Syntheses of three terbium complexes as fluorescent probes and their application on the pH detection of routine urine test

By modifying the salicylic-acid moiety with electron-withdrawing or –donating groups, three new terbium complexes（LⅠ·Tb, LⅡ·Tb, L·（Ⅲ）Tb） based on tripodal carboxylate ligands were synthesized. Due to different pull-push electronic effects of ligands, the fluorescence intensities of these terbium complexes significantly varied, that is： LⅡ·Tb 〉L（Ⅲ）·Tb〉 LⅠ·Tb. Meanwhile, the characteristic peaks at 492 nm（5D4→7F6） and 547 nm（5 D4→7F5） showed ＂Off–On–Off＂ fluorescence response to various p H conditions,which indicated that all of them can be used as the highly sensitive pH fluorescent probes. Notably, using LⅡ·Tb with the best fluorescence performance as a probe, some patients＇ urine samples can be easily monitored through the response triggered by pH value. Therefore, LⅡ·Tb has the potential to auxiliarily diagnose some diseases in clinical practice through p H detection of routine urine test.

Synthesis of 1,8-naphthalimide-based fluorescent nano-probes and their application in pH detection

Two kinds of fluorescent nano-probes（pH-A and pH-B） with different diameters for the determination of H＋concentration, based on photo-induced electron transfer mechanism, were synthesized through click reaction. In which 1,8-naphthalimide was employed as the fluorophore and N,N-dimethylethylenediamine as the receptor. The effects of particle size and linker length on the photophysical properties of the probe were studied. The results revealed that the nano-probes were more sensitive toward pH with increasing particle size. The fluorescence intensity at 529 nm（I529） of the nano-probe p H-A of 120 nm exhibited good linear relationship with solution＇s pH in the range of 6–8. The probe p H-A displayed excellent selectivity and competition toward proton over other possible coexisted ions, and it could be applied to detect pH in realistic samples（river water, urine）.