Deposition Of Single-walled Carbon Nanotubes Research Articles

Fast liquid-free patterning of SWCNT films for electronic and optical applications

The development of new approaches to assembling carbon nanotubes in next-level architecture organization is one of the key directions in Nanomaterials Science. Meanwhile, the recent advances in the so-called rational design of thin single-walled carbon nanotube (SWCNT) films promise a significant improvement in the performance of electronic and optical devices. In this study, we propose a fast, efficient, and green method for the fabrication of 2D patterned SWCNT structures. This technique is based on the selective area deposition of SWCNTs synthesized in the aerosol (floating catalyst) CVD process. Such a liquid-free and one-step process beneficially distinguishes from existing alternative methods based on lithography on the filter or post-treatment lithography on already synthesized continuous films. We demonstrate a 12-fold improvement in the performance of patterned mesh-shaped SWCNT films used as transparent electrodes when compared to the continuous film. As a result, the sheet resistance at an overall 90 % transparency in the visible light range value of 62 Ω/□ was achieved. Moreover, transferred onto elastomer, the mesh-shaped SWCNT films were efficiently applied as tunable diffraction gratings in the THz range. We believe the technique proposed extends the possibilities of the aerosol CVD process for utilization in various applications.

Dry and Binder-Free Deposition of Single-Walled Carbon Nanotubes on Fabrics for Thermal Regulation and Electromagnetic Interference Shielding

Dry and Binder-Free Deposition of Single-Walled Carbon Nanotubes on Fabrics for Thermal Regulation and Electromagnetic Interference Shielding

Arc-discharge deposition of SWCNTs over SnO2 nanowires for highly sensitive NO2 gas sensor

The air pollution caused by the emission of NO2 from vehicles in large cities is threatening human health. Thus, a highly sensitive gas sensor is required to monitor this gas. Here, we introduced the arc-discharge deposition of single-walled carbon nanotubes (SWCNTs) over SnO2 nanowires for highly sensitive NO2 gas sensors. The high-quality SnO2 nanowires were grown on-chip on interdigital Pt electrodes, whereas the SWCNTs were deposited by in situ arc-discharge method. To form the heterojunction between SnO2 nanowires and SWCNTs film, we controlled the length of the SnO2 nanowires to avoid bridging of the two electrode fingers while covering the entire surface of Pt electrodes. The SWCNTs were deposited through a shadow mask to ensure the contact between the SWCNTs and SnO2 nanowires but not the Pt electrodes. Electrical measurements confirmed the formation of non-linear contact between SnO2 nanowires and SWCNTs because of the n-p heterojunction. An increment in resistance (decrease in resistance) of the sensor was observed when measured in NO2 gas, indicating the good response characteristics of the device based on heterojunction between SnO2 nanowires and SWCNTs. In addition, gas-sensing measurement at different temperatures indicated that the fabricated sensor could detect low concentrations of NO2 gas in the range of 1–10 ppm, with response values of 20–80. The results demonstrated that the arc-discharge deposition of SWCNTs over SnO2 nanowires is effective for the fabrication of highly sensitive NO2 gas sensors.

Disposable carbon nanotube-based antifouling electrochemical sensors for detection of morphine in unprocessed coffee and milk

The direct on-site detection of illegal additives in unprocessed food samples is usually a great challenge for electrochemical sensors because of electrode biofouling. In this work, a simple filtration method for the scalable fabrication of disposable single-walled carbon nanotubes (SWCNTs)-based antifouling electrochemical sensors is reported. This method employs flash foam stamp-assisted polydimethylsiloxane (PDMS) patterns to control the region-selective deposition of SWCNTs on polyvinylidene fluoride (PVDF) membranes during filtration, which enables the scalable fabrication of a SWCNTs three-electrode-based sensor with high conductivity, good reproducibility and excellent flexibility. The resulting SWCNTs sensor exhibits a sensitive response towards morphine with a calibration range of 0.2 ∼ 100 μg mL−1 and a detection limit of 0.06 μg mL−1 (S/N = 3). Moreover, probably owing to its unique nanoporous structure, this SWCNTs sensor possesses apparently improved antifouling ability as compared with the widely used glassy carbon electrode (GCE), and allows the direct detection of morphine in unprocessed complex foods such as milk and coffee. The present work thus establishes a simple approach to the scalable production of self-designed SWCNTs electrode arrays suitable for on-site food analysis, which may also provide an alternative to commercial screen-printed carbon electrodes (SPCEs) for electrochemical sensing applications.

