Since I was going on yesterday about the need to validate tool reagents, I wanted to note that this problem is not confined to biochemical applications. Here’s an article looking at commercial sources of graphene, the carbon monolayer material that’s been the subject of so much research the last few years. There are a number of ways to produce it, starting with the famous tape-peeling method, which doesn’t exactly scale to commercial production. And there are quite a few commercial suppliers, with the usual footnote that it can be hard to tell who might be reselling material from someone else.
And as the paper shows, the commercial graphene supply is a mess. The first problem apparently is that a number of things labeled as graphene are actually graphene oxide or its reduced form. That’s a brute-force way of exfoliating graphene sheets by absolutely oxidizing the crap out of the bulk material with a hot mixture of potassium permanganate, sodium nitrate, and sulfuric acid (which will indeed oxidize the crap out of most anything you toss into it). The graphene sheets get riddled with epoxides, hydroxys, and COOH groups, breaking the layers away from each other, and graphene oxide itself is its own field of study. But it sure isn’t graphene. You can partially reduce the material back toward graphene (rGO, reduced graphene oxide) but this is yet another amorphous material, full of random defects, that is also not graphene. But there are plenty of labeled vials for sale that claim otherwise.
Once you’ve hacked your way past that stuff, there are plenty of quality control issues with graphene itself. The real thing is a single carbon atom layer thick, and has very interesting properties. But all the methods for its production (including the tape) give you mixtures of multilayer species that have to be purified. The properties of these get progressive less unusual, and by the time you’re up to 10 layers thick it’s basically indistinguishable from bulk graphite, which needless to say is a heck of a lot cheaper than graphene. Guess what you’re buying, though. The authors of this paper analyzed material from 60 different suppliers worldwide:
The lack of standards for graphene has been stalling the development of graphene applications due to the bad quality of the material sold in the open market. There is a lot of confusion and misinformation in the graphene application’s market leading to unreliability and senseless pricing schemes. . .
. . .As one can clearly see, the majority of the companies are producing less than 10% graphene content and no company is currently producing above 50% graphene content. This result may come as a surprise given the widely advertised graphene “fever” of the last decade. However, it also helps to understand why graphene applications are not commonplace yet.
Yeah, I’ll bet it does. It also leads to the immediate conclusion that a great deal of the graphene literature, the part from people that didn’t carefully produce and purify their own graphene and chose to believe what was on the label instead, must be close to worthless. It appears that the majority of companies are producing what would be better named “finely divided graphite particles”, thick three-dimensional chunks on the nanoscale that have little or nothing to do with graphene.
Furthermore, it is worrisome that producers are labeling black powders as graphene and selling for top dollar, while in reality they contain mostly cheap graphite. This kind of activity gives a bad reputation to the whole industry and has a negative impact on serious developers of graphene applications.
Indeed. It’s not so worrisome for the producers, though – the less ethical ones might consider switching to carbon black as an even cheaper alternative, since it’s not going to perform any worse than the crap they’re selling now. I should note, though, that there are a couple of companies whose material apparently consists of only 30 to 40% carbon at all, which is really impressive, although not in the good way. What the hell the rest of it might be is a good question. As is often the case in these sorts of papers, suppliers do not appear to be named. But at some level, it hardly matters: not one single supplier, in case you’re wondering, manages to sell anything near pure monolayer graphene. The average of even the better end of the scale is four-layer material.
So in case it’s needed, here’s yet another warning. If you’re buying any material/reagent/chemical tool that’s the least bit interesting, unusual, crucial to your research in any way, or (especially) that is for some reason difficult to produce, don’t just take their word for it. Characterize it. Assay it. Make sure it’s what it’s supposed to be. Unless you’re really into wasting your time and everyone else’s.
Update: here’s Nature on the same topic.