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101.
Fluorescence of complexes of EuⅢwith aromatic carboxylic acid-1,10-phenanthroline@舒万艮
@周忠诚
@牛聪伟~~ 相似文献
102.
Using first principles calculations, we study fundamental mechanism of spontaneous reduction reaction of Eu3+ to Eu2+ in eutectic LiCl‐KCl molten salt. We decouple the reaction Gibbs free energy into enthalpy and entropy contributions by using rigorous thermodynamic formalism. Key structural features of the solvation shell are characterized by the radial distribution function and the coordination number. Compared with Eu2+, the Eu3+ ion has a more rigid framework of the solvation shells, corroborating its stronger electrostatic interaction with neighboring ligands of Cl? ions and a more favorable state on the aspect of enthalpy. Computations on vibrational frequency, however, pose significant contribution of vibrational entropy to the reaction Gibbs free energy for the reduction. Vibration frequency of Eu2+ is smaller than that of Eu3+, driving a more positive change of the entropy in the reduction reaction. Furthermore, an Eu2+ diffuses more quickly than an Eu3+ in the LiCl‐KCl molten salt with switching mechanism of ligand Cl? ions in the solvation shell. Our results propose that the spontaneity of the reduction reaction is driven by the entropic contribution by overcoming the penalty of the reaction enthalpy. 相似文献
103.
Eu2 isthemostwell knownandextensivelyused activatorinmanysilicates,boratesandotherinorganic compounds[1~4].Itsemissioncomesfrom5d→4ftran sition,andtheemissionwavelengthcanvaryinvery broadranges.Sincethe5delectronsarelocatedat outershelloftheeuropiumion,… 相似文献
104.
P. J. PETTER 《International journal of cosmetic science》1984,6(5):249-260
A review is given of the manufacture, properties and applications of the anionic surfactants commonly known as taurates and isethionates (fatty acid sulphoalkyl amides and esters, respectively). Originally developed in the 1930s for textile processing, these surfactants are used increasingly in the cosmetic field, particularly those derived from coconut fatty acid. Both types are produced from sodium isethionate, HO°C2H4SO3Na. The acyl isethionate, R°COO°C2H4SO3Na, is obtained by reaction with a fatty acid (‘direct process’). or fatty acid chloride (‘indirect process’). The direct process is cheaper but requires extreme conditions which can lead to discoloration of the product and a loss of shorter chain fatty acid components. The N-methyl-N-acyltaurate, R°CON(R1)C2H4SO3Na, is obtained by Schotten-Baumann reaction of a fatty acid chloride with N-methyltaurine, which is derived from sodium isethionate via methylamine. Taurates and isethionates retain the benefits of the soaps to which they are structurally similar, but chemical modifications have eliminated many undesirable features. Thus they combine good detergency and wetting with high foaming, and maintain their performance in hard or salt water. Taurates are stable to hydrolysis over the whole pH range. Isethionates are prone to hydrolysis at high (>8) or low (<5) pH, but this does not normally present a problem in cosmetic formulations. Above all, these surfactants are characterized by their extreme mildness to skin. Syndet and syndet/soap bars based on isethionate can be formulated at neutral pH (‘Dove type’bars) instead of the alkaline pH of soap, and have been shown in various studies to be milder than soap and better tolerated by the young, the old and those with sensitive skins. Similarly, isethionates have been shown to be less irritating than other anionic or amphoteric surfactants used in cosmetics. The difference has been related to the negligible effect of isethionate on the water-binding capacity of stratum corneum. Other cosmetic applications besides toilet bars include shampoos (excellent cleaning, mild to scalp, some hair conditioning effects), liquid soaps (mild for all-over body use), bubble baths (copious stable foam, efficient lime soap dispersal, low irritancy), skin creams and lotions (emulsification, alleviation of ‘dry skin’), baby care products (ultra-mild cleansing bars and milks, impregnated baby wipes) and oral products (foaming agents with low toxicity for toothpastes and mouthwashes). 相似文献
105.
106.
A model for wire drawing lubrication by soap using realistic soap rheology, plastic at low temperature, non-Newtonian viscous at high temperature, is presented. A simplified analysis of the lubricant flow gives film thickness as a function of soap rheology and drawing pass parameters, which is shown to agree with experiment 相似文献
107.
Emission from Mo‐O charge‐transfer state and Yb3+ emission in Eu3+‐doped and nondoped molybdates under UV excitation 下载免费PDF全文
Molybdates of Li+ and Yb3+ are studied to investigate the luminescence under UV excitation. LiYb(MoO4)2 and Eu3+‐doped LiYb1‐xEux(MoO4)2 (x=001–1.0) phosphors were synthesized by solid state reaction under mixing of Eu2O3, Yb2O3, Li2CO3 and MoO2 in air atmosphere. Two broad absorption bands centered at 333 and 236 nm are observed in LiYb(MoO4)2 compound. They are attributed to the 1A1→1T1 and 1T2 transitions due to the O2?→Mo6+ electron transfers in MoO4 tetrahedron. An emission band with a peak at about 440 nm is found, which is attributed to the 3T1→1A1 transition of MoO4. Appearance of near‐infrared (NIR) Yb3+ emission observed under UV excitation is understood by the MoO4→Yb3+ Foerster‐Type energy transfer due to spectral overlap between the low‐energy tail of the broad 440 nm emission band and the high‐energy tail of the broad Yb3+ absorption band and due to short Yb3+‐MoO4 distance. Yb3+ emission observed in LiYb1?xEux(MoO4)2 by Eu3+ excitation is understood by the Eu3+→Yb3+ energy transfer by cross‐relaxation (CR) process between the 5D0→7F6 Eu3+ transition and the 2F7/2→2F5/2 Yb3+ transition. The CR efficiency shows maximum efficiency of 0.24 at x=0.15 of higher acceptor Yb3+ concentration than donor Eu3+ concentration. Three Yb3+ emission bands with peaks at 994, 1002, and 1023 nm are observed, depending on the excitation wavelength. This is explained by less‐shielded 4f electrons of Yb3+ by the 5s25p6 outermost electron shells, which are also responsible for unusual broadband Yb3+ absorption and emission. From appearance of NIR Yb3+ emission under excitation by not only UV light but also red light, these compounds are expected to be suitable for efficient photovoltaic application to Si‐based solar cells. 相似文献
108.
109.
CaSiO3:Eu的发光性质 总被引:3,自引:2,他引:3
采用高温固相反应法合成出CaSiO3:Eu^3 荧光体。研究了其荧光性质。样品的晶体结构为α-CaSiO3和β-CaSiO3的混合相,其激发光谱的峰位位于240,320,362,383,394,415nm,分别对应于O→Eu的电荷迁移带和^7F0.1-^5H3,^5D4,^5GJ,^5L6,^5D3的吸收跃迁。在240nm和394nm激发下,Eu^3 离子的^5D0→^7F2电偶极跃迁最强,表明Eu^3 离子占据更多的非反演中心格位。研究了不同电荷补偿剂对发光性能的影响,以Li^ 离子的电荷补偿效果最好。 相似文献
110.
配合物Eu(Sal)_2(phen)_2(NO_3)的合成及荧光性能的研究 总被引:1,自引:0,他引:1
用硝酸铕、水杨酸与邻菲罗啉为原料合成了配合物Eu(Sal)2(phen)2(NO3),考察了配体用量和溶剂用量等因素对反应的影响。通过元素分析、红外光谱和紫外光谱确定了配合物的组成及结构,并通过荧光光谱对其荧光性质进行了研究。 相似文献