Project 5: Nanotechnology-based environmental sensing
Summary
Presentation: Overview of Project 5
There remains a compelling need for improved ways to detect and quantify toxic and/or hazardous chemical species found at existing or potential Superfund sites. Better analytical techniques could reduce the cost of monitoring, help improve remediation methods, and more accurately assess the health risks associated with hazardous and toxic species. Project investigators have developed methods to produce novel nanoparticles, arrays, and structures that could be used for chemical analysis, and are developing several approaches that combine evolving methods with the characterization and monitoring needs of Superfund. They are linked by their use of small scale properties to develop new methods that should be faster, easier, smaller, and/or less expensive. These technologies could ultimately lead to a number of nanometer-based devices which are portable and robust, and which can be employed at commercial facilities or in-the-field for environmental monitoring. Dr. Koshland’s team’s goals are to: 1. Develop low-cost sensors and sensor arrays for measuring chemical species such as arsenic and mercury using nanoparticle properties that can be probed optically and electronically. 2. Develop methods to identify biomolecules (specific antibodies/antigens used in bioremediation) by probing their unique local electronic structure using electron tunneling. 3. Investigate the use of new manufactured nanostructured materials for molecular detection, including structures such as carbon nanotubes and coated nanoparticles. This project is divided into four tasks: Gas Phase Detection of Heavy Metals Using Nanoparticle Complexes with Laser Fragmentation Spectroscopy, Mercury Detection with Gold Nanoparticles, Surface Enhanced Raman Spectroscopy Detection of Arsenic Species, and the Detection of Bioremediation Organisms using Electronic Cell Typing. This project is investigating using the different and sometimes unique behavior of materials as their size shrink below 100 nm to develop new methods to detect chemical and biological species found at existing or potential Superfund sites. New sensors could reduce the cost of monitoring, help improve remediation methods, and more accurately assess the health risks associated with hazardous and toxic species.
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Project Update
Drs. Catherine Koshland and Donald Lucas research objective is to develop easier, smaller, and/or less expensive methods to detect and quantify toxic and/or hazardous chemical species found at existing or potential Superfund sites. New sensors and diagnostics could reduce the cost of monitoring, help improve remediation methods, and more accurately assess the health risks associated with these hazardous and toxic species. Their focus is on the use of nanotechnology-based sensing methods, since nanomaterials often have unique properties that differ from conventional bulk materials.
Project researchers have made significant progress towards a functional arsenic detector in ground water using a nanostructured SERS substrate. Using close-pack arrays of octahedral shaped silver nanocrystals, the researchers demonstrated the chemical sensing of arsenic ions with detection limits as low as 1 part per billion in solution. Their sensor is based on surface-enhanced Raman spectroscopy (SERS), where analyte molecules near nanostructured metallic surfaces experience huge enhancements in Raman scattering cross-sections, typically orders of magnitude higher than expected. The nature of vibrational spectroscopy allows them to simultaneously probe for arsenic in both of the commonly found oxidation states and discriminate between the two. This is important since the different oxidation states have different toxicities.
The detection is performed directly on the substrate by placing a droplet of the analyte solution onto the nanocrystal monolayer, with no additional sample preparation required. These substrates have been verified to work in the presence of known competing anions, and have been used to accurately characterize the arsenic levels in polluted well water obtained by collaborators in Nevada. Future work in this direction will include characterization of differently shaped nanocrystals and optimization of the SERS enhancement factor on each of these substrates.
The group continued work on developing elemental mercury detectors using gold nanoparticles. They have successfully used different techniques to immobilize the 5 nm diameter gold nanoparticles on a substrate using organosilanes to link the gold to the silica surface; this prevents coagulation and improves the sensor performance. The detector works for mercury in both the vapor phase and in the aqueous phase. The reserachers have determined that the attachment of the mercury to the gold nanoparticles is reversible at temperatures that do not damage the sensor. This finding opens a potential means of practical filtering of mercury from waste streams, since the nanoparticles have an extremely high surface area to volume ratio, and can be produced at reasonable costs. Additional work on avoiding cross-sensitivity to other pollutant species continues, using either physical or chemical barriers to prevent other species from reaching the gold surface.
The researchers also use microfabricated channels to detect and characterize individual cells based on their cell-surface receptors. The method involves measuring a current pulse generated when an individual cell passes through an artificial pore. When the pore is functionalized with proteins, specific interactions between a cell-surface marker and the functionalized proteins retard the cell, leading to an increased pulse duration that indicates the presence of that specific biomarker. The researchers successfully screened murine erythrolukemia cells based on their CD34 surface marker in both a single and mixed population of cells.
Publications
- Carbonaro, A., S.W. Mohanty, H. Hung, L.A. Godley, and Lydia Sohn. 2008. Cell Characterization Using a Protein-Functionalized Pore. Lab Chip. 8:1478-1485. doi:10.1039/b801929k (http://dx.doi.org/10.1039/b801929k)
- Holder, Amara, Donald Lucas, Regine Goth-Goldstein, and Catherine P. Koshland. 2008. Cellular Response to Diesel Exhaust Particles Strongly Depends on the Exposure Method. Toxicological Sciences. (http://www3.oup.co.uk/toxsci/) 103(1):108-115. doi:10.1093/toxsci/kfn014 (http://dx.doi.org/10.1093/toxsci/kfn014)
- Holder, Amara, Donald Lucas, Regine, Goth-Goldstien, and Catherine P. Koshland. 2008. Cellular Response to Diesel Exhaust Particles Strongly Depends on the Exposure Method. Toxicological Sciences. (http://www3.oup.co.uk/toxsci/) 103:108-115. doi:10.1093/toxsci/kfn014 (http://dx.doi.org/10.1093/toxsci/kfn014)
- Mulvihill, M., A. Tao, K. Benjauthrit, John Arnold, and Peidong Yang. 2008. Surface-Enhanced Raman Spectroscopy for Trace Arsenic Detection in Contaminated Water. Angewandte Chemie-International Edition. 47:6465-6460.