Bmorphological Controlled Preparation Of Polyaniline And Conductive Ag Nanostructures

With the rapid development of society, the traditional conductive material cannot maintain both stability of electricity and properties of strength at the same time, so it is urgent to exploit flexible conductor to satisfy the needs of technology and industry. The conductor fillers are the primary and key material for preparing flexible conducto r. Low-dimensional conductive materials are better than traditional materials in the photoelectric, magnetic, catalytic, sensor field for its huge surface area and quantum effects. It plays an extremely important role in the field of nano-optoelectronic devices, sensors, nano-biotechnology, energy storage and conversion. Polyaniline has good characteristics of doping/dedoping protons regulation, environmental stability, convenient synthesis and facile materials. However, it is difficult to dissolve and melt. Difficult processing hinders the practical application of polyaniline. The nanotechnological synthesis of conductive polyaniline, can combine the electrical conductivity and nano-structure, and greatly improve the processing of the conducting polyaniline. Since nano-structural polyaniline has both advantages of low-dimensional materials and organic conductors, now it becomes a hot focus as a new kind of flexiable conductive material. Nano-silver receives increasing interest because of its high conductivity, unique physical and chemical properties. Recently, a facile method capable of massively synthesizing silver nanorods with high aspect ratios is strongly desired to provide support for their application in commercial areas. This paper deals with the problems of the low dimensional nano-structural polyaniline preparation and morphology control, convenient method for the highly efficient preparation of large amount of silver nanorods and their formation mechanism. The specific contents are as follows:(1)Through chemical oxidation polymerization of aniline using ammonium persulfate as oxidant in the presence of sodium dodecyl sulfonate (SDS) as soft template polyaniline nanotubes with small sticks on the surface was synthesized. However, polyaniline nanotubes with smooth surface was prepared by adding a certain amount of carbonate to the polymerization process. The effects of kind and dosage of carbonates on the nanostructures of the polyaniline product were investigated. The results showed that, with increasing the amount of gas bubbles evolved, nanostructure of polyaniline was transformed from the nanotubes with smaller nano-rods on the surface, to the nanotubes with smooth surface, or to nanoflakes, according to the amount of carbon dioxide gas evolved. However, the morphology of polyaniline nanomaterials was almost not affected by changing the pH value of the system or addition of other salt which cannot produce gas bubble in the polymerization system. Though the carbonates changed the nanostructures of polyaniline, the molecular structure and crystallinity of polyaniline remained unchanged. All these facts demonstrated that gas bubbles formed during the polymerization process have an important influence on the formation of nanostructure of polyaniline. The mechanism was suggested that the CO2bubbles generated by the reaction of the carbonate with the sulfuric acid formed in-situ in the polymerization process can control different nano-structures of polyaniline.(2)Helical polyaniline nanostructure was synthesized in the presence of dextral camphor sulfonic acid. However, the helical polyaniline is a network structure. According to the application, which is limited in the low dimensional single device. Mono-disperse helical polyaniline nano-fiber was synthesized in a two-phase solution of water-organic solvent by interfacial polymerization method, which can effectively reduce the rate of its secondary growth. Dissolution of polyaniline in the upper aqueous layer can effectively reduce its aggregation or deposition. The formation mechanism is that through interaction of N-H hydrogen bond between camphor sulfonic acid and aniline, aniline can orderly combine and form at the same side of the oligomer, due to the induction of chiral carbon. Furthermore the helical poly(o-aminophenol) a hydroxyl derivative of polyaniline, was synthesized in the presence of polyethylene glycol. The formation mechanism is attributed to the role of long-chain flexible polyethylene glycol, benzene ring accumulation in long-chain flexible molecules and formation of micro-helical structure. The FT-IR, UV-Vis, elemental analysis and electrical properties of the helical polyaniline and helical poly(o-aminophenol) were measured. (3)It was reported that using ethylene glycol as solvent and reductant, polyvinyl pyrrolidone(PVP) as capping agent, silver nanorods was prepared by reducing silver nitrate, but the concentration of AgNO3was not exceed0.10M. In this paper, under the action of appropriately preformed silver crystal seeds and controlled addition rates of silver nitrate and PVP solution, silver nanorods with length of2-15μm and diameter of200-880nm can be obtained in high concentration of AgNO3as0.50M. Through study of the effects of various factors on the nanostructure of silver, the favorable conditions are:appropriately preformed seeds concentration at6.54-9.81mM, addition rate of AgNO3solution at0.30-0.43mL/min and molar ratio of PVP/AgNO3at1.1-1.4, the stirring speed was350rpm and the reaction temperature was160℃. The mechanism of preparing silver nanorods in high concentration was suggested as follows:When the AgNO3concentration was high, in the presence of a certain concentration of silver seeds (multiply twinned particles of decahedral shape), which can increase the growth rate of silver atoms on the seeds, due to the existence of more surface area of the silver seeds, thus making the crystal growth rate match the high reduction rate of AgNO3by ethylene glycol. With the help of the capping action of PVP on facets [100] and silver growth on facets [111], silver nanorods were produced. This method without using other metal or salt can not only improve yield of silver nanorods, but can also save80%dosage of glycol.