First-principles based density functional theory (DFT) calculations have been carried out on the chemically functionalized pure and Cu, Ag and Au doped zigzag graphene nanoribbon (ZGNR(6,0)) with the use of the branched chain amino acid L-(+)-Leucine named as LLZGNR(6,0), LLCuZGNR(6,0), LLAgZGNR(6,0) and LLAuZGNR(6,0) respectively. The structural stability for minimum total energy was confirmed by perturbating the geometry of the relaxed structures. The physical and chemical properties, such as band gap, chemical potential, transmission spectrum, charge transfer, bonding character and Gibb's free energy of solvation were analysed for all the four systems. It has been observed that the edge doping assisted functionalized systems (LLCuZGNR(6,0), LLAgZGNR(6,0) and LLAuZGNR(6,0)) without the inclusion of spin polarisation are semiconducting in nature. Whereas, barely functionalized system is found to be semi-metallic. An effective space charge polarisation in functionalized graphene nanoribbon has been revealed through charge transfer studies. Hence, it signifies the effective solubility of the nanoribbon in aqueous media. The results indicate the possibility of using such system as nanocarriers in targeted drug delivery applications. (C) 2017 Elsevier B.V. All rights reserved.