Carbon nanotubes (CNTs) possess superior mechanical, physical and chemical properties that make them ideal candidates for making sensors. However, challenges restricting their widespread applications in sensors still exist. To make the CNTs-based sensors own higher performance, nature has offered us with scientific and technological clues from the formation of biological composites using common organic components via naturally mild approaches. This paper reviews the recent progress on the bio-inspired synthesis of the CNTs-based sensors and their unique structures and novel properties.

In situ X-ray absorption near edge structure (XANES) measurements were conducted to elucidate the chemical states of Co and Ni catalysts during single-walled carbon nanotube (SWCNT) growth via chemical vapor deposition (CVD). XANES spectra indicated that both Co and Ni catalysts partially oxidized before heating. It was found that Co catalysts formed carbides during the SWCNT growth. In contrast, Ni catalysts remained metallic state even after the SWCNT growth had begun. These results indicate that during SWCNT growth, carbon atoms dissolve into Co particles, whereas for Ni particles, they diffuse on the surface region. It was concluded that the growth mechanisms of SWCNTs formed by CVD differed for either Co or Ni catalyst.

Natural graphite can be exfoliated into thin films by trapping it at the interface between water and heptane [S. J Woltornist, A. J. Oyer, J-M. Y. Carrillo, A.V. Dobrynin, and D.H. Adamson, ACS Nano 7, 7062 (2013)]. In this work, we add functional elements into these graphitic thin films by introducing additives into the water phase prior to exfoliation. We report the successful incorporation of ZnO nanoparticles thereby enabling the composite films to act as effective ultraviolet photodetectors. In a similar manner, integration of silver nanowires is achieved, which results in an enhancement of the electrical conductivity of graphite.

Extensive work has been done on the modification of multi-walled carbon nanotubes (MWCNTs) to improve their characteristics. Here, polystyrene (PS) was adsorbed on the surface of MWCNTs by dispersion process, using toluene as medium. PS modified MWCNTs (PS-MWCNTs) have been dispersed in polymethylmethacrylate (PMMA) matrix to prepare composite, PS-MWCNTs/PMMA. It is expected that PS adsorbed at the surface of the MWCNTs will help in improving the interaction between MWCNTs and PMMA which results uniform and homogeneous dispersion of the former in later. Thus, synthesized composites were characterized by UV-Vis and FTIR spectroscopy to monitor the functionality of developed product. Electrical parameters including conductivity and dielectric properties were measured with the help of LCR meter. Electrical characters of the composites were explored by investigating the effect of contents of PS-MWCNTs on conductivity and dielectric properties. Percolation behaviour was examined and calculated value of percolation threshold was 0.1wt%.

Composite of PZT (lead zirconate titanate) and PLZT (lead lanthanum zirconate titanate) along an organic, renewable, conductive, and flexible matrix have been developed. The conductive paper was obtained through the reaction between the cellulose extracted from banana stem and functionalized MWCNT. This reaction was made in the presence of hydrogen (from H2SO4), which reduced the size of the cellulose by acid hydrolysis and promotes the interaction between its hydroxyls and the carboxyl groups of nanotubes. Afterward, the PZT particles were synthesized and grown up on the conductive paper by microwaves-assisted hydrothermal synthesis (MHS). The composite material was characterized by structure and morphology. Moreover, gas-sensing in the presence of methanol and electrical resistance as a function of temperature were also investigated. In this way, a simple, low-cost and successful synthesis was reported. Also, a promising flexible was obtained using a chemical transformation process from banana residue as source of cellulose.

As an emerging carbon material with advantages of thinnest, ultrahigh strength, superior thermal conductivity and electrical conductivity, graphene (Gr) is called the “black gold” and will have a profound applying potential in the field of materials science and engineering. Many researches concerning preparation of the Cu-Gr composite via various approaches have been reported. However, only few works are related to the electrochemical deposition method. As a simple, low cost, large scale production method, electrodeposition method has been widely used in industry for manufacturing foils involving copper-clad laminate (CCL), printed circuit board (PCB) and the negative current collector of lithium ion battery, where the copper foil not only serve as the carrier of the cathode active material but also play a role in collecting and conducting electrons. In the present article, we review the research progress on preparations and mechanical properties of the Cu-Gr composite foils by electrochemical method, and introduce our recent work in this area. The advancement of the process and the perspective industrial productions are also discussed.

