高分子材料与工程专业新生研讨课的教学改革与实践

新生专业研讨课作为我校高分子材料与工程专业新生入学教育的重要内容,它的建设和发展对于大一新生对本专业的了解和学习方法的掌握是非常关键的。本文主要对高分子材料与工程专业的新生专业研讨课的教学内容和教学方法进行探讨,新生专业研讨课的教学内容主要包括详细的专业介绍、专业讨论课程和实践操作课程、专业思想教育,教学方法除了采取了传统的课堂讲授外,还有课堂讨论、课堂探究及实验、专家讲座。     

2017年美国国家化学周活动展示及启示

简要介绍2017年美国国家化学周活动，并得出对我国中学化学教学的启示：（1）营造宽松氛围，实现寓教于乐；（2）凸显证据推理，强化辨识能力；（3）争创绿色教育，长鸣安全警钟；（4）鼓励质疑问难，培养探索精神；（5）拓宽化学阅读，开阔学科视野；（6）开发七彩实验，畅享化学之美。     

Inter-comparison and validation of computational fluid dynamics codes in two-stage meandering channel flows

This paper presents a study in the inter-comparison and validation of three-dimensional computational fluid dynamics codes which are currently used in river engineering. Finite volume codes PHOENICS, FLUENT and SSIIM; and finite element code TELEMAC3D are considered in this study. The work has been carried out by competent hydraulic modellers who are users of the codes and not involved in their development. This paper is therefore written from the perspective of independent practitioners of the techniques. In all codes, the flow calculations are performed by solving the three-dimensional continuity and Reynolds-averaged Navier–Stokes equations with the k–ε turbulence model. The application of each code was carried out independently and this led to slightly different, but nonetheless valid, models. This is particularly seen in the different boundary conditions which have been applied and which arise in part from differences in the modelling approaches and methodology adopted by the different research groups and in part from the different assumptions and formulations implemented in the different codes. Similar finite volume meshes are used in the simulations with PHOENICS, FLUENT and SSIIM while in TELEMAC3D, a triangular finite element mesh is used. The ASME Journal of Fluids Engineering editorial policy is taken as a minimum framework for the control of numerical accuracy. In all cases, grid convergence is demonstrated and conventional criteria, such as Y⁺, are satisfied. A rigorous inter-comparison of the codes is performed using large-scale experimental data from the UK Flood Channel Facility for a two-stage meandering channel. This example data set shows complex hydraulic behaviour without the additional complications found in natural rivers. Standardised methods are used to compare each model with the available experimental data. Results are shown for the streamwise and transverse velocities, secondary flow, turbulent kinetic energy, bed shear stress and free surface elevation. They demonstrate that the models produce similar results overall, although there are some differences in the predicted flow field and greater differences in turbulent kinetic energy and bed shear stress. This study is seen as an essential first step in the inter-comparison of some of the computational fluid dynamics codes used in the field of river engineering.     

Charge density wave states in phase-engineered monolayer VTe2

Charge density wave (CDW) strongly affects the electronic properties of two-dimensional (2D) materials and can be tuned by phase engineering. Among 2D transitional metal dichalcogenides (TMDs), VTe$_{2}$ was predicted to require small energy for its phase transition and shows unexpected CDW states in its T-phase. However, the CDW state of H-VTe$_{2}$ has been barely reported. Here, we investigate the CDW states in monolayer (ML) H-VTe$_{2}$, induced by phase-engineering from T-phase VTe$_{2}$. The phase transition between T- and H-VTe$_{2}$ is revealed with x-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) measurements. For H-VTe$_{2}$, scanning tunneling microscope (STM) and low-energy electron diffraction (LEED) results show a robust $2\sqrt 3 \times 2\sqrt 3 $ CDW superlattice with a transition temperature above 450 K. Our findings provide a promising way for manipulating the CDWs in 2D materials and show great potential in its application of nanoelectronics.     

Enhanced piezoelectric-induced catalysis of SrTiO3 nanocrystal with well-defined facets under ultrasonic vibration

