Nanostructured materials for biological imaging and chemical sensing

In the recent years, the design and synthesis of fluorescent nanoparticles for biological and chemical sensing applications have received considerable attention due to the excellent photostability and emission intensity of fluorescent nanoparticles and the intrinsic sensitivity of fluorescence based methods. Although considerable progress has been made in their synthesis, there is still need for low-cost and high throughput methods for their widespread utilization in biological and chemical sensing applications. In addition, studies regarding their biocompatibility are necessary to identify the toxicological potential of these nanomaterials. In this context, this thesis seeks new methods for multifunctional fluorescent nanoparticle synthesis and investigates their interactions with living organisms. In addition, it reports the applications of the fluorescent nanomaterials in biological imaging, therapy and chemical sensing applications. First, we report a self-assembly method to prepare PEGylated or peptide functionalized mesoporous silica nanoparticles (MSNs) for cell labeling and drug delivery applications. The good cyto- and blood- compatibility of the functionalized nanoparticles were demonstrated. Next, we demonstrated a surfactant assisted method to synthesize ultrabright silica nanoparticles and studied their in vitro v cytocompatibility with several cell lines. We demonstrated the applications of ultrabright particles in cell labeling, chemo and photodynamic therapy and trace explosive sensing. Then, we discuss a template-free method (porosity difference based selective dissolution strategy) to prepare self-luminescent mesoporous hollow silica nanoparticles with tailored shapes. In addition, we studied the surface effects on blood compatibility of nanoparticles in detail using the MSNs possessing different surface functional groups (ionic, polar, neutral, and hydrophobic). Finally, we investigated the optical properties of polydopamine nanoparticles and showed that fluorescence of asprepared polydopamine nanoparticles can be used for sensitive and selective detection of the dopamine neurotransmitter.