Synthesis,Properties And Application Of Functional Titanium-Oxide Clusters

For photocatalysis and dye-sensitized solar cells(DSSCs),the interface structure of functionalized TiO2 nanoparticles(NPs)plays a key role in the light absorption,photoexcitation,electron transfer and photoreaction.Due to the complexity of binding modes,understanding the precise interfacial structure at an atomic level is a challenge.Previously,many efforts have been made via theory and computational modeling to study the electronic structure of ligand/TiO2 complexs.But there are still some differences between the theoretical models and experimental system.The advantages of titanium oxide clusters(TOCs)as the molecular simulators of TiO2 is that functionalized sites and the precise structure can be characterized by X-ray diffraction.Therefore,TOCs can be used to simulate the binding modes of ligands on the surface of TiO2 to obtain the interface structure,electronic structure and photochemical reaction mechanism of the ligand/TiO2 complexs,which provides a new way for the mechanism research and performance improvement of photocatalysis and DSSC.In this thesis,we synthesized a series of functionalized TOCs and obtained interface and electronic structure information of the TOCs by X-ray diffraction combining DFT calculation.We studied the reactivity of ligand exchange of TOCs by Raman spectroscopy and stopped-flow kinetics.Finally,we studied surface-enhanced Raman scattering(SERS)of phenols and catechols by TOCs.This thesis is divided into the following four parts:In Chapter ?,we reviewed the development of synthesis and research progress of functionalized TOCs including surface functionalized TOCs,host-guest TOCs and Ti-MOFs.Meanwhile,we summarized the interfacial structure,electron structure and charge transfer properties of functionalized TOCs.Finally,we expounded the scientific significance of this thesisIn Chapter ?,salicylic acid(SA)functionalized TiO2 show more extensive visible light absorption and better photocatalytic performance.The SA is a highly efficient anchoring group of DSSC.The study of SA-functionalized TOCs as molecular analogue of ligand/TiO2 complexs is rare.We synthesized several SA-functionalized TOCs determining the molecular structure by X-ray diffraction,and further reviewed the binding modes of the SAs.We analyzed the contribution of SAs to the front frontier orbitals and absorption onsets of TOCs by using DFT calculations based on the molecular geometries determined by X-ray diffraction.Finally,we compared the similarities and differences in structure and properties of SAs/TOCs and SAs/TiO2.In Chapter ?,we studied the surface modification of[Ti17]and synthesized a series of functionalized[Ti17]containing different numbers of catechols.We expounded reactivity,binding modes of sites and obtained the kinetic parameters of ligand exchange.The current findings are helpful for the assembly of organic-inorganic hybrid materials,as well as the understanding of the structure and reactivity of TiO2 surface sites.In Chapter ?,SERS is a highly surface-sensitive approach suitable for studying the binding modes of ligand on the surface of NPs.However,the complex structures of TiO2 NPs bring about many difficulties to correlate the SERS signals with the binding modes.We prepared a superhydrophobic porous[Ti17]film in a very simple way and studied SERS of phenols.We found that[Ti17]film shows much more intense Raman signals than TiO2 film.According to the X-ray diffraction analysis and DFT calculation,we assigned the SERS peak and quantitative analysied the contribution of focusing effect,CHEM effect and resonance mechanism for the higher SERS activity of[Ti17]The conclusion indicates that TOCs may have application potential in SERS detection of phenols and catechols,and it can be used to study the SERS signal assignments,binding modes and SERS mechanism of TiO2 NPs.