Histidine‑Stabilized Copper Nanoclusters as a Fluorescent Probe for Selective and Sensitive Determination of Vitamin B_(12)

Herein,we report the highly sensitive and selective determination of vitamin B_(12)(VB_(12))using histidine-stabilized copper nanoclusters(His-CuNCs)as a fluorescent probe by the spectrofluorometry method.The as-synthesized His-CuNCs were characterized by UV–Vis absorption,steady-state emission,and high-resolution transmission electron microscopy measurements.His-CuNCs exhibited an emission maximum around 443 nm,when excited at 350 nm.The emission intensity of His-CuNCs was significantly quenched by the addition of VB_(12),hinting that the synthesized probe can be employed for sensing of VB_(12).Based on the decrease in emission intensity,the concentration of VB_(12) was determined and the emission intensity of His-CuNCs can be quenched by VB_(12) via fluorescence resonance energy-transfer mechanism.His-CuNCs showed high selectivity toward the determination of VB_(12) in the presence of other potentially interfering vitamins,cations,and anions.In addition,the proposed sensing platform displayed a sensitive response to VB_(12) in the linear range of 4.00–28.00×10^(−6) mol dm^(−3) with a limit of detection of 3.30×10^(−9) mol dm^(−3).The proposed sensing system is simple,low cost,selective,and sensitive for the determination of VB_(12) in biological samples.

Interaction of TbCl_3 and lanthanide complexes with poly(N-vinylpyrrolidone)

The interaction of TbC13 and lanthanide（Ⅲ） β-diketonate complexes with poly（N-vinylpyrrolidone） （PVP） polymer was studied using fluorescence spectroscopy. In the presence of PVP the emission of Tb3＋ in cthanolic solution of TbCl3 significantly in- creased owing to the excitation energy transfer from PVP to Tb3＋ ions, which was more efficient as compared to a direct excitation of the Tb3＋ 4f75d1 levels. In contrast, emission of NEt4Tb（hfa）4 and NEt4Eu（hfa）4 complexes was almost completely quenched in solu- tion containing PVP. The PVP bound both Ln3＋ ions and hfa ligands which caused decomposition of Ln-hfa complexes and switched off the excitation energy transfer from the ligand to the emitting Ln3＋ ion. The important role of hydrogen bonds in stabilization of in- teraction ofhfa ligands with PVP was indicated.