Why single-walled carbon nanotubes can be dispersed in imidazolium-based ionic liquids

Preparation of graphene/carbon nanotube-cellulose composites assisted by ionic liquids: A review

As is well known, cellulose, as a natural polymer material with abundant reserves, plays an irreplaceable role as the major raw material in energy and chemical-related fields. With the continuous advancement of technology, native single-component cellulose is often unsatisfactory for practical applications, constructing composites is an effective means of expanding the applications. When compounded with other ingredients to prepare composites, cellulose usually needs to be dissolved and regenerated to obtain good dispersion. Current studies have revealed that cellulose is insoluble in conventional solvents, and the limited types of solvent systems that can dissolve cellulose tend to degrade the cellulose during the dissolution process, altering the cellulose properties. Ionic liquids (ILs) are a class of solvents that are capable of dissolving cellulose without adversely affecting the cellulose during the dissolution process, such as degradation. Graphene and carbon nanotubes (CNTs) are poorly dispersed and easily agglomerated by π-π stacking in general solvents, whereas ILs can effectively shield them from π-π stacking, resulting in a favorable and steady dispersion. Thus, the cellulose composites of graphene/CNTs can be prepared with the assistance of ILs. In this paper, the solubilization of cellulose by ILs and the solubilization mechanism to the preparation of cellulose composites with graphene/CNTs are reviewed, the interactions between graphene, CNTs and cellulose in the composites are elucidated, and the preparation of cellulose composites with graphene/CNTs is introduced in terms of their structure, properties and application potential.

How Domain Segregation in Ionic Liquids Stabilizes Nanoparticles and Establishes Long-Range Ordering─A Computational Study

Due to their physical properties including high thermal stability, very low vapor pressure, and high microwave absorption, ionic liquids have attracted great attention as solvents for the synthesis of nanomaterials, being considered as greener alternatives to traditional solvents. While usual solvents often need additives like surfactants, polymers, or other ligands to avoid nanoparticle coalescence, some ionic liquids can stabilize nanoparticles in dispersion without any additive. In order to quantify how the ionic liquids can affect both the aggregation thermodynamics and kinetics, molecular dynamics simulations were performed to simulate the evolution of concentrated dispersions and to compute the potential of mean force between nanoparticles of both hydrophilic and hydrophobic natures in two imidazolium-based ionic liquids, which differ from each other by the length of the cation alkyl group. Depending on the nature of the nanoparticle, structured layers of the polar and apolar regions of the ionic liquid can be formed close to its surface, and those layers lead to activation barriers for dispersed particles to get in contact. If the alkyl group of the ionic liquid is long enough to lead to domain segregation between the ionic and apolar portions of the solvent, the layered structure around the particle becomes more structured and propagates several nanometers away from its surface. This leads to stronger barriers close to the contact and also multiple barriers at larger distances that result from the unfavorable superposition of solvent layers of opposing nature when the nanoparticles approach each other. Those long-range solvent-mediated forces not only provide kinetic stability to dispersions but also affect their dynamics and lead to a long-range ordering between dispersed particles that can be explored as a template for the synthesis of complex materials.

Synergistic Interaction of Ionic Liquid Grafted Poly(vinylidene Fluoride) and Carbon Nanotubes to Construct Water Treatment Membranes with Multiple Separation Properties

In this study, the dual strategy of 1-butyl-3-vinylimidazolium bromide ionic liquid (IL) grafting and carbon nanotubes (CNTs) nanocomposition was applied to modify poly(vinylidene fluoride) (PVDF)-based membranes. The highly hydrophilic/oleophobic and fouling-resistant PVDF-g-IL/CNTs membranes with excellent separation efficiency were obtained by the nonsolvent-induced phase separation method with ethanol-water mixed solution as the coagulation bath. The grafted IL not only generated hydrophilic groups on PVDF chains but also acted together with the CNTs to induce the formation of hydrophilic β-crystalline phase of PVDF, which significantly improved the hydrophilicity and pore structure of the modified PVDF membranes. As a result, the pure water flux of the optimal membrane increased up to 294.2 L m-2 h-1, which was 5.2 times greater than that of the pure PVDF membrane. Simultaneously, the electrostatic interaction of the positive IL and the integration of CNTs enhanced adsorption sites of the membranes, producing exceptional retention and adsorption of dye wastewater and oil-water emulsion. This study presents a straightforward and efficient approach for fabricating PVDF separation membranes, which have potential applications in the purification of various polluted wastewater.

