CAREER: Alligned Carbon Nanotube Composite Array as Permeable Membrane for Selective Chemical Separations and Sensing

Project Summary: Described is a recently developed method to form a permeable membrane based on the hollow cores of carbon-nanotubes (CNT) passing perpendicularly through a polymer film. Briefly, a polymer film is spin-coated over an existing aligned-CNT array and the CNT tips are opened by plasma enhanced oxidation process. The carboxylic acid groups, only at the ends ofthe CNTs, are readily functionalized, allowing for highly selective affinity membranes. Gas and ionic transport through the membrane structure have been demonstrated with fluxes consistent with idealized pore geometry. Ion-channel mimetic sensor concept was demonstrated with CNT tips functionalization with biotin. When streptavidin is present ionic transport of RU(NH3)62+ is curtailed as seen by electrochemical detection. Proposed is the use of this structure to prove gate-keeper separation hypothesis, which is only possible with nm-scale control pore size and the ability for chemical functionalization. Further work using the membrane structure over the 5 year period includes quantifying gas separation, improved selective sensor design, CNT tip functionalization, improving control of CNT growth, and use of high temperature polymer systems. Also proposed is exploratory research into ionic pumps, capping CNT pore with zeolite nanoparticle for smaIl molecule separations, pore plating to further reduce inner CNT core diameter, and self-assembly of tip-only functionalized CNT rod structures on functionalized surfaces. Several collaborative studies are also identified. Educational Integration: Research efforts have been heavily integrated in education due to the development of two laboratory courses based on the core of my Materials research effort of fabrication and characterization; MSE 402G Electronic Materials and Processing and MSE 585 Materials Characterization. These courses are being further modified to encourage crossdisciplinary students by 2 programs. The first is my joint appointment to the Department of Chemistry for which I am modifying the lab portion of the Electronics Processing course to include nanotechnology and chemical functionalization of patterned materials. The second program is my involvement with the Nanotechnology in Undergraduate Education (NUE), in which I am modifying the Materials Characterization course to focus on nanotechnology systems. Proposed here is to also offer several short laboratory courses on nanofabrication in the summer that target cross-disciplinary graduate students, REU students, and under represented senior high-school students considering college education in engineering or sciences. The short courses (2-3 days) are derived from the formal multi-disciplinary fabrication course with content modified to target students' backgrounds and level. A web-based tutorial wiIl also be developed to reach a larger audience. Broader impact: Success in this research effort wiIl enable a new class of well controlled nmscale pore structure for selective chemical separations, sensors, drug delivery, and environmental remediation. Fundamental studies of transport at the nanometer scale will also be enabled by a well ordered system. Graduate students will strongly benefit from a truly cross-disciplinary research experience that will be the foundation of their research careers. Educational integration is structured to reach cross-disciplinary graduate students, undergraduates and high-school age underrepresented students. Hands-on experience learning would be an enabling experience to bolster both interest and confidence to tackle diverse technical careers related to nanotechnology.