Preparation, Characterization And Chemosens Properties Of Water Soluble Rare-earth(Ⅲ) Chemosensors For Determination Of Chromium(Ⅲ)

With the development of society, the heavy metal ion pollution has become a topic of common concern around the world. The pollution of Cr3 + is a serious problem. Although instrumental analyses such as atomic absorption or atomic emission spectroscopy (AAS or AES), colorimetry, bio-sorption, electrochemical and potentiometric are currently used in applications relevant to the detection of chromium ion, they have sophisticated experimental methods and low sensitivity . Therefore, great attention is attached to develop selective chemosensors for chromium. Due to its simplicity, instantaneous response and high selectivity, fuorimetric detection of Cr³⁺ has great advantages over other detection techniques. So it is widely used in environmental chemistry, clinical virology, the food safety , waste treatment, etc. To our best knowledge, the reported chemosensors have some disadvantages :(1) the crude materials are expensive ; (2) the procedures are troublesome; (3) they are not water solubility,so these disadvantage prevent them from actual applications for Cr³⁺ sensors. Rare-earth (RE) based emitters have some advantage such as can give sharp, narrow emission bands, large sharpen stoke displacement, long excited lifetime and very cheap, if we can use it to detection Cr³⁺ in aqueous solution, it will provide certain theoretical basis for the actual applications to a large extent.In addition ,very few Cr³⁺ fluorescent sensors in aqueous system have been successfully designed so far.First: Tow water soluble rare-earth (Ⅲ) fluorescent chemosensors of Na₃RE(PDA)₃ (PDA = pyridine-2,6-dicarboxylic acid; RE = Eu, Tb,) have been synthesized and characterized by UV/Vis absorption, elemental analysis, and fluorescence spectra. It is observed that their emission intensity and excited state lifetimes decrease with increasing concentration of trivalent chromium (Cr³⁺). Their sensing behavior towards Cr³⁺ is investigated by fluorescence spectroscopy. Results suggest that Na₃Tb(PDA)₃ exhibits the highest sensitivity and linear spectral response towards Cr³⁺ (Stern-Volmer constant = 0.829×10⁶ L/mol, linearity = 0.989). These important advantages make themselves promising candidates to be utilized in actual applications.Second: We tried to put center rare earth ions replaced by Sm and Dy, and conducted a series of tests and characterization.Then we obtained the similar conclusion, but the two complexes's detect limit is lower than Eu and Tb complexes .we speculate the reasons may be is the difference of central ions.