Amino Acid Substitution Aggregate Induces Luminescent Molecular Surface/Interface Assembly

Aggregation induced emission(AIE)refers to the property that molecules have weak or non luminescence in the diluted solution,but their luminescence is several tens or hundreds time enhanced in the aggregation state.In this thesis,we study the self-assembling behaviors of several types of chiral AIE molecules by using atomic force microscopy(AFM),scanning electron microscope(SEM),transmission electron microscopy(TEM)and fluorescence microscope.We systematically study their self-assemblies induced by poor solvent on different surface/interface.We study the self-assemblies of TPE-Valine and TPE-2Valine,which contain tetraphenyl ethylene scaffold modified with single and double Valine substitute,respectively.It is found that upon the addition of poor solvent TPE-Valine self-assembles into helical fibers and more helical fibers are formed at the higher ratio of poor solvent.AFM reveals that along with helical fibers,there are also combined film with fibers,with the film to be wrapped into helical fibers,which shows an important clue about the formation of the helical fibers.While TPE-Valine and TPE-2Valine formed similar helical fibers upon the addition of poor solvent.With LB technique the assemblies of TPE-Valine and TPE-2Valine on air/water interface are also studied.On the air/water interface,at surface pressure from low to high value,short rods and laminar consisting of fibers are formed,respectively.They do not show characteristic helicity previously observed on mica.While TPE-2Valine forms networks which also lose the characteristic helicity in the assemblies on mica.The great difference of the assemblies of TPE-Valine and TPE-2Valine on mica and on air/water surface is related with the different property of the surface/interface.The water surface is more polar than that of mica,so the amphiphilic molecules would adjust their conformation to minimize their contact with water molecules.The adjustment of molecules on water surface also destroys the hydrogen bonds of molecules,which is critical for the formation of helical fibers.The self-assembling behaviors of silole containing leucine attachments are also studied.It also shows diverse morphologies on mica and on water surface.They formed helical fibers upon the addition of poor solvent.On air/water interface,they are less compressible due to the rigidity of the molecules and they form compact networks which also lose characteristic helicity on mica.To further confirm the critical role of the surface interface,3-aminopropyl triethoxysilane(APTES)modified mica and graphite are also chosen as the substrate to study the self-assembling behaviors of the above molecules.TPE-Valine forms the assemblies of laminar on APTES modified mica and formed compact helical fibers on the surface of graphite.It further confirms the influence of the polarity of substrate on the assemblies of molecules.