Abstracts

We use molecular design, tailored syntheses, intermolecular interactions, and selective chemistry to explore the ultimate limits of miniaturization. We direct molecules into desired positions to create nanostructures, to connect functional molecules to the outside world, and to serve as test structures for measuring single or bundled molecules. Interactions within and between molecules can be designed, directed, measured, understood, and exploited at unprecedented scales. Such interactions can be used to form precise molecular assemblies, nanostructures, and patterns, and to control and to stabilize function. We selectively test hypothesized mechanisms of function by varying molecular design, chemical environment, and measurement conditions to enable or to disable function and control using predictive and testable means. Critical to understanding these variations has been developing the means to make tens to hundreds of thousands of independent single-molecule/assembly measurements in order to develop sufficiently significant statistical distributions, while retaining the heterogeneity intrinsic in the measurements. We use a number of excitation mechanisms to induce changes in the molecules and assemblies, including electric field, light, electrochemical potential, ion binding, and chemistry. We measure the electronic coupling of the contacts between the molecules and substrates by measuring the polarizabilities of the connected functional molecules. We have likewise developed and applied the means to map buried chemical functionality and interactions. The next steps are to learn to assemble and to operate molecules together, both cooperatively and hierarchically, in analogy to biological muscles. We discuss our initial efforts in this area, in which we find both interferences and cooperativity.

The carboxylic acid (COOH) functional group contains both an OH that acts as a strong hydrogen-bond donor and a C=O that is a strong hydrogen-bond acceptor. Carboxylic acid crystals are typically built by packing dimers or linear chains, and these are the structures observed in the solid state as well as when molecules are adsorbed in a single layer on a surface. However, the non-equilibrium conditions created in a rapidly drying solution create more complex structures for molecular clusters; this is particularly the case when there are additional groups that participate in hydrogen bonding, even if only relatively weakly. Multiple adsorbate/surface systems are studied using scanning tunneling microscopy, revealing a range of cluster geometries and atypical hydrogen-bonding motifs, including cyclic hydrogen bonding.

One of the many challenges for nanoscale engineering is to purposely direct the self-assembly of nanomaterials into desired patterns. Easy deposition methods (such as drop-casting) are preferable over ones that require high-vacuum, as the latter has a high cost and requires long processing time; both of which renders the method infeasible for mass production. The trade-off for ease-of-use fabrication is that intermolecular morphology of the nano-objects are likely to have some uncontrollable variation between experimental outcomes, resulting in disordered states. To achieve desired patterns, researchers rely on trial-and-error methods to understand which experimental parameters have the necessary influence on morphology. However, in systems of similar density, human perception is unable to detect subtle differences in the localized structure, which can lead to misclassifications in the amount and type of disorder in the system. In this talk, we’ll explore numerical methods where in which these disordered states can be quantified and ranked between each other when the preparation method for nanoparticle deposition at the interface is varied. This allows researchers to quickly and confidently decide on the next variation in methodological refinement by rejecting unnecessary experiments.  The only requirement needed is extracted relative positions of the objects from modern imaging techniques.

In this work we validate three carbon nanostructures such as multi-walled carbon nanotubes (MWCNTs), graphene and single-walled carbon nanohorns(SWCNHs) that are covalently bounded via various polymerization methodologies with polypyrrole and pyrrole-bearing monomers (e.g. by oxidative radical polymerization, Reversible Addition Chain Transfer polymerization- RAFT and electrochemically aided Atom Transfer Radical polymerization (e-ATRP) with carbon allotrope employed as a polymerization initiator or as coreactant). We present a preparation of stable hybrid nanostructured materials with exciting electronic effects able to store energy in electrical field by combining pseudocapacitance and electrochemical double layer capacitance. As pseudocapacitive part poly(pyrrole) is used and double layer capacitance is provided by carbon allotropes. Both parts are covalently connected and exhibit unique stability not observed in physical, non-covalently connected mixtures of both components. Obtained structures were validated microscopically (TEM), spectroscopically (Raman, FTIR, EDXS) and electrochemically (CV, DPV, CP, CC, EIS,). The created materials have shown interesting and highly structured morphologies, high specific gravimetric capacitance (350F/g and more) and life-cycle stability (up to 7500 full cycles). These structures perform well in environmentally friendly media (potassium chloride solution) and their potential to be used as building blocks for supercapacitors is discussed.

Superhydrophobic surfaces have governed increasing attention from scientists and engineers in practical applications due to their unique characteristic such as anti-corrosion, self -cleaning, oil water separation etc. Various methods have been reported for constructing superhydrophobic surfaces on metal and metal alloys, electrodeposition is considered as most facile and versatile technique. In the present study, superhydrophobic surfaces were fabricated on aluminum alloy surface by the electrodeposition of metal stearate from metal ions (Ni⁺²_, Co⁺² and Mn⁺²) and stearic acid in ethanolic solution. Surface morphology and composition of the thin films were characterized by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrum (EDS) and X-Ray diffraction. The electrodeposited thin film having a high contact angle of 161 ± 1 ° with a very low contact angle hysteresis of 2 ± 1 °, due to the presence of hierarchical micro and nano-sized structures as well as low surface energy metal stearates. The electrochemical impedance spectroscope (EIS) measurements showed that superhydrophobic thin film has superior anticorrosion properties than aluminum. Similarly, the thermal stability of the superhydrophobic thin films were also studied and results of thermal dissociation and associated activation of energy will be presented.

Medical sciences have begun to focus their attention on the use of nanomaterials to improve diagnosis and treatment of diseases with the ultimate goal of moving into personalized medicine. The need to develop more efficient drug delivery procedures motivated us to propose a novel nano-carrier based on lanthanide upconverting nanoparticles (UCNPs).

UCNPs have the attractive optical property of higher energy light production from lower energy irradiation. Upon near infrared (NIR) excitation, LiYF₄:Tm³⁺/Yb³⁺ UCNPs produce emission in the ultraviolet (UV), visible and NIR. To construct the nano-carrier, the surface of UCNPs was modified with a supported lipid bilayer (SLB) in order to increase the biocompatibility, produce water dispersability, protect the upconverting emission and give a drug-loading feature to the nanoparticles. Additionally, to photo-control the drug release, an azobenzene-modified lipid (ABZ-lipid) was assembled in the SLB onto the surface of UCNPs. ABZ is a photoswitching molecule that changes from its stable trans-isomer to the cis-isomer under UV irradiation. Upon NIR excitation, UV emission is obtained in situ from the UCNPs and transferred to the ABZ-lipid triggering the photoswitching and disrupting the SLB. As a control model, dye was loaded in the nano-carrier and its photo-control release was studied.

The rise of graphene and related 2D materials makes it possible to form heterostructures held together by weak interplanar van der Waals (vdW) interactions. Within such vdW heterostructures, currently assembled by mechanical superposition of different layers, periodic potentials naturally occur at the interface between the 2D materials. These potentials significantly modify the electronic structure of the individual 2D components within the stack and their alignment, thus offering the possibility to build up hybrid and novel materials with unique properties.

Here we take a different approach by showing that pre-programmable periodic potentials arise in bi-layered structures formed by supramolecular lattices (SLs) over graphene, making them the hybrid equivalent of fully-inorganic vdW heterostructures. In particular, we employ a photoreactive molecule ideally suited to form a SL that induces a 1D-modulated gating effect on graphene with single domains extending over areas exceeding 10⁴ nm² and stable at ambient conditions. The amplitude and sign of the potential can be modified without altering its periodicity by simply irradiating the photoreactive molecule in different solvents prior to the SL formation. Such a novel approach for tailoring the periodic potential is easily applicable to other 2D materials, highlighting the rich prospects that molecular design offers to create ad-hoc heterostructures.

The interfacial strength of Chemical Vapour Deposition (CVD) graphene on copper is only governed by a weak van der Waals force, which is a fundamental property that affects electrical behavior of graphene-based devices. Additionally, the presence of Cu changes the response of the graphene to an oxygen plasma. This study focuses on the robustness of CVD graphene on Cu exposed to a low temperature post-annealing treatment. Raman spectroscopy reveals that unlike a free standing graphene film, oxygen plasma converts it to a reduced graphene oxide — a short annealing time at low temperature can boost the critical etching time for conversion by 3.5 times. Hence, varying amounts of annealing leads to graphene exhibiting different characteristics. This tuneable behaviour of CVD graphene is attributed to the concurrent oxidation mechanism of both the graphene and Cu substrate. The Raman spectra suggests an increased adhesion strength with annealing time, suggesting some pinning effect of cuprous oxides penetrate more into the Cu through intrinsic defect sites on graphene and anchors the graphene sheet more tightly to the Cu. The ability to form patterns of reduced graphene oxide with pristine graphene on the same substrate through selective annealing can be a route to nanoscale device fabrication.

