Nanomaterials

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2 pages, 167 KiB

Open AccessEditorial

Synthesis, Development and Characterization of Nanotubes

by Marius Dobromir

Nanomaterials 2023, 13(11), 1762; https://doi.org/10.3390/nano13111762 - 30 May 2023

Viewed by 765

Abstract

In recent decades, the great demand for device miniaturization has attracted the attention of researchers focused on the growth, modification, properties, and applications of one-dimensional nanostructures, such as nanotubes [...] Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes)

Research

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12 pages, 1940 KiB

Open AccessArticle

Electric Properties of Multiwalled Carbon Nanotubes Dispersed in Liquid Crystals and Their Influence on Freedericksz Transitions

by Emil Petrescu and Cristina Cirtoaje

Nanomaterials 2022, 12(7), 1119; https://doi.org/10.3390/nano12071119 - 28 Mar 2022

Cited by 7 | Viewed by 1834

Abstract

Liquid crystal composites with multiwalled carbon nanotubes present dielectric properties considerably different from those of pure liquid crystal (LC). Using a proper dispersion of nanotubes in the LC-sample and a theoretical model in agreement with the experimental configuration, the dielectric permittivities of multiwalled [...] Read more.

Liquid crystal composites with multiwalled carbon nanotubes present dielectric properties considerably different from those of pure liquid crystal (LC). Using a proper dispersion of nanotubes in the LC-sample and a theoretical model in agreement with the experimental configuration, the dielectric permittivities of multiwalled carbon nanotubes are calculated. The influence of dielectric properties on the Freedericksz transition threshold is discussed. Theoretical values for dielectric permittivities of multiwalled carbon nanotubes are calculated for different temperatures Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes)

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12 pages, 26162 KiB

Open AccessArticle

Carbon and Neon Ion Bombardment Induced Smoothing and Surface Relaxation of Titania Nanotubes

by Astrid Kupferer, Michael Mensing, Jan Lehnert, Stephan Mändl and Stefan G. Mayr

Nanomaterials 2021, 11(9), 2458; https://doi.org/10.3390/nano11092458 - 21 Sep 2021

Cited by 3 | Viewed by 2513

Abstract

Titania nanotube arrays with their enormous surface area are the subject of much attention in diverse fields of research. In the present work, we show that not only 60 keV and 150 keV ion bombardment of amorphous titania nanotube arrays yields defect creation [...] Read more.

Titania nanotube arrays with their enormous surface area are the subject of much attention in diverse fields of research. In the present work, we show that not only 60 keV and 150 keV ion bombardment of amorphous titania nanotube arrays yields defect creation within the tube walls, but it also changes the surface morphology: the surface relaxes and smoothens in accordance with a curvature-driven surface material’s transport mechanism, which is mediated by radiation-induced viscous flow or radiation-enhanced surface diffusion, while the nanotubes act as additional sinks for the particle surface currents. These effects occur independently of the ion species: both carbon and neon ion bombardments result in comparable surface relaxation responses initiated by an ion energy of 60 keV at a fluence of 1 × 10

^{16}

ions/cm

^{2}

. Using atomic force microscopy and contact angle measurements, we thoroughly study the relaxation effects on the surface topography and surface free energy, respectively. Moreover, surface relaxation is accompanied by further amorphization in surface-near regions and a reduction in the mass density, as demonstrated by Raman spectroscopy and X-ray reflectivity. Since ion bombardment can be performed on global and local scales, it constitutes a versatile tool to achieve well-defined and tunable topographies and distinct surface characteristics. Hence, different types of nanotube arrays can be modified for various applications. Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes)

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21 pages, 3662 KiB

Open AccessEditor’s ChoiceArticle

Electrically Conductive Networks from Hybrids of Carbon Nanotubes and Graphene Created by Laser Radiation

by Alexander Yu. Gerasimenko, Artem V. Kuksin, Yury P. Shaman, Evgeny P. Kitsyuk, Yulia O. Fedorova, Artem V. Sysa, Alexander A. Pavlov and Olga E. Glukhova

Nanomaterials 2021, 11(8), 1875; https://doi.org/10.3390/nano11081875 - 22 Jul 2021

Cited by 20 | Viewed by 4253

Abstract

A technology for the formation of electrically conductive nanostructures from single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and their hybrids with reduced graphene oxide (rGO) on Si substrate has been developed. Under the action of single pulses of laser irradiation, nanowelding of [...] Read more.

