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Funding Information: This work was supported by Russian Foundation for Basic Research Grant No. 18-29-06071. We thank the Council on grants of the President of the Russian Federation grant number HIII-1330.2022.1.3. F.F. and D.K. thank Russian Science Foundation, Grant No. 21-73-10288 for support of impedance spectroscopy studies. Publisher Copyright: © 2022 American Chemical Society. All rights reserved. Stretchable and flexible electronics has attracted broad attention over the last years. Nanocomposites based on elastomers and carbon nanotubes are a promising material for soft electronic applications. Despite the fact that single-walled carbon nanotube (SWCNT) based nanocomposites often demonstrate superior properties, the vast majority of the studies were devoted to those based on multiwalled carbon nanotubes (MWCNTs) mainly because of their higher availability and easier processing procedures. Moreover, high weight concentrations of MWCNTs are often required for high performance of the nanocomposites in electronic applications. Inspired by the recent drop in the SWCNT price, we have focused on fabrication of elastic nanocomposites with very low concentrations of SWCNTs to reduce the cost of nanocomposites further. In this work, we use a fast method of coagulation (antisolvent) precipitation to fabricate elastic composites based on thermoplastic polyurethane (TPU) and SWCNTs with a homogeneous distributionof SWCNTs in bulk TPU. Applicability of the approach is confirmed by extra low percolation threshold of 0.006 wt % and, as a consequence, by the state-of-the-art performance of fabricated elastic nanocomposites at very low SWCNT concentrations for strain sensing (gauge factor of 82 at 0.05 wt %) and EMI shielding (efficiency of 30 dB mm-1at 0.01 wt %).

Funding Information: The authors thank Prof. Esko I. Kauppinen and Dr. Fedor Fedorov for fruitful discussions. E.M.Kh. and T.K. acknowledge Academy of Finland (Profi 5 Project) and Finnish National Agency for Education (the EDUFI fellowship grant). D.V.K. acknowledges RSF (grant No. 20-73-10256; ANN, optimal dataset). D.V.K and A.G.N. acknowledge Council on grants of RF (grant No НШ-1330.2022.1.3). Publisher Copyright: © 2022 The Authors This work is devoted to the strategy towards the optimal development of multiparametric process of single-walled carbon nanotube (SWCNT) synthesis. Here, we examine the implementation of machine learning techniques and discuss features of the optimal dataset size and density for aerosol chemical vapor deposition method with a complex carbon source. We employ the dataset of 369 points, comprising synthesis parameters (catalyst amount, temperature, feed of carbon sources) and corresponding carbon nanotube characteristics (yield, quality, structure, optoelectrical figure of merit). Assessing the performance of six machine learning methods on the dataset, we demonstrate Artificial Neural Network to be the most suitable approach to predict the outcome of synthesis processes. We show that even a dataset of 250 points with the inhomogeneous distribution of input parameters is enough to reach an acceptable performance of the Artificial Neural Network, wherein the error is most likely to arise from experimental inaccuracy and hidden uncontrolled variables. We believe our work will contribute to the selection of an appropriate regression algorithm for the controlled carbon nanotube synthesis and further development of an autonomous synthesis system for an “on-demand” SWCNT production.

For terahertz wave applications, tunable and rapid modulation is highly required. When studied by means of optical pump–terahertz probe spectroscopy, single-walled carbon nanotube (SWCNT) thin films demonstrated ultrafast carrier recombination lifetimes with a high relative change in the signal under optical excitation, making them promising candidates for high-speed modulators. Here, combination of SWCNT thin films and stretchable substrates facilitated studies of the SWCNT mechanical properties under strain and enabled the development of a new type of an optomechanical modulator. By applying a certain strain to the SWCNT films, the effective sheet conductance and therefore modulation depth can be fine-tuned to optimize the designed modulator. Modulators exhibited a photoconductivity change of approximately 2 times of magnitude under the strain because of the structural modification in the SWCNT network. Stretching was used to control the terahertz signal with a modulation depth of around 100% without strain and 65% at a high strain operation of 40%. The sensitivity of modulators to beam polarization is also shown, which might also come in handy for the design of a stretchable polarizer. Our results give a fundamental grounding for the design of high-sensitivity stretchable devices based on SWCNT films.

Carbon nanotubes are one of the most versatile nanomaterials currently used to modify the properties of both thermoplastic and thermoset-based composites, both with and without the use of a fibrous reinforcement phase. Electrically and thermally conductive by nature, their addition to traditional fiber-reinforced polymer composites has not only heralded increased mechanical properties in terms of flexural, tensile, impact, and interlaminar properties, but also allowed imparting inherent conductivity to the final composites, allowing the creation of specialized, isotropic, anisotropic, and hierarchically graded composites with applications ranging from self-diagnostic damage detection, de-icing to energy storage and conversion. The purpose of this book chapter is to focus on the methods used to integrate carbon nanotubes, both anistropically and anisotropically via techniques that focus solely on the fibrous reinforcement phase and not the matrix, into fiber-reinforced polymer composite materials. The chapter aims to review the properties that may result from such integration of the various techniques, provide a current state of the art of the multifunctional properties, which have been achieved thus far, and outline possible future dimensions of investigation and application.

