Yongchao Tang

Highly Stretchable and Ultrasensitive Strain Sensor Based on Reduced Graphene Oxide Microtubes-Elastomer Composite.

Strain sensors with excellent flexibility, stretchability, and sensitivity have attracted increasing interests. In this paper, a highly stretchable and ultrasensitive strain sensor based on reduced graphene oxide microtubes-elastomer is fabricated by a template induced assembly and followed a polymer coating process. The sensors can be stretched in excess of 50% of its original length, showing long-term durability and excellent selectivity to a specific strain under various disturbances. The sensitivity of this sensor is as high as 630 of gauge factor under 21.3% applied strain; more importantly, it can be easily modulated to accommodate diverse requirements. Implementation of the device for gauging muscle-induced strain in several biological systems shows reproducibility and different responses in the form of resistance or current change. The developed strain sensors show great application potential in fields of biomechanical systems, communications, and other related areas.

Highly flexible heparin-modified chitosan/graphene oxide hybrid hydrogel as a super bilirubin adsorbent with excellent hemocompatibility

As a pathogenic toxin, bilirubin is generally removed from blood by hemoperfusion for the remission of liver disease or to gain time for patients waiting for liver transplantation. However, the development of bilirubin adsorbents with excellent mechanical properties, adsorption performance and hemocompatibility is still a considerable challenge. In this work, a heparin-modified chitosan/graphene oxide hybrid hydrogel (hep-CS/GH) has been developed for bilirubin adsorption using a lyophilization-neutralization-modification strategy. The as-prepared hybrid hydrogel displayed a unique foam-like porous structure and excellent mechanical flexibility. It was revealed that the incorporation of graphene oxide into the chitosan matrix enhanced both the compressive strength and the Youngs modulus of the hybrid hydrogel, as well as its adsorption capacity for bilirubin. The maximum adsorption capacity of hep-CS/GH for bilirubin was 92.59 mg g-1, according to the Langmuir isotherm model. It was demonstrated that hep-CS/GH successfully competed with albumin, and could effectively adsorb bilirubin from a bilirubin-enriched serum. After the hydrogel was modified with heparin, protein adsorption, platelet adhesion and hemolysis were reduced, and the plasma clotting time was prolonged from 4.1 to 23.6 min, indicating the superior hemocompatibility of hep-CS/GH. Therefore, this study may pave the way for improving the performance of the adsorbent in removing blood toxins.

Flexible Paper-like Free-Standing Electrodes by Anchoring Ultrafine SnS2 Nanocrystals on Graphene Nanoribbons for High-Performance Sodium Ion Batteries

Ultrafine SnS2 nanocrystals-reduced graphene oxide nanoribbon paper (SnS2-RGONRP) has been created by a well-designed process including in situ reduction, evaporation-induced self-assembly, and sulfuration. The as-formed SnS2 nanocrystals possess an average diameter of 2.3 nm and disperse on the surface of RGONRs uniformly. The strong capillary force formed during evaporation leads to a compact assembly of RGONRs to give a flexible paper structure with a high density of 0.94 g cm-3. The as-prepared SnS2-RGONRP composite could be directly used as free-standing electrode for sodium ion batteries. Due to the synergistic effects between the ultrafine SnS2 nanocrystals and the conductive, tightly connected RGONR networks, the composite paper electrode exhibits excellent electrochemical performance. A high volumetric capacity of 508-244 mAh cm-3 was obtained at current densities in the range of 0.1-10 A g-1. Discharge capacities of 334 and 255 mAh cm-3 were still kept, even after 1500 cycles tested at current densities of 1 and 5 A g-1, respectively. This strategy provides insight into a new pathway for the creation of free-standing composite electrodes used in the energy storage and conversion.

Self-assembled sulfur/reduced graphene oxide nanoribbon paper as a free-standing electrode for high performance lithium–sulfur batteries

Flexible, interconnected sulfur/reduced graphene oxide nanoribbon paper (S/RGONRP) is synthesized through S2- reduction and evaporation induced self-assembly processes. The in situ formed sulfur atoms chemically bonded with the surface of reduced graphene oxide nanoribbons and were physically trapped by the compact assembly, which make the hybrid a suitable cathode material for lithium-sulfur batteries.

Rational design of metal oxide hollow nanostructures decorated carbon nanosheets for superior lithium storage

Unique nanostructures and intimate interfaces in nanocomposites play great roles in enhancing performance for energy storage and conversion application. Though many studies have focused on graphene/metal oxide composites with weak interactions by physical loading or chemical anchoring, engineering of metal oxide hollow nanostructures (h-MO) and construction of strongly coupled interfaces between graphene and metal oxides still remain in their infancy. In this work, metal oxide hollow nanostructures were bound onto graphene nanosheets by graphitic carbon layers (the final hybrid is denoted as h-MO@C@G), which were confirmed by HRTEM observations. Polyvinylpyrrolidone (PVP) and its derived carbon play great roles in uniform loading and engineering of h-MO as well as intimate integration of MO with graphene nanosheets. Benefiting from the synergistic effects of MO hollow nanostructures and strongly coupled interfaces for structural robustness and enhanced lithiation kinetics, the resulting h-Fe2O3@C@G anodes exhibit long cycling life over 500 times and a high rate capacity of 430 mA h g−1 at 15 A g−1. More importantly, the strategy developed here can be easily extended to synthesize other single metal oxide (Co3O4, NiOx) or mixed metal oxide (FeNiOx) hollow nanostructures strongly coupled with graphene nanosheets, and they all exhibit excellent electrochemical performance.

Nanopore-confined g-C3N4 nanodots in N, S co-doped hollow porous carbon with boosted capacity for lithium–sulfur batteries

Benefiting from the high theoretical specific capacity and low cost consumption, lithium–sulfur batteries have been regarded as the promising next-generation energy storage technology. However, lithium–sulfur batteries still encounter a series of challenges such as low conductivity and serious volumetric expansion of sulfur during the discharge process as well as the stubborn “shuttle effect” of polysulfides. Such problems have greatly plagued the real applications of lithium–sulfur batteries. Herein, we have synthesized below-5-nm g-C3N4 nanodots based on a pore confinement effect, and they are embedded in a MOF-derived N, S co-doped hollow porous carbon shell (CN@NSHPC) via a unique double solvent-induced strategy. CN@NSHPC displays superior lithium polysulfide (LiPS) adsorptivity and a high sulfur loading of 73%. When applied as an electrode in lithium–sulfur batteries, the CN@NSHPC electrode delivers an excellent specific capacity of 1447 mA h g−1 at 0.2C, good rate capability of 387 mA h g−1 at 5C, and excellent cycling stability, specifically, only 0.048% decay per cycle at 1.0C over 500 cycles. This proposed strategy provides an insight into a new pathway to construct co-doped carbon hollow nanostructure and nanodot materials by the pore confinement effect.