Tongshun Wu

Decorated graphene sheets for label-free DNA impedance biosensing

An efficient DNA impedance biosensing platform is constructed, in which positively charged N,N-bis-(1-aminopropyl-3-propylimidazol salt)-3,4,9,10-perylene tetracarboxylic acid diimide (PDI) is anchored to graphene sheets. The π-π stacking and electronic interactions are elucidated by the distinct absorption features in UV-vis spectra and by quenching perylene fluorescence in contact with graphene. The rational design and tailoring of graphene surface invest it with desired properties (dispersive, structural, photoelectrical and conductive, etc.) and boost its application. Electrostatic interaction between PDIs positively charged imidazole rings and negatively charged phosphate backbones of single-stranded DNA (ssDNA) facilitates ssDNA immobilization. This manner is different from these mainly based on the attraction between the rings in DNA bases and the hexagonal cells of graphene, which is disturbed after hybridization and causes the leaving of formed double-stranded DNA from graphene surface. The electrostatic ssDNA grafting occupies phosphate backbones and particularly leaves the bases available for efficient hybridization. DNA immobilization and hybridization lead to PDI/graphene interfacial property changes, which are monitored by electrochemical impedance spectroscopy and adopted as the analytical signal. The conserved sequence of the pol gene of human immunodeficiency virus 1 is satisfactorily detected via this PDI/graphene platform and shows high reproducibility, selectivity.

Growth Control of MoS2 Nanosheets on Carbon Cloth for Maximum Active Edges Exposed: An Excellent Hydrogen Evolution 3D Cathode

To greatly improve the hydrogen evolution reaction (HER) performance, it is the key approach to expose as many active edges of MoS2 as possible. This target is the research hotspot and difficulty of MoS2 which is a promising HER catalyst. In this work, we realized the active-edges control of MoS2 nanosheets on carbon cloth (CC) by growth control during the synthesis procedure. Moreover, MoS2 nanosheets vertically grown on carbon cloth (MoS2⊥CC) was confirmed to be the best morphology with maximum active edges exposed. Multifactors structure control resulted in abundant active-edges exposure and effective electron delivery, thus excellent HER activity. This three-dimensional cathode, MoS2⊥CC, can reach a great current density of 200 mA/cm(2) at a small overpotential of 205 mV. The preeminent HER performance can rival the best MoS2-based catalyst ever reported.

Spontaneous and Fast Growth of Large-Area Graphene Nanofilms Facilitated by Oil/Water Interfaces

An efficient wet-chemical method based on soft interfacial self-assembly is developed for spontaneous, fast growth of large-area graphene nanofilms on various substrates. The graphene nanofilms produced show tunable optical properties and a highly reversible optoelectronic response. Complementary to chemical vapor deposition, this method could offer a fast, simple, and low-cost chemical strategy to produce graphene nanofilms.

A carbon-based photocatalyst efficiently converts CO2 to CH4 and C2H2 under visible light

Novel photocatalysts consisting of porphyrin and graphene have been designed to reduce CO2 to hydrocarbons under visible light. These catalysts can (i) effectively reduce CO2 to hydrocarbons, particularly to C2H2; and (ii) selectively control the transfer of photogenerated electrons from graphene to CO2 rather than to H2O.

Ce-/S-codoped TiO2/Sulfonated graphene for photocatalytic degradation of organic dyes

TiO2 is an abundant and environmentally benign material, but has a wide band gap, which greatly confines its applications in photocatalysis. Doping and modifying the material composition are both generally used to change and control the photocatalytic activity of semiconductors. Herein, we describe a method and resulting activity of depositing Ce-/S-codoped TiO2 nanoparticles (NPs) on water-soluble sulfonated graphene (SGE) sheets, which guarantees a direct contact and satisfactory electron transfer between the semiconductor and graphene. The Ce/S–TiO2 NPs are homogeneously fixed on the surface of SGE sheets with an average particle size of ∼7 nm. The resulting composite showed noticeable activity in photodegrading methyl orange (κ = 0.425 h−1). This improved performance can be attributed to the synergistic effects of Ce- and S-codoping toward TiO2 and the composite action between TiO2 NPs and SGE. This type of novel composite is expected to stimulate the development of doped and graphene-involved photocatalysts for addressing environmental problems.

