Langmuir−Blodgett Assembly of Densely Aligned Single-Walled Carbon Nanotubes from Bulk Materials

Nonideality in Arrayed Carbon Nanotube Field Effect Transistors Revealed by High-Resolution Transmission Electron Microscopy

High density and high semiconducting-purity single-walled carbon nanotube array (A-CNT) have recently been demonstrated as promising candidates for high-performance nanoelectronics. Knowledge of the structures and arrangement of CNTs within the arrays and their interfaces to neighboring CNTs, metal contacts, and dielectrics, as the key components of an A-CNT field effect transistor (FET), is essential for device mechanistic understanding and further optimization, particularly considering that the current technologies for the fabrication of A-CNT wafers are mainly laboratory-level solution-based processes. Here, we conduct a systematic investigation into the microstructures of A-CNT FETs mainly via cross-sectional high-resolution transmission electron microscopy and tentatively establish a framework consisting of up to 11 parameters which can be used for structure-side quality evaluation of the A-CNT FETs. The parameter ensemble includes the diameter, length (or terminal), and density distribution of CNTs, radial deformation of CNTs, array alignment defects, surface crystallography facets of contact metal, thickness distribution of high-k dielectrics (HfO2), and the contact ratios for the CNT-CNT, CNT-metal, CNT-dielectric, and CNT-substrate interfaces. Enriched array alignment defects, i.e., bundle, stacking, misorientation, and voids, are observed with a total ratio sometimes up to ∼90% in pristine A-CNTs and even up to ∼95% after the device fabrication process. Thus, they are suggested as the prevalent performance-limiting factors for A-CNT FETs. Complex interfacial structures are observed at the CNT-CNT, CNT-metal contact, and CNT-high-k dielectric interfaces, making the local environment and the property of each component CNT involved in an A-CNT FET distinct from others in terms of the diameters, radial deformation, and interactions with the local surroundings (mainly through van der Waals interactions). The present study suggests further improvements on the fabrication technology of A-CNT wafers and devices and mechanistic investigations into the impacts of complex array alignment defects and interface structures on the electrical performance of A-CNT FETs as well.

Removing Conjugated Polymers from Aligned Carbon Nanotube Arrays

Aligned carbon nanotube (A-CNT) with high semiconducting purity and high-density have been considered as one of the most promising active channels for field-effect transistors (FETs), but conjugated polymer dispersant residues on the surface of A-CNT have become the main obstacle for its further development in electronics applications. In this work, a series of removable conjugated polymers (CPs) are designed and synthesized to achieve favorable purification and alignment for CNT arrays with a high density of ≈360 CNTs/µm. Furthermore, a removal process of CPs on the CNT array film is developed. Raman spectra show that the CNTs in array film are almost not damaged after the removal process, and the G/D ratio is as high as 35. The field-effect transistors (FETs) are fabricated with a saturation current density up to 600 µA µm-1 and a current on-off ratio of ≈105, even with a relatively long channel length of ≈3 µm.

Assembly and Alignment of High Packing Density Carbon Nanotube Arrays Using Lithographically Defined Microscopic Water Features

High packing density aligned arrays of semiconducting carbon nanotubes (CNTs) are required for many electronics applications. Past work has shown that the accumulation of CNTs at a water-solvent interface can drive array self-assembly. Previously, the confining interface was a large-area, macroscopic feature. Here, we report on the CNT assembly on microscopic water features. Water microdroplets are formed on 10-100 μm wide hydrophilic stripes patterned on a substrate. Exposure to CNTs dispersed in solvent accumulates CNTs at the microdroplet-solvent interface, driving their alignment and deposition at the microdroplet-solvent-substrate contact line. Compared with macroscopic methods in which the contact line uncontrollably moves across the substrate as it is pulled out of the liquids, the hydrophilic patterns and microdroplets allow pinning of the contact line. As CNTs deposit, the contact line self-translates, allowing for dense CNT packing. We realize monolayer CNT arrays aligned within ±3.9° at density of 250 μm-1 and field effect transistors with a high current density of 1.9 mA μm-1 and transconductance of 1.2 mS μm-1 at -0.6 V drain bias and 60 nm channel length.

Parameters Affecting Interfacial Assembly and Alignment of Nanotubes

Tangential flow interfacial self-assembly (TaFISA) is a promising scalable technique enabling uniformly aligned carbon nanotubes for high-performance semiconductor electronics. In this process, flow is utilized to induce global alignment in two-dimensional nematic carbon nanotube assemblies trapped at a liquid/liquid interface, and these assemblies are subsequently deposited on target substrates. Here, we present an observational study of experimental parameters that affect the interfacial assembly and subsequent aligned nanotube deposition. We specifically study the water contact angle (WCA) of the substrate, nanotube ink composition, and water subphase and examine their effects on liquid crystal defects, overall and local alignment, and nanotube bunching or crowding. By varying the substrate chemical functionalization, we determine that highly aligned, densely packed, individualized nanotubes deposit only at relatively small WCA between 35 and 65°. At WCA (< 10°), high nanotube bunching or crowding occurs, and the film is nonuniform, while aligned deposition ceases to occur at higher WCA (>65°). We find that the best alignment, with minimal liquid crystal defects, occurs when the polymer-wrapped nanotubes are dispersed in chloroform at a low (0.6:1) wrapper polymer to nanotube ratio. We also demonstrate that modifying the water subphase through the addition of glycerol not only improves overall alignment and reduces liquid crystal defects but also increases local nanotube bunching. These observations provide important guidance for the implementation of TaFISA and its use toward creating technologies based on aligned semiconducting carbon nanotubes.

Directional Activated Exciton Highway via Fractal Electric Field Modulation for Ultrasensitive Carbon Nanotube-Based Sensors

The electrical vapor sensor based on carbon nanotubes (CNTs) has attracted wide attention due to its excellent conductivity, stable interfacial structure, and low dimensional quantum effects. However, the conductivity and contact interface activity were still limited by the random distribution of coated CNTs, which led to limited performance. We developed a new strategy to unify the CNT directions with image fractal designing of the electrode system. In such a system, directional aligned CNTs were gained under a well-modulated electric field, leading to microscale CNT exciton highways and molecule-scale host-guest site activation. The carrier mobility of the aligned CNT device is 20-fold higher than that of the random network CNT device. With excellent electrical properties, such modulated CNT devices based on fractal electrodes behave as an ultrasensitive vapor sensor for methylphenethylamine, a mimic of illicit drug methamphetamine. The detection limit reached as low as 0.998 ppq, 6 orders of magnitude sensitive than the reported 5 ppb record based on interdigital electrodes with random distributed CNTs. Since the device is easily fabricated in wafer-level and compatible with the CMOS process, such a fractal design strategy for aligned CNT preparation will be widely applied in a variety of wafer-level electrical functional devices.