Highly sensitive detection of multiple antiviral drugs using graphitized hydroxylated multi-walled carbon nanotubes/ionic liquids-based electrochemical sensors

Global outbreaks and the spread of viral diseases in the recent years have led to a rapid increase in the usage of antiviral drugs (ATVs), the residues and metabolites of which are discharged into the natural environment, posing a serious threat to human health. There is an urgent need to develop sensitive and rapid detection tools for multiple ATVs. In this study, we developed a highly sensitive electrochemical sensor comprising a glassy carbon electrode (GCE) modified with graphitized hydroxylated multi-walled carbon nanotubes (G-MWCNT-OH) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6, IL) for the detection of six ATVs including famciclovir (FCV), remdesivir (REM), favipiravir (FAV), hydroxychloroquine sulfate (HCQ), cepharanthine (CEP) and molnupiravir (MOL). The morphology and structure of the G-MWCNT-OH/IL nanocomposites were characterized comprehensively, and the electroactive surface area and electron conductivity of G-MWCNT-OH/IL/GCE were determined using cyclic voltammetry and electrochemical impedance spectroscopy. The thermodynamic stability and non-covalent interactions between the G-MWCNT-OH and IL were evaluated through quantum chemical simulation calculations, and the mechanism of ATV detection using the G-MWCNT-OH/IL/GCE was thoroughly examined. The detection conditions were optimized to improve the sensitivity and stability of electrochemical sensors. Under the optimal experimental conditions, the G-MWCNT-OH/IL/GCE exhibited excellent electrocatalytic performance and detected the ATVs over a wide concentration range (0.01-120 μM). The limit of detections (LODs) were 42.3 nM, 55.4 nM, 21.9 nM, 15.6 nM, 10.6 nM, and 3.2 nM for FCV, REM, FAV, HCQ, CEP, and MOL, respectively. G-MWCNT-OH/IL/GCE was also highly stable and selective to the ATVs in the presence of multiple interfering analytes. This sensor exhibited great potential for enabling the quantitative detection of multiple ATVs in actual water environment.

Simultaneous Inside and Outside Functionalization of Single-Walled Carbon Nanotubes

Functionalizing single-walled carbon nanotubes (SWCNTs) in a robust way that does not affect the sp2 carbon framework is a considerable research challenge. Here we describe how triiodide salts of positively charged macrocycles can be used not only to functionalize SWCNTs from the outside, but simultaneously from the inside. We employed disulfide exchange in aqueous solvent to maximize the solvophobic effect and therefore achieve a high degree of macrocycle immobilization. Characterization by Raman spectroscopy, EDX-STEM and HR-TEM clearly showed that serendipitously this wet-chemical functionalization procedure also led to the encapsulation of polyiodide chains inside the nanotubes. The resulting three-shell composite materials are redox-active and experience an intriguing interplay of electrostatic, solvophobic and mechanical effects that could be of interest for applications in energy storage.

Development of ionic-liquid-impregnated activated carbon for sorptive removal of PFAS in drinking water treatment

Adsorption of per- and poly-fluoroalkyl substances (PFAS) on activated carbon (AC) is considerably hindered by the surface water constituents, degrading the ability of the AC adsorption process to remove PFAS in drinking water treatment. Herein, we developed ionic-liquid-impregnated AC (IL/AC) as an alternative to AC for PFAS sorption and demonstrated its performance with real surface water for the first time. Ionic liquids (ILs) of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (IL(C2)) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (IL(C6)) were selected from among 272 different ILs using the conductor-like screening model for realistic solvents (COSMO-RS) simulation. Impregnation of the ILs in AC was verified using various analytical techniques. Although the synthesized IL/ACs were less effective than pristine AC in treating PFAS in deionized water, their performances were less impacted by the surface water constituents, resulting in comparable or sometimes better performances than pristine AC for treating PFAS in surface water. The removal efficiencies of 10 wt% IL(C6)/AC for six PFAS were 1.40-1.96 times higher than those of pristine AC in a surface water sample containing 2.6 mg/L dissolved organic carbon and millimolar-level divalent cation concentration. PFAS partitioning from the surface water to ILs was not hindered by dissolved organic matter and was enhanced by the divalent cations, indicating the advantages of IL/ACs for treating significant amounts of PFAS in water. The synthesized IL/ACs were effective at treating coexisting pharmaceutical and personal-care products in surface water, showcasing their versatility for treating a broad range of water micropollutants.

