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Lithium cobalt oxide (LCO), the first commercialized cathode active material for lithium-ion batteries, is known for high voltage and capacity. However, its application has been limited by relatively low capacity and stability at high C-rates. Reducing particle size is considered one of the most straightforward and effective strategies to enhance ion transfer, thus increasing the rate performance. However, side reactions are simultaneously enhanced as the specific surface area increases. Herein, we investigate the impact of LCO particles with varying size distributions and optimize the particle size. To modulate the side reactions associated with particle size reduction, an ultrathin carbon nanotube film (UCNF) is introduced to coat the cathode surface. With this simple process and optimized particle size, the rate performance improves significantly, normal commercial LCO achieves 118 mA·h·g−1 at 3.0–4.3 V and 20 C (0.72 mA·h·cm−2), corresponding to power density of 8732 W·kg−1. This method is applied to high voltage as well, 152 mA·h·g−1 at 3.0–4.6 V and 20 C (0.99 mA·h·cm−2) was achieved with high-voltage LCO (HVLCO), corresponding to power density of 11,552 W·kg−1. The cycling stability is also enhanced, with the capacity retention maintaining more than 96% after 100 cycles at 0.1 C. For the first time, UCNF is demonstrated to suppress the excessive decomposition of the electrolytes and solvents by blocking electron injection/extraction between LCO and electrolyte solution. Our findings provide a simple method for improving LCO rate performance, especially at high C-rates. [ABSTRACT FROM AUTHOR]

Despite the ever-increasing demand of nanofillers for thermal enhancement of polymer composites with higher thermal conductivity and irregular geometry, nanomaterials like carbon nanotubes (CNTs) have been constrained by the nonuniform dispersion and difficulty in constructing effective three-dimensional (3D) conduction network with low loading and desired isotropic or anisotropic (specific preferred heat conduction) performances. Herein, we illustrated the in-situ construction of CNT based 3D heat conduction networks with different directional performances. First, to in-situ construct an isotropic percolated conduction network, with spherical cores as support materials, we developed a confined-growth technique for CNT-core sea urchin (CNTSU) materials. With 21.0 wt.% CNTSU loading, the thermal conductivity of composites reached 1.43 ± 0.13 W/(m·K). Secondly, with aligned hexagonal boron nitride (hBN) as an anisotropic support, we constructed CNT-hBN aligned networks by in-situ CNT growth, which improved the utilization efficiency of high density hBN and reduced the thermal interface resistance between matrix and fillers. With ~ 8.5 wt.% loading, the composites possess thermal conductivity up to 0.86 ± 0.14 W/(m·K), 374% of that for neat matrix. Due to the uniformity of CNTs in hBN network, the synergistic thermal enhancement from one-dimensional (1D) + two-dimensional (2D) hybrid materials becomes more distinct. Based on the detailed experimental evidence, the importance of purposeful production of a uniformly interconnected heat conduction 3D network with desired directional performance can be observed, particularly compared with the traditional direct-mixing method. This study opens new possibilities for the preparation of high-power-density electronics packaging and interfacial materials when both directional thermal performance and complex composite geometry are simultaneously required. [ABSTRACT FROM AUTHOR]

Compared with piezoresistive sensors, pressure sensors based on the contact resistance effect are proven to have higher sensitivity and the ability to detect ultra-low pressure, thus attracting extensive research interest in wearable devices and artificial intelligence systems. However, most studies focus on static or low-frequency pressure detection, and there are few reports on high-frequency dynamic pressure detection. Limited by the viscoelasticity of polymers (necessary materials for traditional vibration sensors), the development of vibration sensors with high frequency response remains a great challenge. Here, we report a graphene aerogel-based vibration sensor with higher sensitivity and wider frequency response range (2 Hz–10 kHz) than both conventional piezoresistive and similar sensors. By modulating the microscopic morphology and mechanical properties, the super-elastic graphene aerogels suitable for vibration sensing have been prepared successfully. Meanwhile, the mechanism of the effect of density on the vibration sensor's sensitivity is studied in detail. On this basis, the sensitivity, signal fidelity and signal-to-noise ratio of the sensor are further improved by optimizing the structure configuration. The developed sensor exhibits remarkable repeatability, excellent stability, high resolution (0.0039 g) and good linearity (non-linearity error < 0.8%) without hysteresis. As demos, the sensor can not only monitor low-frequency physiological signals and motion of the human body, but also respond to the high-frequency vibrations of rotating machines. In addition, the sensor can also detect static pressure. We expect the vibration sensor to meet a wider range of functional needs in wearable devices, smart robots, and industrial equipment. [ABSTRACT FROM AUTHOR]

