Heterometallic BiIII-EuIII Cluster-embedded Antimonotungstate: Rational Design and Dual-Mode Ascorbic Acid Detection Integrating Fluorescent Sensing and Smartphone-Assisted Onsite Assay.

Accurate and reliable detection of ascorbic acid (AA) is of paramount significance for clinical diagnosis and health surveillance. Consequently, the rational design of advanced functional materials and the exploration of their potential in AA sensing have emerged as a pivotal research frontier. Herein, a heterometallic EuIII-BiIII cluster-encapsulated antimonotungstate (HDMEA)9 Na18H3{[Bi10Eu2(H2O)4(DMEA)2(H2OA)4W10O36][B-α-SbW9O33]6}·124H2O (1, DMEA = N,N-dimethylethanolamine, H2OA = oxalic acid) was successfully synthesized via a multicomponent co-assembly strategy. Notably, 1 exhibits intense fluorescence emission in aqueous media and functions as a highly sensitive fluorescent sensor for AA, achieving a low detection limit of 0.038 μM in a linear range of 40-200 μM. Intriguingly, the aqueous solution of 1 undergoes a distinct color transition from colorless to orange upon the addition of AA. Capitalizing on this chromogenic response, a portable sensing platform was further constructed, which transduces visual color signals into digital readouts through a smartphone-based colorimetric application, realizing quantitative detection of AA with an LOD of 0.45 μM in the linear range of 0-400 μM. Both the 1-based fluorescent sensor and the smartphone-assisted colorimetric assay were successfully validated for the detection of AA in real samples. This work elucidates the unique synergistic interactions between Eu3+ and Bi3+ ions in the fabrication of multicomponent polyoxometalates and highlights the immense potential of polyoxometalate-based materials for applications in environmental monitoring and biomedical sensing.