Frick Laboratory, 228
Our research aims to develop new surface and interface chemistry that can be integrated with novel architectures to create prototypical devices with outstanding behavior. We are particularly interested in interfaces between dissimilar materials such as are present in molecular electronic devices or that exist between synthetics and living tissue in biomedical implants.
Our approach is to focus on the basic chemistry that is key to interface design: Knowledge of nanoscopic structure and molecular bonding at the interface is essential. Indeed, understanding and controlling interfaces lies at the confluence of nanoscience and microelectronics or medicine.
We introduced self-assembled monolayers of phosphonates (SAMPs) as a class of structurally variable, well-organized, dense coatings for metal oxides, and we showed them to be superior to well-known thiols/Au or siloxanes/oxides for cases where air and/or moisture are present. SAMPs are now in wide use, especially for electrode surface modification. More recently, we have shifted our attention from oxides to other inorganics or organic polymer substrates. These broad classes of materials are important for emerging applications in electronics and bioscaffolds. SAMPs, however, do not bond directly to these materials, and so we had to develop interfaces to enable multi-component constructs.
Most approaches to surface activation of non-oxide substrates involve harsh reagents, such as oxygen plasma, for partial surface oxidation; in contrast, we use “soft,” surface organometallic chemistry as a non-destructive method for interface synthesis: Ligating functional groups of the substrate serve as coordination sites for vapor-deposited titanium or zirconium alkoxide, which can then be converted under mild conditions to a surface-bound metal oxide. This oxide may be useful for its inherent properties or it could serve as an adhesion layer to bond a SAMP to the substrate.
In the context of application to electronic materials, we recently discovered that very thin (2-10 monolayers) of TiO2 could be prepared on H‑terminated Si by a process involving vapor phase deposition of a volatile Ti alkoxide followed by gentle heating. We believe that this process is initiated by coordination of the alkoxide with any of the multitude of surface Si-H sites. This unusual type of TiO2 has a very large band gap compared with the common forms of TiO2, anatase or rutile, and it imparts interesting device properties to Si-based photovoltaic devices, quadrupling efficiency compared to untreated analogs. The chemistry between the Si-H units and the Ti alkoxide or the TiO2 product is under study as a means to further improve device behavior in collaboration with several groups in the Electrical Engineering Department. We have also found that our TiO2 can be grown on the surface of bismuth selenide telluride, a novel “topological insulator” (TI). Attaching our SAMPs to this oxide adhesion layer enables us to adjust the work function of the TI in a systematic way. In collaboration with Professor Cava’s group we are now studying how such surface treatments might lead to adjustment of the Fermi level of these materials, which is key to controlling their fascinating electronic properties.
We have also been able to manipulate the surface properties of organics such as polyamides, polyurethanes, and polyesters using a ZrO2 thin film. This enables us to bond cell-adherent materials to these materials in the context of creating new approaches to tissue scaffolds. Our work now focuses on creating novel conduits for nerve regeneration. A clinically approved method is to guide nerve growth through a hollow conduit that is usually made of a synthetic material. While these conduits show promise, insufficient levels of nerve regeneration result for two reasons: inadequate nutrient and waste exchange, and inadequate formation of the extracellular matrix (ECM) that is necessary to guide axon directed outgrowth. Working with Professor Schwarzbauer in the Department of Molecular Biology, our approach is to develop a “bridge,” an open architecture instead of a tube, that neurons can cross to span an injury site and that parallels the natural process for nerve repair.
A key step early in the repair process is ECM formation: ECM proteins are assembled in “cables” that, if long enough, can span an injury site. Schwann cells, which are neuron support cells, use these cables to rebuild nerve tissue, while neurons use the cables as a guide to extend axons and make connections with other nerve cells. We envision the architecture of our neuron bridge to include ECM cables in linear arrays on a compliant synthetic surface. Neurons will then attach to these cables at one end of the material and directed axon outgrowth will take place over the bridge. In this regard, we have developed a method to not only attach our ZrO2 adhesion layer to polymers, but also to pattern such attachment on these materials. In this way, we have shown it possible to spatially direct cell spreading and cell-assembled ECM formation on the polymer surface. We recently found that de-cellurization of this ECM gives a “natural” scaffold onto which neuron surrogate cells can be attached and caused to spread, also with spatial control.
