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In this paper, we report a new kind of beam, named “spoon-like” beams, generated with the exponential phase. The intensity distributions and transverse energy flow of the spoon-like beam at the focal plane are analyzed theoretically and experimentally. The results demonstrate that the size of the spoon-like beam becomes enlarged with the increasing power exponent n, and the length of the spoon-like intensity trajectory becomes shorter with the increasing parameter p. Furthermore, there is an intensity gradient along the spoon-like trajectory of the beam, which introduces the intensity-gradient force exerted onto microparticles. The experiment on optical tweezers demonstrates that the focused beams can create spoon-like traps for the two-dimensional manipulation of particles.

WSe2 films were prepared on inexpensive graphite substrate through direct-current magnetron sputtering and rapid selenization for catalytic application in the hydrogen evolution reaction (HER). The effects of the temperature and time in selenization process on the HER activity were studied in details. Scanning electron microscopy and Raman spectroscopy indicates that the graphite surface is covered by WSe2 nanosheets. The HER activity of WSe2 samples prepared at different conditions has been evaluated via linear sweep voltammetry. Through adjusting selenization parameters, the WSe2 nanofilms consists of the proper nanosheets has been prepared with the optimal HER activity. It’s important to control the number, the size and crystallinity of WSe2 nanosheets which take responsibility for the HER activity. WSe2 electrodes prepared at 500 °C for 10 min exhibit high stability in acidic solution and get the optimal activity with an over potential around −179 mV vs reversible hydrogen electrode (RHE) at the current density of 10 mA cm−2.

Inexpensive graphite substrate is applied to grow WSe2 nanofilms for catalytic application in the hydrogen evolution reaction. W nanofilms with a thickness of about 10 nm were deposited onto the graphite substrate by direct-current magnetron sputtering. The graphite with 10 nm W nanofilms was rapidly selenized at 600 °C in horizontal tube furnace to form WSe2 nanofilms. Scanning electron microscopy, Raman spectroscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy indicated that graphite surface was covered by nano-sized vertically aligned WSe2 platelets. The effects of the N2 pressure in the selenization process on the HER performance have been studied in details. Turning of the selenization parameters can optimize the HER performance of the WSe2 nanofilms, which has been evaluated via linear sweep voltammetry and Tafel slope. WSe2 nanofilms prepared at the highest N2 pressure of 0.08 MPa behave optimal performance. The current density reaches 10 mA cm−2 at an over potential around −189 mV vs reversible hydrogen electrode and corresponding Tafel slopes is ∼72 mV dec−1. WSe2 nanofilms electrodes exhibit high stability in acidic solution which shows no degradation after 10000 continuous cycles. Thus, WSe2 nanofilms exhibit superior electrocatalytic performance which is much better than those recently reported grown on carbon paper substrate and W foil.

Reduced graphene oxide (RGO) sheets with varied contents and types of oxygenated groups were synthesized by Hummers treatment of natural graphite powders followed by different nontoxic and mild reduction methods, which include thermal and chemical reduction with ethylene glycol, KOH and Fe powder. The changes in microstructure and surface chemistry of RGOs were extensively characterized by SEM, TEM, AFM, XRD, XPS and Raman spectrum. The results show that significant exfoliation occurs during oxidation and is retained in reduction processes, along with the formation of curled wavy morphology. Compared with large d spacing (0.852 nm) of graphene oxide (GO), the (002) plane distance decreases to 0.358-0.384 nm of RGOs, indicating efficient tuning of surface functionalities through mild reduction methods. The I D/I G ratio of RGOs is about 1.0-1.15, indicating that reconstructed sp2 domains have smaller sizes and larger quantity. The content of sp2 bonded C in GO (36.93%, molar fraction) increases to 45.48%-72.92% (molar fraction) in RGOs, along with a drastic decrease in hydroxyl and epoxy and minor changes in carbonyl and carboxyl. Thermal reduction or chemical reduction produces RGOs with residual functionalities, which may render different chemical activity and is desirable in various applications.