This paper presents experimental results on the synthesis of boron rich diamond-like carbon phases (BCx) obtained by high pressure sintering (s-BCx) and pulsed laser deposition (PLD-BCx). It has been shown that sintering of a mixture of a powder of micro-diamonds with a powder of boron in the toroid type high pressure device leads to the creation of s-BCx phase with a low resistivity, and high elastic moduli. The PLD-BCx film found to be rigid with the resistivity as low as that of best conductive boron–doped diamond films. It indicates that the presence of B atoms in a laser plasma leads to the formation of sp3 bonds in the material in the process of chemical sputtering. The combination of unique characteristics can be achieved by changing the ratio B/C.

Growth of single-walled carbon nanotube (SWCNT) was achieved by an alcohol catalytic chemical vapor deposition (CVD) mechanism that was conducted in a high vacuum using Ru catalysts. By optimizing the ethanol pressure, SWCNTs can grow in a wide range of temperature between 500 °C and 900 °C. Both the yield and crystalline quality of SWCNTs reached their maxima at 700 °C. Significantly, the SWCNT growth was achieved even at 450 °C, which was much lower than the growth temperatures that were required for SWCNT growth using Ru catalysts previously. Raman measurements exhibited that the diameter distribution of the SWCNTs that were grown at 450 °C was quite narrow and (11, 4) nanotubes were dominant. The observations of transmission electron microscope (TEM) suggested that the size of the Ru particles were larger than the diameter of SWCNT. Such a relation was similar to the relation observed in the growth of SWCNTs using Pt catalysts.

Low-density, highly porous graphene/graphene oxide (GO) based-foams have shown high performance in energy absorption applications, even under high compressive deformations. In general, foams are very effective as energy dissipative materials and have been widely used in many areas such as automotive, aerospace and biomedical industries. In the case of graphene-based foams, the good mechanical properties are mainly attributed to the intrinsic graphene and/or GO electronic and mechanical properties. Despite the attractive physical properties of graphene/GO based-foams, their structural and thermal stabilities are still a problem for some applications. For instance, they are easily degraded when placed in flowing solutions, either by the collapsing of their layers or just by structural disintegration into small pieces. Recently, a new and scalable synthetic approach to produce low-density 3D macroscopic GO structure interconnected with polydimethylsiloxane (PDMS) polymeric chains (pGO) was proposed. A controlled amount of PDMS is infused into the freeze-dried foam resulting into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like a glue bonding PDMS and GO sheets. In order to obtain further insights on mechanisms behind the enhanced mechanical pGO response we carried out fully atomistic molecular dynamics (MD) simulations. Based on MD results, we build up a structural model that can explain the experimentally observed mechanical behavior.

Recently, a new 2D carbon allotrope structure, named phagraphene (PG), was proposed. PG has a densely array of penta-hexa-hepta-graphene carbon rings. PG was shown to present low and anisotropic thermal conductivity and it is believed that this anisotropy should be also reflected in its mechanical properties. Although PG mechanical properties have been investigated, a detailed and comprehensive study is still lacking. In the present work we have carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field, to investigate the mechanical properties and fracture patterns of PG membranes. The Young’s modulus values of the PG membranes were estimated from the stress-strain curves. Our results show that these curves present three distinct regimes: one regime where ripples dominate the structure and mechanical properties of the PG membranes; an elastic regime where the membranes exhibit fully planar configurations; and finally am inelastic regime where permanent deformations happened to the PG membrane up to the mechanical failure or fracture.

Graphene is a very promising material for nanoelectronics applications due to its unique and remarkable electronic and thermal properties. However, when deposited on metallic electrodes the overall thermal conductivity is significantly decreased. This phenomenon has been attributed to the mismatch between the interfaces and contact thermal resistance. Experimentally, one way to improve the graphene/metal contact is through high-temperature annealing, but the detailed mechanisms behind these processes remain unclear. In order to address these questions, we carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field to investigate the interactions between multi-layer graphene and metallic electrodes (nickel) under (thermal) annealing. Our results show that the annealing induces an upward-downward movement of the graphene layers, causing a pile-driver-like effect over the metallic surface. This graphene induced movements cause a planarization (thermal polishing-like effect) of the metallic surface, which results in the increase of the effective graphene/metal contact area. This can also explain the experimentally observed improvements of the thermal and electric conductivities.

This contribution deals with the fabrication of a new generation of supercapacitors for harsh environment (avionics) based on nanostructures layers fabricated by spray-gun deposition method. Thanks to the fabrication of electrodes using spray-gun and the utilization of specific ionic liquids developed at Thales, we were able to achieve a capacitance of 20F/g (for a whole cell) and a power of 40kW/kg using carbon nanofibres (CNFs) mixed with reduced graphene oxide (RGO). These results are not the higher values obtained in literature but they are extremely interesting considering that the final device needs to stand temperature between -55°C and +105°C for avionics applications and that no commercial supercaps in the world are able to work in this interval. Only using these ionic liquids and the specific electrodes, it is possible. These supercapacitors were fabricated using spray-gun deposition method which is an extremely interesting technique from an industrial point of view considering that it can be easily implemented in roll-to-roll fabrication.

