-4-2014 at 08:25

Useless to whom? Productive posts please. I have a big square that floats in air above 4 NdFeB magnets. Not useless to me it is cool to see it levitating. I wish to experiment using Graphene to create negative resistance relaxation oscillation. My question is will Titanium or Tungsten work for an electrode.

HgDinis25 - 20-4-2014 at 08:33

Quote: Originally posted by quantumchromodynamics

what can the home scientist do with one atom thick carbon sheets?

Being able to produce onte atom thick carbon sheets should alone be rewarding enough.
On top of my head, I remember the awsome Graphene Supercapacitators. Look around the internet and you'll find plenty of information about them.

http://www.technologyreview.com/view/521651/graphene-superca...

froot - 20-4-2014 at 08:48

I'm sure you can use a carbon electrode, Pt was used to ensure no other chemistry complicated the results. Worst case scenario you'd need to replace your solution more frequently. For one graphene would be useful in photovoltaics as a flexible transparent conductor.

forgottenpassword - 20-4-2014 at 09:16

Quote: Originally posted by IrC

I have a big square that floats in air above 4 NdFeB magnets.

How big is your big square?

aga - 20-4-2014 at 12:19

Does anyone know how the chemistry of the Edges of a graphene sheet work ?

Specifically, if you made, say, two 1mm sheets, could you combine them into 1 sheet ?

Making a 1mm squared sheet would not be too useful.

[Edited on 20-4-2014 by aga]

IrC - 20-4-2014 at 13:58

Quote: Originally posted by forgottenpassword

Quote: Originally posted by IrC

I have a big square that floats in air above 4 NdFeB magnets.

How big is your big square?

Around 25 mm square. Unsure how thin and too fragile to find out without risking it. Pretty thin. Supports the weight of a fly landing on it without touching the magnets. In fact it has a surprisingly large force holding it up. Surely you have seen one of these they are a common toy among geeks. The point being in answer to the "what good is it" question I do not own any other substance that will defy gravity by virtue of its diamagnetism with this much force. Have tried with Bi but Graphene has the highest level I have ever encountered. Along the lines of a frog floating in a superconducting magnet strong.

http://www.youtube.com/watch?v=xoj_fVVZuxc

My sheet looks very similar to the video except I use 4 1.25 inch square by 3/4 inch thick N48 magnets. You can carefully direct a stream of air to make it spin incredibly fast. Not too long ago scientists showed it was the fastest spinning thing (material object) we know.

http://www.newscientist.com/article/dn19514-levitating-graph...

I thought every geek had a toy made from Levitating Pyrolytic Graphene?

http://www.ebay.com/itm/Pyrolytic-Graphite-1x1-cm-piece-neod...

Get your geek toy here $6.95 free shipping. Then whenever anyone asks what good is it explain the endless hours of amusement you derive from your toy.

I like the words this seller put on his page since it is hard to find cheap sources of large sheets.

"I can provide bigger pieces (like, 20x20 mm or even 100x100 mm) for the price of 6$ per square cm (massive discounts for larger pieces are possible) or combine several items if you need. I can also cut any form of any size up to 200x300 mm for the same price of 6$."

After reading this auction page I am talked into getting some N52 magnets to raise the square a little higher while it supports even more weight. Of course at the time I acquired this toy not even N50 was available from my usual hacker supply sources.

At least not as boring as watching pitch drop. This guy watched for 50 years only to pass away a year before it dropped:

http://www.newscientist.com/article/dn25441-longest-experime...

Hard to believe no one here has tried this:

http://www.newscientist.com/article/dn25442-make-graphene-in...

[Edited on 4-20-2014 by IrC]

WGTR - 20-4-2014 at 15:32

Graphene is merely the future of energy storage. It's absolutely useless. I have no idea why anyone would be interested in it. :cool:

Pristine graphene is hydrophobic, and does not disperse into 100% water. It also permanently restacks into graphite sheets if you allow it to settle out.

The particular flavor of graphene that is usually encountered is its partially oxidized form, graphene oxide. Depending on how it was oxidized, there are different carbon/oxygen ratios, and different functional groups that are attached to the graphene sheets. Generally, single and few layered graphene oxide disperses well into water, provided that the pH is neutral and the extraneous salts have been washed out. The thicker pieces precipitate out of solution upon centrifugation, giving a means of separating the exfoliated sheets from the non-exfoliated ones.