Graphene oxide (GO) sponges have been recently shown to be excellent sorbents for water contaminants due to their versatile surface chemistry and high specific surface area. Unlike colloidal GO, the resulting sponges can be easily recovered from the decontaminated water and recycled for further use. However, most GO sponges suffer from poor mechanical properties and cannot endure multiple recovery cycles. To tackle this problem, polymers have been used to improve the mechanical properties of the sponges, albeit at the cost of reduced contaminant adsorption efficiency. We report here a novel strategy based on the use of cellulose nanocrystals (CNCs) to synergistically improve the mechanical properties and contaminant adsorption capacity of nanohybrid GO sponges. We demonstrate that at their optimum content, CNCs can result in a robust scaffold which holds the GO nanosheets in place and enhances the mechanical properties of the nanohybrids. We also show that the use of 1D CNCs extensively inhibits the restacking of GO nanosheets, thus resulting in sponges with higher available surface area for contaminant adsorption.  Finally, we demonstrate that an ultrastrong nanohybrid sponge with a storage modulus of up to 800 kPa has a remarkable capacity for uptake of a wide range of water contaminants.

Organic electronic devices rely on metal coated glass substrates as the working electrode.  Typically, the solid substrate plays a passive role in device operation by supporting the device components. It will be shown that the surface can be taken advantage of to direct the preparation of electroactive.  The substrate can also be used to modify the properties of electroactive layers through post-deposition reactions.  It will be shown that post-deposition patterning and property modification are possible.

Self-assembled monolayers (SAMs) of ferrocenylalkanethiolates chemisorbed to gold surfaces were originally designed for fundamental studies of interfacial electron transfer between an electronic conductor and a molecular redox couple. We have investigated the electrochemical oxidation of ferrocenyldodecanethiolate SAMs in the presence of surface-active organic anions consisting of a hydrophobic hydrocarbon tail and hydrophilic anionic headgroup. The idea is to combine the tendency of surfactants to aggregate at solid/liquid interfaces with the preference of SAM-bound ferroceniums to pair with liphophilic anions. We show that the redox response in cyclic voltammetry (i.e., formal redox potential, formal width at half-maximum of the anodic peak, and anodic-to-cathodic peak separation) is exquisitely sensitive to the surfactant aggregation state in solution. The surfactant adsorbs to the SAM surface by specific ion-pairing interactions between the anionic head groups and the oxidized ferroceniums. A longer alkyl chain length results in a larger ion-pair formation constant, resulting in ferrocene oxidation at lower potential. Finally, we demonstrate that the interfacial electrochemistry of ferrocene-terminated SAMs can be used to detect the micellization of anionic surfactants in aqueous solution.

Odd-even effects are recently wildly observed in alternative materials properties, such as boiling points, exchange kinetics, electron transfer and chirality. In self-assembled monolayers (SAMs) of functionalized alkanethiolates on metal surfaces, an odd versus even number of methylene units impacts the molecular geometry and orientation of the terminal active groups. Due to the attractive electrochemical properties of ferrocene (facile electron transfer, low oxidation potential, and two stable redox states), ferrocenylalkanethiolates on gold, Fc(CH₂)_nSAu, are the most investigated electroactive SAM system. These SAMs undergo coupled electron transfer and ion pairing reactions. Steric constraints for charge neutralization by the complexing anion, X^-, in the densely-packed Fc(CH₂)_nSAu SAM induce a molecular reorientation and volume change. Are these redox-induced changes in the SAMs structure affected by an odd versus even number of methylene units? We report here the results of electrochemical surface plasmon resonance  aimed at detecting the effect on the ion pairing reaction of the different orientation of the ferrocene units in odd and even carbon n Fc(CH₂)_nSAu SAMs.

Functionalizing metal surfaces using a self-assembled monolayer (SAM) is key to many technological applications, including the design of nano-patterned materials in the semiconductor industry, chemical sensing and oxidative protection. Here, we describe our recent advances in applying N-heterocyclic carbenes (NHCs) as self-assembled monolayers on planar surfaces of Au and Cu, and as direct protecting ligands on a series of bimetallic nanoparticles, including Au-Ag, Au-Pd and Au-Cu. Recent findings in our labs have demonstrated that the development of bicarbonate salt-based NHCs affords their use in a bench-top setting. These bicarbonate salt NHCs have demonstrated efficient deposition from solution onto planar bulk surfaces, and may be used in the direct synthesis of bimetallic nanoparticles from precursor salts using a "bottom-up" process.  We show that NHC SAMs afford significant protection to both surfaces and nanoparticles from oxidative processes, and form a stable platform on which to carry out further surface chemistry and chemical sensing, including surface plasmon resonance. The nature of the NHC-metal bond is further explored through the application of both X-ray absorption fine structure to a series of nanoclusters primarily composed of surface Au atoms, and from a series of photoemission experiments carried out at low X-ray excitation energies.

Development of rapid approaches that are capable of in-situ and real-time monitoring of analytes in complex matrices could in principle, impact many applications including medical diagnostics, prognostics and therapeutics. Over the past two decades, many approaches for detection of biomarkers have been explored among which, electrochemical sensors have shown a lot of promises since they are known to be rapid, reagentless and easily multiplexed. However, given the fact that signal originates from the electron transfer, further steps need to be taken toward a specific and sensitive signal response aiming for a point-of-care platform. By engineering the sensor’s surface, we demonstrate modifications such as: (1) immobilization of selecting/capturing monolayers (DNAs and proteins) on the interface of the sensing electrode to provide the desired specificity in real biological samples, e.g. whole blood, and (2) introducing of surface nanoroughness and microscale electrodes to the sensor platform to provide direct analysis of clinical samples with appropriate target detection limits, and low levels of false negatives and false positives. Our sensor platforms using steric effects combined with bioconjugation-based capturing mechanism on nanostructured microelectrodes provide multiplexing detection of antibodies, proteins and small molecules at their therapeutic range for application in disease diagnostics, and therapeutic on-line monitoring.

Permanent doping of semiconductors and low-dimensional structures to modulate their electronic properties is a well-established concept. Even in cases where doping of thin films by analytes (e.g. carbon nanotubes by ammonia) is applied in sensors, it is only reversed by physical removal of dopant molecules, e.g. heating. We demonstrate the facile doping and de-doping of carbon nanotube networks in contact with different oligoaniline oxidation states as an example of interfacial doping with a switchable dopant, i.e. a molecular switch. The idea that a small local change in carrier concentration results in a large change in resistivity is reminiscent of (but not identical to) a chemical field effect transistor (where the electric field is modulated due to creation of electric charges). While for most conventional sensing applications, the removal of the dopants from the film presents one challenge and the selectivity to a particular dopant another, even bigger, challenge, our devices keep the dopants in place. The sensing performance is achieved by switching the dopants between active and inactive states. A redox sensor for measuring chlorine concentrations in drinking water is the first member of this new class of sensors, although the concept can be applied to many other systems.

Stretchable electronic devices built on elastomers have generated exciting new technologies such as stretchable light-emitting devices, wearable health monitors, and implantable biosensors. These studies have relied heavily on a single material – polydimethylsiloxane (PDMS) – as the elastomeric substrate. An important advantage of PDMS is that its surface chemistry can be easily modified through plasma and chemical treatment, which enables integration with thin films of device materials. However, this advantage is outweighed by its high gas permeability, which is detrimental to stretchable devices that use materials sensitive to oxygen and water vapor, such as organic semiconductors and oxidizable metals. Recently, we introduced transparent butyl rubber, a new elastomer that has the potential to revolutionize stretchable electronics due to its intrinsically low gas permeability. This beneficial bulk property, however, is accompanied by challenging surface chemistry: Butyl rubber is a hydrophobic elastomer that decomposes with plasma treatment, making it difficult to integrate with electronic materials. In this presentation, we present the fabrication of a new layered elastomeric composite comprising a PDMS membrane chemically bonded to the surface of a butyl rubber substrate. This new layered composite combines the best of both worlds: The simple surface modification of the PDMS membrane enables the deposition of electronic materials necessary for stretchable device fabrication, while the excellent gas-barrier properties of the butyl rubber substrate protect these sensitive materials from environmental degradation, providing a route to stretchable devices with practical lifetimes.

I will give a general update of our recent photoemission endstations at Canadian Light Source Inc., present some recent work in VUV photoemission (UPS) and hard x-ray photoemission (HXPS) in 2016. These involve UPS work on Li and Na battery system; quantum dot photo-detectors; combined UPS and HXPS studies of layered material and other correlated work. I will also discuss our future photoemission plan and other activities.

The transformation of biomass into useful chemical compounds with applications in a large range of industries represents the future of a clean and sustainable world. Lignin is indeed nature’s most abundant aromatic polymer (10–30% of biomass) and therefore represents an extraordinary sustainable source of highly valuable aromatic compounds.  

The adsorption and decomposition of Anisole and 2-Phenoxyethanol on clean Pt(111) was studied as a function of temperature and exposure by means of  X-ray photoelectron spectroscopy (XPS),Temperature programmed desorption (TPD) and DFT calculations (optPBE functional).

Under UHV conditions, anisole gives benzene, CO and H₂ as the main desorbing products of the decomposition. Phenoxy is the key intermediate of the decomposition of anisole. Interestingly enough, phenol has not been observed, while it is one of the main products under catalytic conditions (1-100 bars H₂). It seems that UHV condition do not allow the hydrogenation of phenoxy into phenol and the presence of carbonaceous species actually performs the deoxygenation of phenoxy into benzene.  

The reactivity of 2-Phenoxyethanol on Pt(111) eventually falls back to the reaction network of the anisole decomposition.

This study opens the road to a better design of metallic based catalysts aiming at lignin deoxygenation.