Stable dispersion of carbon nanotubes in a molten salt of KNO3-NaNO3-NaNO2-LiNO3-LiOH

Carbon nanotubes (CNTs) have excellent mechanical and electrical properties; however, they suffer from dispersion problems in various applications. Traditional dispersing strategies of CNTs mostly use oxidation with strong acids or mechanical milling with high energy, which causes serious damage to the intrinsic structures and properties of CNTs. Therefore, it is important to develop new methods for dispersing CNTs without destroying their structures. This paper proposes to disperse CNTs in low-temperature molten salts composed of KNO3-NaNO3-NaNO2-LiNO3-LiOH. By adjusting the composition ratio of molten salts and alkaline, the interaction between charged ions and CNT electrons in the molten salt is studied. The alkaline molten salts can stably disperse CNTs and do not destroy their lengths, thereby offering better electric conductivity. This work will provide a new yet effective method for dispersing CNTs with high aspect ratios, which are important for the application of CNTs and other nanocarbons.

Hybrid Zn-β-Aminoporphyrin-Carbon Nanotubes: Pyrrolidine and Direct Covalent Linkage Recognition, and Multiple-Photo Response

To unveil and shape the molecular connectivity in (metallo)porphyrin-carbon nanotube hybrids are of main relevance for the multiple medicinal, photoelectronic, catalytic, and photocatalytic applications of these materials. Multi-walled carbon nanotubes (MWCNTs) were modified through 1,3-dipolar cycloaddition reactions with azomethine ylides generated in situ and carrying pentafluorophenyl groups, followed by immobilization of the β-amino-tetraphenylporphyrinate Zn(II). The functionalities were confirmed via XPS and FTIR, whereas Raman spectroscopy showed disruptions on the graphitic carbon nanotube surface upon both steps. The functionalization extension, measured via TGA mass loss and corroborated via XPS, was 0.2 mmol·g-1. Photophysical studies attest to the presence of the different porphyrin-carbon nanotube connectivity in the nanohybrid. Significantly different emission spectra and fluorescence anisotropy of 0.15-0.3 were observed upon variation of excitation wavelength. Vis-NIR absorption and flash photolysis experiments showed energy/charge transfer in the photoactivated nanohybrid. Moreover, evidence was found for direct reaction of amino groups with a carbon nanotube surface in the presence of molecular dipoles such as the zwitterionic sarcosine amino acid.

Ionic Liquids as Alternative Curing Agents for Conductive Epoxy/CNT Nanocomposites with Improved Adhesive Properties

Good dispersion of carbon nanotubes (CNTs) together with effective curing were obtained in epoxy/CNT nanocomposites (NCs) using three different ionic liquids (ILs). Compared to conventional amine-cured epoxy systems, lower electrical percolation thresholds were obtained in some of the IL-based epoxy systems. For example, the percolation threshold of the trihexyltetradecylphosphonium dicyanamide (IL-P-DCA)-based system was 0.001 wt.%. The addition of CNTs was not found to have any significant effect on the thermal or low-strain mechanical properties of the nanocomposites, but it did improve their adhesive properties considerably compared to the unfilled systems. This study demonstrates that ILs can be used to successfully replace traditional amine-based curing agents for the production of electrically conductive epoxy/CNT NCs and adhesives, as a similar or better balance of properties was achieved. This represents a step towards greater sustainability given that the vapor pressure of ILs is low, and the amount needed to effectively cure epoxy resins is significantly lower than any of their counterparts.

Polymethyl(1-Butyric acidyl)silane-Assisted Dispersion and Density Gradient Ultracentrifugation Separation of Single-Walled Carbon Nanotubes

Individual single–walled carbon nanotubes (SWNTs) with distinct electronic types are crucial for the fabrication of SWNTs–based electronic and magnetic devices. Herein, the water–soluble polymethyl(1–butyric acidyl)silane (BA–PMS) was synthesized via the hydrosilylation reaction between 3–butenoic acid and polymethylsilane catalyzed by 2,2′–azodibutyronitrile. As a new dispersant, BA–PMS displayed a quite good dispersing capacity to arc–discharged SWNTs and moderate selectivity for metallic species. The application of sucrose–DGU, the density gradient ultracentrifugation with sucrose as the gradient medium, to the co–surfactants (BA–PMS and sodium dodecyl sulfonate) individually dispersed SWNTs yielded metallic SWNTs of 85.6% purity and semiconducting SWNTs of 99% purity, respectively. This work paves a path to the DGU separation of the SWNTs dispersed by polymer–based dispersants with hydrophobic alkyl chains.

