Heterogeneity in the Response of Platinum/Polymer Hybrid Films to Aqueous Perchlorate

EPA Grant Number: F13E11491
Title: Heterogeneity in the Response of Platinum/Polymer Hybrid Films to Aqueous Perchlorate
Investigators: Norton, Amie Elizabeth
Institution: University of Cincinnati
EPA Project Officer: Lee, Sonja
Project Period: August 25, 2014 through August 25, 2016
Project Amount: $84,000
RFA: STAR Graduate Fellowships (2013) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Chemistry

Objective:

A platinum hybrid film can detect perchlorate; at 0.1 ppb, the emission from the films changes to an intense red color due to formation of a unique platinum salt. However, the underlying chemistry is not understood well enough to optimize this technology. At concentrations and solution volumes where the amount of platinum in the film exceeds the amount of available perchlorate, the films still exhibit a measureable response. Those films show luminescent hot spots, suggesting a surprising heterogeneous distribution of a platinum perchlorate salt. The focus of this research is to characterize the platinum and perchlorate distribution in perchlorateexposed films and identify the role of the polymer in perchlorate uptake from solution.

Approach:

Red luminescent hot spots appear when the amount of perchlorate in solution is less than the amount of platinum in a film. The working hypothesis is that the distribution of perchlorate and/or platinum in these films is heterogeneous. To test this idea, the luminescence from films will be imaged. Intensity histograms (from Matlab) will be used to map the heterogeneity and identify patterns in distribution of hot spots (e.g., near edges or wrinkles in the film). Subsequently, inductively coupled plasma mass spectrometry (ICP-MS) will be used determine the platinum and chlorine content in the yellow and red luminescent sections. The influence of the polymers on perchlorate uptake will be determined initially by investigating films without CPG particles or platinum salt. The hypothesis is that perchlorate has a tendency to partition into the polymer film and therefore contributes to the sensitivity of this system. The partition coefficient will be determined by using an ion-selective electrode (or ICP-MS for low concentrations) to measure perchlorate concentration in solution (csol). The concentration in the film (cfilm) will be inferred from the difference between the initial concentration and csol. The resulting distribution coefficients (Kd=cfilm/csol) will provide a measure of partitioning.

Expected Results:

To broadly disseminate the results and enhance scientific understanding, an open website will be created showing video clips of the response of platinum salts to anions. Through collaboration with a local high school, students in science classes (grades 8–12) will have hands-on experience with these hybrid materials. In one planned activity, students will test the colorimetric/luminescence response on water samples that they will collect in the greater Cincinnati area. The plan is to engage students in the process of documenting their activities (e.g., video clips) and posting these on the website. This project is expected to promote science literacy among the students, as well as among any other visitors to the website. A workshop will be held for rising 9th graders to spend a week in the laboratory preparing their own sensors for hazardous anion in drinking water. Finally, the research is expected to benefit society as a whole, primarily through enabling new technologies, which will promote better drinking water quality. This technology can be expanded to other anions such as nitrate. Also this work can be expanded to the vapochromic work already done in the laboratory at the University of Cincinnati. In addition, what is learned is expected to lay the foundation for strategies for designing highly sensitive, selective, easily used, inexpensive, rapid and portable luminescence- based sensors for aqueous anions, such as perchlorate. Pacific Northwest Laboratory is expected to use this material to detect TcO4, a radioactive water contaminant.

Potential to Further Environmental/Human Health Protection

This project will move toward developing a sensor for the onsite detection of perchlorate using a sensitive and selective platinum complex. This project also will engage high school students to make them more aware of environmental hazards and possible solutions.

Supplemental Keywords:

drinking water, perchlorate, sensors

Progress and Final Reports:

  • 2015
  • Final