Xiangjing Wang

Interdiffusion Reaction-Assisted Hybridization of Two-Dimensional Metal–Organic Frameworks and Ti3C2Tx Nanosheets for Electrocatalytic Oxygen Evolution

Two-dimensional (2D) metal-organic framework (MOF) nanosheets have been recently regarded as the model electrocatalysts due to their porous structure, fast mass and ion transfer through the thickness, and large portion of exposed active metal centers. Combining them with electrically conductive 2D nanosheets is anticipated to achieve further improved performance in electrocatalysis. In this work, we in situ hybridized 2D cobalt 1,4-benzenedicarboxylate (CoBDC) with Ti3C2Tx (the MXene phase) nanosheets via an interdiffusion reaction-assisted process. The resulting hybrid material was applied in the oxygen evolution reaction and achieved a current density of 10 mA cm-2 at a potential of 1.64 V vs reversible hydrogen electrode and a Tafel slope of 48.2 mV dec-1 in 0.1 M KOH. These results outperform those obtained by the standard IrO2-based catalyst and are comparable with or even better than those achieved by the previously reported state-of-the-art transition-metal-based catalysts. While the CoBDC layer provided the highly porous structure and large active surface area, the electrically conductive and hydrophilic Ti3C2Tx nanosheets enabled the rapid charge and ion transfer across the well-defined Ti3C2Tx-CoBDC interface and facilitated the access of aqueous electrolyte to the catalytically active CoBDC surfaces. The hybrid nanosheets were further fabricated into an air cathode for a rechargeable zinc-air battery, which was successfully used to power a light-emitting diode. We believe that the in situ hybridization of MXenes and 2D MOFs with interface control will provide more opportunities for their use in energy-based applications.

One-step and green synthesis of nitrogen-doped carbon quantum dots for multifunctional electronics

A facile one-step and green synthesis method was developed to prepare water soluble, environmentally friendly, and highly nitrogen-doped carbon quantum dots (CQDs) with tunable properties. As a proof-of-concept application, a multifunctional electronic device with the configuration of PEDOT:PSS/s-CQD@SWCNT/PEDOT:PSS was fabricated through a full-solution process, which exhibits memory and current limiting behavior, with the merit of stable operation and reliable endurance.

Wafer-Scale Ultrathin Two-Dimensional Conjugated Microporous Polymers: Preparation and Application in Heterostructure Devices

In this work, we report a universal surface-assisted oxidative polymerization strategy for wafer-scale fabrication of ultrathin two-dimensional conjugated microporous polymers (2D CMPs) on arbitrary substrates under ambient conditions. Three kinds of 2D CMPs with average thickness of 1.5-3.6 nm were prepared on SiO2/Si substrates by using carbazole based monomers. Moreover, 2D CMPs can be grown on reduced graphene oxide (rGO) substrate to construct large-area 2D CMP/rGO heterostructure. As a proof-of-concept demonstration, an organic vertical field-effect transistor based on 2D CMP/rGO heterostructures was fabricated, which exhibited typical p-type behavior with high reproducibility and on/off current ratio. Most importantly, the direct growth of large-area 2D CMPs on arbitrary substrates is compatible with the conventional processes in the semiconductor industry, and therefore is expected to expedite the development of 2D CMPs as building blocks for construction of practical electronic devices.

A general strategy for high performance stretchable conductors based on carbon nanotubes and silver nanowires

A general strategy for high performance stretchable conductors based on one-dimensional conductive materials is proposed. Our approach involves a combination of prestrain for high stretchability and embedding for electrical stability and smooth surface. The resulting stretchable conductors exhibit superior electrical stability with stretchability to 50% tensile strain and a 1000 cycle endurance test, demonstrating their potential as high performance conductors in stretchable electronics.

Large-area patterned 2D conjugated microporous polymers via photomask-assisted solid-state photopolymerization

The large-area and scalable patterning process of conjugated polymers is a critical step toward their practical applications in organic electronics. Here we report a wafer-scale patterning method for 2D conjugated microporous polymer (CMP) films on arbitrary substrates via photomask-assisted solid-state photopolymerization under ambient conditions. 2D CMP patterns from monomeric carbazole materials were controllably prepared with variable geometries with the geometric photomasks and desired film thicknesses by modulating the polymerization time. Moreover, 2D CMP patterns with various size and shapes can be formed onto a reduced graphene oxide (rGO) substrate to construct 2D CMP/rGO heterostructures. The obtained heterostructure exhibited a p-type behavior compared to the metal-like property of the rGO film. Combining this solid-state photopolymerization with photomask techniques, a patterned 2D organic/inorganic heterostructure with a precise size and shape control could be further realized for other 2D materials and their integrated devices.

Polymer–carbon dot hybrid structure for a self-rectifying memory device by energy level offset and doping

A strategy for self-rectifying memory diodes based on a polymer–carbon dot hybrid structure, with a configuration of rGO/PEDOT : PSS/carbon dots/MEH-PPV/Al, has been proposed. The fabricated device exhibits a rectification of 103 in the rectification model and an ON/OFF current ratio of 121 in the memory model. The rectifying behavior was attributed to an energy level offset between the electrodes and the bilayer polymers and the memory effect was induced by carrier trapping of carbon dots within the polymers.

Direct Photopolymerization and Lithography of Multilayer Conjugated Polymer Nanofilms for High Performance Memristors

Controllable preparation of conjugated polymer nanofilms with desirable pattern, thickness, and multilayer structures plays a critical role in high performance organic electronics. Herein, we report a novel strategy combining direct photopolymerization and in situ growth technique for controllable preparation of multilayer conjugated microporous polymer (CMP) nanofilms. By modulating the irradiation time and photomask shape of photopolymerization, scalable patterned CMP nanofilms with variable thickness and geometries were prepared. By further utilizing the in situ layer-by-layer growing method, multilayer CMP nanofilms comprising identical precursor and different precursors were constructed rationally. Moreover, the polymer vertical diodes based on the multilayer CMP nanofilms exhibited layer number-dependent electrical properties from linear resistor to memristor. The trilayer CMP nanofilms-based memristor showed nonvolatile memory effect with a higher ON/OFF current ratio of up to 1.0 × 103. Our study presents an effective strategy for the precise preparation of multilayer patterned homostructure and heterostructure conjugated polymer nanofilms for high performance integrated polymer electronics.