Zongyuan Xiao

Gating of Quantum Interference in Molecular Junctions by Heteroatom Substitution

Abstract To guide the choice of future synthetic targets for single‐molecule electronics, qualitative design rules are needed, which describe the effect of modifying chemical structure. Here the effect of heteroatom substitution on destructive quantum interference (QI) in single‐molecule junctions is, for the first time experimentally addressed by investigating the conductance change when a “parent” meta‐phenylene ethylene‐type oligomer (m‐OPE) is modified to yield a “daughter” by inserting one nitrogen atom into the m‐OPE core. We find that if the substituted nitrogen is in a meta position relative to both acetylene linkers, the daughter conductance remains as low as the parent. However, if the substituted nitrogen is in an ortho position relative to one acetylene linker and a para position relative to the other, destructive QI is alleviated and the daughter conductance is high. This behavior contrasts with that of a para‐connected parent, whose conductance is unaffected by heteroatom substitution. These experimental findings are rationalized by transport calculations and also agree with recent “magic ratio rules”, which capture the role of connectivity in determining the electrical conductance of such parents and daughters.

Three-Dimensional Printing of Polyaniline/Reduced Graphene Oxide Composite for High-Performance Planar Supercapacitor

We apply direct ink writing for the three-dimensional (3D) printing of polyaniline/reduced graphene oxide (PANI/RGO) composites with PANI/graphene oxide (PANI/GO) gel as printable inks. The PANI/GO gel inks for 3D printing are prepared via self-assembly of PANI and GO in a blend solvent of N-methyl-2-pyrrolidinone and water, and offer both shaping capability, self-sustainability, and electrical conductivity after reduction of GO. PANI/RGO interdigital electrodes are fabricated with 3D printing, and based on these electrodes, a planar solid-state supercapacitor is constructed, which exhibits high performance with an areal specific capacitance of 1329 mF cm-2. The approach developed in this work provides a simple, economic, and effective way to fabricate PANI-based 3D architectures, which leads to promising application in future energy and electric devices at micro-nano scale.

Synthesis and properties of graphene oxide–boron-modified phenolic resin composites

Boron–modified phenolic resin (BPR) has a good thermal property, but it has deficiencies in mechanical performance. To obtain PR materials with good thermal property, graphene oxide (GO) was added along with BPR to form a GO–boron-modified PR (GO-BPR). In this study, BPR and GO-BPR were prepared and their thermal resistance and mechanical properties were investigated. In addition, the effects of GO content on the thermal resistance of GO-BPR were studied. Results demonstrate that the optimal GO content was 0.5%. The thermal properties of GO-BPR with 0.5% GO improved 1.06 times when compared with that of BPR, and the peak degradation temperature of GO-BPR increased by approximately 10°C. When compared with BPR composite, the bending, tensile, and impact strengths of the GO-BPR composite materials with 0.5% GO-BPR increased by 46, 38, and 53%, respectively.

One-Pot Synthesis of Hierarchical Flower-Like Pd-Cu Alloy Support on Graphene Towards Ethanol Oxidation

The synergetic effect of alloy and morphology of nanocatalysts play critical roles towards ethanol electrooxidation. In this work, we developed a novel electrocatalyst fabricated by one-pot synthesis of hierarchical flower-like palladium (Pd)-copper (Cu) alloy nanocatalysts supported on reduced graphene oxide (Pd-Cu(F)/RGO) for direct ethanol fuel cells. The structures of the catalysts were characterized by using scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectrometer (XPS). The as-synthesized Pd-Cu(F)/RGO nanocatalyst was found to exhibit higher electrocatalytic performances towards ethanol electrooxidation reaction in alkaline medium in contrast with RGO-supported Pd nanocatalyst and commercial Pd black catalyst in alkaline electrolyte, which could be attributed to the formation of alloy and the morphology of nanoparticles. The high performance of nanocatalyst reveals the great potential of the structure design of the supporting materials for the future fabrication of nanocatalysts.

A rapid and scalable integrated membrane separation process for purification of polysaccharides from Enteromorpha prolifera

Abstract An integrated membrane separation process combining the tubular ceramic microfiltration (MF) membrane and the flat-sheet ultrafiltration (UF) membrane was developed to purify polysaccharides from Enteromorpha prolifera. The effects of membrane pore size, molecular weight cut-off (MWCO), transmembrane pressure (TMP) and adding-water multiples on membrane performance were in-depth studied. The results indicated that the optimal membrane pore size and TMP of the tubular ceramic MF process were found to be 1.2 μm and 0.225 MPa, and the optimal MWCO and TMP of the flat-sheet UF process were found to be 100 kDa and 0.3 MPa. The yields of polysaccharides were increased and optimized while the adding-water multiples was 1 during the diafiltration procedure. Furthermore, the water fluxes could be completely recovered using the specialized membrane cleaning methods, which ensured the reuse of membrane elements and satisfied the demands of industrial production. After purification by this integrated membrane separation process, the content of polysaccharides reached to 96.3%. The purified polysaccharides exhibited the superior moisture absorption and moisture retention properties compared to glycerol, polyethylene glycol (PEG) and luffa water. Graphical Abstract

Supramolecular Systems and Chemical Reactions in Single-Molecule Break Junctions

The major challenges of molecular electronics are the understanding and manipulation of the electron transport through the single-molecule junction. With the single-molecule break junction techniques, including scanning tunneling microscope break junction technique and mechanically controllable break junction technique, the charge transport through various single-molecule and supramolecular junctions has been studied during the dynamic fabrication and continuous characterization of molecular junctions. This review starts from the charge transport characterization of supramolecular junctions through a variety of noncovalent interactions, such as hydrogen bond, π–π interaction, and electrostatic force. We further review the recent progress in constructing highly conductive molecular junctions via chemical reactions, the response of molecular junctions to external stimuli, as well as the application of break junction techniques in controlling and monitoring chemical reactions in situ. We suggest that beyond the measurement of single molecular conductance, the single-molecule break junction techniques provide a promising access to study molecular assembly and chemical reactions at the single-molecule scale.