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Browsing by Author "Serpe, Michael"

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    Characterizing returning polymers in hydraulic-fracturing flowback and produced water: Implications for colloid formation (includes associated erratum)
    (2021) Von Gunten, K.; Snihur, K. N.; McKay, R.; Kenney, Janice; Serpe, Michael; Alessi, Daniel S.
    Partially hydrolyzed polyacrylamide (PHPA) friction reducer was investigated in produced water from hydraulically fractured wells in the Duvernay and Montney Formations of western Canada. Produced water from systems that used nonencapsulated breaker had little residual solids (<0.3 g/L) and high degrees of hydrolysis, as shown by Fourier-transform infrared (FTIR) spectroscopy. Where an encapsulated breaker was used, more colloidal solids (1.1–2.2 g/L) were found with lower degrees of hydrolysis. In this system, the molecular weight (MW) of polymers was investigated, which decreased to <2% of the original weight within 1 hour of flowback. This was accompanied by slow hydrolysis and an increase in methine over methylene groups. Increased polymer-fragment concentrations were found to be correlated with a higher abundance of metal-carrying colloidal phases. This can lead to problems such as higher heavy-metal mobility in the case of produced-water spills and can cause membrane fouling during produced-water recycling and reuse.
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    Lipase-modified pH-responsive microgel-based optical device for triglyceride sensing
    (2015) Zhang, Qiang; Berg, Darren; Mugo, Samuel; Serpe, Michael
    Lipase-modified pH-responsive poly(N-isopropylacrylamide)-based microgels were synthesized. An optical device was subsequently fabricated by sandwiching the enzyme loaded responsive microgels between two thin Au layers, and their response to triolein, a model triglyceride, was investigated. The device's response depended on the triglyceride concentration, demonstrating its potential application as a triglyceride biosensor.
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    Optical devices constructed from ferrocene-modified microgels for H2O2 sensing
    (2016) Zhang, Qiang Matthew; Berg, Darren; Duan, Jiaqi; Mugo, Samuel; Serpe, Michael
    Ferrocene-modified poly(N-isopropylacrylamide)-based microgels were synthesized, characterized, and used to construct optical devices (etalons). The response of the microgels and etalons to H2O2 was investigated, and we show that both the microgel diameter and the optical properties of the etalons depend on the solution concentration of H2O2 from 0.6 to 35 mM. This behavior is a direct result of the oxidation of ferrocene, which influences the microgel diameter. This was also demonstrated by electrochemical-mediated oxidation/reduction of ferrocene using cyclic voltammetry. We go on to show that these materials could be used to monitor H2O2 that is generated from enzymatic reactions. Specifically, we show that the H2O2 generated from the oxidation of glucose catalyzed by glucose oxidase could be quantified. Finally, the devices can be reused multiple times via a regeneration process. This investigation illustrates the versatility of the etalon system to detect species of broad relevance and how they could potentially be used to quantify products of biological reactions.