Fabrication and conductivity of thin PEDOT: PSS-CNT composite films

In this work, two methods for fabrication of composite conductive films, consisting of single walled carbon nanotubes (SWCNTs) and PEDOT:PSS, in order to obtain films with high conductivity and transparency for their use in solar cell structures based on Si have been compared. The thickness and optical parameters of the films were determined using the spectro-ellipsometric measurements within the spectral range 0.6…5.0 eV. The electrophysical parameters were obtained from the four-point probe measurements. Our results showed that the method for deposition of SWCNTs and PEDOT:PSS in layers enables to obtain films with a much higher conductivity (220…306 S/cm) as compared to the method of applying a film from their mixture (6…209 S/cm).

High Energy-Density Supercapacitor, Enabled By Carbon Nanostructures

Objective: A supercapacitor is an emerging energy storage technology that can exhibit capacitances of many orders of magnitude higher than traditional dielectric capacitors, owing to the atomically-small interplanar distance (i.e., the Debye length) between the electrolyte ions and the electronic charges [1]. However, a supercapacitor technology that can surpass the energy-density (in Wh/kg) of conventional batteries or fuel cells while still preserving its well-known advantages of long life-cycle, robust thermal operating range, and high power-density (in W/kg) has not yet been demonstrated.Carbon nanostructures, including single-walled carbon nanotubes (SWCNTs) and graphene (or reduced graphene oxide, rGO), possess the great potential to advance the energy storage technology due to their excellent thermal and electrical conductivity, flexibility while maintaining strength, high surface area-to-mass ratio, and elemental abundancy [1]. A previous work by Niu and co-workers [2] demonstrated the rGO-based micro-supercapacitors (i.e., having rGO as the interdigitated electrodes) with enhanced specific capacitances. Although a preliminary test was performed on how such device parameters as electrode width would impact the overall supercapacitor performance, a physical, specific insight was still not provided on how the biggest existing challenge of modern supercapacitor – namely, relatively low energy-density, can be addressed. In this work, we carefully designed a device fabrication process to develop the electric double layer capacitor (EDLC)-type [3] micro-supercapacitors and investigated both carbon nanostructures (Fig. 1 for SWCNT (a) and rGO (b) solutions) as electrodes. The great tunability of these carbon nanostructures (by surface functionalization, chemical reduction, etc.) will lead us to systematically investigate the effect of varying design parameters on the energy-density aspect of the supercapacitor performance. New Results: We adopted both experimental and theoretical approaches to best study the carbon nanostructure-based micro-supercapacitor devices. Experimentally, our device fabrication process is much simpler than what is shown in the previous work [2], thus enabling us to fabricate and test a greater number of prototype devices of varying electrode dimensions (Fig. 2 for a representative photomask design with electrode width and space of 400 mm). The device fabrication process includes photolithography to pattern the interdigitating electrode structure, dropwise deposition of SWCNT or rGO, polymeric coverage of electrode ends to protect Au contacts, Au etching via iodine gas, and deposition of H3PO4/PVA gel electrolyte (Fig. 3 for the detailed fabrication process flow). It is important to note that in this work, the carbon nanostructures were deposited by using a hypodermic syringe (Fig. 4). This ensures ease of electrode deposition because otherwise some other expensive experimental techniques would have been used (e.g., electrophoretic deposition [2]).To verify the validity of our devices and further guide our experimental efforts, we created a model to simulate the rGO/CNT-based micro-supercapacitors. Two models were created in this work (one with MATLAB and another with PSpice), allowing us to compare and confirm our simulation results (Fig. 5 for the circuit diagram). To accurately model the supercapacitor device, a simple capacitor model was first created to serve as the foundation, and then we used data from the capacitor to create a look-up table based on the capacitance-voltage curve of the capacitor [4-5]. From these models we were able to collect the output power, current and voltage of the supercapacitor device. Fig. 6 shows the simulated energy-density and power-density plot of the supercapacitor based on rGO (a) and SWCNT (b) electrodes. Significance: Currently available renewable energy sources supply only a very small fraction of the electricity consumed in the nation. For example, only 1.7% of about 4 trillion kWh of electricity was generated from photovoltaics in 2019 [6]. This is mainly due to a great challenge in enhancing the solar energy conversion efficiency while still keeping the affordable price [7]. High energy-density supercapacitors developed in this work will serve as the next-generation energy storage device to greatly complement the existing energy harvesting or conversion technologies by dealing with the intermittent nature of renewable energy sources.

