Athanasios B. Bourlinos

Functionalization of graphene: covalent and non-covalent approaches, derivatives and applications.

Approaches, Derivatives and Applications Vasilios Georgakilas,† Michal Otyepka,‡ Athanasios B. Bourlinos,‡ Vimlesh Chandra, Namdong Kim, K. Christian Kemp, Pavel Hobza,‡,§,⊥ Radek Zboril,*,‡ and Kwang S. Kim* †Institute of Materials Science, NCSR “Demokritos”, Ag. Paraskevi Attikis, 15310 Athens, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo naḿ. 2, 166 10 Prague 6, Czech Republic

Noncovalent Functionalization of Graphene and Graphene Oxide for Energy Materials, Biosensing, Catalytic, and Biomedical Applications

This Review focuses on noncovalent functionalization of graphene and graphene oxide with various species involving biomolecules, polymers, drugs, metals and metal oxide-based nanoparticles, quantum dots, magnetic nanostructures, other carbon allotropes (fullerenes, nanodiamonds, and carbon nanotubes), and graphene analogues (MoS2, WS2). A brief description of π-π interactions, van der Waals forces, ionic interactions, and hydrogen bonding allowing noncovalent modification of graphene and graphene oxide is first given. The main part of this Review is devoted to tailored functionalization for applications in drug delivery, energy materials, solar cells, water splitting, biosensing, bioimaging, environmental, catalytic, photocatalytic, and biomedical technologies. A significant part of this Review explores the possibilities of graphene/graphene oxide-based 3D superstructures and their use in lithium-ion batteries. This Review ends with a look at challenges and future prospects of noncovalently modified graphene and graphene oxide.

Liquid‐Phase Exfoliation of Graphite Towards Solubilized Graphenes

Following the astonishing discoveries of fullerenes and carbon nanotubes in earlier decades, the rise of graphene has recently triggered an exciting new area in the field of carbon nanoscience with continuously growing academic and technological impetus. Currently, several methods have been proposed to prepare graphenes, such as micromechanical cleavage, thermal annealing of SiC, chemical reduction of graphite oxide, intercalative expansion of graphite, bottom-up growth, chemical vapor deposition, and liquid-phase exfoliation. Especially this latter top-down approach is very appealing from a chemist’s point of view for the following reasons: i) it is direct, simple, and benign producing graphenes just by solvent treatment of graphite powders, and ii) the as-obtained sheets form colloidal dispersions in the solvents used for the exfoliation, thereby enabling their manipulation into various processes, like mixing, blending, casting, impregnation, spin-coating, or functionalization. The key parameter for suitable solvents is that the solvent–graphene interactions must be at least comparable to those existing between the stacked graphenes in graphite. To that end, Coleman and coworkers have successfully demonstrated this concept using N-methylpyrrolidone, N,N-dimethylacetamide, g-butyrolactone, 1,3-dimethyl-2-imidazolidinone, and benzyl benzoate as

Graphene Fluoride: A Stable Stoichiometric Graphene Derivative and its Chemical Conversion to Graphene

Stoichoimetric graphene fluoride monolayers are obtained in a single step by the liquid-phase exfoliation of graphite fluoride with sulfolane. Comparative quantum-mechanical calculations reveal that graphene fluoride is the most thermodynamically stable of five studied hypothetical graphene derivatives; graphane, graphene fluoride, bromide, chloride, and iodide. The graphene fluoride is transformed into graphene via graphene iodide, a spontaneously decomposing intermediate. The calculated bandgaps of graphene halides vary from zero for graphene bromide to 3.1 eV for graphene fluoride. It is possible to design the electronic properties of such two-dimensional crystals.

Multipurpose Organically Modified Carbon Nanotubes: From Functionalization to Nanotube Composites

We show that covalent functionalization of carbon nanotubes (CNTs) via 1,3-dipolar cycloaddition is a powerful method for enhancing the ability to process CNTs and facilitating the preparation of hybrid composites, which is achieved solely by mixing. CNTs were functionalized with phenol groups, providing stable dispersions in a range of polar solvents, including water. Additionally, the functionalized CNTs could easily be combined with polymers and layered aluminosilicate clay minerals to give homogeneous, coherent, transparent CNT thin films and gels.

Gd(III)-doped carbon dots as a dual fluorescent-MRI probe

We describe the synthesis of Gd(III)-doped carbon dots as dual fluorescence-MRI probes for biomedical applications. The derived Gd(III)-doped carbon dots show uniform particle size (3–4 nm) and gadolinium distribution and form stable dispersions in water. More importantly, they exhibit bright fluorescence, strong T1-weighted MRI contrast and low cytotoxicity.

A simple route towards magnetically modified zeolites

A simple route for decorating the external surfaces of zeolites with maghemite nanoparticles is described. The synthesis comprises feeding of a zeolite support with different amounts of iron(III) by employing melt exchange reactions, exposure of the iron-containing solids to vapors of formic acid and finally calcination of the resulting derivatives in air to afford maghemite nanoparticles embedded in the zeolite host. The as-prepared magnetically modified solids, characterized by XRD, Mossbauer and magnetic measurements and SEM and TEM techniques, were found to retain the cation exchange capacity of the parent zeolite as well as its structural integrity.

Thiofluorographene–Hydrophilic Graphene Derivative with Semiconducting and Genosensing Properties

We present the first example of covalent chemistry on fluorographene, enabling the attachment of -SH groups through nucleophilic substitution of fluorine in a polar solvent. The resulting thiographene-like, 2D derivative is hydrophilic with semiconducting properties and bandgap between 1 and 2 eV depending on F/SH ratio. Thiofluorographene is applied in DNA biosensing by electrochemical impedance spectroscopy.

Fullerol ionic fluids

We report for the first time an ionic fluid based on hydroxylated fullerenes (fullerols). The ionic fluid was synthesized by neutralizing the fully protonated fullerol with an amine terminated polyethylene/polypropylene oxide oligomer (Jeffamine). The ionic fluid was compared to a control synthesized by mixing the partially protonated form (sodium form) of the fullerols with the same oligomeric amine in the same ratio as in the ionic fluids (20 wt% fullerol). In the fullerol fluid the ionic bonding significantly perturbs the thermal transitions and melting/crystallization behavior of the amine. In contrast, both the normalized heat of fusion and crystallization of the amine in the control are similar to those of the neat amine consistent with a physical mixture of the fullerols/amine with minimal interactions. In addition to differences in thermal behavior, the fullerol ionic fluid exhibits a complex viscoelastic behavior intermediate between the neat Jeffamine (liquid-like) and the control (solid-like).

Magnetic Fe2O3–Al2O3 composites prepared by a modified wet impregnation method

Fe2O3–Al2O3 composites were prepared by interaction of acetic acid vapors with iron oxides dispersed on the surface of a sol–gel derived porous alumina. Upon pyrolysis the created iron acetate species were transformed to magnetic iron oxide nanoparticles. The atmosphere which is used during the synthetic procedure affects significantly the nature of the nanoparticles which could be either γ-Fe2O3 or magnetite, or non-magnetic such as α-Fe2O3. X-Ray diffraction, surface area measurements and scanning electron microscopy (SEM) were used for the structural characterization and determination of the sorption properties of the composite material properties. The development of magnetic phases decreases the specific surface area of alumina by seeding of the alumina particles and, in parallel, the coverage of their free surface. Mossbauer spectroscopy, magnetic measurements and transmission electron microscopy (TEM) provide evidence for the formation, size and type of magnetic iron oxide phases.