Ab initio study of temperature-dependent piezoelectric and electronic properties of thermally stable GaPO4.

Gallium-phosphate (GaPO4) is one of the ultra-high thermally stable piezoelectric materials with a high critical temperature of 1206 K. Here, first principles calculations with quasi-harmonic approximation are performed to study thermal and other physical properties of α-GaPO4. For the electronic structure, we focus on the electron-phonon interaction and lattice expansion effects on the temperature-dependent band gap, which plays a significant role in zero-point renormalization. Significantly, the large piezoelectric constants e11 primarily comes from intrinsic sensitivity of Ga and O sites to axial strain, while P atoms contribute little, which remains true in other quartz-like type APO4 (A = B, Al, In). Our work provides an insight into the temperature-dependent electronic and piezoelectric properties of α-GaPO4 and motivates its applications in a high temperature environment.

Switch of Thermal Expansions Triggered by Itinerant Electrons in Isostructural Metal Trifluorides.

Manageable thermal expansion (MTE) of metal trifluorides can be achieved by introducing local structure distortion (LSD) in the negative thermal expansion ScF3. However, an open issue is why isostructural TiF3, free of LSD, exhibits positive thermal expansion. Herein, a combined analysis of synchrotron X-ray diffraction, X-ray pair distribution function, and rigorous first-principles calculations was performed to reveal the important role of itinerant electrons in mediating soft phonons and lattice dynamics. Metallic TiF3 demonstrates itinerant electrons and a suppressed Grüneisen parameter γ ≈ -20, while insulating ScF3 absence of itinerant electrons has a considerable γ ≈ -120. With increasing electron doping concentrations in ScF3, soft phonons become hardened and the γ is repressed significantly, identical to TiF3. The presented results update the thermal expansion transition mechanism in framework structure analogues and provide a practical approach to obtaining MTE without inducing sizable structure distortion.

First-principles study on bilayer SnP3 as a promising thermoelectric material.

The bilayer SnP3 is recently predicted to exfoliate from its bulk phase, and motivated by the transition of the metal-to-semiconductor when the bulk SnP3 is converted to the bilayer, we study the thermoelectric performance of the bilayer SnP3 using first-principles combined with Boltzmann transport theory and deformation potential theory. The results indicate that the bilayer SnP3 is an indirect band gap semiconductor and possesses high carrier mobility. The high carrier mobility results in a large Seebeck coefficient observed in both n- and p-doped bilayer SnP3, which is helpful for acquiring a high figure of merit (ZT). Moreover, by analyzing the phonon spectrum, relaxation time, and joint density of states, we found that strong phonon scattering makes the phonon thermal conductivity extremely low (∼0.8 W m-1 K-1 at room temperature). Together with a high power factor and a low phonon thermal conductivity, the maximum ZT value can reach up to 3.8 for p-type doping at a reasonable carrier concentration, which is not only superior to that of the monolayer SnP3, but also that of the excellent thermoelectric material SnSe. Our results shed light on the fact that bilayer SnP3 is a promising thermoelectric material with a better performance than its monolayer phase.

Ultrahigh thermoelectric performance of Janus α-STe2 and α-SeTe2 monolayers.

Janus α-STe2 and α-SeTe2 monolayers are investigated systematically using first-principles calculations combined with semiclassical Boltzmann transport theory. Janus α-STe2 and α-SeTe2 monolayers are indirect semiconductors with band gaps of 1.20 and 0.96 eV, respectively. It is found that they possess ultrahigh figure of merit (ZT) values of 3.9 and 4.4, respectively, at 500 K, much higher than that of the pristine α-Te monolayer (2.8). The higher ZT values originating from Janus structures reduce lattice thermal conductivities remarkably compared with the pristine α-Te monolayer. The much higher phonon anharmonicity in Janus monolayers leads to significantly lower lattice thermal conductivity. It is also found that electronic thermal conductivity can play an important role in thermoelectric efficiency of materials with quite low lattice thermal conductivity. This work suggests the potential applications of Janus α-STe2 and α-SeTe2 monolayers as thermoelectric materials and highlights that using a Janus structure is an effective way to enhance thermoelectric performance.

Theoretically modelling graphene-like carbon matryoshka with strong stability and particular three-center two-electron π bonds.

