Syntheses and Co-Fluorescence of Complexes of Eu (III)/Gd (III) with Thienyltrifluoroacetonate, Terephthalic Acid and Phenanthroline

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1 Americn Journl of Anlyticl Chemistry, 014, 5, Published nline December 014 in cires. yntheses nd Co-luorescence of Complexes of Eu (III)/Gd (III) with Thienyltrifluorocetonte, Terephthlic Acid nd Phennthroline Xuehui Zho 1*, Zhongling Hu 1, Hiyun Jing 1, eipeng Jio, Zhengxing Wng 1 1 Key Lbortory of Green Pckging nd Appliction Biologicl notechnology of Hunn Province, Hunn University of Technology, Zhuzhou, Chin College of Chemistry nd Chemicl Engineering, Centrl outh University, Chngsh, Chin Emil: * zhoxuehui005@16.com Received 9 ctober 014; revised 7 ovember 014; ccepted 13 December 014 Copyright 014 by uthors nd cientific Reserch Publishing Inc. This work is licensed under the Cretive Commons Attribution Interntionl License (CC BY). Abstrct A series of complexes of europium (III)/gdolinium (III) with -thienyltrifluorocetonte (HTTA), terephthlic cid (TPA) nd phennthroline (Phen) were synthesized by coprecipittion. The resulting complexes including Eu (TPA)(TTA) 4Phen, Eu 1.4Gd 0.6(TPA)(TTA) 4Phen, Eu 1.0Gd 1.0(TPA)(TTA) 4Phen nd Eu 0.8Gd 1.(TPA)(TTA) 4Phen were chrcterized by elementl nlysis, IR spectroscopy nd therml stbility nlysis. The results of nlysis indicte tht the complexes obtined hve similr binucler structure with ech other. The therml stbility nlysis indictes tht the complexes Eu (TPA)(TTA) 4Phen nd Eu 1.0Gd 1.0(TPA)(TTA) 4Phen possess good therml stbility, which melt t ~41 C nd decompose t ~370 C C corresponding to the formtion of the complexes. The fluorescence spectr of Eu (1-x)Gd x(tpa)(tta) 4Phen (x = 0-1) complex powders nd their doped silic gels were studied. The co-fluorescence effect of Gd 3+ ions in complex powders is different from tht of their doped silic gels. The optimum concentrtion of Gd 3+ for complex powders nd their doped silic gels is 0.5 nd 0.3 (molr frction), respectively. The co-fluorescence distinction of Gd 3+ ions for complex powders nd their doped silic gels is preferbly interpreted from the proposed binucler structure together with monomoleculr compositions of the complexes for the first time. Both intermoleculr energy trnsfer nd intr moleculr energy trnsfer in cross binucler monomoleculr EuGd(TPA)(TTA) 4Phen re thought to be responsible for the co-fluorescence effect of the complex powders; yet only the ltter is thought to be responsible for the co-fluorescence effect in silic gels, for the complex molecules in this cse re isolted from ech other. * Corresponding uthor. How to cite this pper: Zho, X.H., Hu, Z.L., Jing, H.Y., Jio,.P. nd Wng, Z.X. (014) yntheses nd Co-luorescence of Complexes of Eu (III)/Gd (III) with Thienyltrifluorocetonte, Terephthlic Acid nd Phennthroline. Americn Journl of Anlyticl Chemistry, 5,

2 Keywords Co-luorescence, Europium, Terephthlic Acid, -Thienyltrifluorocetonte, ilic Gel 1. Introduction The fluorescence enhncement of the trivlent rre erth complexes still enjoys growing interest due to their importnt ppliction in time-resolved fluoroimmunossys, electro-opticl devices nd morphous luminescent mterils [1]-[4]. Generlly, the fluorescence enhncement cn be chieved through lignd sensitiztion. In this process, ultrviolet light is firstly bsorbed by orgnic Lignds. Then, the bsorbed energy is trnsferred to rre erth ions nd mkes them send