Mark T. McDermott's research while affiliated with University of Alberta and other places

Publications (82)

Article
Recent demands for high-performance lightweight materials have brought researchers’ attention to various nanoparticles to reinforce polymeric materials. As such, sustainable and stiff cellulose nanocrystals (CNC) have become a popular candidate as nano-reinforcements. While CNC can offer great advantages, such as high mechanical properties and low...
Article
Full-text available
Nanocomposite technologies can be significantly enhanced through a careful exploration of the effects of agglomerates on mechanical properties. Existing models are either overly simplified (e.g., neglect agglomeration effects) or often require a significant amount of computational resources. In this study, a novel continuum-based model with a stati...
Article
Alkanethiolate monolayers formed on rough gold surfaces can, somewhat surprisingly, act as stronger barriers to heterogeneous electron transfer than those on smooth gold surfaces. This paper presents a possible explanation for this observation by constructing simple geometric models of a “rough” and “smooth” gold surface to examine how microscopic...
Article
A variety of different forms of carbon have found useful electrochemical applications. Thin films of carbon deposited onto an appropriate substrate by a variety of means have been explored and, in many cases, exhibit high electrochemical reactivity. Carbon film electrodes can often be used without pretreatment, and their fabrication allows for flex...
Article
A water dispersible surface-enhanced Raman scattering (SERS) substrate is developed to provide rapid and reproducible measurement of solution-borne analytes. Cellulose nanomaterials are generally dispersible in water and are known to act as a reducing agent and support for the synthesis of metal nanoparticles. In this work, cellulose nanofibers (CN...
Article
The evolution of Raman spectroscopy into a useful analytical technique has been due, in part, to the development of inexpensive, compact instrumentation and advancements in methodologies that enhance Raman intensities. Surface enhanced Raman scattering (SERS) is a primary methodology for quantitative and low detection limit measurements. While a br...
Article
Nitrobenzene (CNC‐1), trifluoromethyl benzene (CNC‐2) modified and polystyrene‐grafted (CNC‐g) cellulose nanocrystals in polystyrene (PS)‐N,N dimethylformamide (DMF) solutions were electrospun and collected as stretched and aligned fibers on a rotating drum. Scanning electron microscope pictures showed significant alignment in the case of unmodifie...
Conference Paper
Full-text available
Cellulose nanocrystals (CNC) are novel bio-based nano-fibers. Their high aspect and surface-to-volume ratios, low density, and attractive mechanical properties make them ideal candidates as a reinforcement for nanocomposites. Polyamide 6 (PA6) is one of the most commonly used thermoplastics in the world; however, the potential for CNC reinforcement...
Article
As medical practitioners' interest in hydrogels continues to grow, their new expectations in terms of mechanical properties, biocompatibility and durability are changed. Here, we demonstrated a new strategy to improve both mechanical properties and self-recovery of double network (DN) hydrogels by introducing a self-healing network, consisting of c...
Article
Full-text available
Sclerotinia stem rot, caused by the fungal pathogen Sclerotinia sclerotiorum, is a destructive disease of canola and many other broadleaf crops. The primary inoculum responsible for initiating Sclerotinia epidemics is airborne ascospores released from the apothecia of sclerotia. Timely detection of the presence of airborne ascospores can serve as a...
Article
Quantitative measurement of small-molecule metabolites is now emerging as an effective way to link the metabolite profile to disease state. Surface plasmon resonance (SPR) is a sensing platform that has demonstrated applicability for a large range of biomolecules. However, direct detection of small molecules with SPR challenges the refractive index...
Preprint
Full-text available
Ultrasensitive and selective detection and quantification of dopamine (DA) plays a key role in monitoring neurodegenerative diseases. However, the detection limit reported for DA detection is typically in the lower nM range. Pushing the detection limit to pM or lower for this particular target to cover the physiological levels (< 130 pM) is signifi...
Article
The development of sensing systems for the measurement of small molecules is an active area of research. A sensor based approach for the measurement of metabolites can potentially provide the simplicity and portability required for widespread use. Rapid detection and quantitation of small-molecule metabolites can potentially emerge as an effective...
Article
In this contribution, we demonstrate the fabrication of hollow mesoporous carbon spheres (HCSs) derived from cellulose nanocrystals. The HCSs were prepared by templating cellulose nanocrystals (CNC) on to sacrificial silica spheres followed by heat treatment. Mesoporous carbon spheres result from the removal of the silica spheres by etching. The wa...
