Sythesis And Characterization Of Water-soluble Near-Infared AIS/ZnS Quantum Dots

Ternary I-III-VI₂ semiconductor nanocrystals,also known as quantum dots?QDs?,have received extensive studies in recent years due to their unique photoelectric effect.These types of I-III-VI₂ QDs have shown trenmendous promise for applications in biological imaging,LED and soalr cells because of their excellent optical properties,such as good biocompatibility and photostability.Among I-III-VI₂ QDs,AIS is a promising substitute for toxic binary QDs,which attributed to their large absorption coefficients in visible and near-infrared region,long photoluminescence?PL?lifetimes and low toxicity.The synthesis methods of AIS QDs mainly include thermal injection and single-source precursor methods.However,these methods are mostly carried out in the high temperature organic phase and the reaction process is complicated,the resulted QDs are difficult to be further applied to biological imaging because of their hydrophobicity.Although the surface can be modified to make QDs water-soluble,it is difficult to operate and likely to reduce the luminescent properties of QDs.Aqueous phase method has the advantages of simple operation,green and excellent water-solubility compared to organic phase method.So far,there is only a small literature on derectly synthesizing water-soluble NIR AIS/ZnS QDs in aqueous phase.Based on this cognition,this thesis aimed at synthesizing water-soluble NIR AIS/ZnS QDs in aqueous phase using different thiol ligands.The main research contents are as follows.1.NIR AIS QDs was firstly synthesized at 80?in an aqueous solution using D-pen as thiol ligand,AgNO₃ and In?NO?₃ as cationic metal precursor and TAA as sulfur source.Experimental variables such as temperature?the amount of D-Pen and TAA,the ratio of Ag/In and pH value was studied and the the optimum condition was pH=8.00,n_D-Pen:n_AgNO3:n_In?NO3?3:n_TAA=4:1:1:0.6.UV-Vis and PL spectrum showed AIS QDs had large stokes shift?410 nm?and can emit in NIR region.XRD results showed AIS QDs were orthorhombic crystals.TEM results showed were well-dispersed and had a near-spherical shape with 4 nm in average size.Furthermore,the AIS/ZnS QDs were synthesized to obtain desirable fluorescence properties.The PL intensity of AIS/ZnS QDs was three three times as high as AIS QDs and PL lifetime was increased from 10.67ìs to 11.48ìs.2.TP was selected as surface ligands to synthesize AIS QDs at 60?in aqueous solution by a one pot method.Cationic metal precursor and sulfur source used in this experiment was the same as D-Pen capped AIS QDs.The optimum condition was pH=7.03,n_TP:n_AgNO3:n_In?NO3?3:n_TAA=4:1:1:1.The emission wavelength for TP capped AIS QDs can be tuned from 838nm to 898 nm.Zeta potential of prepared TP capped AIS QDs was-28.77 mV,which showed that the system was stable.After coating with 0.3 g gelatin and ZnS shell,The stability and fluorescence properties of TP capped AIS QDs were obviously improved.TEM results showed AIS/ZnS QDs was uniformly dispersed in aqueous solution and the average partical size was 4.9 nm.XRD patterns showed AIS/ZnS QDs orthorhombic crystal structure.3.The interaction between AIS QDs and BSA was thoroughly investigated using D-Pen capped AIS QDs as quantum dot system and BSA protein model.In this experiment,the impact of the amount of BSA,p H of the buffer solution and external temperature on AIS-BSA systems was discussed by UV-Vis and fluorescence spectrometry respectively to studied the mechanism of interaction between AIS and BSA.The characterization results showed the modification of BSA can improve the PL intensity of AIS QDs,the effect of the buffer solution on the AIS-BSA system was codetermined by the BSA and the pH of the buffer solution.Low temperature conditions helped to promote the interaction between BSA and AIS and made the system more stable.