Synthesis Of Silver Nanoparticles On Modified Multi-walled Carbon Nanotubes And Their Antimicrobial Effects

The main propose of this paper is to improve the solubility of multi-walled carbon nanotubes and explore simple and highly-efficient method of synthesis carbon nanotubes/silver nanoparticles compound materials.In this paper, the covalent modification (strong oxidation method) method was adopted to modify MWNTs. Carboxyl groups generate on the surface of carbon nanotubes by using concentrated sulfuric acid and nitric acid. FT-IR spectroscopy reveal that there is a clear carboxyl peak of the modified carbon nanotubes. This article focuses on the use of poly acrylic acid (PAA) to modify carbon nanotubes. The TGA data indicate that the optimal reaction condition is reaction time is 8 h, and the ratio of PAA/ 20:1(by weight). According to X-ray photoelectron spectroscopy (XPS) data, between PAA and carbon is a chemical bond. Compare scanning electron microscope (SEM) and transmission electron microscope (TEM) of MWNTs which modified by the above two methods. After PAA modification the length of MWNTs without any change, there is also no opening phenomenon. But the mixed acids (concentrated sulfuric acid and nitric acid) modification method makes MWNTs become fractured and the end of the MWNTs was opened. The result indicates that PAA modification method makes the basic form of carbon nanotubes have been well protected and will not undermine the basic properties of carbon nanotubes. Solubility of the MWNTs which modified by the two methods have been greatly improved.In this article also explores the methods of synthesis carbon nanotubes/silver nanoparticles compound materials and do some research on the antibacterial characters. In the early, silver nanoparticles on modified multi-walled carbon nanotubes are synthesis by the way of chemical reduction. The effects of the different reaction time, reaction temperature and different ratio of the silver source and protective agent are studied. Additionally,exploratory attempt to prepare the nano-Ag/MWNTs using UV irradiation. The nanohybrids are investigated with Fourier transform infrared test(FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The antimicrobial effect of the nanohybrid is researched through the test of inhibition zone. The results show that the surface of the mixed acid modified multi-walled carbon nanotubes is connected to the carboxyl and the hydroxyl groups , the length of carbon nanotubes is shorter and the ends are opened. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy ( XPS) results show that the uniform silver nanoparticles with the average size about7.5 nm are set on the modified carbon nanotubes. According to the X-ray diffraction patterns (XRD), the nano-silver crystal structure is mainly fcc. The zone of inhibition experiments shows that the carbon nanotubes / silver composites have significantly bactericidal effect.In this paper, it shows the first example of synthesis of silver nanoparticles on surface-functionalized multi-walled carbon nanotubes (PAA-g-MWNTs-Ag) by UV irradiation method. It was easily synthetized just by putting the surface-functionalized MWNTs and silver nitrate mixture under ultraviolet condition. The best condition to synthesis nanotubes/silver nanoparticles compound materials is: concentration of silver nitrate (AgNO3) is 5 mM, ultraviolet light intensity is 40w and shine for 5 hours. X-ray photoelectron spectroscopy (XPS) reveals that Poly (acrylic acid) (PAA) functionalized MWNTs (PAA-g-MWNTs) were successfully compounded by grafting acrylic acid (AA) covalently no MWNTs. FT-IR spectroscopy shows that there is a clear carboxyl peak of the modified carbon nanotubes. According to the photos we took regularly, the PAA-g-MWNTs could be dispersed stability in both organic and inorganic solvent comparing to the raw MWNTs. It can be seen that the PAA-g-MWNTs dispersion in ID water, ethanol and acetone did not exhibit any visible changes for over 1 year. PAA-g-MWNTs-Ag composite materials were characterized by transmission electron microscope (TEM), energy dispersive spectrum (EDS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The X-ray photoelectron spectroscopy (XPS) peak shift observed in our work indicates the presence of the interaction between Ag nanoparticles and PAA-g-MWNTs is chemisorption. The transmission electron microscope (TEM) results indicated that the diameter of Ag nanoparticles which were chemisorbed to the PAA-g-MWNTs was approx 5 nm~7 nm. According to the X-ray diffraction patterns (XRD), the nano-silver crystal structure is mainly fcc. The zone of inhibition experiments shows that PAA-g-MWNTs-Ag composite materials have great property as antimicrobial agent against marine bacteria such as Bacillus, G. arthrobacterium and Y. streptococcus. These composite materials are potentially expected as electro-catalysts in fuel cells, ion exchange membrane electrolyzers and antimicrobial paints.