Funding Information: A.A.M. and A.G.N. thanks RFBR research project ? 20-32-90233 for support in experimental part of the work. D.V.K. thanks Russian Science Foundation grant No. 20-73-10256 for support in synthesis of aerosol SWCNT films. V.D. thanks the Russian Science Foundation (Grant No. 17-72-30006) for the support in characterization of pulse laser generation. Funding Information: A.A.M. and A.G.N. thanks RFBR research project № 20-32-90233 for support in experimental part of the work. D.V.K. thanks Russian Science Foundation grant No. 20-73-10256 for support in synthesis of aerosol SWCNT films. V.D. thanks the Russian Science Foundation (Grant No. 17-72-30006 ) for the support in characterization of pulse laser generation. Publisher Copyright: © 2021 Elsevier Ltd Single-walled carbon nanotubes (SWCNTs) are widely explored for the ultrashort pulse generation in the fiber lasers enabled by pronounced saturable absorption (SA) effect. Despite many remarkable results demonstrated in the area, degradation of the samples inside the laser cavity limits the widespread use of SWCNT-SA. In the present work, we investigate the degradation mechanism by measuring the temperature of the carbon nanotubes in an operating laser cavity in accordance with the Raman G-band position. We identify the process behind the sample degradation by comparing the burning temperature of the sample with results of thermogravimetric analysis. We apply this approach for the SWCNTs in polyvinyl alcohol polymer matrix and polymer-free SWCNT thin film and demonstrate that these samples undergo different degradation mechanism. Proposed technique provides a useful instrument for optimization of SWCNT-SA for desired ultrafast laser generation.

The architecture of transparent contacts is of utmost importance for creation of efficient flexible light-emitting devices (LEDs) and other deformable electronic devices. We successfully combined the newly synthesized transparent and durable silicone rubbers and the semiconductor materials with original fabrication methods to design LEDs and demonstrate their significant flexibility. We developed electrodes based on a composite GaP nanowire-phenylethyl-functionalized silicone rubber membrane, improved with single-walled carbon nanotube films for a hybrid poly(ethylene oxide)-metal-halide perovskite (CsPbBr3) flexible green LED. The proposed approach provides a novel platform for fabrication of flexible hybrid optoelectronic devices.

The films of single-walled carbon nanotubes (SWCNTs) are a promising material for flexible transparent electrodes, which performance depends not only on the properties of individual nanotubes but also, foremost, on bundling of individual nanotubes. This work investigates the impact of densification on optical and electronic properties of SWCNT bundles and fabricated films. Our ab initio analysis shows that the optimally densified bundles, consisting of a mixture of quasi-metallic and semiconducting SWCNTs, demonstrate quasi-metallic behavior and can be considered as an effective conducting medium. Our density functional theory calculations indicate the band curving and bandgap narrowing with the reduction of the distance between nanotubes inside bundles. Simulation results are consistent with the observed conductivity improvement and shift of the absorption peaks in SWCNT films densified in isopropyl alcohol. Therefore, not only individual nanotubes but also the bundles should be considered as building blocks for high-performance transparent conductive SWCNT-based films.

Films of single-walled carbon nanotubes are promising for various electro-optical applications. Their engineering at the nanoscale requires a robust method of the contactless, non-invasive determination of structural properties. Here we present a study that uses specular reflectometry for this purpose, namely to determine the film thickness. Analysis of the reflection coefficient of neutrons, as well as X-rays, makes it possible to obtain a normal density profile and thereby trace the effect of densification of films of single-walled carbon nanotubes by ethanol drop casting. The paper summarizes the first experience of using combined neutron and X-ray approach in relation to low-density carbon films. Further steps for the development of the technique are discussed.

We propose a simple dumbbell-shaped scheme of a Holmium-doped fiber laser incorporating a minimum number of optical elements. Mode-locking regimes were realized with the help of polymer-free single-walled carbon nanotubes (SWCNTs) synthesized using an aerosol (floating catalyst) CVD method. We show that such a laser scheme is structurally simple and more efficient than a conventional one using a ring cavity and a similar set of optical elements. In addition, we investigated the effect of SWCNT film transmittance, defined by the number of 40 nm SWCNT layers on the laser’s performance: operating regimes, stability, and self-starting. We found that three SWCNT layers with an initial transmittance of about 40% allow stable self-starting soliton mode-locking at a wavelength of 2076 nm with a single pulse energy of 0.6 nJ and a signal-to-noise ratio of more than 60 dB to be achieved.

Publisher Copyright: © 2022 by the authors. Carbon-encapsulated iron nanoparticles (Fe@C) with a mean diameter of 15 nm have been synthesized using evaporation–condensation flow–levitation method by the direct iron-carbon gas-phase reaction at high temperatures. Further, Fe@C were stabilized with bovine serum albumin (BSA) coating, and their electromagnetic properties were evaluated to test their performance in magnetic hyperthermia therapy (MHT) through a specific absorption rate (SAR). Heat generation was observed at different Fe@C concentrations (1, 2.5, and 5 mg/mL) when applied 331 kHz and 60 kA/m of an alternating magnetic field, resulting in SAR values of 437.64, 129.36, and 50.4 W/g for each concentration, respectively. Having such high SAR values at low concentrations, obtained material is ideal for use in MHT.

We propose a novel approach to enhance optoelectronic performance of single-walled carbon nanotubes (SWCNTs) for transparent conducting film applications. The method provides fine and reversible tuning of optoelectrical properties of SWCNT films over a wide range of parameters. Using imidazolium-based ionic liquid with a wide electrochemical window (BMIM-PF6), we achieved the film sheet resistance as low as 53 Ω/sq at the 90% transmittance, thereby shifting the SWCNT Fermi level up to 1.4 eV. We believe the results to promote collateral research of adjustable tuning of the electronic structure of carbon nanomaterials as promising components for future electronics, electrochromic devices, and ionotronics.

We demonstrate a simple and resource-efficient approach for rapid purification of single-walled carbon nanotube (SWCNT) films from catalyst impurities by Joule heating in a vacuum. As a result, the catalyst concentration decreases by a factor of 27 (from 17 to 1600 °C for 2 min. Moreover, the nanotube structure remains almost intact as the purified films show a high ratio of intensities of G to D bands of Raman spectrum IG/ID = 180. The technique perfectly fits for the devices based on free-standing carbon nanotube films such as protective membranes, infrared detectors, and sound generators. For purified SWCNT films, we show the signal-to-noise ratio for the bolometers to increase by a factor of 2.5 and 24% sound pressure gain for the air-coupled thermophones. The method can be easily extended to other applications, for instance, the SWCNT-based devices of limited liquid and harsh reagent tolerance like nanotube aerogels and drug delivery systems.

