Preparation Of Rare Earth-based Layered Double Hydroxides Nanomaterials And Detection Of Bacillus Anthracis Biomarkers

Lanthanide rare earth ions(Ln³⁺)possess unique luminescent properties such as strong and narrow emission peak bands,large Stokes shifts and long fluorescence lifetimes.The f-f leap absorption efficiency of rare earth ions is low,and the antenna ligands,which are strong absorbers,can transfer energy to the rare earth ions,thus sensitizing them to emit characteristic emission light.However,disadvantages such as poor photothermal stability and low mechanical strength of rare-earth complexes limit their practical applications.Combining nanomaterials as substrates with rare earths to prepare rare earth-based nanocomposites can not only retain the excellent properties of nanomaterials and rare earth,but also effectively improve and enhance the stability and optical properties of rare earth complexes,so as to realize the practical application of rare earth functionalised nanocomposites.In this paper,we prepared a series of rare earth based layered double hydroxides（LDHs）composites and investigated their application as novel fluorescent probes for the detection of anthrax spore biomarker 2,6-pyridinedicarboxylic acid（DPA）,in particular,we proposed a strategy of intercalation synergistic coordination to composite organic small molecules with rare earth-based LDHs to successfully construct stable ratiometric DPA fluorescent nanoprobes,and this synthetic strategy provides a new idea for the preparation of novel rare earth functionalized nanocomposites.1.In this chapter,3D microencapsulated rare earth-based LDHs composites were prepared using a facile cation exchange strategy and further applied as a novel fluorescent sensor for monitoring the anthrax biomarker DPA.In our design,3D hollow Ni-Fe-LDHs were first prepared using MIL-88A as a sacrificial template,and then the 3D microencapsulated Ni-Fe-Ln-LDHs composites were finally obtained by ion exchange.Attributed to the prepared porous microcapsule structure Ni-Fe-Ln-LDHs with large specific surface area,homogeneous dispersion and abundant unsaturated coordination sites for rare earth ions,the material exhibited a fast response and low detection limit（4 n M）for the detection of DPA and was successfully applied to the bioassay of bacterial spores.2.In this chapter,L@Mg-Al-Ln-LDHs functional composites were prepared by assembling anionic organic small molecules L with Mg-Al-Ln-LDHs using an intercalation synergistic coordination strategy.The organic small molecule L was firstly designed and synthesized,which showed high sensitivity and strong binding ability to Al³⁺with significantly enhanced fluorescence.The L-Al³⁺complex provided a strong and stable internal reference fluorescence signal due to the limitation and protection of the LDHs framework,and a stable ratiometric fluorescent DPA sensor was successfully constructed with a low detection limit of11.6 n M and 3.56×10³spores/m L in spore samples.The nano-sensing probe was combined with a smartphone to develop a highly sensitive anthrax marker test strip for reliable and rapid monitoring of B.anthracis.The synthetic strategy of intercalation synergistic coordination provided by this research work provides an important design strategy for the development of rare earth-based LDHs nanosensing platforms for monitoring other environmental pollutants.