Synthesis And Properties Of Water-soluble Nano-heterostructures

Nano heterostructure (NHS) refers to the combination of multiple nano unitsas one entity. NHS integrates the functionalities of every unit. More intrigueingly, themass and energy flow through the interface between different sub-units, wouldmodulate the electronic ensemble property, realizing novel functionalities. Afterliterature review, we found that there are still a lot of spaces in the field of rationaldesign of NHS. Several challenging issues need to be tackled right now:1.Size-controlled and monodisperse NPs in NHS is necessary for interrogation ofstructure-property relationship. Besides, in-situ monitoring is also crucial to theunderstanding of the band structure in reaction environment.2. Although progresseshave been achieved in the synthesis of various NHS, the library of NHS need to beextended based on in-depth understanding in the interfacial bonding and electronicmodulation. For example,2D nanomaterial is less investigated as construction untis.While randomly deposited NHS based on2D materials have been reported, fine controlon the size, shape and deposition site is still in its infant stage.This thesis focuses on three main topics. The first part is on the generalsynthesis of high-quality metal, metal alloy and semiconductor nanocrystals,such as Au, Pd, Pt, PdCu, PtCu, CdS, Bi2S3, AgBiS2and CdSe, in the foramidesolvent. The produts are of high crystallinity, uniform size and can be dispersedin water for further applications. The second part is on catalytic Pd-Fe2O3NHS.We adopt the aformentioned formamide solvent to successfully synthesizemonodisperse Pd-Fe2O3NHS and control the size of Palladium in a wide range.Using this well-defined model catalyst, we study the Suzuki coupling reactionand investigate the structure-property relationship. The catalyst catalyzes thecoupling between bromobenzene and bezene boronic acid under roomtemperature in aqeous solution. The comparison between the electronic structurein vacuum and that in liquid conditions indicates that in-situ characterization iscrucial. The third part lies in the synthesis of novel NHSs.2D nanomaterial is arising star in nano science in recent years. However,2D-NHS usually deals withrandom deposition of a foreign speicies on2D substrates. Controlled deposition of the second unit on required facets or sites is achieved through in-depthunderstanding the interfacial bonding assisted by DFT calculation.2DBi2Se3-0D CdS and1D CdS-2D ZnIn2S4NHSs with controlled orientation andcomposition were obtained. Their functionalities in the field of solar energyconversion were also investigated. Theoretical modeling also indicates the newelectronic states arsing from the inorganic interface.This dissertation combines experimental and theoretical study on thesynthesis, growth mechanism, functionality and structure-property relationshipof the NHSs. This rational design would be instructive for the development offuture and novel NHSs.