Here we report on the design of new materials based on semiconducting nanoparticles (ITO-NPs) that were screen printed on conductive transparent ITO- and FTO- covered glass plates. Functionalization of these high surface area substrates with terpyridyl-moiety followed by the formation of the corresponding Fe(II) and Ru(III) metal complexes leads to the formation of intensively colored materials. Since optical properties of electrochromic materials depend in a continual but reversible manner on the applied voltage, the materials were characterized using cyclic voltammetry. Indeed, the change of the metal oxidation state results in the drastic colour change of the material. The materials demonstrate long-term redox and photochemical stability, high contrast ratios, and high color homogeneity.

Stimuli-responsive coatings enable surface property changes by modulating their structure, surface chemistry or both. However, most coatings suffer from major shortcomings such as lack of responsiveness, selectivity and poor environmental stability. The present work aims to overcome these limitations by the development and optimization of a new generation of responsive hierarchical coatings whose physical properties and surface chemistry can be tuned independently and reversibly using different external stimuli. The hierarchical coatings consist of two-dimensional functionalized-microgel arrays whose characteristic dimensions and surface properties can be independently controlled using different stimuli.  The results showed that it is in fact possible to obtain independent physical and chemical responses by functionalizing thermo-responsive microgels with pH-responsive polymer brushes. These systems are very promising as functional elements in nanotechnologies such as microfluidics.

Dip-coating from solution, in contrast to spin-coating, has been little used in the preparation of thin block copolymer (BCP) films and patterned templates. It will be demonstrated, mainly using polystyrene-poly(4-vinylpyridine) (PS-P4VP) BCPs, that it is a powerful technique for obtaining a diversity of controlled thin film morphologies and patterns, even when using a single block copolymer composition, particularly when combined with H-bonding supramolecular block-selective small molecule components. An underlying feature is the V-shaped dependence of the film thickness on dip-coating rate, which defines the so-called capillarity and draining regimes of dip-coating. The film morphology is determined by the interplay between dip-coating rate, small molecule uptake in the film, block selectivity of the solvent, solution micellar properties, film thickness, and effect of solvent on H-bonding between the functionalized small molecule and P4VP. Furthermore, dip-coating is amenable to simultaneous external control, which will be shown using light control with a photoresponsive H-bonding small molecule. An application of BCP dip-coating for Au nanoparticle templating on glass nanopipettes in view of nanobiosensors will also be presented. In this case, the small diameter of the pulled pipettes appears to result in an unpatterned ultrathin BCP layer, probably adsorbed onto the pipette in solution; nevertheless, when used as a template, it is effective in adsorbing the Au nanoparticles with little aggregation compared to bare glass or to P4VP homopolymer-coated nanopipettes.

Cellulose nanocrystals (CNC) are bio-derived, natively hydrophilic nanomaterials. While they disperse well in water, it is challenging to suspend them in non-polar, hydrophobic media, required for their use in most polymers. In this work, the hydrophilic surface of CNC was modified using polyethyleneimine (PEI), through a low cost and eco-friendly process. The successful modification was confirmed through XPS and FTIR. UV-Vis spectroscopy was performed to study the precipitation rate of the dried-modified CNC (mCNC) in water and the stability of the modifier. After the modification process CNC agglomerates were formed in aqueous suspensions, confirming the hydrophobic nature of mCNC. The solid structure of agglomerates reduced particles diffusion and led to the formation of a gel structure. The mCNC could readily be dispersed in toluene, while they precipitated in fresh water (indicating their hydrophobic surface). Modification was achieved by using only a small amount of PEI (1wt.% respect to CNC), showing that PEI has a strong potential to alter CNC. FTIR results indicated, the modification did not change the CNC structure, and this was confirmed by XPS. UV-Vis showed, the hydrophobicity of mCNC did not change after being in contact with mineral oil and water, resulting in a stable hydrophobic surface.

Self-assembled and cross-linked chitosan/cellulose glutaraldehyde composite materials (CGC1, CGC2 and CGC3 were the numbers represent glutaraldehyde feed ratio) were prepared and characterized via FTIR, CHN, ¹³C solid state NMR studies, XRD, SEM, and TGA. The surface area determination by nitrogen adsorption and equilibrium swelling indicate cellulose-chitosan composites have stable interactions and variable morphology. Equilibrium sorption studies at alkaline conditions with phenolic dyes, single component and mixed naphthenates in aqueous solution reveal materials with enhanced surface area and variable affinity with these anion species. The Sips isotherm model was the best fit for sorption of single component and OSPW naphthenates. Uptake of 2-hexyldecanoic acid was the most favored (Q_m = 115 mg g^-1) relative to other anions while the sorption capacity of CGC3 for naphthenate mixtures was 24.1 mg/g via UV-vis spectroscopy and 27.4 mg g^-1 via electrospray ionization mass spectroscopy. The composite material has greater affinity for naphthenates with low double bond equivalence. Kinetic studies revealed that the sorption of phenolphthalein followed the pseudo-second order model whereas the uptake of 2-naphthoxyacetic acid and naphthenate mixtures obeyed the pseudo-first order (PFO) model. This study reveals that the self-assembly of cellulose and chitosan enhance the anion recognition capacity of the composite material.

Articular joints have captivated the scientific interest of many research groups due to their excellent lubricating and wear resistance properties. Many different mechanisms have been proposed to explain the exceptional lubrication properties of cartilage. Molecular mechanisms have pointed lubricin as a key protein controlling the lubrication of cartilage. The mucin domain of lubricin has the peculiarity of having a bottle-brush architecture with glycosilated side chains grafted on the main chains of the protein. Until recently, the origin of the unmatched lubricating properties of this protein was unclear. In this presentation we will show our recent intents to develop structured polymers whose architecture incorporate lubricin key features. These polymers used alone or mixed with linear polymers such as hyaluronic acid  allow to achieve super lubrication and high wear resistance in a large variety of water-based lubricating  systems. Certain immediate applications of these systems in the biomedical field will be discussed.

Platinum thin films cover supports like yttria stabilized zirconia, titanium dioxide and graphite as a precursor to create catalysts and electrodes with micro- and nanostructures that improve their reactivity. Due to the difference of free energy per area between a thin film and agglomerated particles, Pt migrates when annealed above 400^◦C, thus forming three-phase boundaries. Kinetic studies based on temperature demonstrated that holes form first. As the holes grow larger, bridges form between Pt domains and finally break leaving isolated islets. Here we report how Pt thin films (15 nm to 30 nm-thick) morphology evolves as a function of both temperature (550^◦C to 1000^◦C) and time (up to 16 h). Starting from a 30 nm-thick film, the support uncovered area and islet diameter reach respectively a maximum and a minimum at 12 h when annealed at 700^◦C. We show that beyond this time islets are coarsening, the platinum reforms bridges, the uncovered area and the particle height decrease. The transition time is only 4 h for 15 nm and 700^◦C and it is less than 8 h for 30 nm and 1000^◦C. 

Ice clouds are known to play a major role in the global radiation budget (IPCC, 2014) by diffusing incoming and outgoing radiation fluxes (Schuman, 2012) and by catalyzing a broad array of chemical reactions. Heterogeneous chemicals reaction mechanisms have been largely studied in the laboratory using thin ice films and spectroscopic methods aiming at understanding differences in the reactivity of surface and bulk ice (Marcotte et al., 2015). Though, as the ice growth mechanisms are poorly understood, and depend very strongly on the growth conditions, spectroscopic data often remain difficult to interpret. This is mostly due to differences in ice morphology, impurities concentration and distribution (Barnes et al., 2003), as well as differences in reaction sites, important properties that display extreme sensitivity on the details of the ice film preparation protocols.

Cryogenic environmental scanning electron microscopy (Cryo-eSEM) offers the opportunity to explore the dependence of ice films morphology on thickness, substrate properties, growth temperature and water supersaturation. Water vapor deposition, under controlled supersaturation ratio and temperature, on hydrophobic and hydrophilic substrates, has been used to study ice films growth under environmental conditions.

Iron oxide nanoparticles (IONPs) are composed of an inorganic iron oxide (typically Fe₃O₄) core protected by surface capping ligands, and, due to their unique combination of magnetic properties, low biological toxicity and low cost, have been recognized as ideal components for many advanced technologies. For this purpose, catechols are amongst the most widely employed capping groups for IONPs, owing to their high-affinity for Fe³⁺ on the nanoparticle surface. As a result, many investigations have been performed regarding the stabilization of IONPs with designer ligands based on surface binding through catecholate groups. However, very few examples of systematic research regarding the relationship between ligand structure and subsequent binding to iron oxide exist. This apparent disconnect has severely hindered the design of new ligands for the stabilization and functionalization of iron oxide nanoparticles. Here, we characterize the surface modification of ultrasmall IONPs with the model ligands dopamine, salicylic acid, and a set of related dihydroxybenzoic acids, and demonstrate how knowledge of IONP surface chemistry enables further funtionalization. The structure-activity relationships observed between the model ligands investigated and iron oxide will aid in both future ligand design and chemical functionalization of IONPs.

