Browsing by Author "Yin, Yiyuan B."

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    Microencapsulated Photoluminescent Gold for ppb-Level Chromium(VI) Sensing
    (American Chemical Society, 2019) Yin, Yiyuan B.; Coonrod, Christian L.; Heck, Kimberly N.; Lejarza, Fernando; Wong, Michael S.; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment
    Luminescent gold nanoclusters (Au NCs) are a promising probe material for selective chemical sensing. However, low luminescent intensity and an incomplete understanding of the mechanistic origin of the luminescence limit their practical implementation. We induced glutathione-capped Au NCs to aggregate within silica-coated microcapsular structures using polymer-salt aggregate self-assembly chemistry. The encapsulated NCs have a 5× luminescence enhancement compared to free Au NCs and can detect Cr(VI) at concentrations as low as 6 ppb (=0.12 μM CrO42-) through luminescence quenching, compared to free Au NCs, which have a limit of detection (LOD) of 52 ppb (=1 μM CrO42-). The LOD is 16× lower than the United States Environmental Protection Agency maximum contaminant level for total chromium (Cr(III) + Cr(VI), 100 ppb) in drinking water. No pH adjustment is needed using the encapsulated Au NCs, unlike the case for free Au NCs. The luminescent microcapsule material can sense Cr(VI) in simulated drinking water with a ∼20-30 ppb LOD, serving as a possible basis for a practical Cr(VI) sensor.
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    Treating Water by Degrading Oxyanions Using Metallic Nanostructures
    (American Chemical Society, 2018) Yin, Yiyuan B.; Guo, Sujin; Heck, Kimberly N.; Clark, Chelsea A.; Coonrod, Christian L.; Wong, Michael S.; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment
    Consideration of the water–energy–food nexus is critical to sustainable development, as demand continues to grow along with global population growth. Cost-effective, sustainable technologies to clean water of toxic contaminants are needed. Oxyanions comprise one common class of water contaminants, with many species carrying significant human health risks. The United States Environmental Protection Agency (US EPA) regulates the concentration of oxyanion contaminants in drinking water via the National Primary Drinking Water Regulations (NPDWR). Degrading oxyanions into innocuous compounds through catalytic chemistry is a well-studied approach that does not generate additional waste, which is a significant advantage over adsorption and separation methods. Noble metal nanostructures (e.g., Au, Pd, and Pt) are particularly effective for degrading certain species, and recent literature indicates there are common features and challenges. In this Perspective, we identify the underlying principles of metal catalytic reduction chemistries, using oxyanions of nitrogen (NO2–, NO3–), chromium (CrO42–), chlorine (ClO2–, ClO3–, ClO4–), and bromine (BrO3–) as examples. We provide an assessment of practical implementation issues, and highlight additional opportunities for metal nanostructures to contribute to improved quality and sustainability of water resources.