Detection and Characterization of Chemicals Present in Tank Waste
The goal of this three-year project is to develop and demonstrate novel multi-parameter micro-electro-mechanical system (MEMS) sensors that are robust and can be used to simultaneously detect the presence of target chemicals in a mixture, radiation emitted from radioactive materials and the heat generated by the absorption of photons of specific wavelength by the target molecules.The goal of this program is to study and develop effective methods of immobilizing chemical selective phases for improved microsensor performance 1. Investigations of Photo-Induced and Adsorption-Induced Stress in Micromechanical Structures and Photothermal Spectroscopy Microcantilevers respond to chemical stimuli by undergoing changes in their bending and resonance frequency even when a small number of molecules adsorb on their surface. In our present studies, we extended this concept by studying changes in both the adsorption-induced stress and photo-induced stress as target chemicals adsorb on th e surface of microcantilevers. For example, microcantilevers that have adsorbed molecules will undergo photo-induced bending that depends on the number of absorbed molecules on the surface. However, microcantilevers that have undergone photo-induced bending will adsorb molecules on their surfaces in a distinctly different way. Coating the surface of a microstructure with a different material can provide chemical specificity for the target chemicals. Therefore combining measurements of photo-induced and adsorption-induced stress in MEMS devices caused by target molecules with microcalorimetric spectroscopy both the presence and identity of target molecules can be determined. In addition, radioactive chemicals can also be identified by measuring the temperature changes of micromechanical sensors as the absorb emitted radiation. (i) Studies of Adsorption-Induced Stress in MEMS We investigated the effect of absorption of trace amounts of target molecules, 2- mercaptoethanol and diisopropyl methylphosphonate (DIMP), on micromechanical structures. Although gold coated surfaces adsorb DIMP effectively, the selectivity can be substantially improved by first coating the surface with self-assembled monolayers. The chemical selectivity of the layer is based on the interaction of Cu+2 bound to the MEMS surface by a carboxylate-terminated n-alkanethiol monolayer. Microcantilever MEMS devices with such surface coatings were exposed DIMP molecules by flowing a mixture of N2 and DIMP vapor in a chamber containing the microcantilever. The composite self-assembled monolayer coating transiently adsorbs molecules of DIMP vapor, which causes the microcantilever to bend. We found that our derivitized MEMS respond proportionally and reversibly to the presence of DIMP molecules in a way that is distinguishable from any response to common organic solvents such as ethanol, methanol, or acetone. During the exposure time, we observed no measurable change in the resonance frequency of the MEMS.
- Research Organization:
- Oak Ridge National Lab., Oak Ridge, TN; University of Tennessee, Knoxville, Tennessee (US)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM) (US)
- DOE Contract Number:
- FG07-98ER62718
- OSTI ID:
- 833189
- Report Number(s):
- EMSP-65340-1999; R&D Project: EMSP 65340; TRN: US200430%%974
- Resource Relation:
- Other Information: PBD: 1 Jun 1999
- Country of Publication:
- United States
- Language:
- English
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