Electrophoretic analysis and separation of single-walled carbon nanotubes and metallic nanoparticles

Electrophoresis has been widely used in biological science but has barely applied to nanomaterials. This study is to demonstrate the applications of electrophoresis to separation and analysis of nanomaterials based on size and shape.; In an effort to purify arc-discharge single-walled carbon nanotubes (SWNTs), we developed a procedure to separate larger graphite-related materials from stable crude nanotubes suspension, which was subjected to electrophoretic separation in glass bead matrix and agarose gel. Three important components were well separated: purified SWNTs, short tubule carbon species, and fluorescent fragments. For the first time, electrophoresis has been successfully used to purify arc-discharge SWNTs. Moreover, the two classes of new nanomaterials: short tubule carbon and fluorescent fragments promise to be useful in their own right.; The electrophoretic technique was extended to the separation of gold nanoparticles. First, column electrophoresis was demonstrated to separate nanospheres based on size. Next crude nanospheres were electrophoretically purified. The standard deviation of crude sample of 20% was narrowed to 3--4% of purified sample, indicative of substantial improvement in size distribution. Finally, the crude gold nanorod sample was separated into three components based on shape: spheres, platelets, and rods. Gel electrophoresis has demonstrated much higher resolution than conventional methods: multi-step centrifugation, size exclusion chromatography, etc.; In spite of the fact that SERS activity is intimately associated with the size and shape of nanoparticles, there are rare reports on how to find the size and shape of nanoparticles with highest SERS activity. To achieve this goal, we have designed a procedure. First, crude silver nanoparticles with wide distribution in size and shape was synthesized and functionalized. Then gel electrophoresis was used to separate the nanoparticles into different colorful bands and each of them may correspond to the plasmon resonance scattering of the uniform nanoparticles in size and shape. It has been found the activity is very dependent on different sizes and shapes. Future work will find the absolute SERS intensity of each band after considering silver concentrations. A useful technique will be anticipated to sensor the SERS activity based on size and shape of nanoparticles.