Showing papers on "Nanotube published in 2022"

A novel electric-assisted photocatalytic technique using self-doped TiO2 nanotube films

Abstract: Semiconductor doping is an effective strategy for improving the light absorption efficiency and the photogenerated carrier transport in photocatalysts. However, bulk defects induced by doping act as recombination centers, accelerating the recombination of carriers, which is detrimental to the photocatalytic performance. In this study, a novel electric-assisted photocatalytic technique was developed to reduce the recombination of the carriers trapped by the defects. The technique involves applying a low external voltage to a self-doped TiO2 nanotube film, without any electrolyte and counter electrode. The remarkable improvement in the charge carrier dynamics under the electric assistance is attributed to the significant promotion of photogenerated electron fluxes and prevention of charge recombination. The electric-assisted photocatalytic technique is compatible with a liquid- or a gas-phase reactive system, e.g., water splitting, H2O2 synthesis, and CO2 photoreduction. The technique is sufficiently advanced to allow scale-up of the photocatalytic process from laboratory scale to industrial-scale.

High-performance flexible self-powered strain sensor based on carbon nanotube/ZnSe/CoSe2 nanocomposite film electrodes

Abstract: High-performance energy storage and sensing devices have been undergoing rapid development to meet the demand for portable and wearable electronic products, which require flexibility, extensibility, small volume and lightweight. In this study, we construct a lightweight and flexible self-powered sensing system by integrating a highly stretchable strain sensor with a high-performance asymmetric supercapacitor based on ZnSe/CoSe2//ECNT (ECNT: electrochemically activated carbon nanotube film). The ZnSe/CoSe2 two-dimentional nanosheets on carbon nanotube (CNT) films are synthesized through a simple and efficient strategy derived from ZnCo-based metal-organic frameworks (MOFs). The density functional theory (DFT) simulations show the higher conductivity of the ZnSe/CoSe2/CNT electrode than the CoSe2/CNT electrode. Due to the synergistic properties of self-supported two-dimentional ZnSe/CoSe2 nanosheets with high specific surface area and the high pathway of one-dimention CNTs, the nanocomposite electrode provides efficient transmission and short paths for electron/ion diffusion. The asymmetric supercapacitor provides a stable output power supply to the sensors that can precisely respond to strain and pressure changes. The sensor can also be attached to a garment for measuring a variety of joint movements.

Single-walled zeolitic nanotubes

Abstract: Description Zeolitic nanotubes Nanotubes generally have solid walls, but a low-dimensional version of zeolites now introduces porosity into such structures. Korde et al. used a structure-directing agent with a hydrophobic biphenyl group center connecting two long alkyl chains bearing hydrophilic bulky quaternary ammonium head groups to direct hydrothermal synthesis with silicon-rich precursors (see the Perspective by Fan and Dong). The nanotubes have a mesoporous central channel of approximately 3 nanometers and zeolitic walls with micropores less than 0.6 nanometers. Electron microscopy and modeling showed that the outer surface is a projection of a large-pore zeolite and the inner surface is a projection of a medium-pore zeolite. —PDS A structure-directing agent enabled the synthesis of single-walled nanotubes with zeolitic wall structures. We report the synthesis and structure of single-walled aluminosilicate nanotubes with microporous zeolitic walls. This quasi-one-dimensional zeolite is assembled by a bolaform structure-directing agent (SDA) containing a central biphenyl group connected by C10 alkyl chains to quinuclidinium end groups. High-resolution electron microscopy and diffraction, along with other supporting methods, revealed a unique wall structure that is a hybrid of characteristic building layers from two zeolite structure types, beta and MFI. This hybrid structure arises from minimization of strain energy during the formation of a curved nanotube wall. Nanotube formation involves the early appearance of a mesostructure due to self-assembly of the SDA molecules. The biphenyl core groups of the SDA molecules show evidence of π stacking, whereas the peripheral quinuclidinium groups direct the microporous wall structure.

Reduction of <math xmlns="http://www.w3.org/1998/Math/MathML" id="M1"> <mn>1</mn> <mo>/</mo> <mi>f</mi> </math> Noise in Single-Walled Carbon Nanotubes (SWCNTs) Using Gas Adsorption Technique

Abstract: Single-walled carbon nanotube (SWCNT) plays a major role in electromagnetic absorption and shielding. Their applications as semiconductors make a breakthrough in communication by miniaturizing the communication devices. The main drawback of the SWCNT is found to 1 / f noise. Because of this limitation, high attenuation at the low-frequency band cannot be achieved, limiting its application in terms of selectivity. The spectral density study shows that the noise’s amplitude is directly proportional to the temperature and inversely proportional to the number of carriers in the nanotube. The SWCNT is mainly synthesized using hydrocarbons which contains carbonaceous impurities. On the removal of impurities, more surface oxygen functional groups are formed. On the other hand, the diameter of the carbon nanotube is very small, increasing the resistance of carrier flow. In this research work, gas adsorption was used in SWCNT by treating the carbon nanotube using nitric acid. Isotherms determine porous size. The adsorbate-adsorbent interaction on carbon nanotube reduces the microporosity in the surface by treating with nitric acid. Therefore, the density of the surface increases and the CNT bundle separation will be reduced, increasing the carbon nanotube’s resistivity. This increase in resistivity reduces the excess carrier flow; therefore, the temperature will reduce the 1 / f noise. The proposed system is cost-effective and has shown 11% improvement by reducing the noise amplitude by increasing carbon nanotube resistance. This proposed method has less complexity compared with existing models.