Funding Information: The authors thank Anton Bubis and MIPT Shared Facilities Center for the help with scanning electron microscopy. E.M.Kh. and D.V.K. acknowledge Russian Science Foundation grant No. 20-73-10256 (synthesis of SWCNTs and optical measurements). E.M.Kh. and T.K. acknowledge Academy of Finland project No. 320167 (PREIN Flagship - Aalto University). Q.Zh. and E.I.K. acknowledge Academy of Finland project No. 316572 (CNTstress). A.G.N. and A.E.G. acknowledge the Russian Science Foundation (project No. 17-19-01787 - doping of carbon nanotubes). E.I.K. acknowledge the Academy of Finland for Mobility Grant (application number 334466). A.P.Ts. acknowledges the EDUFI Fellowship (No. TM-19-11079) from the Finnish National Agency for Education and the Magnus Ehrnrooth Foundation (the Finnish Society of Sciences and Letters) for personal financial support. This work made use of the Aalto University Otanano, RAMI and Bioeconomy infrastructures. Funding Information: The authors thank Anton Bubis and MIPT Shared Facilities Center for the help with scanning electron microscopy. E.M.Kh. and D.V.K. acknowledge Russian Science Foundation grant No. 20-73-10256 (synthesis of SWCNTs and optical measurements). E.M.Kh. and T.K. acknowledge Academy of Finland project No. 320167 (PREIN Flagship - Aalto University ). Q.Zh. and E.I.K. acknowledge Academy of Finland project No. 316572 (CNTstress). A.G.N. and A.E.G. acknowledge the Russian Science Foundation (project No. 17-19-01787 - doping of carbon nanotubes). E.I.K. acknowledge the Academy of Finland for Mobility Grant (application number 334466). A.P.Ts. acknowledges the EDUFI Fellowship (No. TM-19-11079) from the Finnish National Agency for Education and the Magnus Ehrnrooth Foundation (the Finnish Society of Sciences and Letters ) for personal financial support. This work made use of the Aalto University Otanano, RAMI and Bioeconomy infrastructures. Publisher Copyright: © 2021 Elsevier Ltd This work contributes to the understanding of single-walled carbon nanotube synthesis by an aerosol CVD method using ethylene and toluene as a hybrid carbon source. We evaluated an extensive set of synthesis conditions revealing the role of ferrocene, toluene, and ethylene. We found the fundamental role of ethylene promoting nanotube nucleation and catalyst activation degree at all the concentrations studied, and enhancing nanotube growth at low ethylene content. We observed the interplay effect of toluene and ethylene concentrations on the nanotube growth rate, accompanied by the detrimental effect of toluene on catalyst activation degree. Nevertheless, toluene apparently promotes nanotube crystallinity, increasing the film conductivity while used as an individual carbon source. Adjusting the ethylene and toluene concentrations, we produced carbon nanotube-based transparent and conductive films with an equivalent sheet resistance (at 90% transmittance at 550 nm wavelength) value of 57 Ω/□ at the synthesis yield of 0.24 cm2 L−1, which is at least two times higher than the results reported earlier.

We examined the effect of hydrogen on the growth of single-walled carbon nanotubes in the aerosol (a specific case of the floating catalyst) chemical vapor deposition process using ethylene as a carbon source and ferrocene as a precursor for a Fe-based catalyst. With a comprehensive set of physical methods (UV-vis-NIR and Raman spectroscopies, transmission electron microscopy, scanning electron microscopy, differential mobility analysis, and four-probe sheet resistance measurements), we showed hydrogen to inhibit ethylene pyrolysis extending the window of synthesis parameters. Moreover, the detailed study at different temperatures allowed us to distinguish three different regimes for the hydrogen effect: pyrolysis suppression at low concentrations (I) followed by surface cleaning/activation promotion (II), and surface blockage/nanotube etching (III) at the highest concentrations. We believe that such a detailed study will help to reveal the complex role of hydrogen and contribute toward the synthesis of single-walled carbon nanotubes with detailed characteristics.

We assess bithiophene (C8H6S2) as a novel sulfur-based promotor for the growth of single-walled carbon nanotubes (SWCNTs) in the aerosol (floating catalyst) CVD method. Technologically suitable equilibrium vapor pressure and an excess of hydrocarbon residuals formed under its decomposition make bithiophene an attractive promoter for the production of carbon nanotubes in general and specifically for ferrocene-based SWCNT growth. Indeed, we detect a moderate enhancement in the carbon nanotube yield and a decrease in the equivalent sheet resistance of the films at a low bithiophene content, indicating the improvement of the product properties. Moreover, the relatively high concentrations and low temperature stability of bithiophene result in non-catalytical decomposition, leading to the formation of pyrolytic carbon deposits; the deposits appear as few-layer graphene structures. Thus, bithiophene pyrolysis opens a route for the cheap production of hierarchical composite thin films comprising carbon nanotubes and few-layer graphene, which might be of practical use for hierarchical adsorbents, protective membranes, or electrocatalysis.

Carbon nanotube films are a promising class of materials for bolometric photodetectors due to a unique combination of extremely thin (nm-sized) free-standing form factor with small thermal capacity and intriguing electronic and optical properties, thereby, ensuring high sensitivity and high speed of operation. Nevertheless, the key parameter for bolometric sensor material—the temperature coefficient of resistance (TCR)—is unacceptably low limiting the application of the carbon nanotube films. Here, we examine the plasma treatment of single-walled carbon nanotube (SWCNT) films as the effective method for the TCR enhancement. We study the effect of different plasma gases (oxygen, nitrogen, and hydrogen) on the conductivity of treated films. Also, we investigate the effect of defectiveness, length, and bundling degree of the SWCNTs on TCR. The optimized procedure allows to increase the TCR up to 1.7% K−1 by modulus at 100 K and to 0.8% K−1 at 300 K. The bolometer prototypes based on the plasma-treated SWCNT films demonstrate high sensitivity over a wide IR range (∼21 V/W), a short response time (∼1 ms), and low noise equivalent power (∼8 × 10−9 W Hz−1/2) at the temperature of 100 K.

