The demands for waste heat energy recovery from industrial production, solar energy, and electronic devices have resulted in increasing attention being focused on thermoelectric materials. Over the ...past two decades, significant progress is achieved in inorganic thermoelectric materials. In addition, with the proliferation of wireless mobile devices, economical, efficient, lightweight, and bio‐friendly organic thermoelectric (OTE) materials have gradually become promising candidates for thermoelectric devices used in room‐temperature environments. With the development of experimental measurement techniques, the manufacturing for nanoscale thermoelectric devices has become possible. A large number of studies have demonstrated the excellent performance of nanoscale thermoelectric devices, and further improvement of their thermoelectric conversion efficiency is expected to have a significant impact on global energy consumption. Here, the development of experimental measurement methods, theoretical models, and performance modulation for nanoscale OTE materials are summarized. Suggestions and prospects for the future development of these devices are also provided.
Organic thermoelectric (OTE) devices play an important role in developing novel thermoelectric devices. Here, the progresses of nanoscale OTE devices from the aspects of structural, materials, measurement, and theoretical methods, as well as some typical optimization strategies are reviewed, and an outlook is given to provide an inspiration for the future development of OTE devices.
Enterocytozoon bieneusi is an important opportunistic pathogen widely distributed in humans and animals that causes diarrhea or fatal diarrhea in immunocompromised hosts. To examine the infection ...status and molecular characteristics of E. bieneusi in pigs, 725 fecal samples were collected from pigs in six areas of Fujian Province. The E. bieneusi genotypes were identified based on the internal transcribed spacer (ITS) regions of the ribosomal RNA (rRNA) gene by nested PCR, and its population genetics were analyzed by multilocus sequence typing (MLST). The results showed that the infection rate of E. bieneusi was 24.4% (177/725), and 11 known genotypes (EbpC, EbpA, CHN‐RR2, KIN‐1, CHG7, CHS5, CM11, CHG23, G, PigEBITS, and D) and 2 novel genotypes (FJF and FJS) were identified. All the genotypes were found to be clustered into zoonotic Group 1. Moreover, 52 positive samples were successfully amplified at minisatellite and microsatellite loci and formed 48 distinct multilocus genotypes (MLGs). Further population structure analyses showed strong genetic linkage disequilibrium (LD) and several recombination events (Rm), indicating that E. bieneusi has a clonal population structure. This study is the first to investigate the prevalence and molecular characteristics of E. bieneusi in Fujian Province and could provide baseline data to control E. bieneusi infection in pigs and humans and deepen our understanding of the zoonotic risk of E. bieneusi and its distribution in China.
Aided by density functional theory with nonequilibrium Green's functions simulations, the thermoelectric (TE) properties of nanoporous carbon nanotube junctions formed by covalently binding carbon ...nanotubes via benzene bridges with either meta‐ or para‐connections are investigated. The results show that the TE performances of meta‐connected nanoporous carbon nanotube junctions are significantly improved due to the influence of destructive quantum interference (DQI) effect. Moreover, the TE properties of meta‐connected carbon nanotube junctions can be further improved by substitution of nitrogen atom and gate voltage. The reason is that the quantum interference patterns can be transformed from DQI to constructive quantum interference (or Fano resonance). The theoretical analysis shows that the TE figure of merit (ZT) for meta‐connected carbon nanotube junctions at room temperature is close to 0.5 near the Fermi level, ≈20 times higher than that of the perfect carbon nanotube junction. These results reveal that quantum interference effect can indeed be used to enhance the TE performance of molecular junctions.
The quantum interference effect is confirmed to be an effective strategy to achieve highly efficient thermoelectric power conversion at room temperature. Furthermore, the maximum of ZT of the nanoporous carbon nanotube junction with meta‐connections is close to 0.5 by nitrogen atom doping and gate voltage, ≈20 times larger than that of the perfect CNT junction.
We investigated the thermoelectric properties of phenalenyl-based molecular devices by using the non-equilibrium Green's function method combined with density function theory. The results show that ...the thermoelectric performance of molecular device can be significantly improved by different contact geometries. The ZT value of the device can reach 1.2 at room temperature, which is two orders of magnitude higher than that of graphene. Moreover, the change of the coupling between molecule and electrodes can also enhance the ZT value. The ZT value can be further optimized to 1.4 at 300 K and 5.9 at 100 K owing to the decrease of electronic thermal conductance and almost unchanged power factor.