Spontaneous clustering of exfoliated two-dimensional materials at the air-water interface

HYPOTHESIS

Coating approaches which trap nanoparticles at an interface have become popular for depositing single-layer films from nanoparticle dispersions. Past efforts concluded that concentration and aspect ratio dominate the impact on aggregation state of nanospheres and nanorods at an interface. Although few works have explored the clustering behaviour of atomically thin, two-dimensional materials, we hypothesize that nanosheet concentration is the dominant factor leading to a particular cluster structure and that this local structure impacts the quality of densified Langmuir films.

EXPERIMENTS

We systematically studied cluster structures and Langmuir film morphologies of three different nanosheets, namely chemically exfoliated molybdenum disulfide, graphene oxide and reduced graphene oxide.

FINDINGS

We observe cluster structure transitions from island-like domains to more linear networks in all materials as dispersion concentration is reduced. Despite differences in material properties and morphologies, we obtained the same overall correlation between sheet number density (A/V) in the spreading dispersion and cluster fractal structure (d_f) is observed, with reduced graphene oxide sheets showing a slight delay upon transitioning into a lower-density cluster. Regardless of assembly method, we found that cluster structure impacts the attainable density of transferred Langmuir films. A two-stage clustering mechanism is supported by by considering the spreading profile of solvents and an analysis of interparticle forces at the air-water interface.

Micron-Scale Fabrication of Ultrathin Amorphous Copper Nanosheets Templated by DNA Scaffolds

Two-dimensional (2D) amorphous materials could outperform their crystalline counterparts toward various applications because they have more defects and reactive sites and thus could exhibit a unique surface chemical state and provide an advanced electron/ion transport path. Nevertheless, it is challenging to fabricate ultrathin and large-sized 2D amorphous metallic nanomaterials in a mild and controllable manner due to the strong metallic bonds between metal atoms. Here, we reported a simple yet fast (10 min) DNA nanosheet (DNS)-templated method to synthesize micron-scale amorphous copper nanosheets (CuNSs) with a thickness of 1.9 ± 0.4 nm in aqueous solution at room temperature. We demonstrated the amorphous feature of the DNS/CuNSs by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Interestingly, we found that they could transform to crystalline forms under continuous electron beam irradiation. Of note, the amorphous DNS/CuNSs exhibited much stronger photoemission (∼62-fold) and photostability than dsDNA-templated discrete Cu nanoclusters due to the elevation of both the conduction band (CB) and valence band (VB). Such ultrathin amorphous DNS/CuNSs hold great potential for practical applications in biosensing, nanodevices, and photodevices.

Stable water-floating transistor with recyclability

Electronic wastes from used devices containing environmentally hazardous materials are an immediate concern for the sustainable development of electronic and sensor industries. To address this, a highly controllable and dedicated electronic module should be devised, that allows systematic recollection of as many components from the original device for their reuse. Here, we report the total recycling of an electronic device, exploiting a water-floating system that is based on a water-compatible semiconductor as an active material. To do so, we developed a system for stable electronics on the water surface. The floating semiconductor features a tunable morphology on the water surface, and is constructed into a water-floating gated transistor (WFGT) and water floating sensor (WFS), exhibiting an on-current of 4.2 × 10^-5 A and an on/off ratio of ∼10³. The device showed high recyclability over 25 cycles, with an efficiency of 99 ± 0.9% within 1 cycle and 92 ± 0.7% within 30 cycles. Furthermore, the device was also found to be stable for over 10 days. Our system has the potential to be an eco-friendly, cost-effective, and scalable device that is fully recyclable, which can be applied in areas once thought of as being beyond the scope of current semiconductor technology.

Controlled Preparation of Single-Walled Carbon Nanotubes as Materials for Electronics

Single-walled carbon nanotubes (SWCNTs) are of particular interest as channel materials for field-effect transistors due to their unique structure and excellent properties. The controlled preparation of SWCNTs that meet the requirement of semiconducting and chiral purity, high density, and good alignment for high-performance electronics has become a key challenge in this field. In this Outlook, we outline the efforts in the preparation of SWCNTs for electronics from three main aspects, structure-controlled growth, selective sorting, and solution assembly, and discuss the remaining challenges and opportunities. We expect that this Outlook can provide some ideas for addressing the existing challenges and inspire the development of SWCNT-based high-performance electronics.

Femtosecond Er-Doped All-Fiber Laser with High-Density Well-Aligned Carbon-Nanotube-Based Thin-Film Saturable Absorber

We have studied the ultrafast saturation behavior of a high-density well-aligned single-walled carbon nanotubes saturable absorber (HDWA-SWCNT SA), obtained by a high-pressure and high-temperature treatment of commercially available single-wall carbon nanotubes (SWCNTs) and related it to femtosecond erbium-doped fiber laser performance. We have observed the polarization dependence of a nonlinear optical saturation, along with a low saturation energy level of <1 fJ, limited to the detector threshold used, and the ultrafast response time of <250 fs, while the modulation depth was approximately 12%. We have obtained the generation of ultrashort stretched pulses with a low mode-locking launching threshold of ~100 mW and an average output power of 12.5 mW in an erbium-doped ring laser with the hybrid mode-locking of a VDVA-SWNT SA in combination with the effects of nonlinear polarization evolution. Dechirped pulses with a duration of 180 fs were generated, with a repetition rate of about 42.22 MHz. The average output power standard deviation was about 0.06% RMS during 3 h of measurement.

The Relevant Approaches for Aligning Carbon Nanotubes

Carbon-nanotube (CNT) is a promising material owing to its compelling mechanical, thermal and electrical properties and has been applied in a broad variety of fields such as composite, fiber, film and microelectronic. Although the introductions of CNT have brought huge improvement for many applications, these properties of macrostructures prepared by CNTs still cannot meet those of individual CNT. Disordered alignment of CNTs in the matrix results in degradation of performance and hinders further application. Nowadays, quantities of methods are being researched to realize alignments of CNTs. In this paper, we introduce the application of CNTs and review some typical pathways for vertical and horizontal alignment, including chemical vapor disposition, vertical self-assembly, external force, film assisted, electric field, magnetic field and printing. Besides that, advantages and disadvantages of specific methods are also discussed. We believe that these efforts will contribute to further understanding the nature of aligned CNT and generating more effective ideas to the relevant workers.

