Fluorinated graphenes as advanced biosensors - effect of fluorine coverage on electron transfer properties and adsorption of biomolecules

Graphene derivatives are promising materials for the electrochemical sensing of diverse biomolecules and development of new biosensors owing to their improved electron transfer kinetics compared to pristine graphene. Here, we report complex electrochemical behavior and electrocatalytic performance of variously fluorinated graphene derivatives prepared by reaction of graphene with a nitrogen-fluorine mixture at 2 bars pressure. The fluorine content was simply controlled by varying the reaction time and temperature. The studies revealed that electron transfer kinetics and electrocatalytic activity of CFx strongly depend on the degree of fluorination. The versatility of fluorinated graphene as a biosensor platform was demonstrated by cyclic voltammetry for different biomolecules essential in physiological processes, i.e. NADH, ascorbic acid and dopamine. Importantly, the highest electrochemical performance, even higher than pristine graphene, was obtained for fluorinated graphene with the lowest fluorine content (CF0.084) due to its high conductivity and enhanced adsorption properties combining π-π stacking interaction with graphene regions with hydrogen-bonding interaction with fluorine atoms.

Electrochemical Fluorographane: Hybrid Electrocatalysis of Biomarkers, Hydrogen Evolution, and Oxygen Reduction

Fluorographane (C1 Hx F1-x+δ )n is a new member of the graphene family that exhibits hydrophobicity and a large band gap that is tunable based on the level of fluorination. Herein, sensing and energy applications of fluorographane are reported. The results reveal that the carbon-to-fluoride ratio of fluorographane has a great impact on the electrochemical performance of the materials. Lowered oxidation potentials for ascorbic and uric acids, in addition to a catalytic effect for hydroquinone and dopamine redox processes, are obtained with a high fluoride content. Moreover, fluorographane, together with residual copper- and nickel-based doping, acted as a hybrid electrocatalyst to promote hydrogen evolution and oxygen reduction reactions with considerably lower onset potentials than those of graphane (starting material), which makes this a promising material for a broad range of applications.

Tuning of fluorine content in graphene: towards large-scale production of stoichiometric fluorographene

The availability of well-defined modified graphene derivatives such as fluorographene, graphane, thiographene or hydroxygraphene is of pivotal importance for tuning the resulting material properties in numerous potential applications. A series of fluorinated graphene with various contents of fluorine was synthesized by a simple fluorination procedure in an autoclave with a nitrogen/fluorine atmosphere at different exposure times and temperatures. To investigate the composition, structure and properties all samples were characterized in detail by a number of analytical techniques such as SEM, XRD, EDS, AFM, STEM, combustible elemental analysis, STA, XPS, Raman spectroscopy, UV-VIS spectroscopy and cyclic voltammetry. The fully fluorinated graphene with the overall stoichiometry C1F1.05 had a bright white color indicating a significant change of band-gap. In comparison to other samples such a high concentration of fluorine led to the occurrence of exotic thermal behavior, strong luminescence in the visible spectral region and also the unique super-hydrophobic behavior observed on the material surface. The described tunable fluorination should pave the way to fluorographene based devices with tailored properties.

Cytotoxicity of fluorographene

Fluorinated graphenes (F-G) might inevitably be released into the environment through disposal and wearing of future commercial products incorporated with F-G. Therefore, we determined their cytotoxicity in this study.

Fluorographane (C1HxF1−x−δ)n: synthesis and properties

Fluorographane (C₁H_xF_1−x−δ)_n was obtained from graphene by hydrogenation via the Birch reaction with consequent fluorination of the resulting graphane.

Alpha (α-) and beta (β-carboranyl-C-deoxyribosides: syntheses, structures and biological evaluation

The syntheses of the unprotected neutral closo-carboranyl-C-deoxyriboses, starting from anomeric mixture of 1-ethynyldeoxyriboses, and their corresponding open-cage nido-derivatives have been described. The structures of both the α- and β-anomers were confirmed by single-crystal X-ray diffraction. While limited water solubility of the neutral closo-anomers led to high cytotoxicity, their cesium salts (nido-species) exhibited higher water solubility leading to lower cytotoxicity. However, in vitro boron neutron capture therapy (BNCT) investigation using the murine squamous cell carcinoma (SCCVII) cell lines showed that there are no significant differences between the survival fractions of the two species.

Cross-metathesis of allylcarboranes with O-allylcyclodextrins

Cross-metathesis between allylcarboranes and O-allylcyclodextrins was catalyzed by Hoveyda–Grubbs 2^nd generation catalyst in toluene. The corresponding carboranyl-cyclodextrin conjugates were isolated in 15–25% yields.

Improved synthesis of [closo-1-CB9H10]– anion and new C-substituted derivatives

The Brellochs method was utilized to gain access to the [closo-1-CB9H10]– anion (1). Previous work describing the details of the synthesis of 1 via the [closo-2-CB9H10]– anion (2) was brief and insufficient. Therefore, we report an optimized procedure for the synthesis of 1, the preparation of the unknown C-halogenated series using N-halosuccinimides and bis(benzenesulfonyl)fluoroamine, and the unknown C-methylated product using CH3I. NMR properties and regularities within the series were also investigated.

C-Halogenation of the closo-[CB11H12]- Anion

A synthesis is described of the four C-halogenated 1-X-CB11H11- anions (X = I, Br, Cl, F) using N-halosuccinimides and N-fluorobis(benzenesulfonyl)amine as halogenating agents. The procedure yields only the desired product next to unreacted starting material. Regularities in the 11B and 13C NMR chemical shifts of singly halogenated icosahedral carboranes are summarized.

