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WhyteFerreira_52081900_2021.pdf
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- In this work, a robust fabrication method for stable mesoporous silicon membranes using standard microfabrication techniques is presented. Over the last three decades, the interest in porous silicon (PSi) has grown due to its highly tunable and remarkable properties that can be dramatically different from those of bulk silicon. The fabrication of porous silicon membranes (PSiM) is achieved by detaching the porous layer from the underlying bulk silicon substrate. The formation of this permeable barrier helps to overcome the infiltration limitations of close-ended PSi and allows its application to different fields, such as optical detection, drug delivery, microfluidics, energy conversion, and electronics. The application of interest in this work is enabling real-time optical biosensing. Due to the high reactivity of the hydride terminated surface species present on the porous silicon surface, the as-prepared matrix is not stable in aqueous solution. In order to passivate the PSi membrane and decrease the biosensor's limit of detection to competitive levels, atomic layer deposition was used to coat the porous matrix with different metal oxides, namely aluminum oxide (Al2O3), hafnium oxide (HfO2), and titanium oxide (TiO2). The fabricated membranes were characterized in terms of morphology, optical, mechanical, and chemical properties. Stability tests, resistance to flow analysis, and noise level determination were also performed. Finally, the biosensing performance of an Al2O3 passivated porous silicon membrane was tested through selective optical detection of bacteria lysate in phosphate buffered saline using PlyB221, an endolysin encoded by the bacteriophage Deep-Blue targeting the B. cereus. The biosensor was able to detect the bacterial lysate, with an initial bacteria concentration of 10E6 colony forming units per mL (CFU/mL), in less than 10 minutes.