Jiangyu Rao

Graphene‐Skeleton Heat‐Coordinated and Nanoamorphous‐Surface‐State Controlled Pseudo‐Negative‐Photoconductivity of Tiny SnO2 Nanoparticles

SnO2 nanoparticles display a pseudo-negative-photoconductivity (PsdNPC) effect, which shows that their resistance increases under light irradiation via a heating effect. The PsdNPC originates from intensive electron scattering of the nanoamorphous surface state of the SnO2 nanoparticles, resulting in a small inner current and a large absorption of moisture, leading to a large surface current. Graphene as the inner skeleton can shorten the response and recovery times.

Highly Self-Healable 3D Microsupercapacitor with MXene–Graphene Composite Aerogel

High-performance microsupercapacitors (MSCs) with three-dimensional (3D) structure provide an effective approach to improve the ability of energy storage. Because the electrodes with 3D structure are generally easily destroyed under mechanical deformation in practical applications, we fabricated a self-healable 3D MSC consisting of MXene (Ti3C2T x)-graphene (reduced graphene oxide, rGO) composite aerogel electrode by wrapping it with a self-healing polyurethane as an outer shell. The MXene-rGO composite aerogel combining large specific surface area of rGO and high conductivity of the MXene can not only prevent the self-restacking of the lamella structure but also resist the poor oxidization of MXene to a degree. The MSC based on a 3D MXene-rGO aerogel delivers a large area specific capacitance of 34.6 mF cm-2 at a scan rate of 1 mV s-1 and an outstanding cycling performance with a capacitance retention up to 91% over 15 000 cycles. The 3D MSC presents an excellent self-healing ability with specific capacitance retention of 81.7% after the fifth healing. The preparation of this self-healable 3D MSC can provide a method for designing and manufacturing next-generation long-life multifunctional electronic devices further to meet the requirements of sustainable development.

Piezoresistive Pressure Sensor Based on Synergistical Innerconnect Polyvinyl Alcohol Nanowires/Wrinkled Graphene Film

Piezoresistive sensor is a promising pressure sensor due to its attractive advantages including uncomplicated signal collection, simple manufacture, economical and practical characteristics. Here, a flexible and highly sensitive pressure sensor based on wrinkled graphene film (WGF)/innerconnected polyvinyl alcohol (PVA) nanowires/interdigital electrodes is fabricated. Due to the synergistic effect between WGF and innerconnected PVA nanowires, the as-prepared pressure sensor realizes a high sensitivity of 28.34 kPa-1 . In addition, the device is able to discern lightweight rice about 22.4 mg (≈2.24 Pa) and shows excellent durability and reliability after 6000 repeated loading and unloading cycles. What is more, the device can detect subtle pulse beat and monitor various human movement behaviors in real-time.

3D Synergistical MXene/Reduced Graphene Oxide Aerogel for a Piezoresistive Sensor

A piezoresistive sensor based on ultralight and superelastic aerogel is reported to fabricate MXene/reduced graphene oxide (MX/rGO) hybrid 3D structures and utilize their pressure-sensitive characteristics. The MX/rGO aerogel not only combines the rGOs large specific surface area and the MXenes (Ti3C2 T x) high conductivity but also exhibits rich porous structure, which leads to performance better than that of single-component rGO or MXene in terms of the pressure sensor. The large nanosheets of rGO can prevent the poor oxidization of MXene by wrapping MXene inside the aerogel. More importantly, the piezoresistive sensor based on the MX/rGO aerogel shows extremely high sensitivity (22.56 kPa-1), fast response time (<200 ms), and good stability over 10 000 cycles. The piezoresistive sensor based on the MX/rGO hybrid 3D aerogel can easily capture the signal below 10 Pa, thus clearly testing the pulse of an adult at random. Based on its superior performance, it also demonstrates potential applications in measuring pressure distribution, distinguishing subtle strain, and monitoring healthy activity.

