Imaging nanoscale molecular binding in functionalized graphene via tip-enhanced Raman spectroscopy.

Surface functionalization of low-dimensional nanomaterials offers a means to tailor their optoelectronic and chemical characteristics. However, functionalization reactions are sensitive to the inherent surface features of nanomaterials, such as defects, grain boundaries, and edges. Conventional optical characterization methods, such as Raman spectroscopy, have limited sensitivity and spatial resolution and, therefore, struggle to visualize reaction sites and chemical species.

Nanoscale insights into graphene oxide reduction by tip-enhanced Raman spectroscopy.

Graphene oxide (GO) has attracted substantial interest for its tunable properties and as a possible intermediate for the bulk manufacture of graphene. GO and its reduced derivatives display electronic and optical properties that depend strongly on their chemical structure, and with proper functionalization, GO can have a desirable bandgap for semiconductor applications. However, its chemical activity leads to a series of unclear chemical changes under ambient conditions, resulting in changes in color and solubility upon exposure to light.

Atmospheric-pressure CVD growth of two-dimensional 2H- and 1 T'-MoTefilms with high-performance SERS activity.

Two-dimensional (2D) molybdenum ditelluride (MoTe) is a member of the transition-metal dichalcogenides family, which is an especially promising platform for surface-enhanced Raman scattering (SERS) applications, due to its excellent electronic properties. However, the synthesis of large-area highly crystalline 2D MoTewith controllable polymorphism is a huge challenge due to the small free energy difference (∼40 meV per unit cell) between semiconducting 2H-MoTeand semi-metallic 1 T'-MoTe. Herein, we report an optimized route for the synthesis of 2H- and 1 T'-MoTefilms by atmospheric-pressure chemical vapor deposition.

One-Step Chemical Vapor Deposition Synthesis of 3D N-doped Carbon Nanotube/N-doped Graphene Hybrid Material on Nickel Foam.

3D hybrid nanostructures connecting 1D carbon nanotubes (CNTs) with 2D graphene have attracted more and more attentions due to their excellent chemical, physical and electrical properties. In this study, we firstly report a novel and facile one-step process using template-directed chemical vapor deposition (CVD) to fabricate highly nitrogen doped three-dimensional (3D) N-doped carbon nanotubes/N-doped graphene architecture (N-CNTs/N-graphene). We used nickel foam as substrate, melamine as a single source for both carbon and nitrogen, respectively.

Large Area Synthesis of Vertical Aligned Metal Oxide Nanosheets by Thermal Oxidation of Stainless Steel Mesh and Foil.

We report here the synthesis of metal oxide nanosheets (MONs) directly grown on stainless steel substrates by thermal oxidation in the presence of trace amounts of water. The morphology and microstructure of MONs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and atomic force microscopy (AFM). The composition of MONs was determined by the energy dispersive system and X-ray diffraction patterns.

Melamine as a single source for fabrication of mesoscopic 3D composites of N-doped carbon nanotubes on graphene.

Integration of two-dimensional graphene and one-dimensional carbon nanotubes (CNTs) to create potentially useful 3D mesoscopic carbon structures with enhanced properties relative to the original materials is very desirable. Here, we report a novel and simple route using chemical vapor deposition (CVD) methods to fabricate bead-like nitrogen-doped CNT/graphene composites (NCNT/G) a simple pyrolysis of the N-rich melamine in the presence of graphene oxide (GO) as a substrate using a Mn-Ni-Co ternary catalyst. We have characterized these structures by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra, isothermal analyses, and X-ray photoelectron spectroscopy.

Influence of electron storing, transferring and shuttling assets of reduced graphene oxide at the interfacial copper doped TiO2 p-n heterojunction for increased hydrogen production.

Herein we report simple, low-cost and scalable preparation of reduced graphene oxide (rGO) supported surfactant-free Cu2O-TiO2 nanocomposite photocatalysts by an ultrasound assisted wet impregnation method. Unlike the conventional preparation techniques, simultaneous reduction of Cu(2+) (in the precursor) to Cu(+) (Cu2O), and graphene oxide (GO) to rGO is achieved by an ultrasonic method without the addition of any external reducing agent; this is ascertained by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. UV-visible diffused reflectance spectroscopy (DRS) studies (Tauc plots) provide evidence for the loading of Cu2O tailoring the optical band gap of the photocatalyst from 3.

Direct observation of spatially heterogeneous single-layer graphene oxide reduction kinetics.

Graphene oxide (GO) is an important precursor in the production of chemically derived graphene. During reduction, GO's electrical conductivity and band gap change gradually. Doping and chemical functionalization are also possible, illustrating GO's immense potential in creating functional devices through control of its local hybridization.

Soluble reduced graphene oxide sheets grafted with polypyridylruthenium-derivatized polystyrene brushes as light harvesting antenna for photovoltaic applications.

