Surfactant‐Free Sub‐2 nm Ultrathin Triangular Gold Nanoframes

Ultrathin triangular gold nanoframes are synthesized in high yield through selective gold deposition on the edges of triangular silver nanoprisms and subsequent silver etching with mild wet etchants. These ultrathin gold nanoframes are surfactant‐free with tailorable ridge thickness from 1.8 to 6 nm and exhibit adjustable and distinct surface plasmon resonance bands in the visible and near‐IR region. In comparison, etching of the nanoprism template by galvanic replacement can only create frame structures with much thicker ridges, which have much lower catalytic activity for 4‐nitrophenol reduction than the ultrathin gold nanoframes.     

Mesh‐Like Carbon Nanosheets with High‐Level Nitrogen Doping for High‐Energy Dual‐Carbon Lithium‐Ion Capacitors

Li‐ion capacitors (LICs) have demonstrated great potential for bridging the gap between lithium‐ion batteries and supercapacitors in electrochemical energy storage area. The main challenge for current LICs (contain a battery‐type anode as well as a capacitor‐type cathode) lies in circumventing the mismatched electrode kinetics and cycle degradation. Herein, a mesh‐like nitrogen (N)‐doped carbon nanosheets with multiscale pore structure is adopted as both cathode and anode for a dual‐carbon type of symmetric LICs to alleviate the above mentioned problems via a facile and green synthesis approach. With rational design, this dual‐carbon LICs exhibits a broad high working voltage window (0–4.5 V), an ultrahigh energy density of $218.4\mathrm{Wh}{\mathrm{kg}}^{–1}{}_{\mathrm{electrodes}}$ ( $229.8\mathrm{Wh}{\mathrm{L}}^{–1}{}_{\mathrm{electrodes}}$), the highest power density of $22.5\mathrm{kW}{\mathrm{kg}}^{–1}{}_{\mathrm{electrodes}}$ ( $23.7\mathrm{kW}{\mathrm{L}}^{–1}{}_{\mathrm{electrodes}}$) even under an ultrahigh energy density of $97.5\mathrm{Wh}{\mathrm{kg}}^{–1}{}_{\mathrm{electrodes}}$ ( $102.6\mathrm{Wh}{\mathrm{L}}^{–1}{}_{\mathrm{electrodes}}$), as well as reasonably good cycling stability with capacity retention of 84.5% (only 0.0016% capacity loss per cycle) within 10 000 cycles under a high current density of 5 A g^?1. This study provides an efficient method and option for the development of high performance LIC devices.     

Efficient Metal‐Free Electrocatalysts from N‐Doped Carbon Nanomaterials: Mono‐Doping and Co‐Doping

N‐doped carbon nanomaterials have rapidly grown as the most important metal‐free catalysts in a wide range of chemical and electrochemical reactions. This current report summarizes the latest advances in N‐doped carbon electrocatalysts prepared by N mono‐doping and co‐doping with other heteroatoms. The structure–performance relationship of these materials is subsequently rationalized and perspectives on developing more efficient and sustainable electrocatalysts from carbon nanomaterials are also suggested.     

Carbon Nanotube Field‐Effect‐Transistor‐Based Biosensors

There is an explosive interest in 1D nanostructured materials for biological sensors. Among these nanometer‐scale materials, single‐walled carbon nanotubes (SWNTs) offer the advantages of possible biocompatibility, size compatibility, and sensitivity towards minute electrical perturbations. In particular, because of these inherent qualities, changes in SWNT conductivity have been explored in order to study the interaction of biomolecules with SWNTs. This Review discusses these interactions, with a focus on carbon nanotube field‐effect transistors (NTFETs). Recent examples of applications of NTFET devices for detection of proteins, antibody–antigen assays, DNA hybridization, and enzymatic reactions involving glucose are summarized. Examples of complementary techniques, such as microscopy and spectroscopy, are covered as well.     

Double‐Walled Carbon Nanotube Processing

Single‐walled carbon nanotubes (SWCNTs) have been the focus of intense research, and the body of literature continues to grow exponentially, despite more than two decades having passed since the first reports. As well as extensive studies of the fundamental properties, this has seen SWCNTs used in a plethora of applications as far ranging as microelectronics, energy storage, solar cells, and sensors, to cancer treatment, drug delivery, and neuronal interfaces. On the other hand, the properties and applications of double‐walled carbon nanotubes (DWCNTs) have remained relatively under‐explored. This is despite DWCNTs not only sharing many of the same unique characteristics of their single‐walled counterparts, but also possessing an additional suite of potentially advantageous properties arising due to the presence of the second wall and the often complex inter‐wall interactions that arise. For example, it is envisaged that the outer wall can be selectively functionalized whilst still leaving the inner wall in its pristine state and available for signal transduction. A similar situation arises in DWCNT field effect transistors (FETs), where the outer wall can provide a convenient degree of chemical shielding of the inner wall from the external environment, allowing the excellent transconductance properties of the pristine nanotubes to be more fully exploited. Additionally, DWCNTs should also offer unique opportunities to further the fundamental understanding of the inter‐wall interactions within and between carbon nanotubes. However, the realization of these goals has so far been limited by the same challenge experienced by the SWCNT field until recent years, namely, the inherent heterogeneity of raw, as‐produced DWCNT material. As such, there is now an emerging field of research regarding DWCNT processing that focuses on the preparation of material of defined length, diameter and electronic type, and which is rapidly building upon the experience gained by the broader SWCNT community. This review describes the background of the field, summarizing some relevant theory and the available synthesis and purification routes; then provides a thorough synopsis of the current state‐of‐the‐art in DWCNT sorting methodologies, outlines contemporary challenges in the field, and discusses the outlook for various potential applications of the resulting material.