What the article is describing, at first glance, is a process of oxidation and exfoliation by which minimal oxygen is introduced into the graphene. In fact, it gives the highest C/O ratios of any process that they compared to. Also, manganese is not introduced, producing less hazardous waste as compared to the typical oxidative processes. This also requires less washing of the graphene afterwards, giving a purer and more suitable product for electrochemical studies. Strong acids and oxidizers are not used, eliminating the risk of explosions from overheating (Mn2O7 is unstable, etc). (NH4)₂SO₄ is fertilizer. So they have essentially reported an easy and non-toxic way of synthesizing low-oxygen graphene.

An important application of graphene is the preparation of high surface area electrodes for supercapacitors. If you look at the SEM images of their product, the sheets of graphene expand out and wrinkle. This wrinkling is good, because it maintains high internal surface area and minimizes the tendency for the layers to restack. High surface area and conductivity are paramount in a capacitor. This translates directly into high capacity and low ESR. Their material has a reported density of 50 farads per gram. This is high, but relatively low compared to the theoretical (250F/g, depending on how you measure it).

The thicker the graphene layers, the less access the electrolyte has to the internal layers of graphene, and the lower the specific capacitance at a given CV scan rate. This is obvious from figure S17. Also, the expansion and wrinkling of the graphene layers is not optimal, which explains why the specific capacitance does not approach the theoretical values. In spite of this, their research is still quite invaluable. It certainly got me excited. Undoubtedly there will be more research that involves getting the most surface area out of this type of process. This is just the beginning.

I think ammonium sulfate is fairly stable. If the electrolyte were ammonium nitrate, the nitrate ion could get reduced, even all the way to ammonia, at the cathode. With a copper cathode, and a platinum anode, a nitric acid solution will go decidedly basic as ammonia is produced. In this case, I think a platinum cathode was used out of habit. Anyway, I have a platinum electrode, so I'll use that just to be sure.

Chemosynthesis - 20-4-2014 at 16:17

Quote: Originally posted by HgDinis25

Baffled, I think that calling Graphene a potential carcinogenic is way out of line. C'mon we all use pencils. Pencils are made of Graphite and simply painting your skin with it will make tiny quantities of Graphene.

According to some biophysicists I know, that's not the case, and the size/diameter of the graphene produced can be very damaging to cells. Merely writing with a pencil may not produce the proper angle, diameter, etc. for significant penetration past the epidermis.

Additionally, inhalation may be most dangerous as the lungs are highly vascularized and may afford entry into systemic circulation, which is very dangerous from a toxicological standpoint.

Baffled - 21-4-2014 at 05:53

Well, at least we can just burn the waste, try doing that with asbestos!

forgottenpassword - 21-4-2014 at 08:12

Quote: Originally posted by WGTR

Graphene is merely the future of energy storage.

Good luck with that. It looks like soot to me. http://www.appliedgraphenematerials.com/products/graphene-po...
In fact it is soot! There's one born every minute.

IrC - 21-4-2014 at 08:56

Quote: Originally posted by forgottenpassword

Quote: Originally posted by WGTR

Graphene is merely the future of energy storage.

Good luck with that. It looks like soot to me. http://www.appliedgraphenematerials.com/products/graphene-po...
In fact it is soot! There's one born every minute.

Enough with the useless posts. If you think Graphene is useless why talk about it? Try studying these patents on the subject.

http://www.freepatentsonline.com/result.html?sort=relevance&...

WGTR - 21-4-2014 at 10:14

I managed to oxidize some flake graphite using an adaption of the electrochemical method.

I thought I had graphite foil, but it turned out to be some strange paper made from carbon squiggles. It exfoliated in a really weird and useless way. Instead, I took some Asbury 3061 flake graphite, and bound up a gram into a small cloth pouch. Contact with the graphite flake was made with a platinum anode. A graphite cathode was used, which did not deteriorate during operation. 0.1M ammonium sulfate was used (straight out of the 20lb bag of fertilizer) as an electrolyte, with no purification. 10V was applied across the cell, and about 0.5A was maintained. After 30 minutes the graphite flake was washed out of the pouch and into a separate beaker. Some flakes were unchanged, but many of them appeared much darker than usual. Upon closer inspection under a microscope, these flakes had expanded out like an accordion, like a graphene slinky. Basically, the graphite changed from flat flakes into expanded columns that were a couple of times taller than their width. It was pretty neat, actually.

