My work focuses on the synthesis of microporous aluminosilicates (zeolites) and their application to a variety of problems related to chemical sensing and gas separation. Depending on the application, existing synthetic approaches must be tailored to yield zeolites with the desired properties. In some cases it is necessary to develop completely new synthetic methods to meet the demands of a specific problem. Some novel synthetic methods developed in our lab address long standing barriers in zeolite synthesis: kinetics, crystal size, etc. Three motivating examples are discussed below.
CO2 Selective Zeolites for Flue Gas Separation
Zeolite matierals are a popular commercial adsorbent that have been considered for separation membranes for decades. Nevertheless, long synthesis times (on the order of days) and the high cost of suitable membrane supports still limit their wide spread application. To address this problem I am currently developing new synthetic routes that minimize the induction time required for FAU type zeolites. Preliminary data suggest High quality FAU type zeolites can be obtained in under 1hr, thus, moving crystallization times within range of continuous processing methods used for commercial production of membranes (polymers for example).
Zeolites as Impedance Based Chemical Sensors
Zeolite has been used as an impedance based electrochemical sensor for nerve gas model compounds. Recently, we discovered crystal size plays an important role in the ac ionic conductivity of zeolites. As a result, my efforts to create more conductive zeolites consist of synthesizing smaller and less polydisperse zeolites.
Zeolite as a SERS Substrate
Surface enhanced Raman scattering (SERS) is becoming a widely used mechanism for chemical sensing and commonly uses colloidal gold or silver nanopaticles as a key component. Controlling the size and degree of aggregation of such noble metal clusters is critical to their sensing performance. My efforts in the lab exploit both the ion exchangeability and the open, porous nature of the faujasite crystal structure to control silver cluster formation within the zeolite framework. Formation of silver clusters within the zeolite framework ensures nano-particles with a closely spaced, well defined three dimensional orientation relative to one another; a factor found to be key to large Raman signal enhancements.