Designed Synthesis Of Amphiphilic Perylene Tetracarboxylic Diimides (PDI) Template Molecules And Properties Of Organic/inorganic Self-assembly System Of PDI/CdS(ZnS)

Facile approaches to fabricate semiconductor nanostructures have attracted scientistsfrom different fields. Semiconductor nanomaterials can often display unique optical,electronic, and magnetic properties, whereas these properties strongly depend on the size andshape of the nanoparticles. As a result, synthetic control over the morphology, size andcrystallographic orientation of materials is highly desired. Among the methods for thepreparation of nanoscale materials, growing of inorganic structures directly on organictemplates by controlled modification of interfaces has recently emerged as a powerfultechnique. We discussed the interaction of PDI and inorganic component among hybridsystem and researched its impact on optical, electronic properties of hybrid system. Ourresearch work has been mainly focused on the following three respects:1. Controlled Preparation of CdS Nanoparticle Arrays in Amphiphilic PeryleneTetracarboxylic Diimides: Organization, Electron-Transfer and Semiconducting PropertiesLangmuir monolayers of two amphiphilic perylene tetracarboxylic diimide (PDI)derivatives, PDI-1and PDI-2, which are modified with different number of hydrophilicpolyoxyethylene/hydrophobic alkoxy side-chains, have been used as not only the organictemplates but also the good functional organic materials to produce the first examples of rose-and petal-like nano-particle arrays of cadmium sulfide (CdS)-PDI composites with acontrollable and tunable size (from40,60to80nm for nano-roses; from20to30nm fornano-petals), respectively. These newly fabricated CdS-PDI hybrid nanostructures werecomparatively studied by a wide range of methods including SEM, TEM technique, electronicabsorption, fluorescence emission and X-ray diffraction analysis. The crystalline regions forCdS were identified to be hexagonal wurtzite with (101) and (001) face preferred growth onthe PDI-1and PDI-2monolayer, respectively, associated with the polyoxyethylene sidechains architecture changing from paralleling to the subphase surface for PDI-1toperpendicular to the subphase surface for PDI-2. Furthermore, electron-transfer from PDImolecules to CdS nanocrystals is established by both quenching of photoluminescenceintensity and changing of the lifetime of photoluminescence emission of PDI in the hybrid nanoparticle arrays. In particular, a significantly enhanced conductivity for both nano-rosesand nano-petals of CdS-PDI nanocomposites was achieved, relative to that of the eachindividual component, due to the existence of the densely packed molecular architecture inthe film matrix and the large interfacial area between the two components that removed thecharge transporting bottleneck by creating an interpenetrating network of the hybrid materials,implying the potential of providing synergetic semiconducting properties of the present hybridorganic-inorganic nanomaterials.2. Self-Assemble, Electron-Transfer and Transformational Thin-Film TransistorProperties of ZnS/Amphiphilic Perylene Tetracarboxylic Diimides Nanocomposite ArraysLangmuir monolayers of two amphiphilic perylene tetracarboxylic diimide (PDI)derivatives, PDI-OH and PDI-2OH, which are modified with different number of hydrophilicaminoethanol/hydrophobic hexyl side-chains, have been used as not only the organictemplates but also the good functional organic materials to produce the unique zinc sulfide(ZnS)/PDI hybrid nanoparticles with a diameter of ca.15nm for either ZnS/PDI-OH orZnS/PDI-2OH hybrid materials. These ZnS/PDI hybrid nanostructures were comparativelystudied by a wide range of methods including SEM, HRTEM technique, electronic absorption,fluorescence emission and X-ray diffraction analysis. The crystalline regions for ZnS wereidentified to be cubic sphalerite and hexagonal wurtzite with (111) and (002) face preferredgrowth on the PDI-OH and PDI-2OH monolayer, respectively, associated with the number ofthe aminoethanol side chains architecture resulting in perpendicular to the subphase surfacefor PDI-OH and PDI-2OH to varying degrees. Furthermore, electron-transfer from PDImolecules to ZnS nanocrystals is established by both quenching of photoluminescenceintensity and changing of the lifetime of photoluminescence emission of PDI in the hybridnanoparticle arrays. The electron mobilities as high as0.018and0.023cm2V-1s-1areachieved for ZnS/PDI-OH and ZnS/PDI-2OH hybrids fabricated freshly, respectively.However, hole mobilities of about0.010cm2V-1s-1are obtained for both ZnS/PDI-basedTFTs after exposure to air for more than30days. Interestingly, n-type TFT behavior wasrecovered again with a significantly enhanced electron mobility of0.13cm2V-1s-1forZnS/PDI-OH and0.081cm2V-1s-1for ZnS/PDI-2OH hybrids upon exposure to UV-light. Asa consequence, a transformation of semiconducting nature from n-type to p-type and then n-type is realized successfully, which is attributed to both the energy band bending ofheterojunction and a process of adsorbing-desorbing of O2molecules at the interface betweenZnS and PDI components of ZnS/PDI hybrids.3. A Facile Method to Preparation of Amphiphilic Perylene Tetracarboxylic Diimide/ZnSHybrid Nanocomposites and Improved Semiconducting PropertyA self-assembled film of an amphiphilic perylene tetracarboxylic diimide derivative(N-hexane-N’-(1-phenyl-4-aminoethanol)-1,7-di(4-tert-butylphenoxy)perylene-3,4;9,10-tetracarboxylate diimide, PDI-OH) has been used as the organic template to produce the firstexample of monodispersed nano-particles of PDI-OH/ZnS composites. The PDI-OH purefilm and PDI-OH/ZnS nanocomposites were characterized by UV-vis absorption, X-raydiffraction (XRD), scanning electron microscopy (SEM) and current-voltage (I-V)measurements. Experimental results revealed the film crystallinity and general molecularorder for PDI-OH molecules in the nanocomposites are improved effectively in comparisonwith those in the pure film due to the introduction of ZnS nanocrystals. The electricalconductivity of the PDI-OH/ZnS nanocomposites (6.6×10-5S·cm-1) is more than ca.2orderof magnitude higher than that of (3.6×10-7S·cm-1). The present result provides an efficientway to improve the performance of organic semiconductors through introducing inorganicsemiconducting nanocrystals.