Abstracts are ordered alphabetically by first author surname.
Tanzeel Arif1, Chris Bumby1
1Robinson Research Institute, Victoria University of Wellington
Substantial deposits of titanomagnetite ironsand are found throughout the west coast of the North Island of New Zealand (NZ). NZ ironsand is an unusual iron ore as it contains approximately 8% TiO2 by mass, which prevents its use as a feedstock for conventional blast furnace (BF) processes. Instead, direct reduced iron (DRI) is produced from NZ ironsand via a solid-state carbo-thermic reduction process which utilises coal as both the reductant and thermal fuel. This process is the second largest source of industrial CO2 emissions in New Zealand.
There is substantial global interest in alternative iron-making processes which can reduce the greenhouse gas footprint of the steel manufacturing industry. One such approach is the electro-winning of iron using electricity generated from renewable sources.1 New Zealand is uniquely placed to develop such technology as its electricity generation system comprises >85% renewable sources. Here, we report initial investigative work into the electro-winning of iron from NZ ironsand through electrolytic decomposition of titano-magnetite ore in an aqueous alkaline electrolyte.
Slurries of ironsand powder were formed through suspension in concentrated aqueous sodium hydroxide solution. It was observed that applying a constant current above 100 oC led to the deposition of iron metal at the cathode, whilst oxygen was evolved at the inert platinised titanium anode. Electro-reduction of the titanomagnetite powder is believed to proceed similar to the Fray-Farthing-Chen (FFC) mechanism.2 In order to evaluate the industrial feasibility of this process, we have experimentally measured the current efficiency and cell voltage in an optimised cell configuration, and used these values to calculate the corresponding process energy cost. Moreover, we have also studied the influence of cell operation parameters on the morphology of the resulting iron deposits, and characterised the contaminants present within these electro-deposited films using X-ray diffraction (XRD), ICP-MS and scanning electron microscopy.
1. Allanore, A.; Lavelaine, H.; Valentin, G.; Birat, J. P.; Lapicque, F. J Electrochem. Soc. 2008, 155(9), E125-E129.
2. Chen, G. Z.; Fray, D. J.; Farthing, T. W. Nature, 2000, 407, 361-364.
Irene Marice A. Fernandez1, Luke Liu1
1School of Physical and Chemical Science, Victoria University of Wellington
Hydrogen has been envisioned as an alternative fuel in a future having a carbon-neutral energy cycle. One of the main problems in fully embracing H2 gas as a fuel source is its storage and transport. The present strategies for H2 storage require large amounts of energy, thus affecting its marketability and operational flexibility. Porous materials – such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs) – are considered as one of the solutions because of their adsorbent capabilities. MOFs and COFs are porous crystalline solids connected through coordination and covalent bonds with net-like structures. Large-scale computational screening and numerous experimental studies have shown a positive correlation between surface area and H2 storage capacities. The present record of the MOF having the highest geometric surface area is NU-1501-Al at 5714 m2/g and an H2 deliverable capacity of 14%wt. This study aims to design and synthesise a 3D COF with the same acs topology of NU-1501-Al that has a potential to surpass its surface area and deliverable capacity. Towards this, we design a key monomer featuring trigonal prismatic geometry. This monomer is expected to deliver 3D COFs through imine condensation with readily available ditopic or tritopic monomers. Our synthetic effort towards this key monomer involved a Miyaura borylation followed by a Suzuki coupling. The study summarises several approaches undertaken to tackle the challenges in synthesising the monomer via an intermediate di-tert-butyl(5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,3-phenylene)dicarbamate.
Anton Good1, Aditya Joshi1, Mark Staiger1
1Mechanical Engineering, University of Canterbury
Development of new alloys for experimental purposes can benefit from the use of bespoke manufacturing equipment, with the aim to improve production efficiency. Research materials are generally produced in small batches, while available industrial tooling is designed to work with large throughputs. The use of industrial tooling for research can result in reduced efficiency and increased material wastage.
This work highlights the development and manufacturing of a custom extrusion machine intended for producing feedstock of magnesium alloys for producing screws and plates to be used as orthopaedic implants in humans.
We discuss the limitations imposed by project budgets, timeframes, global logistics and existing infrastructure. Solution paths are identified and discussed, helpful tips to avoid common pitfalls when designing equipment are also explored.
