Chemical Preparation of Graphene Materials Results in Extensive Unintentional Doping with Heteroatoms and Metals

Abstract

Chemical synthesis of graphene relies on the usage of various chemical reagents. The initial synthesis step, in which graphite is oxidized to graphite oxide, is achieved by a combination of chemical oxidants and acids. A subsequent chemical reduction step eliminates/reduces most oxygen functionalities to yield graphene. We demonstrate here that these chemical treatments significantly contaminate graphene with heteroatoms/metals, depending on the procedures followed. Contaminations with heteroatoms (N, B, Cl, S) or metals (Mn, Al) were present at relatively high concentrations (up to 3 at%), with their chemical states dependent on the procedures. Such unintentional contaminations (unwanted doping) during chemical synthesis are rarely anticipated and reported, although the heteroatoms/metals may alter the electronic and catalytic properties of graphene. In fact, the levels of unintentionally introduced contaminants on graphene are often higher than typical levels found on intentionally doped graphene. Our findings are important for scientists applying chemical methods to prepare graphene.

Carbocatalysis: The State of “Metal‐Free” Catalysis

“…These metallic impurities can include Mo, Co, Fe, Ni, and Cu. Further chemical treatments involving concentrated acids and strong oxidants further introduce unwanted metallic and heteroatom impurities into the chemically modified graphene materials (Scheme ) 10. For example, the Hummers oxidation method, involving the treatment of graphite with potassium permanganate, usually results in the embedment of manganese impurities.…”

Graphite sulphate – a precursor to graphene

“…This observation is in agreement with a recent study on the contamination of GO by chemical treatment. 19 TGA data further reveal that water is the major species detected between 250 1C and 350 1C which contributes mostly to the main weight-loss. A structure containing hydroxyl groups is further supported by FTIR spectroscopy (Fig.…”

“…Additionally, manganese impurities in graphene based materials should be avoided because they disturb their properties in applications. [19][20][21] Here, it is demonstrated for the first time that processable oxo-functionalised graphene is yielded from graphite sulphate (Scheme 1), which is a precursor to G 1 and G few-layer with an unprecedented low density of defects of about 0.06% on average with a reasonable size of flakes of about 1-5 mm.…”

Chemistry of Graphene Derivatives: Synthesis, Applications, and Perspectives

“…Organosilanes were used to create a template matrix by sol‐gel process and after washing out the glycoprotein, the graphene oxide–boronic acid matrix showed high recognition ability towards the same molecule, due to synergistic boronic acid recognition and graphene surface . Also, the simple reduction of graphene oxide by borohydride led to the boron introduction on graphene and its concentration can even exceed hundreds of ppm …”

“…[136] Also, the simple reduction of graphene oxide by borohydridel ed to the boron introduction on graphene and its concentrationc an even exceed hundreds of ppm. [137] Phosphorus modified graphene applicationsa re quite scarse due to low number of these materials, although these derivatives could be very promising. So far,t he materialc ontaining phosphonic acids groups on the edges of graphene sheete xhibited flame retardant properties and was used as materialfor the improvement of fire safety in cotton fabrics.…”