Soft Condensed Matter and Biophysics Projects
Lattice models of protein condensation (Theory)
Email: schmit@phys.ksu.edu
Number of REU participants: 1
A new paradigm is emerging in biology with the discovery that the cell uses phase transitions to organize the cytoplasm, perform metabolic functions, and respond to outside stimuli. These dense liquid states (sometimes called "membraneless organelles") are usually formed from the coalescence of two (or more) molecules that each have multiple binding sites. Our group is investigating how the physical mechanism of assembly contributes to the biochemical properties of the condensates. In this project we will develop lattice simulations to investigate how microscopic binding interactions affect macroscopic morphological changes in the resulting droplets. In particular, we will look at the coalescence of rod-like molecules of varying length that condense by either pairwise direct interactions, or indirectly by flexible crosslinkers.
Suspensions as Solutions: Solubility of Nanoparticles (Experiment)
Email: sor@phys.ksu.edu
Number of REU participants: 1
We have discovered that nanoparticle suspensions can act like solutions with thermally reversible, temperature dependent solubility. We have published one study [1] for 5 nm gold nanoparticles to determine their solubility as a function of their ligand shell and the solvent. We have extended these studies to the temperature dependence and data obtained by previous REU students has led to another paper published [2]. We are now collaborating with a group in Germany who make 2 nm ZnS nanoparticles that interact strongly with water and might show a negative solubility temperature dependence. i.e., they are less soluble at higher temperatures perhaps due to hydrogen bonding. The REU student would be involved in measuring the solubility of these nanoparticles in aqueous mixtures and investigating the effects of hydrogen bonding. This is a good project for someone who has interests in both physics and physical chemistry.
References (Bold type indicates REU student):
1. "Solubility of Gold Nanoparticles as a Function of Ligand Shell and Alkane Solvent", B. C. Lohman, J. A. Powell, S. Cingarapu, C. B. Aakeroy, A. Chakrabarti, K. J. Klabunde, B. M. Law, and C. M. Sorensen, Phys. Chem. Chem. Phys., 14, 6502- 6506 (2012).
2. "Temperature Dependent Solubility of Gold Nanoparticle Suspension/Solutions", J. A. Powell, R. M. Schweiters, K. W. Bayliff, E. N. Herman, N. J. Hotvedt, J. R. Changstrom, A. Chakrabarti and C. M. Sorensen*, RSC Advances 6, 70638–70643 (2016) DOI: 10.1039/C6RA15822F.
Interfacial Reaction Rates—Re-visiting the Arrhenius Rate Law (Experiment)
Email: bret.flanders@phys.ksu.edu
Number of REU Participants: 1
Chemical reactions that occur at solid-liquid interfaces are fundamental to heterogeneous catalysis, bio-membrane-based chemistry, electrochemistry, and monolayer and thin film deposition. We are interested in amplifying the Arrhenius rates of such reactions. A quartz crystal microbalance (QCM) is a device that employs a quartz crystal as a solid, reactive interface. By monitoring the ~5 MHz resonance frequency (of the quartz), which changes as molecules deposit onto its surface during an interfacial chemical reactions, the quartz interface serves as a real-time mass balance with nano-gram precision. This capability permits direct measurement of the deposition rate. This project will use QCM and electrochemical methods to investigate how factors other than the classical parameter of temperature may be applied to reactive interfaces in order to amplify the Arrhenius rate constants of various systems. If successful, amplified rates commensurate with temperatures >100 oC could be realized.