Basically, there are two different approaches proposed for the doping of graphene by heteroatom. They are (i) substitution of carbon atoms in the graphene lattice with heteroatoms and (ii) connection of atoms from the dopant source to the hexagonal network of graphene skeleton via adsorption. Between these two, substitutional doping is the most preferred one because of the formation of covalent linkage between the atom from the dopant and the carbon atoms of the graphene skeleton . Among the various elements in the periodic table, the elements such as nitrogen, boron, sulphur, phosphorus and fluorine are more recommended for the doping with graphene because their properties are similar to those of carbon. The periodic properties of various heteroatoms such as B, F, N, O, S and P are schematically depicted in Fig. . The fundamental periodic properties such as ionic radius and electronegativity which function as deciding factor for the doping of these elements with graphene network. From Fig. , the size of both boron and nitrogen are almost close to that of carbon. However, the boron is relatively less electronegative compared to carbon whereas nitrogen is more electronegative than carbon. Besides, the boron has one valence electron less than carbon while nitrogen has one valence electron excess compared to carbon. Therefore, boron exhibits electron deficient character but nitrogen displays electron rich behaviour. Normally B undergoes sp 2 hybridisation while N undergoes both sp 2 and sp 3 hybridisation. Next for P-doping, the structure of graphene is severely perturbed as the size of P is comparatively higher than N. The electron density around the carbon atom in C-P bond is higher than that in C-N bond as the electronegativity of P is lower than C. Another interesting aspect in the graphene after doping with N and P is the structural variation which could be described to the fact that the graphitic N is planar whereas the graphitic P is pyramidal overhang. Unlike other heteroatoms, S-doping causes minor polarization of C-S bond as the electronegativity of S is very much close to that of C. As a result, curved carbon nanostructure is generated by S-doping instead of flat graphene. Halogens are extremely reactive among the p-block elements and has one electron short to achieve the stable octet configuration. When the graphene gets doped with halogens, then it leads to the variation in the hybridisation of carbon from sp 2 to sp 3 . This end up with serious distortions in the structure of graphene which is particularly maximum in Br owing to its bigger size . Among the halogens, fluorine is smaller in size which makes it convenient to completely screen the graphene sheets to form fluorographene (CF)n. The fluorine is covalently linked with sp 3 hybridized carbon in fluorographene and the thinnest insulator due to broad band gap of 3 eV. Interestingly, the hydrophobicity of the graphene is enhanced because of . On the other hand, the bigger I prefer to form chargetransfer complex with graphene instead of covalent linkage with graphene. As a result, the sp 2 hybridisation of the carbon remains unchanged. The feasibility in the replacement of carbon atoms in the graphene lattice with oxygen is nil due to its higher electronegative character and the bigger . The well-known oxygen rich graphene derivative is the graphene oxide in which epoxy and hydroxy substituents are at the basal plane while both the carbonyl and the carboxyl substituents are at edges . Upon oxidative exfoliation of graphite by modified Hummer's method, more oxygen enriched functional groups are generated which causes a major change in the hybridization of carbon from sp 2 to sp 3 . The presence of sp 3 hybridized carbon moieties generate the more defects which causes the opening of band gap thereby forming the poor electrically conductive nature of GO. It is highly significant to indicate that the GO is presumed as suitable precursor for the doped graphene as the oxygen bearing substituents are easily subjected to interact with any dopant by both physical and chemical methods .