Applications Of Functionally Inorganic-Organic Nanocomposites In Ultramicroelectrode Electrochemical Analysis

In recent years, food safety, health and other life issues has aroused more and more attention. In the process of working on these issues, it will involve research on the life behavior and specific molecular mechanism, but the key to solving these problems lies on studying changes of important bioactive molecules in vivo in content. For most biologically active molecules such as reactive oxygen species, the reasonable concentration helps to sustain life, eliminating inflammation; too high or too low content will destroy the cell structure, affecting the normal metabolic activities, and even cause diseases. Therefore, determination of these active substances in vivo has a very important significance. Currently, fluorescence, electrochemistry, chromatography and other methods can achieve detection of these substances. Among them, with low cost, high sensitivity and simple instruments, the electrochemical method has been widely used. And the emergence and development of ultramicroelectrodes (UMEs) provide a broader space for electrochemical detection. UMEs have small size, high mass transfer rate, high sensitivity, and high spatial and temporal resolution and can be inserted directly into the cell or organism to detect active substances, reducing damage to living cells or organisms.In order to fabricate UMEs to detect active species in living cells or an organism, this paper designed a simple, green method. On this basis, using layer-by-layer self-assmbly and modification, we successfully fabricated UMEs with high sensitivity and selectivity to detect intracellular reactive substances. The full text is divided into four parts, as follows:Chapter 1. OverviewIn Chapter 1, we elaborated the features of UMEs, classification, preparation method and application, focusing on the fabrication and applications of UMEs. We also highlight the characteristics of inorganic/organic functional nanomaterials and applications in ultramicroelectrode. Moreover, we summarizes the formation and detection of reactive oxygen species. In the end, we emphatically pointed out the significance and main contents of our research.Chapter 2. In situ synthesis of poly(ionic liquid)-Pt nanoparticle composite in glass capillary for the electrocatalytic reduction of oxygenA novel approach for in situ synthesizing poly(ionic liquid)-Pt nanoparticle (PIL-Pt) composite in a glass capillary for fabricating filling-type electrode is reported in this work. XRD and TEM were used to characterize the as-synthesized PIL-Pt composite. Because of the modification of poly(ionic liquid)s (PILs), the PIL-Pt composite can not only be dispersed well to form a homogeneous suspension of Pt nanoparticles, but also be synthesized directly in a glass capillary with a tip radius ranging from 250 nm to 2.5 mm. By simple heating at 130 ℃, the PIL-Pt composite capillary electrode was fabricated under mild conditions. With the advantages of both PILs and glass capillary, a PIL-Pt capillary electrode can provide a favourable microenvironment for the encapsulated Pt nanoparticles and promote the mass transfer rate; thus, showing a high electrocatalytic activity and stability for an oxygen reduction reaction (ORR). The present study provided a novel method for the development of high performance electrocatalysts based on the construction of PIL-Pt composite in a glass capillary for fuel cell or electrochemical sensors.Chapter 3. Fabrication and Electrochemical Behavior of Tungsten NanoelectrodeIn this work, we have developed a simple and green method to fabricate dimension controllable tungsten (W) nanoelectrode by electrochemical etching hybrid insulation. By controlling the concentration of etching solution and etching potential, we obtained W nanoneedle with smooth surface morphology. The nanoneedles and nanoelectrodes can be characterized by the SEM, TEM and steady-state cyclic voltammetry. Experimental results show that:W wire (Φ=15 μm) can be etched into a nanoneedle with radius of～8nm at 1.7 V and in 0.5 M NaOH; the hybrid insulation film of the external electrode was uniform and thin about～30 nm, so after insulating, the overall size of the electrode tip can keep in nanosized level, reducing the electrode edge effects. And we also study the electrochemical behviors of W nanoelectrodes in two standard systems, K3Fe (CN)6 and Ru (NH3)6Cl3, cyclic voltammetry has a good "S" morphology, and limited steady-state currents can be used to accurate the effective radius of the electrodes and to study the dynamic behavior of W nanoelectrode, such as transfer coefficient (a), heterogeneous electron transfer rate constant (k°) and other kinetic parameters. Moreover the effective radius of the nanoelectrodes can be controlled and the electrodes showed good stability.Chapter 3. Detection of Hydroxyl Radicals in Single Cell with HAT-functional Gold Nanoparticle-sheathed Tungsten NanoneedleIn the present work, we fabricated smooth tungsten (W) nanoneedles with radius of～8 nm. By layer-by-layer assembly method, gold nanoparticles were modified on W nanoneedles and hexanethiol (HAT) was further modidied through Au-S bond, obtaining hexanethiol functionalized and gold nanoparticles modified W nanoneedle (HAT/Au NPs/W). And we used SEM, TEM to characterize the probes, and with the help of a microscope and microscopic operator, we inserted it into a specific area within the cell to detect OH in living cells. The results show that:the contents of OH in the cytoplasm and nucleus are small under normal culture, higher in cytoplasm than in nucleus; when cultured in the medium containing LPS, the contents of OH in the cytoplasm and nucleus increased, more in cytoplasm; when added OH scavenger, DMSO, before added LPS, OH would be destroyed and the content of OH reduced.