Characterization of Carbon Nanomaterials Dispersions: Can Metal Decoration of MWCNTs Improve Their Physicochemical Properties?

A suitable dispersion of carbon materials (e.g., carbon nanotubes (CNTs)) in an appropriate dispersant media, is a prerequisite for many technological applications (e.g., additive purposes, functionalization, mechanical reinforced materials for electrolytes and electrodes for energy storage applications, etc.). Deep eutectic solvents (DES) have been considered as a promising "green" alternative, providing a versatile replacement to volatile organic solvents due to their unique physical-chemical properties, being recognized as low-volatility fluids with great dispersant ability. The present work aims to contribute to appraise the effect of the presence of MWCNTs and Ag-functionalized MWCNTs on the physicochemical properties (viscosity, density, conductivity, surface tension and refractive index) of glyceline (choline chloride and glycerol, 1:2), a Type III DES. To benefit from possible synergetic effects, AgMWCNTs were prepared through pulse reverse electrodeposition of Ag nanoparticles into MWCNTs. Pristine MWCNTs were used as reference material and water as reference dispersant media for comparison purposes. The effect of temperature (20 to 60 °C) and concentration on the physicochemical properties of the carbon dispersions (0.2-1.0 mg cm^-3) were assessed. In all assessed physicochemical properties, AgMWCNTs outperformed pristine MWCNTs dispersions. A paradoxical effect was found in the viscosity trend in glyceline media, in which a marked decrease in the viscosity was found for the MWCNTs and AgMWCNTs materials at lower temperatures. All physicochemical parameters were statistically analyzed using a two-way analysis of variance (ANOVA), at a 5% level of significance.

Facile Fabrication of Single-Walled Carbon Nanotube/Anatase Composite Thin Film on Quartz Glass Substrate for Translucent Conductive Photoelectrode

A single-walled carbon nanotube/anatase (SWCNT/anatase) composite thin film with a transmittance of over 70% in the visible-light region was fabricated on a quartz glass substrate by heat treating a precursor film at 500 °C in air. The precursor film was formed by spin coating a mixed solution of the titania molecular precursor and well-dispersed SWCNTs (0.075 mass%) in ethanol. The anatase crystals and Ti3+ ions in the composite thin films were determined by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The effect of the heating process on the SWCNTs was analyzed using Raman spectroscopy. The composite film showed an even surface with a scratch resistance of 4H pencil hardness, as observed using field-emission scanning electron microscopy and atomic force microscopy. The electrical resistivity and optical bandgap energy of the composite thin film with a thickness of 100 nm were 6.6 × 10-2 Ω cm and 3.4 eV, respectively, when the SWCNT content in the composite thin film was 2.9 mass%. An anodic photocurrent density of 4.2 μA cm-2 was observed under ultraviolet light irradiation (16 mW cm-2 at 365 nm) onto the composite thin film, thus showing excellent properties as a photoelectrode without conductive substrates.

Functional Ionic Liquids Decorated Carbon Hybrid Nanomaterials for the Electrochemical Biosensors

Ionic liquids are gaining high attention due to their extremely unique physiochemical properties and are being utilized in numerous applications in the field of electrochemistry and bio-nanotechnology. The excellent ionic conductivity and the wide electrochemical window open a new avenue in the construction of electrochemical devices. On the other hand, carbon nanomaterials, such as graphene (GR), graphene oxide (GO), carbon dots (CDs), and carbon nanotubes (CNTs), are highly utilized in electrochemical applications. Since they have a large surface area, high conductivity, stability, and functionality, they are promising in biosensor applications. Nevertheless, the combination of ionic liquids (ILs) and carbon nanomaterials (CNMs) results in the functional ILs-CNMs hybrid nanocomposites with considerably improved surface chemistry and electrochemical properties. Moreover, the high functionality and biocompatibility of ILs favor the high loading of biomolecules on the electrode surface. They extremely enhance the sensitivity of the biosensor that reaches the ability of ultra-low detection limit. This review aims to provide the studies of the synthesis, properties, and bonding of functional ILs-CNMs. Further, their electrochemical sensors and biosensor applications for the detection of numerous analytes are also discussed.

