The Synthesis And Bio/Chemosensing Studies Of Novel Metal-Graphitic Nanocapsules

Biosensing is an interdisciplinary field originated from numerous subjects, such as biology, mathematics, medical science, physics, chemistry, co mputer science and material science. Recent years, the sensitivity and specificity of the biosensor have been significantly improved along with the development of biological technology. However, as the issues of environmental pollution and various diseases becoming serious, multifunctional biosensor systems integrating of diagnosis, imaging and treatment, are in more urgent need. Researchers tend to utilize biocompatibile nanomaterials to obtain multifunctional nanosensors. Particularly worth mentioning is the graphitic and metal nanomaterials, possessing excellent properties in electricity, optics, thermology, mechanics and so on. Although many kinds of metal-graphitic materials have been prepared and applied to various fields, several problems remain to be solved, such as size, quality, stability, homogeneity and synthesis simplification, etc.Considering the issues above, we propose simple chemical vapor deposition(CVD) method to fabracate several kinds of metal-graphitic nanomaterials, and investigate the applications in biological detection, anti-counterfeiting, bioimaging, cancer theranostic The major contents are listed as follows:In chapter 2, Based on its magnetic enrichment and difference in affinity with ss DNA and ds DNA, we demonstrated the utiliz ation of magnetic graphitic nanocapsule(MGN) for programmed DNA. MGN was composed of magnetic Co core and graphite shell, displaying the unique properties of graphite and magnetic particles. The MGN could quench around 98% of the fluorescence of FAM-DNA1 within minutes through energy-transfer or electron-transfer processes, followed by the formation of DNA1-MGN. Upon the addition of targeted DNA T1, it could be fished and enriched from the original sample solution with MGN-DNA1. It is only in the presence of releasing DNA P1 that the sensing platform operates, with FAM-DNA1, T1 and P1 hybridizing to form a duplex helix. The helix has weaker interaction with the MGN which results in separating the FAM molecules from the MGN and, thus, recovering fluorescence. With this simple, nonenzymatic MGN sensing strategy, target DNA molecules down to 50 p M can be detected.In chapter 3, based on magnetic-graphitic-nanocapsule(MGN) template diacetylene assembly and photopolymerization, we report a multifunctional, self-assembled system for sensing and multicoded anti-counterfeiting. The as-prepared assembly system maintains the unique color and fluorescence change properties of the polydiacetylene(PDA) polymers, while also pursues the superior Raman, NIR, magnetic and superconducting properties from the MGN template. Based on both fluorescence and magnetic resonance imaging(MRI) T 2 relaxivity, the MGN@PDA system could efficiently monitor the p H variations which could be used as a p H sensor. The MGN@PDA system further d emonstrates potential as unique ink for anti-counterfeiting applications. Reversible color change, strong and unique Raman scattering and fluorescence emission, sensitive NIR thermal response, and distinctive magnetic properties afford this assembly system with multicoded anti-counterfeiting capabilitiesIn chapter 4, based on the superior chemical stability and impermeability of graphite, making a protecting shell, we report the facile synthesis of superstable Ag Cu@graphite(ACG) nanoparticles(NPs). Altho ugh silver has a larger optical cross section and lower cost than gold, it has attracted much less attention because of its easy corrosion, thereby degrading plasmonic signals and limiting its applications. To circumvent this problem, the growth of several layers of graphene onto the surface of Ag Cu alloy NPs effectively protects the Ag surface from contamination, even in the presence of hydrogen peroxide, hydrogen sulfide, and nitric acid. In addation, ACG showed strong SERS affect, displaying good sensiti vity, repeatability and stability in SERS detection.In chapter 5, based on the strong Raman signals from the graphitic shell and the SERS effect from Ag Cu, along with alkyne having Raman signals in silent region of the cell, we fabricate alkyne-functionalized superstable graphitic silver nanoparticles for Raman imaging. The ACG NPs have been utilized to enhance the unique Raman signals from the graphitic shell, making ACG an ideal candidate for cell labeling, rapid Raman imaging, and SERS detection. ACG is further functionalized with alkyne-polyethylene glycol, which has strong Raman vibrations in the Raman-silent region of the cell, leading to more accurate colocalization inside cells.In chapter 6, we develop a simple chemical-vapor-deposition method to fabricate graphite-isolated-Au-nanocrystal(GIAN) nanostructures for multimodal cell imaging and photothermal-enhanced chemotherapy. First, a surface enhanced Raman scattering substrates, GIANs quench background fluorescence and reduce photocarbonization or photobleaching of analytes. Second, GIANs can be used for multimodal cell imaging by both Raman scattering and near-infrared(NIR) two-photon luminescence. Third, GIANs provide a platform for loading anticancer drugs such as doxorubicin(DOX) for therapy. Finally, their NIR absorption properties give GIANs photothermal therapeutic capability in combination with chemotherapy. Controlled release of DOX molecules from GIANs is achieved through NIR heating, significantly reducing the possibility of side effects in chemotherapy. The GIANs have high surface areas and stable thin shells, as well as unique optical and photothermal properties, making them promising nanostructures for biomedical applications.