Article
The effects of propellant type, cosolvent content, and air humidity on the morphology and solid phase of the particles produced from solution pressurized metered dose inhalers containing the corticosteroid beclomethasone dipropionate were investigated. The active ingredient was dissolved in the HFA propellants 134a and 227ea with varying levels of...
Article
Understanding synthesis and properties of nanomaterials is critical for reliable applications. Biological systems, such as fungi, have been described as a 'green' alternative to synthesis; yet knowledge gaps exist in terms of production variability, comparison with commercial products, and identifying a clear biological advantage over other synthes...
Article
Full-text available
Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incomp...
Article
Full-text available
Resonant glassy nanostrings have been employed for the detection of biomolecules. These devices offer high sensitivity and amenability to large array integration and multiplexed assays. Such a concept has however been impaired by the lack of stable and biocompatible linker chemistries. Diazonium salt reduction-induced aryl grafting is an aqueous-ba...
Article
Adhesion plays an important role in the final properties of nanocomposites. This study explored the surface interaction of cellulose nanocrystals (CNCs) and the effect of CNC sources on adhesion between individual CNCs and the Si tip of an AFM cantilever using a force mapping technique called FMap. The adhesion between CNCs and a Si tip from five d...
Article
Full-text available
Campylobacter jejuni is found in the intestines of poultry, cattle, swine, wild birds and pet animals and is the major cause of foodborne gastroenteritis in developed countries. We report the use of the receptor binding protein (RBP) of Campylobacter bacteriophage NCTC 12673 for the specific capture of Campylobacter jejuni bacteria using RBP-deriva...
Article
Tailoring the surface chemistry of metallic nanoparticles is generally a key step for their use in a wide range of applications. There are few examples of organic films covalently bound to metal nanoparticles. We demonstrate here that aryl films are formed on gold nanoparticles from the spontaneous reduction of diazonium salts. The structure and th...
Article
The successful application of nanoscale materials requires an accurate description of the shape and size of the nanomaterial. Cellulose nanocrystals (CNC) are a plant-derived nanomaterial that is currently being investigated for a variety of applications. We have developed here a method to determine the shape parameter (length/diameter) of rod-like...
Article
MicroRNAs (miRNAs) are endogenous posttranscriptional regulators found in all metazoa and play crucial roles in virtually all cellular processes. Their aberrant expression has been linked to several diseased states; therefore, techniques capable of sensitive and specific profiling of the miRNA milieu will have significant application in prognostics...
Article
Full-text available
A bioassay platform using T4 bacteriophage (T4) as the specific receptor and surface plasmon resonance (SPR) as the transduction technique has been developed for the detection of Escherichia coli K12 bacteria. The T4 phages have been covalently immobilized onto gold surfaces using a self-assembled monolayer of dithiobis(succinimidyl propionate) (DT...
Article
The minimization of sources of uncertainty in nanoindentation experiments is crucial for accurate determination of nanomechanical properties. A common source of uncertainty in these measurements is the estimation of tip shape and size. Besides the experimental determination of the indenter's real geometry, determination of the instrument's complian...
Article
Carbon-clad zirconia particles have been converted into ion-exchange media by in situ diazonium generation and thermal deposition. The surfaces prepared possess either a permanently charged anion-exchange site or a weak anion-exchange site. Surface modification optimization experiments were performed both on planar carbon surfaces and on non-porous...
Article
New methods to pattern and etch a variety of materials are proving to be extremely important owing to the broad impact of microfabrication technology on chemistry and biology. A method, for etching graphitic carbon materials that opens pathways for the creation of arrays of carbon structures, has been developed. The method involves standard photoli...
Article
The reduction of diazonium salts to produce aryl films on surfaces has expanded in application from carbon electrodes to a variety of conducting materials. The increasing interest in this method for modifying gold surfaces has motivated us to directly compare the structure and stability of nitrobenzene films derived from diazonium salts with monola...
Article
The incorporation of carbon materials in micro- and nanoscale devices is being widely investigated due to the promise of enhanced functionality. Challenges in the positioning and addressability of carbon nanotubes provide the motivation for the development of new processes to produce nanoscale carbon materials. Here, the fabrication of conducting,...
Chapter
Full-text available
Nanotechnology emerges out of fundamental science through capability for accurate, repeatable and reproducible measurements on the nanoscale which allows scientists and engineers to accumulate knowledge. Understanding the measurement science is the first step towards development of new ideas. This paper describes some research initiatives which und...
Article
The interactions between proteins and immobilized carbohydrates are crucial to biological events such as cell signaling and immune response. The modification of surfaces with carbohydrates to create sensing platforms provides a pathway to study these interactions in a laboratory setting. In this work, a family of structurally related Salmonella dis...