out their chrcteristic light. rgnic lignds hve usully brod bsorption bnd in the region of ner ultr-violet. If the energy level of the triplet stte of orgnic lignds mtches well with the emission energy level of rre erth ions, the energy trnsfer of lignds to rre erth ions is very efficient. This will result in the gret increse in fluorescence intensity of rre erth ions [5]. or this purpose, vrious lignds hve been used, the more populr ones being the β-diketones [6]-[8], such s -thienyltrifluorocetonte, benzoylcetone nd dibenzoylmethne. The romtic crboxylic cids s n excellent lignd re lso populr [9]-[11], such s trimesic cid, terephthlic cid nd pyromellitic cid. The fluorescence of rre erth complexes cn lso be further enhnced by the use of synergistic gents, such s trioctylphosphine oxide, phennthroline, orgnic phosphtes nd sulphoxides. Another method to increse the fluorescence of the trivlent rre erth complexes is through the use of certin lnthnide ions such s L 3+, Gd 3+ nd Tb 3+ [1]-[15]. In the presence of these ions, the fluorescence enhncement of some rre erth complexes cn be obtined. This process is referred to s co-fluorescence, which is extensively studied in the mononucler complexes of Europiun (III) ions with β-diketones lignds, such s Eu(TTA) 3 Phen [1], Eu(Dbm) 3 Phen [13] nd Eu(TTA) 3 TPP. As fr s the mononucler complex is concerned, the co-fluorescence cn be found in micellr environment [16] [17]. In n ctul solution, there is no co-fluorescence becuse the long distnce between the cheltes mkes intermoleculr energy trnsfer impossible. In solids, especilly in coprecipittes, the distnce between the complex molecules cn be short enough to incur n intermoleculr energy trnsfer. However, for the binucler or polynucler complexes their co-fluorescence properties re different from those of mononucler complexes. Therefore, it is very significnt to study the cofluorescence effect of the binucler or polynucler complexes in solids. uch studies cn be helpful in better understnding of the co-fluorescence mechnism. Recently, synthesis nd fluorescent properties of the mononucler complexes of europium (III) with β-diketones lignds (e.g. -thienyltrifluorocetonte (HTTA), dibenzoylmethide) nd Phennthroline (Phen) or trioctylphosphine oxide hve been shown [1] [13] [18]. However, the studies on synthesis nd cofluorescence of complexes of europium (III)/gdolinium (III) with -thienyltrifluorocetonte, terephthlic cid (TPA) nd Phennthroline hve not been reported yet. In this pper, in order to investigte the co-fluorescence properties of binucler complexes, the bridging lignd TPA is used to link rre erth ions to form the new binucler complexes Eu (1-x) Gd x (TPA)(TTA) 4 Phen (x = 0-1). And the co-fluorescence mechnism of Gd 3+ in complex powders nd their doped silic gels is preferbly interpreted from the binucler structure together with monomoleculr composition of the complexes for the first time. In ddition, IR bsorption spectr nd therml stbility of the bove mentioned complexes were lso studied.. Experimentl Detils.1. Regents nd Apprtus 99.99% Eu 3 nd 99.98% Gd 3 were purchsed from Jingxi outh Rre Erth Metls Institute in Chin. -thienyltrifluorocetonte (HTTA), terephthlic cid (TPA), Phennthroline (Phen) nd other regents were ll nlyticl grde nd used without further purifiction. C, H, nlysis ws performed on n Americn Perkin-Elmer 400 II CHL elementl nlyzer. The percentges of rre erth ions were determined by complexometric titrtion with EDTA. The infrred spectr 1314

