超级电容器纳米氧化锰电极材料的合成与表征

以聚乙二醇为分散剂,利用高锰酸钾和醋酸锰溶液之间的化学共沉淀法制备纳米水合氧化锰.借助SEM,TEM,FT-IR,XRD和BET分析手段对样品结构及性能进行表征.研究结果表明,SEM和TEM显示所得粉体为纳米粉体,粒径大约为10～30nm左右,XRD分析表明该粉体为无定型a-MnO₂·nH₂O,FT-IR分析表明获得的粉体为水合物,BET测试比表面积达160.7m²/g.以氧化锰为研究电极,饱和甘汞电极(SCE)为参比电极,铂片为辅助电极的三电极体系中,以1 mol/L的Na₂SO₄溶液为电解液,通过循环伏安法研究其电化学行为.实验结果表明,纳米氧化锰是理想的超级电容器电极材料,在电位窗口为-0.2～0.9V(vs.SCE)范围内,扫描速度为4mV/s,其比电容达到203.4 F/g.     

In situ synthesis of polystyrene/nano-CdSe core/shell microspheres in aqueous solution at room temperature

Polystyrene/nano-CdSe (PS/CdSe) core/shell microspheres were synthesized via in situ soap-free emulsion polymerization using various functional monomers such as 2-(dimethylamino)ethyl methacrylate, 1-vinylimidazole, 2-vinylpridine, and 4-vinylpridine. They were co-polymerized with styrene monomer and provided the location for coordinating with Cd²⁺ ions on the PS particle surfaces. Then, we used an alkaline selenium solution as a selenium source. Reaction of the alkaline selenium solution with the previous emulsion produced nanocrystalline CdSe onto the surface of PS particles at room temperature under atmospheric pressure. The different kinds of functional monomers and the amount of both Cd²⁺ ion and functional monomer were playing important roles to obtain stable and uniform morphologies of CdSe particles. Morphological observations were carried out by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Through the SEM and TEM microphotographs, we could confirm the formation of PS/nano-CdSe composite particles. Ultraviolet–visible absorption measurement indicated the quantum dot effect in the resulted PS/nano-CdSe core/shell microspheres.     

Imaging ice-like structures formed on HOPG at room temperature

In this work, ice was viewed at the nanoscale by scanning an atomic force microscopy tip over a highly oriented pyrolytic graphite (HOPG) surface in air. At low scan velocities, the tip exhibited stick-slip motion with a period of 0.13 nm corresponding to the scanner step; at higher velocities, the HOPG lattice and the periodicity of the ice were visible. A hexagonal structure with a 0.45 ± 0.04 nm periodicity was observed in which the distance between the second neighbors of the HOPG coincided with the distance of the first neighbors for the ice-like arrangement. Small water clusters were also nucleated with an ice-Ic structure (0.34 ± 0.03 nm), and thus, the ice layers consisted of extensive sets composed of arrangements of hexamers and tetramers.     

纳米结构MnO2的水热合成、晶型及形貌演化

以水热合成方法制备了具有不同微观形貌的纳米结构MnO2, 并以X射线衍射(XRD), 扫描电镜(SEM)和X射线光电子能谱(XPS)等方法对其进行了表征. 跟踪考察了二氧化锰的晶型及微观形貌随水热反应时间的演变过程, 在Ostwald ripening机理作用下, MnO2晶型转化过程为γ-MnO2, α-MnO2和β-MnO2, 同时形貌由微米球转变为海胆结构、空心海胆结构和纳米线.     

一维纳米结构MnO2的微波合成及其电化学性能

以在水热条件下合成的纳米结构γ-MnOOH为前驱物, 以K2S2O8为氧化剂, 采用单模式微波加热法制备出一维纳米结构MnO2. 采用XRD和TEM等手段对样品进行了表征. 以在100 ℃下水热合成的γ-MnOOH纳米纤维为前驱物时, 制得α-MnO2纳米纤维; 以在150 ℃下水热合成的γ-MnOOH纳米棒为前驱物时, 制得β-MnO2纳米棒. 分别用α-MnO2纳米纤维和β-MnO2纳米棒作为Li/MnO2电池的正极材料进行恒电流放电实验, 研究结果显示, α-MnO2纳米纤维的放电容量为270.23 mA·h/g, β-MnO2纳米棒的放电容量为186.66 mA·h/g.     