Solution processable nanocarbon materials, in particular single wall carbon nanotubes (SWCNTs) and graphene flakes dispersed in solution, are of interest for a wide range of applications including printable electronics and light weight composite materials. Atomic force (AFM) and scanning tunneling (STM) microscopies have been used to probe both the structure of individual tubes/flakes as well as the morphology of networks/films assembled from these building blocks. AFM imaging of networks of polymer wrapped semiconducting SWCNT networks reveals how network morphology is strongly modified by varying deposition conditions. In general the tubes are significantly bundled and an analysis method has been developed to quantify this bundling and facilitate correlation with electronic transport. Careful AFM height measurements on single tubes allow the thickness of the polymer on the SWCNTs to be measured. STM imaging confirms significant bundling and provides information on tube-tube junctions which limit transport in these networks. AFM imaging of flakes of graphene oxide (GO) allows determination of flake size and thickness. Height measurements can be used to follow the thermal reduction of GO to graphene. STM images provide information on the nature of defects present in reduced graphene oxide.

We investigated the impact of surface functionalized silica nanoparticles on the structural properties of biomimetic pulmonary surfactant films. Understanding the reactivity of nanomaterials with pulmonary surfactant at the molecular level is important to the development of design parameters for environmentally benign chemical nanomaterials and the prevention of respiratory problems caused by airborne nanomaterials. Lung surfactant replacement therapeutics, Infasurf, and lipid-only systems containing saturated and saturated phospholipids were spread on an aqueous solution of the nanoparticles and were studied by grazing incident X-ray diffraction and X-ray reflectivity techniques. The results showed that the films on pure water subphase, and exposed to neutral, and negatively charged nanoparticles, have an oblique lattice with an intermediate tilt azimuth. However, the films exposed to cationic nanoparticles, showed a centered rectangular unit cell. This system has the smallest value of tilt angle, and the smallest value of out plane scattering length, suggesting the monolayer is pulled downwards at the interface upon interaction with the cationic nanoparticles. The results highlight that the surface chemistry of nanoparticles imposes different structural arrangements in pulmonary surfactants. Furthermore, these results are in agreement with the morphological changes and viscoelastic properties obtained by surface-area isotherms, Brewster angle microscopy, and profile analysis tensiometer.

We have studied novel “PEG-like” plasma-deposited coatings of poly(ethylene glycol), which prevent protein adsorption and cellular adhesion. This enables inhibition of possible inflammatory reactions or rejection of an implant following its insertion into living tissue. Our innovative approach enables precise measurements of electrical energy, E_g, per a.c. voltage discharge cycle in atmospheric-pressure (AP) dielectric barrier discharge plasmas, DBD. The method can be applied to plasma-polymerization (PP) with Argon as carrier gas: comparing DBD with and without (a few ‰) addition of a “monomer”, a ΔE_g value can be determined that depends strongly upon monomer flow rate, F_d. Dividing ΔE_g  by the number of molecules traversing the plasma per unit time yields E_m, the energy absorbed per monomer molecule (in eV). Here, we demonstrate the key importance of E_m in preparing PEG-like coatings for biomedical applications, for example by highlighting the great sensitivity towards molecular weight of mono-glyme (1G) or di-glyme (2G) monomers, and by obtaining anti-(bio)fouling layers, “PP-2G”, only with the di-glyme: We clearly demonstrate near-total absence of adsorbed proteins and cells on PP-2G surfaces prepared with optimized F_d (and E_m) values.

Gold nanoparticles (Au NPs) are widely employed as tunable core in materials science, molecular transport, catalysis, and energy conversion. Incorporation of functional thiols into citrate-stabilized AuNPs  is a promising strategy for well-tuning of interfacial properties of NPs.

Use of high molecular weight molecules of biological origin for controlled NPs assembly is a challenging task for nanobiotechnology. Among others, hemoglobin (Hb) was reported to adsorb on metal oxide surfaces and on Au NPs.  However, the binding process was associated with mainly hydrophobic forces and hydrogen bonding; neither direct interaction between Au NPs and hem groups was reported, no interactions between Au NPs and Hb thiol groups were considered. Taking into account that Hb has definite tertiary structure and contains four globin chains each associated with one molecule of iron heme, in our work we utilized heme moieties for creation of controlled and well directed NPs assemblies. We employed high binding affinities of Hb for heteroaromatic amines as a driving force for controlled assembly of gold nanoparticles.  Here we report on functionalization of citrate-stabilized Au NPs with a novel heteroaromatic amine receptor anchored to the NP via dithiolate linkage and able to cross-link NPs in presence of iron ions or hemoglobin.

The silica/aqueous interface is one of the most widespread interfaces from both an environmental standpoint as well as in commercial applications as sand is a large component of the earth’s crust and glass is a very common industrial material. Despite its ubiquity, the influence of common ions on surface charging at this interface as well as ion effects on the interfacial structure of water are still not well understood as many spectroscopic methods are not amenable to probing insulator/aqueous interfaces. However, owing to their intrinsic surface selectivity and ability to monitor buried insulator interfaces, second-order nonlinear optical techniques like second harmonic generation (SHG) and sum frequency generation (SFG) are very well suited to study silica in the presence of the aqueous phase. Using a combination of SHG and vibrational SFG, we have explored the influence of monovalent and divalent salts on the pH-dependence of surface charging on silica and the interfacial water structure, respectively. Our work reveals that the presence of high concentrations of monovalent salts like Li⁺, Na⁺ and Cs⁺ leads to structured water at the interface, even near the point of zero charge of silica (~pH 2). We attribute this structured water to the formation of the electric double layer, which leads to ordered water in the diffuse part of the double layer. In contrast, we observe that divalent ions promote the destruction of this ordered water layer, especially at high pH. As an important environmental problem facing Alberta involves the slow settling and solidification of the tailings waste from the Athabascan oil sands, our ability to probe interfacial water holds promise for rapid screening of dewatering agents that are used to promote densification of the oil sands processing waste.

Gold nanoparticles have been shown to exhibit preferential mixing with n-alkanes when two conditions are met: 1) the temperature is below the order-disorder phase transition temperature of the nanoparticle ligand coating; and 2) the n-alkane chain length is longer than that of the thiol. Pressure vs. area isotherms of these mixtures as Langmuir films exhibit the onset of a novel liquid-like phase when these conditions are met, versus the typical solid-like phase behaviour for nanoparticle films. Xray reflectivity and grazing incidence Xray diffraction were used to provide insight into the role of the n-alkane during film assembly and compression. Generally, diffraction results reveal a marked improvement to the nanoparticle ordering while reflectivity shows differences in the amount of n-alkane residing at the air-water interface coplanar to the nanoparticle film. These detailed results of this study will be presented and implications on nanoparticle mixing will be discussed.

Carbon dots (CDs) have gained significant interest as fluorescent nanomaterials with potential applications in biomedicine, including sensing, imaging, optoelectronics and energy conversion. Ease, cost-efficiency and environmentally-friendly synthesis, combined with their nano-scale size, biocompatibility, low photo-bleaching/blinking and tunable photoluminescence, renders them ideal candidates for study. Presently, a definitive mechanism responsible for their photoluminescent properties has yet to be proposed. In this work, we probe the effects of CD particle size and surface chemistry, on their optical properties. CDs are synthesized via a bottom-up microwave method, using citric acid as the carbon source. They are systematically nitrogen-doped with a series of polyamines, which act as passivating agents and treated with a variety of oxidizing and reducing agents, in an attempt to modify their surface chemistry. We examine the physical and photoluminescent properties of the synthesized CDs, with emphasis on particle size, fluorescence emission spectra, fluorescence quantum yields and surface composition.

Nanoparticles may aid enhanced oil recovery (EOR) because they may alter rock wettability and possibly reduce the interfacial tension (IFT). The effect of nanoparticles on the oil-water IFT is controversial with some showing that nanoparticles reduce IFT and others illustrating that they have no significant effect. The discrepancy may arise from the way nanoparticles form at the interface.

Nanoparticles must first adsorb at the oil-water interface then form and sustain a monolayer at the interface to reduce IFT. There must be sufficient nanoparticles and an effective driving force for the nanoparticles to adsorb at the oil-water interface. In this research, the kinetics of nanoparticle adsorption at the oil-water interface and the conditions under which untreated nanoparticles can reduce oil-water IFT are investigated. Results show that the maximum IFT reduction occurs when a complete monolayer of silica nanoparticles forms at the interface. At low nanoparticle concentrations, there are insufficient nanoparticles to form and keep a complete monolayer at the interface. If the nanoparticle concentration is too high, the hydrodynamic radius increases and the IFT may increase. Moreover, the effect of pressure and temperature on IFT from ambient to reservoir conditions is investigated.

Cross-linked/quaternized (CQC) and quaternized (QC) cellulose hydrogels were prepared by cross-linking native cellulose with epichlorohydrin (ECH), with subsequent grafting of glycidyl trimethyl ammonium chloride (GTMAC). Characterization via CHN analysis, TGA, and FTIR/ ¹³C solids NMR spectroscopy provided support for the structural characterization of the hydrogel materials. Greater thermal stability of the hydrogels was observed relative to native cellulose, while unique colloidal stability of the hydrogels was evidenced by the stabilization of a hexane-water Pickering emulsion system. Equilibrium sorption studies with naphthenates from oil sands process water (OSPW) and 2-naphthoxy acetic acid (NAA) in aqueous solution revealed that CQC possess higher affinity for the naphthenates relative to QC. Kinetic uptake of NAA at variable temperature, pH and adsorbent dosage showed that increased temperature favored the uptake process. Solution conditions at pH 3 or 9 had a minor effect on the sorption process, while equilibrium was achieved more rapidly at lower dosage (ca. three-fold lower) of the hydrogel (100 mg vs. 30 mg). The estimated activation parameters based on temperature dependent rate constants, k₁, revealed contributions from enthalpy-driven electrostatic interactions. This study contributes to a greater understanding of the adsorption and physicochemical properties of surface modified cellulose-based hydrogels.

