William J. Buttner

Generation of Controllable Nano-Gaps on Single Wall Carbon Nanotube

We demonstrated the application of the atomic force microscope (AFM) in generation of controllable nano-gaps on single wall carbon nano-tubes (SWCNTs). Tapping mode AFM combined with interleave mode was used to image and manipulate the CNTs. By precise control of the loading force and the scan rate, we were able to generate desired gaps on CNT nanowires ranging from 10.6 nm to 58.8 nm. The gap size dependence on loading force and scan rate was discussed. Such a structure can be applied in fabrication of capacitancebased nano-device toward sensor applications.Copyright

Amperometric H/sub 2/S sensor with Pd/Au electrode by electrochemical deposition

Amperometric gas sensors fabricated with various working electrode compositions were evaluated for sensitivity to H/sub 2/S in the presence of up to 50% hydrogen. The WEs consisted of a gold thin-film deposited on to a porous membrane substrate and the gold film modified with two different loadings of palladium (0.3 and 8.1 mg/cm/sup 2/). At a +800mV bias (vs. a Pb-mix reference electrode) the H/sub 2/S sensitivities in N/sub 2/ were 65.1, 16.3, 4947 nA/ppm, for pure gold, 0.03, and 8.1 mg/cm/sup 2/ palladium, respectively. In 1% hydrogen, the H/sub 2/S sensitivities were 38.2, 25.0, 120.9 nA/ppm for pure gold, 0.03, and 8.1 mg/cm/sup 2/ palladium, respectively. In 50% hydrogen the H/sub 2/S sensitivities were 32.5 and 14.4 nA/ppm for pure gold and 0.03, but at 8.1 mg/cm/sup 2/ palladium loading the H/sub 2/S response was not observed. Using a Pd/gold electrode increased sensitivity in air but in very high concentration of hydrogen, it was lower than the pure gold electrode.

Field-usable portable analyzer for chlorinated organic compounds

Transducer Research, Inc. (TRI) has been working with the DOE Morgantown Energy Technology Center to develop a new chemical monitor based on a unique sensor which responds selectively to vapors of chlorinated solvents. We are also developing field applications for the monitor in actual DOE cleanup operations. During the initial phase, prototype instruments were built and field tested. Because of the high degree of selectivity that is obtained, no response was observed with common hydrocarbon organic compounds such as BTX (benzene, toluene, xylene) or POLs (petroleum, oil, lubricants), and in fact, no non-halogen-containing chemical has been identified which induces a measurable response. By the end of the Phase I effort, a finished instrument system was developed and test marketed. This instrument, called the RCL MONITOR, was designed to analyze individual samples or monitor an area with automated repetitive analyses. Vapor levels between 0 and 500 ppm can be determined in 90 s with a lower detection limit of 0.2 ppm using the hand-portable instrument. In addition to the development of the RCL MONITOR, advanced sampler systems are being developed to: (1) extend the dynamic range of the instrument through autodilution of the vapor and (2) allow chemical analyses to be performed on aqueous samples. When interfaced to the samplers, the RCL MONITOR is capable of measuring chlorinated solvent contamination in the vapor phase up to 5000 ppm and in water and other condensed media from 10 to over 10,000 ppb(wt)--without hydrocarbon and other organic interferences.