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[en] The study of the spatially resolved physical and compositional properties of materials at the nanoscale is increasingly challenging due to the level of complexity of biological specimens such as those of interest in bioenergy production. Mode synthesizing atomic force microscopy (MSAFM) has emerged as a promising metrology tool for such studies. It is shown that, by tuning the mechanical excitation of the probe–sample system, MSAFM can be used to dynamically investigate the multifaceted complexity of plant cells. The results are argued to be of importance both for the characteristics of the invoked synthesized modes and for accessing new features of the samples. As a specific system to investigate, we present images of Populus, before and after a holopulping treatment, a crucial step in the biomass delignification process.
[en] The paper presents an innovative way to improve the efficiency of solar energy. The requirements for the two components of the solar cell (the substrate material and the nature of the p-n junction) are determined. The necessity of nanotechnological preparation of the solar cell substrate is shown. The conditions under which technical silicon can be considered as a substrate are determined. A physical picture of the growth process of nanoclusters on the substrate surface based on the fundamental physical effect of self-organization of semiconductor systems is given. The least acceptable parameters of the nanocluster material are determined. The mechanism of the formation process of nanoheterogeneous structure is determined. The special role solar cell nanocomponents is revealed. (authors)
[en] Biomass lignin, as a significant renewable resource, is one of the most abundant natural polymers in the world. Here, we report a novel silicon-based material, in which lignin-derived functional conformal network crosslinks the silicon nanoparticles via self-assembly. This newly-developed material could greatly solve the problems of large volume change during lithiation/delithiation process and the formation of unstable solid electrolyte interphase layers on the silicon surface. With this anode, the battery demonstrates a high capacity of ∼3000 mA h g−1, a highly stable cycling retention (∼89% after 100 cycles at 300 mA g−1) and an excellent rate capability (∼800 mA h g−1 at 9 A g−1). Moreover, the feasibility of full lithium-ion batteries with the novel silicon-based material would provide wide range of applications in the field of flexible energy storage systems for wearable electronic devices. (paper)
[en] Full text: We report on devices based on arrays of thermoelectric nanowires capped with a transparent indium tin oxide electrode. Devices feature a response to illumination with visible and infrared light, the latter related to thermoelectric conversion of the heat diffusing through the sample. The photothermoelectric response was recently discovered in graphene-metal junctions and I will discuss these results also. Photo conversion in nanowire arrays, that feature efficient light trapping, may offer a path to nanostructured thermoelectric materials for direct energy conversion of infrared light and across-the-spectrum solar energy harvesting. (authors)
[en] We study the consequences of thermoelastic coupling on heat and stress pulse propagation along equilibrium and nonequilibrium reference states. We use a generalized heat-transport equation accounting for relaxational and nonlinear effects. We compare the obtained results with those for heat pulses without thermoelastic coupling and with previous results obtained by using the relaxational Maxwell–Cattaneo equation for the heat flux without nonlinear terms. The difference of the speed of heat pulses along and against an imposed average heat flux in nonequilibrium states is also obtained.
[en] The influence of the screening effect of the electron-phonon interaction on weakly coupling Fröhlich polaron energy has been investigated in semiconducting nanotubes (NTs). General analytical expressions for the polaron energy have been obtained in arbitrary values of NT radius, taking into account screening as well as considering transitions between subbands of dimensional quantization. The dependence of the polaron energy for ground and excited states on NT radius has been represented on the basis of our numerical calculations. According to research carried out, it has been established that the screening contribution to polaron energy taking into account the virtual transitions from the ground state to subbands n=±1, ±2, ±3, as well as the transitions from the polaron excited state with n=1 to subbands n=-1, ±2, ±3, is significant for a=r0 /rp < 1 values, where r0 is the NT radius. For values of the parameter a≥ 1 the screening contribution to polaron energy decreases with increasing NT radius, but the decrease of binding energy of the polaron due to screening is still more than 50%.
[en] Understanding how to engineer nanomaterials for targeted solar-cell applications is the key to improving their efficiency and could lead to breakthroughs in their design. Proposed mechanisms for the conversion of solar energy to electricity are those exploiting the particle nature of light in conventional photovoltaic cells, and those using the collective electromagnetic nature, where light is captured by antennas and rectified. In both cases, engineered nanomaterials form the crucial components. Examples include arrays of semiconductor nanostructures as an intermediate band (so called intermediate band solar cells), semiconductor nanocrystals for multiple exciton generation, or, in antenna–rectifier cells, nanomaterials for effective optical frequency rectification. Here, we discuss the state of the art in p–n junction, intermediate band, multiple exciton generation, and antenna–rectifier solar cells. We provide a summary of how engineered nanomaterials have been used in these systems and a discussion of the open questions. (topical review)
[en] The hydrogenic impurity binding energy in cylindrical quantum well wire with a finite confining potential including both barriers of finite height and an applied electric and magnetic fields are studied. The polaron effect on the ground-state binding energy are investigated by means of Landau-Pekar variation technique. The results for the binding energy as well as polaronic correction with taking into account polar optical phonon confinement effect are obtained as a function of the applied fields for different position of the impurity. Our calculations are compared with previous results in quantum wires of comparable dimensions.
[en] Investigation of solar energy harvesting in hexagonally arranged Si nanowire (NW) arrays is performed through optimizing the structural parameters, such as array periodicity (P), Si NW diameter (D) and length (L). The results demonstrate that there exist wide P and D/P ‘windows’ for the Si NW arrays, locating around 600 nm and 0.833 (i.e., D = 500 nm), respectively, for achieving enhanced light absorption compared to their thin film counterparts with the same thickness, but with much less materials consumption. Calculation of the ultimate efficiency (UE) indicates that the light trapping capability is not monotonically increased with L, and that UE vibration is found when L is >1000 nm. Comparison of the light absorption spectra for hexagonally and squarely arranged Si NW arrays demonstrates that these two most widely employed array symmetries in practice have little impact on the light trapping capability. (paper)
[en] Ionic liquid-based nanofluids are a very novel group of fluids used for enhancing heat transfer in different applications, especially in solar energy ones where the parabolic trough pipe receiver is subjected to heat flux due to the sun beam radiation. In regard to this new class of fluids, no empirical correlations are available for their heat transfer capabilities inside tubes even if some research on local Nusselt number of regular flow is present in the current literature. This paper introduces new correlation for heat transfer and friction factor in pipes subjected to constant heat flux considering [C4mim] [NTf2] ionic liquid-based nanofluids flow. In addition, the performance evaluation criteria as an optimization parameter between heat transfer enhancement and pressure drop penalty have been evaluated. In this particular application, the flow is laminar, as recommended in low heat flux applications (solar beam radiation), with Reynolds number in the range of 100–2000 and nanoparticles volume concentration varying from 0 to 2.5%. In addition, according to the change in the [C4mim] [NTf2] ionic liquid thermophysical properties with temperature, the Prandtl number consequently has been changed. As an overall conclusion, the proposed correlations can be seen as favorable for the heat transfer enhancement estimation of the parabolic trough for the solar energy applications. Finally, this pioneering class of heat transfer fluids (ionic liquid-based nanofluids) reveals a great potential in advanced heat transfer applications; therefore, the new correlations aim to collaborate to this progress.