Discontinuous Dewetting, Template-Guided Self-Assembly, and Liquid Bridge-Transfer Printing of High-Resolution Single-Walled Carbon Nanotube Lines for Next-Generation Electrodes and Interconnects

A template-guided, self-assembly patterning technique called discontinuous dewetting (DD) and liquid bridge transfer (LBT) was applied to successfully pattern single-walled carbon nanotubes (SWCNTs): the first 1D nanomaterials patterned using the technique. The technique could efficiently and simply pattern SWCNTs with 2.5-10 mu m resolution using little energy, low temperature (<= 90 degrees C), and low cost and is potentially compatible with roll-to-roll manufacturing. Many variables were investigated to determine successful patterning conditions. The SWCNT patterning technique demonstrates the potential to obtain the often mutually exclusive properties for SWCNT patterning of high resolution and fast throughput/manufacturability. Due to the low concentration attainable in SWCNT dispersions, a preliminary wetting layer and evaporation-driven deposition were required to achieve a uniform and high-density deposition of SWCNTs inside the patterned cavities of a polydimethylsiloxane transfer stamp. The wetting layer allowed for uniform SWCNT deposition inside the cavities by preventing depinning of the SWCNT ink solution in the cavities. The wetting layer also doubled as a release layer during LBT, allowing easy transfer of the SWCNT lines onto hydrophilic substrates. SWCNT lines were patterned with widths down to 2.5 mu m, up to centimeter lengths, and a resistivity of 1.9 X 10(-3 )Omega m without any annealing. This work demonstrates the potential of DD and LBT patterning of SWCNTs for high-resolution R2R printing of cheap and/or flexible next-generation electrodes and interconnects.

(Invited) Carbon Nanotubes As an Effective and Stable p-Type Contact for Perovskite Solar Cells

The enormous strides researchers have made in advancing perovskite-based photovoltaics in the past few years are fueling the dream of a rapid entry of this highly promising technology into the global energy market. This seems like serendipitous timing since solar power has gained an enormous momentum over the past decade exceeding all projections. This expansion in solar power is driven by an increasing understanding that climate change requires immediate action, in particular with regards to power generation; and simultaneously, the price for photovoltaic modules has remarkably quickly fallen to make solar power generation competitive vis-à-vis conventional technologies.Compositional tuning of the perovskite absorber has led to immense improvements in stability and efficiency of perovskite solar cells leading to a certified efficiency of over 25% for a single-junction laboratory device. The successful transition of a photovoltaic technology from the lab into the field requires, however, two additional important parameters aside from efficiency which are essential for real-world deployment: stability and scalability.We propose using single-walled carbon nanotubes (SWCNTs) as an alternative p-type layer for future application in perovskite solar cells.Carbon nanotubes combine several highly attractive characteristics such as chemical inertness and mechanical resilience with intrinsically high charge-carrier mobilities endowing them with a unique potential for a much more stable dopant-free charge-selective contact. Furthermore, the SWCNT deposition techniques for large-scale use, such as spray coating, are already well-established opening clear avenues for direct implementation in a real-world industrial setting.We demonstrate that a cascade-like transfer extraction through SWCNTs can minimize photovoltage losses by suppressing non-radiative recombination. By further improving the absorber quality, the voltage losses in solar cells can be reduced to around 340 mV which is comparable to conventional III-V semiconductor-based photovoltaics.By further enhancing the selective charge extraction at the perovskite-SWCNT interface through interfacial charge transfer doping, we achieve steady-state efficiencies approaching 22% for alloyed narrow bandgap perovskites, illustrating the versatility and excellent performance of SWCNTs as contact material.

