High-speed carbon nanotube actuators based on an oxidation/reduction reaction

Actuators with a high-speed response under a high-frequency (more than 100 Hz) applied square-wave voltage of ±2 V have been developed with an electrode composed of millimeter-long single-walled carbon nanotubes synthesized by the "supergrowth method" (SG-SWNTs) and ionic liquids (ILs). Detailed studies concerning induced electric current and transferred charge in the electrode as well as cyclic voltammetric studies of the electrode revealed that the high-speed response originates from the electric current generated by an oxidation/reduction (redox) reaction in addition to electric double-layer charging. The contribution of the redox reactions of SG-SWNTs to the actuation is sensitive to the presence of supporting polymers, the thickness of the electrolyte, and the amplitude of the applied voltage.     

Surfactant‐Dependent Charge Transfer between Polyoxometalates and Single‐Walled Carbon Nanotubes: A Fluorescence Spectroscopic Study

Hybridizations of redox‐active polyoxometalates (POMs) with single‐walled carbon nanotubes (SWNTs) have been widely investigated for their diverse applications. For the purpose of constructing high‐quality electronic devices, controlling charge transfer within POM/SWNT hybrids is an inevitable issue. As determined by means of fluorescence spectroscopy, electron transfer between SWNTs and a common POM dopant, phosphomolybdic acid (PMo₁₂), can be tuned simply by an alteration of nanotube surfactant type from anionic to nonionic. The mechanism is attributed to the influence of surfactant type on the stabilization of the electron donor–acceptor hybrid and effect of surfactant–nanotube interactions. These results will be important to control charge‐transport behavior in nanohybrids consisting of carbon nanotubes.     

Functionalization of Carbon Nanotubes by an Ionic‐Liquid Polymer: Dispersion of Pt and PtRu Nanoparticles on Carbon Nanotubes and Their Electrocatalytic Oxidation of Methanol

Small beginnings : Metal nanoparticle/CNT nanohybrids are synthesized from carbon nanotubes (CNTs) functionalized with an ionic‐liquid polymer. The Pt and PtRu nanoparticles with narrow size distribution (average diameter: (1.3±0.4) nm for PtRu, (1.9±0.5) nm for Pt) are dispersed uniformly on the CNTs (see images) and show good performance in methanol electrooxidation.

     

Ionothermal synthesis of polyoxometalates

An emerging approach: In the ionothermal synthesis of transition-metal-oxide clusters an ionic liquid acts as a solvent, structure-directing agent, and charge-compensating species. The method may open new convenient routes for the synthesis of polyoxometalate-based materials.     

Novel potentiometric sensor for the determination of Cd2+ based on a new nano-composite

A novel ion selective carbon paste electrode for Cd²⁺ ions based on 2,2′-thio-bis[4-methyl(2-amino phenoxy) phenyl ether] (TBMAPPE) as an ionophore was prepared. The carbon paste was made based on a new nano-composite including multi-walled carbon nanotubes (MWCNTs), nanosilica and room-temperature ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆). The constructed nano-composite electrode showed better sensitivity, selectivity, response time, response stability and lifetime in comparison with typical Cd²⁺ carbon paste sensor for the successful determination of Cd²⁺ ions in water and in waste water samples. The best performance for nano-composite sensor was obtained with an electrode composition of 18% TBMAPPE, 20% BMIM-PF₆, 48% graphite powder, 10% MWCNT and 4% nanosilica. The new electrode exhibited a Nernstian response (29.95?±?0.10?mV?decade^?1) toward Cd²⁺ ions in the range of 3.0?×?10^?8 to 1.0?×?10^?1?mol?L^?1 with a detection limit of 7.5?×?10^?9?mol?L^?1. The potentiometric response of prepared sensor was independent of the pH of test solution in the pH range 3.0 to 5.5. It had a quick response with a response time of about 6?s. The proposed electrode showed fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions.     

