A Systematic Search for New Bismuth and Lead Based Oxide Scintillators and Semiconductors. CHRISTOPHER JESSAMY (North Carolina Agricultural and Technical State University Greensboro, NC 27411) ANGELA EDWARDS (North Carolina Agricultural and Technical State University Greensboro, NC 27411) DR. STEPHEN DERENZO (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

In recent times, the steady increase in the uses of radiation detectors has imoposed a great need for higher efficiency and lower costs of detector production. Through such an acheivement, applications ranging from medical imaging to weapons detection may be realized. Prompted by this demand, our research focuses on the discovery of new radiaton detectors. In this manuscript we report the results of a systematic search for such detectors that have structures based on lead and bismuth. In this work we synthesized and characterized four compounds: Bi₂TeO₅, PbTeO₃, Ca₂Bi₂O₅, and Compound A. We were able to identify four semiconductors (Compound A and Compounds 1-3) by DC ionization under gamma irradiation.

Arsenic Removal Using Bottom Ash (ARUBA). EBERECHUKWU CHUKWUEKE (Contra Costa College San Pablo, CA 94806) ASHOK GADGIL (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

Arsenic is a naturally occurring heavy metal found in the earth's crust. Its presence in drinking water has become an issue of global concern due to numerous lethal occurrences particularly in countries in Bangladesh where the situation is called the largest mass poisoning in human history. The current guideline by World Health Organization (WHO) for arsenic is 10 µg/L. In Bangladesh, about 60 million people are exposed to levels higher than 50 µg/L (the Bangladeshi guideline) arsenic in drinking water and about 10% of the adults (about 13 million) will die of arsenic poisoning if nothing is done. Long term exposures of low concentrations may cause internal cancers including bladder, skin, lung and prostate cancer. Other effects of arsenic exposure include cardiovascular, pulmonary, immunological and neurological effects. Arsenic is mostly present as two species in ground water, arsenate (As5+) and arsenite (As3+). Previous studies have shown the removal efficiency of both species to be highly dependent on pH. The objective of this project is to develop a cheap and effective method to remove arsenic from drinking water as to make it affordable even to the poorest residents in Bangladesh. Our overall approach is based on coating small sized particles (1-10um) of bottom coal ash (a finely powdered and sterile waste material from coal-fired power plants) with ferric hydroxide and using them to immobilize and remove arsenic in water supplies. In this study, we examined the capacity of LBNL media to remove both As(V) and As(III) from water. We also examined the effect of pH on adsorption efficiency of As(V) and As(III). Finally, to make the LBNL approach more cost effective, we examined the effect of recycling excess FeSO4 solution on the capacity of resulting media. Our results demonstrate that the removal of arsenite is more effective at high PH while the removal of arsenate is more effective at low pH. Based on Inductively Coupled plasma mass spectrometric (ICP-MS) analysis, 1g of the LBNL media can effectively remove 1mg of arsenate and about 0.2mg of arsenite. In the future, we will proceed to test the capacity of our media in real groundwater where inhibiting factors like phosphate are present and will design "ARUBA Up-flow Sand Filter" for domestic use.

Chamber Experiments to Develop a New Air Pollution Measuring Method. ELIZABETH DOMINGUEZ (Yakima Valley Community College Yakima, WA 98902) YANBO PANG (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