Funding Information: The authors thank Mr. Andrei Starkov for illustrations and Mrs. Anastasiya Grebenko for assistance with sample synthesis. This work was performed using equipment of MIPT Shared Facilities Center. The authors acknowledge Vadim Khrapai and Evgeny Tikhonov (ISSP) for assistance with low temperature measurements and professor Galina Tsirlina (MSU) for fruitful discussions. The authors are also grateful to Salavat Khasanov for assistance and verification of XRD measurements. The authors thank the Helmholtz‐Zentrum Berlin für Materialien und Energie for the allocation of synchrotron radiation beamtime. Computations were done at the Finnish IT Center for Science, CSC. Russian Foundation for Basic Research grant # 19‐32‐90143 (A.K.G., A.G.N.). German Federal Ministry of Education and Research (BMBF) grant no. 05K19KER (A.A.M.). Russian Science Foundation No. 21‐19‐00226 (D.V.K., graphene synthesis). Russian Science Foundation No. 21‐72‐20050 (B.P.G., THz‐FIR spectroscopy). Ministry of Science and Higher Education of the Russian Federation within the governmental order for Boreskov Institute of Catalysis project АААА‐А21‐121011390011‐4 (A.N.S.). Partially supported by the Ministry of Science and Higher Education of the Russian Federation No. FSMG‐2021‐0005 (V.S.V., ARPES studies) and Russian Science Foundation No. 21‐72‐30026 (V.S.V, STM Studies). The work was supported by the Council on grants of the President of the Russian Federation grant number НШ‐1330.2022.1.3. Publisher Copyright: © 2022 The Authors. Advanced Science published by Wiley-VCH GmbH Following the game-changing high-pressure CO (HiPco) process that established the first facile route toward large-scale production of single-walled carbon nanotubes, CO synthesis of cm-sized graphene crystals of ultra-high purity grown during tens of minutes is proposed. The Boudouard reaction serves for the first time to produce individual monolayer structures on the surface of a metal catalyst, thereby providing a chemical vapor deposition technique free from molecular and atomic hydrogen as well as vacuum conditions. This approach facilitates inhibition of the graphene nucleation from the CO/CO2 mixture and maintains a high growth rate of graphene seeds reaching large-scale monocrystals. Unique features of the Boudouard reaction coupled with CO-driven catalyst engineering ensure not only suppression of the second layer growth but also provide a simple and reliable technique for surface cleaning. Aside from being a novel carbon source, carbon monoxide ensures peculiar modification of catalyst and in generalopens avenues for breakthrough graphene-catalyst composite production.

The architecture of transparent contacts is of utmost importance for creation of efficient flexible light-emitting devices (LEDs) and other deformable electronic devices. We successfully combined the newly synthesized transparent and durable silicone rubbers and the semiconductor materials with original fabrication methods to design LEDs and demonstrate their significant flexibility. We developed electrodes based on a composite GaP nanowire-phenylethyl-functionalized silicone rubber membrane, improved with single-walled carbon nanotube films for a hybrid poly(ethylene oxide)-metal-halide perovskite (CsPbBr

Funding Information: V.N. thanks the Russian Foundation for Basic Research (RFBR project No. 19-32-60040) for PDMS/MW membrane fabrication and optical measurements. V.F. thanks the Russian Foundation for Basic Research (RFBR project No. 19-32-60037) for the support of the MBE growth. V.N. and F.K. thank the support from the Russian Foundation for Basic Research (grant 20-32-90182) for electrical measurements. V.N., F.K., R.I. and I.M. thank the Russian Scientific Foundation (RSF project No. 20-19-00256) for chemical treatment of PDMS. V.N., V.F., A.M., F.K. and K.S. thank the Ministry of Science and Higher Education of the Russian Federation (FSRM-2020-0005) for the general support. E.M. thanks the Basic Research Program at the National Research University Higher School of Economics (HSE University) in 2021 for optical measurements. N.A.-M. and M.T. thank ITN Marie Curie project INDEED (grant No. 722176) for GaPAs NW/PDMS membrane investigation. This work received financial support from Partenariats Hubert Curien Kolmogorov project No. 43784UJ and Indo French Centre for the Promotion of Advanced Research (CEFIPRA) Project No. 6008-1. A.G.N. acknowledges the Russian Scientific Foundation (RSF project No. 21-72-20050) for synthesis of SWCNTs. Funding Information: Funding: V.N. thanks the Russian Foundation for Basic Research (RFBR project No. 19-32-60040) for PDMS/MW membrane fabrication and optical measurements. V.F. thanks the Russian Foundation for Basic Research (RFBR project No. 19-32-60037) for the support of the MBE growth. V.N. and F.K. thank the support from the Russian Foundation for Basic Research (grant 20-32-90182) for electrical measurements. V.N., F.K., R.I. and I.M. thank the Russian Scientific Foundation (RSF project No. 20-19-00256) for chemical treatment of PDMS. V.N., V.F., A.M., F.K. and K.S. thank the Ministry of Science and Higher Education of the Russian Federation (FSRM-2020-0005) for the general support. E.M. thanks the Basic Research Program at the National Research University HigherSchool of Economics (HSE University) in 2021 for optical measurements. N.A.-M. and M.T. thank ITN Marie Curie project INDEED (grant No. 722176) for GaPAs NW/PDMS membrane investigation. This work received financial support from Partenariats Hubert Curien Kolmogorov project No. 43784UJ and Indo French Centre for the Promotion of Advanced Research (CEFIPRA) Project No. 6008-1. A.G.N. acknowledges the Russian Scientific Foundation (RSF project No. 21-72-20050) for synthesis of SWCNTs. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. We demonstrate flexible red light-emitting diodes based on axial GaPAs/GaP heterostruc-tured nanowires embedded in polydimethylsiloxane membranes with transparent electrodes involv-ing single-walled carbon nanotubes. The GaPAs/GaP axial nanowire arrays were grown by molecular beam epitaxy, encapsulated into a polydimethylsiloxane film, and then released from the growth substrate. The fabricated free-standing membrane of light-emitting diodes with contacts of single-walled carbon nanotube films has the main electroluminescence line at 670 nm. Membrane-based light-emitting diodes (LEDs) were compared with GaPAs/GaP NW array LED devices processed directly on Si growth substrate revealing similar electroluminescence properties. Demonstrated membrane-based red LEDs are opening an avenue for flexible full color inorganic devices.

