Dopamine Sensing Based on Ultrathin Fluorescent Metal–Organic Nanosheets

The importance of dopamine (DA) detection as a biomarker for several diseases, especially Parkinson’’s disease, has persuaded scientists to develop new nanomaterials for efficient sensing of DA in clinical samples. Ultrathin metal–organic nanosheets due to their exceptional thickness, large surface area, and flexibility are endowed with many accessible active sites and optimal surface interaction with the target analyte molecules. In this regard, a novel layered fluorescent metal–organic nanomaterial with a honeycomb topology based on europium, [Eu(pzdc)(Hpzdc)(H2O)]n (ECP) (H2pzdc = 2,3-pyrazine dicarboxylic acid), was synthesized. X-ray crystallography revealed that the 3D supramolecular architecture of ECP is constructed from noncovalent interactions of coordinated water molecules between the 2D layers along the b axis. These layers that are only ∼4 nm thick were conveniently separated through ultrasound-induced liquid phase exfoliation. Optical studies show that the reduction of ECP thickness enhances the fluorescence intensity and serves as an efficient optical marker for DA detection. ECP nanoflakes exhibited fast response and high selectivity for DA detection in clinical samples. Good linearity for DA detection in the range of 0.1–10 μM with a detection limit of 21 nM proves the potential of ECP nanoflakes in DA sensing applications.