@ Ym, the brown powder is graphite oxide. The graphite oxide to be exfoliated in water using sonication, ultimately producing single or few layer graphene, known as graphene oxide (GO).The main difference between graphite oxide and graphene is thus the number of layers.

Dear Ym Kim,

Graphite oxide is a compound made up of carbon, hydrogen and oxygen molecules. It is artificially created by treating graphite with strong oxidisers such as sulphuric acid. These oxidisers work by reacting with the graphite and removing an electron in the chemical reaction. This reaction is known as a redox (a portmanteau of reduction and oxidisation) reaction, as the oxidising agent is reduced and the reactant is oxidised.

The most common method for creating graphite oxide in the past has been the Hummers and Offeman method, in which graphite is treated with a mixture of sulphuric acid, sodium nitrate and potassium permanganate (a very strong oxidiser).

Graphite oxide and graphene oxide are very similar, chemically, but structurally, they are very different. The main difference between graphite oxide and graphene oxide is the interplanar spacing between the individual atomic layers of the compounds, caused by water intercalation. This increased spacing, caused by the oxidisation process, also disrupts the sp2 bonding network, meaning that both graphite oxide and graphene oxide are often described as electrical insulators.

In order to turn graphite oxide into graphene oxide, a few methods are possible. The most common techniques are by using sonication, stirring, or a combination of the two. Sonication can be a very time-efficient way of exfoliating graphite oxide, and it is extremely successful at exfoliating graphene (almost to levels of full exfoliation), but it can also heavily damage the graphene flakes, reducing them in surface size from microns to nanometres, and also produces a wide variety of graphene platelet sizes. Mechanically stirring is a much less heavy-handed approach, but can take much longer to accomplish.

Hummer's Method produces graphite oxide (oxidized graphite) and is comprised of many layers of graphene oxide. In order to produce graphene oxide (single-layer or few layer GO), you need to exfoliate the graphite oxide in a solvent of your choice (usually ultrapure water) which is typically done by sonication. When you remove the solvent, the "single-layer or few-layer GO" stacks together (and hence collectively known as graphite oxide). As highlighted by the previous answers, the intercalation of graphite oxide with water molecules (or any other solvent molecules) is the distinguishing feature of "GO". With regards to your first question, AFM can distinguish whether you produced a single-layer GO, few-layer GO, or bulk graphite oxide. Hence, this is one of the standard characterization done when using GO. IR spectra, raman spectra, and XPS spectra are good characterization techniques to identify the functional groups present in GO. Thus, it can be used to distinguish GO from graphite because of their different chemical signatures.

Its only graphite oxide since it contains numerous layer. From Graphite Oxide to Graphene Oxide While graphite is a three dimensional carbon based material made up of millions of layers of graphene, graphite oxide is a little different. The main difference between graphite oxide and graphene oxide is, thus, the number of layers.