Member, NSF Committee of Visitors, 2016
Excellence Cluster Evaluation Committee, Humboldt U., Berlin, 2016
Chair, Hong Kong Theme-Based Research Grants Council, 2012-2015
President’s Award for Distinguished Teaching, 2012
Excellence Cluster Panelist, Humboldt University, Berlin, 2011
Japan Society for the Promotion of Science Fellow, 1995-6
Welch Lecturer, 1988
Pettit Lecturer, University of Texas, 1987
Visiting Professor, University of Paris, 1984
Frontiers Lecturer, Case Western Reserve University, 1982
Alfred P. Sloan Fellow (1976 - 1979)
Awarded NSF Postdoctoral Fellowship (1970)
National Institutes of Health Postdoctoral Fellow (1970)
National Science Foundation Graduate Fellow (1966-1970)
Shu, A. L.; McClain, W. E.; Schwartz, J.; Kahn, A. "Interface dipole engineering at buried organic-organic semiconductor heterojunctions." Org. Electron. 2014, 15, 2360-2366.
Whittaker-Brooks, L.; McClain, W. E.; Schwartz, J.; Loo, Y.-L. "Donor-Acceptor Interfacial Interactions Dominate Device Performance in Hybrid P3HT-ZnO Nanowire-Array Solar Cells." Adv. Energy Mater. 2014, 1400585.
Singh, S.; Bandini, S. B.; Donnelly, P. E.; Schwartz, J.; Schwarzbauer, J. E., "A cell-assembled, spatially aligned extracellular matrix to promote directed tissue development." Journal of Materials Chemistry B 2014, 2 (11), 1449-1453.
Donnelly, P. E.; Jones, C. M.; Bandini, S. B.; Singh, S.; Schwartz, J.; Schwarzbauer, J. E., "A simple nanoscale interface directs alignment of a confluent cell layer on oxide and polymer surfaces." Journal of Materials Chemistry B 2013, 1 (29), 3553-3561.
McClain, W. E.; Florence, P. R.; Shu, A.; Kahn, A.; Schwartz, J., "Surface dipole engineering for conducting polymers." Organic Electronics 2013, 14 (1), 411-415.
Avasthi, S.; McClain, W. E.; Man, G.; Kahn, A.; Schwartz, J.; Sturm, J. C., "Hole-blocking titanium-oxide/silicon heterojunction and its application to photovoltaics." Applied Physics Letters 2013, 102 (20).
Liao, K.-C.; Anwar, H.; Hill, I. G.; Vertelov, G. K.; Schwartz, J., "Comparative Interface Metrics for Metal-Free Monolayer-Based Dye-Sensitized Solar Cells." Acs Applied Materials & Interfaces 2012, 4 (12), 6734-6745.
Cattani-Scholz, A.; Liao, K.-C.; Bora, A.; Pathak, A.; Hundschell, C.; Nickel, B.; Schwartz, J.; Abstreiter, G.; Tornow, M., "Molecular Architecture: Construction of Self-Assembled Organophosphonate Duplexes and Their Electrochemical Characterization." Langmuir 2012, 28 (20), 7889-7896.
Allon, A. A.; Ng, K. W.; Hammoud, S.; Russell, B. H.; Jones, C. M.; Rivera, J. J.; Schwartz, J.; Hook, M.; Maher, S. A., "Augmenting the articular cartilage-implant interface: Functionalizing with a collagen adhesion protein." Journal of Biomedical Materials Research Part A 2012, 100A (8), 2168-2175.
Avasthi, S.; Qi, Y.; Vertelov, G. K.; Schwartz, J.; Kahn, A.; Sturm, J. C., "Electronic structure and band alignment of 9,10-phenanthrenequinone passivated silicon surfaces." Surface Science 2011, 605 (13-14), 1308-1312.
