The selective growth of semiconducting single-walled carbon nanotubes (s-SWCNTs) is of great importance in many high-end applications represented by nanoelectronics. Here, we developed a general approach to grow horizontally aligned s-SWCNT arrays on stable temperature (ST)-cut quartz with bimetallic catalysts using carbon monoxide (CO) as both catalyst reductant and single component carbon feedstock under atmospheric pressure. The disproportionation of CO produces not only carbon species for SWCNT growth but also CO₂, which could act as an in-situ etchant to remove both amorphous carbon and metallic tubes. The employment of bimetallic catalyst and quartz substrate facilitates the selective etching by narrowing the diameter distribution of as-grown SWCNT arrays. At the optimized conditions, we realized the selective growth of horizontally aligned s-SWCNT arrays with the content above 97% using CoCu catalysts, confirmed by Raman characterization and electrical measurements of the fabricated field effect transistor devices. This CO-based process in selective growth of s-SWCNTs has demonstrated its feasibility and universality by the broad growth window and applicability for other bimetallic catalysts, such as FeCu and CoMn. It possesses a practical potential in obtaining semiconducting channel materials for the scalable fabrication of CNT-based devices.

In single molecule study, surface-enhanced Raman scattering (SERS) has the advantage of specifically providing structural information of the molecules targeted. The main challenge in single molecule SERS is developing reusable plasmonic substrates that ensures single molecule sensitivity and acquires intrinsic information of molecules. Here, we proposed a strategy to utilize single- walled carbon nanotubes (SWNTs) to construct SERS substrates. Employing ultrasonic spray pyrolysis, we prepared in situ polyhedral gold nanocrystals closely spaced and attached to nanotubes, ensuring valid hot spots formed along the tube-walls. With such SERS substrates, we proved the single molecule detection by the statistical analysis based on the natural abundance of isotopes. Since SWNTs provide non-chemical bonding adsorption sites, our SERS substrates are easily reusable and have a unique advantage of preserving the intrinsic property of the molecules detected. Using SWNTs to build SERS substrates may become a powerful general strategy in various static and dynamic studies of single molecules.

Bifunctional electrocatalysts with high activity toward both oxygen reduction and evolution reaction are highly desirable for rechargeable Zn-air batteries. Herein, a kind of carbon nanotube (CNT) supported single-site Fe-N-C catalyst was fabricated via pyrolyzing in-situ grown Fe-containing zeolitic imidazolate frameworks on CNTs. CNTs not only serve as the physical supports of the Fe-N-C active sites but also provide a conductive network to facilitate the fast electron and ion transfer. The as-synthesized catalysts exhibit a half-wave potential of 0.865 V for oxygen reduction reaction and a low overpotential of 0.442 V at 10 mA·cm^-2 for oxygen evolution, which is 310 mV smaller than that of Fe-N-C without CNTs. The rechargeable Zn-air batteries fabricated with such hybrid catalysts display a high peak power density of 182 mW·cm^-2 and an excellent cycling stability of over 1, 000 h at 10 mA·cm^-2, which outperforms commercial Pt-C and most of the reported catalysts. This facile strategy of combining single-site Metal-N-C with CNTs network is effective for preparing highly active bifunctional electrocatalysts.

Flexible supercapacitors (SCs) have attracted increasing attention as the power supply unit for portable/wearable electronics. Carbon nanotubes (CNTs) are promising candidate materials for flexible SC electrodes because of their outstanding mechanical property, high electrical conductivity, large surface area, and functionability. CNTs can assemble into various macroscopic materials with different dimensions. In this review, flexible CNT assemblies including 1D fibers, 2D films, and 3D aerogels and sponges are introduced with a focus on the design strategies and fabrication techniques. The recent developments and state-of-the-art applications of such structures as electrodes in flexible SCs are summarized based on device configurations including sandwiched, interdigital in-plane, and cable-type configurations. The flexible CNT-based electrodes have shown great advantages in bendability, stretchability and/or compressibility, as well as a long cycle lifetime. The current challenges and future research opportunities in this field are also discussed.

Solution processes have shown excellent potential for application to the growth of single-crystal materials. We have developed a confined-solution method for the preparation of single crystals with a controlled morphology. By confining the precursor solution within a micrometer-thick cavity and then controlling the saturation by adjusting the temperature gradient and fluid flow, high-quality CH₃NH₃PbBr₃ single crystals with tunable morphologies could be obtained. The morphologies of the CH₃NH₃PbBr₃ can be adjusted from sub-square centimeter-scale thin sheets that are square or rectangular, to one-dimensional wires with lengths in the order of centimeters, simply by changing the temperature. The thicknesses of the CH₃NH₃PbBr₃ sheets could be adjusted from hundreds of nanometers to tens of microns. The CH₃NH₃PbBr₃ sheets feature very clean surfaces with an atomic-scale roughness. This simple strategy provides a means of growing high-quality single crystals with clean surfaces, which realize high levels of performance when applied to devices.