A technology for the formation of electrically conductive nanostructures from single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and their hybrids with reduced graphene oxide (rGO) on Si substrate has been developed. Under the action of single pulses of laser irradiation, nanowelding of SWCNT and MWCNT nanotubes with graphene sheets was obtained. Dependences of electromagnetic wave absorption by films of short and long nanotubes with subnanometer and nanometer diameters on wavelength are calculated. It was determined from dependences that absorption maxima of various types of nanotubes are in the wavelength region of about 266 nm. It was found that contact between nanotube and graphene was formed in time up to 400 fs. Formation of networks of SWCNT/MWCNT and their hybrids with rGO at threshold energy densities of 0.3/0.5 J/cm² is shown. With an increase in energy density above the threshold value, formation of amorphous carbon nanoinclusions on the surface of nanotubes was demonstrated. For all films, except the MWCNT film, an increase in defectiveness after laser irradiation was obtained, which is associated with appearance of C–C bonds with neighboring nanotubes or graphene sheets. CNTs played the role of bridges connecting graphene sheets. Laser-synthesized hybrid nanostructures demonstrated the highest hardness compared to pure nanotubes. Maximum hardness (52.7 GPa) was obtained for MWCNT/rGO topology. Regularity of an increase in electrical conductivity of nanostructures after laser irradiation has been established for films made of all nanomaterials. Hybrid structures of nanotubes and graphene sheets have the highest electrical conductivity compared to networks of pure nanotubes. Maximum electrical conductivity was obtained for MWCNT/rGO hybrid structure (~22.6 kS/m). Networks of nanotubes and CNT/rGO hybrids can be used to form strong electrically conductive interconnections in nanoelectronics, as well as to create components for flexible electronics and bioelectronics, including intelligent wearable devices (IWDs). Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes)

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11 pages, 2603 KiB

Open AccessArticle

A New Method for Dispersing Pristine Carbon Nanotubes Using Regularly Arranged S-Layer Proteins

by Andreas Breitwieser, Uwe B. Sleytr and Dietmar Pum

Nanomaterials 2021, 11(5), 1346; https://doi.org/10.3390/nano11051346 - 20 May 2021

Cited by 10 | Viewed by 2479

Abstract

Homogeneous and stable dispersions of functionalized carbon nanotubes (CNTs) in aqueous solutions are imperative for a wide range of applications, especially in life and medical sciences. Various covalent and non-covalent approaches were published to separate the bundles into individual tubes. In this context, [...] Read more.

Homogeneous and stable dispersions of functionalized carbon nanotubes (CNTs) in aqueous solutions are imperative for a wide range of applications, especially in life and medical sciences. Various covalent and non-covalent approaches were published to separate the bundles into individual tubes. In this context, this work demonstrates the non-covalent modification and dispersion of pristine multi-walled carbon nanotubes (MWNTs) using two S-layer proteins, namely, SbpA from Lysinibacillus sphaericus CCM2177 and SbsB from Geobacillus stearothermophilus PV72/p2. Both the S-layer proteins coated the MWNTs completely. Furthermore, it was shown that SbpA can form caps at the ends of MWNTs. Reassembly experiments involving a mixture of both S-layer proteins in the same solution showed that the MWNTs were primarily coated with SbsB, whereas SbpA formed self-assembled layers. The dispersibility of the pristine nanotubes coated with SbpA was determined by zeta potential measurements (−24.4 +/− 0.6 mV, pH = 7). Finally, the SbpA-coated MWNTs were silicified with tetramethoxysilane (TMOS) using a mild biogenic approach. As expected, the thickness of the silica layer could be controlled by the reaction time and was 6.3 +/− 1.25 nm after 5 min and 25.0 +/− 5.9 nm after 15 min. Since S-layer proteins have already demonstrated their capability to bind (bio)molecules in dense packing or to act as catalytic sites in biomineralization processes, the successful coating of pristine MWNTs has great potential in the development of new materials, such as biosensor architectures. Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes)