NMR Assignments of [6-R-nido-5,6-C2B8H10]- Anions (where R = H, Me, and n-C6H13). An Irreversible 5 → 6 Alkyl Migration via a B9 Vertex-Swing Mechanism

Deprotonation by "proton sponge" (PS = 1,8-dimethylaminonaphthalene) of the parent dicarbaborane nido-5,6-C2B8H12 (1) and its 6-R-substituted derivatives (where R = Me and n-C6H13) leads to the anions [nido-5,6-C2B8H11]- [1]- and [6-R-nido-5,6-C2B8H10]- [6-R-1]-, respectively. In contrast, the deprotonation of the 5-substituted isomers, 5-R-nido-5,6-C2B8H11 (5-R-1), results in irreversible conversion into the 6-substituted anions [6-R-1]-, from which the neutral compounds 6-R-1 can be obtained via reprotonation. This 5 → 6 alkyl migration can be explained by the B9 vertex-swing mechanism previously proposed for the interenantiomeric fluxionality of [1]-, but now with the product dictated by the higher thermodynamic stabilities of the 6-substituted derivatives. The work has also resulted in complete assignments of 11B and 1H NMR spectra of the [nido-5,6-C2B8H11]- anion and of 11B NMR spectra of the [6-R-nido-5,6-C2B8H10]- anions.

Relative Reactivities of 1,1,1-Trichloroethane and 1,1,1-Trichlorotrifluoroethane in Competitive Addition Reactions

Relative reactivity of CH3CCl3 and CF3CCl3 measured in competitive addition reactions with 1-hexene in the presence of free radical initiators or Cu, Pd and Ru complexes was found to depend on the type of catalyst. The unusual course of the reaction has been found in the additions catalyzed with copper(I)-amine complexes where CH3CCl3 in competition with CF3CCl3 was completely unreactive. The results have been explained in terms of the change of reaction mechanism and compared with classical free radical initiation.

Arachno-6,9-C2B8H14 dicarbaborane and its 1- and 5-monohalogenated derivatives

Reduction of nido-5,6-C2B8H12 with sodium tetrahydroborate in ethanolic sodium hydroxide as a new method for preparing arachno-6,9-C2B8H14 is reported. Electrophilic halogenation of 6,9-C2B8H14 occurs at the B(1) site to give a series of 1-X-6,9-C2B8H13 (X = Cl, Br, and I) derivatives. Stereoselective addition of hydrogen halides to the B(5)-C(6) bond in the [6,9-C2B8H10]2- anion results in the formation of 5-X-6,9-C2B8H13 (X = F, Cl, Br, I and 5'-0-6,9-C2B8H13) compounds. Constitution of all compounds isolated is suggested on the basis of their 1H and 11B NMR data and the effects of halogen substituents on the 11B NMR shielding of individual cage boron atoms are discussed in terms of Δδ and k2 values.

Synthesis and structure of μ-6,9-metalla-bis(ligand)-6,9-dicarba-nido-decarboranes(10) from the [6,9-C2B8H10]2- anion

A revised structure for the [6,9-C2B8H10]2- anion is siggested on the basis of its NMR spectra. The anion reacts with the [cis-PtL2CL2] (L = P(C6H5)3, S(C2H5)2) and [Ni(cis-1,2-DACH)..Cl2] (DACH = diaminocyclohexane) complexes to produce a family of suare-planar [μ-6,9-ML2-6,9-C2B8H10] (M = Pt, Ni) nido-metalladicarbaboranes containing an unusual metallic bridge linking both skeletal carbon atoms of the carborane ligand. The structure of the complexes is proposed on the basis of their NMR spectra and an X-ray diffraction study.

Synthesis and structure of iso-C4B18H22

Iso-C4B18H22 isolated earlier as a minor by-product in the H2CrO4 oxidation of the C2B9H12(-) anion was prepared in 10% yield by thermolysis of 7,8-C2B9H13. The originally suggested structure, 3-(8'-nido-5,6-C2B8H11)-1,2-C2B10H11, is confirmed by the 11B NMR spectra.

Synthesis and characteristics of sulfur interligand bridge-derivatives and of some S-substituted compounds in the (C2B9H11)2Co- series. Conformations of (C2B9H11)2Mx- metallocarboranes

Synthesis, properties and chemical behaviour of the (C2B9H11)2Co- derivatives, namely anions with -S- or -SS- bridges and of neutral species with -SR- (R = H, alkyl, aryl) or -S-SR- bridges as well as with -(+)S(CH3)2 group are described. The analysis of 11B NMR spectra indicates in solution and in the 11B NMR time scale a free rotation at (C2B9H11)2Co-, oscillations at -S2-, -S=CH=S- and rigid conformations at -S- or -(+)SR-, (CH3)2S(+)- and -S-SR(+)- derivatives. For description of different conformations a combination of locants and descriptors e (eclipsed), s (staggered) is proposed. The (s-1,4',2,1') conformation was found by X-ray study of (8-CH3OC2B9H10)2Ni.

Synthesis and properties of some icosahedral carborane B,B'-dithiols

Reaction of icosahedral carboranes with excess sulfur over AlCl3 converts in high yields o-carborane to 9,12-, and m-carborane to 9,10- and 5(4),9-dithiols which were transformed by CH2Br2 to the appropriate cyclic thioformal derivatives. Reaction of 9,12(HS)2-1,2-C2B10H10 with acetone and AlCl3 afforded a cyclic thioketal, the structure of which was confirmed by X-ray structure analysis. All structures were proposed on the ground of 1H-, 11B-NMR and mass spectra.