High-Speed Sensing And Removal of Environmental Harmful Factors Using Nano-Hierarchical Structure

Abstract

In the chapter 1, the three anionic species; Chloride (Cl-), sulfate (SO42-), and carbonate (CO32-), are typical chemical factors that environmentally accelerate failure of concrete structures with steel structure through long-term exposure. Efficient removal of these deleterious anions at the early stage of penetration is crucial to enhance the lifespan and durability of concrete structures. Here, we synthesize CaFe-layered double hydroxide (CaFe-LDHs) by a simple one-step co-precipitation technique and CaFe-based metal oxide originated by the CaFe-LDHs via structural modulation, and apply them for the removal of chloride, sulfate, and carbonate anions as well as corrosion inhibition on steel structure in aqueous solutions. In the chapter 2, wastewater from industries can contain excessive nitrate and phosphate anions to cause eutrophication of lakes and rivers. The calcium iron-based layered double hydroxides (CaFe-LDHs) can improve immobilization the migration of phosphate anions in anti-eutrophication. In this study, we developed an efficient structure for the selective uptake of nitrate and phosphate anions in aqueous solution on CaFe-LDHs. We also discuss removal mechanism of anions by the CaFe-LDHs related with structure modulation variation that happens during calcination process.

In the chapter 3, A suitable methanol sensor workable in ambient temperature conditions with a high response has gained wide interest to prevent detrimental consequences from its low-level intoxication. In this work, we present a tunable and highly responsive ppb-level methanol gas sensor device working at room temperature, using an exfoliated graphene sheet (EGs) and ZnO quantum dots (QDs) on an aluminum anodic oxide (AAO) template. It is verified that EGs-supported AAO with a vertical electrode configuration enabled high and fast-responsive methanol sensing.

In the chapter 4, a highly sensitive non-enzymatic electrochemical glucose sensor of copper oxide nanowires-nickel iron layered double hydroxide (CuO NWs-NiFe LDHs) was fabricated in a bottom-up synthetic approach. We systematically modified and tuned the surface complexity of CuO NW-NiFe LDHs by changing the oxygen partial pressure, temperature, time, coating thickness, and compositional ratio. As a result of electrochemical measurement using cyclic voltammetry and amperemetry techniques, a glucose sensor that can be operated even at high sensitivity and low voltage was developed due to the fine shape control of the hierarchical nanostructure.