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Graphene nanosheet films (GNSF) show great potential as solid lubricants. They, however, usually suffer from short lifetime and low load capability, limiting their further engineering application. In this work, we try to address these crucial challenges, for the first time, by inducing a unique three-dimensional microstructure into the GNSF. The as-prepared three-dimensional graphene nanosheet films (3D-GNSF) are composed of many crumpled and partially standing graphene nanosheets (GNS) that overlap with each other and form a three-dimensional interconnected network. The morphology, composition and structure of the 3D-GNSF are investigated in detail using scanning electron microscope, X-ray diffractometer, transmission electron microscope and X-ray photoelectron spectroscopy to deduce their possible formation mechanism. Tribological tests are conducted in air as a function of contact pressure that is up to about 1GPa. The results suggest it is the unique architecture of the 3D-GNSF that quickly produces a compact and stable sliding interface consisting of GNS against GNS, enabling 3D-GNSF as promising solid lubricants with low friction, excellent anti-wear ability, good durability and high load capability. The authors are grateful to the National Natural Science Foundation of China (51605097) and Training Programs of Innovation and Entrepreneurship for Undergraduates (201811845148) for financial support.

High-quality patterns were successfully prepared by inkjet-printing WO3-PEDOT:PSS composites on different substrates including the rigid FTO glass and most importantly, on flexible PEDOT:PSS/Ag grid/PET. Excellent electrochromic performances can be achieved, including large optical modulation (85.7% optical contrast at the wavelength of 633 nm on FTO glass substrate), fast switching speed (coloration/bleaching time of 2.4/0.8 s on the PEDOT:PSS/Ag grid/PET substrate), instantaneous coloration efficiency (68.8 cm2 C−1) and good cycling stability (up to 10,000 cycles). The effects of the applied potential window during electrochemical evaluation on the electrochromic performances were analyzed in detail. The printed electrochromics films on PEDOT:PSS/Ag grid/PET showed the best electrochemical stability, in agreement with its superior conductivity and transmittance at 633 nm of 0.6 Ω/sq and 66%, respectively. It sustained transmittance modulation of about 75.5% and 53.1% of its first cycle recorded contrast at 633 nm, after being subjected to 1000 and 5000 cycles, respectively, and maintained good electrochemical stability up to 10,000 cycles. Moreover, a robust mechanical stability was also achieved by the printed films on flexible PEDOT:PSS/Ag grid/PET substrate. The film maintained a transmittance modulation of 85.8% of its original contrast after 5000 bending cycles at a curvature radius of 1 cm. The inkjet-printed WO3 nanocomposite based flexible electrochromic displays exhibited excellent electrochromic performance, making it a promising candidate for energy efficient displays, e-books, e-cards and multifunctional electronic devices. NRF (Natl Research Foundation, S’pore)

In this paper, we investigate the (2+1)-dimensional (D) sine-Gordon (SG) equation, to describe the propagation of localized light waves in nonlinear media. The main purpose is to obtain a simple specific form of exact solutions of the (2+1)-D SG equation by Hirota’s bilinear method. The novel dynamical behavior is discussed systematically for some special types of localized excitations, such as multi-dromion, multi-lump, plateau and basin solitons, the quasi-tetragonal breather, and elliptical embedded solitons, which are derived by selecting two arbitrary functions in the solution appropriately. We find that the collision of (2+1)-D solitons could be elastic but also inelastic, depending on the functional form of the solitons.

In this paper, uniform NiO nanoparticles on different substrates were successfully synthesized by a simple and low-cost solvothermal method. The high capacitance (1386 F g−1 at 1 A g−1) and excellent rate capability were achieved for NiO nanoparticle film as supercapacitor electrode. A large optical modulation (63.6% at 550 nm), high coloration efficiency (42.8 cm2 C−1 at 550 nm) and good cycling stability can be achieved when the same NiO nanoparticles are used for electrochromic application. The excellent electrochemical performance is attributed to the uniform nanoparticles morphology and stable chemical bonding of the NiO nanoparticle on the substrates, which shorten the ion diffusion length and greatly facilitated the charge transfer both at the contact interfaces and within the electrode materials during the electrochemical process. In addition, we present a smart supercapacitor which function as a regular energy storage device and simultaneously monitor the level stored energy by visual changes. The findings present great promise for NiO nanoparticle film as practical electrode materials as chromo-supercapacitor.