Effect of Concentration of Single-Wall Carbon Nanotubes (SWCNTs) in a SWCNTs/ZnO Nanorods Channel-Based Thin-Film Transistor

Fabrication of three thin-film transistor devices by deposition of single-walled carbon nanotubes (SWCNTs) thin film over hydrothermally grown nanorods of zinc oxide (ZnO) on silicon dioxide (SiO2) layered n-type silicon is reported. In this architecture, SWCNTs/ZnO nanorods were used for the channel layer. The silicon dioxide deposited over silicon substrate was used as a dielectric. Three devices were prepared by varying the concentration of carbon nanotubes to investigate the effect on electrical properties of prepared thin-film transistors. XRD and EDX analysis was performed for the study of structural and elemental properties. Scanning electron microscopy (SEM) was used to examine the surface morphology of SWCNTs/ZnO nanorods. Transfer and output characteristics were studied using a Keithley SourceMeter. I–V analysis revealed that an increase in the concentration of carbon nanotubes increased the mobility values and Ion/Ioff, but the threshold voltage was decreased.

Fabrication of optimally configured layers of SWCNTs, gold nanoparticles, and glucose oxidase on ITO electrodes for high-power enzymatic biofuel cells

We designed an enzymatic biofuel cell (EFC) that utilizes indium tin oxide (ITO) electrodes, and sequential deposition of single-walled carbon nanotube (SWCNT) and gold nanoparticle (AuNP) layers on the electrodes to enhance their electron transfer. Cyclic voltammograms of the SWCNT-modified ITO electrodes showed higher peak currents compared to those of the bare ITO electrodes. Immobilization of glucose oxidase (GOD) on SWCNT-modi-fied ITO electrodes increased their electron transfer resistance by a factor of ten, which could be mitigated by incorporating an AuNP layer between the GOD and SWCNT layers. The single-layer GOD generated higher current than the doubled-layer GOD, with higher specific activity. The assembled EFC featured SWCNT-modified ITO electrodes with sequential layers of immobilized AuNPs and GOD (anode), and with a single layer of immobilized bilirubin oxidase (BOD) (cathode). The cathode performance was further improved by the presence of AuNPs between the BOD and SWCNTs on cathode. The enhanced electron transfer kinetics and enzymatic activity observed for SWCNT/AuNP-modified ITO electrodes resulted in a maximum power density of 38.2±2.0 µW/cm2 at 0.57±0.03 V of a cell voltage.

Fabrication, electrical characterization and mechanical flexibility test of back gated carbon nanotube thin film transistors on polyimide substrate

This work demonstrates the scalable method of fabricating back gated carbon nanotube thin film transistors (CNTTFTs) on a polyimide (kapton) substrate using photo lithography and lift-off process for patterning gate dielectrics and metals deposited for electrodes , and dip coating method for single walled carbon nanotubes deposition on functionalized dielectric surface. The CNTTFTs of varying dimensions are fabricated and electrical characterizations are done at room temperature and the CNTTFTs have exhibited p-type behaviour. The CNTTFT of channel length(L) 3 μm, width(W) 10 μm exhibits on-off current ratio of 9.219 × 105, carrier mobility of 4.9 cm2 V−1 s−1, trans conductance of 26 μS and on current of 472 μA when the substrate is kept flat (not bent). The mechanical flexibility test of CNTTFTs is done by conducting electrical characterization of CNTTFTs with the substrate bent to different diameters. Irrespective of the channel length, CNTTFTs have exhibited minimal change in the electrical characteristics when bent to 14 mm diameter. However, short channel CNTTFT (L = 3 μm) has shown considerable change in electrical characteristics when bent to 8 mm diameter compared to long channel length CNTTFT (L = 75 μm). The fabricated back gated flexible CNTTFTs work as CNTTFTs when bent up to the diameter of 8 mm, demonstrates that the CNTTFTs can be used for practical applications in the area of flexible electronics.

Carbon Nanotubes - the p-Type Contact of the Future for Perovskite Solar Cells?

