环境科学与工程专业物理化学课程教与学的探讨

物理化学的学习前提是具有良好的高等数学知识基础及较强的逻辑推理能力,因此物理化学普遍被视为最难学的化学学科。本文紧扣金课标准,以环境科学与工程类专业学生为授课对象,基于近年来作者在物理化学教学内容和方法方面的探索,分析物理化学中的教与学中存在的问题及解决方法。     

氧化石墨烯/超细银粒子复合物的制备及其光电性能

超细银粉在太阳能电池正面电极领域有广阔的应用前景,其粒径分布、分散性、表面态与其性能息息相关。 本文通过在液相还原法合成超细银粉的后期引入氧化石墨烯(GO),利用溶液状态下二者相对活性的表面的相互作用获得了性能优良的银粉。 通过X射线衍射(XRD)、拉曼光谱(Raman)和扫描电子显微镜(SEM)等手段对所得复合超细银粉进行结构及形貌表征,结果显示该法获得的银粉分散性较好、尺寸分布较窄。 进而,利用紫外-可见光谱探讨了GO与银粒子之间的相互作用。 而且研究发现:固定硝酸银溶液的浓度,随着GO含量的增加,银粉的导电性能先升高后降低,当GO的质量分数为2.5%时,导电性能更好。 这为超细银粉在实际中的应用提供重要数据和有益参考。     

Thermo- and pH-responsive fluorescence behaviors of sulfur-functionalized detonation nanodiamond-poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide)

Detonation nanodiamonds (DNDs) are emerging as bioimaging platforms due to their biocompability, small primary particle size, reactive surface, and stable fluorescence after modification. In this paper, a heteroatom engineering method is provided to fabricate the fluorescent DNDs through pyrolysis of dibenzyl disulfide. The quantum yield of these sulfur (S)-functionalized DNDs (SDNDs) increases with sulfur percentage. The solubility and stability of SDNDs in aqueous solution are also significantly increased due to the formation of hydrophilic sulfur groups on DND. Furthermore, these SDNDs are used to conjugate the stimuli-responsive poly(N-isopropylacrylamide) (PNIPAM) through the ‘graft from’ method. The conjugation demonstrated both pH- and thermo-responsive fluorescence behaviors, which shows promise to be used in ratiometric fluorescence sensing for the detection of intracellular pH and temperature values.     

Surface modification of hollow microsphere Li1.2Ni1/3Co1/3Mn1/3O2 cathode by coating with CoAl2O4

Journal of Solid State Electrochemistry - Li1.2Ni1/3Co1/3Mn1/3O2 was synthesized as a cathode material for lithium-ion batteries and coated with various amounts of CoAl2O4 (0–5&nbsp;wt%)...     

Simulation of pulse responses of lithium salt‐doped poly ethyleneoxide

Ionic migration in organic electrolytes resembles that in neural system involving signal transportation. Here, ionic dynamic simulations are applied to explore pulse responses of lithium‐doped polyethyleneoxide complexes. Two main interactions were considered: diffusion of ions and directional movement guided by an applied electric field. Frequency responses are simulated using arbitrary wave shape. It is found that redistribution of ions results in accumulation of charge and establishes a reverse inbuilt electric field controlling the discharging process and the frequency response. The charging current's wave shape is controlled mainly by contribution from the diffusion process, which strengthens the charging current in the first millisecond before weakening it. For stimulation with higher energy density (higher frequency), activation of ion channels should be considered and an active ion number is introduced to describe the process. The weights of calculated discharging current agree well with the experimental results. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 831–837     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/rice husk-based maco-/mesoporous carbon bone nanocomposite as superior high-rate anode for lithium ion battery

Rice husks (RHs), a kind of biowastes, are firstly hydrothermally pretreated by HCl aqueous solution to achieve promising macropores, facilitating subsequently impregnating ferric nitrate and urea aqueous solution, the precursor of Fe₃O₄ nanoparticles. A Fe₃O₄/rice husk-based maco-/mesoporous carbon bone nanocomposite is finally prepared by the high-temperature hydrothermal treatment of the precursor-impregnated pretreated RHs at 600 °C followed by NaOH aqueous solution treatment for dissolving silica and producing mesopores. The macro-/mesopores are able to provide rapid lithium ion-transferring channels and accommodate the volumetric changes of Fe₃O₄ nanoparticles during cycling as well. Besides, the macro-/mesoporous carbon bone can offer rapid electron-transferring channels through directly fluxing electrons between Fe₃O₄ nanoparticles and carbon bone. As a result, this nanocomposite delivers a high initial reversible capacity of 918 mAh g^?1 at 0.2 A g^?1 and a reversible capacity of 681 mAh g^?1 remained after 200 cycles at 1.0 A g^?1. The reversible capacities at high current densities of 5.0 and 10.0 A g^?1 still remain at high values of 463 and 221 mAh g^?1, respectively.     

Modeling negative cooperativity in streptavidin adsorption onto biotinylated microtubules

The nanoscale architecture of binding sites can result in complex binding kinetics. Here, the adsorption of streptavidin and neutravidin to biotinylated microtubules is found to exhibit negative cooperativity due to electrostatic interactions and steric hindrance. This behavior is modeled by a newly developed kinetic analogue of the Fowler-Guggenheim adsorption model. The complex adsorption kinetics of streptavidin to biotinylated structures needs to be considered when these intermolecular bonds are employed in self-assembly and nanobiotechnology.     

Template-free polyoxometalate-assisted synthesis for ZnO hollow spheres

ZnO hollow spheres with diameters ranging from 400 to 600 nm and the thickness of shell approximate 80 nm were synthesized by a simple polyoxometalate-assisted solvothermal route without using any templates. The effect of polyoxometalate concentration, reaction time and temperature on the formation of the hollow spheres was investigated. The results indicated that the hollow spheres were composed of porous shells with nanoparticles and polyoxometalate play a key role in controlling morphology of ZnO. A possible growth mechanism based on polyoxometalate-assisted assembly and slow Ostwald ripening dissolution in ethanol solution is tentatively proposed. In addition, the room temperature photoluminescence spectrum showed that the ZnO hollow spheres exhibit exciting emission features with wide band covering nearly all the visible region.     

Jingle-bell-shaped ferrite hollow sphere with a noble metal core: Simple synthesis and their magnetic and antibacterial properties

In this paper, a simple strategy is developed for rational fabrication of a class of jingle-bell-shaped hollow structured nanomaterials marked as Ag@MFe₂O₄ (M=Ni, Co, Mg, Zn), consisting of ferrite hollow shells and metal nanoparticle cores, using highly uniform colloidal Ag@C microspheres as template. The final composites were obtained by direct adsorption of metal cations Fe³⁺ and M²⁺ on the surface of the Ag@C spheres followed by calcination process to remove the middle carbon shell and transform the metal ions into pure phase ferrites. The as-prepared composites were characterized by X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray analysis (EDX), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis spectroscopy and SQUID magnetometer. The results showed that the composites possess the magnetic property of the ferrite shell and the optical together with antibacterial property of the Ag core.