Rubber materials are the key components of flexible optoelectronic devices, especially for the light-emitting diodes based on arrays of inorganic nanowires (NWs). This paper reports on polydimethylsiloxane-graft-polystyrene (PDMS-St) as a new flexible substrate of GaP NW array structures. The NWs were encapsulated by the newly introduced G-coating method to substitute the inefficient mainstream spin-coating. To further exploit the flexibility and the stretchability of the NW/PDMS-St structures, the ferrocenyl-containing polymethylhydrosiloxane was synthesized and successfully used as an electrode for the NWs. In order to make an alternative highly efficient transparent electrode, a new application of conductive single-walled carbon nanotubes was demonstrated. The novel materials and methods demonstrated unsurpassed mechanical stability of the fabricated flexible electronic devices.

We propose to use artificial neural networks to process the experimental data and to predict the performance of the aerosol CVD synthesis of single-walled carbon nanotubes based on Boudouard reaction. We employ five key input parameters of the growth (pressures of CO, CO2 and ferrocene as well as the residence time and the growth temperature) to control the performance of produced nanotube films (yield, mean and standard deviation of the diameter distribution, and defectiveness). The prediction errors were found to be comparable with the corresponding experimental errors. We believe the proposed approach is of great interest for the synthesis of nanocarbons with tailored characteristics.

We have designed and built an exhaust-free spark discharge generator for robust aerosol CVD synthesis of single-walled carbon nanotubes. The systematic study has shown the generator to provide a facile and repeatable route to precisely control the size of the catalyst particle and, therefore, carbon nanotube growth. Using a comprehensive set of methods (the analysis of differential mobility of the aerosol particles, optical spectroscopy, scanning and transmission electron microscopy, Raman spectroscopy, and atomic force microscopy) we have revealed the relation between the defectiveness, length, diameter distribution of carbon nanotubes and specific features of a generator such as electrode characteristics (breakdown voltage, composition, and current) as well as the nature of the surrounding media (carrier gas nature, flow rate). The design used has resulted in separation of the nanoparticle formation and carbon nanotube nucleation processes. This provides a mutual independence of the growth parameters and the diameter distribution of the single-walled carbon nanotubes enhancing the scalability of the process. For instance, the breakdown voltage has been shown to have nearly zero effect on diameter and length distribution of carbon nanotubes produced while strictly governing the yield. We focus here on producing specifically short carbon nanotubes (l < 500 nm) of pronounced defectiveness for drug delivery and transistor applications.

The influence of the surface modification of multi-walled carbon nanotubes (MWCNT) with nitrogen-containing compounds on the performance of 40 wt% Pt/MWCNT catalysts in the oxygen electroreduction reaction (ORR) was investigated using a rotating disk electrode (RDE) at 10–35 °C in 0.1 M HClO4 as electrolyte in electrochemical cell, and in a hydrogen–oxygen polymer electrolyte membrane fuel cell (PEMFC) at 82 °C. The catalysts were characterized by low-temperature nitrogen adsorption, XPS, TEM, gas-phase CO titration, electrooxidation of the adsorbed CO monolayer, and cyclic voltammetry. It was shown that the modification of MWCNT with melamine–formaldehyde resin leads to the surface nitrogen concentration up to 8.3 at.% (CNT-MF sample). The 40 wt% Pt/CNT-MF catalyst with 0.1 mg cm−2 Pt loading on the cathode showed a good performance in PEMFC (~ 0.61 W cm−2) and a high utilization ratio (0.84) of Pt in membrane electrode assembly as compared to Pt/CNT catalyst (~ 0.37 W cm−2 and utilization of 0.29). The higher power density of nitrogen-modified catalysts was ascribed to a higher utilization of Pt in the electrode layer.

Interest in compact and stable sources of ultrashort pulsed radiation in the mid-IR range is due to a number of possible applications, e.g. for spectroscopy, perspective communications, materials processing, biodiagnostics, and etc. One of the promising active medium for such sources are holmium-doped (Ho 3+ ) fibers due to their broad gain spectrum of 2–2.2 μm. In recent years, Ho 3+ -doped mode-locked fiber lasers have been intensively studied [1] – [3] . However, practically each of the presented laser schemes contains elements that can be damaged by laser radiation (isolators, polarizers, beam splitters, circulators, etc.). For the further use of ultrashort pulsed lasers in complex or hybrid systems as a seed source, the laser scheme should be simplified and free of elements that can fail and affect laser generation. Therefore, it is of interest to study a fiber laser with a simple dumbbell-shaped cavity [4] , [5] . Here, we focused on saturable absorber optimization to obtain a self-starting mode-locked Ho 3+ -doped fiber laser with a dumbbell-shaped cavity.