Parasitic Entamoeba spp. can infect many classes of vertebrates including humans and pigs. Entamoeba suis and zoonotic Entamoeba polecki have been identified in pigs, and swine are implicated as ...potential reservoirs for Entamoeba histolytica. However, the prevalence of Entamoeba spp. in pigs in southeastern China has not been reported. In this study, 668 fecal samples collected from 6 different regions in Fujian Province, southeastern China, were analyzed to identify three Entamoeba species by nested PCR and sequencing analysis. The overall prevalence of Entamoeba spp. was 55.4% (370/668; 95% CI 51.6% to 59.2%), and the infection rate of E. polecki ST1 was the highest (302/668; 45.2%, 95% CI 41.4% to 49.0%), followed by E. polecki ST3 (228/668; 34.1%, 95% CI 30.5% to 37.7%) and E. suis (87/668; 13.0%, 95% CI 10.5% to 15.6%). E. histolytica was not detected in any samples. Moreover, the coinfection rate of E. polecki ST1 and ST3 was 25.1% (168/668; 95% CI 21.9% to 28.4%), the coinfection rate of E. polecki ST1 and E. suis was 3.7% (25/668; 95% CI 2.3% to 5.2%), the coinfection rate of E. polecki ST3 and E. suis was 0.3% (2/668), and the coinfection rate of E. polecki ST1, E. polecki ST3, and E. suis was 4.0% (27/668; 95% CI 2.5% to 5.5%). A representative sequence (MK347346) was identical to the sequence of E. suis (DQ286372). Two subtype-specific sequences (MK357717 and MK347347) were almost identical to the sequences of E. polecki ST1 (FR686383) and ST3 (AJ566411), respectively. This is the first study to survey the occurrence and to conduct molecular identification of three Entamoeba species in southeastern China. This is the first report regarding mixed infections with E. suis, E. polecki ST1, and E. polecki ST3 in China. More research studies are needed to better understand the transmission and zoonotic potential of Entamoeba spp.
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•A new strategy to independently manipulate the phonon thermal conductivity of two-dimensional superlattice materials.•The strategy is realized by structure defects obtained by ...changing the superlattice arrangement.•The independence of this manipulation method makes it promising to combine with other methods to further regulate thermoelectric properties in such a system further.
Effective regulation of phonon thermal conductivity is crucial for the understanding of phonon transmission and improving thermoelectric (TE) performance. Using density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) method, we investigated the effect of phonon localization induced by aperiodic superlattices on the TE transport properties of superlattices based on monolayer MoS2-MoSe2. The results show that the structural defects obtained by changing the superlattice arrangement can effectively modulate the phonon thermal conductivity independently. In addition, the TE properties of the superlattices increase with temperature and central region length. The maximum value of the TE figure of merit of the aperiodic superlattice can reach 1.38 at 500 K. This implies a new potential strategy for tuning the TE performance of devices by exploiting the arrangements of the aperiodic superlattice.
Excellent thermoelectric performance in molecular junctions requires a high power factor, a low thermal conductance, and a maximum figure of merit (
ZT
) near the Fermi level. In the present work, we ...used density functional theory in combination with a nonequilibrium Green’s function to investigate the thermoelectric performance of carbon chain-graphene junctions with both strong-coupling and weak-coupling contact between the electrodes and the molecules. The results revealed that a room temperature
ZT
of 4 could be obtained for the weak-coupling molecular junction, approximately one order of magnitude higher than that reached by the strong-coupling junction. The reason for this is that strong interfacial scattering suppresses most of the phonon modes in weak-coupling systems, resulting in ultralow phonon thermal conductance. The influence of electrode width, electrode doping, and electrochemical gating on the thermoelectric performance of the weak-coupling system was also investigated, and the results revealed that an excellent thermoelectric performance can be obtained near the Fermi level.
By using first-principles calculations combined with the nonequilibrium Green's function method and phonon Boltzmann transport equation, we systematically investigate the influence of chirality, ...temperature and size on the thermoelectric properties of monolayer WSe
nanoribbons. The results show that the armchair WSe
nanoribbons have much higher ZT values than zigzag WSe
nanoribbons. The ZT values of armchair WSe
nanoribbons can reach 1.4 at room temperature, which is about seven times greater than that of zigzag WSe
nanoribbons. We also find that the ZT values of WSe
nanoribbons increase first and then decrease with the increase of temperature, and reach a maximum value of 2.14 at temperature of 500 K. It is because the total thermal conductance reaches the minimum value at 500 K. Moreover, the impact of width on the thermoelectric properties in WSe
nanoribbons is not obvious, the overall trend of ZT value decreases lightly with the increasing temperature. This trend of ZT value originates from the almost constant power factor and growing phonon thermal conductance.
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