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Herein, we demonstrate a microwave-assisted chemical reduction technique to exfoliate a few layers of graphene from the natural waste material, ‘coconut shell’. The microwave irradiation coconut shell is subjected to structural, morphological and functional groups characterization methods including SEM, Raman, FTIR and XPS spectroscopic analyses. The formation of biomass reduced graphene (BRG) has been confirmed through Raman and FTIR spectroscopic analyzes with the presence of D, G and 2D and other functional spectral bands, respectively. The surface topography of the BRG exhibits two-dimensional mat structures with wrinkle topography, imaged by electron microscopic techniques. The metallic behaviour of the BRG is evaluated by band structure calculation using density functional theory. The synthesized nanostructure has been evaluated for exhaled diabetic breath sensing application by fabricating sensor device on the paper-based substrate by roll-to-roll coating technique. The BRG sensor exhibited enhanced sensing response at a very lower concentration of diabetic biomarker with long term stability and rapid response/recovery time of 1.11 s/41.25 s, respectively. Based on our findings, the microwave-assisted BRG is a potential candidate for fabricating highly scalable, inherently safe, economically viable and excellent sensing performance to detect exhaled diabetic breath at room temperature. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) is a unique technique that allows us to detect samples in trace quantities. The spectral intensities of the characteristic Raman peaks of the analyte molecule are enhanced manifold in the presence of noble metal nanoparticles (NPs). The existence of NPs is necessary to couple the incident electromagnetic field with NPs through the localized surface plasmon resonance phenomenon, which primarily contributes to the enhancement of an SERS signal. The present work demonstrates the working of a paper-based SERS substrate to detect and quantify two pharmaceutical drugsâ€"paracetamol and aspirinâ€"in water. The proposed SERS substrate was obtained by drop-casting silver NPs over printing grade 100 grams per square meter (GSM) paper. 100 GSM denotes the class of paper where 100 grams of raw materials (cellulose) is used per square meter to manufacture the paper. The performance of the designed SERS substrate was initially evaluated with two Raman active samplesâ€"malachite green and rhodamine-6G. The applicability of the proposed SERS substrate was evaluated further through monitoring the Raman spectra of the two aforementioned pharmaceutical drugs in different field-collected water samples, thus establishing the reliability of the scheme in a real field environment. [ABSTRACT FROM AUTHOR]

The authors of the title paper (Mater. Res. Express 6 (2019) 116213) claim to have grown a nickel boro phthalate (NBP) crystal by the slow evaporation method. A critical analysis of the paper reveals that the so-called NBP is an improperly characterized material. A reinvestigation of the crystal growth reaction has been performed to unambiguously characterize the product. In this letter to the Editor, it is proved that nickel boro phthalate neither contains nickel nor phthalate but is, in fact, boric acid.

Mass transport and conductivity properties of the carbon fiber papers (CFPs) used in gas diffusion layers are among the critical parameters that affect a proton exchange membrane fuel cell (PEMFC) performance. Here, instead of carbonization/graphitization in the commercial CFPs manufacturing steps, the expanded graphite (EG) is numerically added to the CFP substrate to compensate and enhance the conductivity. The microstructures of different polymer binder/carbon fiber (CF) composites with and without EG are reconstructed using a digital 3D reconstruction technique. The binder phase is discriminated as an individual phase using image processing, and the effects of different binder percentages are demonstrated. In comparing the properties, the reconstructed CFP exhibited satisfactory properties against the values of the commercial CFPs in the literature and our conducted experimental tests. For the binder/CF/EG CFPs, 1.9 W/mK of effective thermal conductivity in the through-plane direction and also 30.2 mΩ.cm of the in-plane electrical resistivity are reached, compared to 0.48-1.8 W/mK (for Sigracet and Toray papers) and 12.9 mΩ.cm (for untreated Toray TGP-H-60), in the conventional CFPs. Overall, adding EG to the CFPs substrate provides valuable properties and can be considered as a proper replacement in future design and manufacturing of CFPs. [ABSTRACT FROM AUTHOR]

This paper presents the fabrication and characterization of a 'T'-shaped methanol-based fuel cell supported on paper. Methanol is used as the fuel and potassium permanganate is used as the oxidant. A polyacrylamide based gel, impregnated with H2SO4 limits the fuel and oxidant cross over and serves as the membrane/electrolyte to facilitate the ion transport between anode and cathode. Composite of nitrogen doped graphene oxide and NiCo2O4 micro-spheres, having flower-like structure, is used as the catalyst on both the electrodes to improve the cell performance. The use of catalyst has led to 5 times increase in the peak power density. The catalysts are characterized using XRD, SEM, EDX and TEM. A stack of two paper cells could illuminate an LED for 30 minutes. A simple mathematical model based on Butler-Volmer kinetics is used to predict the cell performance and predictions are compared with experimental measurements. [ABSTRACT FROM AUTHOR]

