Dan Bizzotto

Professor

Research Classification

Electrochemical Systems
Surface Characterization
Surfaces, Interfaces and Thin Layers
Sensors and Devices
Electrochemical and Fuel Cells

Research Interests

Electrochemistry
interfacial analysis
biosensors
spectroelectrochemistry
electrocatalysis
self assembled monolayers
fluorescence microscopy

Relevant Degree Programs

Affiliations to Research Centres, Institutes & Clusters

 
 

Research Methodology

surface analysis (AFM, FTIR, fluorescence microscopy)
electrochemical analysis
Electrochemical Impedance Spectroscopy
fluorescence microscopy of electrochemical interfaces
characterizing electrochemical biosensors

Recruitment

Master's students
Doctoral students
Postdoctoral Fellows
Any time / year round

Characterizing modified electrochemical interfaces Electrochemical biosensors Electrocatalysis Spectroelectrochemical studies of DNA modified electrodes

I support public scholarship, e.g. through the Public Scholars Initiative, and am available to supervise students and Postdocs interested in collaborating with external partners as part of their research.
I support experiential learning experiences, such as internships and work placements, for my graduate students and Postdocs.
I am open to hosting Visiting International Research Students (non-degree, up to 12 months).
I am interested in hiring Co-op students for research placements.

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Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - Nov 2019)
Electrodeposited DNA monolayers on gold: creation, evaluation and optimization (2019)

No abstract available.

Pt ionomer composite films (2019)

No abstract available.

Spectroelectrochemical Characterization of Self-Assembled Monolayers on a Single Crystal Au Bead Electrode: The Influence of Surface Crystallography (2017)

Self-assembled monolayers (SAMs) are important structures commonly employed to functionalize metal surfaces. To optimize a metal-SAM construct, it is important to characterize the influence of the surface crystallography. In this thesis, a single crystal Au bead electrode was employed to investigate different types of SAMs, enabling studies on a variety of surfaces under identical conditions and avoiding laborious experimental replicates on a large number of crystal orientations.The application of a single crystal Au bead electrode was demonstrated by investigating the reductive desorption process for two types of SAM: the alkanethiolate SAM and the α-aminoisobutyric acid (Aib) peptide thiolate SAM. Using in situ fluorescence imaging, the influence of surface crystallography on reductive desorption was observed, reflected as a correlation between the density of broken bonds of a surface and the reductive desorption potential of a SAM deposited on the surface. Besides the surface crystallography, intermolecular interactions also had a significant impact on determining the desorption potential.Aib peptide thiolate SAMs on a Au(111) facet were further investigated. It was found that the low packing density Aib peptide thiolate SAMs exhibited a potential-modulated fluorescence response which was believed to be due to the orientational or structural change of the peptide molecules in response to the applied potential.The potential-driven reorientation effect of the DNA SAMs has been intensively explored due to its application in biosensing. Characterization of the DNA SAMs with in situ fluorescence methods suggested that surface crystallography exerts an influence not only on the formation of the DNA SAMs but also on the efficiency of the potential-driven response. Moreover, a spectroelectrochemical technique that couples electrochemistry, fluorescence microscopy and harmonic analysis was developed to explore the non-linearity of the fluorescence response to an applied AC potential. This technique could be potentially applied to detect changes in DNA hybridization state.The experimental results demonstrate the convenience and wide applicability of using a single crystal Au bead electrode to investigate SAMs. On the other hand, applying existing and developing new spectroelectrochemical techniques give insights into creating SAMs with desirable properties.

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Spectroelectrochemical Characterization of Ultrathin Organic Films Deposited on Electrode Surfaces (2014)

Thin organic layers deposited on electrodes are ubiquitously proposed for a variety of surface-related applications. The quality of these layers is usually assessed by analytical methods that average the measured signal over a large area compared to the molecular scale. This work outlines the use of in-situ fluorescence microscopy as a characterization method by analyzing three examples of such layers.First, a heterogeneous Langmuir layer was physically adsorbed to a gold electrode via the Langmuir-Schaefer method and the effects of the substrate analyzed by comparing the adsorbed layer with the predecessor floating film. Through the use of a dimer-forming fluorophore, substrate mediated condensation was suggested.Second, the reductive desorption of self-assembled monolayers (SAMs) from microelectrodes was used to investigate the movement of the released thiolate molecules. Once in solution, these molecules were found to follow a buoyant movement, consequence of the high local concentration of H₂ resulting from the simultaneous reduction of water under the conditions employed.Finally, a DNA SAM system that has been previously suggested as a biosensing platform was investigated for heterogeneity. It was found that the substrate crystallography had a significant effect on the density and efficiency of potential driven change in conformation of the immobilized probes. Furthermore, a deconvolution method is proposed in order to correct for the effect of the electrode charging time constant on the measurements of the kinetics of the DNA conformation change.Overall, the performed experiments show that in-situ fluorescence microscopy is a useful technique to analyze distance dependent phenomena involving these deposited layers. Moreover, the coupling between electrochemistry and fluorescence allows not only to monitor but also to drive changes in the layers, creating systems capable of studying the dynamics of the deposited films.The inclusion of the proposed technique as a characterization tool during the development of systems based on ultrathin organic films could improve the understanding of the influence of the deposition conditions on the film quality, helping to attain the necessary robustness to make the proposed systems actually achieve their proposed applications. Supplementary video material is available at: http://hdl.handle.net/2429/51003