Application of Static Charge Transfer within an Ionic‐Liquid Force Field and Its Effect on Structure and Dynamics

The effects of linear scaling of the atomic charges of a reference potential on the structure, dynamics, and energetics of the ionic liquid 1,3‐dimethylimidazolium chloride are investigated. Diffusion coefficients that span over four orders of magnitude are observed between the original model and a scaled model in which the ionic charges are ±0.5 e. While the three‐dimensional structure of the liquid is less affected, the partial radial distribution functions change markedly—with the positive result that for ionic charges of ±0.7 e, an excellent agreement is observed with ab initio molecular dynamics data. Cohesive energy densities calculated from these partial‐charge models are also in better agreement with those calculated from the ab initio data. We postulate that ionic‐liquid models in which the ionic charges are assumed to be ±1 e overestimate the intermolecular attractions between ions, which results in overstructuring, slow dynamics, and increased cohesive energy densities. The use of scaled‐charge sets may be of benefit in the simulation of these systems—especially when looking at properties beyond liquid structure—thus providing an alternative to computationally expensive polarisable force fields.     

Hybrid Platforms of Silicon Nanowires and Carbon Nanotubes in an Ionic Liquid Bucky Gel

Silicon nanowires (NWs) are appealing building blocks for low-cost novel concept devices with improved performances. In this research paper, we realized a hybrid platform combining an array of vertically oriented Si NWs with different types of bucky gels, obtained from carbon nanotubes (CNT) dispersed into an ionic liquid (IL) matrix. Three types of CNT bucky gels were obtained from imidazolium-based ionic liquids (BMIM-I, BIMI-BF₄, and BMIM-Tf₂N) and semiconductive CNTs, whose structural and optical responses to the hybrid platforms were analyzed and compared. We investigated the electrical response of the IL-CNT/NW hybrid junctions in dark and under illumination for each platform and its correlation to the ionic liquid characteristics and charge mobility. The reported results confirm the attractiveness of such IL-CNT/NW hybrid platforms as novel light-responsive materials for photovoltaic applications. In particular, our best performing cell reported a short-circuit current density of 5.6 mA/cm² and an open-circuit voltage of 0.53 V.     

A new potentiometric sensor based on a high-performance composite for nanomolar determination of mercury (II) in environmental samples

A new potentiometric sensor for the rapid determination of Hg²⁺ based on modified carbon paste electrode consisting of room temperature ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆), multi-walled carbon nanotubes (MWCNTs), alumina nanoparticles and a synthetic macrocyclic diamide ‘7,10,13-triaza-1-thia-4,16-dioxa-6,14-dioxo-2,3;17,18-dinaphtho-cyclooctadecane’ as an efficient ionophore was constructed. Prepared composite is an ideal paste because it has low drift of potential, high selectivity and fast response time (10 s), which leads to a more stable potential signal. The morphology and properties of electrodes surface were characterised by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy. A linear dynamic range of 2.01–2.01 × 10⁷ µg L^?1 with detection limit of 1.40 µg L^?1 Hg²⁺ was obtained at pH range of 2.5 to 4.5. The prepared modified electrode shows several advantages such as simple preparation method, high stability of the composite paste, high sensitivity, long-term life time (at least 13 weeks) and remarkable potentiometric reproducibility. The modified electrode was successfully applied for the accurate determination of trace amounts of Hg ²⁺ in environmental samples.     

Ionic gelators: oligomeric and polymeric electrolytes as novel gel forming materials

In this article, novel gel‐forming materials based on oligomeric and polymeric electrolytes for not only water but also organic solvents, including ionic liquids, are highlighted especially the synthesis, derivatization, and physical property. The oligoelectrolytes with cationic pyridinium backbone can be very easily prepared by the intermolecular quaternization of the ampholytic monomer. The ionene polymers with N,N′‐(p‐phenylene)dibenzamide linkages as polyelectrolyte were also straightforwardly synthesized in high yields by the copolymerization of 1,4‐bis[4‐(chloromethyl)benzamide]benzene and commercially available α,ω‐ditertiary amines. The oligo‐ and polyelectrolytes provided physical hydrogels under ca. 1–5 wt% of the concentrations after heating and cooling at room temperature without any other additives. These cationic gelators have characteristic properties, such as acid resistance, a self‐healing nature after mechanical collapse, and a dispersant ability for single‐walled carbon nanotubes, which have been rarely attainable for conventional physical gelators. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 10: 230–242; 2010: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.201000007     

硫脲类阴离子受体的设计合成与阴离子识别

硫脲类化合物具有生物活性,是优良的氢键供体,与阴离子特别是含氧阴离子形成氢键配合物。本文设计合成了系列二苯基硫脲衍生物,通过取代基效应调控硫脲衍生物分子内电转移过程,阴离子与硫脲基团结合后,增强了分子内供体的给电子能力,进一步促进电荷转移过程,据此识别不同的阴离子。由于主体分子与阴离子间形成氢键的能力及阴离子碱性的差异,可达到选择性结合的目的。     

