Jean D Nelson

Engineer Research and Development Center - U.S. Army, Mississippi, United States

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Publications (5)7.62 Total impact

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    ABSTRACT: Nanoporous silica gel was employed to extract uranyl from contaminated soil and to enhance the fluorescence intensity and lifetime. The fluorescence lifetime and intensity of uranyl ions absorbed within nanoporous silica gel was measured from pH 1-13. The results show that the uranyl fluorescence intensity can be enhanced by approximately two orders of magnitude by the silica nanoporous matrix from pH 4-12 with the greatest enhancement occurring from pH 4-7. The enhanced fluorescence lifetime can be used in time-gated measurements to help minimize the influence of background environmental fluorophores.
    Journal of Fluorescence 01/2011; 21(1):119-24. · 1.79 Impact Factor
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    ABSTRACT: The comprehensive goal of this research is the synthesis and characterization of nanomaterials that are spectrally tunable in terms of their electromagnetic signal, are robust, magnetic (allowing their piloted movement), and have the potential to be functionalized for the detection of CBRNE threats. Various chemical methods were utilized for synthesis of magnetic (iron) and luminescent rare earth (RE) components, and their mixtures. Effects of integrating an iron core into RE luminescent lattices (excited by UV, emit in the VIS) were investigated. The determination of the optimum balances between magnetic and luminescent components such that the magnetism was maximized while maintaining acceptable fluorescence integrity will be discussed. The emphasis of this work is focused on developing a distributed sensor suitable for use in the terrestrial environment. The robust properties of using a RE luminescent shell would allow the particles to be resistant to photobleaching. Additionally the chemical stability of the RE shell would allow operation in a variety of p H conditions. The magnetic core will ultimately allow the distributed particles to be recollected.
    Journal of Applied Physics 06/2010; · 2.21 Impact Factor
  • Lemont B Kier, Cho-Kun Cheng, Jean D Nelson
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    ABSTRACT: A series of models using cellular automata (CA) are created to examine the influences on the phenomenon of solute aggregation. The models used the variations in hydropathic states of the solutes to produce changes in the clustering patterns. It was found that an increase in the hydrophobic character of the solute molecules led to greater aggregation. The effect of concentration of solutes was also modeled. These preliminary models of solute aggregation serve as the basis for subsequent models relative to both biological receptor interactions, and the fate and transport of environmental contaminants of interest.
    Chemistry & Biodiversity 04/2009; 6(3):396-401. · 1.81 Impact Factor
  • Lemont B Kier, Cho-Kun Cheng, Jean D Nelson
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    ABSTRACT: A cellular automata (CA) model of liquid water has been used to study self-diffusion and the diffusion of a solute. The influences of temperature and solute hydropathic state are modeled as variables in this process. The self-diffusion model correlates very well with earlier experimental data. The diffusion of a solute experiences variation with temperature and its hydropathic states. These influences are found to relate to models of free hydroxy groups and the average cavity cluster size in bulk water. These preliminary models serve as the basis for modeling solute diffusion for specific contaminants of interest (such as heavy metals like uranium) in a water system, and addressing its migration patterns with water relative to temperature.
    Chemistry & Biodiversity 04/2009; 6(3):295-302. · 1.81 Impact Factor
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    ABSTRACT: A passive signal enhancement device for the standoff detection of uranium in soil was developed and tested. The device consists of a spherical ball lens half-coated with a polymer–silica gel composite. The nanoporous silica gel, when placed in contact with moist soil, absorbs water and dissolved uranyl ions and significantly enhances the fluorescence intensity of the uranyl. The ball lens focuses the UV excitation energy to the focal point of the lens located within the silica gel layer and directs the resulting fluorescence signal back towards the excitation source. Our results show that this ‘Directed Fluorescence’ (DF) device can be used to enhance the uranyl fluorescence signal intensity by more than 200 times. Consequently, the maximum standoff detection distance is increased by more than an order of magnitude.
    Sensors and Actuators B: Chemical. 01/2009;