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A fluorescent method for detection of tetracyclines (TCs) in milk was developed by using the NH 2 -MIL-53(Al) nanosensor synthesized via a one-pot hydrothermal method. The nanosensor had a crystalline nanoplates structure with rich groups of −NH 2 and −COOH. The −NH 2 /−COOH of NH 2 -MIL-53(Al) reacted with the −CO−/−OH of TCs to form a complex. The electron of −NH 2 /−COOH from the NH 2 -BDC ligand transferred to the −CO−/−OH of TCs. −NH 2 of the NH 2 -MIL-53(Al) interacted with the −CO−/−OH of TCs by hydrogen bonding. The quenching efficiency of the inner filter effect (IFE) was calculated to contribute 57−89%. The synergistic effect of photoinduced electron transfer (PET) and IFE account for fluorescence quenching. TCs were quantitatively detected in milk samples with recoveries of 85.15−112.13%; the results were in great accordance with high-performance liquid chromatography (HPLC) (P > 0.05), confirming the NH 2 -MIL-53(Al) nanosensor has potential applicability for the detection of TCs in food matrix.

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Rapid fabrication of flexible and stretchable sensors is essential for the emerging applications of wearable devices. In this study, a chitosan‐based water ink realizes fabrication of flexible and stretchable stain sensor by simply writing the ink and leaving it to dry for ≈15 min at room temperature. It is found that chitosan is an excellent binding material. The fabricated sensor shows an excellent gauge factor of 64 within strain 1%–8%, and can be stretched up to 60%. More importantly, the sensor can be directly written on the subject, and sensors written on plants show that plants can response to mechanical injuries within a few minutes. These results show that this method reduces the energy and time consumption in the fabrication procedure, realizes direct fabrication of sensors on subjects for wearable monitoring, and meets the requirements for personalized and on‐site applications. So, this chitosan‐based ink provides an attractive strategy for the fabrication and application of wearable devices.

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