The Fabrication And Assembly Of Multi-asymmetric Particles

In recent years, fabrication and application of asymmetric particles have attracted more and more attention. Due to its unique structure, asymmetric particles have been widely used in many application fields, such as assembly of suprastructure, catalysis, drug delivery, and biochemical sensors. Currently, there are several typical methods of fabricating asymmetric particles:microfluidic technique and electrohydrodynamic jetting process, toposelective surface modification, modification at biphasic interface, and template-directed self-assembly. Through these approaches, asymmetric particles played a key role in promoting the practical application. In this issue, we use masking/unmasking method, and plasma etching to prepare asymmetric particles, which show excellent controllability and stability.In the second chapter, we have successfully fabricated the binary heterogeneous asymmetric particles with controllable patchiness combining masking/unmasking technique and plasma etching method. Hydrophobic silica (SiO2) particles were prepared in two ways, and these particles can meet the need of experiment. Then, An orderly array of single-layer silica particles was prepared using gas/liquid interface method with thermodynamic equilibrium of interfacial tension among water, particles and air. By oxygen plasma etching with different duration to control the thickness of polymer mask, particles were precisely controlled for functional modification. Importantly, plasma etching process does not have effect on the nature of SiO2 particles themselves. Asymmetric structure that has been shown through fluorescent microscope images of single particle, resembles different phases of moon and the particles are stable. Similarly, Au was deposited on SiO2 particles surface in a certain thickness to fabricate asymmetric particles with different sizes of gold.In the third chapter, we have successfully fabricated the ternary asymmetric particles with controllable patchiness combining masking/unmasking, double oxygen plasma etching and double functional modification. The methods of mentioned in chapter 2 were used to prepare hydrophobic SiO2 particles, and an orderly array of single-layer silica particles. By oxygen plasma etching with different duration to control the thickness of polymer mask, particles were precisely controlled for functional modification. Using metal and fluorescent quantum dots, ternary asymmetric particles with two-faced gold, Au/Ni and two-faced fluorescence were fabricated, respectively. Energy Dispersive Spectrometer (EDS) mapping was used to distinguish between Au and Ni on particles, and Ni provided magnetic response for these particles which can be oriented in magnetic field. In fluorescent microscope, all asymmetric area can be clearly distinguished and particles achieved self-assembly in a certain degree. Complex operations and expensive reagents have been not used in the whole process. The asymmetric particles have good stability and show the potential to build complex structures.