In Phase I we strive to achieve an overarching understanding of defects so that we can inform and incorporate new syntheses with improved chemical function as we expand into Phase II. Such understanding is only possible through the development of new imaging techniques and, more importantly, the integration with data science to cover the problem’s complexity starting from the atomic-scale, directly addressing one of NSF’s 10 big ideas: Harnessing the Data Revolution. The transformative impact of our Center therefore goes beyond the question of defects in any one chemical system: new instrumentation and data analysis tools will have a lasting influence on related chemistry fields as we seek to change our outlook on chemistry as a field of pure compounds to one where imperfections are welcomed.

Our NSF CAFF Phase I Projects share center Goals, complement our Education and Outreach Plan, and present Phase II opportunities: Phase I Projects are (1) Defect-dependent exciton interconversion at organic-organic interfaces; (2) Heterogeneity-driven chemical dynamics in metal-metal nanoparticles; and (3) Defect-supported energy-transfer in inorganic-organic hybrids. We will leverage our team’s combined expertise in predicting, visualizing, and time-resolving localized structure and dynamics, using methods such as electron, tunneling, and hyperspectral microscopy as well as ultrafast laser spectroscopy. 

Phase I Goals are integrated within our Education and Outreach: (A) Atomic and nanoscale visualization and understanding of defects inherent to chemistry; (B) Correlating local chemistry to ensemble chemical behavior; (C) Co-development of novel data science approaches and modular instruments to move towards seamless real-time, data loss-less analysis of large data sets. 

Defect-dependent exciton interconversion at organic-organic interfaces

Two important processes at organic-organic interfaces in which defects dramatically impact chemistry are energy transfer between surface functional groups of carbon dots and singlet/triplet exciton interconversion at grain boundaries of organic solids. These systems possess a diversity in chemical structures of which only a small subset, dependent on preparation method and surface treatment, may play an outsize role in determining the overall dynamic behavior. The expected outcomes of NSF CAFF are transformative knowledge about how to exploit defects through imaging at atomic, nano- and microscales; spectroscopic insight across multiple time domains; and partnership with theory. Innovations include new data-driven algorithms and modular instrumentation that are crucial for broadening access and advancing physical chemistry.

Heterogeneity-driven chemical dynamics in metal-metal nanoparticles

Photocatalysis and oxidative degradation in bimetallic nanoparticles are two important processes in which intra- and inter-particle heterogeneity influence chemistry. Do we need ‘pure’ samples in order to obtain optimized chemical performance? Or do we require detailed knowledge, free from ensemble averaging, of how to exploit atomic-scale flaws in metal nanoparticle hybrids? NSF CAFF will answer these questions with in operando, atomic-scale spatial resolution to localize defects and their evolution as reactions progress, while nanometer spatially-resolved spectroscopy tracks energy flow. Additional transformative outcomes include new modules and data science methods to follow and control reactions in situ.

Defect-supported energy-transfer in inorganic-organic hybrids

Phase I of NSF CAFF will focus on two systems in which inorganic-organic interfaces, and the presence of defects, have profound effects on energy transfer from the light harvesting inorganic core to the organic surrounding. First, plasmonic nanoparticle cores with electropolymerized polymer shells exhibit a broad range of energy transfer efficiencies that we hypothesize are due to defects. The other system exploits activation of SF/TF in organic molecules through energy transfer from inorganic nanostructures, but depend on the quality of the interface. Combined Center-level expertise is required to relate energy transfer to structural parameters and in particular defects on the atomic, nano- and microscales in order to exploit imperfections for optimized energy transfer.