The Synthesis Of Semiconductor Nanomaterials From The Aqueous Systems Of Divalent Metal Dodecyl Sulfate

Divalent metal dodecyl sulfate is a type of anionic surfactants with amphiphilic structures.The hydrophobic interaction of pendent hydrocarbon chains adsorbed onto the surface of nanoparticles can prohibit the aggregation of inorganic nanoparticles, which can control the size and/or morphology of nanoparticles in the fabrication processes.Moreover,it is also used as a special metal-ion source.In this thesis,CuO, Cu₂O and ZnO semiconductor nanoparticles were successfully obtained from the aqueous systems of these divalent metal dodecyl sulfates,respectively.Meanwhile, the structure and morphology of obtained nanoparticles were characterized by transition electron microscopy(TEM),scanning electron microscopy(SEM),X-ray diffraction(XRD),thermogravimetric analysis(TGA),and etc.The possible formation mechanisms were also postulated.The main results of this thesis were summarized,listed as following:(1) The synthesized surfactant of copper dodecyl sulfate(Cu(DS)₂) was used as special metal-ion source for the morphological control of copper oxide(CuO) architectures.During the fabrication processes,the ribbon-shaped intermediates of basic copper salt with lamellar structures were observed at 60.0℃for the first time. In the absence or presence of dodecanol(DOH),Cu(DS)₂ could react with sodium hydroxide to form dumbbell-like architectures of CuO nanoparticles.The incorporation of DOH molecules into the adsorption monolayers of surfactant ions could greatly enlarge the dumbbell size in length,probably depending upon the formation of the DOH-DS complex.These indicated that the template effectiveness of the intermediate ribbons,together with the hydrophobic interactions of adsorbed hydrocarbon chains,should account for the formation process of CuO dumbbells. Interestingly,the addition of sodium chloride into the reaction systems could induce the morphological change of CuO dumbbells to the twinanchors and then to the twin-spheres with two holes in the center.This further suggests that the hydrophobic interaction of pendent hydrocarbon chains provides an important approach for material fabrication purposes.(2) The functionalized surfactant of copper dodecyl sulfate(Cu(DS)₂) was used both as the metal ion source and as the crystal modifier to investigate the crystallization habits of cuprous oxide(Cu₂O).The increase of Cu(DS)₂ concentration from 0.27 to 6.82 mmol·L^-1 caused the morphological change of Cu₂O crystals from the truncated cubic to the cuboctahedral,then to the coexistence of the cubic and the truncated octahedral,and finally to the truncated octahedrons.As an experimental control,the inorganic salt of copper(â…¡) chloride system was also used as the metal ion source to conduct the crystallization of Cu₂O.These results indicate that the special adsorption of organic counterions(i.e.,dodecyl sulfate ions) exerted a great influence on the shape control of Cu₂O crystals,especially at a relatively low concentration.Meanwhile,the D-glucose concentration and the incubation time of crystals were also considered to discuss the crystallization habits of Cu₂O.In conclusion,the competitive adsorption of surfactant ions and D-glucose molecules onto crystalline faces,as well as the aging time,accounted jointly for the shape control of Cu₂O crystals.(3) ZnO crystals were synthesized by mixing zinc sulfate(ZnSO₄·7H₂O) and sodium hydroxide(NaOH) aqueous solutions at 60℃.In the presence of low concentration of sodium doedcyl sulfate(SDS),the added surfactants could only modify the size of ZnO crystals.While at a high concentration of SDS,the morphology of ZnO changed from corn-like structures into the twin-nanorods.When both SDS and DOH were simultaneously as additives,the structure of ZnO crystals changed from the spindle-like structures,with thin middle,to the hexagonal prisms and then to the twin-rods.At a fixed concentration of SDS,the average size of ZnO crystal increased at first and then reduced with increase of DOH concentration.The largest ZnO prism, obtained in the presence of 1.5 mmol·L^-1,possessed the hexagonal section and was 1.2±0.3μm in length.