Single-walled carbon nanotubes (SWNT) represent a new class of emerging environmental pollutants. Investigations of fate and toxicity of SWNT in the environment are limited by the lack of reliable methods to detect these materials in complex mixtures at environmentally-relevant concentrations. The research objective of this project is to develop and validate a novel analytical technique based on near infrared fluorescence (NIRF) spectroscopy for characterization and quantitation of SWNT in complex environmental matrices such as estuarine sediments and tissues.
NIRF spectroscopy utilizes the unique electrical properties of semiconducting SWNT by measuring their fluorescence in the near infrared region of the spectrum. It has advanced as a highly selective and information rich technique for sensitive detection and structural characterization of SWNT materials. Extraction of SWNT e.g. from sediments into surfactant solutions allows a reduction of sample complexity and enhanced disaggregation of bundled SWNT prior to NIRF analysis.
In addition to concentration, structural information such as shape, length distribution or agglomeration state of SWNT must also be identified and quantified to describe behavior and transport processes as well as biological interactions. NIRF spectral features of SWNT are retained after their extraction from sediment, allowing diameter/chiral wrapping angle characterization for dilute solutions. Several purification, concentration, and separation strategies are being tested to reduce matrix complexity and improve the detection limit of SWNT. One approach is the application of field flow fractionation (FFF) as a separation method prior to NIRF analysis to determine SWNT length distribution and to reduce matrix complexity by separation of SWNT from associated natural organic matter.