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Advanced Nanosensors for Continuous Monitoring of Heavy Metals

Omowunmi A. Sadik, Joseph Wang, Ashok Mulchandani, Isaac Kowino, Jason Karasinki, Marcells Omole, and Daniel Andreescu
State University of New York at Binghamton, Binghamton, NY

The overall objective of this work is to incorporate novel, colloidal-metal nanoparticles into a bed of electrically conducting polymers, and then use these for the development of nanosensors. During Year 1 of the project activities, we explored the feasibility of designing advanced conducting polymeric materials for sensing and remediation applications. These include the synthesis of: (1) polyamic acid-silver nanoparticle composite membranes, (2) polyoxy-dianiline films, and (3) electrochemical deposition of gold nanoparticle films onto functionalized conducting polymer substrates. These were characterized using electrochemical and surface morphology techniques including TEM, AFM, CV, and FTIR. The summary of the synthetic efforts has been published in Langmuir and Journal of Electrochemical Society.

The highlight of our efforts during Year 2 is the development of a Pd synthetic approach that was tested as environmental catalyst for the conversion of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)]. During the reporting period, we selected one of our synthetic nanostructured materials reported in Year 1, and tested these as environmental catalyst for the conversion of higher valent to low valent Cr in soil and water samples. Chromium exists in the environment mainly in two different oxidation states: Cr(III) and Cr(VI). While Cr(III) is considered a nutrition supplement for regulating normal bodily functions, Cr(VI) is a potential carcinogen with remarkable harmful effects on both plants and animals. Currently, Cr(VI) is converted to Cr(III) using chemical assay formats such as wet acid digestion, which are usually labor intensive and require the use of hazardous chemicals. Therefore, there is a need to design novel Cr(VI) remediation approaches that are safe, fast and can efficiently convert Cr(VI) to Cr(III).

The application of nanoparticles could be used to address such needs due to their relatively large surface areas that allow for high reactivity rates. There is, however, little or no information regarding the application of palladium-nanoparticles (Pd-NPs) in the conversion of Cr(VI) to Cr(III) in soils and aqueous media. The real sample application of the Pd nanoparticles-sulfur mixture tested using soil samples produced over 92 percent conversion in the presence of Pd-NPs/S within 1 hour. In contrast, only 33 percent of the same concentration was converted to Cr(III) in the absence of Pd-NPs/S. This represents more than a 500-fold improvement in conversion rate compared to current microbial approaches. This work offers a new and safe application of nanotechnology for the reduction of high oxidation state heavy metal pollutants. In addition, we have reported the use of Bismuth electrodes for sensing. In this presentation, we will discuss these results and future goals.

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