Facet engineering of nanocomposite has been confirmed to be an efficient strategy to accelerate their catalytic performances, but to improve their piezoelectric catalytic activities by facet engineering has been seldom reported. Herein, we developed a series of SrTiO₃ nanocrystals with exposed {0 0 1} facet, dominant {1 1 0} facet and co-exposed {0 0 1} and {1 1 0} facets, respectively, and firstly revealed its piezoelectric catalytic performance under ultrasonic vibration. Moreover, the relationship between piezoelectric-induced catalytic activity and facet-dependence of SrTiO₃ nanocrystal was disclosed for the first time. The SrTiO₃ nanocrystal with co-exposed {0 0 1} and {1 1 0} facets exhibited effectively enhanced piezoelectric catalytic activity by degrading Rhodamine B (RhB) under ultrasonic vibration, as compared to that of SrTiO₃ nanocrystals with exposed {0 0 1} facet and dominant {1 1 0} facet, respectively. In addition, trapping experiments and active species quantitative experiments confirmed that the co-exposed {0 0 1} and {1 1 0} facets were beneficial to produce O₂⁻ and OH with the generation rates of 8.3 and 132.2 μmol g⁻¹ h⁻¹, respectively. The OH radical played a dominant role in piezoelectric catalytic process. Finally, the piezoelectric catalysis mechanism of SrTiO₃ surface heterojunction was proposed based on a DFT study. This study presents an in-depth understanding of piezoelectric-induced catalytic of perovskite nanocrystals with exposed well-defined facets.     

Metal–DNA Coordination-Driven Self-Assembly: A Conceptual Methodology to Expand the Repertoire of DNA Nanobiotechnology

The past several decades have witnessed a rapid revolution of DNA nanotechnology. DNA nanostructures are mainly synthesized with two approaches, by assembly of purely DNA-based nanostructures through complementary base pairing or grafting DNA onto nanoparticles (NPs). Despite the progress made, developing simple and universal methods for the synthesis of DNA nanoarchitectures with specific morphologies and functionalities is still a challenge. This article introduces the reader to a new biomimetic methodology that leads to the controlled synthesis of DNA nanoarchitectures based on metal–DNA coordination chemistry and, furthermore, demonstrates the broad biomedical applications of these functional materials. In particular, we highlight the coordination-driven 1) surface-functionalization of NPs with DNA molecules and 2) direct self-assembly of metal–DNA nanostructures. Finally, challenges and opportunities of this approach to develop nanobiotechnology are provided.     

Poly(l‐glutamic acid)‐based micellar hydrogel with improved mechanical performance and proteins loading

Soft tissues, such as fat and skin, present high flexibility and are capable of withstanding large deformation in various functions. Hydrogels that can resemble the mechanical performance of soft tissue are unique and widely demanded. In this study, micellar hydrogels based on biocompatible poly(l ‐glutamic acid) (PLGA) were designed with the enhanced capacity to bear large deformation. Amphipathic triblock copolymer poly(ethylene glycol) acrylate‐co‐poly(ε‐caprolactone)‐co‐poly (ethylene glycol) acrylate (APEG‐PCL‐APEG) with two terminal double bonds was synthesized and self‐assembled into micelles. At the same time, graft copolymers, poly(l ‐glutamic acid)‐g‐hydroxyethyl methacrylate (PLGA‐g‐HEMA) with double bonds were synthesized. APEG‐PCL‐APEG micelles and PLGA‐g‐HEMA were mixed to construct micellar hydrogel via radical polymerization. The crystalline structure and hydrophobic aggregation of copolymers (APEG‐PCL‐APEG) were found to associate with PCL molecular weight. Due to the hydrophobic stress dissipation and crystalline structure of the micelles, the softness and toughness of hydrogels were promoted, exhibiting a 25% increase in ultimate strain. Moreover, the micellar hydrogels were able to load proteins with long‐term retention. In addition, under dynamic mechanical stimulation, the release of proteins could be accelerated. Besides, the micellar hydrogels also supported rabbit adipose‐derived stem cells (rASCs) growth, thus exhibiting the potential toward soft tissue engineering. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1115–1125     

Defect Engineering of Two-Dimensional Molybdenum Disulfide

Two-dimensional (2D) molybdenum disulfide (MoS₂) holds great promise in electronic and optoelectronic applications owing to its unique structure and intriguing properties. The intrinsic defects such as sulfur vacancies (SVs) of MoS₂ nanosheets are found to be detrimental to the device efficiency. To mitigate this problem, functionalization of 2D MoS₂ using thiols has emerged as one of the key strategies for engineering defects. Herein, we demonstrate an approach to controllably engineer the SVs of chemically exfoliated MoS₂ nanosheets using a series of substituted thiophenols in solution. The degree of functionalization can be tuned by varying the electron-withdrawing strength of substituents in thiophenols. We find that the intensity of 2LA(M) peak normalized to A_1g peak strongly correlates to the degree of functionalization. Our results provide a spectroscopic indicator to monitor and quantify the defect engineering process. This method of MoS₂ defect functionalization in solution also benefits the further exploration of defect-free MoS₂ for a wide range of applications.