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In this paper results of a study of mechanical, optical and electrical properties of thin films made of multiwall carbon nanotubes (MWCNT) of various types were reported. The MWCNT films were obtained on quartz substrates using the Langmuir-Schaefer (LS) method. A gradual increase in transmittance was recorded with decreasing diameters of MWCNT used. Moreover, a blue shift of the π-plasmon band position was observed with increasing MWCNT diameter. In all tested films, anisotropy of electrical surface resistivity was revealed, which was more pronounced for MWCNT of low diameters, except for the MWCNT sample of the smallest diameters. Results of oscillatory barrier measurements of various MWCNT films at the air water interface were used to calculate the complex compression and shear moduli. It is worth emphasizing that the values of these moduli were obtained for the first time for carbon nanotubes films. Moreover, the obtained results allowed identification of the main factor blocking the alignment process, which turned out to be the shear loss tangent.

The Langmuir and Langmuir-Blodgett techniques have been widely used for nearly a century for the production of molecular thin layers with controlled packing and intermolecular distances. Unfortunately, the Langmuir layers of non-amphiphilic molecules have unstable and unrepeatable parameters. The addition of chemical compounds such as liquid crystals can stabilize and prevent aggregation in the Langmuir layer. The aim of the study was to obtain and characterize Langmuir and Langmuir-Blodgett layers of selected dithiophene diketopyrrolopyrrole (DPP) derivatives and to improve their parameters by forming mixtures with 4‑octyl‑4′‑cyanobiphenyl (8CB). Two DPPs with alkyl chains symmetrically and asymmetrically attached to pyrrole unit were chosen for the investigation. The Langmuir layer of the asymmetrical DPP was unstable over time. For the symmetrically functionalized DPP, after transferring onto solid substrates, agglomerates formation was clearly seen. For DPPs/8CB mixtures, a significant improvement in stability over time was achieved. The confocal microscopy investigation revealed almost complete removal of agglomerate structures in the symmetrical DPP with 8CB. The results proved the miscibility of components at air/water interface and the stabilizing effect of 8CB on DPPs layers. Furthermore, the addition of 8CB forces DPP J-type aggregation in the Langmuir film. Above all, the stable layers with repeatable parameters, made of indistinctly amphiphilic DPP dyes, were shown to form at the air/water interface and on solid substrates.

The (N-Xy-Qn)(TCNQ)

The Multiwalled carbon nanotube (MWCNT) thin films has been formed on PVC substrate using Langmuir-Blodgett technique as highly promising material for optoelectronics. The layers were annealed at 367 K which has led to significant electrical resistance decrease. The resistance of the obtained layer was investigated in wide temperature range showing the dependence significantly different from that observed for the layers created using CNTs of smaller diameter. The reason of the unusual conductivity temperature dependence is most probably the difference in thermal expansion coefficients of MWCNTs and the polymer combined with relatively high stiffness of the nanotubes with such large diameter.

Colloidally synthesized semiconductor nanoparticles have been receiving much attention due to their potential application in the area of photovoltaics, optic devices, biology, and medicine. This work explains how semiconductor CdTeSe/ZnS quantum dots (QDs) with the surface modified by trioctylphosphine oxide (TOPO) were dispersed on the surface of water. The studies of the organization and behavior of formation layers of CdTeSe/ZnS were followed by surface pressure-area isotherm measurements, in-situ absorption spectroscopy, Brewster Angle Microscopy (BAM) and surface potential measurements. The conducted research shows that CdTeSe/ZnS QDs form a tightly-packed, thin layer at the water-air interface, which can be easily deposited on different surfaces with the Langmuir-Blodgett and Langmuir-Schafer techniques.

Ultrasonic homogenization is the method of choice for producing and dispersing graphene. In this paper, we show that sp3 hybridization defects introduced by long high-power sonication cause a significant decrease in electrical conductivity. In order to show this, two turbostratic graphene (TG) dispersions were sonicated at two power settings of the tip sonifier at 20 W and 60 W, and for different periods varying from 1 min to 180 min. Afterwards, TG thin films were prepared by the Langmuir technique and transferred onto a quartz substrate by the Langmuir–Schaefer method. The thin films were investigated by electrical conductivity measurement, UV-VIS, Raman spectroscopy and scanning electron microscopy. We found that the relative performance of the TG thin films in terms of transparency and sheet resistance was higher than that for similarly prepared pristine graphene flakes, reported in our previous work. Moreover, despite the increase in transmittance, the electrical conductance significantly decreases with the time of sonication, especially for the 60 W sonication power. The results of Raman spectroscopy indicate that this particular behavior can be explained by the introduction of sp3 hybridization defects into the TG flakes during high power sonication.

Thin films of randomly dispersed carbon nanotubes make highly promising material for transparent electrode applications. Knowing and understanding the nature of the films conductivity is crucial for improvement of their electrical properties. In the paper we present our investigation of electrical conductivity of single wall and multiwalled carbon nanotube (SWCNT and MWCNT) thin films deposited on a polymeric substrate by Langmuir-Schaefer technique. The conductivity of the films is consistent with the Variable Range Hopping (VRH) model. Moreover, remarkable differences in SWCNT and MWCNT films conductivity are observed. A significant impact of the thin film annealing and its temperature history on the conductivity properties is shown. The study of the carbon nanotubes layers transferred on polymeric substrate was undertaken in view of the films possible applications in flexible transparent electrodes. The VRH conductivity in carbon nanotube Langmuir-Schaefer layer is reported for the first time.

Lithium manganese oxide (LiMn2O4) of spinel structure is a very attractive and widely applied active material for lithium ion cells because of high potential vs. metallic lithium content, non-toxicity and low cost of production. Unfortunately, the capacity fading at higher current densities limits its application in fast charging batteries. One of the solutions to this problem is modification of the interface between the current collector and the cathode mass. In this paper we proposed a modification of aluminum current collector by coating it with a thin film of multiwalled carbon nanotubes. Two variants of Langmuir-Schaefer method have been used for the first time to produce the film modifying the interface between the collector and the active material. The proposed modification of the current collector resulted in reduction of charge-transfer resistance and consequently in increasing cells capacity at high current densities.

While the carbon nanotubes are characterized by excellent electrical, mechanical and thermal properties, which makes them a good candidate for many applications, e.g. as a transparent electrode for photovoltaics, there is still no adequate method for the formation of thin conductive carbon nanotube films. Here we report the Langmuir–Schaefer method for the fabrication of large scale, homogeneous multiwall carbon nanotube layers with good optical and electrical properties. We show that the layers obtained are characterized by optical and electrical anisotropies, which can be controlled by the direction of the barrier and surface pressure during the layer transfer.

Correction for ‘The influence of diameter of multiwalled carbon nanotubes on mechanical, optical and electrical properties of Langmuir–Schaefer films’ by Karol Rytel et al., Phys. Chem. Chem. Phys., 2020, DOI: 10.1039/d0cp03687k.