3 were mesured t room temperture on icolet-550 spectrophotometer (Americn Perkin-Elmer) using KBr pellets in the spectrl rnge of cm 1. Differentil thermonlysis (DTA) ws performed in HDT- 40 thermonlyticmeter using luminum crucibles with ~18.40 mg of smple, under dynmic synthetic ir tmosphere (40 ml min 1 ) nd heting rte of 10 C min 1 in the temperture rnge of 30 C C. The thermogrvimetric (TG) curves were recorded with thermoblnce model HDT-40 in the temperture intervl of 30 C C, using pltinum luminum with ~18.0 mg of smple, under dynmic synthetic ir tmosphere (40 ml min 1 ) nd heting rte of 10 C min 1. A luorolog L3-L 1 (Americn JBI YV) pectrometer ws used to record excittion nd emission spectr of the complex powders nd their doped silic gels. The bndwidth of monochromtors ws set t.5 nm for both excittion nd emission... ynthesis of Complexes The complex Eu (TPA)(TTA) 4 Phen ws prepred in the following steps. In the first step, stndrd solution of europium (III) ( mol L 1 ) ws prepred by dissolving Eu 3 in hot hydrochloric cid, evporting up to syrup nd diluting with ethnol to desired volume. HTTA, TPA nd Phen were dissolved seprtely in ethnol with molr rtio of 4:1:. ubsequently EuCl 3 nd HTTA solutions were mixed with molr rtio of 1:, djusting ph vles to 5.0, stirred nd refluxed for 40 min keeping temperture in wter-bth. Then ccording to molr composition of formul Eu (TPA)(TTA) 4 Phen, Phen nd TPA solutions were dded dropwise, keeping ph vles 6.5, stirred nd refluxed until the ppernce of n ornge precipitte. The solid product ws filtered, wshed nd recrystllized in ethnol. The complexes Eu (1 x) Gd x (TPA)(TTA) 4 Phen were prepred by the similr process s Eu (TPA)(TTA) 4 Phen, except tht the mixture solution of EuCl 3 nd GdCl 3 ws used insted of the EuCl 3. The products obtined re n ornge precipitte..3. Incorportion of the Complexes into ilic Gels ilic gels were prepred by hydrolysis nd condenstion of tetrethoxysilne i(c H 5 ) 4 (TE). TE nd H were used ccording to molr rtio of 1:4.3 with the proper mount of dimethylformmide (DM) s solvent. The DM solution of the complexes ws subsequently dded to the silic precursor solution (n complex : n TE = 1:0). Then the mixed solution ws refluxed in 70 C wter bth until geltion occurred. The resulting gels were dried t 100 C for two weeks for mesurement purposes. 3. Result nd Discussion 3.1. Composition of Complexes The rre erth percentges were determined by complexometric titrtion with EDTA. Anlyticl dt of C, H, nd rre erth ions percentges (found/clculted) for the complex Eu (TPA)(TTA) 4 Phen re Eu (III): 17.15/ 17.74; C: 44.76/44.84; H:.0/.10; : 3.58/3.7; for the complexes Eu 1.4 Gd 0.6 (TPA)(TTA) 4 Phen re rre erth (III): 17.76/17.90; C: 44.60/44.76; H:.05/.10; : 3.39/3.7; for the complexes Eu 1.0 Gd 1.0 (TPA)(TTA) 4 Phen re rre erth (III): 17.81/18.00; C: 44.57/44.70; H: 1.99/.10; : 3.45/3.6; nd for the complexes Eu 0.8 Gd 1. (TPA)(TTA) 4 Phen re rre erth (III): 18.01/18.05; C: 44.50/44.67; H: 1.97/.10; : 3.37/3.6. The elementl nlyticl dt re consistent with the clculted vlues of the generl formul of the Eu (III) complexes. 