Bismuth oxides are important battery materials owing to their ability to electrochemically react and alloy with Li, which results in a high capacity level, which substantially exceeds that of graphite anodes. However, this high Li-storage capability is often compromised by the poor electrochemical cyclability and rate capability of bismuth oxides. To address these challenges, in this study, we design a hybrid architecture composed of reduced graphene oxide (rGO) nanosheets decorated with ultrafine Bi₂O_2.33 nanodots (denoted as Bi₂O_2.33/rGO), based on the selective and controlled hydrolysis of a Bi precursor on graphene oxide and subsequent crystallization via solvothermal treatment. Because of its high conductivity, large accessible area, and inherent flexibility, the Bi₂O_2.33/rGO hybrid exhibits stable and robust Li storage (346 mA·h·g^-1 over 600 cycles at 10 C), significantly outperforming previously reported Bi-based materials. This superb performance indicates that decorating rGO nanosheets with ultrafine nanodots may introduce new possibilities for the development of stable and robust metal-oxide electrodes.

Owing to the unique conjugated structure, the chemical-reaction selectivity of single-walled carbon nanotubes (SWNTs) has attracted great attention. By utilizing the radial deformation of SWNTs caused by the strong interactions with the quartz lattice, we achieve an anomalous diameter-dependent reaction selectivity of quartz lattice-oriented SWNTs in treatment with iodine vapor; this is distinctly different from the widely reported and well accepted higher reaction activity in small-diameter tubes compared to large-diameter tubes. The radial deformation of SWNTs on quartz substrate is verified by detailed Raman spectroscopy and mappings in both G-band and radial breathing mode. Due to the strong interaction between SWNTs and the quartz lattice, large-diameter tubes present a larger degree of radial deformation and more delocalized partial electrons are distributed at certain sidewall sites with high local curvature. It is thus easier for the carbon–carbon bonds at these high-curvature sites on large-diameter tubes to break down during reaction. This anomalous reaction activity offers a novel approach for selective removal of small-bandgap large-diameter tubes.

Triuranium octoxide-reduced graphene oxide (U₃O₈/rGO) hybrids have been prepared by a two-step solution-phase method. The presence of GO is essential in order to obtain pure phase U₃O₈. The U₃O₈/rGO hybrids exhibited excellent electrocatalytic activity for the oxygen reduction reaction. The electron transfer number was calculated to be ~3.9 at -0.7 V (vs. Ag/AgCl) from the slope of the Koutecky-Levich plots. The U₃O₈/rGO hybrids were more stable than commercial Pt/C catalysts. Furthermore, when methanol was present, the U₃O₈/rGO hybrids still retained high activity. In addition, the U₃O₈/rGO hybrids can also catalyze the reduction of hydrogen peroxide.

Layered bismuth sulfide (Bi₂S₃) has emerged as an important type of Li-storage material due to its high theoretical capacity and intriguing reaction mechanism. The engineering and fabrication of Bi₂S₃ materials with large capacity and stable cyclability via a facile approach is essential, but still remains a great challenge. Herein, we employ a one-pot hydrothermal route to fabricate carbon-coated Bi₂S₃ nanomeshes (Bi₂S₃/C) as an efficient Li-storage material. The nanomeshes serve as a highly conducting and porous scaffold facilitating electron and ion transport, while the carbon coating layer provides flexible space for efficient reduction of mechanical strain upon electrochemical cycling. Consequently, the fabricated Bi₂S₃/C exhibits a high and stable capacity delivery in the 0.01-2.5 V region, notably outperforming previously reported Bi₂S₃ materials. It is able to discharge 472 mA·h·g^-1 at 120 mA·g^-1 over 50 full cycles, and to retain 301 mA·h·g^-1 in the 40th cycle at 600 mA·g^-1, demonstrating the potential of Bi₂S₃ as electrode materials for rechargeable batteries.

A facile catalyst-free one-step approach for the preparation of carbon nanotubes and graphene sheets at ambient pressure and ~ 230 ℃ has been developed. Carbon nanotubes and graphene sheets are prepared by reducing tetrachloroethylene with sodium in paraffin oil under reflux. The as-prepared products can be easily purified just by washing with common solvents. No metallic contaminants or other impurities exist in the products. The products show unique optical properties and may find various applications such as optical light attenuators and catalyst supports. This high yield and economical process presents a possible strategy for the large-scale production of carbon nanotubes and graphene sheets for future applications.