Developing Methodology to Prepare a Nanoparticle Coated Crystal for Infrared Analyses

Engineering: 2nd Place (The Ohio State University Denman Undergraduate Research Forum)The widespread use of nanomaterials demonstrates a tremendous benefit to society; however, as nanomaterials are inevitably introduced to the environment, it is unknown how their compositions and coating agents alter in different settings and over a prolonged period of time. Coating agents are applied either during or post synthesis to prevent aggregation. Tracking changes to the molecules that coat the surface of nanomaterials is imperative to understanding the inherent risk when nanomaterials are released to the environment. The purpose of my research is to develop a method to prepare a nanoparticle coated crystal for infrared (IR) analyses in order to specifically identify changes to molecules that coat the surface. The two nanomaterials analyzed in this study were hematite and nanosilver. Citrate was the primary coating agent used on both materials. The particles were coated to IR crystals and the coating layers were evaluated under static and dynamic conditions. Variables included coating agent (water, citrate, phthalic acid) and pH. Previously collected data from batch adsorption experiments of citrate and phthalic acid on hematite were used to validate the static system method for hematite. The static experiments successfully detected the adsorption of citrate on the surface of both hematite and nanosilver. The largest issue involved resolving the spectra; specifically, removing the IR absorption of water. This presence of water proved to be an even greater obstacle in the flow-through cell; however, the most successful method involved subtracting water spectra from each component before resolving. No spectra were obtained from silver perhaps due to the silver not adhering to the flow-through cell surface. Significant progress has been made and once the influence of water is removed, these processes should have a vast potential for further research to determine specific changes to nanoparticle surfaces, particularly with the flow-through cell for greater control over variability.Academic Major: Environmental Engineerin

Point of Zero Charge: Role in Pyromorphite Formation and Bioaccessibility of Lead and Arsenic in Phosphate-Amended Soils

Soluble lead (Pb) can be immobilized in pure systems as pyromorphite through the addition of phosphorus (P) sources; however, uncertainties remain in natural systems. Knowledge of point zero charge (PZC) is important to predict the ionization of functional groups and their interaction with metal species in solution. This study utilized Pb- and As-contaminated soils to determine the combined effect of pH with respect to PZC and different rates of P-application on pyromorphite formation as well as Pb and arsenic (As) bioaccessibility as impacted by speciation changes. Solution chemistry analysis along with synchrotron-based Pb- and As-speciation as well as bioaccessibility treatment effect ratios (TERs) were conducted. Results indicated no significant effect of PZC on pyromorphite formation in P-amended soils; however, the TERPb appeared significantly lower at pH > pHPZC and higher at pH < pHPZC (α = 0.05). In contrast, the TERAs was significantly higher at pH > pHPZC compared to the other two treatments for the tested soils. The lack of conversion of soil Pb to pyromorphite may be attributed to several reasons including the presence of highly stable minerals, such as plumbojarosite, limiting soluble Pb availability to react with phosphates, high Fe and S content in IKS, high organic matter in BO, and high Ca content in NW

Performance Modeling of Multi-Tier PCS System

The emergence of multi-tier wireless access is being driven by the different compromises in technology required to provide wireless service in different environments. Three major tiers of wireless access are likely to emerge to provide Personal Communications Services (PCS): high-tier, low-tier, and unlicensed. Because of the service costs of the three tiers, the unlicensed system is given the highest priority to deliver the calls, and the high-tier system has the lowest priority to deliver the calls. To maintain this delivery priority, two multi-tier mobility management schemes have been proposed: the single registration scheme (SR) and the modified multi registration scheme (MR). This paper studies the performance of these two schemes. We show that the registration cost of SR is always no less than the cost of MR. The advantage of MR over SR is more significant if (i) when the user moves into the low-tier system, it is more likely that the currently visited low-tier VLR is the same a..

Design and Evaluation of Signaling Protocols for Mobility Management in an Integrated IP Environment

NoIn the future mobile network, satellites will operate alongside cellular networks in order to provide seamless connectivity irrespective of the location of the user. Such a service scenario requires that the next generation of mobility management (MM) procedures are able to ensure terminal and user mobility on a global scale. This paper considers how the principles of Mobile-IP can be used to develop MM procedures for a heterogeneous access network, comprizing of satellite and cellular elements, connected to an IP core network.Initially, the system architecture is described. This is followed by a discussion of issues related to MM, where location, address and handover management are considered. A description of the signaling protocols for macro-mobility using Mobile-IP is then presented, emphasizing the need to minimize the change to the existing access network procedures. Finally, the performance of the protocols is analyzed in terms of the additional signaling time required for registration and handover

X‑ray Analyses of Lead Adsorption on the (001), (110), and (012) Hematite Surfaces

Predicting the environmental fate of lead relies on a detailed understanding of its coordination to mineral surfaces, which in turn reflects the innate reactivity of the mineral surface. In this research, we investigated fundamental dependencies in lead adsorption to hematite by coupling extended X-ray absorption fine structure (EXAFS) spectroscopy on hematite particles (10 and 50 nm) with resonant anomalous X-ray reflectivity (RAXR) to single crystals expressing the (001), (012), or (110) crystallographic face. The EXAFS showed that lead adsorbed in a bidentate inner-sphere manner in both edge and corner sharing arrangements on the FeO₆ octahedra for both particle sizes. The RAXR measurements confirmed these inner-sphere adsorption modes for all three hematite surfaces and additionally revealed outer-sphere adsorption modes not seen in the EXAFS. Lead uptake was larger and pH dependence was greater for the (012) and (110) surfaces, than the (001) surface, due to their expressing singly- and triply coordinated oxygen atoms the (001) surface lacks. In coupling these two techniques we provide a more detailed and nuanced picture of the coordination of lead to hematite while also providing fundamental insight into the reactivity of hematite