The enormous strides researchers have made in advancing perovskite based photovoltaics in the past few years are fueling the dream of a rapid entry of this highly promising technology into the global energy market. This seems like serendipitous timing since solar power has gained an enormous momentum over the past decade exceeding all projections. This expansion in solar power is driven by an increasing understanding that climate change requires immediate action, in particular with regards to power generation; and simultaneously, the price for photovoltaic modules has remarkably quickly fallen to make solar power generation competitive vis-à-vis conventional technologies. Compositional tuning of the perovskite absorber has led to immense improvements in stability and efficiency of perovskite solar cells leading to a certified efficiency of 22.7% for a single-junction laboratory device. The successful transition of a photovoltaic technology from the lab into the field requires, however, two additional important parameters aside from efficiency which are essential for real-world deployment: stability and scalability. We propose using single-walled carbon nanotubes (SWCNTs) as p-type layer for perovskite solar cells for future applications. Carbon nanotubes combine several highly attractive characteristics such as chemical inertness and mechanical resilience with intrinsically high charge-carrier mobilities endowing them with a unique potential to be a very stable dopant-free charge-selective contact. Furthermore, the SWCNT deposition techniques for large-scale use, such as spray-coating, are already well-established, opening clear avenues for direct implementation in a real-world industrial setting. In this study, we demonstrate that employing SWCNTs as hole-transporting material can yield steady-state efficiencies of above 20% for alloyed narrow bandgap perovskites, and of over 7% for wide-bandgap perovskites, illustrating the versatility and excellent performance of SWCNTs as charge-selective contact material.

Catalysts for single-wall carbon nanotube synthesis—From surface growth to bulk preparation

Abstract

Highly sensitive detection of hexavalent chromium utilizing a sol-gel/carbon nanotube modified electrode

A pyridine-functionalized thin film has been fabricated to selectively preconcentrate Cr(VI) anions for electrochemical detection in the 5–300μgL−1 range. Glassy carbon electrodes were modified through physical deposition of single-walled carbon nanotubes (SWNTs) on the electrode surface, followed by electrochemical deposition of a sol-gel containing a 2-pyridine functional group. The use of SWNTs has increased sensitivity for Cr(VI) detection in aqueous solutions, providing a detection limit of 0.8μgL−1.

Pulmonary Inflammation Induced by Single Walled Carbon Nanotubes in Golden Syrian Hamsters

Single-walled carbon nanotubes (SWCNTs) have a broad range of applications; however, they may present a potential health hazard. The current study was undertaken to evaluate the effects of inhalation exposure of aerosolized SWCNTs on hamster lungs. Golden Syrian Hamsters were divided in to 2 groups: a control group that was exposed to an aerosol of distilled water, and a treated group exposed to aerosolized SWCNTs at concentrations of 1, 2 or 4mg/m3 for 2hrs/day for 4 consecutive days. Additional groups were used to investigate longer inhalation periods (8 and 14 days) with exposures of 4hrs/day to 2mg/m3 SWCNTs. One day post exposure, hamsters were euthanized. Tissue sections were evaluated by TUNEL assay to determine apoptosis and tissue homogenates were used to measure endothelin-1 (ET-1) levels. Bronchoalveolar lavage fluid (BALF) was used to determine total leukocyte cell numbers, tumor necrosis factor receptor type 1 (TNFR1) counts and endothelin receptor subtypes A (ETA) levels on alveolar macrophages. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were carried out on lung tissue sections. The current study demonstrates inhalation exposures to SWCNTs in hamster induce pulmonary inflammation. Results from histological analysis of tissue sections indicated increase in inflammatory cells predominantly macrophages in airways and hyperplasia of airway epithelial cells. SWCNTs treatment significantly increased total BAL leukocyte counts, TNFR1 and lung ET-1 levels. SWCNTs treatment caused an increase in ETA levels and evidence of lung toxicity was demonstrated by apoptosis. SWCNTs deposition in alveolar airspaces along with changes to alveolar epithelium was observed in tissue sections examined by TEM.

Upcycling spent petroleum cracking catalyst: pulsed laser deposition of single-wall carbon nanotubes and silica nanowires

From waste to single-wall carbon nanotubes and silica nanowires: the first high-tech outlet for FC3R.

