Chemistry Speaker Tour 2018-09-17T13:17:08+00:00

2018-19 Chemistry Speaker Tour

Dr. Danielle Tokarz
Dr. Danielle TokarzSaint Mary’s University


Sep. 21, Cape Breton University
Oct. 12, Mount Allison
Oct. 18, Acadia

Advances in Nonlinear Optical Microscopy

Exposing the structure and function of living tissues and cells is instrumental to the advancement of biochemistry and biophysics. Nonlinear optical microscopy can provide such information by exploiting polarization resolved nonlinear light-matter interactions. The caveat is that only select biological structures generate nonlinear optical signals. The first part of the talk will feature how in vivo structural specificity can be achieved by introducing new biocompatible molecular dyes with high nonlinear optical properties for third harmonic generation (THG) microscopy. The second part of the talk will discuss how the nonlinearity of molecules inside tissues can be utilized to discern structure noninvasively.

Potential molecular dyes for nonlinear optical microscopy were investigated. An analytical technique for measuring the nonlinear optical properties of molecules was established to measure the second hyperpolarizability of potential labels, consisting of two distinct experimental analytical setups. Carotenoid and chlorophyll THG dyes were investigated, and labeling of cultured cells was performed in a proof of principle experiment.

Polarization-sensitive second harmonic generation (SHG) and THG microscopy techniques were used to study the nonlinear optical properties and structure of aggregates containing chlorophylls and carotenoids in orange carrots and algae, as well as collagen in and around tumor tissue. These studies demonstrated that polarization-sensitive SHG and THG microscopy can provide quantitative structural information on a number of molecules and polymers found within biological organisms and tissues, and can even be used for early cancer diagnosis.


Dr. Tokarz is an Assistant Professor with the Department of Chemistry at Saint Mary’s University in Halifax, Nova Scotia. She is an experimentalist with expertise in the analytical measurement of light-matter interactions in biological and artificial nanosystems. She has a broad interest in improving knowledge by studying fundamental processes of primary photosynthesis, energy storage, and tissue biomechanics, and she does so in a variety of biological and artificial systems. She is particularly interested in new quantitative nonlinear optical techniques for improved understanding of bio-nanomechanics for elucidation and early diagnosis of disease and wound healing, and to enhance plant output for applications in food, natural products and biofuels production.

Danielle manages an interdisciplinary and independent research program, currently focused on constructing a novel nonlinear optical microscope, which can noninvasively measure the structure of tissues during biological changes, and measuring nonlinear optical properties of molecules for advanced noninvasive analysis of biological targets. The microscope will be the first in Atlantic Canada and one of a handful in the world which has the capability to perform polarization resolved optical structural measurements of artificial and biological tissues.

Danielle Tokarz holds H.B.Sc. and Ph.D. degrees in chemistry from the University of Toronto. During her Honours chemistry thesis project, she built her own spin coater from household items which impressed physics faculty members and encouraged her to pursue interdisciplinary studies. She subsequently performed her doctoral research at the Mississauga campus under the joint supervision of Dr. Virginijus Barzda (Department of Physics) and Dr. Ulrich Fekl (Department of Chemistry) on the nonlinear optical properties of molecules. Soon after completing her degree, she began a postdoctoral fellowship with Dr. Brian C. Wilson at the University Health Network in Toronto, focusing on collagen structure in tumor tissue. Danielle demonstrated a new nonlinear optical analysis technique for detecting microscopic changes in human tissues due to tumor progression. The technique is poised to impact the next generation of hospital biopsy slide scanners, revealing the presence of tumor in micron-sized regions.

After her PhD, Danielle received an NSERC postdoctoral fellowship and moved to the group of Dr. Charles P. Lin at the Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School in Boston, where she worked on developing a new microscope for imaging inside bones of live mice. She performed pilot studies showing the structure of the lacunar-canalicular network of bone cells changes with hypophosphatemic rickets, which influenced how researchers can measure bone disease progression, enabling live feedback of disease progression in living animals with potential use during drug testing.

Past Chemistry Speaker Tours

Dr. Aaron Kelly
Dr. Aaron KellyDalhousie University


Oct. 24, UPEI
TBA, Memorial

Photo-Induced Charge and Energy Transfer in Chemistry:

During individual chemical reaction events, such as when a molecule changes shape or transfers an electron to one of its neighbours, thermal energy and electric charge flow. These processes are especially important when a molecular system interacts with light; after the light energy is absorbed the system must then find some way to “relax”. Describing these types of processes from a theoretical perspective requires the development and application of simulation methods that lie at the interface of statistical mechanics and quantum dynamics. Combining these areas is essential to accurately capture these fundamental chemical steps in many forefront problems ranging from solar energy conversion and chemical catalysis to biological sensing and signaling. Molecular simulations of this type can help uncover the underlying mechanisms that lie at the heart of many energy conversion problems, and the ultimate goal of my research program is to extend and apply these approaches to study light-initiated charge and energy transport. In this talk, I will describe the efforts we are making to simulate charge and energy transfer in laser-driven chemical reactions, molecular wires, and biological light-harvesting systems.


Aaron Kelly received his B.Sc. with Joint Honours in Chemistry and Physics from Memorial University and a Ph.D. in Chemical Physics Theory at the University of Toronto. He has held postdoctoral research positions at the Pohang University of Science and Technology (South Korea, 2010-2011), Stanford University (USA, 2011 – 2015), and the Max Planck Institute for the Structure and Dynamics of Matter (Germany, 2016-2017). He is currently an Assistant Professor of Chemistry at Dalhousie University, and a Visiting Scientist at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany. His research interests focus on the development and application of quantum dynamics approaches to treat charge and energy transfer processes in condensed phase systems.

Past Chemistry Speaker Tours