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12 pages, 4012 KiB

Open AccessArticle

Complex Geometry Strain Sensors Based on 3D Printed Nanocomposites: Spring, Three-Column Device and Footstep-Sensing Platform

by Alejandro Cortés, Xoan F. Sánchez-Romate, Alberto Jiménez-Suárez, Mónica Campo, Ali Esmaeili, Claudio Sbarufatti, Alejandro Ureña and Silvia G. Prolongo

Nanomaterials 2021, 11(5), 1106; https://doi.org/10.3390/nano11051106 - 25 Apr 2021

Cited by 14 | Viewed by 2921

Abstract

Electromechanical sensing devices, based on resins doped with carbon nanotubes, were developed by digital light processing (DLP) 3D printing technology in order to increase design freedom and identify new future and innovative applications. The analysis of electromechanical properties was carried out on specific [...] Read more.

Electromechanical sensing devices, based on resins doped with carbon nanotubes, were developed by digital light processing (DLP) 3D printing technology in order to increase design freedom and identify new future and innovative applications. The analysis of electromechanical properties was carried out on specific sensors manufactured by DLP 3D printing technology with complex geometries: a spring, a three-column device and a footstep-sensing platform based on the three-column device. All of them show a great sensitivity of the measured electrical resistance to the applied load and high cyclic reproducibility, demonstrating their versatility and applicability to be implemented in numerous items in our daily lives or in industrial devices. Different types of carbon nanotubes—single-walled, double-walled and multi-walled CNTs (SWCNTs, DWCNTs, MWCNTs)—were used to evaluate the effect of their morphology on electrical and electromechanical performance. SWCNT- and DWCNT-doped nanocomposites presented a higher T_g compared with MWCNT-doped nanocomposites due to a lower UV light shielding effect. This phenomenon also justifies the decrease of nanocomposite T_g with the increase of CNT content in every case. The electromechanical analysis reveals that SWCNT- and DWCNT-doped nanocomposites show a higher electromechanical performance than nanocomposites doped with MWCNTs, with a slight increment of strain sensitivity in tensile conditions, but also a significant strain sensitivity gain at bending conditions. Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes)

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15 pages, 2558 KiB

Open AccessArticle

Carbon Nanotubes Decrease the Negative Impact of Alternaria solani in Tomato Crop

by Yolanda González-García, Gregorio Cadenas-Pliego, Ángel Gabriel Alpuche-Solís, Raúl Iskander Cabrera and Antonio Juárez-Maldonado

Nanomaterials 2021, 11(5), 1080; https://doi.org/10.3390/nano11051080 - 22 Apr 2021

Cited by 24 | Viewed by 3176

Abstract

The diseases that attack the tomato crop are a limiting factor for its production and are difficult to control or eradicate. Stem and fruit rot and leaf blight caused by Alternaria solani causes severe damage and substantial yield losses. Carbon nanotubes (CNTs) could [...] Read more.

The diseases that attack the tomato crop are a limiting factor for its production and are difficult to control or eradicate. Stem and fruit rot and leaf blight caused by Alternaria solani causes severe damage and substantial yield losses. Carbon nanotubes (CNTs) could be an alternative for the control of pathogens since they have strong antimicrobial activity, in addition to inducing the activation of the antioxidant defense system in plants. In the present study, multi-walled carbon nanotubes were evaluated on the incidence and severity of A. solani. Moreover, to the impact they have on the antioxidant defense system and the photosynthetic capacity of the tomato crop. The results show that the application of CNTs had multiple positive effects on tomato crop. CNTs decreased the incidence and severity of A. solani. Furthermore, CNTs increased the fruit yield of tomato crop and dry shoot biomass. The antioxidant system was improved, since the content of ascorbic acid, flavonoids, and the activity of the glutathione peroxidase enzyme were increased. The net photosynthesis and water use efficiency were also increased by the application of CNTs. CNTs can be an option to control A. solani in tomato crop, and diminish the negative impact of this pathogen. Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes)