Synthesis and Analysis of Impregnation on Activated Carbon in Multiwalled Carbon Nanotube for Cu Adsorption from Wastewater

Abstract: Industrial wastes contain more toxins that get dissolved in the rivers and lakes, which are means of freshwater reservoirs. The contamination of freshwater leads to various issues for microorganisms and humans. This paper proposes a novel method to remove excess copper from the water. The nanotubes are used as a powder in membrane form to remove the copper from the water. The multiwalled carbon nanotube is widely used as a membrane for filtration. It contains many graphene layers of nm size that easily adsorbs the copper when the water permeates through it. Activated carbon is the earliest and most economical method that also adsorbs copper to a certain extent. This paper proposes the methods of involving the activated carbon in the multiwalled carbon nanotube to improve the adsorption capability of the copper. Here, activated carbon is impregnated on the multiwalled carbon nanotube's defect and imperfect surface areas. It makes more adsorption sites on the surface, increasing the adsorption amount. The same method is applied to Hydroxyl functionalized multiwalled carbon nanotubes. Both the methods showed better results and increased the copper removal. The functionalized method removed 93.82% copper, whereas the nonfunctionalized method removed 80.62% copper from the water.

The molecular dynamics study of vacancy defect influence on carbon nanotube performance as drug delivery system

Abstract: In the current research, we described atomic vacancy defect influence on nanopumping performance of CNT structure with molecular dynamics (MD) method (for the first time). In our simulations, CNT structure is defined in the presence of C20 molecule and Au tips in the nanopumping process. Temperature and potential energy convergence after 1 ns indicated the atomic stability in defined systems, which this result arises from the appropriate settings inside the MD box. Also, the nanopumping process was detected after 0.26 ps for the CNT structure without any vacancy defect. By atomic defect implementation to C-based nanotube, the nano-pumping performance of this tube was disrupted. Numerically, by inserting 1% vacancy to pristine CNT, the nanopumping was detected after 0.29 ps. Furthermore, MD outputs predicted by implementing vacancy defect with a larger 10% ratio, nanopumping process doesn't occur. On the other hand, by nanopumping parameters optimization in defected CNT (with 1% defect), this atomic process (nanopumping) occurs after 0.24 ps.

Direct Electrochemical Visualization of the Orthogonal Charge Separation in Anatase Nanotube Photoanodes for Water Splitting

Abstract: Photoelectrochemical (PEC) water splitting is an important and rapidly developing technology that produces H2 as a renewable resource, but local surface investigations remain a major challenge. Using scanning electrochemical cell microscopy (SECCM), the PEC catalytic effects of anatase TiO2-nanotube arrays grown on Ti felt are explored. The SECCM imaging is performed both perpendicular and parallel to the nanotube growth direction. In contrast to bulk cyclic voltammetry measurements, SECCM measures only the upper region of the nanotubes that remain in contact with the electrolyte, which provides a better understanding of the phenomena connected to the longitudinal charge transport. Despite the presence of regions with higher and lower photocurrent, the PEC reactivities of the nanotube tops and walls are roughly comparable with each other. The data support the model of orthogonal electron–hole separation. This model facilitates the photogenerated hole diffusion over the short distance to the electrolyte interface due to the sufficient transport of photoexcited electrons along the long axial direction of TiO2 nanotubes and is often applied to one-dimensional systems. Observed results were additionally supported by the nanotube decoration with photoelectrochemically deposited PbO2 particles.

Ultrahigh strength, modulus, and conductivity of graphitic fibers by macromolecular coalescence

Abstract: Theoretical considerations suggest that the strength of carbon nanotube (CNT) fibers be exceptional; however, their mechanical performance values are much lower than the theoretical values. To achieve macroscopic fibers with ultrahigh performance, we developed a method to form multidimensional nanostructures by coalescence of individual nanotubes. The highly aligned wet-spun fibers of single- or double-walled nanotube bundles were graphitized to induce nanotube collapse and multi-inner walled structures. These advanced nanostructures formed a network of interconnected, close-packed graphitic domains. Their near-perfect alignment and high longitudinal crystallinity that increased the shear strength between CNTs while retaining notable flexibility. The resulting fibers have an exceptional combination of high tensile strength (6.57 GPa), modulus (629 GPa), thermal conductivity (482 W/m·K), and electrical conductivity (2.2 MS/m), thereby overcoming the limits associated with conventional synthetic fibers.