Chemistry, Department of

Transparent conductive oxides (TCOs) serve a critical function in many devices, such as organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). To optimize the performances of these devices, it is desirable to tune the interface between the TCO and the next functional layer of these devices. Self-assembled monolayers prepared from phosphonic acids and silanes are commonly used to tune the properties and performance of this interface, including its surface energy, work function, and durability. Here, we report a new form of self-assembled monolayers for modifying indium tin oxide (ITO), a standard TCO used in OLEDs and OPVs. The ITO surfaces were modified with a series of distinct alcohol reagents. Stabilities of these alcohol-based monolayers were compared with modifications derived from silanes and phosphonic acids, which are commonly used in the literature and industrial processes. Work functions and surface energies of these modified substrates were determined using ultraviolet photoelectron spectroscopy and contact angle measurements. Stability of these monolayers was assessed using cyclic voltammetry, X-ray photoelectron spectroscopy, and transmission spectroscopy techniques. On the basis of the results of these studies, alcohol-based monolayers are promising candidates to modify ITO substrates for use in OLEDs and OPVs.

The incorporation of catalytic nanocrystals into macroporous support materials has been very attractive due to their increased catalyst mass activity. This increase in catalytic efficiency is attributed in part to the increased surface area to volume ratio of the catalysts and the use of complementary support materials that can enhance their catalytic activity and stability. A uniform and tunable coating of nanocrystals on porous matrices can be difficult to achieve with some techniques such as electrodeposition. More sophisticated techniques for preparing uniform nanocrystal coatings include atomic layer deposition, but it can be difficult to reproduce these processes at commercial scales required for preparing catalyst materials. In this study, catalytic nanocrystals supported on three dimensional (3D) porous structures were prepared. The demonstrated technique utilized scalable approaches for achieving a uniform surface coverage of catalysts through the use of polymeric sacrificial templates. This template assisted technique was demonstrated with a good control over the surface coverage of catalysts, support material composition, and porosities of the support material. A series of regular porous supports were each prepared with a uniform coating of nanocrystals, such as NaYF4 nanocrystals supported by a porous 3D lattice of Ti1−xSixO2, Pt nanocrystals on a 3D porous support of TiO2, Pd nanocrystals on Ni nanobowls, and Pt nanocrystals on 3D assemblies of Au/TiO2 nanobowls. The template assisted preparation of high surface area macroporous supports could be further utilized for optimizing the use of catalytic materials in chemical, electrochemical, and photochemical reactions through increasing their catalytic efficiency and stability.

We used human gastric epithelial cells (GES-1) line in an ethanol-induced cell damage model to study the protective effect of Veronicastrum axillare and its modulation to NF-κB signal pathway. The goal was to probe the molecular mechanism of V. axillare decoction in the prevention of gastric ulcer and therefore provide guidance in the clinical application of V. axillare on treating injuries from chronic nephritis, pleural effusion, gastric ulcer, and other ailments. The effects of V. axillare-loaded serums on cell viability were detected by MTT assays. Enzyme-linked immunosorbent assay (ELISA) and Real-Time PCR methods were used to analyze the protein and mRNA expression of TNF-α, NF-κB, IκBα, and IKKβ. The results showed that V. axillare-loaded serum partially reversed the damaging effects of ethanol and NF-κB activator (phorbol-12-myristate-13-acetate: PMA) and increased cell viability. The protein and mRNA expressions of TNF-α, NF-κB, IκBα, and IKKβ were significantly upregulated by ethanol and PMA while they were downregulated by V. axillare-loaded serum. In summary, V. axillare-loaded serum has significantly protective effect on GES-1 against ethanol-induced injury. The protective effect was likely linked to downregulation of TNF-α based NF-κB signal pathway.