Ultrafast growth of carbon nanotubes using microwave irradiation: characterization and its potential applications

Carbon nanotubes (CNTs) have been studied for more than twenty-five years due to their distinguishing features such as high tensile strength, high elastic module, high surface area, high thermal and electrical conductivity, making them ideal for a variety of applications. Nanotechnology and nanoscience researchers are working to develop CNTs with appropriate properties for possible future applications. New methodologies for their synthesis are clearly needed to be developed and refined. In this research, the authors look at the history and the recent developments of carbon nanotubes synthesis methods for CNTs, such as arc discharge, laser ablation, chemical vapour deposition and microwave irradiation. New immerging methods like microwave irradiation for the growth of CNTs and their composite was extensively reviewed. Low temperature and ultrafast growth of CNT through microwave irradiation technique were examined and discussed. In addition, all the techniques used for the CNTs characterization were also briefly discussed. Special attention was dedicated to the application of CNTs. This review has extensively explored future applications in the biomedical sector, industrial water purifications, CNTs composites, energy and storage devices.

•

Synthesis of carbon nanotubes using different methods.

•

Microwave irradiation techniques are used for the growth of CNTs.

•

Current challenge and future aspects of CNTs growth.

•

Detailed characterization and application of CNTs.

Ion-Incorporative, Degradable Nanocellulose Crystal Substrate for Sustainable Carbon-Based Electronics

Electronic wastes from transient electronics accumulate biologically harmful materials with global concern. Recycling these wastes could prevent the deposition of hazardous chemicals and toxic materials to the environment while saving scarce natural compounds and valuable resources. Here, we report a sustainable electronic device, taking advantage of carbon resources and a biodegradable cellulose composite. The device consists of an ambient-stable carbon nanotube as a semiconductor, graphene as electrodes, and a free-standing cellulose filter paper/nanocellulose composite as a dielectric layer. The dual-functional cellulose composite acting simultaneously as a robust substrate and a dielectric is demonstrated, which is compatible with solution device fabrication processes. An optimized channel dimension of 5 mm × 3 mm with the addition of ions that facilitates a charge transport realized a device with an on-current per width of 9.6 μA mm^-1, an on/off ratio >10², a field-effect mobility of 2.03 cm² V^-1 s^-1, and long-term stability over 30 days under ambient conditions. Successful separation of the carbonaceous components via an eco-friendly solution sorting protocol allowed the recycled device to display excellent electronic performance, with a recapture efficiency of 90%. This effort demonstrates a processable, low-cost, and sustainable electronic system that can be applied in the current realm of the semiconducting and sensing industry.

Langmuir-Blodgett Deposition of Cellulose Nanocrystal Surfactants into Ordered Monolayers

The cellulose nanocrystals (CNCs) are shown to interact with amine-functionalized polyhedral oligomeric silsesquioxane (POSS-NH₂) strongly at the water/oil interface, forming the CNC-POSS assemblies, that is, CNC surfactants that decrease the interfacial tension of the water/chloroform greatly. When bringing the CNC aqueous solution and POSS chloroform solution into a Langmuir trough, they form a monolayer of the CNC surfactants. Upon applying a continuous compression, a distinct transition appears in the surface pressure-area curves, and during this transition, the packing of the CNC surfactants in the produced monolayers transits from network-like patterns to ordered alignment.

A simple simulation-derived descriptor for the deposition of polymer-wrapped carbon nanotubes on functionalized substrates

Controlling the deposition of polymer-wrapped single-walled carbon nanotubes (s-CNTs) onto functionalized substrates can enable the fabrication of s-CNT arrays for semiconductor devices. In this work, we utilize classical atomistic molecular dynamics (MD) simulations to show that a simple descriptor of solvent structure near silica substrates functionalized by a wide variety of self-assembled monolayers (SAMs) can predict trends in the deposition of s-CNTs from toluene. Free energy calculations and experiments indicate that those SAMs that lead to maximum disruption of solvent structure promote deposition to the greatest extent. These findings are consistent with deposition being driven by solvent-mediated interactions that arise from SAM-solvent interactions, rather than direct s-CNT-SAM interactions, and will permit the rapid computational exploration of potential substrate designs for controlling s-CNT deposition and alignment.

Recent Advances in Structure Separation of Single-Wall Carbon Nanotubes and Their Application in Optics, Electronics, and Optoelectronics

Structural control of single-wall carbon nanotubes (SWCNTs) with uniform properties is critical not only for their property modulation and functional design but also for applications in electronics, optics, and optoelectronics. To achieve this goal, various separation techniques have been developed in the past 20 years through which separation of high-purity semiconducting/metallic SWCNTs, single-chirality species, and even their enantiomers have been achieved. This progress has promoted the property modulation of SWCNTs and the development of SWCNT-based optoelectronic devices. Here, the recent advances in the structure separation of SWCNTs are reviewed, from metallic/semiconducting SWCNTs, to single-chirality species, and to enantiomers by several typical separation techniques and the application of the corresponding sorted SWCNTs. Based on the separation procedure, efficiency, and scalability, as well as, the separable SWCNT species, purity, and quantity, the advantages and disadvantages of various separation techniques are compared. Combined with the requirements of SWCNT application, the challenges, prospects, and development direction of structure separation are further discussed.

Review on 3D growth engineering and integration of nanowires for advanced nanoelectronics and sensor applications

Recent years have witnessed increasing efforts devoted to the growth, assembly and integration of quasi-one dimensional (1D) nanowires (NWs), as fundamental building blocks in advanced three-dimensional (3D) architecture, to explore a series of novel nanoelectronic and sensor applications. An important motivation behind is to boost the integration density of the electronic devices by stacking more functional units in theout-of-plane z-direction, where the NWs are supposed to be patterned or grown as vertically standing or laterally stacked channels to minimize their footprint area. The other driving force is derived from the unique possibility of engineering the 1D NWs into more complex, as well as more functional, 3D nanostructures, such as helical springs and kinked probes, which are ideal nanostructures for developping advanced nanoelectromechanical system (NEMS), bio-sensing and manipulation applications. This Review will first examine the recent progresses made in the construction of 3D nano electronic devices, as well as the new fabrication and growth technologies established to enable an efficient 3D integration of the vertically standing or laterally stacked NW channels. Then, the different approaches to produce and tailor more sophisticated 3D helical springs or purposely-designed nanoprobes will be revisited, together with their applications in NEMS resonators, bio sensors and stimulators in neural system.

