Eu/Tb-MOF as fluorescence sensors for the detection homocysteine in human serum performance and mechanistic investigation.

Abnormal homocysteine (Hcy) levels in human serum have been associated with serious or vital diseases, making the reliable and easy detection of Hcy important to clinical analysis and biological study. In this work, five phosphorescent Ir(C^N)(N^N) complexes (Ir) having aldehyde group were synthesized as probes (C^N and N^N denoted ligands). A discussion was conducted on their molecular structure, electronic structure, photophysical parameters, and Hcy sensing ability, revealing the correlations between their molecular structures and performances. Ir emission was enhanced (by ∼ two folds) and blue-shifted (by 100 nm) after meeting Hcy (free state), via a cyclization reaction between the -CHO group (from Ir) and Hcy. In addition, using RE(BTC) as a supporting material (RE = Tb and Eu), the Ir(III) probe was loaded onto a supporting material of RE(BTC) (HBTC = 1, 3, 5-benzenetricarboxylic acid). The emission color was changed by increasing Hcy concentration. Straight working curves were obtained with LOD (limit of detection) of 1.9 μM and a response time of ∼200 s. The novelty of this work was the combination of Ir with RE(BTC), which offered enhanced and blue-shifted emission upon Hcy via a cyclization reaction. This demonstrated a high level of sensitivity towards homocysteine detection.