The main objective of this study was to evaluate the feasibility of using nanoscale zero-valent iron (nZVI) as the source of hydrogen to enhance in situ anaerobic biodegradation of trichloroethylene (TCE). In the first part of this study, microcosms were constructed to evaluate the effects of different controlling factors [e.g., different redox conditions (aerobic and anaerobic conditions), different microorganisms (in situ microorganisms, activated sludge, and anaerobic sludge), and different sources of substrates and electron donors (phenol, cane molasses, hydrogen, and nZVI)] on TCE biodegradation. In the second part of this study, batch experiments were conducted to evaluate the feasibility of hydrogen production by nZVI and bimetallic particles. Results from the microcosm study indicate that in-situ microorganisms were capable of degrading TCE under aerobic and anaerobic conditions. Results also show that TCE removal was more effective by activated sludge and anaerobic sludge. Aerobic biodegradation of TCE was enhanced by the addition of phenol and cane molasses. Under anaerobic conditions, TCE removal could be improved when cane molasses and hydrogen were supplied. In addition, anaerobic TCE degradation was more effective with the presence of hydrogen. Results of microcosms conducted with the addition of nZVI reveal that TCE was degraded completely in both live and autoclaved microcosms. This indicates that chemical reductive dechlorination seemed to dominate the removal of TCE in microcosms. Therefore, further studies with higher TCE concentrations or lower nZVI doses need to be conducted to determine the effects of the produced hydrogen on TCE biodegradation. Results from the hydrogen production experiments indicate that efficiency of hydrogen production by nZVI ranged from 30% to 76%. Higher dose of nZVI addition resulted in higher amount of hydrogen production. The total amounts of hydrogen production were correlated with the doses of nZVI. In addition, rates and efficiency of hydrogen production by bimetallic particles were better than those of nZVI. Results of the batch experiments reveal that nZVI and bimetallic particles had good efficiency on hydrogen production. This indicates that nZVI and bimetallic particles have high potential to be used as hydrogen producers. In this study, a simple system consisted of only water and nZVI or bimetallic particles was applied to produce hydrogen. Although TCE in microcosms with nZVI addition was totally consumed by nZVI, results of microcosms with hydrogen addition demonstrated that hydrogen was able to improve the efficiency of anaerobic TCE biodegradation. Thus, it may be feasible to use nZVI as the source of hydrogen to enhance in situ anaerobic biodegradation of TCE. The advantages of using nZVI as the source of hydrogen include: (1) rapid removal of significant contaminant concentrations in the early stage of nZVI injection; (2) creation of a more reducing environment; (3) safer than liquid hydrogen, which is stored in steel containers; and (4) direct hydrogen supply without transfer of biological mechanisms compared to commercial hydrogen release compounds and other organic substrates. Results of this study suggest that biological reductive dechlorination of TCE can be enhanced if proper doses of nZVI are supplied in situ. Knowledge and comprehension obtained in this study will be helpful in designing an enhanced in situ anaerobic bioremediation system for a TCE-contaminated site.

Nanoscience dominates virtually every field of science and technology in the 21st century. Nanoparticles are of fundamental interest since they possess unique size- dependent properties (optical, electrical, mechanical, chemical, magnetic etc.), which are quite different from the bulk and the atomic state. Bimetallic nanoparticles are of particular interest since they combine the advantages of the individual monometallic counterparts. The present study focuses on bimetallic nanoparticles containing gold as one of the constituents. Au-Pd, Au-Pt and Au-Ag bimetallic/alloy nanoparticles have been prepared by four different synthetic methods, and characterised by a variety of techniques, with an emphasis on Au-Ag alloy systems in the solution phase as well as in the form of nanostructured films on solid substrates. Au- Ag alloy nanoparticles have been used to demonstrate two different applications. The first is the use of Au-Ag monolayer protected alloy clusters in demonstrating single electron charging events in the solution phase as well as in the dry state. Single electron transfer events involving nanosized particles are being probed extensively due to their potential applications in the field of electronics. The second is an analytical application, involving the use of trisodium citrate capped Au-Ag alloy hydrosols as substrates for surface enhanced Raman and resonance Raman scattering [SE(R)RS] studies. The sols have been used for single molecule detection purposes. Various organic molecules such as quinones, phthalocyanines and methyl violet have been self- assembled in a stepwise manner on the nanoparticulate as well as bulk Au, Ag and Au-Ag surfaces, and characterised extensively by spectroscopic, electrochemical and spectroelectrochemical techniques.