Waterloo Institute for Nanotechnology

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Sensing guanine and its derivatives: From molecular recognition to applications
(Elsevier, 2020-11) Li, Yuqing; Liu, Juewen
Guanine plays an indispensable role in building nucleic acids, and its derivatives take part in various cellular functions such as regulating biological reactions and signal transduction. Monitoring the levels of guanine and its derivatives is critical for understanding their biological roles and related diseases. Aside from traditional chromatography-based methods, majority of the current detections were based on electrochemistry and the oxidation activity of guanine, for which guanine and adenine often had a similar response. Over the last 30 years, various new sensing strategies have been developed. To provide researchers with more options for specific sensing of guanine and its derivatives, herein we review molecular recognition strategies based on nucleic acids, proteins, small organic molecules, molecularly imprinted polymers to nanomaterials. The mechanism of each molecular recognition strategy is discussed. Based on these target recognition molecules, we also critically review representative fluorescent and electrochemical sensors for guanine-related analytes from an application point of view, and provide readers with our perspectives to further grow this direction.
Nature-inspired robust hydrochromic film for dual anticounterfeiting
(Elsevier, 2021-06) Si, Pengxiang; Liang, Mingrui; Sun, Manyou; Zhao, Boxin
Nature-inspired materials have been actively developed for anticounterfeiting applications. Among a variety of stimuli-responsive anticounterfeiting strategies, hydrochromic materials exhibit reversible color change in response to moisture or water and have the advantage of being easy to authenticate. However, the security level of current hydrochromic anticounterfeiting materials is not sufficient for practical applications since they only exhibit a single anticounterfeiting function, where the information switches between visible and invisible. To improve the security level and efficiency of hydrochromic anticounterfeiting materials, here we developed a robust dual hydrochromic material via the self-assembly of polyurethane (PU)-polyelectrolytes colloids with which the desired information can not only switch between visible and invisible but also transform from one pattern to another within 3 s without the need of any external instruments. The bio-inspiration, material design and demonstrated hydrochromic properties might have profound implications for using colloidal complexes to make advanced anticounterfeiting materials.
Catalytic Nucleic Acids: Biochemistry, Chemical Biology, Biosensors, and Nanotechnology
(Elsevier, 2020-01) Ma, Lingzi; Liu, Juewen
Since the initial discovery of ribozymes in the early 1980s, catalytic nucleic acids have been used in different areas. Compared with protein enzymes, catalytic nucleic acids are programmable in structure, easy to modify, and more stable especially for DNA. We take a historic view to summarize a few main interdisciplinary areas of research on nucleic acid enzymes that may have broader impacts. Early efforts on ribozymes in the 1980s have broken the notion that all enzymes are proteins, supplying new evidence for the RNA world hypothesis. In 1994, the first catalytic DNA (DNAzyme) was reported. Since 2000, the biosensor applications of DNAzymes have emerged and DNAzymes are particularly useful for detecting metal ions, a challenging task for enzymes and antibodies. Combined with nanotechnology, DNAzymes are key building elements for switches allowing dynamic control of materials assembly. The search for new DNAzymes and ribozymes is facilitated by developments in DNA sequencing and computational algorithms, further broadening our fundamental understanding of their biochemistry.
Cellulose nanocrystals in smart and stimuli-responsive materials: a review
(Elsevier, 2020-03) Nasseri, R.; Deutschman, C.P.; Han, L.; Pope, Michael; Tam, K. C.
“Smart” stimuli-responsive materials have been the subject of decades of research because of their versatility and particularly their use in medical and sensing applications. While these materials are often composed exclusively of responsive polymers, there is growing interest in smart hybrid systems that contain at least two distinct components, each contributing uniquely to the final material. Cellulose nanocrystals (CNCs) have found extensive application in smart hybrid systems, as CNCs can both contribute to the mechanical and optical properties of the system and bear stimuli-responsive surface modifications. This review covers the recent body of work on CNC-containing smart hybrid systems, with attention given to the fabrication methodologies that have been employed to generate both physically and optically adaptable CNC-based smart systems. Additionally, the unique application of CNCs in self-healing composites and shape memory polymers will be discussed.
