2021

Permanent URI for this collectionhttps://hdl.handle.net/1807/104120

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Dicarbonyl anthracenes and phenanthrenes as singlet fission chromophores
(Canadian Science Publishing, 2021-12-07) James, Dylan; Pradhan, Ekadashi; Lee, Seunghoon; Choi, Cheol Ho; Zeng, Tao
Singlet fission is a highly desired process in photovoltaic devices as it can significantly enhance photoelectric conversion efficiency. Exploitation of this process in photovoltaics is hindered by the lack of appropriate chromophores. We used mixed-reference spin-flipping time-dependent density functional theory to investigate five di-carbonyl anthracenes and phenanthrenes, with the purpose to design singlet fission chromophores. Two molecules were found to be promising candidates. For all the dicarbonyl molecules, the oxygen lone pair orbitals were found to be involved in the excited states that are relevant to singlet fission.
Methods to identify and characterize iron-sulfur oligopeptides in water
(Canadian Science Publishing, 2021-12-12) Valer, Luca; Rossetto, Daniele; Scintilla, Simone; Hu, Yin Juan; Tomar, Anju; Nader, Serge; Betinol, Isaiah O.; Mansy, Sheref
Iron-sulfur clusters are ubiquitous cofactors that mediate central biological processes. However, despite their long history, these metallocofactors remain challenging to investigate when coordinated to small (≤ six amino acids) oligopeptides in aqueous solution. In addition to being often unstable in vitro, iron-sulfur clusters can be found in a wide variety of forms with varied characteristics, which makes it difficult to easily discern what is in solution. This difficulty is compounded by the dynamics of iron-sulfur peptides, which frequently coordinate multiple types of clusters simultaneously. To aid investigations of such complex samples, a summary of data from multiple techniques used to characterize both iron-sulfur proteins and peptides is provided. Although not all spectroscopic techniques are equally insightful, it is possible to use several, readily available methods to gain insight into the complex composition of aqueous solutions of iron-sulfur peptides.
Raman area- and thermal- mapping studies of faceted nano-crystalline α-Fe2O3 thin films deposited by spray pyrolysis
(Canadian Science Publishing, 2021-12-06) Pathak, Devesh K.; Dayanand, D; Thakur, O P; Kumar, Rajesh
Different advanced techniques including Raman area mapping and Raman thermal imaging has been used to investigate various properties of large area iron oxide thin films deposited by spray pyrolysis, on a large area of crystalline silicon substrates under controlled external parameters. Morphological studies reveal that the obtained films acquire lateral faceted crystalline structure of iron oxide. The Raman and SEM images, in unison, confirm the presence and large area distribution of the nano crystals of Fe2O3 phase. Thermal Raman imaging reveals that the obtained iron oxide thin films are robust and thus can be used for appropriate technological applications like electromagnetic shielding.
Lactide polymerization using a sterically encumbered, flexible zinc complex
(Canadian Science Publishing, 2021-09-29) Dordahan, Fatemeh; Schaper, Frank
4-(tert-Butyl)-2-trityl-6-(di-(2-picolyl)amine)phenol, LH, was prepared from paraformaldehyde, 4-(tert-butyl)-2-tritylphenol and di-(2-picolyl)amine. Reaction with Zn(N(SiMe3)2)2 gave LZnN(SiMe3)2. The complex was shown by X-ray diffraction study, variable temperature NMR and DFT calculations to coordinate only one pyridine ligand, which allows for fast and facile complex isomerisation. LZnN(SiMe3)2 was active in rac-lactide polymerization, but in contrast to previous complexes of this type did not show any evidence for isotactic monomer enchainment via a catalytic-site mediated chain-end control mechanism. Addition of alcohol led to increased activity, but the complex was unstable in the presence of free alcohol.
