镨和镱掺杂Ba2SiO4∶Eu^2＋荧光材料的合成与发光性能

采用高温固相反应法分别合成了变价稀土镨和镱离子掺杂的绿色荧光粉[Ba（2-n-1.5x）REx]SiO4∶nEu^2＋（n=0.03,RE=Pr,Yb;x=0,0.02,0.05,0.10）。结果表明：所有合成荧光粉的激发峰均为250-400 nm的宽峰,与近紫外LED的发射光波长相匹配。发射峰位于450-550 nm之间,是Eu2＋的5d-4f跃迁的典型发射。Pr^3＋和Yb3＋的掺入并未改变Ba2SiO4∶Eu^2＋的相组成,但对荧光强度的影响大,且与掺杂元素、掺杂量和煅烧温度相关。当掺杂Pr^3＋和Yb3＋的量为x=0.02时,经1150℃煅烧所得荧光粉的发光强度分别是未掺杂时的595%和168%。证明三价稀土离子掺杂可以导致基质中的电荷缺陷而敏化Eu^2＋离子的发光,而变价稀土离子的掺杂可以大大提高电荷缺陷,导致荧光强度的进一步提高。     

Two New Diterpene Alkaloids from the Roots of Spiraea japonica var. Acuta

Spiraea japonica L. (Rosaceae) is widely distributed in Yunnan Provence, P. R. China. Previous chemical investigations on S. japonica and its varieties have led to the report of 7 new atisane-type diterpenoids and 38 new diterpene alkaloids of atisine- and hetisine-type1-11. This paper describes the isolation and structure elucidation of two new diterpene alkaloids named spiratines A and B (1-2). Their structures were elucidated on the basis of 1D and 2D NMR experiments (HMQC, HMBC, 1…     

Crystal and Molecular Structure of N-(1-Ethoxycarbonyl- ethyl)1-Ethoxycarbonylmethyl-3-ethyl-1,2,3,4- tetrahydro-4-oxo-1,3,2-benzodiazaphosphorin- 2-carboxamide 2-Oxide

1 INTRODUCTIONOrganophosphorus compounds are ubiquitous in nature and they have broad applications in the fields of agriculture and medicine. During the past two decades, (-ketophosphonates and their derivatives have attracted considerable attention because these compounds are endowed with special physical, chemical and pharmacological properties due to the proximity of the carbonyl and the phosphoryl groups[1～6]. For example, it is well known that phosphonoformic acid (PFA) is effectiv…     

Two New Steroidal Saponins from Diuranthera inarticulata

There are only three species in the genus Diuranthera (Liliaceae), which is endemic in the southwest of China1. Four steroidal saponins, diuranthosides A-C and chloromalo-side A were isolated from the fresh roots of D. major. This paper deals with the structure elucidation of two new steroidal saponins, diuranthosides D and E, which were isolated from the methanolic extract of whole plant of D. inarticulata Wang et K. Y. Lang.Diuranthoside D (1), [(]-38 (c 0.08, pyridine), afforded galac…     

Study on Phase Equilibrium Properties for CO_(2+) Cosolvent Binary Systems

Recently, the application of supercritical fluid technology is very interested, and it is applied in many areas for its special properties. The performance of supercritical fluid (SCF) as a solvent can be greatly affected by addition of an entrainer to the system. An entrainer can be added to a supercritical fluid to enhance its solvent strength and/or selectivity. Critical point data for these dilute supercritical fluid-cosolvent systems are imperative for the design of efficient separation …     

Three New Coumarins from Micromelum integerrimum

Micromelum integerrimum (Rutaceae) is a shrub growing in Yunnan Province. Leaves and barks of this plant have been used for the treatment of dysentery, and arthritis1. Previous researches revealed that this plant contained coumarins2-8. Micromelin, the main chemical constituent of this plant, showed significant inhibition against leukaemia P-388 cell line (T/C 149% at 10 mg/kg) but was inactive in lower doses, and also showed significant activity (T/C 228% at 1.25 mg/kg) against Lewis lung…     

Two-Parameter Stochastic Resonance in a Model of Electrodissolution of Fe in H_2SO_4

IntroductionStochastic resonance (SR) is a nonlinear effect which describes the optimal detection of a weak periodic signal by the action of external noise in nonlinear systems. SR was originally proposed to account for periodicity in the Earth's ice ages1, and it has been observed in a wide range of biological2-4 , physical5 and chemical6 systems. The systems mentioned above which may give rise to SR have a denominator despite many examples of SR in different scientific areas. It is noted…     

Synthesis and Crystal Structure of Triethyl 1,2,2-triphenylpyrrolidine-3,4,5-tricarboxylate,A Proline Derivative

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Design and Synthesis of Chiral Molecular Tweezers Based on Deoxycholic Acid

Molecular tweezers is a novel type of artificial receptors, which not only offer the advantage of efficient construction but also their surfaces can be tailored for specific applications. The clefts of molecular tweezers are particularly effective in regard to complementarity with substrates since functional groups attached to the interior of the cleft converge on substrates held inside1. So, in recent years, the molecular tweezers receptors have attracted more and more attention in molecular …     

First Total Synthesis of 5_α-Hydroxy-isopterocarpolone

Sesquiterpenic compounds of the Eudesmane family have attracted considerable attention due to their intriguing biological properties1,2, particularly significant antifeedant activity, cell growth inhibitory and plant growth regulating activities.In 1996, J. Hu and co-workers3 had isolated eudesmane sesquiterpene 5?-hydroxy-isopterocarpolone 1 from the aerial parts of chinese folk medicine Artemisia eriopoda and elucidated its structure by spectropic methods. Herein, we reported the first tota…