Tunable covalent organic framework electrochemiluminescence from non-electroluminescent monomers
(Elsevier, 2021-10) Cui, Wei-Rong; Li, Ya-Jie; Jiang, Qiao-Qiao; Wu, Qiong; Liang, Ru-Ping; Luo, Qiu-Xia; Zhang, Li; Liu, Juewen; Qiu, Jian-Ding
It is hard to find new electrochemiluminescence (ECL) luminophores using existing research strategies, especially from ECL non-active monomers. Here, fully conjugated covalent organic frameworks with trithiophene (BTT-COFs) are found to have ultra-high ECL efficiencies (up to 62.2%), even in water and without exogenous co-reactants. Quantum chemistry calculations confirm that the periodic BTT-COFs arrays promote intramolecular electron transfer generating ECL from non-ECL monomers. Modulation of ECL performance is possible by substituting the monomers for those with different electron-withdrawing properties. In addition, the cyano group weaved in the skeleton provides the dense sites for post-functionalization. As a typical use case, a highly selective ECL probe for uranyl ions is reported. The tunable ECL luminophore family possesses a broader development space than the traditional emitters, demonstrates the prospects of ECL-COFs, and affords an idea for detecting various contaminants through the rational design of target ligands.
Self-Assembly of Amphiphilic Nanoparticle-Coil “Tadpole” Macromolecules
(American Chemical Society, 2004) Lee, Jae Youn; Balazs, Anna C.; Thompson, Russell B.; Hill, Randall M.
None.
Self-Assembly of Amphiphilic Nanoparticle-Coil “Tadpole” Macromolecules
(American Chemical Society, 2004) Lee, Jae Youn; Balazs, Anna C.; Thompson, Russell B.; Hill, Randall M.
There has been considerable fascination with the self-assembling behavior of amphiphilic chainlike molecules that range from short-chain surfactants to high molecular weight block copolymers. The self-assembly of simple amphiphiles into membranes may have played an important role in the origin of life. The self-organization of amphiphiles with more complex architectures can lead to a stunning variety of complex morphologies. In the case of short-chain surfactants, the equilibrium morphology of the self-assembled sys- tem depends on geometric factors, such as the ratio of the “head” to “tail” sizes. Here, the headgroups are small molecules and the tails are coillike. In the case of block copolymers, the structure of the melt depends on the relative composition of the chains, the degree of polymerization, and the incompatibility between the different blocks.
Origins of Elastic Properties in Ordered Block Copolymer/Nanoparticle Composites
(American Chemical Society, 2004) Thompson, Russell B.; Rasmussen, Kim O.; Lookman, Turab
We predict a diblock copolymer melt in the lamellar phase with added spherical nanoparticles that have an affinity for one block to have a lower tensile modulus than a pure diblock copolymer system. This weakening is due to the swelling of the lamellar domain by nanoparticles and the displacement of polymer by elastically inert fillers. Despite the overall decrease in the tensile modulus of a polydomain sample, the shear modulus for a single domain is unaffected by fillers.
Ordering mechanisms in triblock copolymers
(American Physical Society, 2004) Maniadis, P.; Thompson, Russell B.; Rasmussen, Kim O.; Lookman, Turab
The ordering mechanisms for an ABC triblock copolymer system are studied using self-consistent field theory. We find a two-phase mechanism, similar to what has been suggested experimentally 􏰖two-step mecha- nism􏰌. Analysis of free energy components shows that the two-phase process comes about through a compe- tition between stretching energy and interfacial energy. The mechanism is found to be sufficiently robust so as to make it potentially useful for device applications.
Evaluating Characteristic Parameters for Carbon Dioxide in the Sanchez−Lacombe Equation of State
(American Chemical Society, 2017) von Konigslow, Kier; Park, Chul B.; Thompson, Russell B.
