CAREER: Colloidal Nanoparticle Interfaces Probed by Vibrational Sum-Frequency Scattering Spectroscopy

With support from the Chemical Structure and Dynamics (CSD) program in the Division of Chemistry, Professor Carl Brozek of the University of Oregon is using sophisticated spectroscopies to study the surface of colloidal porous nanoparticles. From catalysis to opto-electronic behavior, the surface of nanoparticles dictates important behavior. Probing the structure and dynamics of the solid-liquid colloidal interface is challenging, however, because analytical techniques typically lack surface specificity.

Beyond conventional nanoparticles, porous colloids present the additional complexity of behaving like polymers and other flexible materials. Professor Brozek and his students will use vibrational sum-frequency scattering spectroscopy (VSFSS) to study the surface of metal-organic framework (MOF) nanoparticles. Their discoveries could reveal fundamental insight into the impact of porosity on colloidal stability and into the composition of nanoparticle solid-liquid interfaces.

Brozek and his students will complement these efforts with a K-adult educational program that integrates public library-based activities, K-12 science modules, soft skills workshops for high school students, and cross-disciplinary collaborations at the college and graduate level.

VSFSS probes only species with a net ordering of transition dipole moments. Due to the random orientation or centrosymmetric nature of bulk solvent and many crystalline solids, this technique provides interface-specific vibrational spectra with additional information into the relative ordering of species and their spatial orientation. Despite the power of this technique, few studies have investigated the surface of bare nanoparticle colloids.

Brozek and his students will use VSFSS to interrogate the surface of colloidal nanoparticles. Leveraging expertise of the Brozek lab to prepare colloidal MOF nanocrystals, they will study the impact of nanoparticle porosity and composition on the structure and dynamics of interfacial chemistry. Specific aims include understanding the influence of nanoparticle identity on the structure and dynamics of electrical double layers, the chemical interactions responsible for colloidal stability, and the impact of dynamic structural flexibility on interfacial chemistry.

Tackling these goals will require advancing the application of surface-specific spectroscopy to inorganic nanoparticles and developing variable-temperature capabilities of VSFSS. Insight into the electrical double layer structure and dynamics at porous and nonporous interfaces will advance conventional models of colloidal surfaces.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.