Professor Marc Knecht of the University of Miami and Professor Anatoly I. Frenkel of SUNY at Stony Brook are supported by the Macromolecular, Supramolecular and Nanochemistry (MSN) Program of the Division of Chemistry to develop biomolecule-bonded nanoparticles for unique applications in catalysis. Nanoparticles are incredibly small-sized materials that are 1000 times smaller than the width of one strand of human hair. To prevent these particles from uncontrollably aggregating to larger structures, small molecules are chemically bound to the particle surface. These molecules, also called ligands, keep the nanoparticles stably suspended in solution, allowing for studies of the material properties for wide ranging applications from harvesting solar energy to chemical catalysis. While these ligands are incredibly important, they are typically locked in a single conformation, thus limiting the properties of a nanoparticle. In this project, Professors Knecht and Frenkel are using biological inspiration and molecular design to develop biological ligands that can change their structure when irradiated with light of a certain wavelength or color. When these biomolecules are used to stabilize metal nanoparticles, they can change their arrangement when bound to the material, thus accessing two different conformations and enhancing the potential properties of a single material. These conformation differences and the changes to the material properties are being studied using catalysis and advanced spectroscopy methods, providing great detail to aid in material design. Professors Knecht and Frenkel are also engaging undergraduate students with the integration of this research with education at the entry level to encourage students into science related studies and careers. In addition, plans are implemented to realign the Freshman and Sophomore general and organic courses and laboratories to improve the chemistry undergraduate students' retention ratio.
Colloidal metal nanoparticles are typically constructed using surface passivating ligands that are rigidly bound to the inorganic surface, locking them into a single configuration. By having the ability to remotely actuate the interfacial structure on the particle surface to adopt different conformations, the properties of the materials could be tuned on demand. Professors Knecht and Frenkel hypothesize that peptide-based nanoparticle passivants can be remotely and reversibly reconfigured via external stimuli to adopt two different configurations for on demand material property control. Such capabilities are achievable through the integration of a photoswitch into the peptide structure. Changes in the photoswitch isomerization state can be propagated through the peptide conformation due to the binding between the biomolecule and the nanoparticle surface. This capability is being examined using catalysis as a surface probe of the ligand structural conformation, where differences in reaction rates are observable. These differences are being exploited to achieve on/off catalytic reactivity, which could be important for multistep reactions. Furthermore, as part of this study, advanced, in situ and operando X-ray spectroscopic analysis of the nanoparticles are being used to identify changes in particle surface structure as a function of ligand conformation before, during, and after photoswitching and catalysis. Finally, the effects of the nanoparticle composition, size, and shape are being studied to modulate the level of photoswitch-based peptide structural differences for enhanced control over the particle catalytic properties.
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.