Carbon materials based on different hybridization of carbon atoms have drawn great attention because of their unique configurations and physical and chemical properties. Here, a previously unknown 2D carbon allotrope named L-2Gy, graphene-like carbon matryoshka graphynes (Gy) with two alkynyls (C[triple bond, length as m-dash]C) inserted into the three-fold carbon atoms of graphene, has been constructed with considerable thermal, dynamical, and mechanical stability by using ab initio density functional theory. With the increasing number of alkynyls between the three-fold carbon atoms of graphene, the stability of Gy will seriously decrease. L-2Gy has a fascinating chemical bond environment consisting of sp- and sp2-hybridized carbon atoms, and delocalized π electrons derived from the 27 three-center two-electron π bonds. This particular electronic structure plays a vital role in chemically stabilizing L-2Gy. The electronic band structure reveals the semi-metallic features of L-2Gy mainly contributed by the px/z orbitals of carbon atoms. Furthermore, compared with the acknowledged catalysts for the hydrogen evolution reaction (HER), L-2Gy, as a 2D carbon allotrope, shows excellent catalytic activity for the HER.

Comparative investigation of the thermal transport properties of Janus SnSSe and SnS2 monolayers.

Recently, Janus two-dimensional (2D) materials as a new member of 2D derivatives have been receiving much attention due to their novel properties. In this work, the lattice thermal conductivity κL of the Janus SnSSe monolayer is investigated based on first-principles calculations, while that of the SnS2 monolayer is studied for comparison. It is found the the κL values of SnSSe and SnS2 are 13.3 and 11.0 W m-1 K-1 at room temperature, and acoustic branches dominate their thermal transport. Weaker phonon anharmonicity in SnSSe leads to a slightly higher κL, though it has weaker phonon harmonicity. The smaller Grüneisen parameters of TA and LA phonons lower than 1 THz in SnSSe indicate weaker phonon anharmonicity, resulting in a higher κL. Finally, the size effect and boundary effect are also investigated, exhibiting that the κL can further decrease at the nanoscale. Our work suggests that Janus SnSSe and SnS2 have a much lower κL compared with conventional transition metal dichalcogenides (TMDs) and are potential competitors in the thermoelectric field.

Thermal transport properties of novel two-dimensional CSe.

Recently, as a novel member of the IV-VI group compounds, two-dimensional (2D) buckled monolayer CSe has been discovered for use in high-performance light-emitting devices (Q. Zhang, Y. Feng, X. Chen, W. Zhang, L. Wu and Y. Wang, Nanomaterials, 2019, 9, 598). However, to date, the heat transport properties of this novel CSe is still lacking, which would hinder its potential application in electronic devices and thermoelectric materials that can generate electricity from waste heat. Here we systematically study the heat transport properties of monolayer CSe based on ab initio calculations and phonon Boltzmann transport theory. We find that the lattice thermal conductivity κlat of monolayer CSe is around 42 W m-1 K-1 at room temperature, which is much lower than those of black phosphorene, buckled phosphorene, MoS2, and buckled arsenene. Moreover, the longitudinal acoustic phonon mode contributes the most to the κlat, which is much larger than those of the out-of-plane phonon mode and transverse acoustic branches. The calculated size-dependent κlat shows that the sample size can significantly reduce the κlat of monolayer CSe and can persist up to 10 µm. These discoveries provide new insight into the size-dependent thermal transport in nanomaterials and guide the design of CSe-based low-dimensional quantum devices, such as thermoelectric devices.

Potential molecular semiconductor devices: cyclo-Cn (n = 10 and 14) with higher stabilities and aromaticities than acknowledged cyclo-C18.

