Nonsaturating Linear Magnetoresistance Manifesting Two-Dimensional Transport in Wet-Chemical Patternable Bi2O2Te Thin Films.

Two-dimensional (2D) materials with exotic transport behaviors have attracted extensive interest in microelectronics and condensed matter physics, while scaled-up 2D thin films compatible with the efficient wet-chemical etching process represent realistic advancement toward new-generation integrated functional devices. Here, thickness-controllable growth and chemical patterning of high-quality Bi2O2Te continuous films are demonstrated. Noticeably, except for an ultrahigh mobility (∼45074 cm2 V-1 s-1 at 2 K) and obvious Shubnikov-de Hass quantum oscillations, a 2D transport channel and large linear magnetoresistance are revealed in the patterned Bi2O2Te films. Investigation implies that the linear magnetoresistance correlates with the inhomogeneity described by P. B. Littlewood's theory and EMT-RRN theory developed recently. These results not only reveal the nonsaturating linear magnetoresistance in high-quality Bi2O2Te but shed light on understanding the corresponding physical origin of linear magnetoresistance in 2D high-mobility semiconductors and providing a pathway for the potential application in multifunctional electronic devices.

Two-Dimensional Superconductivity in Air-Stable Single-Crystal Few-Layer Bi3O2S3.

The progress of unconventional superconductors at the two-dimensional (2D) limit has inspired much interest. Recently, a new superconducting system was discovered in the semimetallic ternary Bi-O-S family. However, pure-phase crystals are difficult to synthesize because of the complicated stacking sequence of multiple charged layers and similar formation kinetics among ternary polytypes, leaving several fundamental issues regarding the structure-superconductivity correlation unresolved. Herein, 2D single-crystal ultrathin Bi3O2S3 nanosheets are prepared by using low-pressure chemical vapor deposition, and their atomic arrangement is clarified. Magnetotransport measurements indicate a superconducting transition at ∼6.1 K that is thickness-independent. The transport results demonstrate 2D superconducting characteristics, such as the Berezinskii-Kosterlitz-Thouless transition, and strong anisotropy with magnetic field orientations following the 2D Tinkham formula. The difference from superconductivity of powder is demonstrated from the perspective of their corresponding microstructures. These results corroborate the superconducting behavior of Bi3O2S3, providing fresh insights into the search for other bismuth oxychalcogenides and derivative BiS2-based analogues at the 2D limit.

Synthesis and characterization of low surface energy thermoplastic polyurethane elastomers based on polydimethylsiloxane.

Organosilicon modified polyurethane elastomers (Si-MTPUs) were synthesized in order to improve the anti-graffiti property of thermoplastic polyurethane elastomers (TPUs). Si-MTPUs were prepared from polydimethylsiloxane (PDMS) and polytetramethylene glycol (PTMG) as mixed soft segment, 1,4-butanediol (BDO) and imidazole salt ionic liquid N-glyceryl-N-methyl imidazolium chloride ([MIMl,g]Cl) used as chain extender, and 4,4'-dicyclohexylmethane diisocyanate (HMDI). The structure, thermal stability, mechanical properties and physical crosslinking density of Si-MTPUs were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TGA), mechanical test and low field nuclear magnetic resonance. Surface energy and water absorption were characterized by static contact angle test and water resistance test, and anti-graffiti and self-cleaning properties were characterized with water, milk, ink, lipstick, oily markers and spray paint. It was found that the mechanical properties of Si-MTPU-10 with the content of PDMS 10 wt% were optimized, with a maximum tensile strength of 32.3 MPa and elongation at break of 656%. Surface energy reached the minimum value of 23.1 mN m-1 with the best anti-graffiti performance, which no longer decreased with the increase of PDMS contents. This work provides novel idea and strategy for the preparation of low surface energy TPUs.

Tunable Mechanics and Micromechanism in Close-Knit Silicide-in-SiO2 Core-Shell Nanowires.

Bending/tension mechanics is one of the core issues for nanowires in flexible free-standing transport and sensor applications, but it remains a challenge to tailor the mechanical performance beyond the inherent properties. Herein, based on structure engineering, silicon-based Mn5Si3@SiO2 nanocables are proposed and demonstrated as versatile nanosystems. Except for outstanding toughness, large ultimate strain, and great strength, they display diverse mechanical behaviors such as simplex elasticity, plasticity, and viscoelasticity under different external conditions. The tunable performances originate from synergetic effects between the core and shell components, like the atomic bonding transitional interface and space confinement, which induce optimizing internal stress distribution and the dislocation evolution mechanism in the core. The related mechanical performance is revealed carefully. The bending and tension dynamic picture, quantitative force curve, stress-strain dependence, and the corresponding lattice evolution are acquired by in/ex situ characterizations and measurements. These results contribute to nanowire mechanical design and also expand to strain-regulated three-dimensional multifunctional nanosystems.

Coexistence of Anisotropic Large Magnetoresistance and Ferroelectricity in Two-Dimensional Narrow-Bandgap Bi2O2Te.

