Smartphone-integrated chameleon ratiometric lanthanide MOF sensor: Semi-quantitative fluorescence for real-time biomarker discrimination in complex environment and foods

Developing fast and convenient sensors for 2,6-dipicolinic acid (DPA) is of great importance for enhancing microbiological safety in food and healthcare, with significant implications for broader industrial applications. This work presents lanthanide metal-organic frameworks ([Ln(H 2 atiip) 2 (phen) 2 (H 2 O) 5 (MeOH)] n , Ln = Eu, Tb), named as CUST-865 and CUST-866. This is the first time that principal component analysis method is utilized to distinguish DPA. DPA molecules precisely replace the coordinated water molecules in the metal-organic framework, enabling the construction of an open ratiometric lanthanide fluorescent sensor. Furthermore, a novel “one-to-two” logic sensor with a single-input and dual-output configuration was developed. This system exhibits chameleon-like behavior, dynamically adapting its output signals in response to the input. Furthermore, smartphone platforms equipped with color recognizer applications enable detection of DPA. The detection limits for CUST-865 and CUST-866 were determined to be 0.19 μM and 1.15 μM in tap water, and 0.22 μM and 1.11 μM in milk powder.