Luminol-Eu3+-Gd3+-functionalized mesoporous silica for ultrasensitive detection of tetracycline antibiotics and smartphone-assisted sensing analysis.

An organic-inorganic hybrid nanoprobe, namely LML-D-SBA@Eu3+-Gd3+, was constructed, with SBA-15 acting as the carrier material, and luminol and Eu3+ acting as fluorescence channels to achieve ratiometric signals that eliminate external interference (accurate detection). Gd3+ was used as a sensitizer to amplify the red emission of Eu3+ (ultrasensitive detection). In TCs detection, the luminol emission at 428 nm was quenched due to the photoinduced electron transfer mechanism, and the Eu3+ emission at 617 nm was sensitized due to the synergistic energy transfer from TCs and Gd3+ to Eu3+. 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.

Rhodamine derivative-functionalized mesoporous silica-Al3+ hybrid material for fluorescence "turn-on" detection of tetracycline antibiotics in aqueous media.

The organic-inorganic hybrid material was prepared by embedding 2-amino-3',6'-bis(diethylamino)spiro[isoindoline-1,9'-xanthen]-3-one (RBH) onto mesoporous SBA-15 silica and coordinating it with Al3+ (RBH-SBA-15-Al3+). RBH-SBA-15-Al3+ was used for the selective and sensitive detection of tetracycline antibiotics (TAs) in aqueous media based on the binding site-signaling unit mechanism, in which Al3+ acted as the binding site and the fluorescence intensity at 586 nm as the response signal. The addition of TAs to RBH-SBA-15-Al3+ suspensions resulted in the formation of RBH-SBA-15-Al3+-TAs conjugates, which realized the electron transfer process and turned-on fluorescence signal at 586 nm. The detection limits for tetracycline (TC), oxytetracycline, and chlortetracycline were 0.06, 0.06, and 0.03 µM, respectively. Meanwhile, the detection of TC was feasible in real samples, such as tap water and honey. In addition, RBH-SBA-15 can operate as a TRANSFER logic gate by using Al3+ and TAs as input signals and the fluorescence intensity at 586 nm as output signal. This study proposes an efficient strategy for the selective detection of target analytes by introducing interaction sites (e.g. Al3+) with target analytes in the system.