Nanotechnology Research

Tetrachloroethylene (TCE) is a common contaminate in groundwater that can cause anything from mild skin irritations to cancer. Currently, methods for removing this highly carcinogenic containment and others like it are inefficient and ineffective. Granular activated carbon (GAC) is often used to remove these contaminants by adsorbing them onto its surface. This simple method does not truly solve the contamination issue as it only relocates the carcinogen to another location. This could be especially problematic because TCE and many other harmful contaminates are classified as volatile organic compounds (VOCs) and therefore, vaporize readily when exposed to the air, creating an even more harmful situation than with which to begin (Chaplin 2012).

Go
Fig1. - Shows (a) SEM image of GAC supported catalyst and (b) TEM image of the same GAC supported catalyst. (c) and (d) Show the composition of the catalyst with the largest peaks showing gold, palladium, and carbon. Other peaks could be a result of leftover acetone and/or the copper plate on which the catalyst was held for viewing.Image Credit: Kavita Meduri

My research focuses on studying and synthesizing a novel palladium and gold catalyst that is supported by carbon, either graphene or GAC (Fig1.) to degrade TCE and other VOCs into ethene and ethane while "skipping" over the more harmful products that lie inbetween, like vinyl chloride (VC). This process is called hydrodechlorination (Fig2.).

Go
Fig2. - Shows the hydrodechlorination process of TCE to Ethene where the red arrow represents the path our catalyst forces TCE to take.

I have specifically studied the optical properties of our catalyst and what parts of synthesis effect our nanoparticles (NPs). To synthesize our catalyst, gold and palladium are sonicated with acetone and left to react for 24 hours at a certain temperature. I’ve looked at how the time of sonication and time left for our solution to react effects the synthesis of nanoparticles. To determine if, how many, or what size our NPs are, I use UV-spectroscopy (Img1.) to study the wavelength of light absorbed by our product.

Go
Img1. - UltraViolet Photospectrometer 36000 used to analyze NPs.

NPs undergo quantum confinement which leads to interesting changes in optical and electronic properties due to an increase of bandgap as the size of the nanoparticle decreases. Depending on the change in optical properties of the nanoparticles, the size or existence of NPs can be determined.

Go
Fig2. - Due to their small size, the electrons in quantum dots are confined in a small space and when the radii of the NP is smaller than the Bohr radius there is quantization of the energy levels. When the size of the NP decreases, the difference in energy between the highest valence band and the lowest conduction band increase resulting in More energy needed to excite the dot. More energy is released when the crystal returns to its ground state which causes a color shift. Image Credit: Sigma Aldrich.

Studying the properties of these nanoparticles is important in understanding how our catalyst works and to assure that is not further contaminating the environment or water. Our gold and palladium, carbon supported nanocatalysts are a promising solution for industry and environmental clean up that not only remove toxic contaminates like TCE, but degrade them into something else entirely.

Go