Water quality monitoring in Canada is essential to providing safe water to all. Indigenous and remote communities, many of which are under boiling drinking water advisories, lack availability and/or funding to water monitoring resources. A low-cost, point-of-care detection mechanism has been proposed for the detection of aqueous ammonia and protozoan parasites, which affect the safety of a source of water. An ammonia fluorescence responsive hydrogel, based on the fluorescence quenching of rare earth metal Europium (Eu3+) upon contact with aqueous ammonia, has been proposed to be incorporated into a microfluidic device, which utilizes shadow imaging and flow analysis to detect parasitic (oo)cysts of Cryptosporidium and Giardia, two of the most prevalent protozoan parasites which cause gastrointestinal illness around the world. Fabrication of the ammonia sensitive hydrogel was completed, and the essential components to the ammonia sensitivity were determined. Chemical analysis and solvent modifications found that Formamide is the essential solvent to maintain ammonia sensitivity. A literature review into the current detection mechanisms of Cryptosporidium and Giardia was completed to provide a reference and starting point for the development of the low-cost, point-of-care device proposed in this thesis. Baseline images of Cryptosporidium parvum and Giardia lamblia were captured to provide a reference for the development of a particle tracking algorithm to be used in the microfluidic device. The images captured highlight morphological features essential to developing a tracking mechanism based on the morphology of the (oo)cysts. / Thesis / Master of Science in Biomedical Engineering / Water quality monitoring for remote and Indigenous communities is needed to provide safe water to all. Detection of aqueous ammonia by fluorescent hydrogel, and parasitic cysts by flow analysis, provides a low-cost, point-of-care detection mechanism. A fluorescence responsive hydrogel for aqueous ammonia detection was produced and the essential components for ammonia responsiveness were determined. Detection mechanisms of parasites Cryptosporidium and Giardia, two of the most prevalent parasitic protozoans causing human gastrointestinal illness, were analyzed and compared. Baseline images of the parasitic (oo)cysts were captured by conventional microscopy for the training of particle tracking algorithms to be implemented into a microfluidic device. The microfluidic device detection mechanism will utilize shadow imaging and flow analysis to detect parasitic (oo)cysts.

Les températures classiques de fonctionnement de la plupart des capteurs chimiques de gaz sont généralement supérieures à 300°C, ce qui ne représente pas les conditions favorables de leur fonctionnement en termes de stabilité, répétabilité et consommation énergétique. Pour ce, dans ce travail, nous avons développé une nouvelle méthode d’élaboration par voie sol-gel des couches minces à base de dioxyde d’étain(SnO2) sensibles à la détection de l’ozone et de l’ammoniac à température ambiante et à l’état de traces. L’ajustement des paramètres expérimentaux relatifs à ce procédé (solvant, concentration du dispersant, température et temps de recuit,…) a permis d’optimiser les conditions de préparation des couches minces et par la suite de contrôler les caractéristiques chimiques et texturales des couches sensibles développées. Dans cette étude les précurseurs du SnO2 ont été préparés selon deux approches.[...]Les résultats de détection de gaz ont montré qu’à l’inverse des couches élaborées par voie aqueuse qui sont quasiment insensibles à l’ozone, le procédé sol-gel en milieu alcoolique a permis de développer des couches très sensibles à ce gaz à des teneurs de l’ordre de 60 ppb, inférieures au seuil limite autorisé qui est de 75 ppb. L’originalité de ce travail porte sur le fait que les couches développées permettent la détection de O3 à température ambiante, ce dont aucune étude antérieure ne faisait état à l’origine de ce travail. Pour l’ammoniac, les deux voies de synthèse ont permis d’élaborer avec succès des capteurs sensibles à ce gaz, à température ambiante. La concentration minimale détectée de l’ordre de 5 ppm est inférieure aux 16,7 ppm correspondant au niveau maximum autorisé pour la détection olfactive par l’humain. Les performances de détection des deux gaz cibles, à température ambiante, ont été améliorées par addition dans les sols d’étain de surfactant (TX-100). En effet, les réponses des couches déposées en présence de surfactant ont été multipliées par un facteur 1,5 pour l’ozone et de 2 pour l’ammoniac, comparées avec celles des capteurs SnO2 sans additif.[...] / The conventional operating temperatures of most chemical gas sensors are generally above 300°C, which are not favorable to their functioning in terms of stability, repeatability and energy consumption. For this reason, in this study, we have developed a new method of thin film synthesis via sol-gel process, based on tin dioxide (SnO2) sensitive detection of very low ozone and ammonia concentrations at room temperature (RT). The adjustment of the experimental parameters (solvent, concentration of dispersant, temperature and annealing time,...) has been optimized for the preparation of SnO2 thin films highly sensitive to these target gases at RT. The precursors of SnO2 were prepared using two approaches. The first one is a synthesis pathway in which an aqueous solution of tin tetrachloride (SnCl4) is neutralized with an aqueous solution of ammonia (NH3, H2O). The second one consists of a synthesis of tin(IV) tetraethoxide by organic way via an alcoholysis reaction of anhydrous SnCl4 in absolute ethanol in the presence of triethylamine. To better control the texture of SnO2 layers obtained by this last route, small amounts of surfactant TX-100 were added to the alcoholic sol. The results particularly highlighted the importance of the nature of the solvent, annealing conditions and the concentration TX-100 on the composition and morphology of sensitive layers. This study showed that the materials synthesized by alcoholic way (SnO2(al)) have crystallites size more important than those prepared by aqueous method (SnO2(aq)), but most especially, the SnO2(al) surface is weakly hydrated, compared to that of SnO2(aq). Moreover, the microscopic analysis revealed evident differences between the two layer morphologies. In fact, the SnO2(al) films exhibit porous nanostructures whereas the SnO2(aq) layer rather appeared as a continuous film with a low porosity. The electrical responses showed that both kinds of sensitive layers enabled the detection of ozone but the sensitivity was higher for the SnO2(al) layers compared to that of SnO2(aq) thin films. The alcoholic sol–gel process enabled the development of very sensitive layers to ozone, working at ambient temperature since concentrations lower than 60 ppb were detected. This value is lower than the limit ozone detection threshold which is 75 ppb. As regards the sensitivity to the ammonia, both synthesis ways enabled its detection at room temperature. The minimum concentration detected was 5 ppm, which is less than 16.7 ppm, corresponding to the maximum level allowed for olfactive detection. In addition, it was demonstrated that the performance of ozone and ammonia detection at room temperature, was improved by the addition of surfactant (TX-100) in the organic sol. Indeed, the sensitivities of SnO2(al) layers prepared in the presence of TX-100 were multiplied by 1.5 and 2 for ozone and ammoniac respectively compared to those of SnO2(al) sensors without additive. The results of the physico-chemical characterization and the electrical responses using both layers led to the proposition of ozone and ammonia detection mechanisms using tin dioxidebased gas sensors.Finally, the development, by a simple and inexpensive sol–gel method, of novel tin dioxidesensors able to monitor ozone and ammonia gases at room temperature, was successfullyachieved. This original and multidisciplinary study, presents new and original results concerning the detection of ozone and ammonia whose detection was up to now reported to be possible at trace levels only by using metal oxide-based sensors working at high temperatures. This approach shed new light on fabricating toxic gas sensors based on metal oxides operating at room temperature.