Application of surface functionalization for designing novel interfaces and materials

Liu, Yue
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University of Delaware
In recent years, surface and interface reactions have affected dramatically device fabrication and material design. Novel surface functionalization techniques with diverse chemical approaches make the desired physical, thermal, electrical, and mechanical properties attainable. Surface modification and functionalization can also be applied to a variety of different substrates and nanoparticles for their target properties by designing appropriate chemical reactions. Meanwhile, it also serves as one of the most important key steps for further assembly process in order to make novel devices and materials. In the following chapters, a novel chemical approaches to reaction and functionalization of inorganic substrates and nanoparticles including silicon, gold and magnetic materials will be generalized and discussed. Furthermore, the specific functionalities including amines, azides and alkynes in different materials can be applied to address further biofunctionalization and assembly processes. The majority of surface and interface reactions targeted by this thesis work are the reactions of primary amines and "click chemistry". The ultimate goals of the projects are: 1) making very sensitive biosensor devices to detect the biomolecular interactions : This project involves designing the surface reactions based on semiconductor substrate, attachment of biomolecules through surface reactions, and surface passivation of the remaining reactions sites with organic molecules; 2) designing novel magnetic composite materials : This project targets surface modification of magnetic nanoparticles with complementary functionalities and assembly of those different batches of nanoparticles through "click chemistry" reaction; 3) driving ultrafast and high coverage of surface coating process to make multilayer coating products by nanoparticles layer deposition method (NPLD), This project involves surface modification of nanoparticles, of the substrate, and the surface assembly process. A combination of spectroscopy and microscopy techniques was utilized to study the functionalization and assembly processes. Fourier-transform infrared spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), Time of fight Ion Mass Spectroscopy (ToF-SIMS) and Density functional Theory (DFT) calculations were applied to confirm the chemical approaches and the assembly process. Atomic Force Microscopy (AFM) and/or Scanning Electron Microscopy (SEM) were combined to obtain the morphological information and surface properties following each surface modification step. Other complementary techniques for these projects also include X-ray diffraction (XRD) and Vibrating Sample Magnetometry (VSM) to verify the physical properties of the assembled materials.