Soft-lock drawing of super-aligned carbon nanotube bundles for nanometre electrical contacts

The assembly of single-walled carbon nanotubes (CNTs) into high-density horizontal arrays is strongly desired for practical applications, but challenges remain despite myriads of research efforts. Herein, we developed a non-destructive soft-lock drawing method to achieve ultraclean single-walled CNT arrays with a very high degree of alignment (angle standard deviation of ~0.03°). These arrays contained a large portion of nanometre-sized CNT bundles, yielding a high packing density (~400 µm^-1) and high current carrying capacity (∼1.8 × 10⁸ A cm^-2). This alignment strategy can be generally extended to diverse substrates or sources of raw single-walled CNTs. Significantly, the assembled CNT bundles were used as nanometre electrical contacts of high-density monolayer molybdenum disulfide (MoS₂) transistors, exhibiting high current density (~38 µA µm^-1), low contact resistance (~1.6 kΩ µm), excellent device-to-device uniformity and highly reduced device areas (0.06 µm² per device), demonstrating their potential for future electronic devices and advanced integration technologies.

One-Dimensional van der Waals Heterostructures: A Perspective

As a new frontier in low-dimensional material research, van der Waals (vdW) heterostructures, represented by 2D heterostructures, have attracted tremendous attention due to their unique properties and potential applications. The emerging 1D heterostructures open new possibilities for the field with expectant unconventional properties and yet more challenging preparation pathways. This Perspective aims to give an overall understanding of the state-of-the-art growth strategies and fantastic properties of the 1D heterostructures and provide an outlook for further development based on the controlled preparation, which will bring up a variety of applications in high-performance electronic, optoelectronic, magnetic, and energy storage devices. A quick rise of the fundamentals and application study of 1D heterostructures is anticipated.

Growth of Semiconducting Single-Walled Carbon Nanotubes Array by Precisely Inhibiting Metallic Tubes Using ZrO2 Nanoparticles

Synthesis of high-quality single-walled carbon nanotubes arrays with pure semiconducting type is crucial for the fabrication of integrated circuits in nanoscale. However, the naturally grown carbon nanotubes usually have diverse structures and properties. Here the bicomponent catalyst using Au and ZrO₂ is designed and prepared. The Au nanoparticle serves as the catalysts for carbon feedstock cracking and facilitating the nucleation of carbon nanotubes, whereas the close-connected ZrO₂ forms a localized etching zone around Au by releasing lattice oxygen and to inhibit the nucleation of metallic carbon nanotubes precisely. The obtained single-walled carbon nanotubes array show a high semiconducting content of >96%, on the basis of good performance of field-effect transistor devices. And such building of localized etching zone is compatible with other catalyst systems as a universal and efficient method for the scalable production of semiconducting carbon nanotubes.

Advances and Frontiers in Single-Walled Carbon Nanotube Electronics

Single-walled carbon nanotubes (SWCNTs) have been considered as one of the most promising electronic materials for the next-generation electronics in the more Moore era. Sub-10 nm SWCNT-field effect transistors (FETs) have been realized with several performances exceeding those of Si-based FETs at the same feature size. Several industrial initiatives have attempted to implement SWCNT electronics in integrated circuit (IC) chips. Here, the recent advances in SWCNT electronics are reviewed from in-depth understanding of the fundamental electronic structures, the carrier transport mechanisms, and the metal/SWCNT contact properties. In particular, the subthreshold switching properties are highlighted for low-power, energy-efficient device operations. State-of-the-art low-power SWCNT-based electronics and the key strategies to realize low-voltage and low-power operations are outlined. Finally, the essential challenges and prospects from the material preparation, device fabrication, and large-scale ICs integration for future SWCNT-based electronics are foregrounded.

Building a Bridge for Carbon Nanotubes from Nanoscale Structure to Macroscopic Application

Through 30 years of research, researchers have gained a deep understanding of the synthesis, characteristics, and applications of carbon nanotubes (CNTs). However, up to now, there are still few industries using CNT as the leading material. The difficulty of CNTs to be applied in industry is the gap between the properties of CNT-based aggregates and those of a single carbon nanotube. Therefore, how to maintain the intrinsic properties of CNTs when they are assembled into aggregates is of great significance. Herein, we summarize and analyze the research status of CNT materials applied in different fields from proven techniques to potential industries, including energy storage, electronics, mechanical and other applications. For each application, the intrinsic properties of CNTs and the real performances of their aggregates are compared to figure out the key problems in CNT synthesis. Finally, we give an outlook for building a bridge for CNTs from nanoscale structure to macroscopic application, giving inspiration to researchers making efforts toward the real application of carbon nanotubes.

Confined Fe Catalysts for High-Density SWNT Arrays Growth: a New Territory for Catalyst-Substrate Interaction Engineering

Great efforts have been devoted to searching for efficient catalytic systems to produce ultra-high density single-walled carbon nanotube (SWNT) arrays, which lay the foundation for future electronic devices. However, one major obstacle for realizing high-density surface-aligned SWNT arrays is the poor stability of metal nanoparticles in chemical vapor deposition catalytic processes. Recently, Trojan catalyst has been reported to yield unprecedented high-density SWNT arrays with 130 SWNTs per µm on the a-plane (11-20) of the sapphire substrate. Herein, a concept of catalyst confinement effect is put forward to revealing the secret of remarkable growth efficiency of SWNT arrays by Trojan catalyst. Combined experimental and theoretical studies indicate that confinement of catalyst nanoparticles on discrete a-plane strips plays a key role in stabilizing the small nanoparticles. The highly dispersive and active states of catalysts are maintained, which promote the growth of super-dense SWNT arrays. By rationally designing the substrate reconstruction process, large areas of dense SWNT arrays (130 SWNTs per µm) covering the entire substrate are obtained. This approach may provide novel ideas for the synthesis of various high-density 1D nanomaterials.

Aligned 2D carbon nanotube liquid crystals for wafer-scale electronics

Semiconducting carbon nanotubes promise faster performance and lower power consumption than Si in field-effect transistors (FETs) if they can be aligned in dense arrays. Here, we demonstrate that nanotubes collected at a liquid/liquid interface self-organize to form two-dimensional (2D) nematic liquid crystals that globally align with flow. The 2D liquid crystals are transferred onto substrates in a continuous process generating dense arrays of nanotubes aligned within ±6°, ideal for electronics. Nanotube ordering improves with increasing concentration and decreasing temperature due to the underlying liquid crystal phenomena. The excellent alignment and uniformity of the transferred assemblies enable FETs with exceptional on-state current density averaging 520 μA μm⁻¹at only −0.6 V, and variation of only 19%. FETs with ion gel top gates demonstrate subthreshold swing as low as 60 mV decade⁻¹. Deposition across a 10-cm substrate is achieved, evidencing the promise of 2D nanotube liquid crystals for commercial semiconductor electronics.

