Shu Wan

Ultrahigh humidity sensitivity of graphene oxide

Humidity sensors have been extensively used in various fields, and numerous problems are encountered when using humidity sensors, including low sensitivity, long response and recovery times, and narrow humidity detection ranges. Using graphene oxide (G-O) films as humidity sensing materials, we fabricate here a microscale capacitive humidity sensor. Compared with conventional capacitive humidity sensors, the G-O based humidity sensor has a sensitivity of up to 37800% which is more than 10 times higher than that of the best one among conventional sensors at 15%–95% relative humidity. Moreover, our humidity sensor shows a fast response time (less than 1/4 of that of the conventional one) and recovery time (less than 1/2 of that of the conventional one). Therefore, G-O appears to be an ideal material for constructing humidity sensors with ultrahigh sensitivity for widespread applications.

Large-range Control of the Microstructures and Properties of Three-dimensional Porous Graphene

Graphene-based three-dimensional porous macrostructures are believed of great importance in various applications, e.g. supercapacitors, photovoltaic cells, sensors and high-efficiency sorbents. However, to precisely control the microstructures and properties of this material to meet different application requirements in industrial practice remains challenging. We herein propose a facile and highly effective strategy for large-range tailoring the porous architecture and its properties by a modified freeze casting process. The pore sizes and wall thicknesses of the porous graphene can be gradually tuned by 80 times (from 10 to 800 μm) and 4000 times (from 20 nm to 80 μm), respectively. The property experiences the changing from hydrophilic to hydrophobic, with the Youngs Modulus varying by 15 times. The fundamental principle of the porous microstructure evolution is discussed in detail. Our results demonstrate a very convenient and general protocol to finely tailor the structure and further benefit the various applications of porous graphene.

Highly enhanced performance of spongy graphene as an oil sorbent

This work demonstrates a brand-new spongy graphene with a highly enhanced performance as an oil sorbent. The absorption capacity of the new spongy graphene to chloroform reaches 616 times of its own weight, which is approximately 8 times higher than that in previous reports. The absorption capacity towards other organic chemicals is also greatly improved.

Microscopic bimetallic actuator based on a bilayer of graphene and graphene oxide

We present an actuator, consisting of a bilayer of graphene and graphene oxide, which allows us to exert forces in micromechanical systems that are at least 50 times higher than reported for other actuators of comparable size. The durability of such a device and stability during many cycles are demonstrated, and the related mechanism is discussed in detail.

Graphene and carbon-based nanomaterials as highly efficient adsorbents for oils and organic solvents

Abstract This paper provides a comprehensive review of recent progress in the synthesis and performance of graphene and carbon-based nanomaterials as efficient adsorbents for oils and organic solvents. Several advantages of these adsorbents are emphasized, including adjustable three-dimensional networks, high surface area, high chemical/thermal stability, high flexibility and elasticity, and extremely high surface hydrophobicity/ oleophilicity. Technical challenges are discussed, and future research directions are proposed.

Temperature sensing properties of the passive wireless sensor based on graphene oxide films

This paper presents a passive wireless temperature sensor with graphene oxide (GO) films as the sensing material. In this sensor a temperature sensitive capacitor is used in a LC tank circuit. The resonant frequency of the tank circuit changes with the temperature. The test results imply that the temperature sensor based on graphene oxide films with proper concentration provides a sensitivity of 59.3 kHz /°C from -C40°C to 0 °C and 46.1 kHz /°C from 10°C to 60°C. The relationship between the sensing properties and dispersion concentrations is also studied. The measured results imply that the sensor based on GO films with proper concentration shows monotonic relationship over a certain temperature range between the sensing resonant frequency and temperature.

Ultra-Thin Electro-Spun PAN Nanofiber Membrane for High-Efficient Inhalable PM2.5 Particles Filtration

In this work, we introduce a synthesis method for a nanofiber membrane made of polyacrylonitrile and verify its filtration ability with micron-size particles. The polyacrylonitrile nanofiber membrane was produced by electro-spun technique with a thickness less than 0.2 mm. The filtration experimental result from micron-size particle penetration proved that after 60-min deposition, the polyacrylonitrile nanofiber membrane successfully filtrated ~99% micron-size particles in solution. We found that uniform morphology, consistent nanofiber diameter without disordered beads will lead to a better filtration performance. This finding will provide a low-cost, environmental-friendly and straightforward filtration approach for future PM2.5 elimination in an aqueous and harsh environment.

A facile strategy for rapid preparation of graphene spongy balls

Porous three dimensional (3D) graphene macrostructures have demonstrated the potential in versatile applications in recent years, including energy storage, sensors, and environment protection, etc. However, great research attention has been focused on the optimization of the structure and properties of graphene-based materials. Comparatively, there are less reports on how to shape 3D graphene macrostructures rapidly and effortlessly, which is critical for mass production in industry. Here, we introduce a facile and efficient method, low temperature frying to form graphene-based spongy balls in liquid nitrogen with a yield of ~400 balls min−1. Moreover, the fabrication process can be easily accelerated by using multi pipettes working at the same time. The graphene spongy balls show energy storage with a specific capacitance of 124 F g−1 and oil adsorbing with a capacity of 105.4 times its own weight. This strategy can be a feasible approach to overcome the low efficiency in production and speed up the development of porous 3D graphene-based macrostructures in industrial applications.