Presentation description

The large surface area of porous silica makes it ideal for catalysis, chemical separations, biosensing, and adsorption applications. To expand and refine these applications, porous silica surfaces are often functionalized with molecules that provide selective interfacial interactions, where quantifying their surface coverage is crucial to understanding their performance. Creating uniform monolayers of functional molecules on porous silica generates molecules in close proximity, creating homogeneous surfaces and facilitating interactions between the immobilized molecules. (3-Aminopropyl)triethoxysilane (APTES) is frequently used for porous silica surface silanization because the reactive terminal amine can be used to attach a variety of other molecules to surfaces. Prior methods of APTES surface silanization involve vapor-phase and solution-phase deposition on flat surfaces, such as silicon wafers and glass coverslips. My research considers deposition of APTES onto interior surfaces within porous silica particles using both methods. The large internal surface area of porous silica allows the APTES deposited on the interior to be detected by Raman-scattering spectroscopy within individual particles, providing structural and quantitative information about functionalized particles and their particle-to-particle uniformity. Compared to vapor-phase deposition, solution-phase deposition of APTES generally exhibits higher surface coverage and concentration within a particle. Further modification of APTES monolayers has been achieved through attachment of a terminal alkyne group via an NHS ester reaction with the terminal amine of immobilized APTES, where Raman spectroscopy can be used to detect the product of this reaction. Future surface modification will include functionalization with redox active molecules to serve as electron shuttles through the interior surfaces of the particles.