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Electrochemically controlled interaction of liposomes with a solid-supported octadecanol bilayer (2013)

Transmembrane proteins and ion channels are a major target for new drug development.Incorporating them into sensors requires a method to produce stable, easilymodifiable solid-supported phospholipid bilayers. This thesis demonstrates amethod for using potential control on the electrode to mediate liposome adsorption,allowing them to interact with a previously deposited octadecanol layer throughpotential-created defects.Compression isotherms and electrochemical measurements were used to establishthe effect of the incorporation of a small amount of fluorescent dye on theoctadecanol layers. Using these fluorescently-labelled octadecanol layers, electrochemicalmeasurements both independently and coupled with in-situ fluorescencemeasurements were used to characterize the interaction of liposomes with theselayers under potential control. It was found that application of moderate potentials- more negative than the onset of defect formation but less than that required fordesorption of the layer - facilitated the effective incorporation of liposome materialinto the octadecanol bilayer. The length of time spent at the poration potential hadlittle effect on the degree of liposome interaction with the adsorbed layer. The incorporationwas seen as a change in the double-layer capacitance and the creationof small fluorescent structures in the layer after exposure to liposomes at the porationpotential. A shift in the characteristic desorption potential was also seen withliposome incorporation.Atomic force microscopy coupled in-situ with electrochemical control was alsoused to investigate the interaction of liposomes with the adsorbed octadecanol layer.The structure of the adsorbed layer was observed and with liposomes present insolution, the creation of three-dimensional structures similar in nature to those seenby fluorescence was noted. The incorporation of liposomes into the octadecanolwas shown to be easily controlled by application of an electrical potential, openinga path for a new method of producing supported lipid bilayers in-situ for biosensingapplications.

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Microstructure evolution in electrodeposited copper thin films for advanced microelectronic applications (2012)

Copper interconnects in advanced integrated circuits are manufactured by processes that include electrodeposition, chemical mechanical polishing and annealing. The as-deposited copper is nano-crystalline and undergoes a microstructure evolution at room temperature (self-annealing) or during an annealing step. During this process, significant changes in resistivity and grain size are observed. In this work, the microstructure evolution in 0.5-3 μm-thick electrodeposited copper thin films was studied. Resistivity measurements were used to quantify the role of deposition conditions on the microstructure evolution rate. In-situ electron backscatter diffraction (EBSD) was employed to observe self-annealing at the film surface. The resistivity-microstructure correlation during self-annealing was examined. A phenomenological model using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) approach was developed to describe recrystallization during isothermal and continuous annealing treatments. The microstructure evolution in copper-silver alloys and films produced by variable deposition rates was investigated. Phase-field model was applied to simulate self-annealing and the effect of deposition current density.The results show that the drop in resistivity during self-annealing is accompanied by significant changes of the microstructure at the film surface. Different criteria were developed to assess self-annealing rate from EBSD maps including grain size, image quality and local orientation spread. Adopting a grain size threshold, it was found that there is a reasonable correlation between resistivity and microstructure during self-annealing. The recrystallization in copper thin films appears to be thermally activated with an activation energy of 0.89-0.93 eV. Adopting the principle of additivity, it was found that the recrystallization rate during continuous annealing can be described by the JMAK model using the isothermal resistivity profiles. A method was proposed to accelerate recrystallization based on a capping layer deposition. No recrystallization was observed when silver was co-deposited with copper in the absence of chloride (even when annealed at 100 °C for 5 hours). Phase-field model was able to describe self-annealing and the effect of deposition current density. The results in this thesis are of significance to the microelectronic industry where recrystallization is a crucial step in the fabrication of copper interconnects for the high performance integrated circuits.

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Electrocatalysis on P+Zn Surface - Fundamental Studies and the Applications in PEM Fuel Cells (2009)

No abstract available.

Calcium Vapour Deposition on Semiconducting Polymers Studies by Adsorption Calorimetry and Visible Light Absorption (2008)

No abstract available.

