Kun Qi

Surface plasmon resonance technique for directly probing the interaction of DNA and graphene oxide and ultra-sensitive biosensing.

The binding of DNA with graphene oxide (GO) is important for applications in disease diagnosis, genetic screening, and drug discovery. The standard assay methods are mainly limited to indirect observation via fluorescence labeling. Here we report the use of surface plasmon resonance for direct sensing of DNA/GO binding. We show that this can be used for ultra-sensitive detection of single-stranded DNA (ssDNA). Furthermore, the results provide a more direct probe of DNA/GO binding abilities and confirm that hydrogen bonding plays a key role in the interaction between GO and ssDNA. This enables to a novel biosensor for highly sensitive and selective detection of ssDNA based on indirect competitive inhibition assay (ICIA). We report development of such a sensor with a linear dynamic range of 10(-14)-10(-6)M, a detection limit of 10fM and a high level of stability during repeated regeneration.

Decoration of the inert basal plane of defect-rich MoS2 with Pd atoms for achieving Pt-similar HER activity

Outstanding hydrogen evolution reaction (HER) activity and stability are highly desired for transition metal dichalcogenide (TMD)-based catalysts as Pt substitutes. Here, we theoretically calculated and experimentally showed that adsorbing Pd atoms on the basal plane of defect-rich (DR) MoS2 will effectively modulate the surface electronic state of MoS2 while retaining its active sites, which greatly enhanced the HER activity. Three decoration strategies were used to implement this design: direct epitaxial growth, assembling spherical nanoparticles and assembling Pd nanodisks (NDs). The results showed that only Pd NDs are able to be site-specifically decorated on the basal plane of DR-MoS2 through lamellar-counterpart-induced van der Waals pre-combination and covalent bonding. This Pd ND/DR-MoS2 heterostructure exhibits exceptional Pt-similar HER properties with a low onset-overpotential (40 mV), small Tafel slope (41 mV dec−1), extremely high exchange current density (426.58 μA cm−2) and robust HER durability. These results demonstrate a novel modification strategy by a lamellar metallic nanostructure for designing excellent layered TMD-based HER catalysts.

One-Step Synthesis of a Self-Supported Copper Phosphide Nanobush for Overall Water Splitting

Developing cheap, stable, and efficient electrocatalysts is of extreme importance in the effort to replace noble metal electrocatalysts for use in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). We report a three-dimensional self-supported Cu3P nanobush (NB) catalyst directly grown on a copper mesh via a one-step method. This nanostructure exhibits a superior catalytic activity of achieving a current density of 10 mA cm–2 at 120 mV and exhibits a long-term stability in acid solutions. It shows a Tafel slope of 72 mV dec–1 and an onset potential of −44 mV. This catalyst displays a good catalytic activity in basic electrolytes, reaching a current density of 10 mA cm–2 at the overpotential values of 252 and 380 mV for HER and OER, respectively. The bifunctional Cu3P NB/Cu catalyst exhibits better catalytic performances than the Pt/C and IrO2 catalysts in a two-electrode electrolyzer for overall water splitting.

Engineering Pt/Pd Interfacial Electronic Structures for Highly Efficient Hydrogen Evolution and Alcohol Oxidation

Tailoring the interfacial structure of Pt-based catalysts has emerged as an effective strategy to improve catalytic activity. However, little attention has been focused on investigating the relationship between the interfacial facets and their catalytic activity. Here, we design and implement Pd-Pt interfaces with controlled heterostructure features by epitaxially growing Pt nanoparticles on Pd nanosheets. On the basis of both density functional theory calculation and experimental results, we demonstrate that charge transfer from Pd to Pt is highly dependent on the interfacial facets of Pd substrates. Therefore, the Pd-Pt heterostructure with Pd(100)-Pt interface exhibits excellent activity and long-term stability for hydrogen evolution and methanol/ethanol oxidation reactions in alkaline medium, much better than that with Pd (111)-Pt interface or commercial Pt/C. Interfacial crystal facet-dependent electronic structural modulation sheds a light on the design and investigation of new heterostructures for high-activity catalysts.

Photo-reduced Cu/CuO nanoclusters on TiO 2 nanotube arrays as highly efficient and reusable catalyst

Non-noble metal nanoparticles are becoming more and more important in catalysis recently. Cu/CuO nanoclusters on highly ordered TiO2 nanotube arrays are successfully developed by a surfactant-free photoreduction method. This non-noble metal Cu/CuO-TiO2 catalyst exhibits excellent catalytic activity and stability for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with the presence of sodium borohydride (NaBH4). The rate constant of this low-cost Cu/CuO based catalyst is even higher than that of the noble metal nanoparticles decorated on the same TiO2 substrate. The conversion efficiency remains almost unchanged after 7 cycles of recycling. The recycle process of this Cu/CuO-TiO2 catalyst supported by Ti foil is very simple and convenient compared with that of the common powder catalysts. This catalyst also exhibited great catalytic activity to other organic dyes, such as methylene blue (MB), rhodamine B (RhB) and methyl orange (MO). This highly efficient, low-cost and easily reusable Cu/CuO-TiO2 catalyst is expected to be of great potential in catalysis in the future.