Jones, C. M.; Donnelly, P. E.; Schwartz, J., "A Nanoscale Interface Improves Attachment of Cast Polymers to Glass." Acs Applied Materials & Interfaces 2010, 2 (8), 2185-2188.
Liao, K.-C.; Ismail, A. G.; Kreplak, L.; Schwartz, J.; Hill, I. G., "Designed Organophosphonate Self-Assembled Monolayers Enhance Device Performance of Pentacene-Based Organic Thin-Film Transistors." Advanced Materials 2010, 22 (28), 3081-3085.
Avasthi, S.; Qi, Y.; Vertelov, G. K.; Schwartz, J.; Kahn, A.; Sturm, J. C., "Silicon surface passivation by an organic overlayer of 9,10-phenanthrenequinone." Applied Physics Letters 2010, 96 (22).
Dennes, T. J.; Schwartz, J., "A Nanoscale Metal Alkoxide/Oxide Adhesion Layer Enables Spatially Controlled Metallization of Polymer Surfaces." Acs Applied Materials & Interfaces 2009, 1 (10), 2119-2122.
Cattani-Scholz, A.; Pedone, D.; Blobner, F.; Abstreiter, G.; Schwartz, J.; Tornow, M.; Andruzzi, L., "PNA-PEG Modified Silicon Platforms as Functional Blo-interfaces for Applications in DNA Microarrays and Biosensors." Biomacromolecules 2009, 10 (3), 489-496.
Traina, C. A.; Dennes, T. J.; Schwartz, J., "A Modular Monolayer Coating Enables Cell Targeting by Luminescent Yttria Nanoparticles." Bioconjugate Chemistry 2009, 20 (3), 437-439.
Tarver, J.; Yoo, J. E.; Dennes, T. J.; Schwartz, J.; Loo, Y.-L., "Polymer Acid Doped Polyaniline Is Electrochemically Stable Beyond pH 9." Chemistry of Materials 2009, 21 (2), 280-286.
Dennes, T. J.; Schwartz, J., "A Nanoscale Adhesion Layer to Promote Cell Attachment on PEEK." Journal of the American Chemical Society 2009, 131 (10), 3456-+.
Cattani-Scholz, A.; Pedone, D.; Dubey, M.; Neppl, S.; Nickel, B.; Feulner, P.; Schwartz, J.; Abstreiter, G.; Tornow, M., "Organophosphonate-based PNA-functionalization of silicon nanowires for label-free DNA detection." Acs Nano 2008, 2 (8), 1653-1660.
Dennes, T. J.; Schwartz, J., "Controlling cell adhesion on polyurethanes." Soft Matter 2008, 4 (1), 86-89.
Shannon, F. J.; Cottrell, J. N.; Deng, X.-H.; Crowder, K. N.; Doty, S. B.; Avaltroni, M. J.; Warren, R. F.; Wright, T. M.; Schwartz, J., "A novel surface treatment for porous metallic implants that improves the rate of bony ongrowth." Journal of Biomedical Materials Research Part A 2008, 86A (4), 857-864.
Vaynzof, Y.; Dennes, T. J.; Schwartz, J.; Kahn, A., "Enhancement of electron injection into a light-emitting polymer from an aluminum oxide cathode modified by a self-assembled monolayer." Applied Physics Letters 2008, 93 (10).
Heijink, A.; Schwartz, J.; Zobitz, M. E.; Crowder, K. N.; Lutz, G. E.; Sibonga, J. D., "Self-assembled monolayer films of phosphonates for bonding RGD to titanium." Clinical Orthopaedics and Related Research 2008, 466 (4), 977-984.
Traina, C. A.; Schwartz, J., "Surface modification of Y2O3 nanoparticles." Langmuir 2007, 23 (18), 9158-9161.
McDermott, J. E.; McDowell, M.; Hill, I. G.; Hwang, J.; Kahn, A.; Bernasek, S. L.; Schwartz, J., "Organophosphonate self-assembled monolayers for gate dielectric surface modification of pentacene-based organic thin-film transistors: A comparative study." Journal of Physical Chemistry A 2007, 111 (49), 12333-12338.