Master's Student Supervision (2010 - 2018)
Optimizing surface modifications for quantum dot self assembled monolayers (-via surface mediated DNA hybridization) on monocrystalline gold bead electrodes using electrochemistry coupled fluorescence imaging (2018)

Surface hybridization of DNA strands on electrode surfaces (probes) with complementary DNA strands in solution (targets) forms the basis of several electrochemical biosensors used to detect nucleic acids of interest. This work aims to construct a site-selective assembly of probe strands on only some parts of the electrode surfaces to study specific and non-specific surface interactions of target strands during the hybridization step. The target strands used in this work have been precisely tailored onto a Quantum-dot (QD) surface. This ties to the larger goal of the project of assembling QDs on electrode surfaces. Such a surface has potential widespread bio-sensing application owing to QDs unique optical and surface properties. Monocrystalline gold bead electrodes displaying different surface features were coated in 11-Mercapto-1-undecanol solutions (or MUDOL). MUDOL was reductively removed by applying negative potentials only from some surface features of the electrodes. Subsequently, AF488 fluorophore tagged DNA strands were assembled onto these surface features either directly or following an assembly of 6-Meracpto-1-hexanol (or MCH) spacer molecules. The value of the applied negative potential, the DNA concentration used and time of electrode immersion in DNA solution were optimized to form low probe surface coverages and low probe surface densities. Preliminary hybridization experiments in the absence or presence of divalent Magnesium ions in the target solutions (containing either 0.2 DNA strands per QD, 2 DNA strands per QD or 10 DNA strands per QD bioconjugates) at room temperature or at an elevated temperature of 45°C were attempted. These surfaces were studied using a fluorescence microscope coupled with an electrochemical control. The results indicate that some of the targets interact with the surface probes non-specifically through weak van der Waals forces or may exist in a partially hybridized state. A small fraction of targets is able to hybridize (specifically interact) with the surface probes, and a still smaller fraction is stable at applications of negative potentials. It might be possible that the negative potentials induce electrochemical melting or dehybridization readily as the bulky nature of the QDs prevent a stable hybridized state.

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Optimizing electrochemical and electroless methods toward the surface-specific modification of Au nanorods (2017)

The controlled modification of gold nanorods has important implications for their successful applications in a wide variety of fields. In this work, electrochemical and electroless methods for the surface-specific modification of gold were optimized with the aim of developing a site-specific strategy for the functionalization of gold nanorods.Electrochemistry and fluorescence microscopy techniques were used to investigate the surface-specific modification of alkanethiol-coated gold bead electrodes, which served as a macroscopic model system for the nanorods. 11-mercaptoundecanoic acid (MUA) was partially removed from the electrodes by reductive desorption and the uncovered regions were modified with a fluorophore-functionalized, thiolated DNA molecule. Single crystal gold bead electrodes were employed in order to study and optimize the modification methods on all crystallographic surfaces under identical conditions.Two methodologies for the surface-specific modification of gold bead electrodes were investigated. In the first, a potential was applied to the electrode using a potentiostat, and it was determined that the SAM could be reductively removed selectively from the Au{111} surfaces of the electrodes by a 5 minute electrochemical application of any potential from -0.75 V to -0.8 V vs. Ag|AgCl. In the second method, the electrode potential was set electrolessly by adding a strong reducing agent, sodium borohydride, to the electrolyte. In the absence of oxygen, it was found that the electroless MUA desorption closely resembled the results obtained electrochemically, and that Au{111}-selective modification of the gold bead electrode was achieved at potentials near -0.75 V vs. Ag|AgCl.The electroless modification strategy was then applied to MUA-stabilized gold nanorods. Preliminary results indicate that sodium borohydride successfully removes alkanethiol fromgold nanorod surface, enabling them to be modified with thiolated, fluorophore-labelled DNA.

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Electrochemical characterization of carminic acid towards the use as an electrochemical molecular beacon for nucleic acid detection (2015)

Worldwide, more than a million people die from tuberculosis (TB) every year. Although the disease is curable, treatment is complicated by multi-drug resistant and extensively drug-resistant TB strains. To detect TB and differentiate between its strains, a sensitive and specific point-of-care device is required. Previous studies show that carminic acid (CA), an anthraquinone derivative, is suitable as an electrochemical molecular beacon due to the ability to switch on and off its electrochemical activity on its dimerization.Characterization of the electrochemical activity of CA at low concentrations (1 μM to 1 mM) over a range of pH values was performed using methods such as cyclic voltammetry, square wave voltammetry and Koutecky-Levich analysis on a rotating disk electrode. CA species of different protonation, which are predominant at pH 1.1, pH 4.1, pH 6.6 and pH 10.5, were examined in more detail. All measurements were carried out on a glassy carbon electrode in phosphate buffer solution electrolyte.It was found that CA undergoes a diffusion limited two proton two electron redox reaction with an overall peak potential shift of 61 mV per pH unit. Electrochemical measurements of the fully protonated CA resulted in additional current peaks that were assigned to an adsorption process of a CA reduction product. Generally, CA has faster electron transfer kinetics in more acidic environment and no electrochemical activity was observed for the fully deprotonated CA species at pH 10.5. While SWV could be used for quantitative analysis of CA for the concentrations up to 1 mM, its redox current signal was determined not to be concentration dependent at high measurement frequencies. These frequencies can also be adjusted to be more sensitive towards either the redox peak potentials with sharper peaks at low frequencies or the electron transfer kinetics based on kinetic dependent peak currents at high frequencies. The limit of detection for CA at pH 7.0 was found to be as low as 10 nM when measured using 200 Hz SWV.

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