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[en] Conductive polymers are macromolecules that have a conjugated system of π bonds. This feature allows the delocalization of electrons through the molecule and generates the possibility of electrical conduction. Among the first reported conductive polymers we find polyacetylene (PA), poly(p-phenylene) (PPP), poly(p-phenylene vinylene) (PPV), polythiophene (PT), polyaniline (PANI) and polypyrrole (PPy). The discovery of the conductive properties of these polymers led to the quest of applications in electronics and in energy generation. In these areas, systems that meet the current technological needs and have a potential use in satisfying future technological requirements have been developed. The objective of this review article is to give an overview of conductive polymers, reviewing some historical data and demonstrating their importance in technological advancement through their application in photovoltaic cells and electronic devices. (author)
[es]Los polimeros conductores son macromoleculas que presentan un sistema conjugado de enlaces π. Este ordenamiento permite la deslocalizacion de electrones a traves de la molecula y genera la posibilidad de conducir electricidad. Entre los primeros polimeros conductores reportados encontramos al poliacetileno (PA), al poli(p-fenileno) (PPP), al poli(fenilenvinileno) (PPV), al politiofeno (PTf), a la polianilina (PANI) y al polipirrol (PPy). El descubrimiento de las propiedades conductoras de estos polimeros condujo a la busqueda de aplicaciones en electronica y en generacion de energia. En estas areas se han desarrollado sistemas que cumplen con las necesidades tecnologicas actuales y que tienen uso potencial, satisfaciendo necesidades tecnologicas futuras. El objetivo del presente articulo de revision es dar una vision general sobre los polimeros conductores, repasando algunos datos historicos y mostrando su importancia para el avance de la tecnologia mediante su aplicacion en celdas fotovoltaicas y dispositivos electronicos. (autor)
[en] Hybrid energy harvesters based on different physical effects is fascinating, but a rational design for multiple energy harvesting is challenging. In this work, a spring-magnet oscillator-based triboelectric-electromagnetic generator (EMG) with a solar cell cap is proposed. A power was produced by a triboelectric nanogenerator (TENG) and an EMG independently or simultaneously by using a shared spring-magnet oscillator. The oscillator configuration enables versatile energy harvesting with the excellent size scalability and self-packaged structure which can perform well at low frequency ranging from 3.5 to 5 Hz. The solar cell cap mounted above the oscillator can harvest solar energy. Under vibrations at the frequency of 4 Hz, the TENG and the EMG produced maximum output power of 5.46 nW cm−3 and 378.79 μW cm−3, respectively. The generated electricity by the hybrid nanogenerator can be stored in a capacitor or Li-ion battery, which is capable of powering a wireless locator for real-time locating data reporting to a personal cell phone. The light-weight and handy hybrid nanogenerator can directly light a caution light or play as a portable flashlight by shaking hands at night. (paper)
[en] Phase change materials (PCMs) that can store the heat energy obtained from intermittent solar irradiation are very important for solar energy absorption cooling system. In this work, an organic compound that melts at the temperature of 368.2 ± 0.5 K was applied as PCM. The specific heat capacities of the PCM were measured by temperature-modulated differential scanning calorimetry from 198.15 to 431.15 K. The thermodynamic functions of [HT–H298.15] and [ST–S298.15] were then calculated based on the measured heat capacities data. Afterward, the long-term cyclic thermal energy storage stability and thermal stability of the PCM were investigated. The results show that the PCM melted and crystallized at about 368 and 364 K, respectively, with a phase change enthalpy (ΔtransH) of 21 kJ mol−1 (130 J g−1). Additionally, it exhibited good long-term cyclic thermal energy storage stability and thermal stability. Hence, the PCM could be applied as good PCM for solar energy absorption cooling.
[en] We investigate the design and performance of thin-film micro thermoelectric generators (µTEGs) using human body heat for wearable device applications, in which various module structures using different thermal-isolations are examined. A transverse type of µTEG suitable for a thin-film thermopile is employed for the modules. The thermal and electrical insulation of the interspace between the hot and cold plates of the modules is an important factor to determine the output power of the µTEGs. A module using vacuum thermal-isolation gives the performance limit of the µTEGs. On the other hand, an easy-to-fabricate insulator-based thermal-isolation severely degrades the performance. A new module structure using insulator/vacuum-hybrid thermal-isolation also has a device-process-friendly structure and in addition can exhibit high output power close to the performance limit achieved by the vacuum thermal-isolation module, which would be adaptable to the power source of wearable devices for internet-of-humans. (paper)
[en] Highlights: • First ever approach for the possibility of using phosphorene QD in solar cell. • SCC-DFTB coupled with TDDFT calculations are performed. • PQD-fullerene nanocomposites show spatial charge separation. • The nanocomposites possess very small exciton binding energy. • The interfacial charge transfer rate is extremely high. • The charge recombination rate is very poor. Using the self-consistent charge density-functional based tight-binding (SCC-DFTB) method, coupled with time-dependent density functional theory (TDDFT) calculations, for the first time we explore the possibility of use of phosphorene quantum dots in solar energy harvesting devices. The phosphorene quantum dots-fullerene (PQDs-PCBA) nanocomposites show type-II band alignment indicating spatial separation of charge carriers. The TDDFT calculations also show that the PQD-fullerene nanocomposites seem to be exciting material for future generation solar energy harvester, with extremely fast charge transfer and very poor recombination rate.
