ChemPhysMater最新文献

Gas sensors play a vital role in monitoring environmental pollution for human health, safety, and the detection of various gasses in the environment. Nanostructured metal oxide thin films have been widely used in sensor applications owing to their unique properties. In this study, pure and gold (Au) doped nanostructured tungsten trioxide (WO₃) films were deposited on glass substrates by electron beam evaporation at room temperature. The microstructure of the WO₃ films changed from nanoflakes to nanorods upon variation of the wt% of Au. The sensing properties of WO₃ based nanostructure films were measured using a computer-controlled system. The gas sensing results showed that the Au-doped WO₃ films exhibited a higher sensitivity than the undoped films. The 15 wt% Au-doped WO₃ nanostructure films showed high sensitivity towards ethanol and the response (sensitivity) value was 89. The response and recovery times for 15 wt% Au-doped WO₃ were 8 and 10 s, respectively.

Lyotropic liquid crystals (LLCs) produced by the self-assembly of surfactant in water represent an important class of highly ordered soft materials that have a wide range of applications. This study investigates the LLCs formed by a zwitterionic surfactant (tetradecyldimethylaminoxide, C₁₄DMAO) in water. The organization of C₁₄DMAO within the LLCs was determined based on a detailed analysis of small-angle X-ray scattering measurements and polarized microscopy observations of a typical sample. Additional to the singe-phase region, which has a hexagonal organization, several two-phase regions were observed, exhibiting the coexistence of hexagonal/cubic, cubic/lamellar, and hexagonal/lamellar phases. The phase behavior showed an obvious dependence on temperature, with more pronounced two-phase regions at lower temperatures. Using the LLCs as a matrix, Au nanospheres, nanoellipsoids, and nanorods were prepared without requiring additional reducing reagents. These three- and one-dimensional Au nanomaterials could be converted to two-dimensional plates via the introduction of a small amount of cationic surfactant to the LLCs, such as cetyltrimethylammonium bromide (CTAB) and 1-hexadecyl-3-methylimidazolium bromide ([C₁₆MIm]B), which showed pronounced surface-enhanced Raman scattering activity towards solid rhodamine. The LLCs loaded with CTAB (or [C₁₆MIm]B) and HAuCl₄ exhibited slightly different structures and mechanical strength from the original LLCs, thereby forming a new class of highly crowded colloidal materials.

The effects of light elements on the elastic properties of disordered binary hcp-Fe alloys were investigated at high pressures using plane-wave density functional theory combined with the Monte Carlo special quasi-random structure method. We found that the increase in the O content in hcp-Fe had a more pronounced effect on the sound velocity than Si, S, and C. The longitudinal wave velocity was decreased by ∼ 6% with 2% O content, which was a much greater decrease than the values of 0.6% and 2% induced by the same content of Si and S, respectively, under high pressures. Compared with the other three light elements, the longitudinal wave velocity of the Fe-C alloy exhibited the most gradual decreasing with increasing C content. In addition, the effects of different O and S contents on the anisotropy of hcp-Fe alloys strongly depended on the variation in pressure, whereas the pressure only slightly affected the anisotropy of Fe-Si alloy systems.

Polyacrylonitrile (PAN) with CN bonds can be converted to nitrogen-doped carbon during carbonization, which enhances electronic conductivity by compensating for the deficiency of the Li₂ZnTi₃O₈ (LZTO) anode. In this study, LZTO was modified by carbonizing a homogeneous PAN/LZTO powder mixture at approximately 800 ℃ for 5 h in nitrogen stream to uniformly coat nitrogen-doped carbon around the LZTO particles and to yield nitrogen-doped LZTO. PAN-60 exhibited a capacity retention of 74.8% as the current density increased from 0.1 to 1.6 A g⁻¹, and had charge/discharge capacities of 250.1/250.8 mAh g⁻¹ even after 1100 cycles at 0.5 A g⁻¹. Structural and compositional analysis along with electrochemical tests showed that the uniform nitrogen-doped carbon coating and the nitrogen-doped LZTO favor electron transfer, while the defects induced by nitrogen-doping in LZTO promote Li-ion migration. The enhanced electronic and ionic conductivities are favorable to alleviate the polarization during cycling, and thus are responsible for the optimized performance.

The discovery of graphene has led to the devotion of intensive efforts, theoretical and experimental, to produce two-dimensional (2D) materials that can be used for developing functional materials and devices. This work provides a brief review of the recent developments in the lattice models of 2D Dirac materials and their relevant real material counterparts that are crucial for understanding the origins of 2D Dirac cones in electronic band structures as well as their material design and device applications. We focus on the roles of lattice symmetry, atomic orbital hybridization, and spin–orbit coupling in the presence of a Dirac cone. A number of lattice models, such as honeycomb, kagome, ruby, star, Cairo, and line-centered honeycomb, with different symmetries are reviewed based on the tight-binding approach. Inorganic and organic 2D materials, theoretically proposed or experimentally synthesized to satisfy these 2D Dirac lattice models, are summarized.