Three-dimensional microspheres constructed with MoS2 nanosheets supported on multiwalled carbon nanotubes for optimized sodium storage

Molybdenum disulfide (MoS2) has been regarded as a promising anode material in the field of sodium-ion batteries (SIBs), with the advantages of high theoretical capacity and large interlayer spacings. Unfortunately, its intrinsic poor electrical conductivity and large volume changes during the sodiation/desodiation reactions still limit its practical application. To deal with this shortcoming, we built MoS2 nanosheet/multiwalled carbon nanotube (denoted as MoS2-MSs/MWCNTs) composites with a three-dimensional (3D) micro-spherical structure, assembled in situ from MoS2 nanosheets. These nanosheets are connected to each other by the MWCNTs network, which provides a highly conductive pathway for electrons/ions through interparticle and intraparticle interfaces, accelerating charge transfer and ion diffusion capabilities. More importantly, the carbon network can boost electrical conductivity and relieve structural strain. Consequently, the as-prepared MoS2-MSs/MWCNTs composite presents a high reversible specific capacity of 519 mA h g-1 at 0.1 A g-1 after 100 cycles with a capacity retention of 94.4% and excellent rate performance (227 mA h g-1 at 10 A g-1). Outstanding cycling stability was also achieved (327.1 mA h g-1 over 1000 cycles at 2 A g-1) and was characterized by scanning electron microscopy (SEM) analysis. Our findings provide a simple and effective strategy to explore anode materials with advanced sodium storage properties.

Synergistic Behavior of Graphene and Ionic Liquid as Bio-Based Lubricant Additive

The constant utilization of petroleum-based products has prompted concerns about the environment, hence a replacement for these products must be explored. Biolubricants are a suitable replacement for petroleum-based lubricants as they provide better lubricity. Biolubricant performance can be improved by the addition of graphene. However, there are reports that graphene is unable to form a stable suspension for a long period. This study used a graphene-ionic liquid additive combination to stabilize the dispersion in a biolubricant. Graphene and ionic liquid were dispersed into the biolubricant via a magnetic stirrer. The samples were tested using a high frequency reciprocating rig. The cast iron sample was then further observed using various techniques to determine the lubricating mechanism of the lubricant. Different dispersion stability of graphene was observed for different biolubricants, which can be improved with ionic liquids. All ionic liquid samples maintained an absorbance value of three for one month. The utilization of ionic liquid was also able to decrease the frictional performance by 33%. Further study showed that by using the ionic liquid alone, the frictional could only reduce the friction coefficient by 13% and graphene could only reduce the friction by 7%. A smooth worn surface scar can be seen on the graphene-IL sample compared to the prominent corrosive spot on the IL samples and abrasive scars on graphene samples. This indicates synergistic behavior between the two additives. It was found that the ionic liquid does not only improve the dispersion stability, but also plays a role in forming the tribolayer.

Improvement of the electromechanical properties of thermoplastic polyurethane composite by ionic liquid modified multiwall carbon nanotubes

Carbon nanotubes (CNTs) were non-covalently modified by two categories of ionic liquids (ILs), including 1-vinyl-3-ethylimidazole bromide (VEIMBr) and 1-vinyl-3-hexylimidazole bromide (VHIMBr) in the ratio of 1:1 and 1:4, respectively. The surface interaction between CNTs and ILs was well-characterized by FTIR, Raman spectra, XPS, etc. Thermoplastic polyurethane (TPU) containing different amounts of CNTs/ILs was fabricated by melting blending method. TPU-CNTs/ILs composites exhibited simultaneously enhanced electromechanical properties with improved dielectric constant and lowered elastic modulus. The electromechanical sensitivity of sample TPU-3CNT/12VHIMBr increased by approximately 45 times in comparison with that of pure TPU at 200 Hz. Besides, improved dispersion of CNTs/ILs in the TPU matrix was also exhibited.