Identification of Novel Potential Anti-Diabetic Candidates targeting Human Pancreatic ɑ-Amylase and Human ɑ-Glycosidase: An Exhaustive Structure-based Screening
(Canadian Science Publishing, 2021-11-25) Maliwal, Deepika; Pissurlenkar, Raghuvir R. S.; Telvekar, Vikas
Diabetes is a major health issue that half a billion people affected worldwide. It is a serious, long-term medical condition majorly impacting the lives and well-being of individuals, families, and societies at large. It is amongst the top 10 diseases responsible for the death amongst adults with an expected rise to 10.2% (578 million) by 2030 and 10.9% (700 million) by 2045. The carbohydrates absorbed into the body are hydrolyzed by pancreatic α-amylase and other enzymes, human α-glucosidase. The α-amylase and α-glucosidase are validated therapeutic targets in the treatment of Type II diabetes (T2DM) as they play a vital role in modulating the blood glucose post meal. Herein, we report novel and diverse molecules as potential candidates, with predicted affinity for α-amylase and α-glucosidase. These molecules have been identified via hierarchical multistep docking of small molecules database with the estimated binding free energies. A Glide XP Score cutoff −8.00 kcal/mol was implemented to filter out non potential molecules. Four molecules viz. amb22034702, amb18105639, amb17153304, and amb9760832 have been identified after an exhaustive computational study involving, evaluation of binding interactions and assessment of the pharmacokinetics and toxicity profiles. The in-depth analysis of protein– ligand interactions was performed using a 100ns molecular dynamics (MD) simulation to establish the dynamic stability. Furthermore MM-GBSA based binding free energies were computed for 1000 trajectory snapshots to ascertain the strong binding affinity of these molecules for α-amylase and αglucosidase. The identified molecules can be considered as promising candidates for further drug development through necessary experimental assessments.
Thermal kinetics, thermodynamics, decomposition mechanism, and thermal safety performance of typical ammonium perchlorate-based molecular perovskite energetic materials
(Canadian Science Publishing, 2021-11-09) An, Erhai; Chen, Shaoli; Li, Xiaoxia; Hu, Lishuang; Tan, Yingxin; Cao, Xiong; Deng, Peng
In this work, we reported that the thermal kinetics, thermodynamics, and decomposition mechanism of AP-based molecular perovskite energetic materials were studied, and their thermal safety performance was estimated. Typical AP-based molecular perovskite energetic materials (H2dabco)[NH4(ClO4)3] (DAP-4), (H2pz)[NH4(ClO4)3](PAP-4),(H2mpz)[NH4(ClO4)3](PAP-M4), and (H2hpz)[NH4(ClO4)3] (PAP-H4) were synthesized and characterized. These were studied by differential scanning calorimetry (DSC). The results show all of the obtained AP-based molecular perovskite energetic materials have higher thermal decomposition temperatures, and the peak temperatures are more than 360 C. And all follow the random nucleation and growth model.Other thermodynamic parameters, such as reaction enthalpy (ΔH), entropy change (ΔS), and free energy (ΔG) show that they are generally thermodynamically stable. Moreover, their adiabatic induced temperatures were obtained, TD24 of DAP-4, PAP-4, PAP-M4, and PAP-H4 are 246.6, 201.2, 194.5, and 217.5C, respectively. The work offered an important and in-depth understanding for the thermal decomposition characteristics of AP-based molecular perovskite energetic materials and their potential applications.
Synthesis of a polyphenylacetylene/silica nanotube composite under high-temperature, high-pressure conditions
(Canadian Science Publishing, 2021-09-27) Fabbiani, Marco; Rouquette, Jrme; Talbi, Gal; Cambon, Martine; Cambon, Olivier; Santoro, Mario; Konczewicz, Leszek; Contreras, Sylvie; Haines, Julien
Phenylacetylene was inserted and polymerized in 5 nm diameter silica nanotubes under high pressure – high temperature conditions of 0.5 GPa and 437 K in an inert gas. The resulting nanocomposite was characterized by infrared and Raman spectroscopy and scanning and transmission electron microscopy. The vibrational spectroscopic data confirmed the formation of π-conjugated polyphenylacetylene and the absence of crystallization of the amorphous nanotubes. Scanning transmission electron microscopy coupled with energy dispersive x-ray spectroscopy, STEM-EDX, measurements confirmed the insertion of the polymer in the channels of the nanotubes and electron diffraction confirmed the amorphous nature of both the polymer and the host SiO2 nanotubes. The obtained nanocomposite is a candidate material for gas sensing applications. Du phnylactylne a t insr puis polymris dans des nanotubes de silice de diamtre 5nm dans de conditions de haute pression 0,5 GPa et haute temprature 437K. Le nanocomposite obtenu a t caractris par spectroscopies infrarouge et Raman et par microscopies lectronique balayage et en transmission. Les donnes de spectroscopie vibrationnelle ont confirm la formation de polyphnylactylne π-conjugu ainsi que l’absence de cristallisation des nanotubes amorphes. La microscopie lectronique en transmission balayage, couple la spectroscopie des rayons X en dispersion d’nergie a confirm l’insertion du polymre l’intrieur des canaux des nanotubes. La diffraction lectronique a confirm la nature amorphe du polymre et des nanotubes de SiO2 hte. Le nanocomposite est un candidat comme matriau pour les capteurs de gaz.
