Mesoporous Silica Thin Films
Sam Houston State University
My goal for this summer was to synthesize and deposit mesoporous silica as a thin film onto glass cover slips that had been previously coated with polystyrene spheres and a thin film of gold. In order to get to that point of proficiency, I had to begin depositing onto glass cover slips without the gold and spheres. Throughout the summer, I used a procedure for synthesizing SBA-15, which is a mesoporous material with pores of a specific size range and shape, as well as micropores that connect the mesopores. Mesopore is a term used for holes that are 2-50 nanometers in diameter, and micropores are any holes with a diameter less than that. To synthesize mesoporous materials, a general process is followed: amphipathic molecules, molecules having a hydrophilic head and a hydrophobic tail, are put into a solution at a high enough concentration that they come together forming micelles, where all the hydrophobic tails are next to each other surrounded by the hydrophilic heads in a sphere or other 3D shape. Then, the micelles will self-assemble into an ordered, packed arrangement. Next, a silica precursor is added which will maneuver throughout the solution in between the micelles. Finally, an acid is added to begin the chemical reaction that will first hydrolyze then condense the silica precursor, forming silica. The last step is template removal, the removal of the micelles, leaving the silica with empty pores. For most of the summer I removed the template by calcination, or burning off the micelles, using a furnace that Dr. Loeffler kindly loaned to Dr. Thompsonís lab for the duration of this project. My final experiment of this summer was synthesizing and depositing the thin film onto the gold-coated cover slips that Asish Parbatani and Antonio Carillo had previously prepared. Later, Asish will experiment to collect the Raman spectra from these film-covered slips as he has been doing with gold-coated slips lacking the thin film of mesoporous silica. The purpose of the silica is to act as a filter, allowing only the select compounds through, like ATCA, from which Asish has been working to collect Raman data, so that we may submerge the complete sensor in a liquid, like blood containing ATCA as well as all the other various substances found in blood, or allowing cyanide to enter the filter as a gas with other substances in the gas phase around it.