James M. Tour - US grants

With this award from the Chemistry Research Instrumentation and Facilities (CRIF) Program, the Department of Chemistry at William Marsh Rice University will acquire a console for a 400 MHz NMR Spectrometer. This equipment will enable researchers to carry out studies on a) metallocene-alumoxane interactions; b) solution structural characterization of tri-metallic molecules; c) characterization of the product distribution and relative yield from the facile hydrogen/deuterium exchange in organic and organometallic aromatic compounds catalyzed by Group 13-mercury complexes; d) synthesis of molecules of precise length and constitution for electronic, photonic, and template self-replication applications; e) development of novel organic synthetic methods and the total synthesis of natural products; f) metal atom chemistry; g) chemistry of novel aromatic systems; h) terpene biosynthesis using recombinant microorganisms; and g) the synthesis of single-stranded DNA oligomers containing nonnatural nucleotides.

Nuclear Magnetic Resonance (NMR) spectroscopy is the most powerful tool available to chemists for the elucidation of the structure of molecules. It is used to identify unknown substances, to characterize specific arrangements of atoms within molecules, and to study the dynamics of interactions between molecules in solution. Access to state-of-the-art NMR spectrometry is essential to chemists who are carrying out frontier research. The results from these NMR studies will have an impact in a number of areas including materials chemistry and biochemistry.

The focus of this Focused Research Group proposal will develop the molecular science of fullerene nanotubes. These new materials have been hailed for their materials properties and the applications that these properties promise. The single greatest impediment to realizing this promise is the current poverty of chemical approaches for manipulating the tubes as individual molecules. Single-walled nanotubes (swnts) are truly molecular entities, owing to their high degree of structural perfection, but the molecular science of manipulating them in the sense that chemists manipulate other molecules is still quite embryonic. These manipulations include solubilization, covalent derivatization of tube ends and sides, sorting by length, electrical type, and diameter, assembly, cutting, and synthesis of tubes of specific helicity. These are the tasks that comprise the basis of nanotube manipulation, and are central technologies in the realization of the promise of swnt. One particular aim will be to develop a variety of strategies to solubilizing nanotubes in various solvents, including water, by supramolecular routes. Associations of swnts with other molecules will be designed - e.g., polymers or large macrocyclic compounds - both for solubilizing the tubes and for assembling them without making any covalent attachment to their sides, thus preserving fully their intrinsic materials properties. Sorting tubes by length, type, and diameter will be crucial to fulfilling hopes of using nanotubes as wires in molecular electronics. Crude separations by length and diameter have begun, but cleaner, scalable chromatographic and electrophoretic methods are needed. Sorting by electrical type will be approached by exploiting their different electrical and magnetic properties(e.g., using electrophoresis, electrochemistry, and electric or magnetic field gradients), as well as their structural differences to derivatize selectively by type.

A grand challenge is to synthesize tubes of a given electrical type. The plan is to utilize seed crystals of a particular type, (separated by methods developed as part of the proposed work), and use covalent chemistry at the end to assemble a catalyst for growth there. This challenge will make demands on several of the other goals, providing both a rich driving force, and, if successful, a remarkable new materials science with far-reaching technological impact.
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This Focused Research Group project will have a major impact in a fast-breaking area focused on the development of the molecular science of fullerene nanotubes. The research is highly synergistic, multidisciplinary, high-risk and high-impact, with a significant probability for technological payoff in areas that include molecular electronics and high performance composites. This team of intrnationally renown experts is being jointly supported by The Office of Mulitdisciplinary Affairs, The Division of Materials Research and The Chemistry Division of The Mathematical and Physical Sciences Directorate, and by the Division of Chemical and Transport Systems of The Engineering Directorate.

