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Biological systems are composed of hierarchical structures made of a large number of proteins. These structures are highly sophisticated and challenging to replicate using artificial synthesis methods. To exploit these structures in materials science, biotemplating is used to achieve biocomposites that accurately mimic biological structures and impart functionality of inorganic materials, including electrical conductivity. However, the biological scaffolds used in previous studies are limited to stereotypical and simple morphologies with little synthetic diversity because of a lack of control over their morphologies. This study proposes that the specific protein assemblies within the cell‐derived extracellular matrix (ECM), whose morphological features are widely tailorable, can be employed as versatile biotemplates. In a typical procedure, a fibrillar assembly of fibronectin—a constituent protein of the ECM—is metalized through an antibody‐guided biotemplating approach. Specifically, the antibody‐bearing nanogold is attached to the fibronectin through antibody–antigen interactions, and then metals are grown on the nanogold acting as a seed. The biomimetic structure can be adapted for hydrogen production and sensing after improving its electrical conductivity through thermal sintering or additional metal growth. This study demonstrates that cell‐derived ECM can be an attractive option for addressing the diversity limitation of a conventional biotemplate. [ABSTRACT FROM AUTHOR]

To realize the development of high‐performance electrodes materials, real‐time observation tool that can visualize dynamical changes of electrode materials upon lithiation and sodiation is highly critical. Recently, in situ transmission electron microscopy (TEM) has gained much attraction as it provides rich information on both phase and morphological transitions of electrode materials upon lithiation and sodiation in an atomic scale. Nevertheless, two significant limitations are present for current in situ TEM study: i) most of the in situ TEM experiments use a specially designed TEM holder, which is costly and suitable for use in only selective types of TEM; and ii) recently developed in situ TEM techniques with no applied bias have inherent limitations in the size of the sample (difficult for a size above 50 nm). Overcoming these two aforementioned issues, bias‐free graphene solid cells (GSCs) are now introduced, which can conduct real‐time observation of electrode materials in any size dimensions and morphologies without using bias. In this work, dynamical changes of hollow SnO2 nanotubes (NTs) are visualized upon lithiation and sodiation in real time using GSCs, where rich information is obtained on the morphology‐dependent, ion‐dependent characteristics of dynamical changes. [ABSTRACT FROM AUTHOR]

Flexible and mechanically robust gas sensors are the key technologies for wearable and implantable electronics. Herein, the authors demonstrate the high-performance, flexible nitrogen dioxide (NO2) chemiresistors using a series of n-type conjugated polymers (CPs: PNDIT2/IM-x) and a polymer dopant (poly(ethyleneimine), PEI). Imine double bonds (C = N) are incorporated into the backbones of the CPs with different imine contents (x) to facilitate strong and selective interactions with NO2. The PEI provides doping stability, enhanced electrical conductivity, and flexibility. As a result, the NO2 sensors with PNDIT2/IM-0.1 and PEI (1:1 by weight ratio) exhibit outstanding sensing performances, such as excellent sensitivity (𝚫R/Rb = 240%@1 ppm), ultralow detection limit (0.1 ppm), high selectivity (𝚫R/Rb < 8%@1 ppm of interfering analytes), and high stability, thereby outperforming other state-of-the-art CP-based chemiresistors. Furthermore, the thin film of PNDIT2/IM-0.1 and PEI blend is stretchable and mechanically robust, providing excellent flexibility to the NO2 sensors. Our study contributes to the rational design of high-performance flexible gas sensors. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) doping and reduction allow for physicochemical property modification to suit practical application needs. Herein, the challenge of simultaneous low‐thermal‐budget heteroatom doping of GO and its reduction in ambient air is addressed through the synthesis of B‐doped reduced GO (B@rGO) by flash irradiation of boric acid loaded onto a GO support with intense pulsed light (IPL). The effects of light power and number of shots on the in‐depth sequential doping and reduction mechanisms are investigated by ex situ X‐ray photoelectron spectroscopy and direct millisecond‐scale temperature measurements (temperature >1600 °C, < 10‐millisecond duration, ramping rate of 5.3 × 105 °C s−1). Single‐flash IPL allows the large‐scale synthesis of substantially doped B@rGO (≈3.60 at% B) to be realized with a thermal budget 106‐fold lower than that of conventional thermal methods, and the prepared material with abundant B active sites is employed for highly sensitive and selective room‐temperature NO2 sensing. Thus, this work showcases the great potential of optical annealing for millisecond‐scale ultrafast reduction and heteroatom doping of GO in ambient air, which allows the tuning of multiple physicochemical GO properties. [ABSTRACT FROM AUTHOR]

Conductive porous materials having a high surface reactivity offer great promise for a broad range of applications. However, a general and scalable synthesis of such materials remains challenging. In this work, the facile synthesis of catalytic metal nanoparticles (NPs) embedded in 2D metal–organic frameworks (MOFs) is reported as highly active and conductive porous materials. After the assembly of 2D conductive MOFs (C‐MOFs), i.e., Cu3(hexahydroxytriphenylene)2 [Cu3(HHTP)2], Pd or Pt NPs are functionalized within the cavities of C‐MOFs by infiltration of metal ions and subsequent reduction. The unique structure of Cu3(HHTP)2 with a cavity size of 2 nm confines the bulk growth of metal NPs, resulting in ultra‐small (≈2 nm) and well‐dispersed metal NPs loaded in 2D C‐MOFs. The Pd or Pt NPs‐loaded Cu3(HHTP)2 exhibits remarkably improved NO2 sensing performance at room temperature due to the high reactivity of catalytic metal NPs and the high porosity of C‐MOFs. The catalytic effect of Pd and Pt NPs on NO2 sensing of Cu3(HHTP)2, in terms of reaction rate kinetics and activation energy, is demonstrated. [ABSTRACT FROM AUTHOR]