After washing this stuff out with a large volume of DI water on filter paper, small amounts were added to DMF and sonicated. After about 10 minutes, the graphene was mostly exfoliated and dispersed into the DMF solvent, where it has remained stable for at least 8 hours. Much of the graphite was not oxidized enough, and did not exfoliate, sinking to the bottom of the solution after several hours of settling. The solution itself remained dark, however. Some parameters need to be adjusted to improve the oxidation.

I'd like to get some of the expanded graphite into the SEM to get some pictures, but it may be a while before I can do this. I have a day job.

Quote: Originally posted by forgottenpassword

In fact it is soot! There's one born every minute.

There are actually several different forms of carbon. The soot you are describing may contain a mix of amorphous carbon, graphite, graphene, carbon nanotubes, random tars and other organic junk. Getting the desired form of carbon in suitable purities can be quite difficult. Ask any guy who's had to shell out big bucks to buy a carbon rock for his girl.

HgDinis25 - 21-4-2014 at 11:37

Quote: Originally posted by Chemosynthesis

Quote: Originally posted by HgDinis25

Can you please provide some references? It has caught my atention and I would like to study more about the subject. What about carbon nanotubes? This might seem insane, but could you stab someone with a huge carbon nanotube without someone even knowing it? (scientific fiction I guess)

IrC - 21-4-2014 at 12:45

Quote: Originally posted by WGTR

I thought I had graphite foil, but it turned out to be some strange paper made from carbon squiggles. It exfoliated in a really weird and useless way.

Thinking about building a Graphene layer lead me to reading this patent:

Graphene deposition and graphenated substrates (United States Patent 8487296)

Attachment: US8487296B2.pdf (490kB)
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forgottenpassword - 21-4-2014 at 12:48

Quote: Originally posted by IrC

Quote: Originally posted by forgottenpassword

Quote: Originally posted by WGTR

Graphene is merely the future of energy storage.

Good luck with that. It looks like soot to me. http://www.appliedgraphenematerials.com/products/graphene-po...
In fact it is soot! There's one born every minute.

Enough with the useless posts. If you think Graphene is useless why talk about it? Try studying these patents on the subject.

http://www.freepatentsonline.com/result.html?sort=relevance&...

How is it a useless post? Some people may not know that graphene is produced as a soot by the combustion of ethanol in air. I linked to a website that both describes the process and shows the product from the world's largest supplier of graphene. You linked to freepatentsonline. Thanks for that!

[Edited on 21-4-2014 by forgottenpassword]

IrC - 21-4-2014 at 13:28

forgottenpassword "I linked to a website that both describes the process and shows the product from the world's largest supplier of graphene. You linked to freepatentsonline. Thanks for that!"

I provided a link to a search at 'freepatentsonline' for reasons stated below. Also I uploaded what I thought was a useful PDF to this site. Even if I had so what? Your "Thanks for that!" remark after mentioning your link in a way which implies it is 'more useful' and mine is therefore 'less useful' is not very productive to the subject at hand. Everyone should be able to feel free to provide information and sources they believe is on topic and useful without fear of being belittled.

Is studying patents on the subject a waste of time? Is freepatentsonline a useless resource? Is there a point to this hijack adding further useless discourse on the stated subject?

Title of thread: Would someone like to try this? Graphene Production

Comments not adding useful input to the science behind the subject:

"It is a useless product!"

(Originally posted by WGTR "Graphene is merely the future of energy storage")

Your IMHO 'useless' comment to WGTR as addition to the subject (sans link which is useful):

"Good luck with that."
"It looks like soot to me."
"In fact it is soot!"
"There's one born every minute."