3.. Chrcteriztion of Complexes Tble 1 shows some results of IR spectr. The presence of crboxylte groups in the Eu (III) complexes ws definitely confirmed by both the symmetric stretching bnds t cm 1 nd the symmetric stretching t cm 1. The seprtions ( = υ s υ s ) between υ s (coo) peks nd υ s (coo) pers re in the rnge of cm 1 in the Eu (III) complexes, which re ttributed to the bidentte chelting, bidentte bridging nd tridentte chelting-bridging coordintion modes of crboxylte groups with rre erth ions, since the seprtions ( = υ s υ s ) in the Eu (III) complexes re lower thn tht in TPA (Δ = 168 cm 1 ) [19] [0]. urthermore, owing to the gret steric hindrnce of the complexes Eu (1 x) Gd x (TPA)(TTA) 4 Phen, the bidentte bridging nd tridentte chelting-bridging coordintion of crboxylte groups with rre erth ions becomes more difficult thn the bidentte chelting coordintion does. Thus, the coordintion mode of crboxylte groups of 1315

4 Tble 1. The IR spectr of some complexes, where L = (TPA)(TTA) 4 Phen. Compounds υ s (coo)/m 1 υ s (coo)/cm 1 Δ (υ s υ s) υ (co)/cm 1 υ (C=)/cm 1 TTA 1680 TPA Phen 1596 EuL Eu 1.4Gd 0.6L Eu 1.0Gd 1.0L Eu 0.8Gd 1.L TPA with rre erth ions is minly the bidentte chelting coordintion mode in the complexes, nd the proposed chemicl structure of the complexes is binucler structure. The IR spectr lso show displcement of υ (C=) stretching from ~1680 cm 1, in free TTA lignd, to ~1605 cm 1 in the complexes, nd displcement of υ (C=) stretching from ~1596 cm 1, in free Phen lignd, to ~1559 cm 1 in the complexes, indicting tht rre erth ions re coordinted by the oxygen or nitrogen toms [1]. The DTA nd TG curves of Eu (TPA)(TTA) 4 Phen nd Eu 1.0 Gd 1.0 (TPA)(TTA) 4 Phen re shown in igure 1 in the temperture rnge from 50 C to 600 C. It cn be seen tht the DTA nd TG curves of the complex Eu (TPA)(TTA) 4 Phen (igure 1(A)) present similr profile to tht of the complexes Eu 1.0 Gd 1.0 (TPA)(TTA) 4 Phen (igure 1(B)). Both Eu (TPA)(TTA) 4 Phen nd Eu 1.0 Gd 1.0 (TPA)(TTA) 4 Phen possess good therml stbility, which melt t ~41 C nd decompose t ~370 C C, with no decomposition before the melting point. These indicte tht both hve similr chemicl structure corresponding to the formtion of the new complexes. Moreover, in the intervl 50 C - 00 C, the TG curves of the complexes do not present ny event reltive to wter loss, which indictes tht the new complexes re in nhydrous form. This is corroborted by elementl nlysis. The fluorescence excittion nd emission spectr of the solid stte complexes were performed in luorolog L3-L 1 pectrometer. igure shows the excittion spectr of the Eu (TPA)(TTA) 4 Phen, Eu 1.4 Gd 0.6 (TPA)(TTA) 4 Phen nd Eu 0.8 Gd 1. (TPA)(TTA) 4 Phen complex powders recorded in the spectrl rnge of nm by monitoring the emission t the hypersensitive 5 D 0 7 trnsition. These complex excittion spectr show strong brod bnd rnging from 50 to 45 nm with the optimum excittion wvelength t ~38 nm, nd they re entirely different from the excittion spectrum of Eu 3+ (without the orgnic lignds) []. These indicte tht the lignds hve trnsferred the energy bsorbed to the Eu 3+ ion, leding to the fluorescence enhncement of Eu 3+. The fluorescence emission spectr of the complexes Eu (1 x) Gd x (TPA)(TTA) 4 Phen (x = 0-1) re ll similr except the reltive intensity. igure 3 shows only the emission spectr of Eu (TPA)(TTA) 4 Phen, Eu 1.4 Gd 0.6 (TPA)(TTA) 4 Phen nd Eu 0.8 Gd 1. (TPA)(TTA) 4 Phen recorded in the rnge of nm with the optimum excittion wvelength t room temperture. It cn be seen tht five typicl Eu (III) emission bnds pper t ~58, ~593, ~615, ~654, ~704 nm, corresponding to 5 D 0 7 0, 5 D 0 7 1, 5 D 0 7, 5 D 0 7 3, nd 5 D 0 7 4, respectively. The chrcteristic