Scheme 1. Schematic diagram of the MIL-101(FeCu)@AuNPs-LFIA. (A) Synthesis of MIL-101(FeCu)@AuNPs-Ab. (B) The detection principle of MIL-101(FeCu)@AuNPs-LFIA.
Fig. 1. SEM image of (A) MIL-101(FeCu), (B) MIL-101(FeCu)@AuNPs. (C) XRD patterns of MIL-101(FeCu) and MIL-101(FeCu)@AuNPs. (D) XPS survey spectra of MIL-101(FeCu) and MIL-101(FeCu)@AuNPs. (E) Au 4 f peaks in MIL-101(FeCu)@AuNPs composites. (F) Zeta potential of MIL-101(FeCu), MIL-101(FeCu)@AuNPs, and MIL-101(FeCu)@AuNPs-Ab.

Fig. 2. Evaluation of photothermal properties of MIL-101(FeCu)@AuNPs. (A) Thermal images of MIL-101(FeCu)@AuNPs with different concentrations after laser irradiation. (B) Time-temperature profiles of MIL-101(FeCu)@AuNPs at various concentrations (20, 40, 60, 80, 100 μg/mL) under laser irradiation at 1.5 W cm⁻². (C) Time-temperature profiles of MIL-101(FeCu)@AuNPs (100 μg/mL) under irradiation with different laser powers (0.4, 0.8, 1.2, 1.6, 2.0 W cm⁻²). (D) Photothermal stability of MIL-101(FeCu)@AuNPs over three heating-cooling cycles. (E) Photothermal conversion efficiency of MIL-101(FeCu)@AuNPs. (F) Ultraviolet absorption spectra of MIL-101(FeCu)@AuNPs, MIL-101(FeCu), and AuNPs. (G) Time-temperature profiles of MIL-101(FeCu)@AuNPs, MIL-101(FeCu), and AuNPs. (H) Comparison of LFIA performance among MIL-101(FeCu)@AuNPs, MIL-101(FeCu), and AuNPs. (N: Negative; P: Positive; IR: Inhibition rate).
Fig. 3. (A) pH tolerance of MIL-101(FeCu)@AuNPs. (B) Salt ion tolerance of MIL-101(FeCu)@AuNPs. (C) Batch-to-batch variation of MIL-101(FeCu)@AuNPs-based LIFA. (D) Results of ka and KD for bare Ab, MIL-101(FeCu)@AuNPs-Ab, and AuNPs-Ab. Optimization of the MIL-101(FeCu)@AuNPs analytical conditions: (E) the coupling pH, (F) the diluent of Ab, (G) the type of blocking agent, (H) the probe amount.Fig. 4. Performance evaluation of MIL-101(FeCu)@AuNPs-LFIA. (A) Test strip images and calibration curves for detecting RIF in milk under colorimetric mode; (B) Test strip images and calibration curves for detecting RIF in milk under photothermal mode; (C) Selectivity evaluation of MIL-101(FeCu)@AuNPs-LFIA for RIF detection; (D) Correlation diagram of MIL-101(FeCu)@AuNPs-LFIA and LC-MS/MS detection results for RIF.