Ice accretion on power generation infrastructure is a costly and dangerous problem. Icephobic materials are being developed that can prevent ice growth if the adhesion strength is below 20 kPa. Slippery lubricant infused porous surfaces (SLIPS) have been shown to possess impressive ice repellent properties, but lack the durability required to prevent ice adhesion over long periods of time. This research seeks to improve the durability of SLIPS to make them suitable for anti-icing applications. A method for the preparation of new SLIPS with higher durability will be shown. Surface characterization and ice adhesion testing results, perspective, and future work will be discussed.

The properties of the nuclear spin isomers (NSI) of the water molecule are of great interest in astrophysics since the ortho:para ratio (OPR) is assumed to provide insight into the history of comets [1] as well as other celestial bodies [2]. Applications in NMR are also foreseen for ortho-H₂O enriched samples. We will show how magnetic focussing in a molecular beam [3] provides a convenient method for preparing water vapour strongly enriched in ortho-H₂O. We will also show that rare gas matrices can be an efficient storage medium for enriched samples [4] whose lifetime remains however, limited by the interconversion kinetics of NSI. Closer examination of the NSI inter-conversion kinetics of H₂O@Ar, revealed that it increases significantly in H₂¹⁷O and H₂¹⁸O compared to normal water, and that it increases rapidly above T~10K.[5] The temperature and isotope effects may provide valuable insight into the role of confinement and of intramolecular hyperfine couplings responsible for interconversion. 

[1] Mumma, et al., Science 232, 1523 (1986); [2] Hogerheijde, et al., Science 334, 338 (2011);[3] Kravchuk et al., Science 331, 319 (2011); [4] Turgeon et al., Phys.Rev.A 86, 062710 (2012); [5] Turgeon, et al, 121, 1571 J. Phys. Chem. A (2017).

Among the various transition metals, iron is the most abundant essential trace element in the human body.  Thus, iron deficiency may lead to anemia, organ dysfunction, and tumorigenesis. Paradoxically, too much iron is equally hazardous to health due to its ability to participate in redox reactions and generate free radicals that increase risk of cancer, Parkinson’s and Alzheimer’s diseases.

Herein we report water soluble terpyridine-based receptor that demonstrates effective quantification of ppb to ppm levels of Fe²⁺ in solution and when embedded on porous TiO₂ nanoparticles. Moreover, the phosphoric moiety of the receptor was employed to immobilize sensing molecule on variety of flat and porous surfaces and screen-printed films to prepare reusable sensing strips with high sensitivity to iron ions in the solution. Rapid (<30 s) colour change of the developed materials from white to magenta permits easy detection of as low as 0.3 ppm of Fe²⁺ by the naked eye. Colour change intensity depends on the nature of the support, the overall film thickness, and the Fe²⁺ concentration. The material shows colour reversibility upon treatment with EDTA solutions, which allows for multiple reuses of the same film with no effect on sensitivity.

The present work reports the fabrication and characterization of a ferroelectric tunnel junction device (FTJ). It is an emerging memory that could replace the current dynamic random access (DRAM) memory, which has gradually reached its physical scalability limits.

In the last couple of years, it had been reported the successful fabrication of FTJ devices based on different perovskite tunnel barriers, where it was demonstrated promising properties such as good scalability, low operating energy, high operation speed, high endurance, non-volatility and a simple structure. However, FTJ’s based on perovskite tunnel barrier require of specific substrates and high processing temperatures which makes them incompatible with the complementary metal oxide semiconductor process (CMOS).

The originality of the present work relies on the demonstration of the tunneling electroresistance effect in a FTJ memory device based on a CMOS compatible tunnel barrier Hf_0.5Zr_0.5O₂ (6 unit cells thick) on an equally CMOS compatible TiN electrode.

Hydration phenomena at solid-solution interfaces play a key role in physical and biophysical processes in aqueous solutions. Based on the previous studies, solvent selective adsorption processes in mixed solvent systems are poorly understood. We report on solid phase polysaccharide adsorbent materials for the fractionation of water from ethanol in binary solutions. To gain an improved understanding of the role of solvation effects and interfacial phenomena in mixed solvent (water-ethanol; W-E) systems, several types of polysaccharide sorbents (starches with different percentages of amylose and amylopectin and cellulose) were studied by complementary analytical methods. Swelling of the polysaccharides was measured to ascertain the hydration and selective solvent uptake properties in binary W-E mixtures. The hydration properties of the sorbents were further probed using thermoanalytical and spectroscopic techniques. The surface accessibility of the hydroxyl (-OH) groups of the biopolymers was estimated using a dye decolorization method. This complementary study contributes to a greater understanding of the role of structure and functional group accessibility governing biopolymer-solvent interactions, hydration properties of biopolymers and the molecular level process of fractionation in W-E mixtures. 

The use of alcohol in the biofuel industry is very important and it requires new materials and methods to remove water from biofuel mixtures to improve quality. Miscanthus is a rich source of lignocellulosic biomass with a great potential for applications ranging from biofuel production to value-added biomass derived products. In this research, the utility of Miscanthus and its modified forms were used for the fractionation of water (W) and ethanol (E) mixtures using an in situ analytical method, referred to as quantitative NMR (qNMR) spectroscopy. Therefore, raw and pretreated Miscanthus with variable biopolymer content (cellulose and lignins) and variable particle size were evaluated as sorbents in binary water-ethanol (W-E) mixtures. The pretreated Miscanthus was prepared by an acid and then an alkaline hydrolysis for the removal of hemicellulose and lignin, respectively, leading to the enrichment of cellulose. As a result, the raw and pretreated Miscanthus were characterized using Fourier Transform Spectroscopy (FT-IR) and displayed preferential water uptake properties related to different content of biopolymers such as cellulose. In addition, the fractionation properties of Miscanthus and its biopolymer constituents display molecular selectivity (R_selectivity) between water and ethanol. To test reusability, Miscanthus was shown to be regenerated over four adsorption-desorption cycles.

We report the design of electrochromic materials constructed from a single layer of metal-terpyridine complexes on conductive indium-tin oxide (ITO) supports. Substitution of 2,2':6',2''-terpyridine at the 4’ position with N aromatic substituents generates ligands that form intensely coloured complexes when coordinated to Fe²⁺ or Co²⁺. The coordinated metal complexes become quaternized at the terminal N atom when brought into contact with a chlorobenzyl-terminated silane template layer on flat or porous hydrophilic solid supports.

The film’s colour is impacted by the selected substituent on the chromophore, and substituent investigations include 3-pyridine, 4-pyridine, 4-quinoline, and N,N-dimethylaniline. The MLCT bands are observable in UV-vis spectroscopy for the complexes in solution and on solid glass supports. The film colour is dependent on the metal’s oxidation state therefore changes in redox states for the complex on porous ITO screen-printed films are visible through diffuse reflectance spectroscopy, and the naked eye.

Switching times, colour-efficiency and long term electrochemical and thermal stability were studied and optimized for materials under investigation.

The development of organic analogues of graphene, the only known 2-d conjugated polymer, would represent a new class of materials. One approach to covalent organic frameworks (COF’s) is the adsorption of halogenated aromatic precursors onto atomically ordered surfaces, followed by de-halogenation, and subsequent covalent coupling. Although examples of COF formation on metal surfaces have been described, limited work has been done on semiconducting surfaces. We discuss the adsorption of a halogenated organic molecule, 2,4,6-tris(4-iodophenyl)-1,3,5-triazine (TIPT), onto the Si(111)-√3×√3-Ag surface as studied by STM. We find at low coverage TIPT monomers display high mobility on the √3-Ag surface. Many STM images show evidence of diffusing species on the surface. In fact, this evidence is often manifest as parallel “fuzzy” lines on the √3-Ag terraces. With increasing molecular dose, the monomers form supramolecular domains defined by a 2.0 nm by 1.8 nm rectangular cell. The size and symmetry of the cell provides strong evidence that the monomers do not undergo de-halogenation, and that the dominant interaction within the domains is intermolecular I···H hydrogen-bonding. As the coverage approaches one monolayer, the film is a mixture of supramolecular domains separated by disordered regions.  We will also discuss our preliminary annealing experiments.

The sensitivity of nanostructure array sensors highly depends on the periodicity of the array and the order of the excited surface plasmon polariton modes. In this presentation, we discuss the plasmonic modes of nanodisk arrays (1200 nm periodicity, a disk diameter of 720 nm, disk height of 75 nm and 75 nm film) excited in the enhanced optical transmission configuration. We also studied the sensitivity to bulk refractive index and penetration depth of different modes in different incident angles. The decay length of the electromagnetic field was estimated using a layer-by-layer deposition technique of polyelectrolytes (PAH and PSS) and was confirmed with 3D FDTD simulations. Then we compared the surface sensitivity of the nanodisk arrays of the mode (1.0) in different angles to maximizing improve detection limits for IgG sensing.