Industrial production of single-chirality carbon nanotubes is critical for their applications in high-speed and low-power nanoelectronic devices, but both their growth and separation have been major challenges. Here, we report a method for industrial separation of single-chirality carbon nanotubes from a variety of raw materials with gel chromatography by increasing the concentration of carbon nanotube solution. The high-concentration individualized carbon nanotube solution is prepared by ultrasonic dispersion followed by centrifugation and ultrasonic redispersion. With this technique, the concentration of the as-prepared individualized carbon nanotubes is increased from about 0.19 mg/mL to approximately 1 mg/mL, and the separation yield of multiple single-chirality species is increased by approximately six times to the milligram scale in one separation run with gel chromatography. When the dispersion technique is applied to an inexpensive hybrid of graphene and carbon nanotubes with a wide diameter range of 0.8–2.0 nm, and the separation yield of single-chirality species is increased by more than an order of magnitude to the sub-milligram scale. Moreover, with present separation technique, the environmental impact and cost of producing single-chirality species are greatly reduced. We anticipate that this method promotes industrial production and practical applications of single-chirality carbon nanotubes in carbon-based integration circuits. Large-scale production of single-chirality carbon nanotubes has long been a major challenge. Here, authors report a simple, yet effective, method to increase the yield of gel chromatography separation of single-chirality carbon nanotubes by enabling significantly higher concentrations of raw nanotubes solution. [ABSTRACT FROM AUTHOR]

Establishing the relationship between the electrical transport properties of single-wall carbon nanotubes (SWCNTs) and their structures is critical for the design of high-performance SWCNT-based electronic and optoelectronic devices. Here, we systematically investigated the effect of the chiral structures of SWCNTs on their electrical transport properties by measuring the performance of thin-film transistors constructed by eleven distinct (n, m) single-chirality SWCNT films. The results show that, even for SWCNTs with the same diameters but different chiral angles, the difference in the on-state current or carrier mobility could reach an order of magnitude. Further analysis indicates that the electrical transport properties of SWCNTs have strong type and family dependence. With increasing chiral angle for the same-family SWCNTs, Type I SWCNTs exhibit increasing on-state current and mobility, while Type II SWCNTs show the reverse trend. The differences in the electrical properties of the same-family SWCNTs with different chiralities can be attributed to their different electronic band structures, which determine the contact barrier between electrodes and SWCNTs, intrinsic resistance and intertube contact resistance. Our present findings provide an important physical basis for performance optimization and application expansion of SWCNT-based devices. Single-wall carbon nanotubes have been reported in field effect transistors as a function of nanotube diameter, showing increasing current with increasing diameter. Su et al. show how the chiral structures of single-wall carbon nanotubes affect their electrical transport properties. [ABSTRACT FROM AUTHOR]

Increasing the concentration of single-wall carbon nanotubes (SWCNTs) is an effective method for enhancing their luminescence intensity. However, an increase in the concentration of SWCNTs would inevitably increase their reabsorption effect, degrading their luminescence efficiency. Herein, we systematically investigated variations in the photoluminescence (PL) intensity of (6,5) single-chirality SWCNTs while increasing their concentration. The results show that the PL intensity first increased to a maximum and then decreased with increasing concentration. Numerical analysis indicates that the concentration boundary corresponding to the maximum PL intensity was strongly dependent on the ratio of the optical absorbances of the SWCNTs at their excitation and emission wavelengths. According to this, statistical analysis by experimentally measuring the optical absorption spectra of 18 kinds of single-chirality SWCNTs shows that the concentration boundaries of SWCNTs were dependent upon their Types and diameters. The concentration boundary of Type I SWCNTs was higher than that of Type II SWCNTs, and the concentration boundaries of both Types increased with increasing diameter. These results provide important guidance for spectral characterization and applications in bioimaging and photoelectronic devices. [ABSTRACT FROM AUTHOR]

In this work, we quantitatively studied the intertube coupling of different (n, m)-sorted semiconducting single-wall carbon nanotubes (SWCNTs) on their photoluminescence (PL) efficiencies by precisely tuning the ratio of (9, 4) and (6, 5) SWCNTs in the mixture. A significant decrease in the PL intensity of (9, 4) SWCNTs was observed after mixing with (6, 5) species when fixing the (9, 4) concentration, which was confirmed to be caused by the absorption of incident photons and reabsorption of the emitted photons by the added (6, 5) species. By contrast, a similar decrease in the PL intensity of (6, 5) SWCNTs was also observed after mixing with the larger-diameter (9, 4) species. Different from that of (9, 4) SWCNTs, the PL decrease of (6, 5) SWCNTs was found to originate not only from photon absorption and reabsorption by the (9, 4) species but also from one-way exciton energy transfer (EET) from the (6, 5) SWCNTs to the larger-diameter (9, 4) SWCNTs. Both the experimental results and numerical simulations further demonstrated that increasing the concentration of mixed (9, 4) SWCNTs would enhance the effects of photon absorption and reabsorption and EET on the PL intensity of (6, 5) SWCNTs quantified by the decrease ratio of the (6, 5) PL intensity. Meanwhile, the influence of EET was found to be always weaker than that of photon absorption and reabsorption. We proposed that the observed EET between isolated SWCNTs in a surfactant solution is derived from their proximity due to Brownian motion. [ABSTRACT FROM AUTHOR]