Functionalization of Carbon Nanotubes with Water‐Insoluble Porphyrin in Ionic Liquid: Direct Electrochemistry and Highly Sensitive Amperometric Biosensing for Trichloroacetic Acid

A functional composite of single‐walled carbon nanotubes (SWNTs) with hematin, a water‐insoluble porphyrin, was first prepared in 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM][PF₆]) ionic liquid. The novel composite in ionic liquid was characterized by scanning electron microscopy, ultraviolet absorption spectroscopy, and electrochemical impedance spectroscopy, and showed a pair of direct redox peaks of the Fe^III/Fe^II couple. The composite–[BMIM][PF₆]‐modified glassy carbon electrode showed excellent electrocatalytic activity toward the reduction of trichloroacetic acid (TCA) in neutral media due to the synergic effect among SWNTs, [BMIM][PF₆], and porphyrin, which led to a highly sensitive and stable amperometric biosensor for TCA with a linear range from 9.0×10^?7 to 1.4×10^?4 M . The detection limit was 3.8×10^?7 M at a signal‐to‐noise ratio of 3. The TCA biosensor had good analytical performance, such as rapid response, good reproducibility, and acceptable accuracy, and could be successfully used for the detection of residual TCA in polluted water. The functional composite in ionic liquid provides a facile way to not only obtain the direct electrochemistry of water‐insoluble porphyrin, but also construct novel biosensors for monitoring analytes in real environmental samples.     

Novel diethanolamine based deep eutectic mixtures for carbon dioxide (CO2) capture: synthesis and characterisation

In this work, diethanolamine was successfully used as a hydrogen bond donor to prepare three different deep eutectic solvents (DESs) using three quaternary ammonium salts at different molar ratios. Important physical properties of the prepared DESs including melting point, glass transition, crystallisation temperature, density, refractive index and viscosity were measured in temperature ranging from (298.15 to 358.15 K). Moreover, in order to explore the changes in chemical structures of the DESs, FTIR analysis was performed. The developed DESs have melting points lower than 293.15 K, and of significantly low density (close to water) and comparable viscosity. The effect of temperature and molar ratio on physical properties were also discussed. Empirical models were used to correlate the density, refractive index and viscosity data of the DESs as a function of temperature and molar ratio. A quantitative analysis, also called as ANOVA analysis, was conducted to investigate the significance of the experimental physical properties data. The new DESs prepared in this work have a potential to be used in numerous applications including CO₂ capture.     

Modified SWCNTs with Amphoteric Redox and Solubilizing Properties

A complementary double‐covalent functionalization of single‐wall carbon nanotubes (SWCNTs) that involves both solubilizing ionic liquids and electroactive moieties is reported. Our strategy is a simple and efficient methodology based on the stepwise functionalization of the nanotube surface with two different organic moieties. In a first instance, oxidized SWCNTs are amidated with ionic liquid precursors, and further treated with n‐butyl bromide to afford SWCNTs functionalized with 1‐butylimidazolium bromide. This approach allows tuneable polarity induced by anion exchange, which has an effect on the relative solubility of the modified SWCNTs in water. Subsequently, a 1,3‐dipolar cycloaddition reaction was performed to introduce the electron‐acceptor 11,11,12,12‐tetracyano‐9,10‐anthra‐para‐quinodimethane (TCAQ) unit on the SWCNTs. Furthermore, to evaluate the influence of the functional group position, the TCAQ electroactive molecule was anchored through an esterification reaction onto previously oxidized SWCNTs, followed by the Tour reaction to introduce the ionic liquid functions. IR and Raman spectroscopies, thermogravimetric analysis (TGA), UV/Vis/NIR spectroscopy, transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS) were employed and clearly confirmed the double‐covalent functionalization of the SWCNTs.     