  Public attention to the water contamination raises an urgent need to develop effective and reliable methods to detect the presence of any organic compound in water such as, atrazine. The current detection techniques for instance, liquid chromatography, mass spectroscopy, or colorimetric methods, which usually require sophisticated and time-consuming steps or sample preparation besides a well-trained operator. Herein, surface enhanced Raman is a powerful vibrational spectroscopy technique that allows for highly sensitive structural detection of compounds. Significant signal amplification is observed on roughened surface of metal nanostructure. However, developing a novel nanomaterial as cost effective, sensitive, and reproducible substrate for surface-enhanced Raman spectroscopy (SERS) applications remains a major challenge. Therefore, Gold nanorods (GNR) are a great candidate for SERS substrates, their importance rises from their LSPR excitation by light, which generates a strong signal due to their anisotropic shape. Moreover, their ability to fabricate in to well ordered standing arrays with a maximum gapping distance~0.8nm in order to allow the maximum signal attainment in the rapid detection of organic and inorganic pollutants at very low concentration (0.1ppm). Those compounds can be differentiated based upon fingerprint spectra that arise when they enter SERS active hot spot.

Direct laser micromachining has emerged as a versatile technique for extensive modification of material surface properties that results from the laser material interaction. For industrial usage and therefore, for efficient replication of the desired surface properties, extensive knowledge of the factors affecting laser material interaction is crucial. Here, we demonstrate the effect of the laser repetition rate on machining outcome; one of the various factors crucial for efficient industrial transfer. We report on the micromachining outcome on copper (Cu) and titanium (Ti) using femtosecond pulses (<100fs) at 1 and 10 kHz. The microstructure formation and the variation in the surface texture (coarseness) caused by the differences in the two repetition rates were analyzed and compared using the accumulated fluence model and lacunarity study, respectively. Significant differences in the coarseness of the microstructures and in their threshold fluence were observed in both the metals at the two repetition rates. These differences were successfully attributed to the respective material behaviour at the two repetition rates.   

MicroRNAs(miRNAs) are non-coding small RNA molecules of 19-22 nucleotides with crucial regulation of gene expression. Emerging evidences also show that miRNAs are closely involved in human diseases, including cancers, and hence miRNAs can be applied as sensitive and specific biomarkers for diagnosis.

In this presentation, “Off to On” and “On to Off” signalling strategies are employed to detect miR21 with surface plasmon resonance (SPR). In the “Off to On” strategy, a sandwich detection approach is used, while in ``On to Off`` strategy, a competition detection approach is adopted. The optimization of experimental parameter led to date to a detection limit as low as 1 nM without amplification.

Rolling circle amplification(RCA), which is reported to have up to 10⁵ linear amplification efficiency, will be adopted to improve the sensitivity of our detection strategy. Two padlock probes were synthesized to amplify miRNA, the amplification products are then subject to our SPR detections. Therefore, we will show the different detection strategies using SPR sensing technologies for sensitive miRNA detection.

Phenolic compounds such as tannins exhibit antioxidant, metal chelating and protein-binding abilities; surfactants with this functionality may confer these properties to self-assembled structures and surfaces. We have previously shown the phenolic headgroup to be extremely self-adhesive give strong lateral rigidity to monolayers at liquid surfaces. The extent to which the phase behaviour can be tuned by modifying the intermolecular interactions via changes in subphase composition (such as pH and salt concentration) will be presented for lauryl gallate (C12) and octadecylgallate (C18) surfactants which exhibit liquid expanded and condensed phases, respectively, at the air water interface. The film organizational changes are determined by grazing incidence x-ray diffraction (GIXD) while morphology is assessed using Brewster angle microscopy at the air-water interface and atomic force microscopy for films deposited on mica. The competition of hydrogen-bonding and π-stacking interactions between headgroups can be manipulated to yield highly directional domain growth and control over the inter-surfactant distance. Contrary to what is observed for most surfactant monolayers, GIXD measurements show that the gallate headgroups are arranged in a crystalline packing state with limited free rotation, attributed to strong hydrogen bonding and π-stacking interactions of the gallate headgroup

Human exposure to nanomaterials is inevitable given the increasing presence in the environment of nanoparticulates generated by industrial activities. Colloidal silica is the most abundant air pollutant in industrial regions. Due to their exceptional chemical reactivity, silica nanoparticles (NPs) can potentially inhibit the lung surfactant and cause difficulties in breathing. The present study investigates the biophysical effects of NPs charge and concentration on the phase behaviour of model lipid mixtures and clinical pulmonary surfactant. A surfactant monolayer was formed at the air-water interface over a NPs-containing subphase. The Langmuir film balance was used to examine the lipids surface activity, while Brewster angle microscopy and Atomic Force Microscopy allowed the study of the overall morphological changes to the film, while the structural changes were detected with x-ray diffraction technique. We obtained a clear evidence that silica NPs influence the lipid monolayer at concentrations as low as 0.001%. The revealed biophysical mechanism of NP interaction with pulmonary surfactant brings new insight in understanding how inhaled NPs impact pulmonary function.

Self-assembled monolayers (SAMs) enable the modification of the substrate surface properties for functional purposes. SAMs have been shown as an effective and simple method to control the wettability of both metal and ceramic surfaces, but they must maintain their properties over time in typical operating conditions. This work examines the stability of three SAMs (hydrophobic octadecyltrichlorosilane, and hydrophilic 3-aminopropyltriethoxysilane, and 3 mercaptopropyltrimethoxysilane) for wetting control on silicon, fused silica, pyrex, and copper surfaces under different environments. The effect of ambient temperature, ambient humidity, and cleaning methods on the reliability of SAM-modified wettability is often an overlooked but critical aspect for operational performance in functionalized surfaces. Results showed that the performance of SAM-modified surfaces can be improved based on the environment temperature and applied surface cleaning method. Long-term stability of the wetting properties of SAMs in air and humid environments was demonstrated up to 150°C. Therefore, these findings can elucidate about SAMs wettability limits in different environmental conditions and facilitate the development of higher performance thermal management systems.

Imaging X-ray photoelectron spectroscopy (XPS) has been used to investigate oxide film changes on four Ni-Cr-Mo alloys after exposure to simulated crevice corrosion conditions. The thin Cr- and Mo- rich oxides formed on these alloys provide excellent corrosion resistance in many environments, but can be vulnerable to breakdown under crevice corrosion condition. Four different Ni-Cr-Mo Hastelloy® alloys (BC-1®, C-22®, G-30® and G-35®) with differing Cr and Mo concentrations were examined after exposure to a simulated crevice solution of 1 M HCl + 2 M NaCl at 75 °C for 20 hours. Random grain boundary sites which are potentially susceptible to corrosion were first identified using electron backscatter diffraction (EBSD). Quantitative imaging XPS was then used to correlate the distribution of Cr and Mo with potential breakdown sites in the microstructure. G-30® and G-35® showed extensive corrosion with little correlation to random grain boundaries, while C-22® exhibited some correlation between local breakdown sites and random grain boundaries. BC-1® exhibited a general distribution of Cr and Mo suggesting passivity was maintained. The extent of corrosion damage decreased as the Cr/Mo ratio in the alloy increased. These observations were consistent with electrochemical measurements of corrosion susceptibility.

Femtosecond laser micromachining has emerged recently as a one-step process to modify surface topology on the nano and micrometer scale for use in anti-wetting, anti-icing, microfluidic, electrical and optical applications.  The fs-laser ablation of a UV-cured urethane diacrylate base polymer has been studied alongside the ablation of this base polymer doped with six different additive species. The additives studied include ethyl acrylate, methacrylic acid, styrene, benzyl methacrylate, and ethyl methacrylate. The additive included, and the weight percentage thereof, has indeed influenced the threshold fluence of the material with respect to a 275-nm wavelength fs-laser beam and has altered the incubation effects the material exhibits with subsequent laser pulses. Although these materials have different threshold fluences and incubation coefficients, they all exhibit strikingly similar microstructure when patches are ablated onto their surfaces. This suggests that the base urethane diacrylate polymer dominates with regards to microstructure formation. Further, no relationships are seen between the ethyl, methyl, or benzene chemical groups present in the additives used and the threshold fluence or incubation coefficient exhibited by the material. This suggests that the laser micromachining characteristics of these materials is a result of physical parameters, rather than the chemical bonds present.

Carbon surfaces doped with nitrogen are frequently used in various electrochemical systems, including fuel cell catalysts, supercapacitors, and in sensing applications.  While there are many methods to introduce nitrogen functional groups to the surface, most of these processes lead to a mixture of functional groups.  This makes it difficult to design and study surfaces rich in a single nitrogen moiety for a desired application.  The work presented here demonstrates a novel method for functionalizing carbon surfaces using various terpyridyl-based molecules.  These terpyridyl moieties were attached via a phosphonic, diazonium, or silane linkage to the carbon surfaces.  The modified electrode surfaces were exposed to cyclic voltammetry (CV).  The electrochemical studies performed examined the capacitive and redox behavior of the novel surfaces.  Moreover, a change in electrochemical response was detected when these functionalized surfaces were exposed to a Fe²⁺ solution.  These modified surfaces demonstrate a potential for both ion sensing and a methodical design of a Fe-N/C catalytic active site for the oxygen reduction reaction.