In order to develop an excellent pseudocapacitor with both high specific capacitance and outstanding stretchability to match with other devices applicable in future wearable and bio-implantable systems, we focus our studies on three vital aspects: Stretchability of hybrid film electrodes, the interface between different components, and the integrated performance in stretchability and electrochemistry of supercapacitors based on single-walled carbon nanotube/polyaniline (SWCNT/PANI) composite films on pre-elongated elastomers. Owing to the moderate porosity, the buckled hybrid film avoids the cracking which occurs in conventional stretchable hybrid electrodes, and both a high specific capacitance of 435 F·g and a high strain tolerance of 140% have been achieved. The good SWCNT/PANI interfacial coupling and the reinforced solid electrolyte penetration structure enable the integrated pseudocapacitors to have stretch-resistant interfaces between different units and maintain a high performance under a stretching of 120% elongation, even after 1,000 cyclic elongations. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Research interest in ZnO nanostructures derives from their excellent luminescent properties and availability of low cost fabricating and processing, which hold promise for the development of electronic and optoelectronic nanodevices. In this review, we focus on the progress in synthesis, properties and nanodevices of ZnO nanorod (NR) arrays and nanotetrapods (NTPs). Recent work done by the authors are also presented. After a brief introduction to the controlled fabrication methods for the highly-ordered ZnO NR arrays and NTPs, we present some aspects of the fundamental properties, especially optical performance, of ZnO NRs/NTPs. Then, we provide an overview of the applications to functional nanodevices based on individual NR and NTP of ZnO. It is demonstrated that different morphologies of ZnO nanostructures have salient effects on their properties and applications. Although much progress has been achieved in the fundamental and applied investigations of ZnO NRs/NTPs over the past decade, many obstacles still remain, hampering further development in this field. Finally, some longstanding problems that warrant further investigation are addressed. [ABSTRACT FROM AUTHOR]

As a type of thin film, two dimensional (2D) reticulate architectures built of freestanding single-walled carbon nanotube (SWCNT) bundles are suitable for scalable integration into devices and nanocomposites for many applications. The superior properties of these films, such as optical transparency, unique electrical properties and mechanical flexibility, result not only from the outstanding properties of individual SWCNTs but also from the collective behavior of the individual tubes, with additional properties arising from the tube-tube interactions. In this review, the synthesis, structure and fundamental properties, such as conductivity, transparency, optical nonlinearity and mechanical performance, of 'freestanding SWCNT bundle network' thin films and nanocomposites, as well as their application as supercapacitors are highlighted. Some long-standing problems and topics warranting further investigation in the near future are addressed. [ABSTRACT FROM AUTHOR]

Random networks of single-walled carbon nanotubes (SWCNTs) were have been grown by chemical vapor deposition on silicon wafers and used for fabricating field-effect transistors (FETs) using symmetric Pd contacts and diodes using asymmetrical Pd and Sc contacts. For a short channel FET or diode with a channel length of about 1 μm or less, the device works in the direct transport regime, while for a longer channel device the transport mechanism changes to percolation. Detailed electronic and photovoltaic (PV) characterizations of these carbon nanotube (CNT) thin-film devices was carried out. While as-fabricated FETs exhibited typical p-type transfer characteristics, with a large current ON/OFF ratio of more than 10 when metallic CNTs were removed via a controlled breakdown, it was found that the threshold voltage for the devices was typically very large, of the order of about 10 V. This situation was greatly improved when the device was coated with a passivation layer of 12 nm HfO, which effectively moved the threshold voltages of both FET and diode back to center around zero or turned these device to their OFF states when no bias was applied on the gate. PV measurements were then made on the short channel diodes under infrared laser illumination. It was shown that under an illumination power density of 1.5 kW/cm, the device resulted in an open circuit voltage V = 0.21 V and a short circuit current I = 3.74 nA. Furthermore, we compared PV characteristics of CNT film diodes with different channel lengths, and found that the power transform efficiency decreased significantly when the device changed from the direct transport to the percolation regime. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The application of nanomaterial in cancer treatment is promising and intriguing. Anti-tumor immunotherapy has the potential to significantly improve the prognosis of cancer treatment, though the efficacy of immunotherapy generally needs further improvement. One way to improve the efficacy is using immune adjuvants, but the adjuvants for anticancer immunotherapy have to be more potent than for prophylactic vaccines. Here, we report that compared to conventional alum adjuvant, aluminum oxide nanoparticles (nano-alum) may further enhance the anticancer effects of an immunotherapy that employs tumor cell vaccine (TCV). The average tumor size tends to be lower in animals that receive the combinational treatment of nano-alum and TCV. The anticancer cytotoxicity by the lymphocytes was also significantly higher in the treatment group that received both TCV and nano-alum. These results suggest that nano-alum may potentially serve as a potent immune adjuvant and have prospective applications in anticancer immunotherapy. [ABSTRACT FROM AUTHOR]