A photonic crystal film (PCF) which consists of a porous layered structure with a highly ordered periodic arrangement of nanopores has been used to differentiate between various mixtures of water and ethanol (EtOH). The refractive index difference between the wall (silica) of the empty nanopore and air which occupies it results in the structural color of the PCF. This color disappears when the nanopores are infiltrated by a liquid with a similar refractive index to silica (or silicon dioxide). The disappearance of the structural color provides a means to construct a colorimetric sensor to differentiate between various water/EtOH mixtures based on their wettability of the nanopores in the PCF. In this study, an array of silica-based PCFs was synthesized on a silicon substrate with a precise control of nanopore properties using the co-assembly/sedimentation method. Using this method, we benefitted from having different PCFs on a single substrate. Chemical coatings, neck angles, and film thicknesses on each PCF were the three factors used to adjust the wettability of the pores. Nanopore wetting by water/EtOH mixtures was studied in a systematic manner based on the three factors, and the findings were used to develop a sensor for visual differentiation of various water/EtOH mixtures. The final developed sensor consisting of an array of six PCFs was able to differentiate between seven different water/EtOH mixtures: W10, W20, W30, W40, W50, W60, and W70, in which W10 means 10% of water in EtOH.

The oxygen evolution reaction (OER) is of importance to both electrochemical energy conversion and energy storage. Low-cost, non-precious metal electrocatalysts that can withstand high operational current densities will likely be the best candidates for meeting the commercial needs for a range of OER applications. In addition to electrode composition, the surface morphology of gas evolving electrodes can affect their efficiency and performance. In this work, we demonstrate the influence of electrochemical aging on the performance of micro- and nanoscale textures for the OER. A series of textured Ni electrodes were prepared by rapid, scalable techniques, which included the use of bead-blasting. Two distinct approaches to induce the formation of the active Ni (oxy)hydroxide phase were conducted by electrochemical aging using cyclic voltammetry (CV) methods. The influence of the aging technique was assessed and correlated to the performance of these surface textures. Differences in the morphology of these textures and their resulting surface areas were estimated using three-dimensional (3D) reconstructions obtained from electron microscopy analyses. Focused ion beam (FIB) milling was also performed on the bead-blasted electrodes to visualize buried cracks and voids. The potential required for the OER at an applied current density of 500 mA/cm2 exhibited a reduction of 0.7 V for the electrodes aged by the steady-state treatment. The OER performance of the textured electrodes were found to correlate to both the electrode surface morphology and the type of electrochemical aging applied to the electrodes.

Similar to the advancements gained from big data in genomics, security, internet of things, and e-commerce, the materials workflow could be made more efficient and prolific through advances in streamlining data sources, autonomous materials synthesis, rapid characterization, big data analytics, and self-learning algorithms. In electrochemical materials science, data sets are large, unstructured/heterogeneous, and difficult to process and analyze from a single data channel or platform. Computer-aided materials design together with advances in data mining, machine learning, and predictive analytics are touted to provide inexpensive and accelerated pathways towards tailor-made functionally optimized energy materials. Fundamental research in the field of electrochemical energy materials focuses primarily on complex interfacial phenomena and kinetic electrocatalytic processes. This perspective article critically assesses AI-driven modeling and computational approaches that are currently applied to those objects. An application-driven materials intelligence platform is introduced, and its functionalities are scrutinized considering the development of electrocatalyst materials for CO2 conversion as a use case.

To study the binding mechanism of disparlure (7,8)-epoxy-2-methyloctadecane enantiomers with pheromone-binding proteins (PBPs) of the gypsy moth, oxygen-17 or 18 and 5,5,6,6-deuterium labelled disparlure enantiomers were prepared in an efficient, enantioselective route. Key steps involve the asymmetric α-chlorination of dodecanal by SOMO catalysis and Mitsunobu inversion of a 1, 2-chlorohydrin. The pheromone, (+)-disparlure (7R, 8S), was tested in two infested zones, demonstrating that it is very attractive towards male gypsy moths. Studies of the binding of (+)-disparlure and its antipode to gypsy moth PBPs by 2H &17O NMR at 600 MHz are reported. Chemical shifts, spin-lattice relaxation times and transverse relaxation times  of deuterium atoms of disparlure enantiomers in 2H NMR show that binding of disparlure enantiomers to PBP1 differs from binding to PBP2, as expected from their opposite binding preferences (PBP1 binds (-)-disparlure, and PBP2 binds (+)-disparlure more strongly). Models of the disparlure enantiomers bound to one internal binding site and two external binding sites of both PBPs were constructed. The observed chemical shift changes of deuterated ligand signals, from non-bound to bound, T1 and T2 values are correlated with results from the simulations. Together these results suggest that the disparlure enantiomers adopt distinct conformations within the binding sites of the two PBPs and interact with residues that line the sites.