Polarized Electroluminescence Emission in High-Performance Quantum Rod Light-Emitting Diodes via the Langmuir-Blodgett Technique

Due to their anisotropic structure, quantum rods (QRs) feature unique properties that differ from quantum dots, such as suppression of non-radiative Auger recombination and linearly polarized light emission. Despite many potential advantages, the progress of QR-based light-emitting diodes (QR-LEDs) is left behind due to the difficulty in aligning QRs. In this study, polarized electroluminescence emission is reported in high-performance QR-LEDs by employing the Langmuir-Blodgett (LB) technique. The adoption of the LB technique successfully produces a highly dense and smooth QR film with a high degree of alignment. As a result, the aligned QR films exhibit polarized photoluminescence emission with a degree of linear polarization of 2.1. Advantageous features of the LB technique, such as nondestructiveness, precise thickness control, and the nonnecessity of an additional matrix material, allow to fabricate QR-LEDs with the same procedure as the standard spin coating-based scheme. The device is fabricated via the LB technique, which shows excellent device performance, such as the low turn-on voltage of 1.8 V, peak luminance of 56 287 cd m^-2 , and peak external quantum efficiency (EQE) of 10.33%. Furthermore, these devices clearly exhibit an indication of polarized electroluminescence emission, which opens new opportunities for QRs in display technologies.

Synaptic transistors and neuromorphic systems based on carbon nano-materials

Carbon-based materials possessing a nanometer size and unique electrical properties perfectly address the two critical issues of transistors, the low power consumption and scalability, and are considered as a promising material in next-generation synaptic devices. In this review, carbon-based synaptic transistors were systematically summarized. In the carbon nanotube section, the synthesis of carbon nanotubes, purification of carbon nanotubes, the effect of architecture on the device performance and related carbon nanotube-based devices for neuromorphic computing were discussed. In the graphene section, the synthesis of graphene and its derivative, as well as graphene-based devices for neuromorphic computing, was systematically studied. Finally, the current challenges for carbon-based synaptic transistors were discussed.

Growth of Homogeneous High-Density Horizontal SWNT Arrays on Sapphire through a Magnesium-Assisted Catalyst Anchoring Strategy

In-situ growth of high-density single-walled carbon nanotube (SWNT) arrays with homogeneity is highly desirable for integrated circuits. However, disastrous migration and aggregation of catalyst nanoparticles on substrate has greatly limited the area of as-grown SWNT arrays. Herein, we develop a magnesium-assisted catalyst anchoring strategy to restrain catalyst nanoparticles sintering on substrate. Magnesium modification ameliorates sapphire surface by high temperature solid reaction and thus provides a stronger metal-support interaction (SMSI). Hereby, we realize the direct growth of high-density SWNT arrays that fully cover an entire 10×10 mm² substrate with the local highest density of ≈110 tubes μm^-1 using iron as catalyst. This strategy was also proven universal when employing solid carbide catalysts.

Materials Science Challenges to Graphene Nanoribbon Electronics

Graphene nanoribbons (GNRs) have recently emerged as promising candidates for channel materials in future nanoelectronic devices due to their exceptional electronic, thermal, and mechanical properties and chemical inertness. However, the adoption of GNRs in commercial technologies is currently hampered by materials science and integration challenges pertaining to synthesis and devices. In this Review, we present an overview of the current status of challenges, recent breakthroughs toward overcoming these challenges, and possible future directions for the field of GNR electronics. We motivate the need for exploration of scalable synthetic techniques that yield atomically precise, placed, registered, and oriented GNRs on CMOS-compatible substrates and stimulate ideas for contact and dielectric engineering to realize experimental performance close to theoretically predicted metrics. We also briefly discuss unconventional device architectures that could be experimentally investigated to harness the maximum potential of GNRs in future spintronic and quantum information technologies.

Chemical and topographical patterns combined with solution shear for selective-area deposition of highly-aligned semiconducting carbon nanotubes

Selective deposition of semiconducting carbon nanotubes (s-CNTs) into densely packed, aligned arrays of individualized s-CNTs is necessary to realize their potential in semiconductor electronics. We report the combination of chemical contrast patterns, topography, and pre-alignment of s-CNTs via shear to achieve selective-area deposition of aligned arrays of s-CNTs. Alternate stripes of surfaces favorable and unfavorable to s-CNT adsorption were patterned with widths varying from 2000 nm down to 100 nm. Addition of topography to the chemical contrast patterns combined with shear enabled the selective-area deposition of arrays of quasi-aligned s-CNTs (∼14°) even in patterns that are wider than the length of individual nanotubes (>500 nm). When the width of the chemical and topographical contrast patterns is less than the length of individual nanotubes (<500 nm), confinement effects become dominant enabling the selective-area deposition of much more tightly aligned s-CNTs (∼7°). At a trench width of 100 nm, we demonstrate the lowest standard deviation in alignment degree of 7.6 ± 0.3° at a deposition shear rate of 4600 s^-1, while maintaining an individualized s-CNT density greater than 30 CNTs μm^-1. Chemical contrast alone enables selective-area deposition, but chemical contrast in addition to topography enables more effective selective-area deposition and stronger confinement effects, with the advantage of removal of nanotubes deposited in spurious areas via selective lift-off of the topographical features. These findings provide a methodology that is inherently scalable, and a means to deposit spatially selective, aligned s-CNT arrays for next-generation semiconducting devices.

Structure, morphology and reversible hysteresis nature of human serum albumin (HSA) monolayer on water surface

Compression-decompression surface pressure (π)-specific molecular area (A) isotherm cycle of human serum albumin (HSA) monolayer is performed on water surface at four different subphase pH conditions, i.e., below and above the isoelectric point (pI ≈ 4.7) of HSA molecule. For all pH conditions, the decompression curve nearly follows the compression curve, however, at pH ≈ 5.0, hysteresis is observed at higher surface pressure. Out-of-plane structures and in-plane morphologies obtained from the X-ray reflectivity and AFM studies show that only the film thickness variation takes place with the change in surface pressure, which is also evidenced from the BAM images. With increase in surface pressure, the oblate-shaped HSA molecules start tilting making an angle with the water surface and as the monolayer is decompressed the molecules regain their initial untilted monomolecular configuration. Depending upon the subphase pH and local surface charge of the specific protein molecule, electrostatic repulsive interaction dominates over the van der Waals attraction and as a result decompression curve follows the compression curve as the molecules repel each other, however, closer to the isoelectric point as strength of the interactions reverses, a hysteresis is obtained at higher surface pressure and accordingly monolayer behaviour modifies on the water surface.

