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Polymers are usually considered thermal insulators, because the amorphous arrangement of the molecular chains reduces the mean free path of heat-conducting phonons. The most common method to increase thermal conductivity is to draw polymeric fibres, which increases chain alignment and crystallinity, but creates a material that currently has limited thermal applications. Here we show that pure polythiophene nanofibres can have a thermal conductivity up to ∼ 4.4 W m(-1) K(-1) (more than 20 times higher than the bulk polymer value) while remaining amorphous. This enhancement results from significant molecular chain orientation along the fibre axis that is obtained during electropolymerization using nanoscale templates. Thermal conductivity data suggest that, unlike in drawn crystalline fibres, in our fibres the dominant phonon-scattering process at room temperature is still related to structural disorder. Using vertically aligned arrays of nanofibres, we demonstrate effective heat transfer at critical contacts in electronic devices operating under high-power conditions at 200 °C over numerous cycles.

Photocatalytic degradation mechanismFigure S1 displays the mechanism for the photocatalytic degradation involved in the operation of the TiO 2 /Au/Mg-micromotor. The new micromotors consist of a photoactive TiO 2 surface layer embedded with Au nanoparticles for photodecomposition. Under UV irradiation, the photogenerated positive holes react with adsorbed water and produce strong oxidizing hydroxyl radicals. In addition, the photogenerated free electrons react with adsorbed molecular O 2 to produce superoxide anions that could also contribute to the production of peroxide radicals, hydroxyl radicals, and hydroxyl anions. The complete mineralization of CWAs has been achieved due to coupled oxidation-reduction carried out by the highly active radicals and anions.The presence of the Au nanoparticles can effectively shift the Fermi level of TiO 2 and enhance the charge carrier separation to extend the lifetime of the generated radicals and anions, which results in an enhanced photocatalytic efficiency.

Self‐propelled activated carbon‐based Janus particle micromotors that display efficient locomotion in environmental matrices and offer effective ‘on‐the‐fly’ removal of wide range of organic and inorganic pollutants are described. The new bubble‐propelled activated carbon Janus micromotors rely on the asymmetric deposition of a catalytic Pt patch on the surface of activated carbon microspheres. The rough surface of the activated carbon microsphere substrate results in a microporous Pt structure to provide a highly catalytic layer, which leads to an effective bubble evolution and propulsion at remarkable speeds of over 500 μm/s. Such coupling of the high adsorption capacity of carbon nanoadsorbents with the rapid movement of these catalytic Janus micromotors, along with the corresponding fluid dynamics and mixing, results in a highly efficient moving adsorption platform and a greatly accelerated water purification. The adsorption kinetics and adsorption isotherms have been investigated. The remarkable decontamination efficiency of self‐propelled activated carbon‐based Janus micromotors is illustrated towards the rapid removal of heavy metals, nitroaromatic explosives, organophosphorous nerve agents and azo‐dye compounds, indicating considerable promise for diverse environmental, defense, and public health applications.

Nonpolar liquids do not easily accommodate electric charges, but it is known that surfactant additives can raise the conductivity and lead to electric charging of immersed solid surfaces. Here, we study the rarely considered conductivity effects induced by surfactant molecules without ionizable groups. Precision conductometry, light scattering, and Karl Fischer titration of sorbitan oleate solutions in hexane reveal a distinctly electrostatic action of the nonionic surfactant. The conductivity in dilute hexane solutions of sorbitan trioleate (Span 85) exhibits two regimes of linear scaling with surfactant concentration and a transition around the critical micelle concentration (cmc). Both regimes can be described with a statistical model of equilibrium charge fluctuations. The behavior observed above the cmc has a direct analogy in systems of ionic surfactants and can be explained by charge disproportionation of reverse micelles. The observed conductivity of Span 85 solutions below the cmc, however, represents a qualitative departure from the behavior reported for ionic surfactants. In the studied surfactant systems, the availability of ionic species may stem from a complexation of the surfactant with ionizable impurities; nonetheless, the ionization process appears to be limited entirely by the surfactant and not by the level of impurity. We therefore propose that nonionizable surfactants can offer a new and robust way of controlling the conductivity in nonpolar liquids.

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An optical rectenna--a device that directly converts free-propagating electromagnetic waves at optical frequencies to direct current--was first proposed over 40 years ago, yet this concept has not been demonstrated experimentally due to fabrication challenges at the nanoscale. Realizing an optical rectenna requires that an antenna be coupled to a diode that operates on the order of 1 PHz (switching speed on the order of 1 fs). Diodes operating at these frequencies are feasible if their capacitance is on the order of a few attofarads, but they remain extremely difficult to fabricate and to reliably couple to a nanoscale antenna. Here we demonstrate an optical rectenna by engineering metal-insulator-metal tunnel diodes, with a junction capacitance of ∼2 aF, at the tip of vertically aligned multiwalled carbon nanotubes (∼10 nm in diameter), which act as the antenna. Upon irradiation with visible and infrared light, we measure a d.c. open-circuit voltage and a short-circuit current that appear to be due to a rectification process (we account for a very small but quantifiable contribution from thermal effects). In contrast to recent reports of photodetection based on hot electron decay in a plasmonic nanoscale antenna, a coherent optical antenna field appears to be rectified directly in our devices, consistent with rectenna theory. Finally, power rectification is observed under simulated solar illumination, and there is no detectable change in diode performance after numerous current-voltage scans between 5 and 77 °C, indicating a potential for robust operation.

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