Article
Rapid, sensitive and inexpensive analysis of biological molecules is vital to many fundamental problems in molecular biology. Nanomechanical resonators are of great interest for such applications. The use of these devices for the analysis of protein mixtures would however require the immobilization of probes onto their surfaces in order to enable t...
Article
Glancing angle deposition was used to produce approximately 150-nm-thick silver nanoparticle films, which were evaluated as localized surface plasmon resonance (LSPR) biosensors. The films have a strong extinction peak around 368 nm in air due to LSPR. As the refractive index of the surrounding environment is increased, the extinction peak red-shif...
Article
The deposition of-nitroazobenzene (NAB) on carbon electrodes were achieved by the electrochemical reduction of 4-Nitro-4'-diazonium azobenzene tetrafluoroborate in anhydrous acetonitrile media using cyclic voltammetry technique at room temperature. The modified surfaces were examined as voltammetric electrodes for Fc/Fc+, Ru(NH3) 63+/2+, IrCl62-/3-...
Article
A variety of new methodologies to pattern biomolecules on surfaces and to detect binding events are currently being developed for high-throughput assay applications. Carbohydrates serve as attachment sites for toxins, bacteria, and viruses. Immobilized carbohydrate units can thus be used to directly detect these agents or as a platform for inhibito...
Article
This work presents a study focused on improving the sensitivity of surface plasmon resonance (SPR) imaging for protein microarrays. The research examines the effects of nanoparticle size and binding valency on observed SPR signal.
Article
A simple method is presented for patterning of protein antigens at a gold surface for use in surface plasmon resonance (SPR) imaging experiments. Microfluidic devices fabricated from poly(dimethylsiloxane) were used to flow various fluids over a gold substrate in spatially defined channels. This technique was used to pattern the surface chemistry o...
Article
A facile method for the preparation of thin-film carbon electrodes by electron beam evaporation onto highly doped silicon is presented. The physical and electrochemical properties of these films both before and after postdeposition pyrolysis are investigated. Raman spectroscopy establishes the amorphous structure of the nonpyrolyzed carbon films an...
Article
Due to the broad impact of microfabrication technology on chemistry and biology, new methods to pattern and etch a variety of materials are being explored in a number of laboratories. Here, we report the design, fabrication, and operation of a glassy carbon (GC) microchip interfaced to a nanoelectrospray ionization source and a quadrupole mass spec...
Article
Due to the broad impact of microfabrication technology on chemistry and biology, new methods to pattern and etch a variety of materials are being explored in a number of laboratories. We have developed a method for the etching of glassy carbon (GC) that opens pathways for the creation of new electrode patterns and devices. The method involves stand...
Article
Scanning force microscopy (SFM) was used to examine plasma protein films adsorbed on highly oriented pyrolytic graphite (HOPG). Single component films of bovine serum albumin (BSA) and bovine fibrinogen (BFG) were initially investigated to study the effect of protein solution concentration on film morphology. We then studied the adsorption of BFG t...
Article
This paper describes a simple and rapid electrochemical oxidative procedure that removes polishing contaminants from glassy carbon (GC) surfaces. The method involves oxidation of polished GC electrodes in basic media for short periods of time (~10 s). Tapping mode scanning force microscopy (TM SFM), X-ray photoelectron spectroscopy (XPS) and nanoin...
Article
We have employed scanning force microscopy (SFM) and nanoindentation analysis to track the evolution of tribologically generated antiwear films derived from zinc dialkyldithiophosphate (ZDDP) as a function of rubbing time. The SFM images reveal that film morphology evolves with time through a growth mechanism consisting of three stages. In the firs...
Article
Scanning probe microscopy has been used for the analysis of a wear surface from a component removed from a heavy duty diesel engine. This component is analysed and compared to a wear surface that has been generated in a rig that simulates engine conditions. It was found that the wear surface from the engine component is highly pitted in the regions...
Article
In this paper, a label-free protein array chip is presented. Surface plasmon resonance (SPR) imaging is used to measure the interactions between proteins and their corresponding antibodies. Poly(dimethylsiloxane) PDMS channels are used to pattern the protein layers on a gold coated glass surface, modified with a self-assembled carboxylic acid termi...
Article
This paper describes the adsorption mechanisms and aggregation properties of cetyltrimethylammonium bromide (CTAB) and didodecyldimethylammonium bromide (DDAB) surfactants that are used for dynamic coatings in capillary electrophoresis (CE). Atomic force microscopy is used to directly visualize surfactant adsorption on fused silica. It was found th...
