Interfacial Modification Of Carbon Nitride And Photoelectrochemical Sensing Application

In the era of advocating sustainable development,it is urgent to find environmentally friendly,clean and resource-rich energy.Solar energy,as the source of nourishing everything,is the most abundant clean resource on the planet.Therefore,how to use solar energy efficiently becomes the focus of scientific community.Photoelectrochemical(PEC)processes,in which,optical signal is converted into electrical signal,plays an important role in the realization of molecular detection and pollutant degradation by solar energy.As a new material of mental-free conjugated polymer,carbon nitride(CN)has drawn increasing attention in the application of PEC biosensing.However,the bulk carbon nitride has a low surface area and severe recombination of photo-generated carriers,becoming a great challenge in improving the photoelectric efficiency.Due to the large specific surface area,two-dimensional carbon nitride nanosheets(CNNS)can accelerate the transport of carriers and improve the PEC response.However,the ultrasonication-assisted mechanical exfoliation of bulk carbon need a long preparation time and/or may cause a damage to carbon nitride structure.In addition,carbon nitride nanosheets only response to ultraviolet light and very limited visible light(λ<460 nm),limiting its application in biosensing.It is because the short-wavelength lights are ready to generate reactive oxygen-containing species(ROS),causing DNA mutation,protein denaturation,cell damage,and also cannot pass through tissue,making future in vivo applications challenging.Therefore,this thesis aims to explore a fast and efficient method for exfoliating carbon nitride and sensitizing carbon nitride nanosheets so that it can be used for PEC biosensing under red light.The main research contents are summarized as follows:(1)The ball-milling method was used to grind the bulk carbon nitride and copper phthalocyanine(TsCuPc).Due to the constant "shearing force",the van der Waals force between the carbon nitride layers was weakened and exfoliated into thinner layers.Meanwhile,TsCuPc rapidly attached to the surface of CN by the "linkage" of non-covalent(π-π)interaction.In this manner,few-layered CN could be stabilized against agglomeration owning to the sulfonic acid groups that,as part of TsCuPc,induce repulsive forces among them.moreover,a substrate-antenna molecular model which capable to absorb red light(λ>630 nm)efficiently was formed.(2)The optical properties of CN were modified by coupling antenna molecules via donor-acceptor(D-A)interaction for highly sensitive and selective PEC biosensing under red light(λ>630 nm).CNNS-TsCuPc nanocomposites were formed by non-covalently forces.TsCuPc can be excited and generate photoelectrons under red light irradiation,forming an effective D-A system with CNNS.Because of effective photosensitization and D-A interaction,compared to each individual counterpart,the as prepared CNNS-TsCuPc demonstrated much improved photocurrent under red-light irradiation,highly sensitive and selective detection of dopamine(DA)by photoelectrochemistry biosensing.