For many different pure substances, large numbers of competing characteristic parameter sets exist in the literature for the Sanchez−Lacombe equation of state. This is due in part to differing research requirements or differing procedures used for determining the parameters. The existing parameters for carbon dioxide are reviewed in order to determine whether a single set of parameters can describe the equation of state over large ranges of temperature and pressure. It is found that by consideration of a large collection of experiments, a good fit can be achieved over much larger temperature and pressure ranges than previously thought possible. Properties directly related to the equation of state, such as the thermal expansivity and isothermal compressibility, are also predicted well; however, as expected, properties that depend on the internal degrees of freedom of molecules, such as the specific heats, do not correlate well. Closely agreeing parameter sets are found in the literature that fit the equation of state data reasonably well over a large range. A new set of parameters is found using a least-squares approach over the largest ranges of temperature and pressure to date. These parameters are found to be P* = 419.9 MPa, T* = 341.8 K, and ρ*= 1.397 g/cm3 using N = 556 experimental data points over the temperature range of 216.58−1800 K and the pressure range of 0.5−66.57 MPa.
Effect of well-dispersed surface-modified silica nanoparticles on crystallization behavior of poly (lactic acid) under compressed carbon dioxide
(Elsevier, 2016) Sarikhani, K.; Nasseri, R.; Lotocki, V.; Thompson, Russell B.; Park, Chul B.; Chen, Pu
In this work, the crystallization behavior of poly (lactic acid) (PLA)/amine-modified silica nano- composites at different loadings of amine-modified silica (1, 2, and 8 wt %) under isothermal, non- isothermal, and isothermal under compressed CO2 is studied. A significant improvement in crystalliza- tion rate was observed after introduction of the nanoparticles. A modified Hoffman-Lauritzen nucleation theory was utilized to explain the facilitation and acceleration of the crystallization process of nano- composites with introducing the surface energy of the nanoparticles and interfacial energy between polymer/nanoparticle into the rate equation. After incorporation of the nanoparticles, three-dimensional spherulites formed sporadically in the PLA matrix based on the prediction of the Avrami exponents of the nanocomposites. High-pressure DSC results also showed an increase in the crystallization rate at 15 bar compared with the atmospheric pressure condition. However, an increase in pressure up to 21 bar had no significant effect on the crystallization rate. The PLA nanocomposites with lower molecular weights and D-content also showed a significant increase in the crystallization rate but with no change in the crys- tallization mechanism.
Polymeric Foaming Predictions from the Sanchez-Lacombe Equation of State: Application to Polypropylene-Carbon Dioxide Mixtures
(American Physical Society, 2017) Thompson, Russell B
A simple off-lattice method of deriving the Sanchez-Lacombe equation of state is presented. The Sanchez-Lacombe equation of state for mixtures is shown to be thermodynamically inconsistent for all mixing rules in such a way that fugacity coefficients, until now thought to correct for mixing inconsistencies, cannot make the theory consistent. The theory is consistent, however, for constant hole volumes and it is shown, for a sample mixture of polypropylene and carbon dioxide, that excellent agreement with experimental solubility results is achieved without changing the mixture parameters with temperature or pressure. To this end, pure-component Sanchez-Lacombe characteristic parameters for both branched and linear polypropylene are also provided. The agreement between theory and experiment for solubility using a constant hole volume for carbon dioxide mixtures with both branched and linear polypropylene is much better than for typical mixing rules for the Sanchez-Lacombe equation of state. Fair agreement with experimental swelling-ratio data at saturation is also achieved with no further free parameters, making this equation of state a good choice for predictions related to polymeric foaming. A consideration of the hole volume is given in terms of correlations, and evidence to support this perspective is presented in terms of the characteristic parameters regressed from different architectures of pure polypropylene. It is shown that only a single pure-polypropylene characteristic parameter is needed to characterize mixtures with carbon dioxide, and that an estimate of this parameter can be extracted from mixture solubility data. This example demonstrates the feasibility of applying the Sanchez-Lacombe equation of state to mixtures in which one of the pure components has not been independently characterized.
Application of a constant hole volume Sanchez–Lacombe equation of state to mixtures relevant to polymeric foaming
(Royal Society of Chemistry, 2018) Park, Chul B.; von Konigslow, Kier; Thompson, Russell B.