The successful synthesis and isolation of cyclo-C18 in experiments is a ground-breaking development in carbon rings. Herein, we studied the thermodynamic stabilities of cyclo-Cn (4 ≤ n ≤ 34) with hybrid density functional theory. When n = 4N + 2 (N is an integer), cyclo-Cn were thermodynamically stable. In particular, cyclo-C10 and cyclo-C14 were more thermodynamically, kinetically, dynamically, and optically stable compared with the acknowledged cyclo-C18, and were potential candidates for zero-dimensional carbon rings. Cyclo-Cn (n = 10 and 14) show similar molecular semiconductor characteristics to the acknowledged cyclo-C18. The carbon atoms were sp hybridized in cyclo-C10, cyclo-C14, and cyclo-C18. Cyclo-C14 and cyclo-C18 had alternating abnormal single and triple bonds, but cyclo-C10 had equal bonds. Cyclo-C10, cyclo-C14, and cyclo-C18 with large aromaticities had out-of-plane and in-plane π systems, which were perpendicular to each other. The number of π electrons in the out-of-plane and in-plane π systems, respectively, followed the standard Hückel aromaticity rule. Simulated UV-vis-NIR spectra indicated similar electronic structures of cyclo-C14 and cyclo-C18.

Three metallic BN polymorphs: 1D multi-threaded conduction in a 3D network.

In this paper, three novel metallic sp2/sp3-hybridized boron nitride (BN) polymorphs are proposed by first-principles calculations. One of them, denoted as tP-BN, is predicted based on the evolutionary particle swarm structural search. tP-BN is composed of two interlocked rings forming a tube-like 3D network. The stability and band structure calculations show that tP-BN is metastable and metallic at zero pressure. Calculations for the density of states and electron orbitals confirm that the metallicity originates from the sp2-hybridized B and N atoms, forming 1D linear conductive channels in the 3D network. According to the relationship between the atomic structure and electronic properties, another two 3D metastable metallic sp2/sp3-hybridized BN structures are constructed manually. Electronic property calculations show that both of these structures have 1D conductive channels along different axes. The polymorphs predicted in this study enrich the structures and provide a different picture of the conductive mechanism of BN compounds.

Ultra-low lattice thermal conductivity of monolayer penta-silicene and penta-germanene.

We study the lattice thermal conductivity of two-dimensional (2D) pentagonal systems, such as penta-silicene and penta-germanene. Penta-silicene has been recently reported, while the stable penta-germanene, made up of another group IV element, is first revealed by our ab initio calculations. We find that both penta-silicene and penta-germanene at room temperature have ultra-low lattice thermal conductivities, κ, of 1.29 W m-1 K-1 and 0.30 W m-1 K-1, respectively. To the best of our knowledge, penta-germanene may have the lowest κ in 2D crystal materials. We attribute the ultra-low κ to the weak phonon harmonic interaction and strong anharmonic scattering. A small phonon group velocity, a small Debye frequency, a large Grüneisen parameter, and a large number of modes available for phonon-phonon interplay together lead to the ultra-low κ of penta-silicene and penta-germanene. These discoveries provide new insight into the manipulation of ultra-low κ in 2D materials and highlight the potential applications of silicon and germanium based high thermoelectric materials.

Hand-spinning chrysotile exposure and risk of malignant mesothelioma: A case-control study in Southeastern China.

While chrysotile has been commonly used by Chinese textile industry for many years, investigations on the association of chrysotile exposure with risk of mesothelioma in China are scarce. We conducted a case-control study in a county located at Southeastern China, including 46 cases and 230 individually matched controls. A semi-quantitative method based on experts' assessment was used for evaluating hand-spinning chrysotile exposure. Conditional logistic regression models were used to assess the association of asbestos exposure with risk of mesothelioma. We found that hand-spinning chrysotile exposure was associated with significantly elevated risk of mesothelioma, reaching OR =10 (95% CIs: 1.4-65) for possible exposure and 64 (12-328) for definite exposure. Our data suggested a dose-response relationship of chrysotile exposure duration with risk of mesothelioma, reaching 28 (6-134) for <6 years, 51 (11-247) for 7-17 years and 56 (9-351) for ≥18 years. A dose-response relationship of cumulative exposure index (CEI) with risk of mesothelioma was found, reaching 28 (6-137) for CEI at 0-0.5 fibers per milliliter years (f/mL-year), 36 (7-184) for CEI at 0.5-28.6 f/mL-years and 79 (14-451) for CEI > 28.6 f/mL-years. We found a dose-response relationship of chrysotile exposure duration and CEI with risk of mesothelioma in Southeastern China, adding valuable information on health hazards of chrysotile exposure in China where chrysotile is still used nationwide.

Novel Two-Dimensional Silicon Dioxide with in-Plane Negative Poisson's Ratio.

