Carregant...
Tipus de document
TesiVersió
Versió publicadaData de publicació
Llicència de publicació
Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/126448
Micromotors for Environmental Applications
Títol de la revista
Autors
Director/Tutor
ISSN de la revista
Títol del volum
Recurs relacionat
Resum
[eng] Scarce supply of clean water and rising water pollution are key global challenges for water sustainability. Much of the wastewater generated by human agricultural and industrial activity is left untreated. Nanotechnological materials and systems have emerged as new tools for improving the efficiency of water treatment. Among those, self-propelled micromotors have shown several advantageous characteristics. Micromotors are autonomously propelled systems which either use chemical energy present in their environment or are propelled via external force fields. Diverse designs, materials composition and mechanisms of propulsion are reported for micromotors found in the literature. Among them, bubble-propelled micromotors, which move due to the generation and release of gas bubbles from their surface, are the main type of motors used for water remediation applications. In addition to the motion in fluids, the bubbles generated by the motors, also contribute with additional mixing of the fluid and enhance the mass transfer between active material and pollutant at the microscale. Additionally, the structure of micromotors can be modified to target a wide variety of pollutants, almost on demand. The micromotors that we synthesized during the research work for this thesis can remove organic and heavy metal pollutants, as well as exhibit bactericidal activity.
We studied Iron/Platinum (Fe/Pt) micromotors for their reusability, effect of sizes, swimming behaviors and catalytic properties. These micromotors were fabricated by spontaneous roll-up of iron and platinum nanomembranes, deposited on the pre-fabricated patterns of a photoresist substrate. The iron layer present as the outer surface of these micromotors can degrade organic pollutants via Fenton-like reaction and the inner platinum layer acts as the engine decomposing hydrogen peroxide to oxygen for bubble propulsion. We observed that Fe/Pt micromotors can swim continuously for hours, and can be stored for weeks before reuse, without sacrificing much of their activity. The results suggested that Fe/Pt micromotors act as a heterogeneous catalyst due to in situ generated iron oxide species on the surface, without leaching high concentration of iron in the media.
We developed graphene oxide-based micromotors (GOx-micromotors) for heavy metal removal, consisting of nanosized multilayers of graphene oxide, nickel, and platinum. These micromotors can capture, transfer, and remove heavy metals (i.e. lead) from contaminated water. GOx-micromotors are synthesized by electrodepositions of electro-reducible graphene oxide, nickel and platinum layers in the polycarbonate porous templates. The outer layer of graphene oxide captures lead on their surface, and the inner layer of platinum provides self-propulsion in hydrogen peroxide, while the middle layer of nickel enables external magnetic control of the micromotors. We observed that the mobile GOx-micromotors can remove lead 10 times more efficiently than non-motile GOx-micromotors, cleaning water from 1000 ppb down to below 50 ppb. We have demonstrated control of their motion and directionality in a proof of concept microfluidic system.
Silver nanoparticles (AgNPs) decorated Magnesium Janus micromotors were designed for disinfection and remove of Escherichia coli (E. coli) bacteria from contaminated water. Magnesium present in the micromotors functions as both, the template for the spherical shape and propulsion source by producing hydrogen bubbles while in contact with water. The inner layer of iron provides functionality for the magnetic remote guidance, and an outer AgNP coated gold layer facilitates adhesion of bacteria and gives bactericidal properties to the micromotors. We observed that the AgNPs-coated Au cap of the micromotors shows dual capabilities, capturing bacteria and killing them.
In our efforts to develop multifunctional micromotors and scalable synthesis methods, we developed two types of micromotors. (i) Mesoporous silica-based micromotors with manganese dioxide (MnO2) layer on the inner surface and coated with γ-Fe2O3 nanoparticles (FeSiMnOx micromotors). These micromotors can remove both organic and heavy metal pollutants, and they are synthesized using only template-assisted chemical methods. (ii) Cobalt ferrite micromotors (CFO micromotors) synthesized by template-free chemical synthesis approach. They are made up of aggregated cobalt ferrite nanoparticles, which act as the catalyst for propulsion and for Fenton-like reactions. We qualitatively measured the generation of hydroxyl radicals by CFO micromotors and studied the effect of surfactants on the degradation efficiency of CFO micromotors.
We hope that such approach of synthesizing micromotors via relatively facile methods will push the use of micromotors towards commercially practical solutions for water treatment. Overall, our results show that the multifunctional self-propelled micromotors have potential to become an effective tool for water remediation in the near future.
Matèries (anglès)
Citació
Col·leccions
Citació
PARMAR, Jemish. Micromotors for Environmental Applications. [consulta: 15 de desembre de 2025]. [Disponible a: https://hdl.handle.net/2445/126448]