Luminol-Eu-Gd-functionalized mesoporous silica for ultrasensitive detection of tetracycline antibiotics and smartphone-assisted sensing analysis.

An organic-inorganic hybrid nanoprobe, namely LML-D-SBA@Eu-Gd, was constructed, with SBA-15 acting as the carrier material, and luminol and Eu acting as fluorescence channels to achieve ratiometric signals that eliminate external interference (accurate detection). Gd was used as a sensitizer to amplify the red emission of Eu (ultrasensitive detection). In TCs detection, the luminol emission at 428 nm was quenched due to the photoinduced electron transfer mechanism, and the Eu emission at 617 nm was sensitized due to the synergistic energy transfer from TCs and Gd to Eu. The fluorescence intensity at 617 and 428 nm showed ratiometric changes as indicated by notable color changes from blue to red. The detection limits for TC and OTC were 0.21 and 0.08 ng/mL, respectively. To realize a facile, rapid, and cost-effective detection, we constructed a portable intelligent sensing platform based on smartphones, and it demonstrated great potential for on-site detection of TCs.