The conducting polymer polyethylenedioxythiophene doped with polystyrene sulfonate (PEDOT:PSS) has become one of the most successful organic conductive materials due to its high air stability, high electrical conductivity and biocompatibility. In recent years, a great deal of attention has been paid to its fundamental physicochemical properties, but its healability has not been explored in depth. In this communication, we report the first observation of mechanical and electrical healability of PEDOT:PSS thin films. Upon reaching a certain thickness (about 1 µm), PEDOT:PSS thin films damaged with a sharp blade can be healed by simply wetting the damaged area with water. The process is rapid, with a response time on the order of 150 ms. Significantly, after being wetted, the films are transformed into autonomic self-healing materials without the need of external stimulation. This work reveals a new property of PEDOT:PSS and enables its immediate use in flexible and biocompatible electronics, such as electronic skin and bio-implanted electronics, placing conducting polymers on the front line for healing applications in electronics.

Photo-deposition method has increasingly become a popular approach to load metal nanoparticles on a surface. As the photogenerated electrons on the conduction band of a photocatalyst are generally reductive enough to reduce the metal ions into metallic nanoparticles, it is facile to disperse nanoparticles on its surface. The mostly applied metals include silver, gold, platinum and palladium etc. The well-dispersed nanoparticles on the surface of a photocatalyst possess following merits: i) improving the visible light harvesting capacity as for the surface plasmonic resonance effect and ii) acting as electrons acceptor so as to improve the separation efficiency of photogenerated charge carriers. Silver and palladium are selected to improve the photocatalytic activity of bismuth-based semiconductors including Bi₂WO₆, Bi₂MoO₆, BiOBr and BiVO₄ in this work. It was found the photocatalytic activity in the degradation of phenol was greatly improved via dispersing these metal nanoparticles on the surface. Also, the mechanism in the enhancement was also explored via different characterizations. This work opens a new possibility for efficient removal of phenolic compounds in wastewater via visible light-driven photocatalysis in the presence of metal nanoparticles dispersed bismuth based semiconductors.

Biomass is a sustainable and renewable feedstock for potentially high value chemicals that, due to its abundance, could theoretically supply the world demand. Lignin, the 2nd most abundant polymer in wood. represents up to 40% of the dry biomass weight in the world. Mainly obtained as a by-product in pulp and paper industries in the form of black liquor, lignin is just burned to produce low-grade fuel. In this research, some fundamental questions regarding conversion of lignin into valuable compounds are addressed. The reactivity of aromatic molecules on different surfaces such as Nickel, Platinum, Molybdenum is coverage dependent. It seems that the adsorption geometry of these molecules plays a key role in their reactivity. In this project, the behavior of 2-phenoxyethanol (2-PE) on various surfaces namely graphite, mica and cobalt is studied through Atomic Force Microscopy. 2-PE is the model used as it contains the characteristic β-O-4 linkage as found in lignin. The patterns formed by the adsorption of 2-PE on these different surfaces were studied as a function of the concentration and dosage. This study is part of a bigger study to enable the sourcing of an array of chemicals from lignin in a more economical, environmentally safe way. 

Thrombus formation on blood-contacting medical devices such as catheters is a significant problem in medicine. The coagulation cascade is initiated by non-specific proteins adhering to the surface of the medical devices and ultimately leading to platelet adhesion and thrombin generation. Lubricant-infused slippery surfaces are a newly developed coating that have proven to minimize medical device induced thrombosis. In this work, we report a more efficient process for creating omniphobic lubricant-infused coatings on commercially available catheters that have anti-thrombogenic properties, using chemical vapour deposition (CVD) of hydrophobic organosilanes. CVD coated catheters significantly increase the clotting time and reduce protein adhesion compared to commercially available catheters. We also compare CVD treated catheters with catheters modified using the liquid phase deposition (LPD) of organosilanes. Although LPD of organosilanes is the most widely used technique for developing omniphobic slippery surfaces, our results showed that LPD was not as efficient, compatible and reproducible compared to CVD. Catheters treated with LPD harmed the polymeric surface of the catheters and their antithrombotic activity was similar to non-modified control catheters. The proposed coating process is simple and efficient and can potentially be applied to other medical devices in order to make them hemocompatible.

Microbial pathogens can grow in food after processing mechanisms. Packaged food can be directly in touch with the surface of their containers or covers. Biosensors developed based on liquid-phase sensors or lab-on-a-chip devices can hardly be used in applications for real-time food examinations after packaging without taking the sample out of the stock. Therefore, real-time and surface based sensing mechanisms are much needed to examine food safety. Simple biosensors, installed inside the food packaging, tracing the presence of pathogens inside the packaged food are needed.

Our team in McMaster university, has developed sensing surfaces based on DNAzyme biosensors, generating a detectable fluorescent signal in the presence of a specific bacteria in food or water. To generate a sensing layer located between the packaging and food, we chose covalent attachment of Amine terminated fluorogenic DNAzyme probes to epoxy coated surfaces. Transparent, flexible and thin COP (cyclo olefin copolymer) slides, were used for this purpose. The developed flexible biosensors can be applied to food wraps or bottles. These DNAzymes cleave in the presence of pathogenic bacteria and release a fluorescent signal. We have so far demonstrated successful detection of Escherichia coli in meat, milk and apple juice using the developed flexible biosensors.

The goal of my presentation is to study the odd-even effect of the carbon numbers in the alkyl chains of the SAM on the microcantilever’s redox deflection.

After functionalizing the microcantilever’s surface with the appropriate SAM, it is used it as working electrode in an electrochemical cell, adapted to the experiment. The electrolytic solution is sodium perchlorate. The deflection measurement device is composed of a laser that sends a beam on the microcantilever’s tip and a PSD to collect the reflected light. This device allows us to follow the microcantilever’s deflection, during a cyclic voltammetry experience, occurring as the result of the Ferrocene’s oxidation to Ferrocenium at the top of the SAM.

The results presented are those of the effect of the alkyl chain length of the SAM on the microcantilever’s redox deflection.

We fabricated, both on rigid and flexible substrates, electrolyte-gated (EG) TiO₂ and SnO₂ transistors making use of high surface area activated carbon (AC) as a gate electrode and the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][TFSI] and [EMIM][TFSI] mixed with lithium perchlorate as the gating media. Thin films of metal oxides have been deposited by thermal evaporation and sol gel techniques and were photolithographically patterned as transistor channel materials.

To explore the effect of the double layer capacitance on device performance we investigated bottom-contact top-gated transistor where we varied the area of the active layer in contact with electrolyte and the area of overlap of the source/drain electrodes with the gate. The influence of different film morphology and the effect of the size of electrolyte ions on charge carrier density modulation in transistors was introduced. We believe that these simple architecture devices working at low voltages are promising for flexible, transparent and bio electronic applications.

GL13 peptides are novel thirteen-residue peptides that are derived from the sequence in the human salivary parotid secretory protein (PSP) that is believed to have antimicrobial properties. GL13K is a small, cationic peptide with a net charge of +5 at physiological pH that has strong activity against Gram-negative and biofilm-forming bacteria while exhibiting low hemolytic and cytotoxic activity.

Model membrane studies have shown that GL13K attacks membranes with high specificity, and folds into β-sheets in the presence of anionic membranes. On the other hand, GL13K does not appear to interact with membranes in the absence of anionic lipids. In this study, we probe the impact of cholesterol incorporation on the interaction of GL13K with model membranes as cholesterol affects both membrane packing and rigidity. The model membrane systems that will be used are 1,2-dioleoylphosphatidylglycerol (DOPG) and mixed-lipid systems at various DOPG:cholesterol composition ratios. Results from liposome (circular dichroism and total internal reflectance fluorescence microscopy) and monolayers studies (isotherms and polarization modulation-infrared reflection absorption spectroscopy) are used to understand the behavior of this peptide at the membrane biointerface.

We have grown patterned low-aspect-ratio, well-separated single ZnO nanorods using a hydrothermal method on two different substrates with dissimilar crystal orientations. ZnO nuclei have been used as a seed layer to compensate the crystal mismatch between the substrates and nanorods. Based on XRD results, in order to have highly oriented nanorods, the seed layer must be annealed over 300 ̊ C. Micro-Raman spectra show that our patterned nanorods have a wurtzite crystal structure, with most nanorods presenting vertical orientation relative to the substrate. Room-temperature micro-photoluminescence (PL) spectra from the nanorods show sharp band edge emission at 385 nm and a common broadband defect emission in the visible range. Our method is a significant step towards an economical controlled synthesis of 1D ZnO for application in mass-production advanced devices.

