Kejian Ding

A novel Ni3N/graphene nanocomposite as supercapacitor electrode material with high capacitance and energy density

A novel Ni3N/graphene nanocomposite of small Ni3N nanoparticles anchoring on the reduced graphene oxide nanosheets has been successfully synthesized. Due to the quite small size of Ni3N nanocrystals, the surface for faradic redox reaction of pseudocapacitive materials dramatically increases. The main issue of the volume change obstructing the pseudo-supercapacitor performance is concurrently resolved by the tight attachment of Ni3N nanoparticles with flexible texture. Importantly, the two-step oxidation/reduction reaction between Ni(I) and Ni(III) endows this nanocomposite with large capacitance by providing more faradic charge. The kind of electrode material behaves excellently both in three-electrode and asymmetric supercapacitors. The biggest specific capacitance reaches to 2087.5 F g(-1) (at 1 A g(-1)), and its asymmetric supercapacitor cell with ethylene glycol modified RGO as negative electrode has a high energy density (50.5 W h kg(-1) at 800 W kg(-1)). The cell capacitance retention exceeds 80% after 5000 cycles at different high current densities, showing its promising prospects for high-energy supercapacitors.

Highly sensitive nonenzymatic glucose sensor based on nickel nanoparticle–attapulgite-reduced graphene oxide-modified glassy carbon electrode

In this article, a fast and sensitive nonenzymatic glucose sensor is reported utilizing a glassy carbon electrode modified by synthesizing nanocomposites of nickel nanoparticle-attapulgite-reduced graphene oxide (Ni NPs/ATP/RGO). A facile one-step electrochemical co-deposition approach is adopted to synthesize Ni NPs-ATP-RGO nanocomposites via electrochemical reduction of mixed precursor solution containing graphene oxide (GO), attapulgite (ATP) and nickel cations (Ni(2+)) at the cathode potentials. This strategy results in simultaneous depositions of ATP, cathodic reduction of Ni(2+) into nickel nanoparticles under acidic conditions, and in situ reduction of GO. The as-prepared NiNPs/ATP/RGO-based glucose sensor exhibits outstanding performance for enzymeless glucose sensing with sensitivity (1414.4 μAmM(-1)cm(-2)), linear range (1-710μM) and detection limit (0.37μM). What is more, the sensor has excellent stability and selectivity against common interferences in real sample.

A unique technology to transform inorganic nanorods into nano-networks

An inorganic nano-network of attapulgite is formed from rigid nanorods using ion beam bombardment. The structure of the nano-networks depends on the ion beam fluence for the same ion energy. Scanning electron microscopy reveals that ion beam bombardment improves the dispersion of the attapulgite particles and the change in the shape of the rod-shaped attapulgite particles stems from the thermal stress induced by ion beam bombardment. This phenomenon is more obvious for higher ion fluences. The bent or twisted rod-shaped attapulgite particles cross-link to form a network structure, which is stable in water, and when the ion fluence is increased further, the cross-linked points are permanently sealed. The improved materials are more useful than clava attapulgite particles.

Graphene quantum dots cut from graphene flakes: high electrocatalytic activity for oxygen reduction and low cytotoxicity

3–8 nm sized high quality graphene quantum dots with zigzag edges and multi-heteroatom doping were synthesized through a green process of electrochemically cutting pristine few-layer graphene flakes. The graphene quantum dots exhibit the structural features of monodisperse and shaped nanocrystals co-doped by O, N and F elements or chemical groups mainly at the zigzag edges. The cutting and in situ doping of the graphene flakes into dots were realized in the potential/current exchangeable electrochemical etching process without any thermal treatment. It was found that the graphene dots showed high electrocatalytic activity for the oxygen reduction reaction including 70 times enhancement in voltammetric current in oxygen saturated KOH compared to that in nitrogen. In addition, low in vitro cytotoxicity and fluorescent labeling to Vero cells and NRK cells of the graphene dots were presented. The Gdots synthesized may potentially be applied in the fields of electrocatalysis and biomedicine.

Aromatic ring substituted g-C3N4 for enhanced photocatalytic hydrogen evolution

A facile strategy to fabricate modified g-C3N4 with all-carbon aromatic rings incorporated in the constitutive plane was presented. The light absorption, band structure and photo-induced carrier separation of this benzene doped g-C3N4 was extremely improved. It exhibited a 3 times higher hydrogen evolution rate (HER) and a 17 times higher HER per surface area.

Surface Engineering for Extremely Enhanced Charge Separation and Photocatalytic Hydrogen Evolution on g‐C3N4

Reinforcing the carrier separation is the key issue to maximize the photocatalytic hydrogen evolution (PHE) efficiency of graphitic carbon nitride (g-C3 N4 ). By a surface engineering of gradual doping of graphited carbon rings within g-C3 N4 , suitable energy band structures and built-in electric fields are established. Photoinduced electrons and holes are impelled into diverse directions, leading to a 21-fold improvement in the PHE rate.

Near-Surface Oxidized Sulfur Modifications and Self-Assembly of Thiol-Modified Aptamer on Au Thin Film Substrates Influenced by Piranha Treatment

Self-assembly of thiol-modified oligonucleotides on Au films has great importance for biosensor applications. Prior to the self-assembly, a piranha treatment (PT) is commonly used to clean the Au surface. Here we report that near-surface oxidized sulfur modifications on Au thin films by PT for longer than 60 s have serious effects on the self-assembled monolayer (SAM) formation of thiol-modified single-stranded thrombin binding aptamer (s-TBA), and a PT time of 10-30 s is optimal for s-TBA SAM formation. These results have important implication to SAM formation of biomolecules, especially for the thiol-modified ones where a careful consideration of this key step could significantly enhance the SAM formation and biosensor performance.

Trivalent cerium-preponderant CeO2/graphene sandwich-structured nanocomposite with greatly enhanced catalytic activity for the oxygen reduction reaction

A sandwich-like CeO2/graphene nanocomposite (CeGS) with a uniform thin CeO2 crystalline film coating on reduced graphene oxide is presented. Large amounts of trivalent Ce and abundant oxygen vacancies (VO) were introduced onto the surface of CeGS. Due to the advantageous surficial crystal configuration, this CeGS displayed greatly enhanced catalytic activity and excellent durability for the oxygen reduction reaction (ORR). By DFT calculations, it was demonstrated that the Ce(III)-preponderant and VO-containing surface benefited the intense chemical adsorption and activation of O2 and optimized the intermediate reaction pathways.

Highly sensitive and selective detection of cadmium with a graphite carbon nitride nanosheets/Nafion electrode

A highly sensitive and selective electrochemical sensor is developed for the detection of cadmium with a nanosheet graphitic carbon nitride (g-C3N4) modified electrode. The g-C3N4 nanosheet modified glassy carbon electrode detects heavy metal not only by electrostatic interactions, but also by intercalating the holes during differential pulse anodic stripping voltammetry (DPASV) measurements for Cd2+ in aqueous solution. The calibration curves for Cd2+ covered two ranges varying from 1 nM to 1 μM and 1 μM to 100 μM. The limitation of detection (LOD) is estimated to be 0.5 nM for Cd2+, which is 53 times lower than the guideline values of drinking water given by the World Health Organization (WHO). In addition, the good repeatability and stability of the modified electrode is feasible for heavy metal detection in this study.