Browsing by Author "Villarreal, Eduardo"

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    Communicating Science Concepts to Individuals with Visual Impairments Using Short Learning Modules
    (American Chemical Society, 2016) Stender, Anthony S.; Newell, Ryan; Villarreal, Eduardo; Swearer, Dayne F.; Bianco, Elisabeth; Ringe, Emilie
    Of the 6.7 million individuals in the United States who are visually impaired, 63% are unemployed, and 59% have not attained an education beyond a high school diploma. Providing a basic science education to children and adults with visual disabilities can be challenging because most scientific learning relies on visual demonstrations. Creating resources to help teachers and service organizations better communicate science is thus critical both to the education of sighted students as well as to the continuing education of individuals with blindness or low vision (BLV). Here, 4 new scientific learning activities that last 5–15 min each are described. These simple exercises are designed to educate the general public, including both those who are sighted and those with BLV. The modules use tactile and auditory approaches to convey basic concepts including the metric system, material strength and deformation, transparency, and the electromagnetic spectrum. These modules were tested on 20 adults with BLV during a science outreach event. Answers to learning assessment questions indicate that the modules conveyed information about the scientific concepts presented and increased an interest in science for most participants.
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    Investigation of Light-Matter Interactions in Nanomaterials via Correlated Optical-Electron Microscopy
    (2018-08-10) Villarreal, Eduardo; Ringe, Emilie
    Nanomaterials have become more relevant in several sectors (environmental, energy storage, nanomedicine, etc) over recent years, where their unique properties compared to bulk are exploited. The difference in surface area is one of the reasons nanomaterials display tailorable chemical, mechanical, and physical properties due to extremely small grain size. Unfortunately, the properties of most of the nanomaterials are still to be characterized due to the need of precise instrumentation, preventing from making them convenient for consumer/industry applications. This thesis addresses the study and understanding of the relationship of nanomaterials’ optical properties and their physical structure, as well as the creation of protocols to facilitate characterization. By understanding this relationship, nanomaterials can be tailored to exploit their properties for many applications in many sectors. Based on this premise, two different systems were studied and correlated. First, the sensitivity-structure correlation of gold nanoparticles (NPs) for biosensing applications is studied. In such study, a single-nanoparticle approach was used, and statistical models were applied to correlate the refractive index sensitivity of gold NPs with their shape and size. Based on such correlation, rounder NP resulted to be more sensitive to surface events, providing insights on particle selection for biosensors. Furthermore, the nanoparticles were functionalized as DNA sensors as a proof of concept. Next, the Micro Extinction Spectroscopy development is described, as well its use as an analytical tool to study the influence of defects in 2D semiconductors. With such tool, a monolayer transition metal dichalcogenides library was create by detecting excitons with their local absorption. Finally, monolayer MoS2 was treated by both oxygen plasma exposure and hydrogen treatment to create defects and alter its band gap. The material was characterized before and after the treatment using optical spectroscopy, and information about its composition, bandgap, and optical response was revealed. In sum, the projects presented here are unified by the need for structure-function correlations, which are achieved with optical spectroscopy and electron microscopy.
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    Micro-Extinction Spectroscopy (MExS): a versatile optical characterization technique
    (Springer, 2018) Kumar, Anjli; Villarreal, Eduardo; Zhang, Xiang; Ringe, Emilie
    Micro-Extinction Spectroscopy (MExS), a flexible, optical, and spatial-scanning hyperspectral technique, has been developed and is described with examples. Software and hardware capabilities are described in detail, including transmission, reflectance, and scattering measurements. Each capability is demonstrated through a case study of nanomaterial characterization, i.e., transmission of transition metal dichalcogenides revealing transition energy and efficiency, reflectance of transition metal dichalcogenides grown on nontransparent substrates identifying the presence of monolayer following electrochemical ablation, and scattering to study single plasmonic nanoparticles and obtain values for the refractive index sensitivity and sensing figure of merit of over a hundred single particles with various shapes and sizes. With the growing integration of nanotechnology in many areas, MExS can be a powerful tool to both characterize and test nanomaterials.