Diffraction sensing is explored as a possible means to improve upon the limit of detection and detection time in measuring antibiotic susceptibility. The goal of this research area is twofold: 1) to decode the unique light-cell diffractive interactions in the search for new, more powerful biosensor technologies and 2) to develop new tools to better understand bacterial-surface interactions and the complex thermodynamics that govern them. Up until now, work has mainly focused on immobilizing bacterial cells in diffractive patterns with the help of electrostatics, micro contact printing, and micro molding. These patterns produce a detectable diffraction pattern when illuminated with a laser, and diffraction intensity changes are monitored as cells grow or die in the presence of antibiotics. To further understand bacterial-surface preferences and optimize cell capture, bulk and surface cell concentrations are compared using adsorption isotherms to estimate the free energy of adsorption on various surfaces. Experiments are currently focusing on studying these interactions on controllable, charged polyelectrolyte multilayer surfaces in micro-fluidic channels.

Researcher: Nicholas K. Kotoulas


Our work focuses on the applications of visible light photocatalytic materials in waste water treatment applications. To date, research has been focused on TiO2-graphene composites and BiOX materials to tackle anthropogenic sources of pollution in our water. The bulk of this work involves the synthesis and characterization of photoactive nano materials. New techniques have been developed using Q-NMR to more accurately understand the complex interactions between photocatalytic materials and the degradation process. Future work will continue to study and optimize material properties and begin applying the materials to solve environmental issues inckuding wasste water treatment, air purificatioin and antibacterial self cleaning.

Researchers: Reece Lawrence, Mark Croxall

Carbon nitride is a promising material for photocatalysis due to its ability to absorb in the visible region and its cheap producibility. Unfortunately, it is disadvantaged by its high recombination rates which limits the amount of free carriers it can produce. This research focuses on lowering the recombination rate of carbon nitride through doping the material with transition metals, which could potentially induce a polarization effect that increases the separation of the material electron-hole pairs. A potentiostat has been designed and built to measure the resulting photocurrent response. We plan on further modifying our instrument to characterize our materials through cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry.

Researcher: Fa-Yuan (Lawrence) Wang


Natural, biodegradable polyelectrolytes, such as the glycosaminoglycan hyaluronic acid, are currently studied to determine their suitability as polymeric nanoparticle active ingredient delivery systems. The phenomena of counter-ion condensation describes exposure to high ionic strength conditions masks the charges distributed along the polymer’s structure, reducing interchain repulsion and changing conformation from linear to collapsed. By optimizing conditions of polymer collapse, the chemical environment of the interior of the polymer nanoparticle may be described, and encapsulation of suitable active ingredients follows. Nanoparticle structure is maintained by irreversible chemical cross-linking utilizing carbodiimide chemistry. Characterization includes kinematic viscosity, dynamic light scattering, zeta potential, atomic force microscopy, FTIR and absorbance spectroscopies.

Researcher: Charlotte Wallace

Several nanoparticle materials can be synthesized using the polymer collapse method invented in our group. Research in this area has spurred a number of projects and a successful company Vive Crop Protection. To date we have synthesized metallic nanoparticles (Ag, Au, etc), quantum dots (CdSe, CdTe, etc) transition metal oxides (TiO2, WO3) and lanthanum oxides. Current work is continuing to better understand factors involved in the collapse and expand the 'menu' of particles which can be synthesized, starting with copper alloys.

Researcher: Mark Croxall


Light Up the World

In celebration of UNESCO’s declaration of 2015 as the International Year of Light, the Impact Centre set out on a challenge to light up the world. This challenge was sparked by Professor Cynthia Goh who grew up in a remote part of the Philippines without electricity. Many such communities in developing countries do not have access to the electric grid. This means that after sundown, the light goes out. To tackle this ‘light poverty’, Prof. Goh mobilized her team at the Impact Centre, and the rest of U of T to design and create a practical, cost-effective lighting system for low-resource settings to help ensure access to a reliable overhead light source. For more information, click here.