Effect of calcination temperature on the structure and formaldehyde removal performance at room temperature of Cr/MnO2 catalysts

Research on Chemical Intermediates - In this paper, Cr/MnO2 catalysts were prepared by hydrothermal–calcination method and applied to the catalytic oxidation of formaldehyde (HCHO) at room...     

Nanostructured MnO2: an efficient and robust water oxidation catalyst

Nanostructured MnO(2) exhibits a high turnover frequency for oxygen evolution under visible light and high stability in strong acidic conditions.     

Nanostructured Bi2Te3 synthesized by low temperature aqueous chemical route

Chemical and physical reactions during the low temperature aqueous chemical synthesis of nanostructured Bi₂Te₃ powders were investigated in-situ by pH measurement, color observation of the solution and X-ray diffraction analysis of the powders. It was found that Bi₂Te₃ could be synthesized only in a strong alkaline solution. Bi₂Te₃ nanocapsules were synthesized by the aqueous chemical route at 65 °C with the addition of disodium ethylenediaminetetraacetate salt. High-resolution transmission electron microscopy observation indicates that the nanocapsules are hollow-structured with a wall thickness of about 6 nm. __________ Translated from CHIMICA SINICA, 2005, 63(16)(in Chinese)     

Enhancement of palladium-porphyrin room temperature phosphorescence by alkaline earth metal in deoxycholate aggregates solution

Room temperature phosphorescence (RTP) of three palladium (Pd)-phorphyrins in air-saturated solution of sodium deoxycholate (NaDC) aggregates was measured. RTP of Pd-meso-tetrakis (4-carboxyphenyl) porphyrin (Pd-TCPP) was obviously enhanced in NaDC-aggregates mediated by alkaline earth metal (AEM). Under the same experimental conditions, Ca(2+), Ba(2+) and Mg(2+) induced 200, 90 and 24 times greater enhancement in RTP of Pd-TCPP, respectively. It is ascribed to form the complex of NaDC-aggregate/AEM/Pd-TCPP in the system. The positively charged AEM has a strong capability of co-ordination with negatively charged carboxyl groups of NaDC and Pd-TCPP. The phosphor Pd-TCPP is confined in rigid NaDC-aggregates/AEM system by the coordination which decreases the probability of collision of phosphor with quenchers such as dissolved oxygen molecules and prolongs the lifetime of the phosphor on the triplet state. Long excited-state lifetimes resulted in great enhancement of Pd-TCPP phosphorescence. Observations by optical microscope showed that specific fan-like structures of NaDC were formed under the influence of AEM. Surface tension measurements supported a close interaction between Ca(2+) ions and anion aggregates of NaDC with 1:1 stoichiometric ratio. Due to its outstanding RTP behavior in NaDC-aggregates induced by Ca(2+), Pd-TCPP was used as a RTP probe to detect bovine serum albumin (BSA). A broad linear range from 1.0 × 10(-9) to 9.0 × 10(-7) g mL(-1) was obtained. Detection limit is 2.6 × 10(-11) g mL(-1), the relative standard deviation (n = 6) is 2.3% for 2.0 × 10(-9) g mL(-1) BSA.     

Fluorescence emission of disperse Red 1 in solution at room temperature

In this article, we report the fluorescence emission of Disperse Red 1 in solution at room temperature and pumping at 532 nm with a 25 mW diode laser. We have measured its fluorescence quantum yield in methanol, ethylene glycol, glycerol, and phenol obtaining values as high as 10(-3) in the aliphatic alcohols. The excitation spectra of Disperse Red 1 in all four solvents as well as its excitation anisotropy in glycerol are presented. Applying a Gaussian decomposition method to the absorption spectra along with the support from the excitation spectra, the positions of the different transitions in this pseudo-stilbene azobenzene dye were determined. Solvatochromic and isomerization constraint effects are discussed. Calculations using density functional theory at TD-B3LYP/6-31G*//HF/6-31G* level were performed to interpret the experimental observations.     