[en] The present study focuses on the relationship between the structural features and reversible shape memory effect (SME) including the related martensitic transformation (MT) in porous TiNi-based compounds fabricated by self-propagating high-temperature synthesis (SHS) at various ignition temperatures. Exploring the as-synthesized samples (S-1 and S-2) ignited at T 1 = 400 and T 2 = 600 °C, respectively, using a set of research instruments has revealed a key feature that modulates the resultant porous structure and SME parameters. Evidently, the one-step B2 ↔ B19′ MT in both samples is considered to be diffuse within a broad temperature gap, where the hysteresis loop width excels 70 degrees. The fine-porous S-1 indicated the well-developed macrostructure having a rough surface pattern of pore walls, whereas the high-porous S-2 did a dissimilar macrostructure having an even pore surface topology. From a phase-chemical point of view, the metal matrix of S-2 was found to be more homogeneous as compared to that of S-1, that in turn has led to the distinctive SME performance in terms of ε-T upon thermocycling. The extremely heterogeneous S-1 featured by more uniform pore shape and distribution has demonstrated the feasible strain behavior despite the fewer TiNi volume fraction and depressed MT was observed. Conversely, the SME performance for S-2 was shown to be impaired because of the discrepancy in the deformation behavior of small and large pore walls, even though the redundant TiNi volume fraction facilitated the MT. (paper)
[en] Highlights: • Sensitizer loading level is one of the key factors determine the sensitized solar cell performance. • The influence of photo-anode thicknesses on the performance of the QDSSCs are well studied. • The optimized film thickness is around 20 µm. • The film thickness is about twice as the optimal one for dye counterparts. • The light harvesting and charge recombination determines the film thickness. Sensitizer loading level is one of the key factors determined the performance of sensitized solar cells. In this work, we systemically studied the influence of photo-anode thicknesses on the performance of the quantum-dot sensitized solar cells. It is found that the photo-to-current conversion efficiency enhances with increased film thickness and peaks at around 20 μm. The optimal value is about twice as large as the dye counterparts. Here, we also uncover the underlying mechanism about the influence of film thickness over the photovoltaic performance of QDSSCs from the light harvesting and charge recombination viewpoint.
[en] We analyzed the linear energy transfer (LET; energy deposited onto the target per unit length) effects on the scintillation properties of Bi4Ge3O12 (BGO) with an emphasis on the dynamical aspect. We irradiated BGO with 20 MeV H±, 50 MeV He±, and 220 MeV C5+. We observed that the rise and the decay of the scintillation temporal profiles are faster at higher LET. The faster decay at higher LET is attributed to the competition between the radiative transition of self-trapped excitons (STEs) localized at Bi3+ ions and the quenching caused by the interaction between STEs. The faster rise can be explained in terms of the competition between the quenching caused by the interaction between excited states and the formation of the STEs.
[en] Cyanobacteria are a group of phototrophic organisms that have a great ecological and economical importance. There is a growing interest in the evaluation of oxidative stress in relation to the impact of global climate change on natural ecosystems in different trophic levels. The purpose of this study was to elucidate the effects of changing temperatures on biomass and oxidative stress parameters of a native M. aeruginosa (strain named CAAT 2005-3) in culture conditions. For long term experiments (7 days exposure) we used cells from cultures during the exponential growth phase. Three treatments were applied: 23°C (low temperature), 26°C (control) and 29°C (high temperature). The average irradiance in each incubator was 30 μE m-2 s-1 (daily monitored with an IL spectro radiometer) under 14/10 h light/dark photo cycle. The cell biomass was determined by cell count (using an inverted microscope) and chlorophyll concentration (determined spectrophotometrically). The rate of oxidation of the dichlorofluorescein diacetate (DCF-DA), indicating ROS presence, was determined with by fluorescence with a microplate reader and the activity of antioxidant enzyme catalase (CAT) was determined spectrophotometrically. We assessed the production of secondary metabolites by liquid chromatography, followed by tandem mass spectrometry (LC-MS/MS). It was observed a significant increase in the growth rate during the exponential phase and an increased biomass in cultures exposed to 29°C. However, the cellular chlorophyll decreased during the 7 days of exposure. The oxidation rate of DCF-DA was significantly higher at 29°C compared to that observed in 26°C and 23°C. Catalase activity did not differ significantly in 26°C throughout the experiment, however the values at 29°C were significantly higher on days 1 and 4 compared to the other two treatments. The production of secondary metabolites was maximum in the beginning of the experiment and then was significantly reduced on days 2 and 4, compared with control values in cells exposed to 29°C. As conclusion cyanobacteria have adaptive mechanisms that could lead to the replacement of blue-green algae species highly susceptible to oxidative stress by others with a higher system of antioxidant protection. In addition our results support recent findings which proposed that secondary metabolites could act as protein-modulating and protection against ROS. (author)
[en] In the solid Breeder Blanket (BB) concepts both tritium release and heat recovery depend on the thermal performances of the breeding zone. Within the R&D activities of the Helium Cooled Pebble Bed (HCPB) breeding blanket, the knowledge of the thermal diffusivity of the breeder beds is of fundamental importance to model the transient heat transfer during the power pulses of the fusion machine. The aim of the present study is to investigate the thermal diffusivity of the breeder beds at BB relevant conditions; to this end the line heat source probe method was employed together with differential scanning calorimetry. An experimental facility, based on the line heat source probe method, was devised for the investigation of the thermal diffusivity of granular beds at breeder blanket relevant temperatures, mechanical state, purge gas type and pressure. Besides the experimental approach, literature values were used to estimate the specific heat capacity of the breeder materials starting from the specific heat capacity of the constituent compounds based on the mole fraction. In addition to the thermal diffusivity and heat capacity, a preliminary insight on the phase transitions of the reference and advanced ceramic breeder beds is given.