Then there is the additional post I am replying to now which fails to further information on the subject in the thread title. I did not like the replies I quoted above so I said something about it. Get over it. To actually provide more useful information here is a few more patents:

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Attachment: US20090155561A1.pdf (182kB)
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Attachment: US7619257B2.pdf (91kB)
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While I may not have the infinite intellect some may require to make posts on this site, it seems clear to me comments such as "It is a useless product!" and "There's one born every minute." are not very helpful to the OP's reason for this thread. My adding a list of or posting patents was merely in reply, to show real world uses for the as you say 'useless product'.

Chemosynthesis - 21-4-2014 at 13:36

Quote: Originally posted by HgDinis25

References for which part? I could try and ask the biophysicist colleagues, but it seems to make sense to me given that pressure is dependent on surface area, and lipophilic absorption through various means also relies on surface area and molecular size as well as partition coefficient. I cited a paper or two on nanotube drag forces. Two excellent examples of that principle in action are through the colon with ingestion and subcutaneous injection.

Additionally, I can think of two mechanisms by which lung tissue is toxicologically important, both stemming from vascularization. One is access to systemic circulation of your toxic agent, and the other is easy access of the immune system to the lung. I could look through my shelf at work for the perfect review paper, but lung cancer (among others, such as breast, etc.) is often associated with inflammation.

It gets a little contentious to make claims here, depending on who is fighting for what grant, unless I start citing lots of data, but inflammation and wound healing with EMT/MET mechanisms are potentially carcinogenic by epidemiological correlation. Fine metal particles actually always present a cancer risk, but substances such as asbestos are better known for their apparent efficacy as etiological agents.

One mechanism for this in the lungs involves, presumably, Tumor Necrosis Factor (TNF) cytokines which cascade from cell signalling in mast cells, which logically have increased access to the lungs or colon due to the high amount vascularization needed for efficient gas exchange and absorption of food, respectively.

Hopefully these will provide enough of a starting point in mitigating any scepticism, but if it helps, I work in pharmacology with plenty of background in oncology, which is very toxicological in nature. If you're still dubious, let me know.
http://pubs.acs.org/doi/abs/10.1021/nn102763b
http://experts.umn.edu/pubDetail.asp?n=David+Y+Pui&u_id=...

http://aje.oxfordjournals.org/content/148/3/241.full.pdf
http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/cobalttung...
http://oes.tamu.edu/guidelines/Nanotechnology/Inhalation_Tox...
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2783215/
http://www.particleandfibretoxicology.com/content/11/1/3
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2367012/pdf/MI-0...
http://www.safenano.org/Portals/3/SN_Content/Documents/FEATU...
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1994795/

Edit- and yes, with a needle that thin, you could theoretically avoid hitting any neural pain fibers. Coat the exterior with a local anesthetic, perhaps an ester for rapidity of metabolism, and it's theoretically plausible the injectee wouldn't feel a thing.

It's also important to remember that cell membranes are not uniformly comprised, and show variation due to gene expression between tissue types. This could be presumed to affect the energy of penetration, and may make certain tissues more susceptible to damage. The dead epidermal layer, by contrast, requires no nutrients to its dead husk, and may act as a sponge or shield, which isn't uncommon (hence some agents requiring skin penetrating solvents, or not being contact risks).

[Edited on 21-4-2014 by Chemosynthesis]

WGTR - 21-4-2014 at 16:27

Quote: Originally posted by WGTR

I managed to oxidize some flake graphite using an adaption of the electrochemical method.

I thought I had graphite foil, but it turned out to be some strange paper made from carbon squiggles. It exfoliated in a really weird and useless way.

Well, I'm going to have to eat my socks. After several more hours, my precious exfoliated flake graphite precursor settled out of the DMF solution. It is not as exfoliated and/or oxidized as I had thought. I should have known better. It was an optically black solution. Partly oxidized graphene will have at least a bit of brown in it when it's in solution.

On the other hand, the "useless" squiggles from the graphite foil turned out to be more useful than I thought. After bumping up the anode current density a bit, the solution started turning a little brown. The ribbons of oxidized graphite were mostly floating. These were scooped out and washed with DI water, and then sonicated in DMF. There is still a lot of unexfoliated graphite/graphite oxide floating around in the solution. It will take a few days for it to settle out, probably. If it doesn't, then I'll go out back and use the centrifuge. Even now, this solution does look brown when in a strong light.