Whether indoors or out, the air we breathe contains particulate and gaseous pollutants that can adversely affect human health. Semi-volatile organic compounds (SVOCs), which come from incomplete combustion of organic compounds, exist in both particulate and gas phases. Many of these SVOCs are toxic. Previous methods to measure air pollutants like annular denuders are not sufficient to understand the effects of semi-volatile organic compounds. They are typically made of glass and are large, fragile, and costly. Foam denuder technique could potentially be good for collecting a range of hazardous species, especially semi-volatile organic compounds. The objective is to develop a foam denuder technique that is lightweight, simple, cost effective, accurate, and easy to use to collect gaseous pollutants. But in order to accomplish this, we needed to understand how SO₂ gas diffuses in Polyurethane foam and how well the foam absorbs SO₂. Polyurethane foam was used as the primary foam material in the experiments. Two general approaches were taken in consideration, foam thickness and pore size. For the foam thickness, 1/8 in. thick foam sheets were stacked to reach 0.5-5 in. high. Each thin foam layer was analyzed separately. For the pore size, 20ppi, 50ppi, 80ppi, and 110ppi (pores per inch) were used. In addition, different face velocities 5, 20, 40, and 100 (cm/sec) and different SO₂ concentrations ~0.01, ~0.1, and ~1 (ppm) were tested. Data on SO₂ collection for different foam thickness were used to derive the empirical model. Our results demonstrated that when we decreased the pore size (increasing ppi) of foam and decreased the face velocity it can help to improve the collection efficiency for gaseous pollutants. Overall, there was good correlation when we compared the SO₂ concentration measured by foam denuder vs. the SO₂ concentration measured by annular denuders. In conclusion, it was demonstrated that foam denuders could achieve 100% collection efficiency for gaseous pollutants. Future experiments will be done to test foam denuders for SVOC collection efficiency.

Development, Design and Deployment of Passive Samplers for Nicotine. ELIZABETH STEWART (University of California, Los Angeles Los Angeles, CA 94707) LARA A. GUNDEL (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

A passive sampling device for ETS was developed and tested for retention of nicotine and 3-ethenylpyridine vapor. Passive sampling is preferred over active sampling because of the compact size, minimal energy requirement and low cost of the samplers. The devices will be placed into the households of participants in a NIH-funded smoking intervention program. Due to the complex nature of ETS and high basicity of nicotine, measurement of urine cotinine (a metabolic byproduct of nicotine) levels may not be an accurate measure of ETS exposure. The reliability of cotinine as a biological marker for ETS will be determined. Correlation will be made between the level of ETS exposure and the severity of the participants' children's asthma. The passive sampler will provide a more accurate measure of ETS exposure and correct misclassification of exposure status. Tenax-filled thermal tubes were extensively tested in an environmental chamber for 250 minutes while three cigarettes were smoked. Tubes that gave poor results for nicotine retention were repacked with either old or new tenax and retested. The validated, standard method of active sampling with tenax-filled thermal tubes was employed concurrently for comparison. Results from old tubes and tubes repacked with new tenax agree with results from the active samplers. More tests must be done to determine if tubes repacked with old tenax are reliable enough for use in the field. Design and building of a device to deploy and expose the passive samplers in the field has taken place.

Effect of Ozone on Nicotine Desorption from Model Surfaces. SHARON LEE (University of California, Berkeley Berkeley, CA 94720) HUGO DESTAILLATS (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

Environmental Tobacco Smoke (ETS) can cause harmful respiratory diseases when present in enclosed spaces. Although ETS is composed of many different compounds, nicotine is used as its tracer. Due to nicotine's ability to sorb onto and desorb from different materials at different rates, its interaction with these materials must be further investigated. Therefore, desorption profiles of nicotine with household surfaces such as Teflon, cotton and wallboard is important to study. Using a 200-L chamber, nicotine desorption profiles were observed on these three surfaces. In order to test conditions similar to those present in ambient air, different humidity and ozone levels were also explored. All samples were collected using Tenax tubes and analyzed with a gas chromatographer. Preliminary results indicate nicotine desorption was significantly reduced in the presence of ozone under most experimental conditions. On cotton surfaces in humid air, the competition between ozone and water for reaction with nicotine on cotton surfaces and water's ability to react reversibly with nicotine led to higher concentrations of nicotine in the chamber. In addition, mechanisms proposed for ozone and nicotine reaction products supported this observation due to water's ability to also react with the pyrrolidinic ring. Unlike cotton, Teflon chamber experiments with humid and dry air showed the expected decrease in nicotine concentrations when ozone was added into the chamber. This observation was attributed to the hydrophobic nature of Teflon surfaces. Wallboard experiments showed a larger concentration of ozone was needed in order for a pseudo first-order reaction to occur. However, future experiments relating to wallboard must be investigated in order to compare its desorption profile with cotton and Teflon surfaces. Also, studies relating to water hydrogen bonding interactions with surfaces would be beneficial to understanding surface reactions of ozone, water, and nicotine.