Beyond Exploding Balloons – Bringing the Science of Chemistry to the Public
(Canadian Science Publishing, 2021-11-29) Farrell, Jacqueline; Wahba, Alexander S
This paper is a personal account of the inception and work of the award-winning McGill Chemistry Outreach Group by two of its founding members. This team of graduate students, staff and faculty helps promote science literacy, curiosity and critical thinking, while making chemistry accessible to the public. The McGill Chemistry Outreach Group also serves as a good example of how to prepare students and staff in communicating chemistry to the public through formal training. In doing so, outreach is beginning to be defined not only in terms of its obvious impact on members of the public, but also as an explicit part of a student’s professional training.
Thermal transitions in metastable Cu – 68.5 at. % Co alloy.
(Canadian Science Publishing, 2021-11-09) Jegede, Oluwatoyin Enitan; Haque, Nafisul; Mullis, Andrew M.; Cochrane, Robert F.
Arc melted and drop tube processed Cu – 68.5 at. % Co alloy has been subjected to differential thermal analysis (DTA). The liquidus temperature determined from the DTA curves in the arc melt sample (1664 K) was found to be close to phase diagram estimate of 1662 K. In contrast as a result of liquid phase separation in the drop tube samples, the values obtained in the powders were much lower mainly because the compositions of the demixed phases vary from that of the parent melt. The liquidus temperature of the 850 + μm powders was 1632 K while that of the
Parallel or Interconnected Pores’ Formation through Etchant Selective Silicon Porosification
(Canadian Science Publishing, 2021-10-14) Rani, Chanchal; Tanwar, Manushree; Ghosh, Tanushree; Kandpal, Suchita; Pathak, Devesh K.; Maximov, Maxim Yu.; Kumar, Rajesh
Effect of oxidizer, present in the etching solution, on the surface morphology and microstructure obtained after porosification of p-type silicon wafer using metal assisted chemical etching has been studied here. The morphologies of Si wafers porosified using two different solutions namely HF/ H2O2 and HF/KMnO4 have been compared to establish how either of the oxidizers (H2O2 or KMnO4) should be chosen depending on the desired application. The comparative study reveals that either parallel pores with wire like structures or interconnected pores with cheese like structures can be obtained when H2O2 or KMnO4 respectively are chosen. Careful analysis of SEM images has been carried out using ImageJ to establish that samples prepared using KMnO4 are more porous due to aggressive etching. Additionally, experimental and theoretical Raman spectroscopic studies have been utilized to study the presence of low dimensional Si nanostructures of a few nanomaters size at the microscopic level in the porosified silicon.
A novel fluorometric chemosensor based on imidazo[4,5-b]phenazine-2-thione for ultrasensitive detection and separation of Hg2+ in aqueous solution
(Canadian Science Publishing, 2021-10-27) Huang, Qing; Li, Qiao; Zhang, Hai-Li; Zhu, Wei; Qu, Wen-Juan; Lin, Qi; Yao, Hong; Zhang, You-Ming; Wei, Tai-Bao
We synthesize and develop 1,3-dihydro-2H-imidazo[4,5-b]phenazine-2-thione as a ratiometric chemosensor for recognition of Hg
Non-Fickian diffusion in viscous aerosol particles
(Canadian Science Publishing, 2021-11-16) Preston, Thomas
Slow condensed phase diffusion in organic aerosol particles can impede many chemical and physical processes associated with atmospheric aerosol (e.g. gas-particle equilibrium partitioning). The characteristic times associated with these high viscosity particles are typically modelled using a concentration-dependent diffusivity within a purely Fickian framework. In that model, the medium in which diffusion is taking place is treated as being inviscid as far as mass transport is concerned. In this report, we investigate the validity of assuming that the viscosity is equal to zero by using a transport model that includes viscous pressure gradients. It is found that the effect of viscosity is negligible for particles with radii that are larger than 100 nm but, below that radius, it can delay water uptake and loss by orders of magnitude for physically realistic viscosities. However, if the Stokes-Einstein relation is obeyed then, even for nanosized particles, viscosity can be ignored. In addition to numerical calculations, a dimensionless Deborah number is defined that indicates the significance of Fickian diffusion compared to the rheological response during water transport.
