Selective, scaled-up self assembly of single walled carbon nanotubes for analytical separations

PRES 26

Mahesh Karwa, mk9@njit.edu, Department of Chemistry, New Jersey Institute of Technology, 138 Warren Street, Newark, NJ 07102, Zafar Iqbal, iqbal@adm.njit.edu, Chemistry and Environmental Science, Professor, New Jersey Institute of Technology, 138 Warren Street, Newark, NJ 07102, and Somenath Mitra, mitra@njit.edu, Chemistry and Environmental Science, Professor, New Jersey Inst. of Technology, 138 Warren Street, Newark, NJ 07102.
An interesting feature of Single Walled Carbon Nanotubes (SWCNTs) is their high surface area, high temperature stability, their framework of single layer of atoms and the ability to self-assemble them. This provides unique opportunities for the development of higher performance separation techniques that utilize the nano-scale interactions. For the first time a scaled-up selective self assembly of single walled carbon nanotubes inside meter long stainless steel tubings for a real world application, such as, gas chromatographic analysis was explored. A SWCNT film with an average thickness of 300 nm was self-assembled by a unique, single-step, catalytic chemical vapor deposition (CVD) process consisting of dissolved cobalt and molybdenum salts in ethanol. The SWCNTs then served as a gas chromatography stationary phase. A variety of organic compounds with varying polarity were separated at high resolution, and the column efficiency demonstrated ~1000 theoretical plates/m. Comparison of capacity factors and isosteric heats of adsorption with a packed tubing containing a commercial sorbent (Carbopack C) showed comparable results. This demonstrated high capacity and strong sorbate-sorbent interactions on the SWCNT phase. Evaluation of the McReynolds constants suggested that the SWCNT was a non-polar phase. The SWCNT media allowed separations of gases, and at the same time, its high thermal stability (>425oC) permitted separations of higher molecular weights at higher temperatures, thus extending the range of conventional chromatography on the same column.