emission peks of Eu 3+ ions do not chnge with the ddition of cofluorescence Gd 3+ ions. Compred with the powdered complexes, the silic gels doped with these complexes show weker split lines of the Eu 3+ ion. The phenomenon cn be ccounted for in the following wy. or the powdered complexes, Eu 3+ ions with surrounding environment of different lignd groups is in site without center of inversion, so the emission peks split into more lines under the lignd field. However, silic gel is kind of noncrystlline substnce with porous mcrostructure. And the complex molecules fixed in the pores re highly ordered. The weker split lines of Eu 3+ re observed becuse the symmetry of Eu 3+ ion in the powder is lower thn tht in silic gel. In igure 3(A), the reltive emission intensity of the complex powder of Eu (TPA)(TTA) 4 Phen is weker thn tht of Eu 0.8 Gd 1. (TPA)(TTA) 4 Phen. While for the silic gels doped with these complexes, in igure 3(B), the reverse is true. But compred with the silic gels doped with Eu 1.4 Gd 0.6 (TPA)(TTA) 4 Phen, the reltive emission intensity of the silic gels with Eu (TPA)(TTA) 4 Phen remin weker. The intermoleculr energy trnsfer cnnot explin perfectly these chnges of the fluorescence intensity. 1316

5 DTA b TG/% Temperture/ C (A) DTA b TG/% Temperture/ C (B) igure 1. DTA () nd TG (b) curves of the complexes Eu (TPA)(TTA) 4 Phen (A) nd Eu 1.0 Gd 1.0 (TPA)(TTA) 4 Phen (B). Reltive intensity (. u.) b c 3.3. Energy Trnsfer Processes λ /nm igure. Excittion spectr of the complex powders () Eu 0.8 Gd 1. L, (b) Eu 1.4 Gd 0.6 L nd (c) Eu L, where L = (TPA)(TTA) 4 Phen. To investigte the co-fluorescence effect of Gd 3+ for the complex powders nd their doped silic gels, We would ssume tht co-fluorescence Gd 3+ ions hve no influence on the fluorescence intensity of Eu 3+ in the complexes, the reltive emission intensity vlue I clc of the complex powders nd their doped silic gels ws clculted ccording to the molr frction of Eu 3+ in different co-fluorescence complexes, nd the I exp is the reltive emission intensity vlue for experiment, so the rtios of I exp nd I clc cn be gotten. The results re lso listed in Tble. 1317

6 A B Reltive intensity (. u.) c b λ /nm (A) igure 3. Emission spectr of the complex powders (A) nd their doped silic gels (B), () Eu 0.8 Gd 1. L, (b) Eu 1.4 Gd 0.6 L nd (c) Eu L, where L = (TPA)(TTA) 4 Phen. Tble. luorescence spectr pek positions nd reltive intensities of the complex powders nd their doped silic gels, where L = (TPA)(TTA) 4 Phen. Complexes λex/nm complex powders λem/nm (reltive intensity) in silic gel λem/nm (reltive intensity) 5 D 0 7 I clc Iexp Iexp I clc b c (B) 5 D 0 7 I clc Iexp Iexp/I clc Gd L Eu 0.Gd 1.8L Eu 0.6Gd 1.4L Eu 0.8Gd 1.L Eu 1.0Gd 1.0L Eu 1.Gd 0.8L Eu 1.4Gd 0.6L Eu 1.6Gd 0.4L Eu 1.8Gd 0.L Eu L Reltive intensity (. u.) λ /nm As is well known tht the energy trnsfer for the complexes from the lignd to the lnthnide ions cn tke plce vi intr moleculr energy trnsfer mode, nd the energy trnsfer cn lso tke plce vi intermoleculr trnsfer mode. In this study, we think tht the co-fluorescence distinction of Gd 3+ ions for complex powders nd their doped silic gels cn be preferbly interpreted from the proposed binucler structure together with monomoleculr compositions of the complexes. ince the coordintion mode of crboxylte groups of TPA with rre erth ions is minly the bidentte chelting coordintion mode in the complexes. The proposed binucler structure