A variant of the Sanchez–Lacombe equation of state is applied to several polymers, blowing agents, and saturated mixtures of interest to the polymer foaming industry. These are low-density polyethylene– carbon dioxide and polylactide–carbon dioxide saturated mixtures as well as polystyrene–carbon dioxide–dimethyl ether and polystyrene–carbon dioxide–nitrogen ternary saturated mixtures. Good agreement is achieved between theoretically predicted and experimentally determined solubilities, both for binary and ternary mixtures. Acceptable agreement with swelling ratios is found with no free parameters. Up-to-date pure component Sanchez–Lacombe characteristic parameters are provided for carbon dioxide, dimethyl ether, low-density polyethylene, nitrogen, polylactide, linear and branched polypropylene, and polystyrene. Pure fluid low-density polyethylene and nitrogen parameters exhibit more moderate success while still providing acceptable quantitative estimations. Mixture estimations are found to have more moderate success where pure components are not as well represented. The Sanchez–Lacombe equation of state is found to correctly predict the anomalous reversal of solubility temperature dependence for low critical point fluids through the observation of this behaviour in polystyrene nitrogen mixtures.
Wetting, adhesion and droplet impact on face masks
(ACS, 2021-02-12) Melayil, Kiran Raj; Mitra, Sushanta K.
In the present pandemic time, face masks are found to be the most effective strategy against the spread of the virus within the community. As aerosol-based spreading of the virus is considered as the primary mode of transmission, the interaction of masks with incoming droplets needs to be understood thoroughly for an effective usage among the public. In the present work, we explore the interactions of the droplets over the most commonly used 3-ply surgical masks. A detailed study of the wetting signature, adhesion and impact dynamics of water droplets and microbe-laden droplets is carried out for both sides of the mask. We found that the interfacial characteristics of the incoming droplets with the mask are very similar for the front and the back side of the mask. Further, in an anticipated attempt to reduce the adhesion, we have tested masks with a superhydrophobic coating. It is found that a superhydrophobic coating may not be the best choice for a regular mask as it can give rise to a number of smaller daughter droplets and thus can linger in air for longer time and can contribute to the transmission of potential viral loads.
Microparticle suspensions and bacteria laden droplets: Are they the same in terms of wetting signature?
(ACS, 2021-01-17) Melayil, Kiran Raj; Misra, Sirshendu; Mitra, Sushanta K.
Adhesion behavior of microbial pathogens on commonly encountered surfaces is one of the most pertinent questions now. We present the characterization of bacteria laden droplets and quantify the adhesion forces on highly repellent surfaces with the help of a simple experimental setup. Comparing the force signature measured directly using an in-house capillary deflection based droplet force apparatus, we report an anomalous adhesion behavior of live bacteria (E. coli) laden droplets on repellent surfaces, which stands in stark contrast to the observed adhesion signature when the doping agent is changed to inert microparticles or the same bacteria in an incapacitated state. We showed that the regular contact angle measurements using optical goniometry is unable to differentiate between the live bacteria and the dead ones (including microparticles) and thus delineate its limitations and the complementary nature of the adhesion measurements in understanding the fundamental interfacial interaction of living organisms on solid surfaces.
Friction and Adhesion of Microparticle Suspensions on Repellent Surfaces
(ACS, 2020-11-06) Melayil, Kiran Raj; Misra, Sirshendu; Mitra, Sushanta K.
With the recent advancements in the development and application of repellent surfaces, both in air and under liquid medium, accurate characterization of repellence behavior is critical in understanding the mechanism behind many observed phenomena and to exploit them for novel applications. Conventionally, the repellence behavior of a surface is characterized by optical measurement of the dynamic contact angle of the target (to be repelled) liquid on the test surface. However, as already established in literature, optical measurements are prone to appreciable error, especially for repellent surfaces with high contact angle. Here, we present an alternative, more accurate force-based characterization method of both friction and adhesion forces of microparticle laden aqueous droplets over various repellent surfaces, where the force signature is captured by probing the surface with a droplet of the test liquid mounted at the tip of a flexible cantilever and then tracking the deflection of the tip of the cantilever as the probe droplet interacts with the surface. A systematic investigation of response of repellent surfaces towards droplets with different microparticle concentration revealed the dependency and sensitivity of measured adhesion and friction signature towards particle concentration. A comparison with theoretical estimate from optical goniometry highlights the deviation of the theoretical data from experimentally measured values and further substantiates the need of such a force-based approach for accurate characterization of repellence behavior.
