Electrostatic-Interaction-Assisted Construction of 3D Networks of Manganese Dioxide Nanosheets for Flexible High-Performance Solid-State Asymmetric Supercapacitors

A three-dimensional (3D) macroscopic network of manganese oxide (MnO₂) sheets was synthesized by an easily scalable solution approach, grafting the negatively charged surfaces of the MnO₂ sheets with an aniline monomer by electrostatic interactions followed by a quick chemical oxidizing polymerization reaction. The obtained structure possessed MnO₂ sheets interconnected with polyaniline chains, producing a 3D monolith rich in mesopores. The MnO₂ sheets had almost all their reactive centers exposed on the electrode surface, and combined with the electron transport highways provided by polyaniline and the shortened diffusion paths provided by the porous structure, the deliberately designed electrode achieved an excellent capacitance of 762 F g^–1 at a current of 1 A g^–1 and cycling performance with a capacity retention of 90% over 8000 cycles. Furthermore, a flexible asymmetric supercapacitor based on the constructed electrode and activated carbon serving as the positive and negative electrodes, respectively, was successfully fabricated, delivering a maximum energy density of 40.2 Wh kg^–1 (0.113 Wh cm^–2) and power density of 6227.0 W kg^–1 (17.44 W cm^–2) in a potential window of 0–1.7 V in a PVA/Na₂SO₄ gel electrolyte

Self-standing microporous films of arrayed alumina nano-fibers including Schiff base molecules: effect of the environment around the molecules on their photo-luminescence

<p>A self-standing, flexible and transparent microporous film made of alumina nano-fibers is applied as a host to design new functional hybrid materials. Luminescent Schiff base molecules, <em>N-</em>salicylidene-<em>p</em>-toluidine, were found to fully, stably, and homogeneously occupy the slit-like micropore of the film from X-ray diffraction, optical spectra, and N_{<font size="2">2</font>} gas adsorption isotherm measurements. Photoluminescence (PL) intensity of the hybrid film was sensitive to the type of transition metal ions dispersed in aqueous solution. For example, Zn^{<font size="2">2+</font>} and Cu^{<font size="2">2+</font>} ions in the solutions were involved with the apparent increase and decrease of the PL intensity, respectively. This unique alumina film has high potential to be a candidate of a host matrix for designing new hybrid materials with noble functions.</p><br /

Semiconductor SERS enhancement enabled by oxygen incorporation

<p>Semiconductor-based surface-enhanced Raman spectroscopy (SERS) substrates represent a new frontier in the field of SERS. However, the application of semiconductor materials as SERS substrates is still seriously impeded by their low SERS enhancement and inferior detection sensitivity, especially for non-metal-oxide semiconductor materials. Herein, we demonstrate a general oxygen-incorporation-assisted strategy to magnify the semiconductor substrate–analyte molecule interaction, leading to significant increase in SERS enhancement for non-metal-oxide semiconductor materials. Oxygen incorporation in MoS₂ even with trace concentrations can not only increase enhancement factors by up to 100,000 folds compared with oxygen-unincorporated samples, but also endow MoS₂ with low limit of detection below 10^-7 M. Intriguingly, combined with the findings in previous studies, our present results indicate that both oxygen incorporation and extraction processes can result in SERS enhancement, probably due to the enhanced charge-transfer resonance as well as exciton resonance arising from the judicious control of oxygen admission in semiconductor substrate.</p

Rational design of galvanically replaced Pt-anchored electrospun WO3 nanofibers as efficient electrode materials for methanol oxidation

<p>We develop a simple dry wrapping method to fabricate a tungsten oxide (WO_{<font size="2">3</font>})/carbon nanotube (CNT) cable, in which WO_{<font size="2">3</font>} layers act as an electrochromic component while aligned CNTs as the core provide mechanical support and an anisotropic, continuous electron transport pathway. Interestingly, the resultant cable material exhibits an obvious gradient electrochromic phenomenon.</p><br /

Rational design of galvanically replaced Pt-anchored electrospun WO 3 nanofibers as efficient electrode materials for methanol oxidation

Platinum/tungsten oxide (Pt/WO3) is a very important hybrid material system, which has been found to have wide applications from photochemistry to heterogeneous catalysis. For the first time we combine electrospinning and galvanic replacement reaction as a new fabrication method for the in-situ anchoring of galvanically replaced Pt nanocubes and nanospheres onto the surface of electrospun WO3 nanofibers to yield a 1D heterostructure. This constructed nanostructure tied with carbon nanotubes as a novel nanostructured three-phase electrode for methanol oxidation exhibits exceptional catalytic activity. It is found that the morphology of both the Pt nanostructures and tungsten oxide support play an important role in the catalytic activity and stability for methanol oxidation. The peak current density of Pt nanocubes-anchored to WO3 nanofibers is about 4.5 times higher than that of their spherical counterparts under the same condition. The current decay with time for the Pt nanocubes/ WO3 nanofibers is much slower than that for Pt nanocubes/commercial WO3. The novel<br />multidimensional, multicomponent and multifunctional Pt/WO3 nanostructures offer a new material platform for solar cells, photocatalysis, fuel cells, sensors, and other applications. Such a hybrid design has been demonstrated to be an effective means for bridging functional nanoscale entities with a practical macroscale device