Silicon dioxide or silica, normally existing in various bulk crystalline and amorphous forms, was recently found to possess a two-dimensional structure. In this work, we use ab initio calculation and evolutionary algorithm to unveil three new two-dimensional (2D) silica structures whose thermal, dynamical, and mechanical stabilities are compared with many typical bulk silica. In particular, we find that all three of these 2D silica structures have large in-plane negative Poisson's ratios with the largest one being double of penta graphene and three times of borophenes. The negative Poisson's ratio originates from the interplay of lattice symmetry and Si-O tetrahedron symmetry. Slab silica is also an insulating 2D material with the highest electronic band gap (>7 eV) among reported 2D structures. These exotic 2D silica with in-plane negative Poisson's ratios and widest band gaps are expected to have great potential applications in nanomechanics and nanoelectronics.

Two-Dimensional Heterostructure as a Platform for Surface-Enhanced Raman Scattering.

Raman enhancement on a flat nonmetallic surface has attracted increasing attention, ever since the discovery of graphene enhanced Raman scattering. Recently, diverse two-dimensional layered materials have been applied as a flat surface for the Raman enhancement, attributed to different mechanisms. Looking beyond these isolated materials, atomic layers can be reassembled to design a heterostructure stacked layer by layer with an arbitrary chosen sequence, which allows the flow of charge carriers between neighboring layers and offers novel functionalities. Here, we demonstrate the heterostructure as a novel Raman enhancement platform. The WSe2 (W) monolayer and graphene (G) were stacked together to form a heterostructure with an area of 10 mm × 10 mm. Heterostructures with different stacked structuress are used as platforms for the enhanced Raman scattering, including G/W, W/G, G/W/G/W, and W/G/G/W. On the surface of the heterostructure, the intensity of the Raman scattering is much stronger compared with isolated layers, using the copper phthalocyanine (CuPc) molecule as a probe. It is found that the Raman enhancement effect on heterostructures depends on stacked methods. Phonon modes of CuPc have the strongest enhancement on G/W. W/G and W/G/G/W have a stronger enhancement than that on the isolated WSe2 monolayer, while lower than the graphene monolayer. The G/W/G/W/substrate demonstrated a comparable Raman enhancement effect than the G/W/substrate. These differences are due to the different interlayer couplings in heterostructures related to electron transition probability rates, which are further proved by first-principle calculations and probe-pump measurements.

A Tumor-Specific Neo-Antigen Caused by a Frameshift Mutation in BAP1 Is a Potential Personalized Biomarker in Malignant Peritoneal Mesothelioma.

Malignant peritoneal mesothelioma (MPM) is an aggressive rare malignancy associated with asbestos exposure. A better understanding of the molecular pathogenesis of MPM will help develop a targeted therapy strategy. Oncogene targeted depth sequencing was performed on a tumor sample and paired peripheral blood DNA from a patient with malignant mesothelioma of the peritoneum. Four somatic base-substitutions in NOTCH2, NSD1, PDE4DIP, and ATP10B and 1 insert frameshift mutation in BAP1 were validated by the Sanger method at the transcriptional level. A 13-amino acids neo-peptide of the truncated Bap1 protein, which was produced as a result of this novel frameshift mutation, was predicted to be presented by this patient's HLA-B protein. The polyclonal antibody of the synthesized 13-mer neo-peptide was produced in rabbits. Western blotting results showed a good antibody-neoantigen specificity, and Immunohistochemistry (IHC) staining with the antibody of the neo-peptide clearly differentiated neoplastic cells from normal cells. A search of the Catalogue of Somatic Mutations in Cancer (COSMIC) database also revealed that 53.2% of mutations in BAP1 were frameshift indels with neo-peptide formation. An identified tumor-specific neo-antigen could be the potential molecular biomarker for personalized diagnosis to precisely subtype rare malignancies such as MPM.

Asbestos textile production linked to malignant peritoneal and pleural mesothelioma in women: Analysis of 28 cases in Southeast China.

