Electronic transport in monolayer graphene with extreme physical deformation: ab initio density functional calculation

Voltammetric determination of acetaminophen in pharmaceutical preparations and human urine using glassy carbon paste electrode modified with reduced graphene oxide

A completely new direct voltammetric method has been developed for determination of acetaminophen (APAP), known as popular analgesic drug. The present electroanalytical method is based on anodic oxidation of APAP at the glassy carbon paste electrode modified with reduced graphene oxide (RGO). Key experimental conditions were studied, resulting in a set of optimal conditions: acetate buffer (pH 5.0) as working medium electrolyte, content of RGO, parameters of squarewave voltammetry including the potential step of 5 mV, potential amplitude of 50 mV, and frequency of 40 Hz. If peak area is used for evaluation, a linear range from 1.2 × 10^–6 to 2.2 × 10^–4 mol L⁻¹ characterized by determination coefficient of 0.9971, limits of quantification and detection, 9.3 × 10^–7 mol L⁻¹ and 3.1 × 10^–7 mol L⁻¹, respectively, will be obtained. Under validation, the precision was described by relative standard deviation of 2.9% for the model sample analysis. Finally, the developed voltammetric method was compared with a reference high-performance liquid chromatography method in the analysis of commercially available pharmaceutical preparation and human urine collected from five healthy volunteers.

Folds and buckles at the nanoscale: experimental and theoretical investigation of the bending properties of graphene membranes

The elastic properties of graphene crystals have been extensively investigated, revealing unique properties in the linear and nonlinear regimes, when the membranes are under either stretching or bending loading conditions. Nevertheless less knowledge has been developed so far on folded graphene membranes and ribbons. It has been recently suggested that fold-induced curvatures, without in-plane strain, can affect the local chemical reactivity, the mechanical properties, and the electron transfer in graphene membranes. This intriguing perspective envisages a materials-by-design approach through the engineering of folding and bending to develop enhanced nano-resonators or nano-electro-mechanical devices. Here we present a novel methodology to investigate the mechanical properties of folded and wrinkled graphene crystals, combining transmission electron microscopy mapping of 3D curvatures and theoretical modeling based on continuum elasticity theory and tight-binding atomistic simulations.

Folded graphene membranes: mapping curvature at the nanoscale

While the unique elastic properties of monolayer graphene have been extensively investigated, less knowledge has been developed so far on folded graphene. Nevertheless, it has been recently suggested that fold-induced curvature (without in-plane strain) could possibly affect the local chemical and electron transport properties of graphene, envisaging a material-by-design approach where tailored membranes are used in enhanced nanoresonators or nanoelectromechanical devices. In this work we propose a novel method combining apparent strain analysis from high-resolution transmission electron microscopy (HREM) images and theoretical modeling based on continuum elasticity theory and tight-binding atomistic simulations to map and measure the nanoscale curvature of graphene folds and wrinkles. If enough contrast and resolution in HREM images are obtained, this method can be successfully applied to provide a complete nanoscale geometrical and physical picture of 3D structure of various wrinkle and fold configurations.

Enhanced photoelectrocatalytic activity for dye degradation by graphene-titania composite film electrodes

Graphene-titania composite film electrodes have been fabricated by a dip-coating method. Transmission electron microscopy (TEM) images show that the titania nanoparticles were dispersed uniformly, with only a little aggregation on the surface and edges of the graphene sheets. XRD analysis showed that the composite electrodes comprised the anatase phase of titania with just a little rutile phase. The photoelectrocatalytic activities of the as-prepared samples were investigated by studies of the degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2). An enhancement of the photocurrents was observed using the graphene-titania composite electrodes, compared with pure titania film electrodes, under UV light irradiation. This improvement is attributed to the following two reasons: enhanced migration efficiency of the photo-induced electrons and enhanced adsorption activity of the dye molecules. In addition, we investigated the effects of graphene content and pH values on the photoelectrocatalytic activity of the as-prepared composite film electrodes. Results showed that there was an optimal amount of 5% (initial graphite oxide content).