The Interface Assembly Of Viologen Molecules Aggregate Materials And Their Properties

The research of organized molecular aggregates in recent years has developed a new field of chemistry, based on the interaction and coordination between two or more molecules, it has provided a large opportunity for us to achieve a great quantity of innovations on various kinds of scientific knowledge.Viologen (V) is an important substance which can construct several kinds of organized molecular aggregates. Owing to its excellent electrochemical reversibility and the distinctive oxidation-reduction which always accompanied by a color change, viologen is frequently applied as the media for electronic transfer, which is widely used in diversified studies of organic/inorganic compounds and biological systems.In the present work, we used viologen as a point of departure from which we processed researches by two directions:Developed a process for the design and preparation of metal ion (M)-viologen and carbon nanotube (CNT)-viologen, then used the well-developed molecular assembly methods—Langmuir-Blodgett (LB) technique and casting technology to assemble M-V and CNT-V ultrathin films. These films were characterized, with detailed studies on the optical and electrochemical properties of the viologen and related compounds. The details are summarized as follows:PartⅠFirstly, we prepared a series of viologen derivative contained tolunitrile substituents through certain method—one group of viologen including N,N'-di(m-tolunitrile)-4,4'-bipyridium dibromide (VIA) and N,N'-di(o-tolunitrile)-4,4'-bipyridium dibromide (V2A) were water-soluble, another were the viologens of bishexafluorophosphate salts (V1B and V2B) obtained by reprecipitation of V1A and V2A which were water-insoluble but well dissolved in organic solvents. Then using series of characterization methods such as ultimate analysis, UV-vis absorption spectroscopy, infrared absorption spectroscopy we proved their structures. Afterwards, we use electrochemical methods to measure cyclic voltammograms (CVs) and chronocoulomograms of V1A, V2A in the 10 mM KC1 electrolyte solutions at various concentrations and VIA, V2A, V1B, V2B in pure ionic liquids respectively. The result indicated that viologen contained tolunitrile substituents had excellent electrochemical activity in ordinary electrolyte solutions and pure ionic liquids, and with the change on positions of tolunitrile substituents, viologens' properties are also influenced.Secondly, we used the casting technology to prepare VIA,V2A,V1B,V2B conjugates modified glass carbon (GC) electrodes. Then using electrochemical methods we measured cyclic voltammograms and chronocoulomograms of V1A, V2A, V1B, V2B in 10 mM KC1 electrolyte solutions and pure ionic liquids. The result indicated that the films of viologen contained tolunitrile substituents prepared through this method had certain electrochemical activity, but their stability were not satisfactory.Thirdly, with the use of LB technique we transferred monolayer and LB films of Fe2+-Mediated Polyelectrolyte Frameworks——Fe2+-V1B, Fe2+-V2B onto substrate surfaces, then recorded the X-ray photoelectron spectroscopy (XPS) spectra for the LB films on the quartz substrate surfaces and measured their cyclic voltammograms and chronocoulomograms on the indium tin oxide (ITO) electrodes. The results suggested that the Fe2+-Mediated Polyelectrolyte Frameworks could not only support the formation of stable M-V films but also enhanced the electron transfer efficiency between the electrode surfaces and the active centers of the viologen. So through this method we provided a facile route to prepare organic-inorganic hybrid films of electroactive frameworks for the chemically modified electrodes, which could be developed as an electron mediator of enzymes (such as hydrogenase) and as redox-based molecular devices.PartⅡFirstly, we used the casting technology to prepare viologen, Nafion-viologen, single-walled carbon nanotubes (SWCNT)/Nafion-viologen conjugates modified glass carbon (GC) electrodes respectively. Then using the electrochemical methods we measured their cyclic voltammograms and chronocoulomograms. The results showed that with the Nafion as the adhesive, the co-existed SWCNT could enhance the electron transfer efficiency between the electrode surfaces and the active centers of the viologen.Secondly, with the use of LB technique we transferred Monolayer and LB Films of amphiphilic viologen onto substrate surfaces and measure their cyclic voltammograms and chronocoulomograms. The results showed that through this method the LB films we prepared had poor stability and their activity had been affected irregularly.Finally, we found a method to prepare multiple-walled carbon nanotubes (MWCNT)-viologen aggregates and testified their structures by thermogravimetric analysis (TGA) and Raman spectrum. Then using LB technique we transferred monolayer and LB films of MWCNT-viologen aggregates onto substrate surfaces, observed their appearance by scanning electron microscope (SEM) and measured their cyclic voltammograms and Chronocoulomograms. The results suggested that with the cooperation of M WCNT, some kinds of amphiphilic viologen we chose were able to form monolayer and LB films which could not only maintain the activity of amphiphilic viologen but also enhance the stability of ultrathin film.