my be given in chemes 1()-(c). or certin x vlue in Eu (1 x) Gd x (TPA)(TTA) 4 Phen, the complex powders were prepred by coprecipittion, so the complexes re composed of monomoleculr EuGd(TPA)(TTA) 4 Phen, Eu (TPA)(TTA) 4 Phen nd Gd (TPA)(TTA) 4 Phen. In ddition, the chemicl structure of the mononucler complex Eu(TTA) 3 Phen is lso given in cheme 1(d) [8]. igure 4 shows the reltionship between the percentges of every monomoleculr compositions nd the content of Gd 3+ ions in the complexes. It cn be seen from igure 4 firstly, tht with the increse of x vlue, i.e., the contents of Gd 3+ ions, the percentges of monomoleculr EuGd(TPA)(TTA) 4 Phen nd Gd (TPA)(TTA) 4 Phen increse. ince energy cn only be trnsferred from molecule to other molecules t short distnces, nd the complex powders were prepred by coprecipittion, the short distnce between Gd (TPA)(TTA) 4 Phen molecules nd Eu (TPA)(TTA) 4 Phen molecules in the coprecipitte mkes the intermoleculr effective energy trnsfer be possible. In ddition, intr moleculr energy trnsfer in cross binucler monomoleculr EuGd(TPA)(TTA) 4 Phen increses. They result in the increse of the emission intensity of the complex powders. When x vlue is 0.5, the percentge of monomoleculr EuGd(TPA)(TTA) 4 Phen reches mximum, the intr 1318

7 Eu Eu Eu Gd () (b) Gd Gd Eu 3 (c) cheme 1. Chemicl structures of the monomoleculr Eu L (), EuGdL (b), Gd L (c) nd Eu(TTA) 3 Phen (d), where L = (TPA)(TTA) 4 Phen. (d) % b c X / Gd igure 4. The reltionship between the percentges of monomoleculr EuGdL (), Eu L (b) nd Gd L (c) nd the content of Gd 3+ ions in the complexes., where L = (TPA)(TTA) 4 Phen. moleculr energy trnsfer reches lso mximum. Then with further increse of x vlues the intr moleculr energy trnsfer decreses, on the other hnd, intermoleculr energy trnsfer is thought to be concerned with the molr rtios of Eu (TPA)(TTA) 4 Phen nd Gd (TPA)(TTA) 4 Phen. o the optimum concentrtion of Gd 3+ in the complex powders Eu (1 x) Gd x (TPA)(TTA) 4 Phen is ~0.5 (molr frction). In the silic gel doped with these complexes, the complex molecules re trpped in the pores nd isolted from ech other. The long distnce between complex molecules in the silic gel mkes the intermoleculr energy trnsfer impossible. Yet intr moleculr energy trnsfer in cross binucler monomoleculr EuGd(TPA)(TTA) 4 Phen is not ffect by silic gel. o with the increse of the contents of Gd 3+ ions, the percentge of the EuGd(TPA)(TTA) 4 Phen increses, the fluorescence intensity of the silic gel doped with these complexes increses. But when the contents of Gd 3+ ions ttin to certin vlue, becuse of the decrese of Eu (TPA)(TTA) 4 Phen, the fluorescence intensity of the silic gel doped with these complexes decrese. The optimum concentrtion of Gd 3+ in silic gel doped is ~0.3 (molr frction). These interprettions from the binucler structure together with monomoleculr composition of the complexes re consistent with the results of the experiment. 1319