An electrochemical quartz crystal microbalance study on adsorption of single walled carbon nanotubes onto poly[3,4-ethylenedioxythiophene] layers

Deposition by adsorption of single walled carbon nanotubes (SWCNTs) onto electrodeposited poly[3,4-ethylenedioxythiophene] (PEDOT) films is reported. Electrochemical quartz crystal microbalance (EQCM) measurements in dispersive mode reveal resonance frequency decrease as well as growth of acoustic resistance during the SWCNT deposition. These data were interpreted in terms of increasing of the roughness of the surface and the corresponding change of surface impedance. The thus in situ obtained estimates of size and irregularities agree with ex situ scanning electron microscopy data. Transmission electron microscopy was used to analyze the size and the morphology of the SWCNTs, which were mostly occurring as bundles of nanotubes rather than individual ones. Electroactivity of PEDOT and PEDOT-SWCNT films was studied with regard to the detection of dopamine.

The Application of Gas Dwell Time Control for Rapid Single Wall Carbon Nanotube Forest Synthesis to Acetylene Feedstock.

One aspect of carbon nanotube (CNT) synthesis that remains an obstacle to realize industrial mass production is the growth efficiency. Many approaches have been reported to improve the efficiency, either by lengthening the catalyst lifetime or by increasing the growth rate. We investigated the applicability of dwell time and carbon flux control to optimize yield, growth rate, and catalyst lifetime of water-assisted chemical vapor deposition of single-walled carbon nanotube (SWCNT) forests using acetylene as a carbon feedstock. Our results show that although acetylene is a precursor to CNT synthesis and possesses a high reactivity, the SWCNT forest growth efficiency is highly sensitive to dwell time and carbon flux similar to ethylene. Through a systematic study spanning a wide range of dwell time and carbon flux levels, the relationship of the height, growth rate, and catalyst lifetime is found. Further, for the optimum conditions for 10 min growth, SWCNT forests with ~2500 μm height, ~350 μm/min initial growth rates and extended lifetimes could be achieved by increasing the dwell time to ~5 s, demonstrating the generality of dwell time control to highly reactive gases.

Novel felt pseudocapacitor based on carbon nanotube/metal oxides

This work describes a novel supercapacitor electrode based on a glass fiber felt substrate, single-walled carbon nanotube (SWCNT) and metal oxide layers (RuO2 or MnO2). It is fabricated by the repeated and alternate deposition of SWCNTs and metal oxides via dipping and electrodeposition, respectively, to achieve three-dimensional layered hierarchical structured supercapacitor electrodes. The results show that the layered structured electrodes fabricated by alternating deposition of SWCNTs and metal oxides have higher capacitance as compared with the bulk deposited samples, which are fabricated by deposition of SWCNTs followed by metal oxides. The best configuration studied in this work shows specific capacitance of 72 and 98 F/g for the SWCNT–MnO2 and SWCNT–RuO2, respectively, whereas the corresponding areal capacitances are 0.07 and 0.09 F/cm2. This three-dimensional porous electrode structure design combines the high mechanical stability of the felt substrate with the high conductivity and specific surface area of SWCNTs, and the high capacitance of metal oxides. This will add immensely to the research and development of wearable lightweight electronics in harsh environments.

Ni2O3 decoration of In2O3 nanostructures for catalytically enhanced methane sensing

The explosive limit of methane (CH4) gas concentration is 5%. However, detection of CH4 gas at lower concentrations is essential for prevention and warning purposes in leaking gas systems. In this study, a simple method for fabricating thin films of granular indium oxide (In2O3) particles decorated with nickel oxide (Ni2O3) nanoparticles was developed for high response CH4 gas sensor. The In2O3 granular film was fabricated by sputter deposition of indium, followed by oxidation. Ni2O3 nanoparticles were deposited onto the In2O3 film by arc-discharge deposition of single-wall carbon nanotubes (SWCNTs) with Ni catalyst nanowires, followed by burning the carbon nanotubes. The Ni nanoparticle catalysts deposited on the SWCNTs were then oxidized to Ni2O3.The Ni2O3 nanoparticles on the surface exhibited a catalytic role in methane gas reactions, resulting in reduction of operation temperature. The sensors showed relatively high response percentage per 100 ppm methane gas concentration.