Funding Information: The authors J.E., C.D. and A.K. would like to thank Jean Dussaud for his work on the MOVPE setup. V.N. would like to thank Maria Baeva for her assistance with the stretchable LED transparency measurements.J.E., C.D. and A.K. thank French National Labex GaNeX (ANR-11-LABX-0014) for MW synthesis and CL measurements. V.N. thanks the Russian Foundation for Basic Research (RFBR project no. 19-32-60040) for PDMS/MW membrane fabrication and optical measurements. I.S.M., V.N., F.M.K. thank the support from the Russian Science Foundation (grant 20-19-00256) for PDMS synthesis and electrical measurements. D.K. and A.G.N. thank Russian Foundation of Basic Research project no. 20-03-00804 for the synthesis of carbon nanotubes. F.E.K. thanks the support from the Russian Science Foundation (grant 19-79-00313) for the LED array encapsulation and membrane transfer. I.S.M., F.M.K., V.N., V.A.M., S.M., A.A.V., A.V.U., and D.A.M. thank the Ministry of Science and Higher Education of the Russian Federation (FSRM-2020-0005) for the general support. N.A. and M.T. acknowledge the financial support from the ITN Marie Curie project INDEED (grant no. 722176), by the Indo-French Centre for the Promotion of Advanced Research (IFCPAR/CEFIPRA project no. 6008-1) for MW/PDMS membrane processing and characterization. Funding Information: Funding: J.E., C.D. and A.K. thank French National Labex GaNeX (ANR-11-LABX-0014) for MW synthesis and CL measurements. V.N. thanks the Russian Foundation for Basic Research (RFBR project no. 19-32-60040) for PDMS/MW membrane fabrication and optical measurements. I.S.M., V.N., F.M.K. thank the support from the Russian Science Foundation (grant 20-19-00256) for PDMS synthesis and electrical measurements. D.K. and A.G.N. thank Russian Foundation of Basic Research project no. 20-03-00804 for the synthesis of carbon nanotubes. F.E.K. thanks the support from the Russian Science Foundation (grant 19-79-00313) for the LED array encapsulation and membrane transfer. I.S.M., F.M.K., V.N., V.A.M., S.M., A.A.V., A.V.U., and D.A.M. thank the Ministry of Science and Higher Education of the Russian Federation (FSRM-2020-0005) for the general support. N.A. and M.T. acknowledge the financial support from the ITN Marie Curie project INDEED (grant no. 722176), by the Indo-French Centre for the Promotion of Advanced Research (IFCPAR/CEFIPRA project no. 6008-1) for MW/PDMS membrane processing and characterization. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. We propose and demonstrate both flexible and stretchable blue light-emitting diodes based on core/shell InGaN/GaN quantum well microwires embedded in polydimethylsiloxane membranes with strain-insensitive transparent electrodes involving single-walled carbon nanotubes. InGaN/GaN core-shell microwires were grown by metal-organic vapor phase epitaxy, encapsulated into a polydimethylsiloxane film, and then released from the growth substrate. The fabricated free-standing membrane of light-emitting diodes with contacts of single-walled carbon nanotube films can stand up to 20% stretching while maintaining efficient operation. Membrane-based LEDs show less than 15% degradation of electroluminescence intensity after 20 cycles of stretching thus opening an avenue for highly deformable inorganic devices.

Determination of food doneness remains a challenge for automation in the cooking industry. The complex physicochemical processes that occur during cooking require a combination of several methods for their control. Herein, we utilized an electronic nose and computer vision to check the cooking state of grilled chicken. Thermogravimetry, differential mobility analysis, and mass spectrometry were employed to deepen the fundamental insights towards the grilling process. The results indicated that an electronic nose could distinguish the odor profile of the grilled chicken, whereas computer vision could identify discoloration of the chicken. The integration of these two methods yields greater selectivity towards the qualitative determination of chicken doneness. The odor profile is matched with detected water loss, and the release of aromatic and sulfur-containing compounds during cooking. This work demonstrates the practicability of the developed technique, which we compared with a sensory evaluation, for betterdeconvolution of food state during cooking.

The development of THz technology and communication systems is creating demand for devices that can modulate THz beams rapidly. Here we report the design and characterisation of high-performance, broadband THz modulators based on the photo-induced transparency of carbon nanotube films. Rather than operating in the standard modulation mode, where optical excitation lowers transmission, this new class of modulators exhibits an inverted modulation mode with an enhanced transmission. Under femtosecond pulsed illumination, modulation depths reaching + 80 % were obtained simultaneously with modulation speeds of 340 GHz. The influence of the film thickness on the insertion loss, modulation speed and modulation depth was explored over a frequency range from 400 GHz to 2.6 THz. The excellent modulation depth and high modulation speed demonstrated the significant potential of carbon nanotube thin films for ultrafast THz modulators.

We demonstrate a mode-locked holmium-doped fiber laser with a dumbbell-shaped cavity. Unlike the ring or linear schemes, the dumbbell-shaped design is simple and doesn't contain expensive, and subject to radiation damage optical components.

Dual-wavelength ultra-short pulses generation in the dumbbell-shaped thulium fiber laser was demonstrated. The mode-locking regime was achieved by using single-walled carbon nanotubes in the laser cavity. Output power was up to 6 mW and the main repetition rate was around 5.3 MHz.

In this work, we evaluate the effect of ferrocene delivery in the reactor on the growth of single-walled carbon nanotubes (SWCNTs) in an aerosol CVD utilizing carbon monoxide as a feedstock. For this purpose, we assess the reactor output parameters varying a gas flow rate through a ferrocene vapor injector in the hot zone with other conditions (temperature, total flow rate, and reactant concentration) being fixed. Our experimental results reveal the adjustment of the ferrocene injection strategy (injector flow rate) to cause a 9-fold improvement in the synthesis yield while preserving the SWCNT properties. We show the catalyst injection optimization to enhance catalyst activation degree as a result of a streamline catalyst delivery, preventing particle over-growth; the experimental data are supported by the computational fluid dynamics. We believe our work to highlight the importance of appropriate aerosol CVD reactor engineering and to facilitate the optimization of reactor productivity, which is one of the fundamental milestones towards SWCNT-based technology.