8 4. Conclusions A series of complexes of europium (III)/gdolinium (III) with -thienyltrifluorocetonte, terephthlic cid nd Phennthroline, showing strong red fluorescence nd good therml stbility hve been synthesized. Compositions of these complexes re reveled to be Eu (1 x) Gd x (TPA)(TTA) 4 Phen. The cofluorescence properties nd the mixed complexes Eu (1 x) Gd x (TPA)(TTA) 4 Phen (x = 0-1) re thought to be, for certin x vlue in Eu (1 x) Gd x (TPA)(TTA) 4 Phen, composed of EuGd(TPA)(TTA) 4 Phen, Eu (TPA)(TTA) 4 Phen nd Gd (TPA)(TTA) 4 Phen. The fluorescence enhncement of the Eu (III) complexes is observed by the ddition of reltive chep Gd 3+ ions. The optimum concentrtion of Gd 3+ is 0.5 (molr frction). The mechnism of the fluorescence enhncement is preferbly interpreted from the proposed binucler structure together with the percentges of every chemicl composition in the Eu (III) complexes. Both intermoleculr energy trnsfer mode nd intr moleculr energy trnsfer mode re thought to be responsible for the fluorescence enhncement of the complex powders; yet only intr moleculr energy trnsfer is thought to be responsible for the fluorescence enhncement the silic gels doped with these complexes, for the complex molecules re isolted from ech other in this cse. Both intermoleculr energy trnsfer between monomoleculr Gd (TPA)(TTA) 4 Phen nd monomoleculr Eu (TPA)(TTA) 4 Phen nd intr moleculr energy trnsfer in cross binucler monomoleculr EuGd(TPA)(TTA) 4 Phen re thought to be responsible for the co-fluorescence of the complex powders; yet only intr moleculr energy trnsfer in cross binucler monomoleculr EuGd(TPA)(TTA) 4 Phen is thought to be responsible for the co-fluorescence in silic gels, for the complex molecules in this cse re isolted from ech other. Acknowledgements The uthors cknowledge the finncil supports from the Chinese tionl ture cience oundtion (o , ). References [1] Richrdson,.. (198) Terbium(III) nd Europium(III) ions Ions s Luminescent Probes nd tins for Biomoleculr ystem. Chemicl Reviews, 8, [] Wng, Z.M. (000) Advnce in tudy of Light Trnsform rm ilm Doped with Rre Erth in Chin. Chinese Rre Erths, 1, [3] Li, B., M, D., Zhng, H.J., et l. (1998) Electroluminescence Devices Bsed on Monohexdecyl Phthlte Terbium. Thin olid ilms, 35, [4] Liu, H.G., eongte, P., Kiwn, J., et l. (004) Influence of Lignds on the Photoluminescent Properties of Eu 3+ in Europium β-diketonte/pmma-doped ystems. Journl of Luminescence, 106, [5] Andrzej, M.K., tefn, L., Zbingniew, H., et l. (000) Improvement of Emission Intensity in Luminescent Mterils Bsed on the Antenn Effect. Journl of Alloys nd Compounds, 300, [6] Yng, J.H., Zhu, G.Y. nd Wu, B. (1987) Enhnced Luminescence of the Europium/Terbium/Thenoyltrifluorocetone/ 1,10-Phennthroline/urfctnt ystem nd Its Anlyticl Appliction. Anlytic Chimic Act, 198, [7] Zhng, R.J. nd Yng, K.Z. (000) luorescence Lifetime nd Energy Trnsfer of Rre Erth β-diketone Complexes in rgnized Moleculr ilms. Thin olid ilms, 363, [8] Zhng, R.J., Liu, H.G., Zhng, C.R., et l. (1997) Influence of everl Compounds on the luorescence of Rre Erth Complexes Eu(TTA) 3 Phen nd m(tta) 3 Phen in LB ilms. Thin olid ilms, 30, [9] Pniqrhi, B.., Peter,. nd Viswnthn, K.. (1997) Cofluorescence of Eu 3+ in Complexes of Aromtic Crboxylic Acid. pectrochimic Act Prt A, 53, [10] Mji,. nd Viswnthn, K.. (008) Lignd-ensitized luorescence of Eu 3+ Using phthlene Crboxylic Acids s Lignds. Journl of Luminescence, 18, [11] Zho, G.H., Zho,.G., Go, J.Z. nd Kng, J.W. (1997) ensitivity nd tbility Induced by Cyclodextrin in the luorescence Anlysis of Terbium(III) Ions Using Trimesic Acid. Bulletin des ocietes Chimiques Belges, 106, [1] Wng, Z.X., hu, W.Y., Zhou, Z.C., Liu, Y.. nd Chen, H. (003) luorescence Properties nd Appliction of Doping Complexes Eu 1-x L x (TTA) 3 Phen s Light Conversion Agents. Journl of Centrl outh University of Technology, 130

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