Photophysical performance of a rhodamine-MOF composite structure and its sensing potential for picric acid

Abstract

For the following paper, a rhodamine-MOF composite structure, RO-EuBTC, was constructed for the optical recognition of PA (picric acid) by the covalent combination of an organic rhodamine dye and rare earth MOF. By means of XRD, IR, TGA, this composite structure was analyzed and confirmed. Its photophysical analysis suggested two sensing aspects towards PA. Be more specific, RO-EuBTC's rhodamine absorption intensity in visible region was proportional to PA, showing colorimetric sensing. RO-EuBTC's rhodamine emission intensity was proportional to PA as well, with its Eu emission intensity inversely proportional to PA, showing self-calibrated sensing signals. Both sensing aspects showed linear response and high selectivity towards PA. Their LOD value was as low as 2.2 μM. Detailed analysis confirmed its sensing mechanism as the combination of two parts, namely the rhodamine emission enhancement sparked by PA's proton and the Eu emission quenching caused by EuBTC's electron transfer to PA. RO-EuBTC was found superior to traditional optical sensing materials based on MOFs owing to its two sensing aspects and the possibility for naked eye detection.