Morphology dependence of electrochemical properties on palladium nanocrystals

In recent years, shape control has received the most attention in the exploration of Pd nanocrystals (NCs). However, exploring an efficient approach for the systematic production of Pd NCs under similar reaction conditions still presents a significant challenge, which is significantly important to clearly explain the effectiveness of morphology on the catalytic activity of Pd NCs. We designed and accomplished a facile strategy for the morphology transformation between Pd nanosheets and Pd nanotetrahedra by simply controlling the reaction temperature. A growth mechanism was proposed based on TEM images of the time-dependent morphology evolution. The Pd nanosheets and Pd nanotetrahedra exhibit higher activity for the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) compared with the benchmark Pd/C catalysts, and their activities are dependent on the morphology. In particular, Pd nanosheets show an increased activity by 3.81 (MOR) and 2.86 (ORR) times due to their large specific surface area and exposed facets.

In situ preparation of porous Pd nanotubes on a GCE for non-enzymatic electrochemical glucose sensors

Porous Pd nanotubes were in situ fabricated on a glass-carbon electrode (GCE) via a one-step galvanic replacement reaction by using cheap, flexible, and ultralong copper nanowires as the sacrificial template. The electrode exhibits excellent electrocatalytic performance for non-enzymatic glucose biosensors, thanks to massive pores and high specific surface area. This non-enzymatic glucose biosensor shows a wide linear response range from 5 μM to 10 mM, with a sensitivity of 6.58 μA mM−1 cm−2, and a detection limit of 1 μM (signal-to-noise ratio of 3).

Nanoporous Sulfur-Doped Copper Oxide (Cu2OxS1–x) for Overall Water Splitting

Developing active and bifunctional noble metal-free electrocatalysts is crucial for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the full water splitting process. A ternary nanoporous sulfur-doped copper oxide (Cu2OxS1-x) was successfully synthesized on Cu foam. The obtained Cu2OxS1-x/Cu shows robust electrocatalytic activity toward HER with a low overpotential of 40 mV at 10 mA cm-2 and a Tafel slope of 68 mV dec-1 and exhibits long-term stability in acid solution. Moreover, Cu2OxS1-x shows excellent electrocatalytic activity for OER, HER, and overall water splitting as a bifunctional catalyst in 1.0 M KOH electrolyte. The sulfur doping strategy implemented here can greatly improve the catalytic performance and stability in both acidic and alkaline water electrolyzers and presents an efficient catalyst for overall water splitting.

Interfacial Engineered Surface Morphology Evolution of Au@Pd Core-Shell Nanorods

Engineering the interfacial structure of bimetallic nanocrystals is an effective method to improve their electrocatalytic performances. Here, we design a facile strategy for controlling the surface morphology evolution of Au@Pd core-shell nanorods by adjusting the solution supersaturation. The Pd shell of the as-prepared Au@Pd bimetallic nanorods can be modulated from a (111) facet-exposed island to a (100) facet-exposed conformal shell. The conformal shell structure exhibited enhanced catalytic performance toward the ethanol oxidation reaction, while the core-island structure possessed better catalytic stability. This work provides a facile method for interfacial engineering of bimetallic nanocrystals with desired morphology and properties.

Synthesis of ultrathin wrinkle-free PdCu alloy nanosheets for modulating d-band electrons for efficient methanol oxidation

The synthesis of ultrathin noble-metal-based alloy nanosheets with few-atomic-layer thickness remains a great challenge although they have attracted remarkable attention. Herein, ultrathin wrinkle-free Pd4Cu1 nanosheets with lateral size of 33.8 nm and thickness of 2.71 nm were successfully prepared using n-butylamine as a bifunctional agent. The ingenious structure possesses the highest electrochemically active surface area among the reported PdCu nanostructures. The quantum confinement and entrapment effects of the Pd4Cu1 nanosheets render the modulation of d-band electrons and weaken the adsorption of poisoning species, thus enhancing the performance towards methanol oxidation. The mass activity of the ultrathin wrinkle-free Pd4Cu1 nanosheets was 6.7-times and 4.8-times higher than that of commercial Pd black and Pt black, respectively. This study highlights the important role of designing ultrathin alloy nanosheets towards enhancing electrocatalytic performance.