Morphology-controlled electrochemical sensing of erbium-benzenetricarboxylic acid frameworks for azo dyes and flavonoids

Generally, materials with different morphologies are expected to have different electrochemical properties. Here, three kinds of erbium-based metal-organic frameworks with different morphologies were prepared using erbium nitrate and 1,3,5-benzenetricarboxylic acid (H3BTC) as the source in N, N-dimethylformamide (DMF) by adding various amounts of ammonium acetate (CH3COONH4). The characterization of X-ray diffraction, infrared spectroscopy and X-ray photoelectron spectroscopy proved that the obtained materials were Er-BTC. Scanning electron microscope measurements indicated that the amount of CH3COONH4 had obvious effects on the morphology. More importantly, the active sensing area and interface electron transfer ability of Er-BTC were controlled by the morphology, which revealed by rotating ring disk electrode and electrochemical impedance spectroscopy. Moreover, the prepared Er-BTC with different morphologies exhibited different signal enhancement ability toward the oxidation of azo dyes (allura red and rhodamine B) and flavonoids (quercetin and luteolin). Based on the morphology-controlled sensing of Er-BTC, a highly sensitive detection platform were developed for allura red/rhodamine B and quercetin/luteolin, with detection limits of 0.30/0.56 nM and 0.22/0.14 nM. Besides, this new method was successfully used in drink and tea samples, and the results were in good agreement with those obtained from high-performance liquid chromatography.