Study On Synthesis Of Eu³⁺-doped CaAl-LDH And Its Fluorescence Response To Nucleic Acid Bases Molecule

The work is aimed to study the preparation and fluorescent property of Eu³⁺doped Calcium Aluminum layered double hydroxides(Eu³⁺-doped CaAl-LDH),along with the changes of fluorescence and structure for its thermal treatment samples.Further,the fluorescence of Eu³⁺-doped CaAl-LDH response to cytosine and guanine is investigated.The primary coverage is followed as:1.A series of Eu³⁺-doped CaAl-LDH were prepared in ethanol/water medium by co-precipitation method,and their composition,structure,and fluorescence have been studied.It is found that the actual Ca²⁺/(Al³⁺+Eu³⁺)molar ratios present in the samples are 1.0,2.0,2.0,and 2.3 corresponding to the initial Ca²⁺/(Al³⁺+Eu³⁺)molar ratios of1/1,2/1,3/1,and 4/1,respectively.All the samples exhibit layered structure and belong to monoclinic system.Moreover,strong red emission ascribed to ⁵D₀-⁷F_J?J=1,2?transition of Eu³⁺present in the samples,suggesting the CaAl-LDH host is favorable for the Eu³⁺emission.2.The thermal treatment about the sample with Ca²⁺/(Al³⁺+Eu³⁺)molar ratio of 1.0 is conducted.Result reveals that the layered structure of the sample is destroyed after being thermal treatment at 400°C,then a new cubic phase Ca₁₂Al_14-xEu_xO₃₂Cl₂ forms at 600°C.Further the crystallinity is improved with temperature up to 800 and 1000°C.Compared with the as-prepared sample and other thermally treated samples,the sample thermal treatment at 600°C shows the strongest red emission.3.The fluorescence of the sample response to cytosine and guanine molecules has been studied.Results indicate that the layered structure of Eu³⁺-doped CaAl-LDH does not change as it reacts with cytosine,its basal spacing has increased,which is possibly due to cytosine molecules incorporated into interlayer of LDH.Moreover,the fluorescence of Eu³⁺-doped CaAl-LDH gradually decreases with increasing content of cytosine incorporated in the LDH.The decrease of fluorescence may be related to some hydrogen bonds between the LDH and cytosine.As the Eu³⁺-doped CaAl-LDH reacts with guanine,its basal spacing tends to increase with increasing content of guanine,but its fluorescence firstly decreases and then increases,which is possibly relevant to the guanine molecular association.