Electrical transport properties of individual metallic double-walled carbon nanotubes (DWCNTs) were measured down to liquid helium temperature, and multi-stable conductance states were found in DWCNTs. At a certain temperature, DWCNTs can switch continuously between two or more electronic states, but below certain temperature, DWCNTs are stable only at one of them. The temperature for switching is always different from tube to tube, and even different from thermal cycle to cycle for the same tube. In addition to thermal activation, gate voltage scanning can also realize such switching among different electronic states. The multi-stable conductance states in metallic DWCNTs can be attributed to different Fermi level or occasional scattering centers induced by different configurations between their inner and outer tubes. [ABSTRACT FROM AUTHOR]

Reports a concept of the confined polaron. Two types of polaron in solids; Discussion on intrinsic polarons; Correlation between the polaron and the luminescence spectroscopy in porous silicon.

Very long and open aligned carbon nanotubes that reach about 2 mm long, an order of magnitude longer than previously reached, have been prepared by chemical vapor deposition over silica dioxide substrates on the surface, where iron/silica nano-composite particles are evenly positioned. The nanotubes are naturally opened at the bottom ends. The growth mechanism of the very long and openended nanotubes is also discussed. [ABSTRACT FROM AUTHOR]

The growth of carbon nanotubes from catalytic thermal decomposition of acetylene on fine iron particles has been studied. Electron microscopic images of the carbon nanotubes “as formed” and after annealing treatment are presented. Besides the ordinary carbon nanotubes which have been reported (S. Iijima, Nature, 354 (1991) 56), we have found, at first time, two other new kinds of carbon nanotubes: one is straight or curved nanotube with many irregular multi-layered diaphragms in the hollow core, in particular, the fringes of the wall of the tubes are not parallel to the axis of the tube; another one has many regular diaphragms (bamboo-like) which keep almost constant distance with each other. A model that postulates two steps growth of nanotubes from catalyst particles is proposed to explain the microstructure of the novel carbon nanotubes. [ABSTRACT FROM AUTHOR]

Large size C70 single crystals with the dimension of more than 5 mm are grown from the vapor phase by controlling nucleation. X-ray diffraction and electron diffraction confirm that in the C70 single crystal a phase of the hexagonal close-packed (hcp) structure coexists with a minor face-center-cubic (fcc) phase at room temperature. The morphologies and their formation mechanism of the C70 single crystals are investigated by means of scanning electron micrascopy and optical microscopy. The influence of growth conditions on the morphologies of C70 single crystals is discussed. [ABSTRACT FROM AUTHOR]

Sintering-free, dispersive, large area and high density carbon nanotubes(CNTs) were obtained in arc-discharge. Both the quality and the production of the CNTs were improved. SEM study showed that the dispersive CNTs intertwined and aligned randomly in the sample. The growth mechanism of the CNTs and the formation of the morphologies in the arc-discharge were discussed. [ABSTRACT FROM AUTHOR]

Carbon nanotubes were prepared by chemical vapor deposition (CVD) of hydrocarbon gas on various substrates. The effect of substrates on the growth, morphology and structure of carbon nanotubes were investigated. Aligned carbon nanotubes with high density and purity were achieved by CVD on mesoporous silica substrate. The Raman scattering of aligned carbon nanotubes was carried out, and the dependence of the phonon properties on the microstructure of the nanotubes has been discussed. [ABSTRACT FROM AUTHOR]

Presents information on a study which developed a two-dimensional structure of 1-nonanethiol-capped gold nanoparticles. Background on nanoparticles; Methodology; Results and discussion.

It is a great challenge to substantially improve the practical performance of flexible thermoelectric modules due to the absence of air-stable n-type thermoelectric materials with high-power factor. Here an excellent flexible n-type thermoelectric film is developed, which can be conveniently and rapidly prepared based on the as-grown carbon nanotube continuous networks with high conductivity. The optimum n-type film exhibits ultrahigh power factor of ∼1,500 μW m−1 K−2 and outstanding stability in air without encapsulation. Inspired by the findings, we design and successfully fabricate the compact-configuration flexible TE modules, which own great advantages compared with the conventional π-type configuration modules and well integrate the superior thermoelectric properties of p-type and n-type carbon nanotube films resulting in a markedly high performance. Moreover, the research results are highly scalable and also open opportunities for the large-scale production of flexible thermoelectric modules. [ABSTRACT FROM AUTHOR]