Probing Facet Dependent Properties of Crystalline Nanomaterials and Interactions with Biomolecules using Hybrid AFM

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Metallic semiconductor nanomaterials or nanoparticles, such as cerium dioxide, zinc oxide and titanium dioxide, are produced in high volume and have broad applications in commercial products and processes such as sunscreens, antimicrobial agents, solar energy conversion and catalysis. These nanomaterials exhibit remarkable properties important to their industrial applications. However, the same unique properties may also cause unexpected biological consequences (e.g., cellular injury and cell membrane disruption), which are commonly attributed to the intrinsic and/or extrinsic properties. Intrinsic properties include size, shape, surface area, chemical composition, crystallinity, electronic, and surface reactivity. Extrinsic properties include radical formation and dissolution, which depend on intrinsic properties and environmental factors. Understanding of the roles of nanomaterial properties in toxicity mechanisms is critical for establishing regulatory and manufacturing frameworks for safe and sustainable nanotechnology. This project will encompass a suite of innovative scanning probe approaches to unravel facet-level material properties and true "nano" effects. Ultimately, the research findings may not only promote the "safety-by-design" of nanotechnology, but also facilitate the tailored fabrication of functional nanomaterials in a wide array of applications such as catalysis, biomedicine, phototherapy, and drug delivery, where crystal facet engineering for nanomaterials plays a pivotal role. Other broader impacts include (1) developing new teaching modules, laboratory manuals, and interactive learning activities targeted at a diverse student population to increase the STEM workforce. (2) organizing nanotechnology themed workshop series and hands-on training on scanning probe microscopy. This effort will be made through academic-industrial collaborations to build a focal point for regional research and education consortium in sustainable nanotechnology. Remote participants will be effectively involved through live streaming the workshops and other interactive webinars; At a molecular level, any changes in the size or shape of nanomaterials could be associated with changes in their exposed crystallographic facets or lattice planes. Different orientations and distributions of crystal facets have been reported to vary surface charge, surface tension or hydrophobicity, photocatalytic activity and surface reactivity, which ultimately changes biological effects of nanomaterials. The central hypothesis of this research is that the commonly characterized nanomaterial properties (e.g., size, shape, and zeta potential) and their environmental or biological impacts may originate from differences in exposed crystallographic planes or facets and their associated surface structures, atomic configurations and characteristics. To validate this hypothesis, this project seeks to achieve the following specific objectives: (1) Investigate the dependence of crystal facet distribution on highly crystalline semiconductor nanomaterials with distinct morphologies (cube, octahedra and plate). (2) Quantify facet-level intrinsic properties such as photo reactivity, band structures, and hydrophobicity to better reveal facet-dependent or facet-controlled surface properties. (3) Demonstrate hybridized scanning probe techniques such as using an atomic force microscope combined with Raman and infrared spectrometry in localized surface physical and chemical mapping of nanomaterials. (4) Investigate mechanisms of biomolecular interactions (adsorption, binding and degradation) at exposed facets of nanomaterials to provide new insight into potential biological implications. Furthermore, these research outcomes will be incorporated into STEM education and workforce development.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.