Coupling magnetic and plasmonic anisotropy in hybrid nanorods for mechanochromic responses

Mechanochromic response is of great importance in designing bionic robot systems and colorimetric devices. Unfortunately, compared to mimicking motions of natural creatures, fabricating mechanochromic systems with programmable colorimetric responses remains challenging. Herein, we report the development of unconventional mechanochromic films based on hybrid nanorods integrated with magnetic and plasmonic anisotropy. Magnetic-plasmonic hybrid nanorods have been synthesized through a unique space-confined seed-mediated process, which represents an open platform for preparing next-generation complex nanostructures. By coupling magnetic and plasmonic anisotropy, the plasmonic excitation of the hybrid nanorods could be collectively regulated using magnetic fields. It facilitates convenient incorporation of the hybrid nanorods into polymer films with a well-controlled orientation and enables sensitive colorimetric changes in response to linear and angular motions. The combination of unique synthesis and convenient magnetic alignment provides an advanced approach for designing programmable mechanochromic devices with the desired precision, flexibility, and scalability.

Cation-π Interactions in Graphene-Containing Systems for Water Treatment and Beyond

Cation-π interactions are common in nature, especially in organisms. Their profound influences in chemistry, physics, and biology have been continuously investigated since they were discovered in 1981. However, the importance of cation-π interactions in materials science, regarding carbonaceous nanomaterials, has just been realized. The interplay between cations and delocalized polarizable π electrons of graphene would bring about significant changes to the intrinsic characteristics of graphene and greatly affect the device performance based on graphene and its derivatives. Here, the cation-π interactions in graphene containing systems for water treatment applications (e.g., separation membranes, adsorbents) are highlighted. The cross-linking effects caused by cation-π interactions contribute to membrane stability and selectivity and enhanced adsorption. Their roles in dominating the performance of graphene-based structures for other specific applications are also discussed. Relevant theoretical modeling and calculations are summarized to offer an in-depth understanding of the underlying mechanisms which can help in designing more functional materials and structures. Perspectives on the potential directions that deserve effort are also presented.

Chirality Pure Carbon Nanotubes: Growth, Sorting, and Characterization

Single-walled carbon nanotubes (SWCNTs) have been attracting tremendous attention owing to their structure (chirality) dependent outstanding properties, which endow them with great potential in a wide range of applications. The preparation of chirality-pure SWCNTs is not only a great scientific challenge but also a crucial requirement for many high-end applications. As such, research activities in this area over the last two decades have been very extensive. In this review, we summarize recent achievements and accumulated knowledge thus far and discuss future developments and remaining challenges from three aspects: controlled growth, postsynthesis sorting, and characterization techniques. In the growth part, we focus on the mechanism of chirality-controlled growth and catalyst design. In the sorting part, we organize and analyze existing literature based on sorting targets rather than methods. Since chirality assignment and quantification is essential in the study of selective preparation, we also include in the last part a comprehensive description and discussion of characterization techniques for SWCNTs. It is our view that even though progress made in this area is impressive, more efforts are still needed to develop both methodologies for preparing ultrapure (e.g., >99.99%) SWCNTs in large quantity and nondestructive fast characterization techniques with high spatial resolution for various nanotube samples.

Efficient reduction of graphene oxide to graphene nanosheets using a silica-based ionic liquid: synthesis, characterization and catalytic properties of IMD-Si/FeCl4−@GNS

Ionic liquid-modified graphene nanosheets (IMD-Si/FeCl₄⁻@GNS) have been synthesized as efficient catalysts for the synthesis of (E)-selective thiosemicarbazones.

Bioelectrocatalysis at carbon nanotubes

This paper summarizes several examples of enzyme immobilization and bioelectrocatalysis at carbon nanotubes (CNTs). CNTs offer substantial improvements on the overall performance of amperometric enzyme electrodes mainly due to their unique structural, mechanical and electronic properties such as metallic, semi-conducting and superconducting electron transport. Unfortunately, their water insolubility restrains the kick-off in some particular fields. However, the chemical functionalization of CNTs, non-covalent and covalent, attracted a remarkable interest over the past several decades boosting the development of electrochemical biosensors and enzymatic fuel cells (EFCs) based on two different types of communications: mediated electron transfer (MET)-type, where the use of redox mediators, small electroactive molecules (freely diffusing or bound to side chains of flexible redox polymers), which are able to shuttle the electrons between the enzyme active site and the electrode (second electron transfer generation system); direct electron transfer (DET)-type between the redox group of the enzyme and the electrode surface (third electron transfer generation system).

