Characterization Of Ricinoleic Acid Coated Spinel Nanoparticles And Micro Fabrication Of Four Point Device For Nanowire Electronic Conductivity Measurement
Committee Members: Advisor: Linda Doerrer, MSE/CAS Chemistry; Xin Zhang, MSE/ME
Abstract: The following work covers two distinct topics:
I. Characterization of ricinoleic acid coated spinel nanoparticles. Magnetic nanoparticles are of great interest today due to their potential contributions to the development of new imaging technologies. Ferrites, in particular, stand out because of their significant magnetic susceptibilities and relative chemical stability as candidates for a number of applications in technological, biomedical and environmental research. In this chapter, the vibrating magnetic susceptibility studies of a series of ricinoleic acid coated non-magnetite spinels with the form MFe2O4 (M= Co, Ni, Mn, Zn) will be presented. Results indicate similarities between the magnetic saturation susceptibility (MS) values obtained for Ni and Mn samples (55.9 emu/g and 48.8 emu/g, respectively), and published values for oleic acid, and other surfactant, coated species (~50 emu/g and ~20-50 emu/g respectively). Co samples demonstrated a MS of 5.06 emu/g that can be attributed to small core size and/or presence of other species during measurements. Finally, the Zn sample demonstrated dispersion difficulties and low magnetic susceptibility and was subjected to a series of pH dependent studies resulting in a maximum MS of 17.7 emu/g at pH 10. Higher susceptibilities have been attained by optimization of facile air-stable hybrid co-precipitation hydrothermal syntheses demonstrating how magnetic susceptibilities can be affected by the reaction conditions and size of nanoparticles.
II. Micro fabrication of four point device for nanowire electronic conductivity measurement.
The development of one-dimensional (1D), electronically conducting nanowires has attracted interest due to their possible integration into submicroscale electronic devices. The Doerrer group is investigating the preparation of electrically conductive, 1D, one atom wide nanowires employing a bottom-up approach. This chapter describes the design and development of a substrate for four-point probe electronic conductivity measurements with sub-micrometer scale Au wires utilizing micro-fabrication techniques for the characterization of the aforementioned structures. Potentially, the design would allow the user to deposit a sample on the micrometer scale Au contacts without the need for submicron probes. Initial devices are not well-defined at the smallest submicron features (<1 μm), preliminary thin film four point probe measurements of TTF-TCNQ (tetrathiafulvalene tetracyanoquinodimethane) are encouraging.