Electronic transport upon adsorption of biomolecules on graphene

Abstract

Currently, the construction of sensors plays an important role in electronics and bioelectronics, due to the wide range of novel applications for biomedical research, food quality control and environmental monitoring. The sensors for biological application demand materials with special properties, such as: sensitivity, selectivity, biocompatibility, high electronic mobility, low electronic noise and chemical functionality. Due to its unique physical and chemical properties, the graphene has emerged as a suitable candidate for making sensors, since it largest known surface-to-volume ratio; highcharge carrier mobility of up to 200.000 cm2 V−1 s−1 at electron densities of ≈ 2 ×1011 cm−2 , which is significantly higher than that of silicon <1,400 cm2 V−1 s−1 ; mechanical stability and high compatibility with flexible technologies, among others. The electronic properties of graphene are extremely sensitive to the environmental perturbations such as electronic doping and molecular adsorption. Several biomolecules interact with graphene through noncovalent bonds, which typically include the π-π stacking. These interactions can modify the electron density and conductivity in the graphene allowing the detection of the molecules. Theoretical and experimental workspropose nanoelectronic biosensors based on graphene for detecting various biomolecules including DNA, glucose, neurotransmitters, amino acids, proteins and bacteria. In the fabrication of electronic omponents like field-effect transistors (FETs) with the adoption of thin layers of graphene, which consist of two terminals, the source and drain, and a gate that controls the resistance of the device, the highly mobile electrons at or near its surface are extremely sensitive to local charge changes. As a result, the molecules acquire charge when adsorbed, and their binding to a graphene-based gate will disrupt the flow of the electrons. Studying and quantifying the electronic effects due to interaction between substrates and adsorbates can provide tools for the construction of nano graphene-based sensing devices. But,what are the phenomena that underlie the charge transfer between graphene and biomolecules? The different effects generated in the adsorption process of biomolecules and the modification and response of the electrical properties of the graphene, are presented in this review. The chapter was developed in four sections: i) introduction, where the generalities and basic notions of the electronic properties for graphene are presented, together with a brief fundamental of electronic transport based on non-equilibrium Green s functions, and the experimental approaches to current-voltage curves in FET devices; ii) computational modeling of adsorption and devices; iii) experimental realization of devices and; iv) conclusions and final remarks.