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12 pages, 3126 KiB

Open AccessArticle

Effect of Co₃O₄ Nanoparticles on Improving Catalytic Behavior of Pd/Co₃O₄@MWCNT Composites for Cathodes in Direct Urea Fuel Cells

by Nguyen-Huu-Hung Tuyen, Hyun-Gil Kim and Young-Soo Yoon

Nanomaterials 2021, 11(4), 1017; https://doi.org/10.3390/nano11041017 - 16 Apr 2021

Cited by 6 | Viewed by 2665

Abstract

Direct urea fuel cells (DUFCs) have recently drawn increased attention as sustainable power generation devices because of their considerable advantages. Nonetheless, the kinetics of the oxidation-reduction reaction, particularly the electrochemical oxidation and oxygen reduction reaction (ORR), in direct urea fuel cells are slow [...] Read more.

Direct urea fuel cells (DUFCs) have recently drawn increased attention as sustainable power generation devices because of their considerable advantages. Nonetheless, the kinetics of the oxidation-reduction reaction, particularly the electrochemical oxidation and oxygen reduction reaction (ORR), in direct urea fuel cells are slow and hence considered to be inefficient. To overcome these disadvantages in DUFCs, Pd nanoparticles loaded onto Co₃O₄ supported by multi-walled carbon nanotubes (Pd/Co₃O₄@MWCNT) were employed as a promising cathode catalyst for enhancing the electrocatalytic activity and oxygen reduction reaction at the cathode in DUFCs. Co₃O₄@MWCNT and Pd/Co₃O₄@MWCNT were synthesized via a facile two-step hydrothermal process. A Pd/MWCNT catalyst was also prepared and evaluated to study the effect of Co₃O₄ on the performance of the Pd/Co₃O₄@MWCNT catalyst. A current density of 13.963 mA cm⁻² and a maximum power density of 2.792 mW cm⁻² at 20 °C were obtained. Pd/Co₃O₄@MWCNT is a prospectively effective cathode catalyst for DUFCs. The dilution of Pd with non-precious metal oxides in adequate amounts is economically conducive to highly practical catalysts with promising electrocatalytic activity in fuel cell applications. Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes)

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Review

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18 pages, 5817 KiB

Open AccessReview

Tellurium Nanotubes and Chemical Analogues from Preparation to Applications: A Minor Review

by Cailing Liu, Ruibin Wang and Ye Zhang

Nanomaterials 2022, 12(13), 2151; https://doi.org/10.3390/nano12132151 - 22 Jun 2022

Cited by 6 | Viewed by 2446

Abstract

Tellurium (Te), the most metallic semiconductor, has been widely explored in recent decades owing to its fantastic properties such as a tunable bandgap, high carrier mobility, high thermal conductivity, and in-plane anisotropy. Many references have witnessed the rapid development of synthesizing diverse Te [...] Read more.

Tellurium (Te), the most metallic semiconductor, has been widely explored in recent decades owing to its fantastic properties such as a tunable bandgap, high carrier mobility, high thermal conductivity, and in-plane anisotropy. Many references have witnessed the rapid development of synthesizing diverse Te geometries with controllable shapes, sizes, and structures in different strategies. In all types of Te nanostructures, Te with one-dimensional (1D) hollow internal structures, especially nanotubes (NTs), have attracted extensive attention and been utilized in various fields of applications. Motivated by the structure-determined nature of Te NTs, we prepared a minor review about the emerging synthesis and nanostructure control of Te NTs, and the recent progress of research into Te NTs was summarized. Finally, we highlighted the challenges and further development for future applications of Te NTs. Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes)

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