Catalytic and Sorbent Materials Chemistry and Engineering Group

Dr. Larsen's group works on a variety of projects related to catalysis, adsorption, and nanostructured materials design. By means of micro- and nano-fabrication methods based on electrohydrodynamic forces, we are currently designing nanocapsules, nanotubes, and nanofibers of inorganic, hybrid (organic/inorganic), organic, and biological materials for a variety of applications. Specifically, these submicron structures can be utilized for preparing nanovesicles for controlled release applications, reinforced composites, sorbents and catalysts, and tissue scaffolds. Being highly interdisciplinary, some of the work is done in collaboration with faculty and professionals affiliated with several foreign and domestic academic institutions and industry.
Figure 1. The two immiscible liquids (red and blue in this figure) are injected through two concentric electrified needles which are placed a few centimeters away from a grounded electrode (the collector). A compound Taylor cone is developed from whose tip a coaxial nano jet is emitted. Upon solidification of the outer liquid a sheathed fiber, or a liquid-filled hollow fiber is formed

Figure 2. Hollow nanotubes, as-collected, from a compound electrospray of an aged sol formulation (outer fluid) and glycerin (inner liquid).(A) Cylindrical nanotubes, without traces of varicose deformations. (B) View of the sample after being cut perpendicularly to the axis of the fibers, to expose their hollow structure. Note the good degree of monodispersity in tube diameter. (C) High resolution SEM of one of the nanotubes. (D) Cotton puff-like hollow nanofiber deposits collected in few minutes of operation; the ruler is in cm.

Figure 3. A fibrous chitosan film with a very high degree of microfiber orientation. Shown on the right is the nanofiber interconnects that gives improved mechanical strength to the overall structure.

Figure 4. A macroporous carbon sorbent made by templating a resin with silica submicron fibers, followed by pyrolysis and removal of the fibers by HF washing. Macroporous sorbents with quasi-cylindrical pores are more difficult to synthesize than their less efficient counterparts based on spheroidal cavities. The latter present transport "bottlenecks" due to their narrow pore interconnects.


Figure 5. 3-7 µm silica/siloxane hybrid vesicles with 50-100 nm shells. The vesicles were solvent-extracted and mechanically broken to expose their core-shell structure.