Synthesis of Janus Hybrid Nanoparticles as Colloidal Amphiphiles

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TECHNICAL SUMMARY: The synthesis, assembly and polymerization of a new class of hybrid colloids composed of asymmetric nanorods with disparate colloidal components and differentially functionalized polymer ligands will be pursued. These types of hybrid colloids will exhibit Janus-type structural character, as the inorganic colloidal phase will be composed of a single semiconductor nanorod (based on CdSe@CdS) conjugated to a single dipolar cobalt nanoparticle (CoNP). Furthermore, the controllable functionalization of CdSe@CdS nanorod and CoNP surfaces with (co)polymeric ligands will be achieved. This Janus nanoparticle is a novel and unique platform that enables selective and differential functionalization of CoNP and CdSe@CdS nanorod surfaces with different types of polymeric ligands made from controlled radical polymerizations of varying hydrophilicity enabling creation of colloidal amphiphilic nanomaterials. The synthesis and structural variation of colloidal and polymeric components will be the central focus of the research that will enable further studies on the assembly of these Janus NPs and conversion via colloidal polymerization into heterostructured photocatalytic materials. The PI will investigate the self-organization of these amphiphilic Janus NP in solution and at oil-water interfaces to form various colloidal assemblies targeting the formation of linear NP chains with nanorods laterally oriented. Oxidation of the metallic CoNP phases of the Janus NP colloidal assemblies will then be conducted to afford cobalt oxide nanowires carrying CdSe@CdS nanorod side chains along every repeating unit of the cobalt oxide backbone. This methodology affords a route to spatially and electronically ordered p-n semiconductor junctions that are energetically aligned for photocatalysis. The composition, morphology, and electronic structure of these nanomaterials will be investigated via TEM, XRD, photoelectron and optical spectroscopies, along with photocatalysis studies with Janus NP colloidal assemblies and solution optical probe molecules upon irradiation. NON-TECHNICAL SUMMARY:The proposed research aims to develop new methods to prepare novel materials that combine organic polymers and inorganic particles with control of size, shape and function of the different components. This will require the development of new synthetic chemistry to prepare these types of inorganic particles that will be very small in size (i.e., nanoscopic) and decorated with a shell of organic polymer ligands as a plastic coating. Because these types of building blocks are very novel, methods to prepare and hybridize these into a single useful material are lacking, which the proposed research aims to address. Hence, the research is highly interdisciplinary, but grounded in basic and fundamental polymer science. Upon development of these synthetic methods, the preparation of asymmetric nanoparticles will enable evaluation of these materials for energy related problems, such as, photocatalytic generation of hydrogen from water. Furthermore, integration of the research with educational activities with K-12 students will be achieved by joint mentoring projects and a series of lectures given by the PI. Collaborations with South Korean academic institutions (Seoul National University) will also be integrated into this project through joint technical research and educational activities.