Demonstration and Validation of a Portable Raman Sensor for In Situ Detection and Monitoring of Perchlorate (ClO4-)

ER-201327

Objective

The objective of this project is to demonstrate, validate, and optimize the performance and sensitivity of a new portable Raman sensor for rapid detection and analysis of perchlorate anion (ClO4-) in groundwater at Department of Defense (DoD) sites. Specific objectives are to: (1) validate the performance of the portable Raman sensor for the detection of ClO4- as a target analyte; (2) optimize the performance and sensitivity of the sensor through precision fabrication of a new type of nanostructured Raman substrates and the fiber-optic sensor probe; (3) optimize field-testing methodologies and establish standard protocols for use by field technicians; (4) partner with a commercial vendor for the production of Raman substrates; and (5) evaluate and document the cost effectiveness of the new sensing technology by comparing it with conventional laboratory-based analytical protocols.

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Technology Description

A prototype portable Raman sensor has been developed under SERDP project ER-1602. The technology is so-called surface enhanced Raman spectroscopy (SERS), referring to million-fold or greater enhancements of the Raman signal of target analyte molecules adsorbed at or near nanostructured noble metal surfaces (called SERS substrates). It thus allows the detection of analytes at ultra-low concentrations in water. Moreover, since SERS provides signatures or molecular vibrational frequency shifts of specific chemical bonds (e.g., perchlorate at approximately 935 cm-1, and nitrate at 1050 cm-1), the technique is highly selective to specific analyte molecules, potentially enabling simultaneous, multi-species detection and analysis. The fabrication of highly ordered, nanostructured SERS substrates with small nano-gap sizes is a key step for realizing the SERS enhancement. The team recently developed and demonstrated a new type of ordered and elevated gold bowtie arrays with controllable gap sizes to less than 8 nm, and the substrate showed superior reproducibility and high sensitivity with an enhancement factor on the order of 1011. The detection of perchlorate as low as 0.1 ppb (µg/L) in synthetic groundwater was shown. In collaboration with Shaw Environmental and Nanova Inc., this project will develop and optimize the technology through nanoimprinting for large-scale production of nanostructured SERS substrates, build a field-based sensor that can be commercialized, and test the sensor at multiple DoD sites.

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Benefits

The portable Raman sensor is expected to allow rapid and cost-effective screening and monitoring of perchlorate and possibly other co-contaminants in situ at low concentration levels. In comparison with traditional approaches, because sample shipping and typical costs associated with laboratory analysis can be eliminated, a significant cost reduction may be realized by using the sensor for both short- and long-term monitoring and analysis at DoD sites. Portable and near real-time analysis also allows higher spatial and temporal density data collection from each sampling event and rapid turn-around of information to decision makers for site characterization and remediation purposes. For example, when new wells are being drilled to characterize a plume, a field-based Raman sensor could provide nearly real-time contaminant concentrations, thus allowing more efficient use of expensive drilling rigs and crews, with far less downtime, as well as better decision-making concerning plume delineation. (Anticipated Project Completion - 2016)

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Points of Contact

Principal Investigator

Dr. Baohua Gu

Oak Ridge National Laboratory (ORNL)

Phone: 865-574-7286

Fax: 865-576-8543

Program Manager

Environmental Restoration

SERDP and ESTCP

Document Types

  • Fact Sheet - Brief project summary with links to related documents and points of contact.
  • Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
  • Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
  • Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
  • Guidance - Instructional information on technical topics such as protocols and user’s guides.
  • Workshop Report - Summary of workshop discussion and findings.
  • Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
  • Model/Software - Computer programs and applications available for download.
  • Database - Digitally organized collection of data available to search and access.