BACKGROUND: Chrysotile had been used in asbestos textile workshops in Southeast China but a clear relation to mesothelioma is lacking. METHODS: All patients diagnosed with mesothelioma from 2003 to 2010 at Yuyao People's Hospital were re-evaluated by multiple expert pathologists with immunohistochemistry and asbestos exposure data were collected. RESULTS: Of 43 patients with a mesothelioma diagnosis, 19 peritoneal and nine pleural cases were finally diagnosed as mesothelioma. All were females, and the mean age of the patients with peritoneal or pleural mesothelioma was 52.4 and 58.2 years, respectively. All these cases had a history of domestic or occupational exposure to chrysotile. Two-thirds of the patients were from two adjoining towns with multiple small asbestos textile workshops. Contamination of tremolite was estimated to be less than 0.3%. CONCLUSIONS: This is a report of mesothelioma in women exposed to chrysotile asbestos at home and at work, with an over-representation of peritoneal mesothelioma.

[Comparing the results of pathologic diagnosis of mesothelioma between Chinese and Japanese experts].

OBJECTIVE: To compare the results of pathological diagnosis of 41 patients with malignant mesothelioma between Chinese and Japanese experts, and to provide a basis for the standard for diagnosis of mesothelioma. METHODS: The medical information and tissue samples of 41 patients with malignant mesothelioma were collected in a hospital in Zhejiang Province from 2003 to 2010. The expression levels of calretinin, Wilms' tumor suppressor gene (WT1), podoplanin (D2-40), cytokeratins (CK5/6, AE1/AE3, and CAM5.2), epithelial membrane antigen, carcinoembryonic antigen, BerEP4, MOC31, thyroid transcription factor-1, estrogen receptor, and progesterone receptor in tumor tissues were measured using immunohistochemical staining by Japanese experts, and the pathological classification and diagnosis were made. The results of diagnosis, pathological classification, immunohistochemical marker selection, and slide review were compared between Chinese and Japanese experts. RESULTS: Twenty-nine (70.7%) cases were diagnosed as mesothelioma by Japanese experts, among whom 12 (41.4%) cases were pleura mesothelioma, and 17 (58.6%) cases were peritoneal mesothelioma. Ten (24.4%) cases were confirmed without mesothelioma, and 2 (4.9%) cases were not confirmed due to insufficient information. Thirty-two (78.0%) cases were diagnosed as mesothelioma by Chinese experts, among whom 8 (25.0%) cases were pleura mesothelioma, and 24 (75.0%) cases were peritoneal mesothelioma. One (2.4%) case was confirmed without mesothelioma, and 8 (19.5%) cases were not confirmed. There were significant differences in the results of diagnosis between Chinese and Japanese experts. However, their pathological classifications of mesothelioma were similar. Significant differences in immunohistochemical marker selection and slide review were also found between Chinese and Japanese experts. CONCLUSION: The diagnostic skills of those pathological experts in this hospital remain to be further improved for mesothelioma diagnosis. A panel of immunohistochemical markers including at least 2 mesothelioma-positive and 2 mesothelioma-negative markers are recommended for the diagnosis of malignant mesothelioma.

[The effects of equol on enzymes related to testosterone synthesis and vimentin in the testis of perinatal mice by organ culture in vitro].

OBJECTIVE: To investigate the effects of Equol on genes and protein expression of testosterone synthesis related enzymes and Vimentin in testis of perinatal mice in vitro. METHODS: Testes were isolated and cultured in infiltrating type rotating device for 72 h. The testes were randomly divided into five groups and treated with Equol (DMSO control, 0.01, 0.10, 1.00, 10.00 µmol/L Equol). Morphological changes were observed by HE staining under optical microscope. Expressions of 3ß-hydroxysteroid dehydrogenase (3ß-HSD),P450 side-chain cleavage enzyme (P450scc), Vimentin were detected by real-time PCR and immunohistochemistry. RESULTS: No apparent morphological change in testes was observed compared to control group. The mRNA expression of 3ß HSD, P450Scc, Vimentin show no statistical significance(P> 0. 05) in all Equol group, while the protein expressions of 3ß-HSD, Vimentin, P450scc increased in 0. 10 µmol/L and decreased in 10.00 µmol/L Equol group. CONCLUSION: Equol exposure can affect 3ß-HSD, P450Scc, Vimentin expression in testes in vitro, means Equol may have potential adverse effects on testosterone production and spermatogenesis.

Two-Dimensional-Like Phonons in Three-Dimensional-Structured Rhombohedral GeSe-Based Compounds with Excellent Thermoelectric Performance.

