Aqueous Stabilization and Self‐Assembly of Graphene Sheets into Layered Bio‐Nanocomposites using DNA

Abstract

Atomically thick graphene layers produced from graphite reveal unique electro-thermal, and mechanical properties, [1][2][3][4][5][6][7] and are considered to have a wide range of applications in nanoelectronics, catalysis and biosensing. [1,3,[8][9][10] Graphene monolayers exhibiting exceptional electron/hole carrier mobility have been prepared by mechanical exfoliation of highly ordered pyrolytic graphite, [1,3] by epitaxial growth using chemical vapour deposition of hydrocarbons onto silicon carbide, [11] or via thermal fusion of polycyclic aromatic hydrocarbons.[12] These methods are constrained by low yields and processing limitations, and more practical approaches based on the chemical [6,12,13] or thermal [15,16] reduction of exfoliated sheets of oxidised graphite (graphene oxide, GO) have been developed. High yields of GO monolayers, 0.78 nm in thickness, can be readily prepared by treatment of graphite under strongly acidic and oxidising conditions. [17][18][19] The GO single sheets can be readily dispersed in water and mounted onto substrates using spin-, dip-and spray-coating techniques, and reduced in situ to produce isolated graphene monolayers or transparent 2D films [20][21][22][23][24] with conductivities ranging from as low as 2 S cm À1 , [20] or 23 S cm À1, [15] to a value of 550 S cm À1 for a 10 nm-thick film, [20] comparable with polycrystalline graphite (1250 S cm À1).[25] Alternatively, aqueous dispersions of GO oxide can be chemically reduced directly to produce aggregated sols of graphene sheets that can be assembled into graphene thin films with a typical conductivity of 72 S cm À1. [26] Moreover, by undertaking the reduction step in the presence of poly(sodium 4-styrenesulfonate), [13] or pyrene butyrate, [14] or exploiting electrostatic repulsions between adjacent sheets in an alkaline medium, [26] stable aqueous dispersions of coated graphene monolayers have been produced. Similar approaches have been used to prepare stable graphene dispersions in polar organic solvents by chemical reduction of GO sheets functionalized with hydrophobic residues such as alkylamines, [27] phenyl isocyanate [6] or anhydrous hydrazine. [28] Alternatively, Coleman and coworkers [29] have recently prepared graphene dispersions by ultrasonicating graphite powders in various solvents, for example, N-methylpyrrolidinone, followed by subsequent fractionation using low-speed centrifugation to produce sols comprising single and multilayered graphene sheets. Interestingly, thin films produced from the above dispersions showed conductivity values of $65 S cm À1, comparable to that of chemically reduced graphene oxide paper.Recent studies have demonstrated that hydrophobic carbon nanotubes (CNTs) can be successfully functionalized using single-stranded (ss) DNA to produce novel nanocomposites with potential applications in nanoelectronics and bionanotechnology. [30,31] Adsorption of the biomolecules onto the surface of the CNTs is facilitated by non-covalent p-p stacking interactions involving both purine and pyrimidi...

Functionalized Graphene Nanocomposites

“…For example, adsorption of DNA biomolecules on the surface of graphene is enabled due to non-covalent interactions (electrostatic/hydrogen bonding) between the primary amines of the single-stranded DNA and the carboxylic groups of the GO and by the π-π stacking interactions involving both purine and pyrimide bases of DNA. The results demonstrate that these systems are stable in aqueous solutions for several months at concentrations below 2.5 mg/mL (Patil, Vickery et al 2009). This approach was also developed for chains of double-stranded DNA, yet the results showed that the aqueous suspensions of graphene were less stable, probably due to the pairing of helices limiting interactions with the hydrophilic surface of GO.…”

Graphene materials as 2D non-viral gene transfer vector platforms

“…Isothermal titration calorimetry experiments between graphene and nucleobases revealed that guanine presented the highest interaction energy followed by adenine, cytosine and thymine 17 . Moreover, GO has proven able to load both single-stranded DNA and RNA despite its overall negative charge thanks to hydrophobic and π-π stacking interactions between the ring structures present in NA nucleobases and the GO hexagonal carbon lattice 18,19 . On the other side, the adsorption of double-stranded NA onto GO flakes is thought to be more complex due to its hydrophilic external structure and less availability of NA bases trapped within the double helix structure 20 .…”

Carbon Nanostructures Reduced From Graphite Oxide as Electrode Materials for Supercapacitors

“…К числу химических реактивов, успешно применявшихся для восста-новления ОГ, в первую очередь относятся гидразин и его производные (см., например, работы [30,40,49,[56][57]). При этом гидразин не восстанавливает гидроксильные группы на краях нанолистов.…”