Size-controllable gold-platinum alloy nanoparticles on nine functionalized ionic-liquid surfaces and their application as electrocatalysts for hydrogen peroxide reduction

A series of room-temperature ionic liquids (RTILs) containing different functional groups such as hydroxyl, nitrile, carboxyl, and thiol attached to imidazolium cations, combined with various anions such as chloride [Cl], tetrafluoroborate [BF(4)], hexafluorophosphate [PF(6)], and bis[(trifluoromethyl)sulfonyl]imide [Tf(2)N], have been successfully synthesized. Dissolved in chitosan (Chi), the Chi/RTIL composites can be employed as flexible templates for the preparation of Au/Pt nanostructures. These Au/Pt nanostructures can be facilely deposited in situ on the surface of Chi/RTILs through electrodeposition. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results demonstrate that the alloy size is significantly dependent on the structure of the Chi/RTILs, with sizes ranging from 2.8 to 84.7 nm. Based upon the functionalized RTILs, nine Chi/RTIL-Au/Pt biosensors have been fabricated. First, the size-dependent electrochemistry of Chi/RTIL-Au/Pt was investigated using potassium ferricyanide as the probe. The reversible electron transfer of the Fe(CN)(6)(3-/4-) redox couple was realized for the nine biosensors, and the peak currents, as well as the peak-to-peak separations (ΔE(p)) and electron-transfer rates, differ greatly from each other because of the diversity of the RTILs. Further electrochemical research reveals that the functional groups of these RTILs exert an evident influence on the reduction behavior of H(2)O(2), which in turn illustrates that the electrocatalytic activity of Chi/RTIL-Au/Pt nanocomposites can be tuned by means of employing RTILs with different functional groups, and an appropriate combination of cations and anions may produce a higher activity. The facilitated electron transfer and the intrinsic catalytic activity of Au/Pt NPs provide a facile way to construct a third-generation H(2)O(2) biosensor with a high sensitivity, low detection limit, quick response time, and excellent selectivity.     

Charge‐Scaling Effect in Ionic Liquids from the Charge‐Density Analysis of N,N′‐Dimethylimidazolium Methylsulfate

The charge scaling effect in ionic liquids was explored on the basis of experimental and theoretical charge‐density analyses of [C₁MIM][C₁SO₄] employing the quantum theory of atoms in molecules (QTAIM) approach. Integrated QTAIM charges of the experimental (calculated) charge density of the cation and anion resulted in non‐integer values of ±0.90 (±0.87) e. Efficient charge transfer along the bond paths of the hydrogen bonds between the imidazolium ring and the anion was considered as the origin of these reduced charges. In addition, a detailed QTAIM analysis of the bonding situation in the [C₁SO₄]^? anion revealed the presence of negative π_O→σ*_S‐O hyperconjugation.     

百草枯在碳纳米管与离子液体复合修饰电极上的电化学行为及测定

制备了碳纳米管(MWCNTs)和疏水性离子液体1-丁基-3-甲基咪唑六氟磷酸盐(BMIMPF6)复合修饰电极(MWCNTs-BMIMPF6/GCE),并采用红外光谱(IR)分别对MWCNTs、BMIMPF6及MWCNTs-BMIMPF6进行了表征。运用循环伏安法研究了百草枯(PQ)在该修饰电极上的电化学行为。结果表明,在pH7.0的PBS缓冲溶液中,PQ在MWCNTs-BMIMPF6/GCE上出现2对明显的氧化还原峰,在20~200 mV/s扫描速率范围内,其氧化还原峰电流均与扫描速率平方根(v1/2)呈线性关系,表明该电极过程受扩散控制。计算了电极过程的部分动力学参数:电极有效面积A=0.156 4 cm2,百草枯在pH7.0的PBS缓冲液中的扩散系数D=7.0×10-5cm2/s。优化了方波溶出伏安法(SWSV)的实验参数,发现峰电流Ipa1与PQ浓度在7.729×10-7~9.660×10-5mol/L范围内呈线性关系,检出限为1.576×10-7mol/L。采用该方法对实际水样进行检测,增敏回收率为93%~104%。     

Insight into the Origin of the Positive Effects of Imidazolium Salt on Electrocatalytic Activity: Ionic Carbon Nanotubes as Metal‐Free Electrocatalysts for Oxygen Reduction Reaction

We report remarkable metal‐free electrocatalytic activities of the imidazolium salt‐functionalized ionic multi‐walled carbon nanotubes (IM‐f‐MWCNTs) in the oxygen reduction reaction (ORR). The electrocatalytic activity can be attributed to the induced polarization of the π‐electrons of CNTs, thus accelerating interfacial electron transfer. The zwitterionic MWCNTs functionalized with poly(vinylimidazolium sulfonate) have a more positive surface charge and exhibit a better electrocatalytic activity than the poly(vinylbutylimidazolium chloride)‐functionalized MWCNTs. The IM‐f‐MWCNTs showed better fuel selectivity than the commercial Pt/C electrocatalyst.