Room temperature synthesis of hollow CdMoO(4) microspheres by a surfactant-free aqueous solution route

Hollow cadmium molybdate microspheres have been successfully prepared via a template-free aqueous solution method with the assistance of NaCl at room temperature. The structure and morphology of the CdMoO(4) hollow microspheres were characterized by X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. The microspheres have diameters of 3-6 microm and hollow interiors of 2-3 microm. The shell is composed of numerous single-crystalline nanorods with diameters of 30-120 nm and lengths of 1-2 microm which are radially oriented to the center. A certain concentration of NaCl plays a key important role in the formation process of hollow microspheres, which might provide a suitable chemical environment to favor the formation of hollow CdMoO(4) microspheres. A possible NaCl-induced Ostwald ripening process is proposed for the formation of hollow CdMoO(4) microspheres on the basis of scanning electron microscopy observation of intermediate products at different precipitation stages.     

Synthesis and characterisation of strontium carboxylates formed at room temperature and under hydrothermal conditions

A novel method was developed for the synthesis of highly pure strontium complexes in high yield. Syntheses proceeded along three pathways with optimum conditions being at T?=?120–140°C, a base?:?acid ratio of 1.2 and 15?min reaction-time in an autoclave vessel. Large crystals were readily obtained within hours. The crystal structures of strontium R-glutamate hexahydrate (I) and strontium di(hydrogen S-glutamate) pentahydrate (II) were determined by X-ray powder diffraction methods at 295?K with Rietveld refinement (I: Space group P2₁2₁2₁, Z?=?4, a?=?7.3519(2), b?=?8.7616(2), c?=?20.2627(5)?Å; II: Space group P2₁, Z?=?2, a?=?8.7243(1), b?=?7.2635(1), c?=?14.6840(2)?Å, β?=?100.5414(7)°). Synthesis at room temperature provided four additional new strontium compounds that may be applicable as constituents of pharmaceutical products for the treatment of bone conditions.     

Direct visualization of solution morphology of cellulose in ionic liquids by conventional TEM at room temperature

Taking advantage of the negligible vapor pressure and dissolving features of ionic liquids (ILs), the solution morphology and dissolution process of cellulose in ILs have been visualized directly by conventional transmission electron microscopy (TEM) at room temperature for the first time.     

A triplet carbene surviving a week in solution at room temperature

A stable triplet carbene, having a lifetime at 25 degrees C of 14.5 days in a dilute benzene solution, was realized by simply changing the substituent at the 10 position of the previously most persistent carbene, di[9-(10-phenyl)anthryl]carbene, from a phenyl to a 2,6-dimethyl-4-tert-butylphenyl group.     

Photochemical preparation of CdS hollow microspheres at room temperature and their use in visible-light photocatalysis

CdS hollow microspheres have been successfully prepared by a photochemical preparation technology at room temperature, using polystyrene latex particles as templates, CdSO₄ as cadmium source and Na₂S₂O₃ as both sulphur source and photo-initiator. The process involved the deposition of CdS nanoparticles on the surface of polystyrene latex particles under the irradiation of an 8 W UV lamp and the subsequent removal of the latex particles by dispersing in dichloromethane. Photochemical reactions at the sphere/solution interface should be responsible for the formation of hollow spheres. The as-prepared products were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. Such hollow spheres could be used in photocatalysis and showed high photocatalytic activities in photodegradation of methyl blue (MB) in the presence of H₂O₂. The method is green, simple, universal and can be extended to prepare other sulphide and oxide hollow spheres.     

