Synthesis Of Manganese Oxides And Cadmium Telluride Quantum Dots Dual-Mode Composites

Recent research has shown that the pathogenesis of some diseases is closely related to concentration variety of certain small molecules in the body,therefore it is important to establish methods for these small molecule detections.Magnetic resonance and fluorescence dual-mode imaging probe with both the advantages of high sensitivity and high spatial resolution,could realize real-time,in situ and dynamic imaging,which could enhance the ability to identify and diagnose diseases,and is very suitable for the small molecular detection.The synthesis of MRI/fluorescence dual-mode imaging materials has become an active area of research,of which core elements is imaging materials with good biocompatibility,excellent imaging performance,high stability,controlled size and shape.In this thesis,two dual-mode MRI/fluorescence imaging have been successfully synthesized.Material 1.The MnO₂/BSA/CdTe quantum dot complex（MnBQ）is obtained by synthesizing CdTe quantum dots and BSA-modified MnO₂ nanosheets,respectively,and then doped the CdTe quantum dots on the nanosheets via the carboxylamine reaction.Transmission electron microscopy（TEM）results show that the synthesis materials have good dispersion and the morphology,which are flat 2D nanosheets with a diameter of about 200 nm.High-resolution TEM indicates that CdTe quantum dots and MnO₂ are scattered in MnBQ,which is consistent with the results obtained by XRD and XPS.In addition,the results of magnetic resonance imaging and fluorescence spectra results show that the synthesized materials have good magnetic resonance/fluorescence dual-mode imaging properties.The imaging properties of the materials are further improved by optimising the experimental conditions,and circular dichroism has been used to explore conformation of BSA during the synthesis process.Cytotoxicity and imaging experiments shown that the synthesized MnBQ have low toxicity,good biocompatibility,and good fluorescence imaging performance.Then MnBQ is used as a ratiometric fluorescence-T₁MR dual-mode sensor for quantitative analysis of H₂O₂ and Fe³⁺,and the mechanism are discussed in detail.The lowest limit detection for H₂O₂ is 2.841μmol/L（fluorescence）and 43.85μmol/L（MRI）.The lowest limit detection for Fe³⁺is 0.7004 nmol/L（fluorescence）and 0.2642 mmol/L（MRI）,which could be used for quantitative analysis of H₂O₂ and Fe³⁺in serum,and showed good selectivity and recovery in real sample detections.Material 2.Mn₃O₄/GSH/CdTe quantum dot complexes（MGQ）have been synthesized by a one-pot method.In this reaction glutathione is the reducing agent for the synthesis of Mn₃O₄,the carrier for the loading of manganese oxides and CdTe quantum dots,and the adsorbent for the adsorption of target molecules in the probe system.Transmission electron microscopy results show that the synthesis material is an irregular sheet-like structure.High-resolution transmission electron microscopy,XRD and XPS results demonstrate that Mn₃O₄ and CdTe quantum dots are dispersed on the nanosheets of the complex.Magnetic resonance imaging and fluorescence spectra results show that the synthesized materials have good MRI/fluorescence dual-mode imaging properties.Since phosphoric acid can generate Mn²⁺with Mn₃O₄,and Mn²⁺can generate manganese carboxylate complexes with the carboxylic acid on the quantum dots,which would induce a static quenching progress of CdTe quantum dots.There is a good linear relationship between the concentrations of phosphoric acid and fluorescence intensity varieties of CdTe quantum dots.The lowest limit detection for H₃PO₄ detection is 0.1608 nmol/L（fluorescence）and0.02006 mol/L（MRI）,which can be used for the quantitative analysis of phosphoric acid concentrations in real samples.