ABSTRACT


Proposal Number: CTS-0236281
Principal Investigator: Tour, James M. and McHale, Mary
Affiliation: Rice U
Title: SGER NanoKids Education Outreach Project-Proof of Concept


Ten different configurations of molecules resembling human stick figures have been synthesized in the PI's laboratory. The molecules as a group are dubbed the NanoKids. By portraying these molecules in a series of computer-animated lessons, the PI intends to develop a proof-of-concept support curriculum for introducing students in the 6-12 grade to the molecular environment. The longer vision is to develop extensive lessons based on the National Science and Technology Education standards. This SGER proposal is to obtain the funds for the proof-of-concept and to prepare for the upcoming submission of the full proposal.

This grant supports the acquisition of a scanning electron spectroscopy for chemical analysis (ESCA) instrument for interface characterization of bio- , geo- and nanomaterials at Rice University. ESCA, also known as x-ray photoemission spectroscopy (XPS), is a powerful and versatile method for evaluating the surfaces of complex materials. The characterization of material interfaces is an important activity in much of materials research; for bio-, geo- and nanomaterials it is essential for developing new materials and understanding their properties. It is intrinsically a surface technique sensitive only to the top several angstroms of a sample, but with the appropriate conditions can be used to probe depths up to 20 nanometers. Several projects require depth profiling of atomic concentrations at surfaces while others need information about the nature of chemical bonding at interfaces. Still others are interested in chemical mapping of interfaces at the tens of micron level. Nearly all participants must be able to measure the atomic composition of surfaces, and the ability to analyze multiple samples quickly and consistently is of particular value. ESCA can measure the relative amounts of carbon and nitrogen at a surface and can determine whether the carbon is graphitic or bound to nitrogen. ESCA works by bombarding surfaces with a controlled X-ray source and resolving the kinetic energy of the photoemitted electrons; these energies are then used to identify surface atoms and their chemical state. Both the relative amounts of atomic species at surfaces, as well as their chemical environment can be deduced from XPS data. Though samples are evaluated under vacuum conditions, the technique is flexible- conductive and non-conductive powders and thin films have been analyzed with this method. The specific system has a focused, intense x-ray source, leading to small spot sizes (10 microns and high x-ray flux. This feature speeds data collection and its large sample platforms allow for rapid analysis of multiple samples. The scanning capability also enables a wider range of surface chemical experiments, such as depth profiles of atomic composition near surfaces and chemical mapping at the tens of micron length scale.

The acquisition of a scanning ESCA will be especially significant to student training and development, specialized courses for undergraduates and graduates, and workshops. Over thirty graduate students, and tens of post-docs and undergraduates will be able to use this system to understand how surface chemistry plays a role in their research. The existence of a scanning ESCA will allow us to implement a set of programs that not only teaches students how to use the instrument, but also highlights the importance of interface chemistry in areas such as bio- and nanoengineering.

James Tour
The objective of this research is to develop external electronic and optical methods for controllably imaging, sensing, propelling and actuating nanocars and nanotrucks and to devise theoretical models for predicting the motion and output from these diminutive structures. The approach is to synthesize new nanocar entities that are suitable for rolling motion and susceptible to electronic manipulation, imaging using a host of microscopies and devising theoretical models for predicting the mechanisms, range of motion and work output extractable from truly nano-sized single-molecule machines.
Intellectual merit:Transport of goods and materials between points is at the heart of all engineering and construction in real-world systems. As researchers delve into the arena of the nano-sized world, it beckons that they learn to manipulate and transport nanometer-scale materials in a similar manner. This proposed work outlines a method to control the motion of nanocars at the nanoscale level, and thereby pave the way for future bottom-up nanoscale construction.
Broader Impact: The research plan outlined above will be leveraged with education and outreach efforts using the NanoKids program, thereby multiplying this program's impact on grades 6-12 students and teachers, undergraduate students, graduate students, and traditionally underrepresented groups in the sciences and engineering. This uses the attractiveness of nanoscale science to introduce fundamental concepts in chemistry, physics and biology including how those concepts eventually make their way into the marketplace thus impacting everyday life. Funding this work will provide a path to future construction while laying groundwork for education from middle school to post graduate studies.