A high performance wire-shaped flexible lithium-ion battery based on silicon nanoparticles within polypyrrole/twisted carbon fibers

Currently, mechanically flexible and strong batteries are desired for the development of bendable and portable devices. To meet this requirement, a simple and scalable synthesis of the anode for flexible wire-shaped lithium-ion batteries has been developed by a facile one-step in situ polymerization method. Polypyrrole was found to grow on the surface of Si nanoparticles and attach to twisted carbon fibers. The formed cross-linked structure of Si/PPy along with carbon fiber substrate offers a consecutive electron transport network and a porous structure to adjust large volumetric changes of Si particles during charging and discharging processes. On fabricating the wire-shaped Li-ion battery, the interconnected Si/PPy/CF hybrid electrode was found to offer an excellent performance of 3.9% capacity decrease after the flexibility test, a greatly improved cycling capacity of 2287 mA h g−1 and a capacity retention of about 75% after 100 cycles of the half-cell test. The all-wet methodology may provide a promising route for a new scalable way to produce applicable wire-shaped electrode in battery fabrication.

Vertical finger-like asymmetric supercapacitors for enhanced performance at high mass loading and inner integrated photodetecting systems

Herein, a vertical finger-like asymmetric supercapacitor (VFASC) comprising a reduced graphene oxide–manganese dioxide–polypyrrole (RGO–MnO2–PPy) positive electrode and reduced graphene oxide–molybdenum trioxide (RGO–MoO3) negative electrode was fabricated for the first time. The relationship between specific capacitance and mass loading of the VFASC was systematically studied. To our surprise, contrary to the general problem faced by supercapacitors, the specific capacitance of VFASC increased with an increase in the mass loading of the electrode. Furthermore, as the VFASC supplied a potential and MoO3 guaranteed photodetection capacity, the VFASC also acted as a photodetector with excellent sensitivity for the detection of white light without the use of additional external connected systems. This study presents an essential strategy for the preparation of high performance supercapacitors with high mass loading, low production cost, energy efficiency, space saving and simple integrated photodetection systems.

Bandgap-graded ZnO/(CdS)1−x (ZnS) x coaxial nanowire arrays for semiconductor-sensitized solar cells

Bandgap-graded ZnO/(CdS)1−x (ZnS) x (0 x 1) coaxial nanowire arrays on transparent conducting oxide substrates have been successfully fabricated by a facile two-step-approach, combining hydrothermal method and successive ion exchange reactions. Energy-dispersive x-ray spectroscopy elemental analysis suggests that the shells are composed of (CdS)1−x (ZnS) x double-layer structures, which are thoroughly and tightly synthesized on the ZnO cores, and play the role of sensitizers. The as-prepared ZnO/(CdS)1−x (ZnS) x coaxial nanowire arrays are demonstrated to be controllably adjusted in their optical absorption from ultraviolet to green via compositional effect, and are promising electrodes for semiconductor-sensitized solar cells. The photoelectrode based on the ZnO/CdS coaxial nanowire array shows good performance with power conversion efficiency of 2.093%, a short-circuit current density 7.733 mA cm−2, and an open-circuit voltage 0.536 V.

A flexible and highly sensitive pressure sensor based on elastic carbon foam

In this paper, we fabricate a flexible elastic carbon foam (ECF)-based pressure sensor by direct carbonization of melamine foams (MF) at 800 °C without using any metal catalyst. The carbonized ECF is composed of a unique 3D interconnected concave triangular carbon network with a fraction of cracked carbon microfibers, and displays abundant micro and meso-porosity. We select the ECF as a sensing material due to its conductive and elastic features, and make a piezoresistive sensor with ultrahigh sensitivity (100.29 kPa−1) and reproducible sensing (11 000 cycles) characteristics. Moreover, the pressure sensor is able to distinguish a large pressure range from as low as 3 Pa to 10 kPa. The cheap raw materials, simple fabrication process and satisfactory performance of the pressure sensor make it a promising device for electronic monitoring systems in industrial detection, human motion monitoring and so on.