Development of solid polymer electrolytes has potential applications for battery technology. Membranes should be environment friendly and also have high conductivity. We use chitosan, cellulose and graphene in this research. In this work, 1% (w/v) of chitosan powder and 1.5% (w/v) of acetic acid were dissolved in double distilled water. The solution was heated to 60°C under constant stirring until the chitosan powder was completely dissolved and a semi-transparent thick chitosan solution was obtained. To this chitosan solution, appropriate amounts of graphene (grade H5-XG Sciences) was added to have 5, 10, 20 and 30% graphene (weight with respect to chitosan). The solution was sonicated for dispersing graphene and then 100ml of it was poured on plastic dishes with and without cellulose fabric in it. The films were dried by slow evaporation technique. The sample thickness varied from 200 to 300µm. SEM images showed that chitosan film formed on cellulose and had grid like structures. Chitosan deposited more on the fibres of the cellulose. This is attributed to the rectangle shaped micro pores of cellulose fabric. From the cross section of the films, it was observed that graphene arranged in stacks along the plane of the cellulose fabric and the fabric became darker as graphene concentration increased. The dielectric properties such as dielectric constant, impedance, conductivity and dissipation factor were measured from 102 - 106 Hz. The conductivity of the sample increased as the frequency increased. The conductivity of the samples at room temperature increased with increase in graphene concentrations. The conductivity varied from 10-8 to 10-5 S/Cm as the graphene concentration increases from 0 to 30%. Hence conductivity increases significantly as graphene concentration increases. From the dissipation factor for the films, the relaxation process could be observed in the frequency ranging from 102 to 105 Hz. It is observed that as frequency increases, the relaxation tend to shift towards higher frequency indicating that graphene affects the relaxation of the polymer nanocomposite. At high frequency (106Hz) dissipation factor for cellulose fabric, chitosan in cellulose, chitosan with 5% graphene in cellulose, chitosan with 10% graphene in cellulose, chitosan with 20% graphene in cellulose, chitosan with 30% graphene in cellulose are 0.14, 0.19, 0.4, 0.8 and 1.38 respectively. This shows that dissipation factor increases as the graphene concentration increases. This implies that graphene improves heat dissipation in these films. The dielectric constant was observed to be maximum for chitosan with 30% graphene in cellulose indicating that the graphene may assemble into percolation networks at higher concentrations of graphene (20 and 30%).

In this study, we examined the limitations in growth temperatures for single-walled carbon nanotube (SWNT) forest synthesis using a water (H2O) growth enhancer as highlighted by a dramatic decrease in growth efficiency at high temperatures. Comparative synthesis using a carbon monoxide (CO) growth enhancer demonstrated a wider temperature window for SWNT forest synthesis. We found that SWNT forests taller than 100 μm could not been synthesized above 850 °C by using H2O, but by using CO, tall (>800 μm) forests could be synthesized at growth temperatures exceeding 900 °C. The dependency of H2O concentration showed that H2O, itself, was the cause for the reduced growth efficiency observed at higher temperatures. In contrast, increased CO concentrations did not result in any drop in the carbon nanotube (CNT) yield across the entire temperature range. While a severe drop of CNT yield above 950 °C was observed when CO was used, the origin was found to stem from catalyst particle aggregation enhanced by diffusion on the surface rather than CO itself. Therefore, the ability to synthesize at higher growth temperatures is advantageous when using more stable carbon feedstocks, such as methane.

The study of the mechanical properties of nanostructured systems has gained importance in theoretical and experimental research in recent years. Carbon nanotubes (CNTs) are one of the strongest nanomaterials found in nature, with Young’s Modulus (EY) in the order 1.25 TPa. One interesting question is about the possibility of generating new nanostructures with 1D symmetry and with similar and/or superior CNT properties. In this work, we present a study on the dynamical, structural, mechanical properties, fracture patterns and EY values for one class of these structures, the so-called pentagraphene nanotubes (PGNTs). These tubes are formed rolling up pentagraphene membranes (which are quasi-bidimensional structures formed by densely compacted pentagons of carbon atoms in sp3 and sp2 hybridized states) in the same form that CNTs are formed from rolling up graphene membranes. We carried out fully atomistic molecular dynamics simulations using the ReaxFF force field. We have considered zigzag-like and armchair-like PGNTs of different diameters. Our results show that PGNTs present EY ∼ 800 GPa with distinct elastic behavior in relation to CNTs, mainly associated with mechanical failure, chirality dependent fracture patterns and extensive structural reconstructions.

