Benefits of oxidation and size reduction of graphene/graphene oxide nanoparticles in biosensing application: Classification of graphene/graphene oxide nanoparticles

Graphene nanoparticles (GNPs) have become increasingly attractive nanomaterials in their application in various biosensing platforms. Several benefits from the size reduction distinguish them from graphene (Gr) and graphene (GO), resulting from the electron confinement to smaller surfaces and increased edge-plane ratio. This allows for higher electrochemical activity due to the increased edge density and introduction of bandgap related photoluminescence even in GNPs that do not contain oxygen functional groups. The oxygenated counterparts, although less electrochemically active, are endowed with improved dispersibility and stability. Few aspects will be discussed in the presented review: a) the advantages and disadvantages of Gr and GO, regarding their electrical and optical properties; b) the properties of GNPs and their oxygen-containing analogs (GONPs) gained by the size reduction and quantum confinement effect; c) a clear distinction of GNPs/GONPs as nanoscale forms compared to the microscale Gr/GO; d) presenting a definition of GNPs and proper classification of the special forms of GNPs, graphene nanoribbons (GNRs) and graphene quantum dots (GQDs); e) summary of the proposed GNP biosensors will be provided, as classified into three main sections: GNPs, GNRs, and GQDs, with separate subsections for their oxygenated equivalents.