Hu Xuefu, Wang Zhiye, Su Yuming, Chen Peican, Chen Jiawei, Zhang Cankun, Wang Cheng
iChem, State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China.
Inorg Chem. 2020 Apr 6;59(7):4181-4185. doi: 10.1021/acs.inorgchem.0c00373. Epub 2020 Mar 13.
Metal-organic frameworks (MOFs) based on 9,10-diphenylanthracene-derived ligands had been reported to exhibit upconverted fluorescence through triplet-triplet annihilation. We found that zirconium MOFs based on 9,10-diphenylanthracene can also give upconverted fluorescence via two-photon absorption without adding a triplet photosensitizer when a femtosecond pulsed laser is used as the excitation source. By tuning the synthetic condition, we obtained nanoscale MOFs of UiO structure in both octahedral and hexagonal nanoplate shapes, as well as a hexagonal nanoplate of MOFs of hcp-UiO structure and two-dimensional metal-organic layers. All of them, as well as a homogeneous solution of the 9,10-diphenylanthracene ligand, exhibit upconverted fluorescence upon excitation using a laser pulse of 60 fs with a pulse energy of ∼1.1 × 10 nJ/cm (unfocused). Moreover, we observed different emission spectra by two-photon excitation compared to those by one-photon excitation, which indicates access to a unique initial excited state via two-photon excitation. This phenomenon is not observed for a homogeneous solution of the ligand. These nanoscale MOFs may find application in two-photon fluorescence imaging.
据报道，基于9,10 - 二苯基蒽衍生配体的金属有机框架（MOF）通过三重态 - 三重态湮灭表现出上转换荧光。我们发现，当使用飞秒脉冲激光作为激发源时，基于9,10 - 二苯基蒽的锆基MOF在不添加三重态光敏剂的情况下也能通过双光子吸收产生上转换荧光。通过调节合成条件，我们获得了八面体和六边形纳米片状的UiO结构纳米级MOF，以及hcp - UiO结构的MOF六边形纳米片和二维金属有机层。所有这些以及9,10 - 二苯基蒽配体的均匀溶液，在使用60 fs的激光脉冲、脉冲能量约为1.1×10 nJ/cm（未聚焦）激发时都表现出上转换荧光。此外，与单光子激发相比，我们通过双光子激发观察到了不同的发射光谱，这表明通过双光子激发可以进入独特的初始激发态。对于配体的均匀溶液未观察到这种现象。这些纳米级MOF可能在双光子荧光成像中找到应用。