Monocytes and macrophages play an initiating role in the foreign body response to biomaterial implants. The interactions between monocytes and biomaterials can potentially be modulated by controlling the surface chemistry and morphology of biomaterials. Organic coatings with varying oxygen and nitrogen concentration were prepared by low-pressure plasma co-polymerization of binary gas mixtures combining a hydrocarbon (C₂H₄ or C₄H₆) and a heteroatom-containing gas. (NH₃ or CO₂). The effect of surface chemistry on protein adsorption and on adhesion and differentiation of inflammatory cells to plasma polymer films containing tuneable concentrations of N and O functional groups were investigated. The study of protein adsorption by surface plasmon resonance results and the cell culture experiments revealed that the presence of albumin on the surface appears to act as an indicator for cell adhesion within the scope of our study.

This paper presents a computational Scanning Tunneling Microscope (STM) where interactive intrusion of molecular systems, subsequent molecular relaxation, and nearly real-time STM images are considered. Our approach was validated with the three following experiments: (1) the metalation of a porphyrin on Ag(111), (2) the intermediates in the Ulmann reaction of bromobenzene on Cu(111), and (3) the influence of halogen bonds on the formation of 2D islands on Si(111)-B. The metal-porphyrin is an interesting system for STM simulation because the presence of cobalt or iron atom provokes a significant relaxation of the organic fragment. The Ulmann coupling remains a quite challenging reaction to model, and more especially for identifying the chemical intermediate species. Here, we have i) intrusively broken the C-Br bond, ii) identified the adsorbed intermediate, iii) and finally initiated the coupling between two adsorbed species. The obtained molecular geometries are in good agreement with experimental results and DFT calculations. Finally, we study the influence of halogen bonds on the formation of molecular islands on the Si(111)-B. The weakening of the molecule-surface interactions through the presence of an increasing amount of halogen atoms, we observed that the packing of molecules can go from isolated nanolines to highly packed 2D monolayer.

Development of modified surfaces using self-assembled monolayers (SAMs) of aminosilanes, is one of the extensively used methods for covalent attachment of organic and inorganic materials. This capacity of silane coupling agents, makes them a promising candidate for producing bio-functional and biosensing surfaces.

Here, we set out to endothelialize a glass surface by establishing a procedure in which endothelial cells are attached to the surface using a specific ligand (i.e. CD34 antibody). For this purpose, glass samples were first functionalized using (3-Aminopropyl)triethoxysilane (APTES). We explored two methods for the amino-silanization process, namely, chemical vapor deposition (CVD) and Liquid-phase deposition (LPD). Results were evaluated using contact angle measurements and X-ray photoelectron spectroscopy (XPS). To further validate the existence of amino-silane on silanized glass samples, an amine targeting fluorescent dye, fluorescein isothiocyanate isomer I, was employed and results were verified using fluorescence microscopy and were quantified using ImageJ software. The amino-silanized glass samples were further coated with fluorescently labelled CD34 monoclonal antibody using EDC/NHS chemistry and were imaged using fluorescent microscopy. We have demonstrated successful coating of the surface with endothelial cell’s specific ligands (CD34) using both CVD and LPD. Moving forward, we will evaluate human endothelial cell culture on the produced surfaces.

Most known octa-alkylthio substituted tetraazaporphyrins (TAPs) have eight identical groups because their synthesis is much more straightforward. The generation of more amphiphilic TAPs, however, requires the attachment of at least two different types of substituents, one of hydrophilic and one of hydrophobic character. Amphiphilic TAPs are important building blocks for the formation of thin films by the LB and other techniques and the incorporation of TAPs into biological structures such as cell membranes. Presented here is the synthesis and properties of the first TAP containing four hydrophobic alkyl chains and four alkyl chains terminated with polar carboxylic acid groups. The synthetic approach required the development of a step-wise alkylation of sodium maleonitriledithiolate, which was best achieved by flow chemistry rather than batch reactions. The free-base TAP shown below was then prepared by the established cyclization in Mg propanolate. Its properties, such as solubility and arrangement at interfaces, will be reported and compared to previously studied symmetric TAP derivatives with eight terminal carboxylic acid groups.

Some mycobacteria produce special types of surface substance during the growth phase that causes them to stick together in a parallel fashion way. In some infectious diseases, these ordered structures provide an important reservoir of cells that repopulate colonized sites upon removal of drug treatment. Understanding biostructure properties and how it can be affected by chemical treatment could lead to improvement in treatment of these infectious diseases. The viscoelastic properties of biostructures can be studied using the liquid-crystal theory while the growth and division of individual cells in a confined capillary show a dynamical transition from an isotropic disordered phase to a nematic phase characterized by orientational order. In this work, using a mathematical model based on the radial and pair distribution functions, we present a method to estimate the order parameter of bacterial cell structures. Our results, in agreement with experimental data, showed the order parameter of bacterial cells can decrease by up to 20% in the present of antibiotic. These results treated with an analogy to the Namtic-Elastica model, can be used to estimate the physical and mechanical properties of confined cell populations.

Low-density polyethylene composites including different amounts of graphene-like and carbon black additives having between 0 wt% to 30 wt% were fabricated by means of melt compounding.

Graphene-like additive was produced from natural resources such as sugar and bentonite by caramelization and pyrolization at 800 ⁰C under inert condition. Scanning electron microscopy (SEM) characterizing of graphene-like additive illustrated anisotropic morphology with some heavy groups.

Thermogravimetric analysis (TGA) confirmed the accuracy of the additive concentrations as well as a substantial improvement in thermal degradation by 50-70 ⁰C for both composites.

Mechanical properties results proved addition of 30 wt% graphene-like additive and 30 wt% carbon black improved Young’s modulus by 35 and 56 %, respectively.

Thermal conductivity behavior of the composite demonstrated that 20 wt% carbon black formed a conducting network to transfer heat readily.

Dielectric response results demonstrated the formation of electrical network with addition of 25 wt% carbon black to the LDPE, the composite being found electrically conductive.

The chemical interface between additives and host polymer plays an important role in all of the aforementioned properties. Thus, the miscibility of the components and creation of covalence and Wan der Waals bonds between the additives and matrix can be the most determining factors

As oxygen is inhaled it has to first cross a very thin layered membrane, lung surfactant, before it can enter the bloodstream. This lung surfactant membrane is composed of saturated and unsaturated phospholipids and membrane proteins which serve to reduce the surface tension at the air-liquid interface of the alveoli preventing alveolar collapse. To maintain this function through repetitive compression-expansion cycles, the film employs a mechanism of reversible reservoir formation and exhibits a high degree of fluidity. The inhalation of nanoparticulate may interfere with the functional properties of pulmonary surfactant including lowering the film collapse, altering viscoelastic properties and modifying lipid reservoir formation. This study aims to determine the degree to which nanoparticles interfere with the phase structure, compressibility, and viscoelastic properties when they deposit on the lipid membrane. The lung surfactant films are modelled using monolayers of lipid-only mixtures and natural membrane extracts, namely Survanta and Infasurf (two clinical formulations comprising extracted lipids and proteins in different ratios). Surface pressure area-isotherms, Brewster angle microscopy, rheological measurements and GIXD data of films in the absence and presence of cationic, neutral and anionic silica nanoparticles will be presented.

Superhydrophobic surfaces are conventionally prepared employing two steps: roughening a surface and lowering their surface energy. It is known that the cleaned coppers substrates when immersed in an ethanolic stearate solution transforms anodic electrode into the superhydrophobic surface due to reaction between copper and stearic acid. In the present work, superhydrophobic nanocomposite films were coated on a copper surface via a one-step electrochemical modification process in an ethanolic stearic acid (SA) solution containing CeO₂ nanoparticles with and without Cu²⁺ ions under a DC voltage. It was observed that the superhydrophobic composite thin films composed of CeO₂ nanoparticles and copper stearate on copper substrates. This nanocomposite thin film shows superhydrophobic characteristics with water roll of properties. Superhydrophobic nanocomposite thin film was characterized using X-ray diffraction, infrared (IR) spectroscopy and scanning electron microscopy. Effect of CeO₂ nanoparticles on the corrosion resistance of the coating was also studied using electrochemical methods such as electrochemical impedance spectroscope and potentiodynamic polarization test. Additionally, this versatile method can also be used to modify any conducting surfaces.

Well-defined amphiphilic block copolymers exhibiting stimuli-responsive degradation (SRD) have shown immense potential for drug delivery application because of their ability to self-assemble and encapsulate hydrophobic drugs. SRD-based nanocarriers exhibit the unique property of undergoing dissociation in a controlled fashion, as a result of cleavage of dynamic covalent bond in response to external stimuli. In particular, pH- and reduction-responsive nanocarries, have received increasing attention owning to the fact that tumor microenvironment and cancer cells show acidic pH and elevated concentration of glutathione as compared to normal cells.

Recent advance in designing effective SRD systems centers on the development of new intracellular nanocarriers designed with multiple stimuli-responsive cleavable linkages at multiple locations. This strategy dramatically increases versatility since responses to each stimulus can independently and precisely regulate release of encapsulated biomolecules at several locations. We present a new dual stimuli acidic pH/glutathione-responsive block copolymer consists of hydrophilic poly(ethylene glycol) (PEG) block that is linked with a hydrophobic polymethacrylate block having pendant disulfide linkages (PHMssEt) through ketal linkage; thus PEG-ketal-PHMssEt. The copolymer self-assembles to form micellar nanostructures with ketal linkages at core/corona interfaces to promote cellular uptake after extravasation into tumors and glutathione-responsive disulfide linkages in cores to enhance drug release.