Study On Synthesis Of Tb³⁺-doped CaAl-LDH And Their Fluorescence Response To Amino Acid Molecules

The present work is about the synthesis and fluorescence property of terbium doped calcium aluminum layered double hydroxides(Tb³⁺-doped CaAl-LDHs),the annealing of Tb³⁺-doped CaAl-LDH,the fluorescence of Tb³⁺-doped CaAl-LDH response to tryptophan and cytosine.The contents are followed as:1.Tb³⁺-doped CaAl-LDHs with different Ca²⁺/(Al³⁺+Tb³⁺)molar ratios have been synthesized in the ethanol/water media by co-precipitation method using CaCl₂,AlCl_3·6H₂O,Tb₂O₃,NaOH,H₂O₂ and HNO₃ as the raw materials,and its structure,composition and fluorescence property have been investigated.Results revealed that the Tb-doped CaAl-LDHs kept the structure of hydrocalumite and exhibited typical emissions ascribed to ⁵D₄?⁷F_J?J=3,4,5,6?transition of Tb³⁺ions.2.The annealing of Tb-doped CaAl-LDH with Ca²⁺/(Al³⁺+Tb³⁺)molar ratio of 2.0was carried out at 200,400,600,800 and 1000oC for two hours.Results suggested that the structure of LDHs kept after annealing at 200oC,then the structure began to collapse at 400oC,further new phase Ca₁₂Al₁₄O₃₂C_l2:Tb³⁺appeared while annealing at 600¹000oC.Moreover,the crystallinity of the Ca₁₂Al₁₄O₃₂C_l2:Tb³⁺was improved and its fluorescence obviously enhanced with increasing temperature.3.The fluorescence of Tb³⁺-doped CaAl-LDH response to tryptophan and cytosine have been examined,respectively.Results indicated that the green emissions attributed to Tb³⁺markedly decreased and even quenched after the Tb³⁺-doped CaAl-LDH reacted with tryptophan,but the structure of LDH retained.With the increase in the concentration of tryptophan solution,some weak new diffraction peaks appeared.These new diffraction peaks may be due to the hybrid of Tb³⁺-doped CaAl-LDH and tryptophan.When the Tb³⁺-doped CaAl-LDH reacted with different concentrations of cytosine,the green emissions of Tb³⁺increased gradually,the structure of LDH did not change much,and no new diffraction peaks occurred.In view of the biocompatibility of Ca²⁺and the fluorescence of Tb³⁺-doped CaAl-LDH response to biological molecules,the Tb³⁺-doped CaAl-LDHs may have latent application in biological probe or medical diagnosis.