We investigate a complex relationship between structural parameters of single-walled carbon nanotubes (namely, mean length, diameter, and defectiveness) and optoelectrical properties (equivalent sheet resistance) of thin films composed of the nanotubes. We obtained a systematic dataset describing the influence of CO2 concentration and growth temperature. On the basis of the experimental results, we prove the high Raman peak ratio (IG/ID), length, and diameter of the nanotubes to decrease the equivalent sheet resistance of the nanotube-based film. The approach employed highlights the change in the nanotube growth mechanism at the temperature coinciding with the phase transition between α-Fe and γ-Fe catalyst phases. We believe this work to be of high interest for researchers working not only in the field of transparent and conductive films based on nanocarbons, but also for those who reveals the fundamentals of the nanotube growth mechanism.

Here we have studied the kinetics of the ethylene non-catalytic decomposition on the surface of multi-walled carbon nanotubes (MWCNTs) leading to the formation of lateral carbon deposits (LCD). Despite the comprehensive data on the gas-phase pyrolysis and a clear presence of surface impurities formed of carbon deposits, this process has not gained any proper attention. Within the temperature range studied (650–750 °C), we have found the rate of the reaction to be proportional to the MWCNT surface area and ethylene partial pressure. The activation energy of carbon deposition is close to that for the collision of two ethylene molecules to form C2H5· and C2H3· radicals. Based on the data obtained, we have proposed the radical mechanism of the formation of the deposits. High-resolution TEM, synchrotron radiation XRD, Raman spectroscopy, differential thermal analysis, temperature dependence of conductivity, and surface area measurements were used to characterize the structure and properties of the carbon-carbon composite produced. We have shown the deposition of lateral carbon to be a soft non-destructive technique for MWCNT surface functionalization allowing one to tune the properties of 3D-structured nanotube materials (e.g. arrays or aerogels). As an example, the LCD coating gradually changes the conductivity mechanism to 3D variable range hopping.

International audience; 59 Co NMR a b s t r a c t CoFe 2 /CaO catalysts for multi-walled carbon nanotubes (MWCNT) were characterized during the activation period (T = 670°C; C 2 H 4 /Ar = 1:1, 400 sccm) by internal field 59 Co nuclear magnetic resonance. During this induction period, although C 2 H 4 is already reacting, the MWCNT yield remains negligible. The NMR spectra of the catalysts revealed the occurrence of several structural and magnetic species. They were not detectable by conventional X-ray diffraction but the heterogeneity of the metal particles was corroborated by high-resolution transmission electronic microscopy coupled with energy dispersive X-ray spectroscopy. Two samples quenched at different activation time contained, beside non-reacted pure metal Co particles, strong and weak ferromagnetic alloys. During activation, the pure Co metal content dropped and an increase of the ordering of the cobalt-iron alloy in the catalyst was evidenced thus revealing a multistage activation mechanism for the reaction. We propose this ordering process during the induction period to be an intermediate step between the strong ferromagnetic Co rich alloy and the weak ferromagnetic Fe rich one and that it favors the onset of MWCNTs growth.

We demonstrate a short cavity passively mode-locked composite erbium-doped fiber laser with saturable absorber based on aerosol-synthesized single-walled carbon nanotubes. Optical pulses had a duration of 973 fs while an average output power – 6 mW. Using a shortened laser cavity, a stable soliton generation with a pulse repetition rate of 150 MHz at the output of the all-fiber linear cavity was obtained.

We examine an effect of residence time on the growth of single-walled carbon nanotubes (SWCNTs) in an aerosol (floating catalyst) chemical vapor deposition (CVD) process using CO as a carbon source and ferrocene as a catalyst precursor. The key feature of aerosol CVD reactors, namely stabilization of fine nanoparticles by an extreme dilution, limits the method for catalyst evolution studies. We show an approach to examine the role of the residence time while maintaining all the processes preceding the nanotube growth (catalyst formation, nanotube nucleation). Using the diameter distribution of nanotubes as a fingerprint of the SWCNT nucleation stage, we have proven the latter to be unaffected by changes in the residence time. Using SEM observations, we have revealed a quite intuitive but inspiring correlation between the carbon nanotube length and residence time. We have also found a decrease in the SWCNT yield caused by the drop in the aerosol concentration, which could be attributed to the gas-phase losses as well as the shift in the catalyst activation degree. Nevertheless, the trends observed allowed us to reach a tenfold decrease in an equivalent sheet resistance (sheet resistance of a film with 90% transmittance at 550 nm) by a threefold increase in the residence time at optimal CO2 concentration. SWCNT films with the equivalent sheet resistance as low as 245 Ω/□ and 51 Ω/□ (for pristine and doped carbon nanotubes, correspondingly) ensure the promising future of the proposed strategy for optimization of both aerosol CVD reactors and SWCNT-based films for optoelectronic applications.

In the present study, we have developed a mathematic model describing quasi-continuous catalytic synthesis of multi-walled carbon nanotubes (MWCNTs) in a fluidized bed (FB) reactor. The special attention has been paid to the effects related to heat release or absorption during MWCNT synthesis. The heat of the reaction for MWCNT growth has been shown to significantly affect the thermal field in the reactor with the diameter as low as 6 cm. We attribute this to the extremely low thermal conductivity of aerogel-like MWCNT agglomerates (0.5–0.7 W/(m·K)), the basic units of the fluidized bed. According to the proposed model, the overheating up to 60 degrees takes place in the reactor with the diameter of D = 18 cm, the wall temperature of 943 K, and blown by 1:1 C2H4/Ar mixture. We have observed major changes caused by overheating: the activity of the catalyst and morphological properties of the produced MWCNTs (outer diameter, the structure of the walls, and fraction of impurities). The role of these thermal effects rises dramatically with increasing the reactor size and should be taken into account when designing reactors for large-scale production of MWCNTs.