Vertically aligned hierarchical WO3 nano-architectures on transparent conducting substrate (3×2.5 cm2 in size and sheet resistance Rs=10 Ω) are produced via a template-free solvothermal method. The nanostructured array films with thicknesses of about 1.1 μm show remarkable enhancement of the electrochromic properties in visible spectrum and infrared region. In particular, a significant optical modulation (66.5% and 66.0% at 633 nm, 73.8% and 53.9% at 2000 nm, 57.7% and 51.7% at 8 μm), fast switching speed (4.6 s/3.6 s and 2.0 s/3.4 s), high coloration efficiency (126 and 120 cm2 C−1 at 633 nm) and excellent cycling stability (maintained 77.5% and 81.7% of the initial optical modulation after 4500-cycles) are achieved for the nanotree and nanowire arrays, respectively. The improved electrochromic properties are mainly attributed to the vertically aligned structure and the porous space among the nanotrees or nanowires, which make the diffusion of H+ in these arrays easier and also supply larger surface area for charge-transfer reactions.

The WO 3 /PANI core/shell nanowire array is prepared by the combination of solvothermal and electropolymerization methods. The core/shell nanowire array film shows remarkable enhancement of the electrochromic properties. In particular, a significant optical modulation (59% at 700 nm), fast switching speed, high coloration efficiency (86.3 cm 2 C −1 at 700 nm) and excellent cycling stability are achieved for the core/shell nanowire array film. The improved electrochromic properties are mainly attributed to the formation of the donor–acceptor system, and the porous space among the nanowires, which can make fast ion diffusion and provide larger surface area for charge-transfer reactions. The data indicate great promise for the WO 3 /PANI core/shell nanowire array as a potential multicolor electrochromic material.

One-dimension MnCo 2 O 4 nanowire arrays are synthesized on nickel foam by a facile hydrothermal method. The MnCo 2 O 4 nanowires are highly crystalline with an average diameter of 70 nm and exhibit excellent properties for electrochemical energy storage. Impressively, the MnCo 2 O 4 nanowire array exhibits noticeable pseudocapacitive performance with a high capacitance of 349.8 F g −1 at 1 A g −1 and 328.9 F g −1 at 20 A g −1 as well as excellent cycling stability. As an anode material for Li-ion batteries, the MnCo 2 O 4 nanowire array delivers an initial specific discharge capacity of 1288.6 mAh g −1 at 100 mA g −1 , with reversible capacity retention of 92.7% after 50 cycles. The outstanding electrochemical performances are mainly attributed to its nanowire array architecture which provides large reaction surface area, fast ion and electron transfer and good structure stability.

Ultra-thin WO3 nanorods (NRs) embedded polyaniline (PANI) composite thin films were synthesized by embedding WO3 NRs into polyaniline using a surface-initiated-polymerization method, followed by spin-coating deposition. The ultra-thin WO3 NRs with length of 60 nm and diameter of 4 nm were prepared by a solvothermal method. The nanofillers were well-dispersed in the polymer matrix. The nanocomposites were finally deposited onto ITO-coated glass via spin-coating technology. The electrochromic contrast, switching speed, and durability of the composite films were investigated in details. The composite film, being a dual electrochromic material, varied from purple to green, light yellow and finally dark blue. The switching speed (0.9 s) is much faster than the films only composed of WO3 NRs. The durability of the hybrid film was enhanced compared with neat WO3 NRs film.

Periodical bowl-like macroporous WO3 array film was electrodeposited on ITO glasses using self-assembled monolayer polystyrene (PS) spheres as template. The film showed a connected network of close-packed hemisphere pores (microbowl arrays) with average size of 600 nm after the template was removed. The structure of the film revealed by XRD and TEM was that nanocrystals embedded into an amorphous matrix. The electrochromic property of the WO3 microbowl array film was examined in 0.5 M H2SO4 solution. Compared with dense film prepared without PS template, the WO3 microbowl array film showed superior electrochromic property with coloration efficiency of 68 cm2 C−1, response times of 3.6 s (coloration) and 1.0 s (bleaching), and without significant change in cyclic stability.

Nanostructured nickel oxide (NiO) thin films were prepared by a simple electrodeposition in choline chloride-based ionic liquid followed by an oxidation in air. Uniform granules and some voids opened between these granules were presented in the polycrystalline NiO films deposited for 10 and 30 s, but the film became compact as the deposition time increased to 60 s. The optical transmittance of the film decreased with the increase of the film thickness. All the NiO films exhibit high coloration efficiency, fast electrochromic switching and good cycling durability. The ultra fast switching time (0.74 s and 0.88 s) and maximum coloration efficiency of 250 cm2 C−1 were observed for the film deposited for 10 s.