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Design and Synthesis of Mixed Lanthanide Metal-Organic Framework Materials with Color Tunable and Temperature Sensing Properities

Author: RaoXingTang
Tutor: QianGuoDong
School: Zhejiang University
Course: Materials Physics and Chemistry
Keywords: metal-organic framework materials lanthanide luminescence energytransfer mechanism white light emission temperature sensing
CLC: O621.3
Type: PhD thesis
Year: 2014
Downloads: 11
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Recently years, luminescent metal-organic frameworks (MOFs) materials have attracted extensive attention by their diverse applications in lighting, display, automobiles, transportation, imaging, fluorescence detection and sensor. Not only the metal centers (for example, luminescent lanthanide ions) and organic linkers can produce luminescent emissive sources, the metal-organic charge transfer and the guest solvent molecules can also generate luminescence; thus a variety of combination of metal centers and organic linkers have led to a series of luminescent MOFs of diverse topologies with the emissive wavelengths ranging from300to1550nm. However, it is still very challenging and difficult of MOF materials with only one metal ion to tune luminescent color. In this dissertation, we improved an effective approach to synthesize MOFs materials with color tuable luminecence properities. By mixing small amout of Tb3+and Eu3+to provide additional green (543nm) and red (614nm) light from Tb3+and Eu3+emissions, and combining the original blue light from the organic linkers, we can easily explore white light emitting MOFs materails. Our approach might be applied to a variety of lanthanide metal-organic frameworks to generate tunable and white light emitting materials.Moreover, the MOF thermometers based on the temperature dependent luminescence intensity and/or the lifetime of one transition, may suffer from variation of the sensor concentration, excitation power, and the drifts of the optoelectronic systems such as lamps and detectors.In contrast, the luminescent intensity ratio is not compromised, thus is expected to enable more accurate thermal measurements through the mixed-lanthanide metal-organic framework (M’LnMOF) approach. With the reasonable selection of organic ligands, several new M’LnMOFs were developed, which display an excellent performance as ratiometric luminescent thermometers in the cryogenic temperature range (10-300K) and the physiological temperature range (25-45℃), respectively.A series of isostructural lanthanide MOFs materials, Ln(TDPA)(H2O)5(LnTIPA; Ln=Nd3T, Sm3+, Gd3+, Eu3+, Tb3+, or Dy3+; H2TIPA=5-(1H-tertrazol-5-yl)isophthalic acid) were hydrothermally synthesized by the reaction of H2TIPA with Ln(NO3)3at160C for2days. By mixing small amount of Tb3+and Eu3+, the M’ LnMOFs of GdTIPA:x%Tb3+,y%Eu3+exhibit both the characteristic transitions of Tb3+and Eu3+excited at330nm, in addition to the emission at410nm from H2TIPA ligand. The color of the GdTIPA:x%Tb3+,y%Eu3+can be systematically tuned through different combination of the amount of Tb3+and Eu3+from0.1%to10%molar percentage. When the emission intensities at408,543, and614nm are comparable, the white light emission can be readily produced. Accordingly, the optimized combination of Tb3+and Eu3+concentrations in the GdTIPA:x%Tb+,y%Eu3+for the resulting the white light emission are GdTIPA:1.0%Tb3+,2.5%Eu3+and GdTIPA:1.5%Tb3+,3.0%Eu3+with the corresponding CIE coordinate (0.3363,0.3343) and (0.3367,0.3373), respectively; which are both very close to the coordinate for pure white-light (0.3333,0.3333), thus ideal for white-light emission according to the1931CIE coordinate diagram. This strategy provided a new design approach for MOF white light emitting materials.To improve the quantum yield of white light emitting MOFs materials, we chose an organic ligand PDA with much lower T1to construct MOFs materials. A new two-dimensional lanthanide La2(PDA)3(H2O)5(we term this MOF as ZJU-1;ZJU=Zhejiang University; PDA=pyridine-2,6-dicarboxylate) of square planar (4,4) topology was developed. The original ZJU-1emits blue (408nm) light attributed to the emissive organic PDA linkers. Mixing of small amount of Tb3+and Eu3+led to the formation of isostructural ZJU-1:Tb3+and ZJU-1:Eu3+which can provide additional green (543nm) and red (614nm) light from Tb3+and Eu3+emissions, respectively, excited at312nm; thus the white light emitting MOFs ZJU-1:Tb3+,Eu3+have been realized by mixing1%to2%molar amount of Tb3+and Eu3+into the host framework solid. The white light emission samples are ZJU-1:1.0%Tb3+,2.0%Eu3+and ZJU-1:1.5%Tb3+,2.0%Eu3+with the corresponding CIE coordinate (0.3269,0.3123) and (0.3109,0.3332), respectively; which are both very close to the coordinate for pure white-light (0.3333,0.3333), thus ideal for white-light emission according to the1931CIE coordinate diagram. Compared with the white light emitting MOFs of GdTIPA:1.0%Tb3+,2.5%Eu3+and GdTIPA:1.5%Tb3+,3.0%Eu3+the quantum yields of ZJU-1:1.0%Tb3+,2.0%Eu3+and ZJU-1:1.5%Tb3+,2.0%Eu3+were enhanced about three times. This researc h initiated an improtant design approach for MOF white light emitting materials with high quantum yields.A series of isostructural lanthanide MOFs Ln(PIA)(HPIA)(H2O)2.5(LnPIA; Ln=Y3+, Nd3+, Sm3+, Gd3+, Eu3+, Tb3+, Dy3+, Ho3+, Er3+, or Tm3+; H2PIA=5-(Pyridin-4-yl)isophthalic acid) were hydrothermally synthesized by the reaction of H2PIA with Ln(NO3)3at160℃for2days. The temperature-dependent luminescence properities of TbPIA、EuPIA and Tb1-xEuxPIA were investigated. As expected, the representative mixed lanthanide MOF Tbo.9Euo.1PIA exhibits a significantly different temperature-dependent luminescent behaviour with respect to the emissions of Eu3+at615run and Tb3+at546nm. With the temperature increases, the emission intensity of both Tb3+and Eu3+ions keep unchanged at low temperature range (14-100K). However, at100-300K temperature range, the emission intensity of the Tb3+ions decreases, while that of the Eu3+increases. Moreover, the absolute temperature measurement can be linearly correlated to the temperature dependent luminescent intensity ratios of ITb/TEu from100to300K, whose absolute sensitivity is up to3.53%·K-1, which is much higher than that of most reported MOF thermometers. The results indicated that the sensitivity of the mixed lanthanide metal-organic framework thermometers could be significantly enhanced sensitivity by selecting organic ligands with reasonable triplet state energy, and this strategy provided a new design approach for MOF thermometers.A series of isostructural lanthanide MOFs,[Ln(BPDA)(NO3)(DMF)2](DMF)(LnBPDA, Ln=Gd3+, Eu3+, or Tb3+; H2BPDA=biphenyl-3,5-dicarboxylic acid) were solvothermally synthesized. Focus on the development of new MOF theremometers with wider sensing range, especially in the physiological temperature (300~320K) range., we have targeted a new ratiometric MOF thermometer Tb0.8Eu0.2BPDA. The absolute temperature can be linearly correlated to the temperature dependent luminescent intensity ratios of ITb/IEu in Tb0.8Eu0.2BPDA both from30to55℃and from60to80℃, and the absolute sensitivity were up to2.22%-K-1and1.69%·K-1, respectively. Moreover, the maximum relatve sensitivity of Tb0.8Eu0.2BPD A was up to1.19%·K-1at physiological temperature range, pointing out the possibility of using this MOFs to measure physiological temperatures in biological applications.

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