Imaging Live Cells with Quantum Dots. SARAH CARTER (University of Illinois at Urbana Champaign Urbana-Champaign, IL 61820) DR. FANQING CHEN (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

Quantum dots are small semiconductor particles ranging in size from several nanometers to a few microns in diameter. The dots are spherical in structure with a special arrangement of electron shells that allows them to fluoresce. The luminescence emitted is non-bleaching, making them useful reagents for long-term in vivo studies. The surface of the nano-particles can be modified so that they can be linked to various other molecules, including water-soluble biomolecules. In order to develop a better reagent for detecting breast cancers, the quantum dot was linked to a DNA aptamer specific for breast cancer cells. The cells were then imaged using fluorescence microscopy.

Low Temperature Spectroscopy of ZnO Nanowires. CANDACE CHAN (Rice University Houston, TX 77005) SAMUEL MAO (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

ZnO is a direct, wide bandgap semiconductor with many interesting optical properties, such as room temperature excitonic recombination and UV photoluminescence and lasing capabilites. Recent advances in nanomaterial synthesis and characterization have suggested that ZnO nanowires may have potential use in nanoscale optoelectronics. Photoluminescence (PL) spectroscopy on ZnO nanowires synthesized by laser-assisted evaporation was conducted in order to study the optical properties of the nanowires at different temperatures. The nanowires were excited with a Nd:YAG laser (266 nm, 10 Hz, 6 ns) at constant pumping energy in a liquid helium cooled closed-cycle cryostat. PL spectra were taken at different temperatures from 12 K to room temperature. At low temperatures, well-defined emission peaks corresponding to donor-bound exciton and free-exciton recombination were observed at 3.342 eV and 3.306 eV. The first, second, and third order longitudinal optical phonon replicas were also observed at 3.231 eV, 3.161 eV, and 3.084 eV. With increased thermal energy, the peaks broadened and converged due to the decomposition of the bound-excitons into free-excitons. Room temperature PL was dominated by a broad free-exciton emission at 3.179 eV. The presence of the free-exciton emission at very low temperatures suggests that the nanowires synthesized were of high optical quality and have potential application for use in nanoscale optoelectronic devices.

Solubility and Speciation Studies of Manganese in Aqueous Manganite Solutions. DANIEL NIEPORT (Diablo Valley College Pleasant Hill, CA 94523) HEINO NITSCHE (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

Manganite (MnOOH), a manganese oxide mineral, has been shown to reduce highly soluble, aqueous mobile plutonium (VI) to relatively insoluble plutonium (IV). The physical characteristics of manganite which predict this redox reaction disagree with experiment. The conflict lies in that Mn2+ reduces Pu(VI) to Pu(IV) while in theory manganite is made of only Mn3+ ions that could reduce hexavalent plutonium by oxidation of Mn3+ to Mn4+. However, should the manganese oxidation occur, the formation of manganese dioxide, MnO2 would be observed. Manganese dioxide has a very low solubility and would precipitate as a solid. The formation of any solids other than manganite was not observed in the reported plutonium reduction experiments. The question that was attempted to answer by this research was if manganite solution that is in contact with air contains any Mn2+ in addition to Mn3+. The presence of Mn2+ in Pu(VI) solutions would explain the observed plutonium reduction. In this work, we determined the total aqueous concentration of manganese in equilibrium with the solid of manganite by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). We then developed three electrochemical techniques, anodic stripping linear scan voltammetry (ASLSV) and differential pulses anodic stripping voltammetry (DPASV) on a hanging mercury drop electrode (HDME), a sitting mercury drop electrode, and a rotating disk mercury film electrode (RDEMF) to determine whether any Mn2+ ions and at what concentration are in the supernatant aqueous solution that is in equilibrium with the solid manganite. The range of total manganese concentration varied with the pH of the manganite solutions, ranging from 5 x 10E-4 M to about 5 x 10E-9 M, for pH 4.6 and 9.4, respectively. The manganite solubility reached a minimum at about pH 8.7, which was below the detection limit of the ICP-OES. Once manganite's physical properties are properly defined, better predictions can be made about redox reactions with manganite and plutonium compounds. Understanding plutonium manganite interactions in nature will result in better management and cleanup of plutonium contaminated sites.