Alexei V. Tivanski
- M.S., Moscow Institute of Physics and Technology (2001)
- Ph.D., University of Pittsburgh (2005)
- Postdoctoral Research Associate, Lawrence Berkeley National Laboratory, (2005-2007)
Nanoscale studies of mechanical, optical and electrical properties of organic molecules, polymers and biomolecules (single molecules, molecular thin films and interfaces, nanostructures); chemical speciation and enviromental processing of individual submicron atmospheric aerosols and their impact on climate and enviroment; reactive spectromicroscopy of individual submicron aerosols.
Our research focuses on a single molecule level study of the mechanical, optical and conductive properties of molecular junctions composed a few molecules up to molecular films that will enable the design and fabrication of molecular devices with useful electrical, mechanical and optical properties. We are also interested in the chemical speciation and environmental processing of individual submicron atmospheric aerosols and their impact on the climate and environment.
Opto-Electromechanical Properties of Nanostructured Materials
Molecular devices offer not only an ultra-miniaturization of electric devices but can also exhibit novel and significantly improved physical, chemical, and optical properties and phenomena that are unique to this size scale and may not be as predictable as those observed at larger scales. Presently, molecular devices fail frequently and are difficult to control and replicate, in part due to the severe geometric constraints under which they are constructed and connected to external circuitry. The feasibility of these devices depends on our ability to understand and control specific properties of individual or bundles of molecules and to connect these nanostructures to the macroscopic world. The goal of this research program is quantitative physical chemistry studies to correlate conducting, optical, structural and mechanical properties of molecular nanojunctions with potential use in opto-electromechanical molecular devices. These include studies of molecule-electrode contact effects under the influence of applied force and elucidation of the charge transfer mechanisms of cooperative effects between interacting molecules forming nanojunctions, with the aim of developing mechanically stable, reliable and efficient electrical contacts and interconnects. Conductive probe atomic force microscopy and scanning force spectroscopy techniques are employed to repeatedly form metal-molecule(s)-metal junctions and study their properties. We are examining the properties of these junctions under different temperatures as a function of molecular length, molecule-electrode contact type, number of molecules forming the nanojunction, AFM probe material, mechanically induced stress and strain, and under different organic solvents and inert gases.
Chemical Speciation and Environmental Processing of Atmospheric Aerosols
Atmospheric aerosols have substantial effects on the atmospheric radiative budget either by directly scattering and absorbing solar radiation or indirectly by acting as cloud condensation nuclei and facilitating the formation of aqueous aerosol. These direct and indirect effects lead to a warming and cooling of the atmosphere, respectively. The overall climate effect of increasing atmospheric aerosol concentrations remains largely unknown, primarily due to large uncertainties in the chemical composition of aerosols as well as a limited understanding of the chemical transformations and atmospheric lifetimes of particles due to atmospheric processing. We are developing a novel approach for reactive spectromicroscopy studies of single aerosols based on a combination of scanning transmission x-ray microscopy and near edge x-ray absorption fine structure spectroscopy. This combination provides a unique opportunity to identify functional groups within various regions of individual submicron particles. One of the goals of our research is in situ chemical kinetics study of both the chemical and morphological changes of individual atmospheric particles during chemical transformations. Chemical transformations include oxidation of these particles with atmospheric trace gases (e.g. NO2, SO2, H2SO4, NHO3) followed by water uptake. These studies are important to understand the chemical composition and environmental processing of atmospheric aerosols and hence radiative forcing.
- Ditzler, L.R.; Sen, A.; Gannon, M; Kohen, A.; Tivanski, A.V. Self-assembled Enzymatic Monolayer Directly Bound to a Gold Surface: Activity and Molecular Recognition Force Spectroscopy Studies. Journal of American Chemical Society, 2011, 133, 13284-13287.
- Karunatilaka, C.; Bučar, D.K.; Ditzler, L.R.; Friščić, T.; MacGillivray, L.R.; Tivanski, A.V. Softening and Hardening of Macro- and Nano-Sized Organic Cocrystals in a Single-Crystal Transformation. Angewandte Chemie International Edition, 2011, 50, 8642-8646.
- Ghorai, S.; Laskin, A.; Tivanski, A. V. Spectroscopic Evidence of Keto−Enol Tautomerism in Deliquesced Malonic Acid Particles. Journal of Physical Chemistry A, 2011, 115, 4373-4380.
- Kapadia, P. P.; Ditzler, L.R.; Baltrusaitis, J.; Swenson, D.C.; Tivanski, A.V.; Pigge, C.F. Semiconducting Organic Assemblies Prepared from Tetraphenylethylene Tetracarboxylic Acid and Bis(pyridine)s via Charge-Assisted Hydrogen Bonding. Journal of American Chemical Society, 2011, 133, 8490-8493.
- Hamilton, T. D.; Bučar, D. K.; Baltrusaitis,J.; Flanagan, D. R.; Li, Y.; Ghorai, S.; Tivanski, A. V.; MacGillivray, L. R. Thixotropic Hydrogel Derived from a Product of an Organic Solid-State Synthesis: Properties and Densities of Metal-Organic Nanoparticles. Journal of American Chemical Society, 2011, 133, 3365-3371.
- Ghorai, S.; Tivanski, A. V. Hygroscopic Behavior of Individual Submicrometer Particles Studied by X-ray Spectromicroscopy. Analytical Chemistry, 2010, 82, 9289-9298.
- Ditzler, L.R.; Karunatilaka, C.; Donuru, V.R.; Liu, H; Tivanski, A.V. Electromechanical Properties of Self-Assembled Monolayers of Tetrathiafulvalene Derivatives Studied by Conducting Probe Atomic Force Microscopy. J. Phys. Chem. C, 2010, 114, 4429-4435.
- Galgano, J.J.; Karunatilaka, C.; Rethwisch, D.J.; Tivanski, A.V. Atomic Force Microscopy Study of Photoreversible Nanoscale Surface Relief Grating Patterns on Side Chain Dendritic Polyester Thin Films. Colloids and Surfaces. A, 2010, 360, 167-174.
- Tivanski, A. V.; Li, J. K.; Walker, G. C. Pressure-Induced Restructuring of a Monolayer Film Nanojunction Produces Threshold and Power Law Conduction. Langmuir, 2008, 24, 2288-2293.
- Tivanski, A.V.; Hopkins, R.J.; Gilles, M.K. Oxygenated Interface on Biomass Burn Tar Balls Determined by Single Particle Scanning Transmission X-ray Microscopy. Journal of Physical Chemistry A, 2007, 111, 5448-5458.