Surface Enhanced Infrared Spectroelectrochemistry using a Microband Electrode
(Canadian Science Publishing, 2021-10-20) Morhart, Tyler A.; Tu, Kaiyang; Read, Stuart; Rosendahl, Scott M; Wells, Garth; Achenbach, Sven; Burgess, Ian J
The successful use of a microband electrode printed on a silicon internal reflection element to perform time resolved infrared spectroscopy is described. Decreasing the critical dimension of the microband electrode to several hundred micrometers provides a sub-microsecond time constant in a Kretschmann configured spectroelectrochemical cell. The high brilliance of synchrotron sourced infrared radiation has been combined with a specially designed horizontal attenuated total reflectance (ATR) microscope to focus the infrared beam on the microband electrode. The first use of a sub-microsecond time constant working electrode for ATR surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) is reported. Measurements show that the advantage afforded by the high brilliance of the synchrotron source is at least partially offset by increased noise from the experimental floor. The test system was the potential induced desorption of an adsorbed monolayer of 4-methoxypyridine as measured using step-scan interferometry. Based on diffusion considerations alone, the expected time scale of the process was less than 10 microseconds but was experimentally measured to be three orders of magnitude slower. A defect-mediated dissolution of the condensed film is speculated to be the underlying cause of the unexpected slow kinetics.
Ultra-fast Cu-based A3-coupling catalysts: faceted Cu2O microcrystals as efficient catalyst-delivery systems in batch and flow conditions
(Canadian Science Publishing, 2021-09-26) Bao, Huizhi; Li, Alain Y.; Kairouz, Vanessa; Moores, Audrey
Cu(I) catalysts were studied for the synthesis of a propargylamine via A3-coupling of aldehyde, amine, and alkyne, under solvent-free and low loading conditions, using batch microwave or flow thermal heating. We explore ultra-low loading conditions with Cu(I) salts as ultra fast and active catalysts featuring TOFs above 105 h-1. Well-defined octahedral and cubic Cu2O microcrystals were also successfully applied and compared to this reaction. Both types of microcrystals exhibited excellent catalytic activities within minutes, via in-situ generation of low dose of Cu(I) ions within the reaction medium, to achieve TON beyond 2000 and recycling up to 10 times in a flow reactor. The study of the catalytic system demonstrated that the activity was surface-structure dependent and allowed for the design of low Cu contamination A3-coupling systems, affording a product at the decigram scale, with Cu contamination below FDA recommendations for drug synthesis, without the need for a purification procedure.
Following the thread: Mytilus mussel byssus as an inspired multi-functional biomaterial
(Canadian Science Publishing, 2021-09-27) Waite, J. Herbert; Harrington, Matthew James
Over the last 15 years, the byssus of marine mussels (Mytilus spp.) has emerged as an important model system for the bio-inspired development and synthesis of advanced polymers and adhesives. But how did these seemingly inconsequential fibers that are routinely discarded in mussel hors d’oeuvres become the focus of intense international research. In the present review, we take a historical perspective to understand this phenomenon. Our purpose is not to review the sizeable literature of mussel-inspired materials as there are numerous excellent reviews that cover this topic in great depth. Instead, we explore how the byssus became a magnet for bio-inspired materials science, with a focus on the specific breakthroughs in the understanding of composition, structure, function and formation of the byssus achieved through fundamental scientific investigation. Extracted principles have led to bio-inspired design of novel materials with both biomedical and technical applications, including surgical adhesives, self-healing polymers, tunable hydrogels and even actuated composites. Continued study into the byssus of Mytilid mussels and other species will provide a rich source of inspiration for years to come.
Generation of ultrafast, transient, highly acidic pH spikes in the radiolysis of water at very high dose rates. Relevance for FLASH radiotherapy.
(Canadian Science Publishing, 2021-10-09) Sultana, Abida; Alanazi, Ahmed; Meesungnoen, Jintana; Jay-Gerin, Jean-Paul
Monte Carlo multi-track chemistry simulations were carried out to study the effects of high dose rates on the transient yields of hydronium ions (H3O
Stoichiomorphic Halogen-Bonded Cocrystals. A Case Study of 1,4-Diiodotetrafluorobenzene and 3-Nitropyridine
(Canadian Science Publishing, 2021-09-20) Hajjar, Christelle; Nag, Tamali; Al Sayed, Hashim; Ovens, Jeffrey S.; Bryce, David L.