Soluble graphene nanosheets, prepared by grafting polystyrene-based polymer chains from the surface of reduced graphene oxide (RGO), have been functionalized with pendant Ru(II) polypyridine chromophores. N-Hydroxysuccinimide (NHS) derivatized p-vinylbenzoic acid polymer chains were grown from methyl bromoisobutyrate initiation sites on the surface of RGO by atom transfer radical polymerization (ATRP). Deprotection of the resulting NHS polystyrene chains followed by amide coupling with the amine-derivatized Ru(II) polypyridyl complex [Ru(4-CH2NH2-4'-CH3-bpy)(bpy)2](2+) (4-CH2NH2-4'-CH3-bpy = 4-aminomethyl-4'-methyl 2,2'-bipyridine and bpy = 2,2'-bipyridine) afforded the covalently linked RGO-metallopolymer.

Proton activity in nafion films: probing exchangeable protons with methylene blue.

A simple approach to monitor the H(+) activity of a proton-exchange membrane (Nafion) is introduced by incorporating methylene blue as an indicator dye. The dye exhibits characteristics absorption maxima at 665 and 745 nm corresponding to its singly and doubly protonated forms, respectively. The apparent proton activity of Nafion as monitored from the appearance of doubly protonated methylene blue absorption is equivalent to 1.

Highly dispersed Pt catalysts on single-walled carbon nanotubes and their role in methanol oxidation.

Well-dispersed Pt catalysts with very high utilization efficiencies for fuel cell reactions have been prepared by ethylene glycol reduction on polymer-wrapped single-walled carbon nanotubes (SWCNTs). By wrapping the SWCNTs in a polymer such as polystyrene sulfonate, we are able to break up the nanotube bundles to achieve better dispersion. These polymer-wrapped SWCNTs with platinum nanoparticles deposited on them show very high electrochemically active surface areas.

Boosting fuel cell performance with a semiconductor photocatalyst: TiO2/Pt-Ru hybrid catalyst for methanol oxidation.

A hybrid carbon fiber electrode (CFE) consisting of TiO2 semiconductor photocatalyst and Pt-Ru catalyst has been developed to boost the performance of direct methanol fuel cells (DMFC). These two catalyst nanoparticles are deposited on opposite sides of the carbon fiber paper such that methanol oxidation is carried out catalytically on Pt-Ru and photocatalytically on TiO2 under UV-light irradiation. Since both catalysts carry out methanol oxidation independently, we observe an additive effect in the current generation.

Sonochemically prepared platinum-ruthenium bimetallic nanoparticles.

Colloidal bimetallic nanoparticles of Pt-Ru have been synthesized by sonochemical reduction of Pt(II) and Ru(III) in aqueous solutions. Transmission electron microscope (TEM) images indicate that sequential reduction of the Pt(II) followed by the Ru(III) produces particles with a core shell (Pt@Ru) morphology. In the presence of sodium dodecyl sulfate, SDS, as a stabilizer, the particles have diameters between 5 and 10 nm.

Single wall carbon nanotube supports for portable direct methanol fuel cells.

Single-wall and multiwall carbon nanotubes are employed as carbon supports in direct methanol fuel cells (DMFC). The morphology and electrochemical activity of single-wall and multiwall carbon nanotubes obtained from different sources have been examined to probe the influence of carbon support on the overall performance of DMFC. The improved activity of the Pt-Ru catalyst dispersed on carbon nanotubes toward methanol oxidation is reflected as a shift in the onset potential and a lower charge transfer resistance at the electrode/electrolyte interface.

Single-wall carbon nanotube-based proton exchange membrane assembly for hydrogen fuel cells.

A membrane electrode assembly (MEA) for hydrogen fuel cells has been fabricated using single-walled carbon nanotubes (SWCNTs) support and platinum catalyst. Films of SWCNTs and commercial platinum (Pt) black were sequentially cast on a carbon fiber electrode (CFE) using a simple electrophoretic deposition procedure. Scanning electron microscopy and Raman spectroscopy showed that the nanotubes and the platinum retained their nanostructure morphology on the carbon fiber surface.

Self-assembled linear bundles of single wall carbon nanotubes and their alignment and deposition as a film in a dc field.

A one-step process of solubilization of single wall carbon nanotubes (SWCNT) in an organic solvent has enabled us to polarize them asymmetrically in a dc electric field. Quaternary ammonium ion-capped SWCNTs readily suspend in organic solvents; under the influence of a dc electric field, they assemble as stretched bundles anchored on the positive electrode. At low dc applied field (approximately 40 V), all of the SWCNTs from the suspension are deposited on the electrode, thus providing a simple methodology to design robust SWCNT films.

Selective electrochemical detection of ionic and neutral species using films of Suwannee River humic acid.

An electroanalytical method has been developed to investigate the uptake of redox-active species by the humic acid substances. The Suwannee River humic acid (SHA) films were first cast on a glassy carbon electrode using an electrophoretic approach. The binding of a series of redox-active species to these SHA films was then probed using cyclic voltammetry at a rotating disk electrode.

Electrophoretic assembly of naturally occurring humic substances as thin films.

Polydisperse humic acid thin films on optically transparent electrodes (OTEs) have been prepared by electrophoretic deposition from a solution of Suwanee River humic acid (SHA) in ethanol/acetonitrile. The thickness of the film and the rate of deposition of SHA are dependent on the applied voltage and the concentration of the solution. Tapping-mode atomic force microscopy (TM-AFM) confirms the assembly of SHA aggregates on the electrode surface.