Detection of Nitroaromatics Using the Excimer Fluorescence of Pyrene-Labeled Starch Nanoparticles
(American Chemical Society, 2019-09-09) Patel, Sanjay; Seet, Jonathan; Li, Lu; Duhamel, Jean
Starch nanoparticles (SNPs) were hydrophobically modified using 1-pyrenebutyric acid (PyBA) with degrees of substitution (DS) between 0.0006 and 0.11. Fluorescence quenching studies were conducted on the pyrene-labeled starch nanoparticles (Py-SNPs) in dimethyl sulfoxide (DMSO) and water with nitromethane (NM), 4-mononitrotoluene (MNT), 2,6-dinitrotoluene (DNT), and 2,4,6-trinitrotoluene (TNT) to assess the mode of quenching of the pyrene labels in the two solvents. In DMSO where pyrene, starch, and the quenchers were soluble, a decrease in fluorescence signal was the result of dynamic encounters between the excited pyrene labels and the nitrated quenchers. In water where starch could be dispersed but pyrene and the nitroaromatic compounds (NACs) were insoluble, quenching took place through the binding of NACs to pyrene aggregates. Py(11)-SNPs (Py-SNPs with a DS of 0.11) coated filter papers (Py-CFPs) were prepared as fluorescence sensors. The fluorescence emitted by Py-CFPs was quenched to 25% of its original value within 10 (± 2), 72 (± 20), and 23 (± 4) s upon exposure to vapors of MNT, DNT, and TNT, respectively. When known amounts of NACs were deposited onto Py-CFPs, their limit of detection (LOD) when the fluorescence decreased by more than three standard deviations (3) from its original value equaled 9.2 (± 0.8), 3.3 (± 0.5), and 0.20 (± 0.02) ng/mm for MNT, DNT, and TNT, respectively. These response times and LODs were among the best values reported to date in the scientific literature for fluorescence sensors. The selectivity of the Py-CFPs toward NACs was also investigated by comparing their response to the presence of non-nitrated aromatics, amines, and aromatic ketones. Quenching was only observed with the latter family of chemicals tested, but with much lower efficiency compared to TNT, thus reflecting some level of selectivity toward this specific NAC.
Probing the Interactions between Mimics of Pour Point Depressants (PPDs) and Viscosity Index Improvers (VIIs) in Engine Oil Using Fluorescently Labeled PPDs
(American Chemical Society, 2019-03-18) Gholami, Kiarash; Jiang, Sheng; Duhamel, Jean
The level of interpolymeric interactions experienced by a pyrene-labeled poly(octadecyl methacrylate) labeled with 6.7 mol% of 1-pyrenebutanol (Py(6.7)-PC18MA) was characterized by fluorescence in the presence of an amorphous (EP(AM)) and a semicrystalline (EP(SM)) ethylene propylene copolymer. These polymers belong to different families of engine oil additives. The fluorescence spectra of Py(6.7)-PC18MA solutions in engine oil were acquired and analyzed to obtain finter, the molar fraction of pyrene labels that formed excimer intermolecularly upon encounter between an excited and a ground-state pyrene. The fraction finter was measured as a function of solution temperature between 30 and +25 oC. The finter-vs-T profiles obtained for Py(6.7)-PC18MA showed a sharp transition between +10 and +15 oC indicating an increase in intermolecular interactions at temperatures lower than the transition. This behavior was attributed to the crystallization of the PC18MA octadecyl side chains. Addition of EP(AM) resulted in an increase in interpolymeric interactions between Py(6.7)-PC18MA macromolecules at all solution temperatures studied. Addition of EP(SM) increased finter for Py(6.7)-PC18MA at high temperatures, but at lower temperatures where EP(SM) formed microcrystals, finter for Py(6.7)-PC18MA returned to its original value when no EP(SM) was present in solution. These trends indicated that PC18MA interacted with the EP copolymers as long as the copolymers remained solvated. Crystallization of EP(SM) released the polyolefin from PC18MA and PC18MA resumed its original level of intermolecular interactions as if no polyolefin was present in the solution. These experiments extended our earlier finding established with pyrene-labeled EP copolymers that finter is a powerful analytical means to quantify the level of intermacromolecular interactions taking place during the crystallization of polymers and monitor their interactions with other macromolecules in solution.
