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121.
By using first-principles calculations, we have systematically investigated the structural and electronic properties of an infinite linear monatomic Cu chain with an adsorbed CO molecule. We find that the bridge geometry is energeticabsally favored not only when the Cu–Cu bond below the molecule is unstretched, but also for a wide range of dCu–Cu up to about 4.20 Å, while the substitutional geometry is favored only in the hyperstretched situation dCu–Cu>4.80 Å. Charge density differences point out the electron transfer is from the Cu atoms to the adsorbed CO molecule. The binding mechanism of CO to Cu chain can be described by the Blyholder’s model, in terms of σ-donation of electron density from the nonbonding CO-5σ orbital into empty metal orbitals and π-backdonation from the occupied metal d orbitals to empty CO-2π⁎ orbital. The donation/backdonation process leads to the formation of bonding/antibonding pairs, 5σb/5σa and 2πb⁎/2πa⁎, with the 5σa lying above Ef and the 2πb⁎ below Ef. 相似文献
122.
We explore the electronic structures and magnetic properties in Cu-doped MX2 (=MoS2, MoSe2, MoTe2, and WS2) based on density functional theory. A Cu dopant leads to a net moment of 5.0 or 1.0 μB in MX2, which mainly depend on the size of crystal-field splitting relative to that of the spin splitting. No magnetism is observed in Cu-doped MoTe2. The local distortion around the Cu atom reduces the total magnetic moment in two-Cu-doped MX2. The magnetic coupling between the nearest neighboring Cu atoms is ferromagnetic for all the cases, but they demonstrate various magnetic ground states with the increasing distance between Cu atoms: the Cu-doped MoS2 and WS2 exhibit anti-ferromagnetic and nonmagnetic ground state, respectively. A long-range ferromagnetic or ferrimagnetic coupling is attributed to double-exchange interaction in Cu-doped MoSe2. Half-metallic ferromagnetism with Curie temperature above room temperature in Cu-doped MoSe2 provides a useful guidance to engineer the magnetic properties of MoSe2 in experiments. 相似文献
123.
《Current Applied Physics》2015,15(5):622-631
Lithium (Li) (0–5 wt%) doped V2O5 thin films were spray deposited at 450 °C onto ITO substrates. Structural analysis using X-ray diffraction and Raman spectroscopy revealed orthorhombic phase of the films. In addition to the V2O5 phase, presence of VO2 peaks due to high deposition temperature is also evident from structural and optical characterization. The non-stoichiometric nature of the films due to loss of the terminal O atom was confirmed from Raman spectroscopy. The direct band gap, indirect bandgap, and phonon energies were also calculated from optical studies. Different charge states of vanadium ions present in the film were identified from X-ray photoelectron spectroscopy study. Results from cyclic voltammetry experiments reflected significant differences between the undoped and Li doped V2O5 samples. Transport properties by Hall-effect measured at room temperature indicated significant increase in conductivity, carrier concentration and mobility of V2O5 thin films on doping with Li. A Dye Sensitized Solar Cell (DSSC) was fabricated using mobility enhanced 5 wt% Li doped V2O5 film as photoanode and its efficiency was found to be 2.7%. A simple electrochromic cell is fabricated using undoped V2O5 thin film to demonstrate the colour change. 相似文献
124.
Here we described the design and synthesis of a discrete 3D amphiphilic metallacage 4,in which the tetragonal prismatic frameworks act as the hydrophobic cores and the poly(ethylene glycol)(PEG)chains as the hydrophilic tails.The structure of 4 was characterized by 1H NMR,31P NMR and electrospray ionization time-of-flight mass spectrometry(ESI-TOF-MS).Notably,4 with its Iong PEG tails was subsequently ordered into micelles at a low concentration(1.20×10^-6 mol/L)in water.As the concentration and cultivation time increased,the micelles can further self-assembly into nanofibers and nanoribbons.Considering the dynamic property of the coordination bond,these structures show reversible transformation under external stimuli. 相似文献
125.
Two novel rhodamine-based polystyrene solid-phase fluorescence sensors PS-PA-I and PS-PA-II with different lengths of polyamines were synthesized for Hg(II) determination. The detection mechanism involving the Hg(II) chelation-induced spirocycle open of rhodamine was proposed with the aid of theoretical calculation. The stronger N-Hg bond and the longer polyamine chain in PS-PA-II led to a better selectivity, much higher and more quickly fluorescence response to Hg(II). 相似文献
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128.
Chenxi Zhai Yang Yu Yumei Zhu Jing Zhang Ying Zhong Jingjie Yeo Mingchao Wang 《Molecules (Basel, Switzerland)》2022,27(3)
Foaming effect strongly impacts the physical and mechanical properties of foam glass materials, but an understanding of its mechanism especially at the molecular level is still limited. In this study, the foaming effects of dextrin, a mixture of dextrin and carbon, and different carbon allotropes are investigated with respect to surface morphology as well as physical and mechanical properties, in which 1 wt.% carbon black is identified as an optimal choice for a well-balanced material property. More importantly, the different foaming effects are elucidated by all-atomistic molecular dynamics simulations with molecular-level insights into the structure–property relationships. The results show that smaller pores and more uniform pore structure benefit the mechanical properties of the foam glass samples. The foam glass samples show excellent chemical and thermal stability with 1 wt.% carbon as the foaming agent. Furthermore, the foaming effects of CaSO4 and Na2HPO4 are investigated, which both create more uniform pore structures. This work may inspire more systematic approaches to control foaming effect for customized engineering needs by establishing molecular-level structure–property–process relationships, thereby, leading to efficient production of foam glass materials with desired foaming effects. 相似文献
129.
采用溶胶-凝胶法,以氧化琼脂糖和四甲氧基硅烷为前驱体,通过水解、缩聚反应制得琼脂糖/硅胶复合材料,进一步利用开环、"巯-烯"点击和酰胺化反应对复合材料实现酰胺基团功能化修饰.借助红外光谱(FT-IR)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)对所制备复合材料进行结构、组成和微观形貌表征.以制备的酰胺功能化修饰琼脂糖/硅胶复合材料为吸附剂,探讨其对莱克多巴胺的吸附过程,实验考察了溶剂、吸附时间、莱克多巴胺的初始浓度等对吸附的影响.结果表明:经过修饰反应酰胺基团成功接枝到琼脂糖/硅胶复合材料,该材料颗粒呈球形,粒径在2~3μm之间;复合材料对莱克多巴胺表现出良好的吸附性能,吸附过程50 min达到平衡,适合准二级动力学特征,属化学吸附,吸附等温线符合Freundlich模型;复合材料经过6次吸附解析,再生后对莱克多巴胺的吸附率仅有小幅下降,表明具有较好的循环再生吸附能力. 相似文献
130.
利用玻色化方法可以避免超对称可积系统中反对易费米场带来的计算困难. 本文以N=1超对称mKdVB系统为例, 利用玻色化方法, 将其转化为只有玻色场的耦合系统. 应用标准的WTC方法, 证明了该耦合系统具有Painlevé性质. 运用Painlevé截断方法, 可以得到玻色化后超对称mKdVB系统的非局域对称. 为了求解与非局域对称相关的Lie第一性原理, 引入新的场将玻色化后系统拓展为更大的系统. 通过引入新的场, 该非局域对称局域化为Lie点对称. 因此, 可以利用Lie点对称约化方法研究拓展后的系统, 得到超对称mKdVB系统的孤子与其他孤波相互作用解. 相似文献