The development of visible-light responsive photocatalysts would permit more efficient use ofsolar energy, and thus would bring sustainable solutions to many environmental issues. Conductivepolymers appear as a new class of very active photocatalysts under visible light. Among them poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most promising conjugated polymer with a widerange of applications. PEDOT nanostructures synthesized in soft templates via chemical oxidativepolymerization demonstrate unprecedented photocatalytic activities for water treatment withoutthe assistance of sacrificial reagents or noble metal co-catalysts and turn out to be better than TiO2as benchmark catalyst. The PEDOT nanostructures exhibit a narrow band gap (E = 1.69 eV) and arecharacterized by excellent ability to absorb light in visible and near infrared region. The novel PEDOTbasedphotocatalysts are very stable with cycling and can be reused without appreciable loss of activity.Interestingly, hollow micrometric vesicular structures of PEDOT are not effective photocatalysts ascompared to nanometric spindles suggesting size and shape dependent photocatalytic properties.The visible-light active photocatalytic properties of the polymer nanostructures present promisingapplications in solar light harvesting and broader fields.

We report on Terahertz detection by inverted band structure HgTe-based Field Effect Transistor. Photoconductivity measurements allow for the observation of cyclotron resonance and Shubnikov-de-Haas-like oscillations. However, an unexpected peak was observed at the critical magnetic field value for which zero mode Landau Levels are crossing. Therefore, this specific feature of TeraHertz photoconductivity spectra can tentatively attributed to this magnetic field driven topological phase transition.

We report terahertz measurements on bulk HgCdTe crystals at the semiconductor- to-semimetal topological transition and InAs/GaSb inverted band structure quantum well. We show that physical parameters of these narrow gap systems driven in specific topological phases can be efficiently extracted by means of terahertz photoconductivity studies.

This paper presents terahertz detectors based on high performance 0.7-μm InP double heterojunction bipolar transistor (DHBT) technology and reports on the analysis of their voltage responsivity over a wide frequency range of the incoming terahertz radiation. The detectors operated without any spatial antennas to couple terahertz radiation to the device and have been characterized in the 0.25 - 3.1 THz range with the responsivities (normalized to 1 W radiant power) of 5 V/W and 200 μV/W measured at 0.35 THz and 3.11 THz, respectively. The InP DHBTs also performed as the imaging single-pixels at room temperature in the raster scanned transmission mode. A set of the sub-terahertz images of plant leaves suggest potential utility of InP DHBT detectors for terahertz imaging dedicated to non-invasive testing of plants.

We derive the explicit expression for the Casimir energy between a sphere and a one-dimensional grating in terms of the sphere and grating reflection matrices. This expression is valid for arbitrary materials, sphere radius, and grating geometric parameters. We then numerically calculate the Casimir energy between a metallic (gold) sphere and a dielectric (fused silica) lamellar grating at room temperature, and we explore its dependence on the sphere radius, grating-sphere separation, and lateral displacement. We quantitatively investigate the geometrical dependence of the interaction, which is sensitive to the grating height and filling factor, and we show how the sphere can be used as a local sensor of the Casimir force geometric features. Toward that end, we mostly concentrate on separations and sphere radii of the same order of the grating parameters (here of the order of1 μm).We also investigate the lateral component of the Casimir force, resulting from the absence of translational invariance. We compare our results with those obtained within the proximity force approximation (PFA). When applied to the sphere only, the PFA overestimates the strength of the attractive interaction, and we find that the discrepancy is larger in the sphere-grating than in the sphere-plane geometry. On the other hand, when the PFA is applied to both the sphere and the grating, it provides a better estimate of the exact results, simply

A double-walled carbon nanotube (DWNT), a coaxial composite of two single walled carbon nanotubes (SWNT), provides a unique model to study interactions between thetwo constituent SWNTs. Combining high resolution transmission electron microscopy (HRTEM), electron diffraction (ED), and resonant Raman scattering (RRS) experiments on the same individual suspended DWNT is the ultimate way to relate unambiguously its atomicstructure, defined by the chiral indices of the coaxial outer/inner SWNTs, and its Raman-active vibration modes. This approach is used to investigate the intertube distance dependence of theG-modes of individual index-identified DWNTs composed of two semiconducting SWNTs.We state the main features of the dependence of the G-mode frequencies on the distance between the inner and outer layers: (i) When the interlayer distance is larger than the nominal van der Waals distance (close to 0.34 nm), a downshift of the inner-layer G-modes with respectto the G-modes in the equivalent SWNTs is measured. (ii) The amplitude of the downshiftdepends on the interlayer distance, or in other words, on the negative pressure felt by the innerlayer in DWNT. (iii) No shift is observed for an intertube distance close to 0.34 nm.