Premium
Highly Stable Mixed‐Lanthanide Metal–Organic Frameworks for Self‐Referencing and Colorimetric Luminescent pH Sensing
Author(s) -
Xia Tifeng,
Cui Yuanjing,
Yang Yu,
Qian Guodong
Publication year - 2017
Publication title -
chemnanomat
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.947
H-Index - 32
ISSN - 2199-692X
DOI - 10.1002/cnma.201600331
Subject(s) - lanthanide , luminescence , deprotonation , ligand (biochemistry) , excited state , chemistry , metal organic framework , inorganic chemistry , materials science , photochemistry , ion , organic chemistry , optoelectronics , atomic physics , physics , biochemistry , receptor , adsorption
A strategy utilizing mixed‐lanthanide metal–organic frameworks (MOFs) for self‐referencing and colorimetric luminescent pH sensing has been developed. The mixed‐lanthanide MOFs Eu x Tb 1− x Hdpda ( x= 0.097, 0.205, 0.303, H 4 dpda=4‐(3,5‐dicarboxyphenyl)pyridine‐2,6‐dicarboxylic acid) exhibit excellent stability in phosphate buffer solution with pH values varying from 3.90 to 7.50. Density functional theory (DFT) calculations indicate that the deprotonation of uncoordinated carboxyl groups in ligands results in the elevation of the triplet excited state (T 1 ) energy level of H 4 dpda, thus increasing the energy transfer probability from the T 1 to 5 D 4 level of Tb 3+ . As a result, the emission intensity of Tb 3+ in Eu x Tb 1− x Hdpda increases gradually while that of Eu 3+ is almost not changed with the pH varying from 3.90 to 7.50. The intensity ratios of Eu 3+ to Tb 3+ can be correlated to the pH value, suggesting they are promising self‐referencing luminescent pH sensors. Furthermore, the significant pH‐dependent emission color change enables them to act as a luminescent colorimetric pH sensor for in situ and real‐time pH imaging. Because the energy transfer between the ligand and lanthanide ion can be easily tuned by selecting an appropriate ligand to further optimize the pH response range and sensitivity, such a strategy opens a new perspective for the development of self‐referencing luminescent pH sensors.