A porous ternary nanocomposite based on graphene, RuO2 and TiO2 has been prepared via a facile in-situ co-assembly without any surfactants. A unique morphology of highly-curled graphene sheets loaded with sporadic spots or coatings comprised of mixed RuO2 and TiO2 nanodots was achieved for the first time. This uniform decoration indicates strong interaction between graphene and the as-grown nanoparticles favoring the full separation of graphene sheets. The formation mechanism of such a porous but tightly bonded hetero-nanostructure benefiting from linking effect of TiO2 is proposed. Electrochemical tests showed a characteristic capacitive behavior and the specific capacitance values of 216.7–396.5 F/g depending on the ratios of Ru/Ti, which has potential for energy storage.

Using graphene oxide and hydrous ruthenium chloride as starting materials, RuO 2 /graphene composites were prepared via a hydrothermal reaction under different precipitation conditions by using ammonium carbonate, urea, and sodium hydrate as precipitants. The morphology and structure of the RuO 2 /graphene composites were characterized by SEM, TEM, XRD. Cyclic voltammetry, galvanostatic charge–discharge, and impedance measurements were carried out to test the electrochemical performance. The results revealed that the veil-like RuO 2 /graphene composite prepared by sodium hydrate precipitation showed better capacitance performance than a particle-like composite prepared by ammonium carbonate and urea precipitation. A disproportionation reaction from Ru 3+ to Ru and RuO 2 took place in the RuO 2 /graphene composite when using CO(NH 2 ) 2 as the precipitant. The RuO 2 /graphene composite using sodium hydrate as the precipitant exhibited the optimum electrochemical performance with superior specific capacitance of 528.5 F g −1 at 0.1 A g −1 , minimum resistance (0.4 Ω), and excellent rate performance and cycling stability, suggesting the synergetic effects of the Ru(OH) δ Cl 3−δ precursors and graphene oxide during the hydrothermal process.

We report here characterization of the interfacial microstructure and properties of titanium dioxide (TiO2) nanotube array films fabricated by anodization. Field effect scanning electron microscopy (FESEM), X-ray diffraction (XRD), nanoindentation, atomic force microscopy (AFM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the interface of the film. With increasing annealing temperature from 200 °C to 800 °C, the interfacial fusion between the film and the Ti substrate increased. The phase transformation of the TiO2 nanotube film from amorphous to anatase to rutile took place gradually; as the phase transformation progressed, the force needed to break the film increased. The growth of TiO2 nanotube arrays occurs in four stages: barrier layer formation, penetrating micropore formation, regular nanotube formation, and nanofiber formation. The TiO2 nanotubes grow from the Schottky interface layer rather than from the Ti substrate. The Schottky interface layer's thickness of 35–45 nm was identified as half the diameter of the corresponding nanotube, which shows good agreement to the Schottky interface layer growth model. The TiO2 nanotube film was amorphous and the Ti substrate was highly crystallized with many dislocation walls.

Nanocomposites of reduced graphene oxide (RGO) sheets decorated with amorphous ruthenium oxide nanoparticles are fabricated through a one-pot hydrothermal process without additional dispersants. During the hydrothermal reduction, unilamellar graphene sheets with curved and veil-like morphology are formed and multilamellar graphene sheets are further separated by amorphous RuO2·xH2O with a particle size of 3–8 nm. The nanocomposites exhibit evident pseudo capacitance behavior and the comprehensive electrochemical performance is improved markedly compared with that of the single components. When the precursor ratio of graphene oxide (GO) to RuCl3·xH2O is 2:10, the graphene–RuO2 (GR) nanocomposite electrode achieves the highest specific capacitance of 542.5 F g−1 and the minimum ESR value of 1.21 Ω at 0.1 A g−1, retaining 94% after 1000 cycles at 1 A g−1. Thus graphene sheets/ruthenium oxide nanocomposites bode well for a promising candidate in supercapacitor technology.