A nanomaterial that attracts the attention in a variety of research areas is multiwall carbon nanotubes (MWCNTs), due to their good mechanical proprieties, and high electrical and thermal conductivity. For this reason, the preparation of three-dimensional (3D) structures from them draws interest because it opens new horizons to produce materials with novel properties and useful applications. In this investigation the synthesis of 3D nanotube carbon (nanoforest type) functionalized with nanoparticles of silver, aluminum, and iron was studied. A 3D structure was produced in the form of aligned microchannels. The functionalization of carbon nanotubes with nanoparticles of silver, aluminum or iron during the synthesis process of carbon nanotubes, was carried out through spray-pyrolysis with different synthesis time and solution concentration. The results were characterized through microscopy SEM, TEM and Raman’s spectroscopy.

Graphene-based membranes have been investigated as promising candidates for water filtration and gas separation applications. Experimental evidences have shown that graphene oxide can be impermeable to liquids, vapors and gases, while allowing a fast permeation of water molecules. This phenomenon has been attributed to the formation of a network of nano capillaries that allow nearly frictionless water flow while blocking other molecules by steric hindrance effects. It is supposed that water molecules are transported through the percolated two-dimensional channels formed between graphene-based sheets. Although these channels allow fast water permeation in such materials, the flow rates are strongly dependent on how the membranes are fabricated. Also, some fundamental issues regarding the nanoscale mechanisms of water permeation are still not fully understood and their interpretation remains controversial. In this work, we have investigated the dynamics of water permeation through pristine graphene and graphene oxide model membranes that have strong impact on water/alcohol separation. We have carried out fully atomistic classical molecular dynamics simulations of systems composed of multiple layered graphene-based sheets into contact with a pure water reservoir under controlled thermodynamics conditions (e. g., by varying temperature and pressure values). We have systematically analysed how the transport dynamics of the confined nanofluids depend on the interlayer distances and the role of the oxide functional groups. Our results show the water flux is much more effective for graphene than for graphene oxide membranes. These results can be attributed to the H-bonds formation between oxide functional groups and water, which traps the water molecules and precludes ultrafast water transport through the nanochannels.

The 3D porous carbon-based structures called Schwarzites have been recently a subject of renewed interest due to the possibility of being synthesized in the near future. These structures exhibit negatively curvature topologies with tuneable porous sizes and shapes, which make them natural candidates for applications such as CO2 capture, gas storage and separation. Nevertheless, the adsorption properties of these materials have not been fully investigated. Following this motivation, we have carried out Grand-Canonical Monte Carlo simulations to study the adsorption of small molecules such as CO2, CO, CH4, N2 and H2, in a series of Schwarzites structures. Here, we present our preliminary results on natural gas adsorptive capacity in association with analyses of the guest-host interaction strengths. Our results show that Schwarzites P7par, P8bal and IWPg are the most promising structures with very high CO2 and CH4 adsorption capacity and low saturation pressure (<1bar) at ambient temperature. The P688 is interesting for H2 storage due to its exceptional high H2 adsorption enthalpy value of -19kJ/mol.

Nowadays, carbon nanotubes have a lot of applications in daily life, being applied in the fabrication of cellphones, computers, nanotransistors, among many others. Currently, their new applications in biotechnology area are in research, in particular in order to find new biosensors with fluorescent properties applying on the basis of multi-wall carbon nanotubes (MWCNTs). In this work, the obtaining of carbon nanoparticles having fluorescent properties via spray pyrolysis is presented. Synthesis, properties, structural peculiarities, and applications of nanobuds and related nanostructures are discussed. MWCNTs, decorated with strontium aluminate SrAl12O19 and doped with rare-earth elements, were synthetized from distinct organic precursors and the corresponding metal oxides. The metal oxides used were Samarium (Sm), Europium (Eu), Neodymium (Nd), Lanthanum (La), Cerium (Ce) and some their combinations.

The synthesis was carried out on the surface of optical fibres to obtain a uniform growth of forest-like MWCNTs, adding to metal oxide nanoparticles to their surface. The preparation of composites was carried out by spray pyrolysis techniques in dry nitrogen atmosphere in the temperature range from 780 to 850°C. The formed products were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), FTIR spectroscopy, Raman spectroscopy and UV/visible spectroscopies. The analysis of the obtained data shows that the deposited nanoparticles are in the range of size 20-60 nm being uniformly distributed on the surface of MWCNTs. The samples, obtained at different temperatures and with doping metal oxides added to SrAl12O19, show different fluorescence behavior. The best results were observed with lanthanum oxide as a dopant. Possible applications as persistently luminescent phosphors for the formed MWCNTs-supported luminescent materials are proposed.