Date of Award

2013

Degree Type

Thesis

Degree Name

Master of Science in Chemistry

Department

Chemistry

First Advisor

William Euler

Abstract

The first manuscript, “Fabrication of SERS Substrates for Explosive Detection,” focuses on the development of a Surface Enhanced Raman Scattering (SERS) substrate for use in the area of explosive detection. The substrate was created by immersion plating of silver onto porous silicon, resulting in a Ag roughened surface with an average roughness of 135 nm as determined by AFM. When explosive solutions, such as trinitrotoluene (TNT) and dinitrotoluene (DNT) in ethanol, were applied directly to the substrate, detection of unique Raman bands was possible down to the 10-9 – 10-10 mol/cm2 range. These results prove the technique is selective and shows promise for future work when vapor phase explosives will be investigated.

The second manuscript entitled “Light Trapping to Amplify Metal Enhanced Fluorescence with Application for Sensing TNT” focuses on the use of the previously mentioned substrate for Metal Enhanced Fluorescence (MEF). By using a polymer layer as a dielectric spacer in between the Ag layer and the fluorophore, enhancement of fluorescent emission was possible even though the spacer thicknesses was 10 – 20 times larger than typically reported. In experiments with rhodamine 6G, the fully assembled substrate resulted in a 1600-fold enhancement of emission. Compared to the usually reported 101 – 102 times enhancement, the large enhancement is suspected to occur due to numerous effects. As enhancements were observed with and without the roughened Ag layer, light trapping is suggested as a contributing factor in addition to MEF. While less effective in enhancing the emission of the conjugated polymer methoxy-ethylhexloxypolyphenylene-vinylene (MEH-PPV) that is known to interact with TNT vapor, the quench in fluorescent emission of MEH-PPV occurred more rapidly when the light trapping polymer was incorporated. Rapid detection and increased sensitivity are important features to the detection of trace explosives.

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