Article
The functionalization of carbon electrodes with aryl films can be achieved via the electrochemical reduction of the corresponding diazonium salt. We have previously shown that this deposition procedure will produce multilayer films on ordered graphite under certain conditions. We examine here the formation of multilayer films on glassy carbon (GC)...
Article
This paper reports a simple experimental technique developed to measure strains in fibre-reinforced plastic (FRP) tensile micro-specimens (nominal thickness: 254 μm) before and after these were exposed to a 50-50 volumetric mixture of methanol and ASTM Fuel C. Micro-specimens were used to reduce the time required for the fuel mixture to diffuse int...
Article
Zinc dialkydithiophosphate (ZDDP) materials are important antiwear/antioxidant additives in most modern lubrication formulations. The current understanding of the formation of antiwear films from ZDDP involves a tribochemical and thermooxidative component. We examine here the changes in the topography and structure of films formed by the thermooxid...
Article
In this work we combine electrochemical metal deposition with the self-assembly of thiolate monolayers in an effort to develop a novel method for attaching predefined functional groups to glassy carbon (GC) electrodes. Gold nanocrystals were electrochemically deposited on polished GC substrates by a potential step and subsequently modified by expos...
Article
In this work, we demonstrate the sensitivity of scanning force microscopy (SFM), operated in friction force mode, to adsorbed protein conformation or orientation. We employ patterned films of methyl- and carboxylate-terminated alkanethiolate monolayers on gold as substrates for protein adsorption to observe the effect of each functional group in th...
Article
Nanoscale Pt structures were prepared on highly ordered pyrolytic graphite (HOPG) by chemical vapor deposition. The organometallic compound Pt(COD)(CH3)2 (1) (COD is 1,5-cyclooctadiene) was reduced by hydrogen gas to effect the deposition of Pt. The deposited Pt was characterized by cyclic voltammetry and by tapping mode scanning force microscopy....
Article
The sensitivity of friction force scanning force microscopy (SFM) to adsorbed protein conformation or orientation was examined. Patterned films of methyl and carboxylate-terminated alkanethiolate monolayers on gold were used as substrates for protein adsorption to observe the effect of each functional group in the same image. A frictional contrast...
Article
This paper demonstrates the first application of tapping-mode scanning force microscopy (TM SFM) in the compositional mapping of modified glassy carbon (GC) electrodes. Using TM SFM, we have been able to track both compositional and topographical changes of polished GC induced by electrochemical pretreatment (ECP). Photoresist-based microfabricatio...
Article
This paper describes the nucleation and growth of functionalized aryl films on ordered graphite. The attachment of aryl groups to carbon surfaces is induced by the electrochemical reduction of the corresponding diazonium salt. This deposition procedure affords the ability to control film formation by potential cycling in a low concentration of prec...
Article
The interfacial properties of gold nanocrystals deposited electrochemically onto glassy carbon substrates are characterized. Electrochemical interrogations as well as microscopy have been utilized to examine systematically the influences of deposition solution concentration and overpotential. The results of these studies indicate that the overall s...
Article
Spontaneously adsorbed organic films can drastically influence the electrochemical reactivity of carbon materials. We report here a combined electrochemical and scanning force microscopic (SFM) study of anthraquinone 2,6-disulfonate films adsorbed to ordered graphite electrodes. The cyclic voltammetric signature of adsorbed 2,6-AQDS depends on the...
Article
Full-text available
We have used two hydroxylated naphthoquinol menaquinol analogues, reduced plumbagin (PBH2, 5-hydroxy-2-methyl-1,4-naphthoquinol) and reduced lapachol [LPCH2, 2-hydroxy-3-(3-methyl-2-butenyl)-1, 4-naphthoquinol], as substrates for Escherichia coli anaerobic reductases. These compounds have optical, solubility and redox properties that make them suit...
Article
We report here the results of a scanning force microscopic (SFM) investigation into the structure of adsorbed bovine fibrinogen films on well-defined surfaces. SFM images show that a monolayer of fibrinogen assembles on both highly oriented pyrolytic graphite (HOPG) and mica. We find, however, that the film morphology varies as a function of the su...
Article
This paper reports on the use of a scanning force microscope (SFM) for the tip-assisted base hydrolysis of an ester-terminated alkanethiolate monolayer on Au(111). We have found that contact imaging accelerates the base hydrolysis of a dithiobis(succinimido undecanoate) monolayer relative to the surrounding unimaged area. It is proposed that (1) th...
