| Colloidal systems are dispersed systems driven by intermolecular forces,containing microemulsion,foam,gel et al..There exist abundant micro structures with nano size in these systems,and the component molecules usually have good surface activity and could adsorb on the surface or interface of nano-particles,thereby not only could be used as micro reaction container but also possessing colloidal dispersion capabilities of nano materials.These characteristics made colloids system the prospective template for nano-particle synthesis.Quantum dots(QDs)are three-dimensional quantum confined nanomaterials,which have good application prospects in many fields,such as photoelectric devices,biological imaging,environmental sensing,and photocatalysis based on the special nano effects and good photoelectric properties,among which the ?-?semiconductor QDs should be the most widely studied QDs,because of the excellent luminous property with luminescence coverage from ultraviolet to visible light area.The organic and water phase synthesis methods are commonly used in the preparation of quantum dots,which are commonly proceeded at high temperature.While it was found that the preparation of QDs through colloidal systems such as microemulsion could be realized under mild conditions.Therefore the colloidal preparation methods of QDs have attractted much more attentions.Surface modification of QDs through colloidal methods was usually used for the purpose to realize the solubility,dispersion or functionalization requirements in applications,in which colloidal molecules play an important role.In addition,the construction of QDs hybrid materials was also a common way now for achieving functionalization of QDs,and QDs-gel composites have attracted increasing attention due to the integrative properties of the fluorescence capability from QDs and the flexibility and porosity from the gel.In most existing researches,both the surface modification approaches and the formation of the hybrid materials were realized through ex-situ ways after the synthesis of QDs were completed,which actually induced the complexity of the functionalization process and the extra consume of the agents,having become a bottle neck limiting the efficient application of QDs.Thus the realization of synthesis and functionalization of QDs in an integrative way is a subject which deserves exploring.Based on the knowledge provided by the existing researches about QDs synthesis and the advantages of colloidal templates methods,we explored the novel appraoches to prepare CdS QDs through colloidal templates,containing gel,foam,and microemulison,which were all constructed using environmental-friendly surfactants and polymer.The structural characteristics of these colloidal templates and the microscopic mechanisms in preparation and functionalization of QDs were discussed.The main contents of this paper were listed as below.(1)Based on the understanding of the gelation process of sodium alginate(SA)induced by multivalent metal ions,a two-step gelation method was designed,through which the SA/S2-gel was firstly formed with S precursor being encapsulated into the SA gel.Then CdS QDs were synthesized by immersing the SA/S2" gel balls into the solutions containing Cd2+.The control to the growth of the formed QDs was attributed to the "anchoring" combing interaction between the negatively charged groups of SA with Cd2+and the restriction to the encounter of the Cd2+and S2-precusors through the gel network.It was found that the controlled performance on the growth of the QDs in this method was not affected by the variation in temperature,precursor concentration and the reaction time.It was also found that the synthesized CdS QDs could be modified by SA,and showed pH sensitivity,Fe3+ detectability and good biological compatibility.Thus the two-step gelation method provided a smart integrative way for realization the preparation,dispersion,stabilization and functionalization of QDs,which shows good prospect in environment sensing and biology imaging.(2)The capability and mechanisms for carrying the functional components by foam films through the interafacial co-adsorption phenomenon was studied,and the mechanisms were used in exploring new QDs synthesis approach through solid foam template.It was found that,in the SDS foam system,various organic molecules and inorganic cations could be carried by foam films through co-adsorbing with SDS at the gas-water interface.Through combination of the experimental and simulation methods,the relationship between the molecular adsorption behavior and the foam performance was understood,which hinted the possibility not only realize the regulation to foam property but also regulate the release of coadsorbed functional components.Based on the understanding about the carrying effect to the functional component ensured by the co-adsorption phenomenon,we prepared SDS/SA solid foam containing Cd precursors,in which CdS QDs were synthesized afterwards.By using this foam template,the preparation of quantum dot-solid porous media composites with bright application prospect is innovatively realized.(3)The alkanolamide surfactant CDEA was chosen to construct microemulsion,which was used as medium to achieve controllable synthesis of CdS QDs.Through orthogonal test,the components proportion and the size distribution of the prepared microemulsions were explored.Through comparison the CdS QDs got using this method with that prepared using the microemulsion constructed by traditional surfactant CTAB,the CdS QDs synthesised using CDEA microemulsion had smaller size and a more uniform size distribution,which indicated the advantage from the good passivation effect on QDs might through the amine groups of CDEA.This strategy might enrich the selection options of microemulsion which could be used to product quantum dots and could provide reference significance for improving the performance of quantum dots prepared by microemulsion method.(4)Based on the learning about the preparation process of CdS-SA through the two-step gelation method,the possibility using this process to achieve the adsorption of heavy metal ions and then further utilizing the produced CdS-SA gel in the photocatalysis degradation of organic dye contamination were explored.It was found that the removal efficiency of heavy metal ions by the SA gel was improved through encapsulation of S2-in the SA gel.And the formed SA/S2-gel showed higher adsorption ability Pb2+ in Cd2+-Pb2+ mixed solution.The effects on the adsorption efficiency of the metal cations induced by the pre-gelation time,the metal ions concentration,the pH of the solution and the gel ball size were discussed,which provided useful references for the promotion of the application.The formed SA/S2gel with S2-encapsulated in could not only improve the removal efficiency of metal ions,but also induce the formation of CdS and PbS QDs,solve the reuse problem of the adsorbed metal ions.What is more,the prepared CdS QDs-SA hybrid gel could be used as photocatalysisor and actually showed good action in the the degradation of the organic dyes contamination in polluted water.Through this two-step gelation method,the recovery and utilization of the heavy metal ions after adsorption were realized,also providing a comprehensive way for removal of inorganic and organic contaminations in polluted water.To sum up,this paper comprehensively discussed the application of alginate gel,SDS/alginate foam and alkanolamide microemulsion in the controlled synthesis and functionalization of CdS QDs.In the SA-based gel system,the functionalization modification and the synthesis of QDs was realized in an integrative way.The two-step gelation step used for CdS-SA QDs preparation showed high efficiency in removal of heavy metal ions,and the produced CdS-SA QDs composite showed efficiency in photocatalysis degradation of organic dyes,which provided an integrative way for the removal of the inorganic heavy metal cations and organic dyes in polluted water.These colloidal systems used in the processes were composed of environmental-friendly agents,providing a reference for the greenization of the QDs preparation technology,and theoretic guidance for simplifying the functionalization approach of QDs. |
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