The coupling of charge and phonon transport in solids is a long-standing issue for thermoelectric performance enhancement. Herein, two new narrow-gap semiconductors with the same chemical formula of GeSe0.65Te0.35 (GST) are rationally designed and synthesized: one with a layered hexagonal structure (H-GST) and the other with a non-layered rhombohedral structure (R-GST). Thanks to the three-dimensional (3D) network structure, R-GST possesses a significantly larger weighted mobility than H-GST. Surprisingly, 3D-structured R-GST displays an extremely low lattice thermal conductivity of ∼0.5 W m-1 K-1 at 523 K, which is comparable to that of layered H-GST. The two-dimensional (2D)-like phonon transport in R-GST stems from the unique off-centering Ge atoms that induce ferroelectric instability, yielding soft polar phonons, as demonstrated by the Boson peak detected by the low-temperature specific heat and calculated phonon spectra. Furthermore, 1 mol % doping of Sb is utilized to successfully suppress the undesired phase transition of R-GST toward H-GST at elevated temperatures. Consequently, a peak ZT of 1.1 at 623 K is attained in the rhombohedral Ge0.99Sb0.01Se0.65Te0.35 sample, which is 1 order of magnitude larger than that of GeSe. This work demonstrates the feasibility of exploring high-performance thermoelectric materials with decoupled charge and phonon transport in off-centering compounds.

Fast Na+ Kinetics and Suppressed Voltage Hysteresis Enabled by a High-Entropy Strategy for Sodium Oxide Cathodes.

O3-type layered transition metal cathodes are promising energy storage materials due to their sufficient sodium reservoir. However, sluggish sodium ions kinetics and large voltage hysteresis, which are generally associated with Na+ diffusion properties and electrochemical phase transition reversibility, drastically minimize energy density, reduce energy efficiency, and hinder further commercialization of sodium-ion batteries (SIBs). Here, this work proposes a high-entropy tailoring strategy through manipulating the electronic local environment within transition metal slabs to circumvent these issues. Experimental analysis combined with theoretical calculations verify that high-entropy metal ion mixing contributes to the improved reversibility of redox reaction and O3-P3-O3 phase transition behaviors as well as the enhanced Na+ diffusivity. Consequently, the designed O3-Na0.9Ni0.2Fe0.2Co0.2Mn0.2Ti0.15Cu0.05O2 material with high-entropy characteristic could display a negligible voltage hysteresis (<0.09 V), impressive rate capability (98.6 mAh g-1 at 10 C) and long-term cycling stability (79.4% capacity retention over 2000 cycles at 5 C). This work provides insightful guidance in mitigating the voltage hysteresis and facilitating Na+ diffusion of layered oxide cathode materials to realize high-rate and high-energy SIBs.

[Effects of bisphenol A on testis testosterone synthesis in mouse cultured in vitro].

OBJECTIVE: To investigate the effects of BPA on testosterone synthesis and the related genes expression in the fetal testis of male mouse by organ culture in vitro. METHODS: The testis tissues cultured in vitro were randomly divided into five groups, DMSO control group and 4 different concentration of BPA groups (10(-7), 10(-6), 10(-5) and 10(-4) mol/L respectively). The culture medium and gas were changed every 24 h. The histomorphological examination of the testis was conducted under optical microscope, the testosterone levels in the cultured medium were measured by radioimmunoassay, the expressions of related proteins were measured by immunohistochemistry, and the expression of 3betaHSD, P450scc, P450c17 and Vimentin were determined by real-time PCR. RESULTS: Compared to the control group, the number of sertoli cells were decreased and flocculent changes appear in some Leydig ceils in 10(-) mol/L dose group. Testosterone secretion was gradually reduced as time goes on. The testosterone synthesis of 10(-5) mol/L dose group was increased in 48h (P < 0.05), and the rest groups were decreased, especially the 10(-4) mol/L dose group (P < 0.1). The expression of genes coding for proteins involved in testosterone biosynthesis, 3betaHSD, P450scc, P450c17 and Vimentin were reduced. CONCLUSION: Bisphenol A can affect testosterone synthesis of mouse cultured in vitro through suppression of 3betaHSD ,P450scc, P450c17 and Vimentin.