Characteristics like air-stability and high carrier mobility make non-van-der-Waals layered Bi2O2Se a good prospect for planar integrated nanosystems. However, experimental investigation about its analogue Bi2O2Te is rather rare due to difficulty in synthesis. Herein, a low-pressure CVD process is proposed that is adjusted to the rigorous growth condition required, with large-scale Bi2O2Te ultrathin film obtained. Magneto-transport behavior reveals a very large anisotropic nonsaturating low-temperature magnetoresistance (∼1133% under 9 T magnetic field). Despite the contradiction between high conductivity and ferroelectricity in principle (mobile electrons screen electrostatic forces between ions), the high-conductive Bi2O2Te film here is revealed experimentally as another intrinsic ferroelectric with the polarization switchable by external electric field (predicted in Nano Lett. 2017, 17, 6309). These results prove that Bi2O2Te possesses a very narrow bandgap (∼0.15 eV), high conductivity, large magnetoresistance, and room-temperature ferroelectricity, displaying great potential as a high-performance nanoelectronic two-dimensional semiconductor and, in advanced functional devices, working in the mid-infrared region.

Horizontally Self-Standing Growth of Bi2 O2 Se Achieving Optimal Optoelectric Properties.

Air-stable 2D Bi2 O2 Se material with high carrier mobility appears as a promising semiconductor platform for future micro/nanoelectronics and optoelectronics. Like most 2D materials, Bi2 O2 Se 2D nanostructures normally form on atomically flat mica substrates, in which undesirable defects and structural damage from the subsequent transfer process will largely degrade their photoelectronic performance. Here, a new synthesis route involving successive kinetic and thermodynamic processes is proposed to achieve horizontally self-standing Bi2 O2 Se nanostructures on SiO2 /Si substrates. Fewer defects and avoidance of transfer procedure involving corrosive solvents ensure the integrity of the intrinsic lattice and band structures in Bi2 O2 Se nanostructures. In contrast to flat structures grown on mica, it displays reduced dark current and improved photoresponse performance (on-off ratio, photoresponsivity, response time, and detectivity). These results indicate a new potential in high-quality 2D electronic nanostructures with optimal optoelectronic functionality.

A study on the effect of four thermoplastic elastomers on the properties of double-base propellants.

To improve the low-temperature mechanical properties of double-base propellants, glycidyl azide polymer-energetic thermoplastic elastomer (GAP-ETPE), polyether block copolyimide-thermoplastic elastomer (PEBA-TPE), 1,2-polybutadiene thermoplastic elastomer (PB-TPE), and ethylene oxide-tetrahydrofuran copolyester-thermoplastic elastomer (PET-TPE) were used to modify them. The effects of these four thermoplastic elastomers (TPEs) on the energy properties of double-base propellants were studied via theoretical calculations. The mechanical properties of double-base propellants at high, low, and room temperature were compared, and their thermal properties were analyzed. It was found that GAP-ETPE had a significant effect on improving the low-temperature mechanical properties of double-base propellants, with the maximum tensile strength and maximum elongation at a low temperature for the double-base propellant reaching 43.30 MPa and 6.24%, respectively.

Novel waterborne polyurethanes containing long-chain alkanes: their synthesis and application to water repellency.

In the fabric finishing field, the water repellents have received increasing interest in recent years and the development of a fluorine-free water repellent has become an attractive prospect. In this study, glyceryl monostearate-modified waterborne polyurethanes (GWPUs) with a branched structure act as water repellents, and were prepared from toluene diisocyanate, trimethylolpropane, hydroxypropyl polydimethylsiloxane, N-methyldiethanolamine, and glyceryl monostearate (GMS). The water repellency and other properties of GWPUs with different GMS content, such as water resistance, hydrophobicity, and air permeability, were studied. The results show that the GMS content for optimum water repellency was 20 wt%, which achieved the highest score (100 points) in a water repellency evaluation. As for the water repellent ability with a GMS content of 20 wt%, the water absorption of a piece of film was reduced to 7.80%, while the water contact angle of terylene coated by the water repellent rose to 148.0°.

AMPD1 functional variants associated with autism in Han Chinese population.

Autism is a childhood neurodevelopmental disorder with high heterogeneity. Following our genome-wide associated loci with autism, we performed sequencing analysis of the coding regions, UTR and flanking splice junctions of AMPD1 in 830 Chinese autism individuals as well as 514 unrelated normal controls. Fourteen novel variants in the coding sequence were identified, including 11 missense variants and 3 synonymous mutations. Among these missense variants, 10 variants were absent in 514 control subjects, and conservative and functional prediction was carried out. Mitochondria activity and lactate dehydrogenase assay were performed in 5 patients' lymphoblast cell lines; p.P572S and p.S626C showed decreased mitochondrial complex I activity, and p.S626C increased lactate dehydrogenase release in medium. Conclusively, our data suggested that mutational variants in AMPD1 contribute to autism risk in Han Chinese population, uncovering the contribution of mutant protein to disease development that operates via mitochondria dysfunction and cell necrosis.

Two new phenylpropanoid derivatives and other constituents from Illicium simonsii active against oral microbial organisms.

Bioassay-guided fractionation of the ethanol extract of the leaves and stems of Illicium simonsii led to the isolation of two new compounds, simonin A (1) and 1-hydroxyl-2- O- ß- D-6'-acetyl-glucopyranosyl-4-allylbenzene (2), along with eight known compounds. Their structures were elucidated by spectroscopic analysis. The isolates were tested for anti-oral microbial activity using a microdilution method. Compounds 1 and 3- 6 showed significant activities against oral microbial organisms (Actinomyces viscosus, Streptococcus mutans, Streptococcus sanguis, and Actinomyces naeslundii), with minimum inhibitory concentration (MIC) values ranging from 1.95 to 31.25 µg/mL in vitro.