Xiaochen Dong

3D Graphene–Cobalt Oxide Electrode for High-Performance Supercapacitor and Enzymeless Glucose Detection

Using a simple hydrothermal procedure, cobalt oxide (Co(3)O(4)) nanowires were in situ synthesized on three-dimensional (3D) graphene foam grown by chemical vapor deposition. The structure and morphology of the resulting 3D graphene/Co(3)O(4) composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The 3D graphene/Co(3)O(4) composite was used as the monolithic free-standing electrode for supercapacitor application and for enzymeless electrochemical detection of glucose. We demonstrate that it is capable of delivering high specific capacitance of ∼1100 F g(-1) at a current density of 10 A g(-1) with excellent cycling stability, and it can detect glucose with a ultrahigh sensitivity of 3.39 mA mM(-1) cm(-2) and a remarkable lower detection limit of <25 nM (S/N = 8.5).

Doping Single‐Layer Graphene with Aromatic Molecules

Recently discovered single-layer graphene (SLG) has attracted great attention not only because this perfect 2-dimensional carbon crystalline structure enables unprecedented explorations of fundamental physics but also because of its exciting potentials in the post-silicon nanoeletronics 1-6 . As the electrical properties of SLG films are very sensitive to the local perturbations such as from surface charges 7-9 and adsorbed gas molecules 6 , it is plausible that the electronic structures, hence the performance, of SLG may be tailored by molecular doping on its surface. Herein, we demonstrated that the electronic structures of SLG can be differentially modulated by doping from various aromatic molecules. We also show that a simple spectroscopic method based on the Raman 2D and G band frequency sampling can be used to distinguish the n- and p-doped SLG. Raman spectroscopy is a powerful tool to rapidly and nondestructively examine intrinsic physical properties of various carbon nanostructures, including flat and one-atom thick carbon crystalline layer (graphene monolayer), stacked graphenes (graphite), and roll-up graphene monolayer (single-walled carbon nanotube–SWNT). The characteristic G (~1580-1590 cm -1 ) and 2D (~2690-2710 cm -1 ) Raman bands are able to reveal the number of stacked graphene layer 10-12 and the changes in charge carrier concentration (or Fermi energy shift) induced by static electrical field 13-14 .

Electrical Detection of DNA Hybridization with Single‐Base Specificity Using Transistors Based on CVD‐Grown Graphene Sheets

[*] Dr. P. Chen School of Chemical and Biomedical Engineering, Nanyang Technological University Singapore, 637459 (Singapore) E-mail: pengchen@ntu.edu.sg Dr. L.-J. Li, Dr. X. Dong, Y. Shi School of Materials Science and Engineering, Nanyang Technological University Singapore, 639798 (Singapore) E-mail: ljli@ntu.edu.sg Dr. X. Dong, Dr. W. Huang Jiangsu Key Laboratory for Organic Electronics & Information Displays (KLOEID) Institute of Advanced Materials (IAM) Nanjing University of Posts and Telecommunications (NUPT) 9 Wenyuan Road, Nanjing 210046 (P. R. China)

Macroporous and Monolithic Anode Based on Polyaniline Hybridized Three-Dimensional Graphene for High-Performance Microbial Fuel Cells

Microbial fuel cell (MFC) is of great interest as a promising green energy source to harvest electricity from various organic matters. However, low bacterial loading capacity and low extracellular electron transfer efficiency between the bacteria and the anode often limit the practical applications of MFC. In this work, a macroporous and monolithic MFC anode based on polyaniline hybridized three-dimensional (3D) graphene is demonstrated. It outperforms the planar carbon electrode because of its abilities to three-dimensionally interface with bacterial biofilm, facilitate electron transfer, and provide multiplexed and highly conductive pathways. This study adds a new dimension to the MFC anode design as well as to the emerging graphene applications.

Superhydrophobic and superoleophilic hybrid foam of graphene and carbon nanotube for selective removal of oils or organic solvents from the surface of water

A monolithic 3D hybrid of graphene and carbon nanotube was synthesized by two-step chemical vapor deposition. Owing to its superhydrophobic and superoleophilic properties, it can selectively remove oils and organic solvents from water with high absorption capacity and good recyclability.