In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, James Tour, Stephan Link and Angel Marti of the William Marsh Rice University will develop and study molecules that exhibit controlled motion on a surface, "nanocars". The approach is to synthesize "nanocars" that incorporate fluorescent moieties within their frameworks and to continue expanding the repertoire of molecular parts that can be used to build these molecules. The PIs will also incorporate molecular entities into the "nanocars" that exhibit photon driven rotation and may acts as a propulsion mechanism for the molecules. Finally, the PIs will develop optical microscopy methods for tracking and characterizing the translation motion of the individual molecules and to utilize these methods to measure quantities such as collision frequencies and diffusion coefficients. The broader impacts involve training undergraduate students, graduate students and postdoctoral researchers. Additionally, the PIs plan to develop informal science learning approaches aimed at middle school students. Major principles in book chapters from middle school science curricula will be translated into bullet points, developed into dance songs (with professional help) and then added to open source Step Mania and Jamming software packages.

This work will enhance our fundamental understanding about controlling individual molecular movement across a surface. Ultimately, such work could lead to the development of molecular machines that could control chemical transport and fabrication at ultrasmall dimensions.

Abstract: In the prior funding cycle, we successfully obtained a mechanistic understanding of the chemical basis for the excellent therapeutic actions in mild traumatic brain injury (TBI) of our carbon nanoparticle (CNP) platform, poly(ethylene)glycol-hydrophilic carbon clusters (PEG-HCCs). We identified new actions that point to profound new directions for our CNPs. We: 1) discovered that the HCC's broad redox potential extended their action as a redox mediator among mitochondrial constituents involved in electron transport, i.e. a nanoparticle enzyme, or ?nanozyme?, and 2) identified a new mechanism by which hemorrhage causes cellular toxicity: rapid and persistent generation of DNA double strand breaks and robust DNA damage response leading to cellular ?senescence?, in which cells become a nidus for inflammation. While senescence could be prevented by PEG- HCCs, the cells became sensitized to iron toxicity/ferroptosis. This interaction led us to generate a new CNP, covalently bonding iron chelator, deferoxamine (DEF). Our results indicate DEF-HCC-PEG effectively addressed hemin and iron-related injury, senescence and ferroptosis. Given that mitochondrial dysfunction and hemorrhagic contusion (HC) are associated with poor outcome in TBI, these findings directly indicate the benefit of pursuing these mechanisms. The identification of key mechanistic features of our CNP platform that facilitate a mitochondrial site of action and new mechanism of hemorrhage-induced pathology form the basis for this renewal application. We will incorporate our understanding of the PEG-HCC mechanisms of action to generate a more immediately translatable CNP utilizing a good manufacturing practice (GMP) starting material, activated charcoal, and test them in-vivo in a rodent TBI with hemorrhagic contusion (TBI/HC). Our overall hypothesis is that the mechanisms of action discovered in our prior application will be translatable to GMP starting materials and will act on both the genomic and mitochondrial damage associated with TBI/HC. Specific Aim 1 will test the hypothesis that an oxidizing synthesis environment can be optimized to generate GMP-derived starting materials, PEG-oxidized activated charcoal achieving, the desired characteristics of a CNP nanozyme. Specific Aim 2 will test the hypothesis that DEF-linked CNP will address hemorrhage-related mitochondrial and genomic events triggering senescence and resistance to ferroptosis. Specific Aim 3 will administer the CNPs developed in Aims 1 and 2 to moderate-severe TBI/HC model. Completion of these Aims will yield a more readily translatable version of our CNP platform building on a growing understanding of the critical features and sites of action for their nanozyme mechanisms. New therapeutic targets emerging from a more thorough understanding of pathological mechanisms by which hemorrhage complicates outcome from TBI will guide the design. By employing GMP starting material, this project can generate breakthrough materials more rapidly translatable to the clinic. Because mitochondrial dysfunction and the cellular consequence of hemorrhage are features both of acute injury and of aging and cognitive decline, a broader potential for this therapy is suggested.