Self-assembly And Optoelectronic Properties Of Carnosine Substituted Perylene Diimide Derivative

As one of the n-type organic non-fullerenes semiconductor materials,perylenediimide derivatives(PDIs)have a variety of outstanding advantages such as excellent electron transport capability,high photothermal stability and electron affinity,tunable energy levels and multiple chemical modification sites.They have been widely used in field of frontier technologies,such as organic photovoltaic cells,linear photovoltaic devices,sensors,photo catalysis and thermoelectric materials,and have become one of the most popular organic semiconductor materials in recent years.However,It is difficult to predict the self-assembly behaviour based on the molecular structure,which severely limits the fabrication of micro-and nanomaterials with long-range ordered ?-? stacking upoon different requirements.Thus,in this thesis,the assembly mechanism of a new PDI derivative was thoroughly investigated from the molecular level,as well as the relationship between molecular and self-assembled structures and optoelectronic properties(1)A novel asymmetrically substituted amphiphilic perylene diimide derivative(CUPDI)was designed and synthesised,using hydrophilic L-carnosine(C)substituted at one of the imide positions and the alkyl chain(undecyldodecyl,U)on the other.L-carnos ine is a dipeptide consisting of K?-alanine and L-histidine,where the imidazole ring can act as a donor to construct a D-A molecular structure with the electron-deficient PDI ring.The assembly mechanism of CUPDI was investigated by varying the concentration,solvent and temperature.It was found that the cooperative model could well fit the assembly behaviour of CUPDI.By regulating the balance of hydrogen bonding between carnosine and ?-?interactions between PDI rings,CUPDI nanomaterials with diverse morphologies,such as small spherical aggregates,nanowires with uniform size,nanoribbons and irregular aggregates,were obtained.It was found that nanoribbons showed the highest photocurrent enhancement,while nanowires exhibited the highest photostimulus responsiveness to ammonia,with an increase of up to 7.1 times(2)The self-assembly behaviour of CUPDI in different solvent mixtures was investigated.The effects of solvent composition,solvent polarity,concentration and pH on the self-assembly behaviour of CUPDI in different binary solvent mixtures were studied.The results showed that by adjusting the tetrahydrofuran/water ratio(fTHF)was able to regulate the structural transformation of CUPDI self-assemblies to achieve chiral inversion,and the micro-nano fibres with the most significant chiral features were fabricated at fTHF=0.3 Adjusting pH also induced the chiral inversion of the self-assemblies.The CUPDI micro-nanomaterials fabricated from the tetrahydrofuran/water and tetrahydrofuran/sodium hydroxide aqueous solution exhibited higher photocurrent response.The presence of ammonia could enhance the photocurrent of CUPDI nanomaterials.(3)The effects of Na+,K+and different metal coordination centres(Zn2+,Cu2+and Ni2+)on the self-assembly behaviour of CUPDI were investigated from the perspectives of ionic strength and transition metal coordination.The balance amone different noncovalent bonds such salt effects,coordination bonding,hydrophobic interactions,hydrogen bonding and ?-?stacking was taken into consideration The chiral self-assembly structure of the CUPDI self-assemblies was controlled by a competitive coordination strategy using EDTA to achieve chiral switching control.Using electrochemical characterisations such as CV,the photoelectric properties of the fabricated CUPDI micro-nanomaterials and the photoelectric in response to stimuli were investigated.It was found that the Zn2+/CUPDI binary assemblies,and the CUPDI assemblies obtained from the KCl and NaCl solution/tetrahydrofuran showed higher photoelectric response than that of the system without metal ion,whereas the Cu2+/CUPDI binary assemblies showed weaker photocurrents.The presence of ammonia resulted in significantly enhanced photoelectric conductivity of the CUPDI nanomaterials containing the different metal ions.