Preparation And Band Gap Engineering Of Gel/PbI₂ Single-crystal Composites

Drawing inspiration from single-crystal composites of biominerals in nature,increasingly bio-inspired single-crystal composites have been synthesized.These materials combine the long-range order(single-crystallinity)and composite structures with bulk contact inside single-crystal.3D continuous network guest can be incorporated into single-crystal host using gel method to grow crystals,introducing bicontinuous interpenetrating network structures inside single-crystal.Aiming at functionalization and application of the single-crystal composites,efforts have been made to adopt the semiconductor single-crystals.However,limited efforts have been made to in-depth investigate the property of these semiconductor single-crystal,especially gel/semiconductor single-crystal owing bicontinuous structures.Furthermore,current works have not yet exceeded the limitations of insulator gel guest which cannot form the heterostructures owing excellent photoelectric performance with semiconductor single-crystal host.It will take a big leap forward for application of these single-crystal composites,if gel guest could be made into semiconductor.In this thesis,we focus on property research and structure design of gel/semiconductor single-crystal towards functionalization and carry out a series of work.In chapter 1,the current research status of single-crystal composites in nature and synthesized in recent years is firstly introduced,and the research progress of gel/semiconductor single-crystal is especially presented.Then,the efforts and attempts for functionalization of single-crystal composites are reviewed.In chapter 2,the influence on photoelectric property of semiconductor single-crystal after gel incorporation is in-depth investigated,taking PbI2 single-crystal as a model.Here,PbI2/gel single-crystal composites have been successfully prepared.Diffuse Reflectance Spectra(DRS)show a clear increase of band gap of PbI2 after gel incorporation.The band gap is further increased through expanding the area of host/guest interfaces or enhancing the interatomic forces at the interfaces.The electrostatic interaction at host/guest interfaces are attributed to this band gap shift.As such,this work provides a novel and facile way for band gap engineering by gel incorporation.In chapter 3,TiO2 semiconductor were made into gel forms by sol-gel method,and the band structure was measured with,the help of Ultraviolet Photoelectron Spectrometer(UPS)and DRS.After the optimization of gel-medium environment,TiO2 gel incorporated PbI2 semiconductor single-crystals with hexagonal and star-like shape were obtained using gel method to grow PhI2 single-crystal.