Impedance biosensor chips were developed for detection of Escherichia coli O157:H7 based on the surface immobilization of affinity-purified antibodies onto indium tin oxide (ITO) electrode chips. The immobilization of antibodies onto ITO chips was carried out using an epoxysilane monolayer to serve as a template for chemical anchoring of antibodies. The surface characteristics of chips before and after the binding reaction between the antibodies and antigens were characterized by atomic force microscopy (AFM). The patterns of the epoxysilanes monolayer, antibodies, and E. coli cells were clearly observed from the AFM images. Alkaline phosphatase as the labeled enzyme to anti-E. coli O157:H7 antibody was used to amplify the binding reaction of antibody-antigen on the chips. The biocatalyzed precipitation of 5-bromo-4-chloro-3-indolyl phosphate by alkaline phosphatase on the chips in pH 10 PBS buffer containing 0.1 M MgCl2 increased the electron-transfer resistance for a redox probe of Fe(CN)6(3-/4-) at the electrode-solution interface or the electrode resistance itself. Electrochemical impedance spectroscopy and cyclic voltammetric method were employed to follow the stepwise assembly of the systems and the electronic transduction for the detection of E. coli. The biosensor could detect the target bacteria with a detection limit of 6 x 10(3) cells/mL. A linear response in the electron-transfer resistance for the concentration of E. coli cells was found between 6 x 10(4) and 6 x 10(7) cells/mL.

Anodization of titanium in a fluorinated dimethyl sulfoxide (DMSO) and ethanol mixture electrolyte is investigated. The prepared anodic film has a highly ordered nanotube-array surface architecture. Using a 20 V anodization potential (vs Pt) nanotube arrays having an inner diameter of 60 nm and 40 nm wall thickness are formed. The overall length of the nanotube arrays is controlled by the duration of the anodization, with nanotubes appearing only after approximately 48 h; a 72 h anodization results in a nanotube array approximately 2.3 mum in length. The photoelectrochemical response of the nanotube-array photoelectrodes is studied using a 1 M KOH solution under both UV and visible (AM 1.5) illumination. Enhanced photocurrent density is observed for samples obtained in the organic electrolyte, with an UV photoconversion efficiency of 10.7%.

Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 microM uranium as U(VI). Through a series of experiments at a pilot scale test facility, we explored the lower limits of groundwater U(VI) that can be achieved by in-situ biostimulation and the effects of dissolved oxygen on immobilized uranium. Weekly 2 day additions of ethanol over a 2-year period stimulated growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria, and immobilization of uranium as U(IV), with dissolved uranium concentrations decreasing to low levels. Following sulfite addition to remove dissolved oxygen, aqueous U(VI) concentrations fell below the U.S. Environmental Protection Agengy maximum contaminant limit (MCL) for drinking water (< 30/microg L(-1) or 0.126 microM). Under anaerobic conditions, these low concentrations were stable, even in the absence of added ethanol. However, when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L(-1)) entered the injection well, spatially variable changes in aqueous U(VI) occurred over a 60 day period, with concentrations increasing rapidly from < 0.13 to 2.0 microM at a multilevel sampling (MLS) well located close to the injection well, but changing little at an MLS well located further away. Resumption of ethanol addition restored reduction of Fe(III), sulfate, and U(VI) within 36 h. After 2 years of ethanol addition, X-ray absorption near-edge structure spectroscopy (XANES) analyses indicated that U(IV) comprised 60-80% of the total uranium in sediment samples. Atthe completion of the project (day 1260), U concentrations in MLS wells were less than 0.1 microM. The microbial community at MLS wells with low U(VI) contained bacteria that are known to reduce uranium, including Desulfovibrio spp. and Geobacter spp., in both sediment and groundwater. The dominant Fe(III)-reducing species were Geothrix spp.