Jean-Christophe P. Gabriel

Interaction of Aromatic Compounds with Carbon Nanotubes: Correlation to the Hammett Parameter of the Substituent and Measured Carbon Nanotube FET Response

We have used field-effect transistor (FET) devices with semiconducting single-walled carbon nanotubes (SWNTs) as the conducting channels to study interactions of aromatic compounds with SWNTs. Electronic detection occurs through charge-transfer effects, monitored as the change of the gate voltage (Vg) dependence of the source-drain current Isd. For monosubstituted benzene compounds, we find that the shift of the Isd − Vg characteristic is proportional to the Hammett sigma values (σp) of their substituents.

Swollen liquid-crystalline lamellar phase based on extended solid-like sheets

Ordering particles at the nanometre length scale is a challenging and active research area in materials science. Several approaches have so far been developed, ranging from the manipulation of individual particles to the exploitation of self-assembly in colloids. Nanometre-scale ordering is well known to appear spontaneously when anisotropic organic moieties form liquid-crystalline phases; this behaviour is also observed for anisotropic mineral nanoparticles resulting in the formation of nematic, smectic and hexagonal mesophases. Here we describe a lyotropic liquid-crystalline lamellar phase comprising an aqueous dispersion of planar solid-like sheets in which all the atoms involved in a layer are covalently bonded. The spacing of these phosphatoantimonate single layers can be increased 100-fold, resulting in one-dimensional structures whose periodicity can be tuned from 1.5 to 225 nanometres. These highly organized materials can be mechanically or magnetically aligned over large pH and temperature ranges, and this property can be used to measure residual dipolar couplings for the structure determination of biomolecules by liquid-state NMR. We also expect that our approach will result in the discovery of other classes of mineral lyotropic lamellar phases.

Short-channel effects in contact-passivated nanotube chemical sensors

We report a design for carbon nanotube field-effect transistors which tests the nanotube depletion length. In this design, the metal contacts and adjacent nanotubes were coated with impermeable silicon oxide, while the central region of nanotubes was exposed. We tested the devices by measuring sensitivity to NH3 and poly(ethylene imine). NH3 caused similar responses in passivated devices and in normal, nonpassivated devices. Thus, the device design passivates the metal-nanotube contacts while preserving chemical sensor characteristics. Poly(ethylene imine) produced negative threshold shifts of tens of volts, despite being in contact with only the center region of devices. Based on the observed device characteristics, we conclude that the length scale of the covered nanotubes in our structure is comparable to the decay length of the depletion charge in nanotube transistors.

Quasi-Langmuir–Blodgett thin film deposition of carbon nanotubes

The handling and manipulation of carbon nanotubes continues to be a challenge to those interested in the application potential of these promising materials. To this end, we have developed a method to deposit pure nonoriented nanotube films over large flat areas on substrates of arbitrary composition. The method bears some resemblance to the Langmuir–Blodgett deposition method used to lay down thin organic layers. We show that this redeposition technique causes no major changes in the films’ microstructure and that they retain the electronic properties of as-deposited films laid down on an alumina membrane.

Mineral Liquid Crystals from Self-Assembly of Anisotropic Nanosystems

In this article we review the mesogenic properties of the mineral liquid crystals (MLCs) based on molecular nanowires: Li2Mo6Se6; nanotubes: Imogolite and NaNb2PS10; molecular ribbons: V2O5; exfoliated single sheets: smectic clays and H3Sb3P2O14; nanorods: Boehmite (γ-AlOOH), Akaganeite (β-FeOOH ), Goethite (α-FeOOH); platelets: Gibbsite (Al(OH)3); disks: Ni(OH)2; bio-mineral hybrids. We then propose numerous phases that could lead to the discovery of new MLCs. We finally review how the properties of these mesophases and their collective behavior have been used for making mesoporous composites with anisotropic properties, for making nanodevices and solar cells, as well as how they could be used to allow the measurement of residual dipolar couplings in NMR studies of biomolecules.

Mineral liquid crystalline polymers

Abstract This paper presents a survey of the literature on the liquid crystalline properties of dispersions of mineral moieties in solvents. The description of various systems, namely vanadium pentoxide, boehmite, imogolite, β FeOOH, LiMo 3 Se 3 and montmorillonite clay suspensions, show that the mesomorphism of these mineral polymers can be understood by using the same concepts which apply to suspensions of organic moieties. The respective roles of the particle anisotropy and electrical charge are specifically discussed in order to define the molecular features required by mineral moieties to form mesomorphic suspensions.

Complex Fluids Based on the Flexible One‐Dimensional Mineral Polymers [K(MPS4)]∞ (M=Ni, Pd): Autofragmentation to Concave, Cyclic (PPh4)3[(NiPS4)3]

A remarkable autofragmentation/rearrangement sequence results in the unprecedented formation of inorganic concave cyclic anion [(NiPS4 )3 ]3- (structure shown on the right) upon dissolving the potassium salt of the charged mineral polymer 1∞ [NiPS4 ]- in DMF; the initial complex fluid has a transient anisotropic texture that can be identified by optical microscopy under polarized light. In contrast, the complex fluid that results upon dissolving 1∞ [PdPS4 ]- is stable up to 323 K as persistent, flexible, charged chains.

First Use of a Mineral Liquid Crystal for Measurement of Residual Dipolar Couplings of a Nonlabeled Biomolecule

Superimposing the two 13 C,1 H correlation maps of an unlabeled pentasaccharide acquired in D2 O (upper doublet) and in a magnetically aligned mineral liquid crystal, a colloidal suspension of V2 O5 (lower doublet), reveals that, in the second case, D components appear in addition to the usual splittings J. This is a result of the partial alignment of the biomolecule, and provides long-range structural NMR data.

Synthesis and structure of a three-dimensional open-framework aluminophosphate [NH2(CH2)3NH3]+[HAl3P3O14]–·H2O, containing AlO5 and AlO6 polyhedra

The novel, open-framework aluminophosphate, [NH2(CH2)3NH3]+[HAl3P3O14]–·H2O, designated SBM-6, contains five- and six-coordinate aluminum but, unlike other AlPOs, no AlO4 tetrahedra.

Liquid–crystalline properties of aqueous suspensions of natural clay nanosheets

Clay minerals, like beidellite or nontronite, spontaneously exfoliate in water and form colloidal suspensions of nanosheets. In a given range of concentration, these suspensions display a nematic liquid–crystalline phase whose structure and properties can be conveniently studied in detail by polarized-light microscopy and small-angle X-ray scattering (SAXS). Moreover, in situ SAXS investigations of sheared clay suspensions provide information about their flow properties, both in the isotropic and nematic phases. The colloidal nematic phase shows the classical properties of usual nematics, such as surface anchoring and electric-field and magnetic-field alignment. Thus, nematic single domains can be produced. The isotropic phase also displays strong electro-optic effects in moderate electric fields. Finally, we describe a few examples of applications of such systems and we show how these studies could be extended to suspensions of other types of nanosheets.