Electroconductive starch/multi-walled carbon nanotube films plasticized by 1-ethyl-3-methylimidazolium acetate

Starch/multi-walled carbon nanotube (MWCNT) films were prepared by casting using an ionic liquid (1-ethyl-3-methylimidazolium acetate, [emim⁺][Ac^-]) as plasticizer for the first time. The effect of the MWCNT content (0.25-5 wt.%, with respect to the sum of starch and plasticizer mass) on thermal, mechanical and electroconductive behavior of the films was studied. Films containing 0.5 wt.% MWCNT showed increases of 327 % in maximum tensile strength, 2484 % in Young's modulus and 82 % in elongation at break. The significant improvements are explained by the good MWCNT dispersion in the matrix and by the effect of [emim⁺][Ac^-] as an efficient plasticizer, which leads to higher extensibility. The MWCNT/[emim⁺][Ac^-] combination have a synergistic effect on film electrical conductivity, increasing a 130% (3 wt.% MWCNT). These films, easily prepared by a "green" process, have potential applications in the packaging industry but also in the field of lithium batteries, fuel cells and dye-sensitized solar cells.

Alloyed Pt3M (M = Co, Ni) nanoparticles supported on S- and N-doped carbon nanotubes for the oxygen reduction reaction

Sulfur- (S-CNT) and nitrogen-doped (N-CNT) carbon nanotubes have been produced by catalytic chemical vapor deposition (c-CVD) and were subject to an annealing treatment. These CNTs were used as supports for small (≈2 nm) Pt₃M (M = Co or Ni) alloyed nanoparticles that have a very homogeneous size distribution (in spite of the high metal loading of ≈40 wt % Pt), using an ionic liquid as a stabilizer. The electrochemical surface area, the activity for the oxygen reduction reaction and the amount of H₂O₂ generated during the oxygen reduction reaction (ORR) have been evaluated in a rotating ring disk electrode experiment. The Pt₃M/N-CNT catalysts revealed excellent electrochemical properties compared to a commercial Pt₃Co/Vulcan XC-72 catalyst. The nature of the carbon support plays a key role in determining the properties of the metal nanoparticles, on the preparation of the catalytic layer, and on the electrocatalytic performance in the ORR. On N-CNT supports, the specific activity followed the expected order Pt₃Co > Pt₃Ni, whereas on the annealed N-CNT support, the order was reversed.

Dispersion and Stabilization of Exfoliated Graphene in Ionic Liquids

The liquid-phase exfoliation of graphite is one of the most promising methods to increase production and commercial availability of graphene. Because ionic liquids can be easily obtained with chosen molecular structures and tuneable physicochemical properties, they can be use as media to optimize the exfoliation of graphite. The understanding of the interactions involved between graphite and various chemical functions in the solvent ions will be helpful to find liquids capable of dissociating and stabilizing important quantities of large graphene layers. After a step of sonication, as a mechanical precursor, samples of suspended exfoliated graphene in different ionic liquids have been characterized experimentally in terms of flake size, number of layers, total concentration and purity of the exfoliated material. Nine different ionic liquids based on imidazolium, pyrrolidinium and ammonium cations and on bis(trifluoromethylsulfonyl)imide, triflate, dicyanamide, tricyanomethanide, and methyl sulfate anions have been tested. UV-vis, Raman and X-ray photoelectron in addition to high resolution transmission electron and atomic force microscopy have been selected to characterize suspended exfoliated graphene in ionic liquids. The number of layers in the flakes exfoliated, the size and concentration depend of the structure of the ionic liquid selected. In order to obtain large flake sizes, ionic liquids with bis(trifluoromethylsulfonyl)imide anions and a cation with an alkyl chain of medium length should be selected. Smaller cation and anion favors the exfoliation of graphene. The exfoliation caused the formation of C-H bonds and the oxidation of the graphitic surface.

Modulating Chirality-Selective Photoluminescence of Single-Walled Carbon Nanotubes by Ionic Liquids

The chirality-selective near-infrared emission of surfactant-stabilized single-wall carbon nanotubes could be controlled by simply varying the anion of the commonly used 1-butyl-3-methylimidazolium ionic liquids. This result advances the notion of the designer solvent ability of ionic liquids and provides opportunities for modulating the properties of nanomaterials.