Intrinsic quantum yields and radiative lifetimes of lanthanide tris(dipicolinates)
Intrinsic quantum yields and radiative lifetimes of lanthanide tris(dipicolinates)
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DOI：
10.1039/b816131c
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发表时间：
2009-01-01
影响因子：
3.3
通讯作者：
Buenzli, Jean-Claude G.
中科院分区：
文献类型：
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作者：
Aebischer, Annina;Gumy, Frederic;Buenzli, Jean-Claude G.
三价稀土离子在环境中对其发光的敏化效率(ETA(SENS))是设计高发射分子建筑物和材料的关键参数。对ETA(SENS)的评估需要分别测量配体和金属激发下的总量子产率和本征量子产率。我们描述了一种改进的积分球，可以在少量的固体样品或溶液上绝对测定这些量(60亩L)。随着Cs-3[Ln(Dpa)(3)]溶液(Ln=Eu，Tb)浓度的增加，球体的发射光强度与吸收光强度的线性响应被测试。对于Eu，总量子产额(Q(L)(Eu)=29+/-2%)和内禀量子产额(Q(Eu)(Eu)=41+/-2%)允许直接计算Eta(SENS)(71+/-6%)，而辐射寿命(tau(Rad)=4.1ms+/-0.3ms)是由Q(Eu)(Eu)和观测寿命计算的。本征量子产额与用Werts等人提出的简化方程从发射参数中提取的值相匹配。但是，另一方面，根据JO参数计算的自发跃迁几率的理论估计误差为-25%(3.15ms)。在Cs-3[Tb(Dpa)(3)]的情况下，D-5(4)7F6发射的摩尔吸收系数和二吡啶甲酸盐三重态的吸收光谱的摩尔吸收系数在溶液中重叠较小。Na-3[Yb(Dpa)(3)]在水溶液中的总量子产率很低(0.015+/-0.002%)，原因是敏化效率较低(8%)和较小的本征量子产率(Q(Yb)(Yb)=0.178+/-0.003%；tau(Rad)=1.31+/-0.02ms)。为了从寿命估算Yb在水溶液中的本征量子产率，建议取1.2-1.3ms的值。
The efficiency with which the surroundings of trivalent lanthanide ions sensitize their luminescence (eta(sens)) is a key parameter in the design of highly emitting molecular edifices and materials. Evaluation of eta(sens) requires the measurement of the overall and intrinsic quantum yields obtained upon ligand and metal excitation, respectively. We describe a modified integration sphere enabling absolute determination of these quantities on small amounts of solid samples or solutions (60 mu L). The sphere is tested for linear response of emitted versus absorbed light intensities with increasing concentration of Cs-3[Ln(dpa)(3)] solutions (Ln = Eu, Tb). The overall (Q(L)(Eu) = 29 +/- 2%) and intrinsic (Q(Eu)(Eu) = 41 +/- 2%) quantum yields obtained for Eu allow the direct calculation of eta(sens) (71 +/- 6%) while the radiative lifetime (tau(rad) = 4.1 +/- 0.3 ms) is calculated from Q(Eu)(Eu) and the observed lifetime. The intrinsic quantum yield matches the value extracted from emission parameters using the simplified equation proposed by Werts et al. but, on the other hand, the theoretical estimate using spontaneous transition probabilities calculated from Judd-Ofelt (JO) parameters is off by -25% (3.15 ms). In the case of Cs-3[Tb(dpa)(3)], the molar absorption coefficient of the D-5(4) 7F6 emission and the absorption spectrum of the dipicolinate triplet, this overlap being smaller in the case of the solution. The overall quantum yield of Na-3[Yb(dpa)(3)] in aqueous solution is very low (0.015 +/- 0.002%) due to both poor sensitization efficiency (8%) and small intrinsic quantum yield (Q(Yb)(Yb) = 0.178 +/- 0.003%; tau(rad) = 1.31 +/- 0.02 ms). For evaluating intrinsic quantum yields of Yb in aqueous solutions of coordination compounds from lifetimes, a value of 1.2-1.3 ms is recommended.