CAREER: Understanding Nanoparticle Adhesion to Guide the Surface Engineering of Supporting Structures

University Of Pittsburgh, Pittsburgh PA

Investigators

Abstract

This Faculty Early Career Development (CAREER) Program grant supports fundamental research on metal nanoparticles, a class of materials that can be as small as 10 atoms in diameter and are widely used in advanced technologies such as catalysis. A critical challenge in the use of these nanoparticles is their loss of functionality via particle coarsening; a phenomenon in which the average particle size increases over time, thus degrading their performance. This grant seeks to mitigate such coarsening allowing for improved performance, thus advance knowledge to sustain global leadership in these critical materials technologies and aid in the development of national prosperity. Coarsening is countered through the use of stabilizing support materials, but at present these materials are mostly found through time-consuming and costly trial-and-error testing. The present research seeks to enable the rational design of new and better stabilizing support materials by elucidating the dependence of particle coarsening on the supporting surface structure. The grant develops new approaches to measure the attachment and stability of nanoparticles on well-defined surfaces under various conditions, enabling the rational engineering of surfaces to optimize the performance and lifetime of the nanoparticles. Ultimately, more stable nanoparticles will lead to significant advances in human and environmental health, clean energy, and more efficient manufacturing. Educational activities include collaborates with the University of Pittsburgh's School of Education and a local elementary school to create and nationally disseminate surface engineering focused curricular units for 6th-to-8th-grade students and professional development training modules for teachers. Nanoparticle coarsening occurs by two mechanisms, atomic diffusion (Ostwald ripening) and particle migration and coalescence; both are hypothesized to depend exponentially on the strength of adhesion between the nanoparticle and its substrate. The research will investigate this link using in situ adhesion tests in a transmission electron microscope, thus enabling direct measurements of adhesion energy with simultaneous sub-nm-scale materials characterization for individual nanoparticles. The research objective is to establish structure-function relationships that link surface chemistry, crystallinity, and morphology to nanoparticle adhesion and the rate of particle coarsening. The central hypothesis is that the substrate surface can be rationally modified to tune adhesion, and thus control the rate of particle coarsening. The knowledge developed will improve performance in applications of metal nanoparticles on oxide supports, specifically: plasmonic sensors for detection of pollutants and as biosensors for disease; nanophotonics for improved conversion of solar energy; and heterogeneous catalysis, which contributes to the production chain of one-third of the US gross national product. 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.