High-Quality Graphene Using Boudouard Reaction

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 general opens avenues for breakthrough graphene-catalyst composite production

Gentle Patterning Approaches toward Compatibility with Bio-Organic Materials and Their Environmental Aspects

Funding Information: A.K.G. and K.A.M. acknowledge funding from Russian Science Foundation under Grant No. 19‐73‐10154. A.G.N. acknowledges Russian Foundation of Basic Research project no. 20‐03‐00804. The authors acknowledge the Ministry of Science and Higher Education of the Russian Federation (Project No. FZSR‐2020‐0007 in the framework of the State Assignment No. 075‐03‐2020‐097/1). This work is supported by the Council on grants of the President of the Russian Federation grant number НШ‐1330.2022.1.3. MIPT Center for Photonics and 2D Materials is supported by the Ministry of Science and Higher Education of the Russian Federation (No. FSMG‐2021‐0005). Publisher Copyright: © 2022 The Authors. Small published by Wiley-VCH GmbH.Advances in material science, bioelectronic, and implantable medicine combined with recent requests for eco-friendly materials and technologies inevitably formulate new challenges for nano- and micropatterning techniques. Overall, the importance of creating micro- and nanostructures is motivated by a large manifold of fundamental and applied properties accessible only at the nanoscale. Lithography is a crucial family of fabrication methods to create prototypes and produce devices on an industrial scale. The pure trend in the miniaturization of critical electronic semiconducting components has been recently enhanced by implementing bio-organic systems in electronics. So far, significant efforts have been made to find novel lithographic approaches and develop old ones to reach compatibility with delicate bio-organic systems and minimize the impact on the environment. Herein, such delicate materials and sophisticated patterning techniques are briefly reviewed.Peer reviewe

Evaluation of elastic properties and conductivity of chitosan acetate films in ammonia and water vapors using acoustic resonators

Novel bio-materials, like chitosan and its derivatives, appeal to finding a new niche in room temperature gas sensors, demonstrating not only a chemoresistive response, but also changes in mechanical impedance due to vapor adsorption. We determined the coefficients of elasticity and viscosity of chitosan acetate films in air, ammonia, and water vapors by acoustic spectroscopy. The measurements were carried out while using a resonator with a longitudinal electric field at the different concentrations of ammonia (100–1600 ppm) and air humidity (20–60%). It was established that, in the presence of ammonia, the longitudinal and shear elastic modules significantly decreased, whereas, in water vapor, they changed slightly. At that, the viscosity of the films increased greatly upon exposure to both vapors. We found that the film’s conductivity increased by two and one orders of magnitude, respectively, in ammonia and water vapors. The effect of analyzed vapors on the resonance properties of a piezoelectric resonatorwith a lateral electric field that was loaded by a chitosan film on its free side was also experimentally studied. In these vapors, the parallel resonance frequency and maximum value of the real part of the electrical impedance decreased, especially in ammonia. The results of a theoretical analysis of the resonance properties of such a sensor in the presence of vapors turned out to be in a good agreement with the experimental data. It has been also found that with a growth in the concentration of the studied vapors, a decrease in the elastic constants, and an increase in the viscosity factor and conductivity lead to reducing the parallel resonance frequency and the maximum value of the real part of the electric impedance of the piezoelectric resonator with a lateral electric field that was loaded with a chitosan film. This leads to an increase in the sensitivity of such a sensor during exposure to these gas vapors.Peer reviewe

A spark discharge generator for scalable aerosol CVD synthesis of single-walled carbon nanotubes 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.Peer reviewe

Fine-tuning of spark-discharge aerosol CVD reactor for single-walled carbon nanotube growth

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.Peer reviewe

High-Quality Graphene Using Boudouard Reaction

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 general opens avenues for breakthrough graphene-catalyst composite production

Quasi-2D Co3O4 nanoflakes as an efficient gas sensor

Here, we study quasi-two-dimensional crystals of Co3O4 grown by electrochemical synthesis on Pt electrodes with a nanoflake morphology to serve as a gas sensor. When synthesizing in aqueous electrolytes under applied electrical bias, the material follows a self-hierarchical architecture to primarily appear as the hexagonal nanoflakes α-Co(OH)2. After heating up to 300 °C in air, the as-synthesized material transforms to Co3O4, preserving the original hierarchical morphology. The Co3O4 nanoflakes have been found to have remarkable chemiresistive response when exposed to various kinds of alcohol vapors, at low ppm concentrations in a mixture with air, over a wide range of temperatures up to 300 °C with a detection limit down to the ppb range with direct dependence on the molecule weight of the alcohol. We explain the observed features of the gas response of the Co3O4 nanoflakes by a shift in the electron density under the chemisorption of VOCs, verified by DFT calculations.Peer reviewe

High-Quality Graphene Using Boudouard Reaction

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 GmbHFollowing 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.Peer reviewe