A macroporous carbon aerogel (MCA) was produced by in situ synthesis of multi-walled carbon nanotubes (CNTs) via catalytic high-temperature decomposition of ethylene over the supported Fe:Co catalyst. A three-dimensional framework of ball-shaped MCA granules was formed by chaotic interlacing of growing CNTs and mechanical strength of the granules was high enough for their promising application in heterogeneous processes, in particular, bioconversion of fatty acids. The macroporous carbon aerogel was investigated as a novel support for adsorptive immobilization of an enzyme—Thermomyces lanuginosus lipase, followed by preparation of the lipase-active heterogeneous biocatalysts. It was found that the efficient and tight adsorption of the lipase on MCA occurred due to hydrophobic interactions. The amount of the lipase adsorbed in one dense adsorptive layer was equal to 110 mg per 1 g of the carbon aerogel. The lipase adsorbed in the 1st adsorptive layer possessed the maximum activity, 700–800 U/mg. The lipase-active heterogeneous biocatalysts were studied in the periodic processes of hydrolysis of emulsified triglycerides (tributyrin), interesterification of vegetable oil with ethyl acetate, and esterification of fatty acids (butyric C4:0, capric C10:0, and stearic C18:0) with isopentanol. It was found that T. lanuginosus lipase lost significantly its enzymatic activity during adsorption on the carbon aerogel; possible causes of the negative effect of such immobilization were discussed. The specific activity of the adsorbed lipase, as well as activity and stability of the biocatalysts depended foremost on the type of the reaction performed. The maximum activities of the biocatalysts were determined to be approximately 75·103 and 2.5 U/g in tributyrin hydrolysis (aqueous media) and esterification of fatty acid (non-aqueous media), respectively. Stability of the biocatalysts was very high in the esterification reaction due to accumulation of essential water inside MCA. The lipase-active biocatalysts carried out the synthesis of isopentyl caprinate in organic solvents (hexane + diethyl ether) for several 100 h at 40 °C.

A machine learning technique, namely, support vector regression, is implemented to enhance single-walled carbon nanotube (SWCNT) thin-film performance for transparent and conducting applications. We collected a comprehensive data set describing the influence of synthesis parameters (temperature and CO2 concentration) on the equivalent sheet resistance (at 90% transmittance in the visible light range) for SWCNT films obtained by a semi-industrial aerosol (floating-catalyst) CVD with CO as a carbon source and ferrocene as a catalyst precursor. The predictive model trained on the data set shows principal applicability of the method for refining synthesis conditions toward the advanced optoelectronic performance of multiparameter processes such as nanotube growth. Further doping of the improved carbon nanotube films with HAuCl4 results in the equivalent sheet resistance of 39 Ω/□-one of the lowest values achieved so far for SWCNT films.

We propose a novel, scalable, and simple method for aerosol doping of single-walled carbon nanotube (SWCNT) films. This method is based on aerosolization of a dopant solution (HAuCl4 in ethanol) and time-controlled deposition of uniform aerosol particles on the nanotube film surface. The approach developed allows fine-tuning of the SWCNT work function in the range of 4.45 eV (for pristine nanotubes) to 5.46 eV, controllably varying the sheet resistance of the films from 79 to 3.2 Ω/□ for the SWCNT films with 50% transmittance (at 550 nm). This opens a new avenue for traditional and flexible optoelectronics: both to replace existing indium-tin oxide electrodes and to develop novel applications of the highly conductive transparent films.

Effect of the catalyst composition on the structure of nanotubes layers obtained on the surface of carbon nanofibers was studied. We found the preliminary functionalization of the surface of carbon fibers to affect the coating uniformity and the thickness of synthesized nanotube layer. We determined the optimal surface concentration of the catalyst (Fe–Co) which provides uniform layer of nanotubes on the surface of carbon fibers. The effect of modification of the surface of carbon fibers with multi-walled carbon nanotubes on the mechanical properties of carbon fiber–epoxy resin composites was examined. The modification of the carbon fibers with multi-walled carbon nanotubes were shown to increase the flexural modulus and the flexural strength.

The synthesis conditions of multi-walled carbon nanotubes (MWCNTs) indirectly determine their application potential through the decisive role in the characteristics of individual tubes: diameter distribution, structure and defectiveness of graphene walls, the amount of metal impurities and amorphous carbon. In the present work, we have studied the influence of the catalyst composition and synthesis conditions on the diameter distribution and the structure of nanotube walls. We have observed the influence of the particle size for MWCNT synthesis (i.e. size effect) on catalytic activity by ex situ and in situ techniques: in situ X-ray diffraction on synchrotron radiation (SRXRD), gas chromatography, and ex situ transmission electron microscopy. The data obtained by in situ SRXRD are in agreement with the results collected using laboratory tubular fix-bed catalytic reactor allowing thereby extending the applicability of the approach. For the first time we have shown the increase of the fraction of graphene walls in the total MWCNT diameter with time.

We report a development of recently designed apparatus equipped with a spark discharge generator of catalytic nanoparticles for robust aerosol CVD synthesis of single-walled carbon nanotubes. We achieve a profound control over the diameter distribution and the defectiveness of carbon nanotubes produced. By providing a justified comparison of the apparatus with the most abundant aerosol CVD reactor utilizing ferrocene as a catalyst precursor, we reveal the role of the activation procedure: while spark-discharge generator provides aerosol of nanoparticles (ex situ route), the ferrocene vapor decomposes in the nanotube growth zone providing an in situ formation of the catalyst. With other parameters being equal, we reveal the differences in the nanotube growth (diameter and length distribution, yield, defectiveness) employing a comprehensive set of methods (the analysis of differential mobility of the aerosol particles, optical spectroscopy, scanning and transmission electron microscopy, Raman spectroscopy, and atomic force microscopy). We show the ex situ activation in the spark discharge reactor to provide a lower utilization degree of the nanoparticles due to over-coagulation. However, the same method provides an independence of the key performance parameters of the nanotubes opening a room for scaling the apparatus.