室温下碘催化直接构建硫化吡唑啉酮

含硫化合物在有机合成、药物化学以及材料化学等领域具有重要的作用.到目前为止,科学家已经在C-S键的构建领域进行了很多工作.在构建C-S键的众多方法中,金属催化的C-S键合成反应是一类很重要的反应,但是此方法存在着催化剂对空气敏感、环境不友好等问题.因此,发展无金属催化的C-S键构建反应受到了人们越来越多的重视.基于我们在碘催化相关反应方面的研究,本文报道了一种碘催化的硫化吡唑啉酮类化合物的合成方法.我们选用3-甲基-1-苯基-2-吡唑啉-5-酮与二苯二硫醚为底物进行条件筛选实验,发现I2(10%)为催化剂,二氧六环为溶剂,H2O2为氧化剂为最优化的实验条件,目标产物硫化吡唑啉酮最高产率为88%.在最优化的反应条件下,我们尝试了带有不同官能团(NO2,Cl,OH等)的吡唑啉酮与二硫醚的反应,均能以较高产率得到目标产物.当含有杂环的二硫醚(2,2'-二硫二吡啶)作为反应底物时,也能以中等以上的产率得到相应的目标产物.另外还进行了对比试验,例如在反应体系中加入自由基捕获剂TEMPO,反应产率会大大降低,说明反应中应该有自由基中间体生成;如果反应体系中不加碘,则反应产率为零;如果反应体系中不加H2O2,则反应产率由88%降低至48%,说明碘和H2O2在反应中都起到了重要作用.通过以上对比试验,提出了可能的反应机理:首先,二硫醚发生均裂反应生成苯硫基自由基,然后苯硫基自由基与碘反应生成亲电的PhSI活性中间体,PhSI与异构化的吡唑啉酮发生亲电取代反应,生成目标产物硫化吡唑啉酮和HI,HI可以被H2O2氧化生成I2继续参与下一轮催化反应.以3-甲基-1-苯基-2-吡唑啉-5-酮与二苯二硫醚为底物,我们对此反应进行了放大试验,结果显示反应产率几乎没有降低,这为此反应的大规模应用奠定了基础.在此,我们发展了一种简单高效的合成硫化吡唑啉酮的反应,此方法无需金属催化剂,利用常见的碘为催化剂就可以以较高的产率得到目标产物.为合成含硫化合物提供了一种新的方法.     

Cavity ring-down observation of Yb3+ optical absorption in room temperature solution

Cavity ring-down spectroscopy is used to probe the optical absorption of the optical pseudo-two level system [Xe]4f¹³ Yb³⁺ in room temperature solution, a situation where the two-color pump-probe luminescence approach commonly used to study the other [Xe]4fⁿ (2 ≤ n ≤ 12) trivalent lanthanide ions fails. A 1 m optical cavity constructed from two highly reflective mirrors is used to obtain ring-down signals as a function of wavelength from 1 mL samples contained in a quartz cuvette placed in the center of the cavity. Absorption spectra constructed from these signals characteristic of the ⁶H_15/2 → ⁴F_9/2 [Xe]4f⁵ Dy³⁺ and the ⁷F₀ → ⁵D₀ [Xe]4f⁶ Eu³⁺ transitions are presented and compared to the corresponding single pass absorption and two-color pump-probe luminescence spectra to obtain sensitivity estimates. Finally the spectrum for the ²F_5/2 → ²F_7/2 [Xe]4f¹³ Yb³⁺ transition for a model Yb³⁺ complex in room temperature solution is obtained using cavity ring-down spectroscopy for the first time.     

Towards ultrafine TiO2 nanocrystal at room temperature

Ultrafine titanium dioxide (TiO₂) nanocrystal has attracted enormous interest due to their unusual quantum and surface effects. Here, we propose a facile route to synthesize ultrafine anatase nanocrystal at room temperature via an aqueous sol–gel method using lactic acid (LA) and acetylacetone (Acac) as double chelators. Transmission electron microscopy (TEM) and size analyzer confirmed that TiO₂ nanocrystal in precursor possessed an average size of ~3 nm with a narrow size distribution. Crystal structure characterized by TEM and X-ray diffraction (XRD) indicated that TiO₂ nanocrystal to be anatase phase. The results of field emission scanning electron microscopy (FE-SEM) and BET surface area exhibited that TiO₂ xerogel powder had mono-dispersed particles size and large BET surface area up to 90 m²/g.     

Transition-metal-free C-arylation at room temperature by arynes

A facile, fluoride-induced transition-metal-free chemoselective α-arylation of β-dicarbonyl compounds (malonamide esters) at room temperature using aryne intermediates has been demonstrated. Selective mono- or diarylation and generation of a quaternary benzylic stereocenter have also been achieved. The methodology will be highly useful for the synthesis of a library of CNS depressant barbiturate drugs like Phenobarbital.