Anyway, I hope my haphazard experiments aren't too frustrating to people. I'm really short on time right now. When I can, I'll throw some stuff in the SEM and try to characterize it.

forgottenpassword - 22-4-2014 at 10:36

Graphite and a kitchen blender is today's scientific breakthrough method, knocking the Scotch tape and pencil method off the top spot! http://www.bbc.co.uk/news/science-environment-27113732

"An Irish-UK team poured graphite powder (used in pencil leads) into a blender, then added water and dishwashing liquid, mixing at high speed.

The results are reported in the journal Nature Materials."
http://dx.doi.org/10.1038/nmat3944

[Edited on 22-4-2014 by forgottenpassword]

elementcollector1 - 22-4-2014 at 11:15

Apparently, even the brand and amount of dishwasher detergent factors in? This is going to be another Potassium, where we all report tries with different brands of solvent, isn't it.

Might just try this - I used to collect broken pencil leads for obtaining graphite, but eventually threw it away as I had no real use for it.

IrC - 22-4-2014 at 15:44

I'm going with the OP's link. Ordered Ammonium Sulphate 4 lb and have graphite out the wazoo. Even have two new crucibles made of pure graphite that weigh 90 lbs each. Monsters that take up large area in storage. Don't ask no idea what they were made for but it was big whatever it was. Plus many reasonable size electrodes of graphite, and many Ti and W electrodes. But only a small amount of Pt wire, the reason for my earlier question still unanswered. Just going to try it with a Ti rod 1/2" x 12", and a similar size graphite rod and see what happens.

What I was wondering about and hope would be answered by someone good at chemistry is if I run say 10 amps through an Ammonium Sulphate solution with one electrode of graphite and the other Ti or W, do I need to worry about any undesired side reactions and products/gasses/U name it coming out of the cell?

Quote: Originally posted by elementcollector1

Apparently, even the brand and amount of dishwasher detergent factors in? This is going to be another Potassium, where we all report tries with different brands of solvent, isn't it.

On page one of this thread I posted a link to the NewScientist version of this article which gives specific info:

"The team put graphite powder and a solvent fluid in a laboratory mixer and set it spinning. Analysis with an electron microscope confirmed that they had produced graphene at a rate of about 5 grams per hour. To find out how well the process could scale, they tried out different types of motors and solvents. They discovered that a kitchen blender and Fairy Liquid, a UK brand of dishwashing liquid, would also do the job.

"If you are using a blender, why use a fancy expensive surfactant? Why not use the simplest surfactant there is, and I guess that is Fairy Liquid," says Coleman.""

I have to wonder, my bean grinder has sharper blades rotating at much higher velocity. Only question is how good is the shaft seal?

Baffled - 25-4-2014 at 14:46

This article cought me by surprise:
http://www.sciencedirect.com/science/article/pii/S0142961212...
This (supposedly) is the full article:
http://extremelongevity.net/wp-content/uploads/C60-Fullerene...
If only we had more helium, not all at once though, that wouldn't be cool

Mildronate - 27-4-2014 at 08:43

Oganic graphene analog http://pubs.acs.org/doi/abs/10.1021/ja502765n

Dan Vizine - 27-4-2014 at 13:13

A statement to the effect that graphene is the "future" of energy storage is overly broad. That graphene will be enormously important is not debated, it's the how that remains to be seen.

The real stars of energy storage into the forseable future are, naturally, the batteries that utility companies plan to use for off-peak power supply in order to make solar and wind energy practical. Nobody is talking about graphene here, where the emphasis is on inexpensive starting materials and a high number of cycles/battery. Here they talk about sea water, iron, prussian blue, zinc and manganese dioxide.

So, what electronics is graphene going to revolutionize first? Let's look at the properties.

One of the most noteworthy (although, personally, I'm more interested in the mechanical uses like gas separation, but that's a chemist for you) features of these 2D sheets is that allowable energy levels are continuous (zero bandgap, which is the energy difference between the conduction and valence bands ) and that conduction electrons behave oddly as a result. Instead of exhibiting normal fermion behavior where E is proportional to the momentum squared, in graphene the electrons (conduction), behave more like light does and E is directly proportional to momentum. The electrons literally mimic massless photons in spatial regimes defined as "Dirac cones". In these regions, conduction electrons all travel at the same high speed and so metal-like conductance is seen in something that is often more accurately called a "zero-bandgap" semiconductor.