Article
This paper explores the ability of n-alkanethiolates chemisorbed at Au(111) to function as boundary lubricants at microscopic length scales as probed by scanning force microscopy (SFM). Through an examination of the influence of alkyl chain length, we show that the macroscopic structure of this system, as developed from insights into the chain-pack...
Article
This paper demonstrates the real time monitoring of the electrochemical transformation of a surface-bound redox species using AFM-based adhesion measurements. The measurements were conducted using a monolayer formed by the chemisorption of 11-mercaptoundecyl ferrocenecarboxylate (FcT) at a Au(111) electrode and a gold-coated probe tip modified with...
Article
Scanning tunneling (STM) and atomic force (AFM) microscopies have been used to examine structural features of monolayers formed from the spontaneous adsorption of alkanethiols at Au(111) surfaces. In addition to the atomic scale spacings of the adlayer, the depressional features found in both large (50-250 nm) and atomic scale images have been char...
Article
This paper demonstrates the ability to map chemically distinct domains at nanometer length scales using frictional force microscopy (FFM). The basis of this characterization is the dependence of the frictional interactions on the identity of the chemical functional groups at the outermost few angstroms of microscopic contacting areas, i.e., the sur...
Article
Electron transfer kinetics and adsorption were examined at several carbon surfaces, including basal plane highly ordered pyrolytic graphite (HOPG) and glassy carbon (GC). The objective was an understanding of how surface structure affects reactivity. HOPG basal plane exhibited much slower electron transfer rates than GC for all systems studied, and...
Article
Adsorption was examined on STM-characterized graphite and glassy carbon surfaces, in order to relate adsorption behavior to specific surface structures; The adsorption of four electroactive quinones was determined voltammetrically on highly ordered pyrolytic graphite (HOPG) and fractured glassy carbon (GC). The average surface coverage on HOPG was...
Article
Electron-transfer rates for 17 inorganic redox systems plus methyl viologen were determined on highly ordered pyrolytic graphite (HOPG) and glassy carbon (GC). Provided the HOPG defect density is low, the electron-transfer rates of all systems are much slower on the basal plane of HOPG than on GC. The slow rates on HOPG show a trend with the homoge...
Article
Polished, fractured, heat-treated, and laser-activated glassy carbon (GC) surfaces were examined by scanning tunneling microscopy (STM) in ambient air. Polished electrodes, as well as those which were vacuum heat treated (VHT) or laser activated (25 mW/cm2) after being polished, were comparably smooth in 2.5-mum STM scans, exhibiting root-mean-squa...
Article
The adsorption of anthraquinone-2,6-disulfonate, disodium salt (AQDS), was found to be well behaved at glassy carbon (GC) and highly oriented pyrolytic graphite (HOPG) electrodes. On laser-activated GC, the surface excess obeys a Langmuirian isotherm in the concentration range of 5 x 10(-8) to 1 x 10(-5) M with a saturation coverage of 228 pmol/cm2...
Article
The fullerenes exhibit a remarkable ability to accommodate excess negative charge. We have observed C60(2-) and C70(2-) in a Fourier transform ion cyclotron resonance mass spectrometer by laser desorption (1.064-mu-m) of raw fullerene material that had been extracted from soot produced from graphite rods. C60(2-) was distinguished from C30- by the...
Article
Highly oriented pyrolytic graphite (HOPG) has been studied by several groups as an electrode material, due mainly to its well-defined surface structure compared to more commonly used materials such as glassy carbon. The basal plane of HOPG is also a common standard for scanning tunneling microscopy because it is atomically flat over regions up to a...
Article
The fullerenes exhibit a remarkable ability to accommodate excess negative charge. We have observed $C_{60}^{2}-$ in a Fourier transform ion cyclotron resonance mass spectrometer by laser vaporization of raw fullerene material which had been extracted from soot produced with graphite rods. A variety of tests were performed to verify the existence o...
Article
Microfabrication has had a considerable impact in many areas of chemistry and biology. The application of processes such as metal deposition, lithographic pattern transfer and etching techniques to a variety of materials has enabled, for example, the development of lab-on-a-chip devices, microelectromechanical systems (MEMS), miniaturized sensor sy...
Article
The ability to rationally design interfaces for biosensors, implants, etc., with predefined control over protein adsorption will only be realized with the aid of techniques that can rapidly analyze surface induced variations in protein conformation and orientation. Several groups have demonstrated that the friction force mode of contact SFM is sens...

Citations

... The two-parameter model of agglomeration based on the Eshelby-Mori-Tanaka approach was implemented through the finite element method. Demir et al. [23] developed a continuum-based model of agglomerated nanocomposite with a statistical approach based on a modified three-phase Mori-Tanaka model. ...
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