Nanoelectronic biosensors based on CVD grown graphene

Graphene, a single-atom-thick and two-dimensional carbon material, has attracted great attention recently. Because of its unique electrical, physical, and optical properties, graphene has great potential to be a novel alternative to carbon nanotubes in biosensing. We demonstrate the use of large-sized CVD grown graphene films configured as field-effect transistors for real-time biomolecular sensing. Glucose or glutamate molecules were detected by the conductance change of the graphene transistor as the molecules are oxidized by the specific redox enzyme (glucose oxidase or glutamic dehydrogenase) functionalized onto the graphene film. This study indicates that graphene is a promising candidate for the development of real-time nanoelectronic biosensors.

3D graphene foam as a monolithic and macroporous carbon electrode for electrochemical sensing.

Graphene, a single-atom-thick monolayer of sp(2) carbon atoms perfectly arranged in a honeycomb lattice, is an emerging sensing material because of its extraordinary properties, such as exceptionally high specific surface area, electrical conductivity, and electrochemical potential window. In this study, we demonstrate that three-dimensional (3D), macroporous, highly conductive, and monolithic graphene foam synthesized by chemical vapor deposition represents a novel architecture for electrochemical electrodes. Being employed as an electrochemical sensor for detection of dopamine, 3D graphene electrode exhibits remarkable sensitivity (619.6 μA mM(-1) cm(-2)) and lower detection limit (25 nM at a signal-to-noise ratio of 5.6), with linear response up to ∼25 μM. And the oxidation peak of dopamine can be easily distinguished from that of uric acid - a common interferent to dopamine detection. We envision that the graphene foam provides a promising platform for the development of electrochemical sensors as well as other applications, such as energy storage and conversion.

Graphene-based biosensors for detection of bacteria and their metabolic activities

Graphene, which is a recently discovered single-atom-thick planar sheet of carbon atoms perfectly arranged in a honeycomb lattice, has great potential in biosensing owing to its extraordinary electrical, physical, and optical properties. In this work, we demonstrate a graphene based biosensor to electrically detect E. coli bacteria with high sensitivity and specificity. The large-sized graphene film was grown by chemical vapor deposition and functionalized with anti-E. coliantibodies and passivation layer. Significant conductance increase of the graphene device was observed after exposure to E. coli bacteria at a concentration as low as 10 cfu/mL, while no significant response was triggered by high concentration of the another bacterial strain. In addition, this biosensor was employed to detect the glucose induced metabolic activities of the bound E. coli bacteria in real time. This simple, fast, sensitive, and label-free nanoelectronic biosensor, in principle, could serve as a high throughput platform for detection of any pathogenic bacteria, and for functional studies or screening of antibacterial drugs.

Binary metal oxide: advanced energy storage materials in supercapacitors

Binary transition metal oxides (BTMOs) possess higher reversible capacity, better structural stability and electronic conductivity, and have been widely studied to be novel electrode materials for supercapacitors. In this review, we present an extensive description of BTMO materials and the most commonly used synthetic methods. Furthermore, we review several notable BTMOs and their composites in application of supercapacitors. With the increasing attention for energy storage, more and more exciting results about BTMO materials will be reported in the future.

Electrodeposited Pt on three-dimensional interconnected graphene as a free-standing electrode for fuel cell application†

A three-dimensional interconnected graphene monolith was used as an electrode support for pulsed electrochemical deposition of platinum (Pt) nanoparticles. Pt nanoparticles with well-defined morphology and small size can be obtained by controlling electrodeposition potential and time. Electrochemical characterization was carried out to examine the electrocatalytic activity of this monolithic electrode towards methanol oxidation in acidic media. The results show that the carbon material surface and structure have a strong influence on the Pt particle size and morphology. Compared with the three-dimensional scaffold of carbon fibers, the three-dimensional graphene when used as a free-standing electrode support resulted in much improved catalytic activity for methanol oxidation in fuel cells due to its three-dimensionally interconnected seamless porous structure, high surface area and high conductivity.