Electron Transport of Zigzag Graphene Nanoribbon Based Biosensor-A Future Perspective towards Biosensor and Biomedical Applications

Research Article

Austin J Nanomed Nanotechnol. 2014;2(1): 1007.

# Electron Transport of Zigzag Graphene Nanoribbon Based Biosensor-A Future Perspective towards Biosensor and Biomedical Applications

K.Janani, C. Preferencial Kala, R.M.Hariharan, S. Sivasathya, and D.John Thiruvadigal*

Department of Physics and Nanotechnology, SRM University, Kattankulathur, Chennai-603 203.

*Corresponding author: : D.John Thiruvadigal, Department of Physics and Nanotechnology

Received: January 02, 2014; Accepted: January 16, 2014; Published: January 23, 2014

## Abstract

Graphene, the profound mother of carbon nanostructures has attracted tremendous attention towards biosensor and biomedical research through its enhanced property of sensitivity and specificity. In the present study, we explore the biological applications of zigzag graphene nanoribbon (ZGNR) as molecularscale biosensors by calculating the electronic properties of zigzag graphene nanoribbon (ZGNR) and paracetamol drug ensemble. Here the drug is adsorbed at the edge of ZGNR through physisorption. The non-covalent interaction between ZGNR and the drug is studied by calculating the transmission spectrum and density of states using non-equilibrium Green's function formalism (NEGF) and density functional theory(DFT).We have simulated different systems like bare ZGNR, hybrid system consisting of ZGNR and paracetamol, hybrid system with central doping of nitrogen, hybrid system with edge doping of nitrogen, hybrid system consisting of nitrogen replacing one complete edge layer carbon atoms and their corresponding I-V characteristics and transmission spectrum are reported. Our results show a significant suppression of transmission spectrum supported by the variation in density of states (DOS) thereby showing a distinct response to the molecule for sensing action. Further, bare ZGNR system is chosen as the reference. The decrease in the I-V characteristics of all the chemically modified systems clearly indicates tuning of band gap thus proving the sensing effect of ZGNR for biomedical applications.

Keywords: Zigzag graphene nanoribbon, Paracetamol drug, Non-Equilibrium Green's function, Density functional theory, Transmission spectrum, I-V characteristic.

## Introduction

Graphene is a rapidly rising star on the horizon of materials science and condensed matter physics.1Graphene is made up of a single layer of carbon atoms packed into a two dimensional honeycomb lattice.[2-5] Since its discovery in 2004, graphene has been extensively studied in many different fields including nanoelectronics, composite materials, energy research, catalysis, and more recently biomedicine.[20] Utilizing the interesting optical, electrical, and chemical properties of graphene, various graphene-based biosensors have been fabricated to detect biomolecules with high sensitivities.[6]Graphene nanoribbons (GNRs) are quasi-one-dimensional structure, which are stripes of graphene. Their structures and their electronic properties have been intensively studied both experimentally and theoretically. The properties of GNR can be tuned by morphology control and chemical doping. While the chemical modification is expected for improved specificity, structural modification of graphene can further improve its sensitivity.[7]To begin with, the development of sensitive and rapid methods for determination of trace amounts of various ions and molecules in human biological samples, serum, plasma and urine were analyzed by fabricating different voltammetric and potentiometric sensors and tested effectively for their sensing efficiency.[22-44]The advent of nanomaterials created the ease to fabricate highly efficient biosensors using fullerene-C[60]-modified edge plane pyrolytic graphite electrode, modified glassy carbon electrode and single-wall carbon nanotubes modified pyrolytic graphite electrode for the detection of biological entity in pharmaceutical formulations and human biological fluids.[45-48]The non-covalent interaction of graphene with biomolecules have been reported for loading of doxorubicin drug in cancer therapy.[8]

Depending on the termination style, normally, GNR can be divided into two kinds: armchair graphene nanoribbon (AGNR) and zigzag graphene nanoribbon (ZGNR).[9]In particular, different quantization rules have been predicted for pure GNR's with zigzag (ZGNR's)[10]and armchair(AGNR's)[11,22] edge shaped. Edge states present in zigzag ribbons provide a single channel for electron conduction which is not the case for the armchair configuration.[2]

Paracetamol is a widely used analgesic (pain reliever) and antipyretic (fever reducer). In combination with opioid analgesics, paracetamol is used in palliative care in advanced cancer patients. [13,18] Paracetamol is not considered carcinogenic at therapeutic doses.[19]

The robust nature of ZGNR makes it an interesting material to be utilized for biosensing and biomedical applications. The purpose of the study is to understand the interaction between a drug (paracetamol) and zigzag graphene nanoribbon in terms of variation in the electrical characteristics which will be helpful while fabricating the biosensor devices.

## Modeling and Methods

In our study, we have simulated different systems like bare ZGNR, hybrid system consisting of ZGNR and paracetamol adsorbed on one of the edges of ZGNR through p-p interaction (physisorption), hybrid system with central doping of nitrogen, hybrid system with edge doping of nitrogen, hybrid system with nitrogen replacing one complete edge layer carbon atoms (Fig1, a-e) and their corresponding I-V characteristics and transmission spectrum are reported.