Multi-Functional Properties of MWCNT/PVA Buckypapers Fabricated by Vacuum Filtration Combined with Hot Press: Thermal, Electrical and Electromagnetic Shielding

The applications of pure multi-walled carbon nanotubes (MWCNTs) buckypapers are still limited due to their unavoidable micro/nano-sized pores structures. In this work, polyvinyl alcohol (PVA) was added to a uniform MWCNTs suspension to form MWCNT/PVA buckypapers by vacuum infiltration combined with a hot press method. The results showed an improvement in the thermal, electrical, and electromagnetic interference (EMI) shielding properties due to the formation of dense MWCNTs networks. The thermal and electrical properties rose from 1.394 W/m·k to 2.473 W/m·k and 463.5 S/m to 714.3 S/m, respectively. The EMI performance reached 27.08 dB. On the other hand, ABAQUS finite element software was used to simulate the coupled temperature-displacement performance. The electronic component module with buckypapers revealed a homogeneous temperature and thermal stress distribution. In sum, the proposed method looks promising for the easy preparation of multi-functional nanocomposites at low-cost.

Circularly Polarized Luminescence of Langmuir-Schaefer Films of Amphiphilic Stilbene Enhanced via Interfacial Reaction with Cyclodextrins

Two enantiomeric amphiphiles containing the stilbene moiety (l-StG and d-StG) were assembled into ordered Langmuir-Schaefer (LS) films through the air/water interface and their circularly polarized luminescence (CPL) was investigated. When the molecules were spread at the air/water interface, a monolayer with nanofiber structures was formed, which could be subsequently transferred onto solid substrates by the LS method. The LS films showed both circular dichroism (CD) and CPL, whose handedness was determined by the molecular chirality of the amphiphiles. When the amphiphilic molecules were spread on the aqueous subphases containing cyclodextrins (including α-CyD, β-CyD, or γ-CyD), similar nanofiber-featured films were formed. However, the CD and CPL showed different changes. When l-StG was spread on the cyclodextrins, both CD and CPL were enhanced. When d-StG was reacted with cyclodextrins, the CD signal decreased while the CPL was enhanced. It was suggested that the chirality cooperation and conflict between the point chirality from the amphiphilic stilbene and the cavity chirality of cyclodextrin led to the phenomenon. However, in any case, the immobilization of the stilbene by the cyclodextrins caused the enhancement of CPL.

Horizontal Single-Walled Carbon Nanotube Arrays: Controlled Synthesis, Characterizations, and Applications

Single-walled carbon nanotubes (SWNTs) emerge as a promising material to advance carbon nanoelectronics. However, synthesizing or assembling pure metallic/semiconducting SWNTs required for interconnects/integrated circuits, respectively, by a conventional chemical vapor deposition method or by an assembly technique remains challenging. Recent studies have shown significant scientific breakthroughs in controlled SWNT synthesis/assembly and applications in scaled field effect transistors, which are a critical component in functional nanodevices, thereby rendering the horizontal SWNT array an important candidate for innovating nanotechnology. This review provides a comprehensive analysis of the controlled synthesis, surface assembly, characterization techniques, and potential applications of horizontally aligned SWNT arrays. This review begins with the discussion of synthesis of horizontally aligned SWNTs with regulated direction, density, structure, and theoretical models applied to understand the growth results. Several traditional procedures applied for assembling SWNTs on target surface are also briefly discussed. It then discusses the techniques adopted to characterize SWNTs, ranging from electron/probe microscopy to various optical spectroscopy methods. Prototype applications based on the horizontally aligned SWNTs, such as interconnects, field effect transistors, integrated circuits, and even computers, are subsequently described. Finally, this review concludes with challenges and a brief outlook of the future development in this research field.

Unidirectional Langmuir-Blodgett-Mediated Alignment of Polyaniline-Functionalized Multiwalled Carbon Nanotubes for NH3 Gas Sensor Applications

Herein, we report the formation of well-aligned ultrathin films of polyaniline-functionalized multiwalled carbon nanotubes (PANI@MWCNTs) with a high orientational order over a macroscopic area by Langmuir-Blodgett (LB) technique and its enhanced ammonia gas sensing properties. During the interfacial assembly process, the PANI@MWCNTs gradually align to form small ordered blocks at the air-water interface, which further organize as a well-defined oriented monolayer. The orientation and alignment of PANI@MWCNTs in Langmuir films at the air-water interface were systematically studied as a function of interface temperature using transmission electron microscopic analysis. Surface functionalization of MWCNTs with polyaniline was found to overcome the 3D aggregation of CNTs leading to an oriented assembly of PANI@MWCNTs. The formation and stability of the compact monolayer/multilayer structures of PANI@MWCNTs-based LB films have been extensively studied using a π-A isotherm analysis and thermodynamic approach. For the first time, such highly oriented LB films of PANI-functionalized MWCNTs have been employed for ammonia gas sensing applications at room temperature. The sensor was found to exhibit outstanding sensitivity toward NH₃ at room temperature compared to random networks, which is attributed to the directed electron transport through the aligned PANI@MWCNTs. The ultrathin LB film allows fast analyte diffusion due to the adequate molecular accommodation in the oriented assembly of the active sensing layer. The large-scale alignment of PANI@MWCNTs demonstrated in this investigation would enable the fabrication of high-density MEMS (micro-electromechanical system)-based nanoscale sensor arrays for high-performance NH₃ gas sensor applications.

Langmuir films of low-dimensional nanomaterials

A large number of low-dimensional nanomaterials having different shapes and being dispersible in solvents open a fundamental question if there is a universal deposition technique for the monolayer formation. A monolayer formation of various nanomaterials at the air-water interface, also known as a Langmuir film, is a well-established technique even for the large group of the recently developed low-dimensional nanomaterials. In this review, we cover the monolayer formation of the zero-dimensional, one-dimensional and two-dimensional nanomaterials. Thanks to the formation of a Langmuir layer at the thermodynamic equilibrium, by using a suitable nanomaterial dispersion and subphase, the monolayers can be formed from all kinds of materials, ranging from the graphene oxide to the semiconducting quantum dots. In this review, we will discuss the basic requirements for the successful formation of monolayers and summarize the recent scientific advances in the field of Langmuir films.

