Chemical Engineering

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Browsing Chemical Engineering by Author "Anderson, William A."

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    Development of nanocatalytic-based assay for the detection of an endocrine disrupting compound in aqueous solution
    (University of Waterloo, 2016-03-09) Bustami, Yazmin; Anderson, William A.; Moo-Young, Murray
    Endocrine disrupting compound (EDC) pollutants raise a concern among researchers as these pollutants are implicated in the increasing incidence of testicular, breast and thyroid cancers. Some of these chemicals are widely used for plastics production and discharged into the water system as industrial effluents that could harm the ecosystem as well as plant, animal and human life. Thus, rapid detection and quantification of EDCs in water is desired for screening and investigative purposes. For this purpose, nanoparticle-based methods appear to be potentially efficient, quick and cost-effective techniques to rapidly assess this toxic pollutant. The main focus of this study was to synthesize heterogeneous nanoparticles, iron oxide/gold nanoparticles (IONPs/AuNPs) and to manipulate their synergistic effects for the development of a nanoparticles-based assay, specifically for the EDC compound, 17β-estradiol. As the first step, IONPs and AuNPs were synthesized separately and heterogeneous nanoparticles were formed by a simple electrostatic- self- assembly technique. The unique physiochemical properties of this hybrid nanoparticle were investigated as a supporting material for biomolecules, as well for its intrinsic peroxidase-like activity using a hydrogen peroxidase dependent system. The formation of the IONPs/AuNPs was verified using several characterization tools such as UV-Vis spectrophotometry, Dynamic Light Scattering (DLS), Transmission Electron Microscope (TEM), Energy Dispersive X-ray (EDX) and X-ray Photoelectron Spectroscopy (XPS). The diameter calculated from TEM was 16.1 ± 11.1 nm and EDX confirmed the presence of the Fe and Au elements. From a heterostructural analysis using HRTEM and XPS data, an alloy-like morphology (Fe/Au) was suggested for the heterogeneous nanoparticles, rather than a core-shell structure. The Fe/Au nanoparticles showed good potential for the basis of a colorimetric assay for glucose detection using glucose oxidase immobilized on the Fe/Au surface. In addition, the Fe/Au nanoparticles also showed a significant peroxidase-like activity. A nanocatalytic-based assay was developed by modifying the nanoparticles surface with an aptamer in order to specifically “capture” the target molecule, 17β-estradiol. The formation of a Fe/Au-17β-estradiol complex significantly hampered the peroxidase-like catalytic activity resulting in the development of a unique nanosensor system based on the extent of loss of peroxidase activity. Development of the nanocatalytic-based assay suggests the potential application of Fe/Au nanoparticles to capture, separate and detect a selective target as well as a basis for the development of a rapid, simple and reliable detection tool. The heterogeneous Fe/Au nanoparticles show a remarkable synergistic property for application in nanosensor system. Therefore, some of the work presented here can be extended in certain major directions such as heterostructure formation and optimization of nanocatalytic-based assay.
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    Evaluation of antimicrobial coatings in wet conditions and development of sulphonated poly (ether ether ketone) - copper composites for antimicrobial applications
    (University of Waterloo, 2020-08-06) Muralidharan, Sanjay Krishna; Zhao, Boxin; Anderson, William A.
    The existence of pathogenic bacteria and fungi on surfaces can be a serious threat to health causing numerous infections. With microorganisms developing antimicrobial resistance over the years, there is an increasing need to develop surfaces that can kill or inhibit the growth of bacteria and fungi. Antimicrobial coatings have been tested as an effective solution to battle hospital-acquired infections, which are one of the leading causes for patient morbidity and mortality. Aereus Technologies has been working on developing a coating consisting of marine paint and biocidal copper-alloy based microparticles that can render surfaces antimicrobial. One of the key concerns for this new coating is that the microparticles are expected to oxidize when exposed to human palm sweat or disinfection agents in healthcare settings. To investigate this possibility, the antimicrobial efficacy and durability of this coating was evaluated under exposure to different saline environments (artificial ocean water and artificial sweat environment) and a strongly oxidizing environment (hydrogen peroxide). From the experiments, it was observed that regular painted and marine painted samples with proprietary “Aereus shield” particles have the ability to survive harsh oxidizing conditions without losing their antimicrobial properties. The antimicrobial application of copper was extended to the synthesis of sulphonated poly (ether ether ketone) (SPEEK) and copper composite films as promising antimicrobial materials. The effects of fabricating surface structures (micro-pillars) on the films were investigated. The synthesized films were systematically characterized and it was observed that both SPEEK and SPEEK – Cu films possessed antimicrobial properties which initially demonstrated over 4 log reduction of E. coli within 15 minutes of contact. Over longer times as the films aged, the SPEEK – Cu film still achieved over 2 log (for flat film) and 4 log (for micro-pillared film) reduction of E. coli within 1 hour of contact and showed significant fungal growth reduction for Saccharomyces cerevisiae (yeast) and Aspergillus niger after 2 hours of contact. Micro-pillared films had a larger water contact angle (131°) in comparison to flat films (64°), indicating that they were hydrophobic. These micro-pillared films also showed better antimicrobial properties and more copper release than flat films, due to better exposure of copper particles on the top surface of the micro-pillars. The synthesized films were also thermally stable up to 300°C and exhibited tensile strengths ranging from 50 – 160 MPa depending on the surface morphology and copper content. Furthermore, the films were found to be recyclable by dissolution in sulphuric acid and re-casting to form new films with replenished sulphonic acid groups in the polymer matrix and restored antimicrobial properties.