The concept of variable stoichiometry cocrystallization is explored in halogen-bonded systems. Three novel cocrystals of 1,4-diiodotetrafluorobenzene and 3-nitropyridine with molar ratios of 1:1, 2:1, and 1:2, respectively, are prepared by slow evaporation methods. Single-crystal X-ray diffraction analysis reveals key differences between each of the nominally similar cocrystals. For instance, the 1:1 cocrystal crystallizes in the P21/n space group and features a single chemically and crystallographically unique halogen bond between iodine and the pyridyl nitrogen. The 2:1 cocrystal crystallizes in the P1- space group and features a halogen bond between iodine and one of the nitro oxygens in addition to an iodine-nitrogen halogen bond. The 1:2 cocrystal crystallizes with a large unit cell (V = 9896 3) in the Cc space group and features 10 crystallographically distinct iodine-nitrogen halogen bonds. Powder X-ray diffraction experiments carried out on the 1:1 and 2:1 cocrystals confirm that gentle grinding does not alter the crystal forms. 1H → 13C and 19F → 13C cross-polarization magic angle spinning (CP/MAS) NMR experiments performed on powdered samples of the 1:1 and 2:1 cocrystals are used as spectral editing tools to select for either the halogen bond acceptor or donor, respectively. Carbon-13 chemical shifts in the cocrystals are shown to change only very subtly relative to pure solid 1,4-diiodotetrafluorobenzene, but the shift of the carbon directly bonded to iodine nevertheless increases, consistent with halogen bond formation (e.g., a shift of +1.6 ppm for the 2:1 cocrystal). This work contributes new examples to the field of variable stoichiometry cocrystal engineering with halogen bonds.
Defects and Impurities in Colloidal Ga2O3 Nanocrystals: New Opportunities for Photonics and Lighting
(Canadian Science Publishing, 2021-09-12) Nguyen, Khue; Radovanovic, Pavle V
Defects, both native and extrinsic, critically determine functional properties of metal oxides. Gallium oxide has recently gained significant attention for its promise in microelectronics, owing to the unique combination of conductivity and high breakdown voltage, and solid-state lighting, owing to the strong photoluminescence in the visible spectral region. These properties are associated with the presence of native defects that can form both donor and acceptor states in Ga2O3. Recently, Ga2O3 nanocrystal synthesis in solution and optical glasses has been developed, allowing for a range of new applications in photonics, lighting, and photocatalysis. This review focuses on the structure and properties of Ga2O3 nanocrystals with a particular emphasis on the electronic structure and interaction of defects in reduced dimensions and their role in the observed photoluminescence properties. In addition to native defects, the effect of selected external impurities, including lanthanide and aliovalent dopants, and alloying, on the emission properties of Ga2O3 nanocrystals are also discussed.
Efficient One-pot Synthesis of 4 Hydroxy-2H Chromene by heterogeneously catalyzed ZnO NP and mesoporous aluminosilicate catalysts in solvent free condition.
(Canadian Science Publishing, 2021-07-27) Mahato, Birendra Nath; T., Krithiga; Yogalakshmi, G.; Kumar, Aravind
4Hydroxy-2H Chromenes are fused benzopyran rings, an important class of biologically active compounds, widely used as antibacterial, antiviral, antitumor, and anticancer agents. In this present paper, we report the 4 Hydroxy-2H Chromenes synthesis by using two catalysts namely, (i) ZnO nanoparticles and (ii) mesoporous ZnO/AlSBA-15 (7) catalysts. The ZnO NP catalyst was prepared by using leaf extract while ZnO/AlSBA-15(7) catalysts were prepared by the wet chemical route. All catalysts were characterized by XRD, SEM, EDS, FTIR, and N2 sorption techniques. The catalytic activity of the synthesized catalyst was evaluated in the one-pot reaction using aromatic aldehyde and Coumarin, and found to be maximum yield of 81% at temperature 80C, a catalyst dose of 10 mmol %, in time limit of 4h.
Recent development in metal-doped SBA-15 catalyst for heterogeneous catalysis and sustainable chemistry: a mini-review
(Canadian Science Publishing, 2021-09-16) Mahato, Birendra Nath; T., Krithiga
For the invention of new advanced sustainable materials for heterogeneous catalysis require control of structural parameter of active sites. Mesoporous silica, especially SBA-15 has some unique and important features such as highly ordered mesopore, greater hydrothermal stability, greater wall thickness, large surface area, and adjustable pore volume. All these properties render it a promising material for catalysis, adsorption, supporting material, biomedical application, and environmental remediation. However, purely SBA-15 lacks acidic characters, which hinder its catalysis capabilities. Therefore, functionalized SBA-15 improves the catalytic activities for versatile applications. Thus, in this paper, we attempted to summarize the synthesis procedures, various functionalization processes, and application of metal modified SBA-15 in organic synthesis, fine chemical synthesis, photocatalysis, and decontamination of water. Furthermore, physicochemical properties, sustainability, and efficacies are discussed in detail for future reference and scope of studies.

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