But, the fact that no significant bandgap exists means that you can't make a transistor from it. You must open a bandgap. But, the things that open bandgaps (cutting, strain, doping) reduce electron mobility. This trade-off is the devil in the details. Actually, let me qualify that a little bit...there has been a recent proposal to open "tunable" gaps in graphene through a combination of strain and an electrostatic field that supposedly doesn't reduce electron mobility. I don't think this is proven in the lab yet and, honestly, I don't fully grasp how it works.

The important point is that, while graphene is great for supercapacitors, should improve photovoltaics and will probably be a means for increasing the energy density of Li batteries (because it can act as a very high capacity Li ion host although very significant cycling problems currently exist), so far nobody can say if graphene, a graphyne (with alkynyl bridges and less symmetrical) or even the significantly more complicated silicon analogs, silicenes, will be the material of choice in the future. For example, silicenes offer better interfacing with our existing silicon-based devices and they have their own unique Dirac cones. One hopes that we will waste less time between theoretical predictions and some kind of real-world actualization than we did with graphene, but that seems assured. We can make the latter types already, unfortunately the amounts produced are quite small so far.

Silicenes, btw, don't exhibit the simple, but elusive, silicon sp2 hybridization scheme. Thus, they are 3D sheets, more than one atom in thickness.

[Edited on 28-4-2014 by Dan Vizine]

Dan Vizine - 10-5-2014 at 06:04

Sometimes, things move fast when a huge number of scientist focus their energies. Graphene just took another big step forward, as announced about a week ago:

http://nanotechweb.org/cws/article/tech/57080

Growing graphene on hexagonal boron nitride allows the lattice mismatch to open tunable bandgaps without the performance penalties (apparently) of existing methods.

Baffled - 18-6-2014 at 14:34

http://www.youtube.com/watch?v=t5qLfHLyQKo
Did he say "eat"?

forgottenpassword - 19-6-2014 at 00:26

I have 100g of graphene powder. What can I practically do with it?

WGTR - 19-6-2014 at 04:56

Quote: Originally posted by forgottenpassword

I have 100g of graphene powder. What can I practically do with it?

That depends mostly on how it was made, assuming that what you have is in fact graphene powder. The exfoliation of graphite into graphene is easily reversable. How was it made/obtained?

forgottenpassword - 19-6-2014 at 05:29

It was made by the incomplete combustion of ethanol. There is no doubt as to its identity.

forgottenpassword - 23-6-2014 at 05:43

No suggestions at all?

WGTR - 23-6-2014 at 07:59

The reason that I asked how it was made, is because it's usefulness for different applications depends on the different functional groups that are attached to it. If it's pristine curved nano sheets of graphene, then you could grind the powder together with a plastic binder and conductive additive, and form thin super capacitor electrodes. This type of material can also be used to increase the strength, thermal conductivity, or electrical conductivity of epoxy, etc.

I'm on an iPhone right now, so I'm away from my references.

[Edited on 6-23-2014 by WGTR]

Baffled - 24-7-2014 at 18:04

Now that I think of it, I once (about 10 years ago) demolished an old vacuumcleaner and tried using the carbon brushes for the production of chlorates with some lo-salt and an old universal ac/dc adapter. I soon got tired of the rapidly heating adapter and tossed in some hand soap containing mostly sodium laureth sulfate to see if I could get the bubbles to mix enough on the surface to produce a bang.

I didn't succeed in making enough bubbles to make the two gasses to mix, but I did notice an "oily" rainbow on the surface (like this) after a couple of hours. I tossed it in the toilet thinking it was just some oil residue that made it's way into the brush from the electric motor, but I still have the flowerpot, adapter and the carbon brushes.

I'm still alive.

Edit: checked the flowerpot, it appears I have some graphene oxide (a few yellow/brownish areas a few mm² across) suspended on ceramic glazed substrate (the flowerpot). I think I should measure its resistance to be sure.

[Edited on 25-7-2014 by Baffled]