Langmuir-Scheaffer Technique as a Method for Controlled Alignment of 1D Materials

A widely applicable method for aligning 1D materials, and in particular carbon nanotubes (CNTs), independent of their preparation would be very useful as the growth methods for these materials are substance-specific. Langmuir-Schaefer (LS) deposition could be such an approach for alignment, as it aligns a large number of 1D materials independently of the desired substrate. However, the mechanism and required conditions for alignment of 1D nanomaterials in a Langmuir trough are still unclear. Here we show, relying on numerical simulations of the Langmuir film compression, that the LS method is a powerful tool to achieve maximal alignment of 1D material in a controllable manner. In particular, 1D materials terminated with a suitable surfactant can align only if the velocity induced by the attraction between individual 1D entities is low enough relative to the flow speed. To validate this model, we achieved an efficient LS alignment of single-walled carbon nanotubes covered with a suitable surfactant relying on the numerical simulations. In situ polarized Raman microspectroscopy during the compression of Langmuir film revealed good quantitative agreement between the numerical simulations and the experiment. This suggests the applicability of the LS technique as a versatile method for the controlled alignment of 1D materials.

Clinically accurate diagnosis of Alzheimer's disease via multiplexed sensing of core biomarkers in human plasma

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder, affecting one in ten people aged over 65 years. Despite the severity of the disease, early diagnosis of AD is still challenging due to the low accuracy or high cost of neuropsychological tests and neuroimaging. Here we report clinically accurate and ultrasensitive detection of multiple AD core biomarkers (t-tau, p-tau₁₈₁, Aβ₄₂, and Aβ₄₀) in human plasma using densely aligned carbon nanotubes (CNTs). The closely packed and unidirectionally aligned CNT sensor array exhibits high precision, sensitivity, and accuracy, evidenced by a low coefficient of variation (<6%), a femtomolar-level limit of detection, and a high degree of recovery (>93.0%). By measuring the levels of t-tau/Aβ₄₂, p-tau₁₈₁/Aβ₄₂, and Aβ₄₂/Aβ₄₀ in clinical blood samples, the sensor array successfully discriminates the clinically diagnosed AD patients from healthy controls with an average sensitivity of 90.0%, a selectivity of 90.0%, and an average accuracy of 88.6%.

Detection of Alzheimer’s disease (AD) biomarkers from patients’ blood is challenging because these are present in very low concentrations in the plasma. Here the authors develop a sensor array of densely aligned single-walled carbon nanotubes for clinically accurate detection of femtomolar AD biomarkers in human plasma samples.

In-plane aligned assemblies of 1D-nanoobjects: recent approaches and applications

One-dimensional (1D) nanoobjects have strongly anisotropic physical properties which are averaged out and cannot be exploited in disordered systems. We reviewed the in plane alignment approaches and potential applications with perspectives shared.

Self-Limiting Assembly Approaches for Nanoadditive Manufacturing of Electronic Thin Films and Devices

Most electronics consist of functional thin films with tens of nanometer thicknesses. It is usually challenging to control the growth of these thin films using conventional solution-based approaches. Nanoadditive manufacturing, a method to deposit electronically desired molecules, polymers, or nanomaterials in a layer-by-layer (LbL) fashion, has emerged as a promising technique for the precise control of film growth and device fabrication. Here, basic principles of nanoadditive manufacturing approaches with self-limiting characteristics are summarized with a particular focus on Langmuir-Blodgett assembly and LbL assembly. Additively manufactured electronic thin films with properties of conductors, semiconductors, and dielectrics are reviewed, followed by a discussion of their application in various electronics, such as field-effect transistors, sensors, memory devices, photodetectors, light-emitting diodes, and electrochromic devices. Finally, challenges and future developments of these approaches are proposed. The resulting analysis reveals promising opportunities of nanoadditive manufacturing for the solution-based fabrication of electronic devices.

Aerosol-Jet-Printed Preferentially Aligned Carbon Nanotube Twin-Lines for Printed Electronics

The alignment of carbon nanotubes (CNTs) is of great importance for the fabrication of high-speed electronic devices such as a transistor as the electron mobilities can be greatly enhanced with aligned CNT architectures. Here, we report, for the first time, a methodology to obtain preferentially aligned CNT traces on a flexible polyimide substrate utilizing the high-resolution aerosol jet printing technique and evaporation-driven self-assembly process. A self-assembled twin-line of CNT ("coffee-ring" effect) is observed in the deposit patterns, and the field-emission scanning electron microscopy (FESEM) images reveal highly self-ordered CNT in the resulting CNT twin-line. Various aerosol jet parameters have been investigated to obtain printed tracks in the range of 30-80 μm and conductive tracks (single CNT twin-line width) in the range of 600-1500 nm. The smallest CNT twin-line obtained in this experiment is found to be approximately 16 μm using a suitable sheath-to-atomizer flow ratio. Image analysis of FESEM images confirms the formation of aligned CNT traces at the ink periphery. The effect of the line width on the degree of alignment of the CNT is studied and evaluated. The electrical resistance of the CNT trace is adjustable by controlling the number of print passes and print speed.

Solvent-Mediated Affinity of Polymer-Wrapped Single-Walled Carbon Nanotubes for Chemically Modified Surfaces

Semiconducting single-walled carbon nanotube (s-CNT) arrays are being explored for next-generation semiconductor electronics. Even with the multitude of alignment and spatially localized s-CNT deposition methods designed to control s-CNT deposition, fundamental understanding of the driving forces for s-CNT deposition is still lacking. The individual roles of the dispersant, solvent, target substrate composition, and the s-CNT itself are not completely understood because it is difficult to decouple deposition parameters. Here, we study poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6'-[2,2'-{bipyridine}])] (PFO-BPy)-wrapped s-CNT deposition from solution onto a chemically modified substrate. We fabricate various self-assembled monolayers (SAMs) to gain a greater understanding of substrate effects on PFO-BPy-wrapped s-CNT deposition. We observe that s-CNT deposition is dependent on both the target substrate and s-CNT dispersion solvent. To complement the experiments, molecular dynamics simulations of PFO-BPy-wrapped s-CNT deposition on two different SAMs are performed to obtain mechanistic insights into the effect of the substrate and solvent on s-CNT deposition. We find that the global free-energy minimum associated with favorable s-CNT adsorption occurs for a configuration in which the minimum of the solvent density around the s-CNT coincides with the minimum of the solvent density above a SAM-grafted surface, indicating that solvent structure near a SAM-grafted surface determines the adsorption free-energy landscape driving s-CNT deposition. Our results will help guide informative substrate design for s-CNT array fabrication in semiconductor devices.