Clathrate hydrates are icy materials composed of a lattice of water molecules containing well-defined cavities which can accommodate small guest molecules. Their large storage capacity makes clathrates attractive media for a variety of gas storage and separation applications, but there is relatively little information on the chemical stability and diffusion of guest molecules. At the fundamental level inter-cage transition energies have been calculated, but the results need to be tested with experimental data. Ideally this should involve single-atom transport, using an isotopic tracer or spin label. Muonium (Mu = µ+e–) qualifies on both counts. As a single-electron atom with the muon as nucleus it may be considered a light isotope of hydrogen. Furthermore muonium and its reaction products may be monitored by muon spin spectroscopy. In recent years we have used this method to probe H-atom and free radical behaviour in clathrate hydrates. The current work extends studies to benzene and acetone clathrate hydrates. Of note is the simultaneous detection of muonium and muoniated radicals in the same sample. This can happen when Mu is trapped in an empty cavity, remote from its reaction partner. Increase in temperature leads to transport of Mu between cages and results in encounters with reactive guest molecules. By studying the temperature dependence of Mu and radical signals, we have been able to determine the activation energy for transport of Mu between cavities.

The strategic tuning of liquid crystalline phase behaviour by adjusting molecular symmetry was investigated. A family of sixteen symmetrical and unsymmetrical 2,6-di(4’-n-alkoxybenzoyloxy) naphthalene derivatives were prepared and their liquid crystal properties examined by differential scanning calorimetry, polarised optical microscopy, and x-ray diffraction. All mesogens formed nematic phases, with longer-chain analogues also exhibiting smectic C phases at lower temperatures. Melting temperatures of the compounds strongly depend on molecular symmetry, whereas clearing transitions are relatively insensitive to this effect. A detailed analysis indicates that the clearing point can be predicted based on the nature of the terminal alkyl chains, with only a secondary effect from molecular symmetry. Moreover, low symmetry molecules showed a greater tendency to form smectic C phases, which was ascribed to the selective depression of the melting point versus the SmC-N transition. This demonstrates that molecular symmetry-breaking is a valuable tool both for tuning liquid crystalline phase range and for increasing a material’s polymorphism.

Background

Actinium-225 (225Ac, t1/2 = 9.9 d) is a promising candidate radionuclide for use in targeted alpha therapy (TAT), though the currently limited global supply has hindered the development of a suitable Ac-chelating ligand and 225Ac-radiopharmaceuticals towards the clinic. We at TRIUMF have leveraged our Isotope Separation On-Line (ISOL) facility to produce 225Ac and use the resulting radioactivity to screen a number of potential 225Ac-radiopharmaceutical compounds.

Results

MBq quantities of 225Ac and parent radium-225 (225Ra, t1/2 = 14.8 d) were produced and separated using solid phase extraction DGA resin, resulting in a radiochemically pure 225Ac product in > 98% yield and in an amenable form for radiolabeling of ligands and bioconjugates. Of the many polydentate picolinic acid (“pa”) containing ligands evaluated (H4octapa [N4O4], H4CHXoctapa [N4O4], p-NO2-Bn-H4neunpa [N5O4], and H6phospa [N4O4]), all out-performed the current gold standard, DOTA for 225Ac radiolabeling ability at ambient temperature. Moreover, a melanocortin 1 receptor-targeting peptide conjugate, DOTA-modified cyclized α-melanocyte-stimulating hormone (DOTA-CycMSH), was radiolabeled with 225Ac and proof-of-principle biodistribution studies using B16F10 tumour-bearing mice were conducted. At 2 h post-injection, tumour-to-blood ratios of 20.4 ± 3.4 and 4.8 ± 2.4 were obtained for the non-blocking (molar activity [M.A.] > 200 kBq/nmol) and blocking (M.A. = 1.6 kBq/nmol) experiment, respectively.

Conclusion

TRIUMF’s ISOL facility is able to provide 225Ac suitable for preclinical screening of radiopharmaceutical compounds; [225Ac(octapa)]−, [225Ac(CHXoctapa)]−, and [225Ac(DOTA-CycMSH)] may be good candidates for further targeted alpha therapy studies.