Surfactant-Structure Dependent Interactions with Modified Starch Nanoparticles Probed by Fluorescence Spectroscopy
(American Chemical Society, 2019-02-05) Zhang, Qian; Kim, Damin; Li, Lu; Patel, Sanjay; Duhamel, Jean
The interactions between the surfactants sodium dodecyl sulfate (SDS) and sodium dioctylsulfosuccinate (AOT) and starch nanoparticles hydrophobically modified with the hydrophobic dye pyrene (Py-SNPs) were investigated in water by steady-state and time-resolved fluorescence. The Py-SNPs formed interparticulate aggregates in water which were disrupted by adding SDS to the Py-SNP aqueous dispersions. SDS was found to interact with Py-SNPs at SDS concentrations that were close to two orders of magnitude lower than its CMC. These interactions led to the breakup of the Py-SNP aggregates which was confirmed by conducting fluorescence resonance energy transfer (FRET) experiments between naphthalene-labeled SNPs (Np-SNPs) and Py-SNPs. By the time the SDS concentration reached the CMC of SDS, the Py-SNPs were separated from each other and excimer was generated from isolated Py-SNPs in the aqueous dispersions. While SDS interacted with the Py-SNPs at SDS concentrations lower than CMC, SDS did not seem to target the hydrophobic pyrene aggregates. Only above the CMC did SDS appear to interact with the pyrene aggregates as evidenced from diffusive pyrene excimer formation between excited and ground-state pyrenes. Most surprisingly, no interaction was observed between sodium dioctyl sulfosuccinate (AOT) and Py-SNP at AOT concentrations where SDS interacted with the Py-SNPs. This observation led to the conclusion that SDS below its CMC interacted not with hydrophobic pyrene aggregates, but rather through the formation of inclusion complexes which led to the electrostatic stabilization of individual Py-SNPs and enabled the breakup of Py-SNP aggregates. The formation of inclusion complexes with linear surfactants like SDS might thus provide a new means of stabilizing HMSNPs in water which bears the promise of finding future applications.
Design, characterization, optical and photophysical properties of novel thiophene monomers and polymers containing pyrene moieties linked via rigid and flexible spacers
(Elsevier, 2019-02-01) Morales-Espinoza, Eric G.; Ruiu, Andrea; Valderrama-Garcia, Bianca X.; Duhamel, Jean; Rivera, Ernesto
Herein, we report the synthesis of three novel thiophene monomers connected to pyrene moieties via a flexible oligo(ethylene glycol) (OEG) spacer with an oxygen -to-pyrene (T1), a flexible OEG spacer with an oxygen -to-pyrene (T2), and a rigid acetylene spacer (T3). These monomers were prepared in an easy manner from commercially available 3-bromo-4-methylthiophene and further characterized by NMR spectroscopy and mass spectrometry. Monomer T2 exhibited the absorption band at 344 nm and a strong “monomer” emission band at 375 nm typical of a 1-pyrenemethyl derivative. Moreover, T1 and T3 showed red shifted absorption bands at 352 and 384 nm arising from the pyrene substituents, namely the electron-donating oxygen to-pyrene and the extended conjugation length, respectively. These compounds exhibited a broad “monomer” emission band between 360~480 nm without excimers. Homopolymers (OHP1, OHP2, and OHP3) obtained from these monomers were partially soluble and their photophysical properties such as quantum yield and lifetime were characterized. Emission spectra of the oligomers OHP1 and OHP3 exhibited an emission band at ~500 nm, which is due to the conjugated polythiophene backbone and does not arise from intramolecular pyrene-pyrene interactions.

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