Aqueous exfoliated graphene by amphiphilic nanocellulose and its application in moisture-responsive foldable actuators

Graphene is a promising material for diverse applications, such as in composites, optoelectronics, photovoltaic cells, and energy storage devices. However, high-yielding liquid exfoliation of good-quality graphene in high concentrations remains a challenge. In this study, amphiphilic 2,2,6,6-tetramethylpiperidin-1-yl-oxyl (TEMPO)-mediated cellulose nanofibrils (CNFs) were demonstrated in robust aqueous exfoliation of graphite into high quality graphene in high yields and stable dispersions with graphene concentration up to 1 mg mL-1. Over 50% of graphene flakes exfoliated were 3 layers or less, of which ca. 5% were monolayer, and another 47% were multilayers, leaving only 3% as un-exfoliated graphitic platelets. Outstanding yields up to 84.2% were achieved at an optimized 0.2 g g-1 graphite : CNF feed ratio. The dispersed graphitic flakes are stabilized by Coulomb repulsion from the surface bound charged CNFs. Aqueous graphene suspensions stabilized by CNFs were easily vacuum filtered into nanopapers that exhibited rapid moisture triggered motion and spontaneous recovery in the absence of moisture, resembling actions of biological motor cells in "shame plant" leaves. Such unique moisture responsive behavior is attributed to the highly accessible, charged CNF surfaces and the recovery is due to the inherently hydrophobic graphene. This facile aqueous exfoliating approach using amphiphilic CNFs as multi-functional exfoliating, dispersing and structural-forming agents for moisture-responsive graphene nanopaper opens up a large-area of potential applications toward biologically inspired sensors and actuators.

A Facile One-Step Approach for Constructing Multidimensional Ordered Nanowire Micropatterns via Fibrous Elastocapillary Coalescence

Nanowire (NW) based micropatterns have attracted research interests for their applications in electric microdevices. Particularly, aligning NWs represents an important process due to the as-generated integrated physicochemical advantages. Here, a facile and general strategy is developed to align NWs using fibrous elastocapillary coalescence of carbon nanotube arrays (ACNTs), which enables constructing multidimensional ordered NW micropatterns in one step without any external energy input. It is proposed that the liquid film of NW solution is capable of shrinking unidirectionally on the top of ACNTs, driven by the dewetting-induced elastocapillary coalescence of the ACNTs. Consequently, the randomly distributed NWs individually rotate and move into dense alignment. Meanwhile, the aggregating and bundling of ACNTs is helpful to produce carbon nanotube (CNT) yarns connecting neighboring bundles. Thus, a micropatterned NW network composed of a top-layer of horizontally aligned NWs and an under-layer of vertical ACNT bundles connected by CNT yarns is prepared, showing excellent performance in sensing external pressure with a sensitivity of 0.32 kPa^-1 . Moreover, the aligned NWs can be transferred onto various substrates for constructing electronic circuits. The strategy is applicable for aligning various NWs of Ag, ZnO, Al₂ O₃ , and even living microbes. The result may offer new inspiration for fabricating NW-based functional micropatterns.

Solution-processed thin films of semiconducting carbon nanotubes and their application to soft electronics

Semiconducting single-walled carbon nanotube (SWNT) networks are promising for use as channel materials in field-effect transistors (FETs) in next-generation soft electronics, owing to their high intrinsic carrier mobility, mechanical flexibility, potential for low-cost production, and good processability. In this article, we review the recent progress related to carbon nanotube (CNT) devices in soft electronics by describing the materials and devices, processing methods, and example applications in soft electronic systems. First, solution-processed semiconducting SWNT deposition methods along with doping techniques used to achieve stable complementary metal-oxide-semiconductor devices are discussed. Various strategies for developing high-performance SWNT-based FETs, such as the proper material choices for the gates, dielectrics, and sources/drains of FETs, and methods of improving FET performance, such as hysteresis repression in SWNT-based FETs, are described next. These SWNT-based FETs have been used in flexible, stretchable, and wearable electronic devices to realize functionalities that could not be achieved using conventional silicon-based devices. We conclude this review by discussing the challenges faced by and outlook for CNT-based soft electronics.

Solution-Processing of High-Purity Semiconducting Single-Walled Carbon Nanotubes for Electronics Devices

High-purity semiconducting single-walled carbon nanotubes (s-SWCNTs) are of paramount significance for the construction of next-generation electronics. Until now, a number of elaborate sorting and purification techniques for s-SWCNTs have been developed, among which solution-based sorting methods show unique merits in the scale production, high purity, and large-area film formation. Here, the recent progress in the solution processing of s-SWCNTs and their application in electronic devices is systematically reviewed. First, the solution-based sorting and purification of s-SWCNTs are described, and particular attention is paid to the recent advance in the conjugated polymer-based sorting strategy. Subsequently, the solution-based deposition and morphology control of a s-SWCNT thin film on a surface are introduced, which focus on the strategies for network formation and alignment of SWCNTs. Then, the recent advances in electronic devices based on s-SWCNTs are reviewed with emphasis on nanoscale s-SWCNTs' high-performance integrated circuits and s-SWCNT-based thin-film transistors (TFT) array and circuits. Lastly, the existing challenges and development trends for the s-SWCNTs and electronic devices are briefly discussed. The aim is to provide some useful information and inspiration for the sorting and purification of s-SWCNTs, as well as the construction of electronic devices with s-SWCNTs.

Science and applications of wafer-scale crystalline carbon nanotube films prepared through controlled vacuum filtration

Carbon nanotubes (CNTs) make an ideal one-dimensional (1D) material platform for the exploration of novel physical phenomena under extremely strong quantum confinement. The 1D character of electrons, phonons and excitons in individual CNTs features extraordinary electronic, thermal and optical properties. Since their discovery in 1991, they have been continuing to attract interest in various disciplines, including chemistry, materials science, physics and engineering. However, the macroscopic manifestation of 1D properties is still limited, despite significant efforts for decades. Recently, a controlled vacuum filtration method has been developed for the preparation of wafer-scale films of crystalline chirality-enriched CNTs, and such films have enabled exciting new fundamental studies and applications. In this review, we will first discuss the controlled vacuum filtration technique, and then summarize recent discoveries in optical spectroscopy studies and optoelectronic device applications using films prepared by this technique.