Two amphiphilic barbituric acid derivatives with a D-π-A structure, 5-(4-dodecyloxybenzylidene)-(1H,3H)-2,4,6-pyrimidinetrione(PB_ 12) and 5-(4-N,N-didodecylaminobenzylidene)-(1H,3H)-2,4,6-pyrimidintrione(AB_ 12) were found to show different aggregation behavior in chloroform. PB_ 12, a derivative with weak electron donating and strong electron drawing substituents, tends to aggregate in a head-to-tail manner, whereas AB_ 12, a derivative with both strong electron donating and drawing substituents, tends to aggregate in a face-to-face manner at a higher concentration. The cyclic voltammograms of AB_ 12 and PB_ 12 show that their energy levels of LUMO approach each other, however, the energy level of HOMO of AB_ 12 is much higher than that of PB_ 12.
The colloids of ZnO and WO 3 were synthesized and ZnO colloid with different mass fractions was added into the WO 3 colloid to get WO 3/ZnO composite colloids. The experimental results indicate that the UV-light coloration of WO 3 nanoparticles could be improved greatly after the addition of ZnO. When the molar ratio of ZnO to WO 3 is about 1∶100, the magnitude of the difference of absorbance(ΔOD) at 900 nm after and before the coloration for WO 3/ZnO colloids is as about 135 times as that of WO 3 colloids. The surface photovoltaic spectra show that the state density of the surface state of WO 3 increases greatly after the addition of ZnO, thus, under the UV-light irradiation more electrons from ZnO nanoparticles can be captured in the surface state and those electrons can be excited to a higher energy level, resulting in the improved coloration.
The recent progresses on constructing organic nanostructures from the self-assembly of melamine and barbituric acid derivatives are reviewed. By mediating the chemical microenvironment during the self-assembly, the information contained in the molecular components can be expressed at different levels, thus resulting in the formation of different organic nanostructures. When the assembly is carried out in anhydrous chloroform, a kind of asymmetric layered structure with a d value of 4.1 nm is obtained. When a little amount of polar solvent such as alcohol is contained in the chloroform, organic nanotubes with diameter of 6 nm and length of several hundreds of nanometers are observed. After being treated by appropriate polar solvents, the nanotubes are induced into supercoils with diameter of about 300 nm and length of several tens of microns. The sensitivity of the self-assembly process origins from the weak noncovalent intermolecular interactions between the molecular components. The enthalpy change of such interactions is pretty small, so slight change of the molecular structure or microenvironment could affect the primary equilibrium, resulting in the rearrangement and transformation of the supramolecular structure.