This work establishes that the frequency and temperature-dependent electronic and dielectric properties of electrochemically reduced graphene (ERGO) are higher than graphene oxide (GO) papers by 2 orders of magnitude. There is stronger polarization as a result of increased concentration of reduced clusters and thinning of graphene sheets in ERGO papers, first ever electrochemically reduced paper from GO. In GO, there is a greater dependence on frequency due to a higher percentage of interlayer O--H bonds. Dielectric permittivity increases with decreasing frequency due to stronger polarization and reduced conduction losses. At very high frequencies, greater conduction losses are responsible for lower values of dielectric permittivity of ERGO papers compared to GO papers. The "U" or "W" profile (σ vs T curves) of temperature dependent conductivity was due to thermally activated transport, residence time and ionic scattering of charge carriers. The recovery of conducting and dielectric properties at higher temperatures were due to the transition from graphene--ion--cloud to a graphene--air dielectric multi-nano-capacitor system. The latter had more sp2--carbon cluster concentration and increased electrical percolation supportive of band-like or variable range electron transport. Higher activation energies along ln σT vs T-1/2 plot are associated with delocalization of charge carriers from their potential wells, thermally activated carrier transport and frequency of the electronic field. [ABSTRACT FROM AUTHOR]

The increasing demand for portable and wearable electronics requires high reliability of devices for continuous miniaturization, and provides challenges for the dimensionally-confined bottom-up assembly methods which typically begin with materials such as graphene oxide (GO). However, GO based devices suffer from complicated synthesis procedures and lower device performance due to the presence of oxygen functionalities on the electrode materials, as well as the need to ensure a good interface between the electrode material and the electrolyte used. Here, a facile, two-step, top-down strategy was used to fabricate thin, all-in-one (PVA/H3PO4)/graphene/graphite paper-like electrodes. The assembled flexible, all-solid-state micro-supercapacitor devices exhibit excellent performance compared to previously reported values, such as a high volumetric capacitance of ~3.6 F·cm-3 even after 20000 cycles. Notably, the devices also showed excellent rate performance with extremely high specific capacitance retention of up to 94% as the current density increased from 0.5 to 5 A·cm-3, indicating promise for high power applications. The paper-like electrodes were tailored to less than 0.5 mm width for further miniaturization and suffered from minimal capacitance attenuation. The excellent mechanical flexibility, capacity, and reliability indicate their promising application in energy storage devices. [ABSTRACT FROM AUTHOR]

Glucose electrochemical sensors based on nanostructures of CuO/Cu(OH)2 onto graphene paper were prepared by thermal (solid) and nanosecond pulsed laser (molten phase) dewetting of a CuO layer 6 nm thin deposited by sputtering. Dewetted systems, obtained without the use of any binder, act as array of nanoelectrodes. Solid state and molten phase dewetting produce nanostructures of copper oxide-hydroxide with different average size, shape and surface composition. Molten phase dewetting originates particles with size below 100 nm, while solid state dewetting produces particles with average size of about 200 nm. Moreover, molten phase dewetting produce drop-shaped nanostructures, conversely nanostructures derived from solid state dewetting are multifaceted. X-ray photoelectron spectroscopy (XPS) characterization revealed that the surface of nanostructures is formed by a copper(II) species CuO and Cu(OH)2. Shape of anodic branch of the cyclic voltammograms of glucose in alkali solution evidenced a convergent diffusion mechanism. Analytical performances in amperometric mode are as good as or better than other sensors based on copper oxide. Amperometric detection of glucose was done at potential as low as 0.4 V versus saturated calomel electrode by both types of electrodes. Linear range from 50 ÎĽ M to 10 mM, sensitivity ranging from 7 to 43 ÎĽ A cmâˆ'2 mMâˆ'1 and detection limit of 7 ÎĽ M was obtained. Good analytical performances were obtained by laser dewetted electrodes with a low copper content up to 1.2 by atoms percentage of the surface. Analytical performance of the proposed electrodes is compliant for the determination of glucose both in blood serum, saliva or tear. [ABSTRACT FROM AUTHOR]