Perylene ligand wrapping G-quadruplex DNA for label-free fluorescence potassium recognition

A perylene ligand, N,N-bis-(1-aminopropyl-3-propylimidazol salt)-3,4,9,10-perylene tetracarboxylic acid diimide ligand (PDI), which consisted of π-conjugated perylene moiety and hydrophilic side chains with positively charged imidazole rings, was used to wrap G-quadruplex for fluorescence turn-on K(+) recognition. Electrostatic attraction between PDIs positively charged imidazole rings and DNAs negatively charged phosphate backbones enabled PDI to accumulate on DNA. Upon trapping K(+), these G-rich DNA sequences transitioned to G-quadruplex. Subsequently, PDI ligands wrapped G-quadruplex, in which the flat aromatic core of PDI ligand interacted with G-quartet through π-π stacking and the side chains were positioned in grooves through electrostatic interactions. Consequently, the interaction mode change and conformational transition from PDI stacked G-sequence to PDI wrapped G-quadruplex led to PDI fluorescence enhancement, which was readily monitored as the detection signal. This strategy excluded the sequence tagging step and exhibited high selectivity and sensitivity towards K(+) ion with the linear detection range of 10-150 nM. Besides, PDI ligands may hold diagnostic and therapeutic application potentials to human telomere and cancer cells.

Improved performances of a LiNi0.6Co0.15Mn0.25O2 cathode material with full concentration-gradient for lithium ion batteries

A novel high capacity cathode material with a full concentration-gradient (FCG) structure has been successfully synthesized by a modified hydroxide co-precipitation method. A continuous concentration change of Ni, Co, and Mn from the core LiNi0.8Co0.1Mn0.1O2 to the shell LiNi0.4Co0.2Mn0.4O2 in each particle with an average composition of LiNi0.6Co0.15Mn0.25O2 is confirmed by EDX and ICP, respectively. Charge–discharge tests demonstrate that the FCG cathode delivers a high specific capacity of 190 mA h g−1 at a current density of 0.05 mA cm−2, exceptional rate capacity (a high capacity of 125 mA h g−1 at an ultrafast rate of 10C-rate), and an ultralong cycle life up to 1000 cycles (capacity retention of 80% at 5C-rate), which is obviously superior to the conventional cathode LiNi0.6Co0.15Mn0.25O2. Meanwhile, the Mn-rich in the outer layer of the FCG cathode contributes to more excellent thermal stability than the conventional cathode LiNi0.6Co0.15Mn0.25O2.

Disposable graphene sensor with an internal reference electrode for stripping analysis of heavy metals

In this study, a low-cost disposable graphene sensor was fabricated for detecting heavy metals such as Cd2+, Pb2+ and Cu2+ by the anodic stripping voltammetry method (ASV). Vacuum compacted graphene films were used as the three electrodes, and they showed excellent conductivity and low noise signals. A big advantage was the simple fabrication process of graphene films without any binder. Furthermore, a ferrocene-based internal reference was introduced in the working electrode. The analytes were recognized by the relative distances of the stripping potential peaks between the working electrode and internal reference electrode. Finally, the all-graphene-based sensor was successfully built for the electrochemical analysis and then applied for determination of heavy metals in real river-water samples.

Collector and binder-free high quality graphene film as a high performance anode for lithium-ion batteries

Collector and binder-free high quality graphene film has been successfully synthesized by a simple filtration process. Electrochemical results indicate that the graphene film exhibits good rate and cycle behavior compared with the commercial mesocarbon microbeads (MCMB)/copper system. More importantly, after excluding the dead-weight copper collector, the gravimetric energy density could be enhanced to some extent. This may provide an alternative in the demand for higher energy density lithium-ion batteries.