Physical Chemistry, Materials Chemistry, Nanoscale Science and Engineering
- B.Sc. Physics, Sharif University of Technology, Iran 1999
- M. Sc. Physics, Sharif University of Technology, Iran 2001
- Ph.D. Physics, University of Waterloo, 2007
- Post-Doctoral associate, Chemistry, University of Toronto, 2007-08.
- NSERC Post-Doctoral Fellow, Chemistry, University of Wisconsin-Madison, 2009-11.
Our group is interested to study the effect of nano-confinement on structure, dynamics and other properties of materials. Materials behave differently on surfaces, interfaces or small length scales compared to their bulk properties. Understanding such differences are crucial in many technological applications where materials are constrained in nanometer size spaces, such as organic electronics, polymer applications and drug delivery. One can take advantage of such difference to produce novel materials, such as exceptionally stable glasses or harvest light for various applications. In biological systems, most of the dynamics happens in nanometer size proximity of surfaces and interfaces, and understanding the properties in confinement is a key in predicting function. We focus our efforts on understanding the origins of such modified properties on a fundamental level as well as possible application of such phenomena in producing novel materials or experimental tools. For more details please see our website at:
Enhanced Mobility at the Surface of Polymeric and Organic Glasses:
We study the properties of glasses at the air/glass interface. Our studies show that below the glass transition temperature, where the bulk of the material is in an out of equilibrium state, the interfacial dynamics are many orders of magnitude faster that the bulk dynamics. As a result a layer close to the interface maintains equilibrium properties. We study the dynamics of this layer, its thickness, and its effect on the properties of the underlying glass. The interfacial layer can strongly modify properties of amorphous materials in nanometer length scales. They also allow one to produce near-equilibrium structures at temperatures well below bulk glass transition temperature, through physical vapor deposition.
Exceptionally Stable Glasses:
The enhanced mobility of the interfacial layer allows us to produce near-equilibrium glasses at temperatures well below the bulk glass transition temperature, Tg, by means of physical vapor deposition (PVD). Exceptionally stable glasses are formed when the substrate temperature during PVD is maintained just below the glass transition temperature. We study the morphology and the kinetics of PVD films during formation and their relationship to the final properties of the stable glass. These studies provide information on mechanisms of rapid aging below Tg and stable glass formation. We also investigate exceptional material properties of these glasses and the role of the chemical structure in these properties such as the optical birefringence and electronic properties.
Novel Emergent Optical Properties in Disordered Nanoparticle Clusters:
Using simple synthetic routs we can produce dielectric core-gold shell nanoparticles decorated with randomly packed nanoparticles of various shapes and sizes. Spiky nanoparticles are a good example of such nanoparticles. Broadband and tunable structure of spiky gold nanoshells makes them ideal for various applications such as enhanced Raman scattering, temperature and index sensing and sensors for biological and light harvesting applications. Exceptional properties, such as higher order quadrupoloar scattering and magnetic dipole plasmons in these nanoparticles are due to inherent disorder in their structure and random packing arrangements. We explore optical properties of these nanoshells, using various theoretical and experimental tools. We also develop new techniques that allow us to study properties of meta materials formed from these types of particles.
Surface Mediated Self-assembly of Amyloid Aggregrates:
Surface self-assembly provides an alternative pathway for amyloid aggregation that is not available in bulk solutions. We us high-resolution atomic force microscopy and other imaging techniques to study the adhesion and diffusion of peptides on various surfaces and their role in facilitating amyloid fibril formation through self-assembly routs. We also use our exceptional capabilities in high-resolution imaging to study the conformation of amyloids formed under various conditions in aqueous conditions.
1. Tianyi Liu, Annemarie L. Exarhos, Ethan C. Alguire, Feng Gao, Elmira Salami-Ranjbaran, Kevin Cheng, Tiezheng Jia, Joseph E. Subotnik, Patrick J. Walsh, James M. Kikkawa, and Zahra Fakhraai, “Birefringent Stable Glass with Predominantly Isotropic Molecular Orientation”, Physical Review Letters, 119, 095502 (2017).
2. Ethan C. Glor, Gabriel V. Angrand, and Zahra Fakhraai, “Exploring the Broadening and the Existence of Two Glass Transitions Due to Competing Interfacial Effects in Thin Supported Polymer Films”, The Journal of Chemical Physics, 146, 203330 (2017).
3. Yue Zhang and Zahra Fakhraai, “Decoupling of Surface Diffusion and Relaxation Dynamics of Molecular Glasses”, Proceedings of the National Academy of Sciences, 117, 4915–4919 (2017).
4. Ethan C. Glor, Robert C. Ferrier, Chen Li, Russell J. Composto, and Zahra Fakhraai. "Out-of-Plane Orientation Alignment and Reorientation Dynamics of Gold Nanorods in Polymer Nanocomposite Films." Soft Matter 13, 2207-2215 (2017).
5. Y. Zhang, and Z. Fakhraai, "Invariant Fast Diffusion on the Surfaces of Ultrastable and Aged Molecular Glasses", Phys. Rev. Lett., 118, 066101 (2017).
6. Y. Lin, H. Komatsu, J. Ma, P. H. Axelsen and Z. Fakhraai, "Quantitative analysis of amyloid polymorphism using height histograms to correct for tip convolution effects in atomic force microscopy imaging", RSC Advances ., 6, 114286 (2016) .
7. Y. Zhang, E. Glor, M. Li, T. Liu, K. Wahid, W. Zhang, R. Riggleman and Z. Fakhraai, "Long-range correlated dynamics in ultra-thin molecular glass films", J. Chem. Phys. 145, 114502 (2016)
8. Z. Qian, S.P. Hastings, C. Li, B. Edward, C.K. McGinn, N. Engheta, Z. Fakhraai and S.J. Park,"Raspberry-like Metamolecules Exhibiting Strong Magnetic Resonances", ACS Nano, 9,1263–1270 (2015).
9. Y. Lin, E.J. Peterson, and Z. Fakhraai, "Surface Effects Mediate Self-Assembly of Amyloid-β Peptides", ACS Nano, 8, 10178–10186 (2014).
10. S. P. Hastings, P. Swanglap, Z. Qian, Y. Fang, S.J. Park, S. Link, N. Engheta, and Z. Fakhraai, "Quadrupole-Enhanced Raman Scattering", ACS Nano, 8, 9025–9034 (2014).