Calum Gordon1, Rose Hogg1, Nathaniel Davis1
1School of Chemical and Physical Sciences, Victoria University of Wellington
The commercialization of luminescent solar concentrators (LSCs) is greatly inhibited by reabsorption events from their light harvesting constituents. Hybrid nanomaterials have been shown to have energy transfer applications, enabling appreciable stokes shift enhanced emission, ideal for mitigating reabsorption events in LSCs. A known non-toxic hybrid nanomaterial system is InP/ZnS quantum dots acting as a donor, with an organic acceptor. The impact of ZnS shell size on energy transfer efficiency and light harvesting ability is investigated in this work with a focus on optimization for LSCs.
Honey Gupta1,2, Steve McNeil2, Steve Ranford2, Mark Staiger1
1Mechanical Engineering, University of Canterbury
2Biopolymer Network Ltd/AgResearch Limited, New Zealand
Biopolymer aerogels are exciting materials as they bring-together two strands of modern materials development. Biopolymers are polymers derived from renewable resources such as plant and animals, are biodegradable and sustainable alternatives to petroleum-derived polymers. Aerogels attract great interest in applications as diverse as aerospace to medicine, due to their unique combination of properties such as high porosity and low density.
Several biopolymers have been studied for their ability to form aerogels including polysaccharides (cellulose, starch, alginate, chitin, pectin etc.) and proteins from milk, eggs and silk. Aerogels are highly adsorbent nanostructured materials giving them potential matrices for controlled release of materials. Hence, aerogels made from biopolymers have great potential as biocompatible matrices for the controlled release of pharmaceuticals, antivirals, antibacterials, antifungals, skin moisturisers and UV absorbers.
The present research concerns the preparation of gelatine-based protein aerogels, their impregnation with a bioactive polyphenolic extract by various green chemistry methods, and the controlled release of the bioactive. The synthesised bio-aerogels were characterised by scanning electron microscopy, N2 adsorption-desorption analysis and FTIR spectroscopy and in-vitro release profiles. The results indicated that novel bio-aerogels can be synthesised with tunable pore sizes giving high surface areas (~150 m2/g). Sustained release of the bioactive was observed which typically had a 10-20% burst release and confirmed to the Kors-Peppas model. These results and the underlying science extend our knowledge, not only in terms of aerogels but also of proteins, for developing sustainable materials to broaden our options towards a greener and sustainable future.
Muhammad Hayat1, Harshpreet Singh1,2, Ying Xu1, Peng Cao1
1Chemical and Materials Engineering, University of Auckland
2NZ Product Accelerator, University of Auckland
The currently available heat-sink materials cannot meet the requirements for the 5G and beyond technology. Copper/diamond composites have been proposed, simply because Cu and diamond are excellent thermal conductors while diamond has a very low coefficient of thermal expansion (CTE). Mixing Cu and diamond to form a composite seems to be a straightforward approach. However this simple approach has never succeeded, because chemically Cu does not wet diamond and therefore the Cu-diamond interface cannot be tightly bonded, leading to an inferior thermal conductivity. This study presents a metal injection moulding (MIM) process for depositing copper submicronic particles onto diamond reinforcements prior to densification by hot pressing. Microstructural study of composites by scanning electron microscopy (SEM) was correlated with X-ray photoelectron spectroscopy (XPS). The initial results have shown that our strategy can lead to successful copper deposition onto diamond particles. This will lead to a well-bonded interface between copper matrix and diamond reinforcement, ultimately resulting in excellent thermal conductivity.
Caixia Hou1, Martin Allen1, Roger Reeves2, Rodrigo Martinez Gazoni2, Liam Carroll2
1Electrical & Computer Engineering, University of Canterbury
2School of Physical and Chemical Sciences, University of Canterbury
Monoclinic beta-phase gallium oxide (β-Ga2O3) is currently the subject of very strong research interest for high-efficiency power electronics and deep UV photodetectors due to its ultra-wide band gap (4.85 eV) and very high breakdown strength (~8 MV/cm). One of the important challenges to unlocking the potential of β-Ga2O3 for power electronics devices, is the production of robust thermally-stable Schottky contacts, as these form the key component in high-speed rectifying diodes and metal-semiconductor field effect transistors. In the work presented here, very high temperature β-Ga2O3 Schottky contacts were fabricated on (21) β-Ga2O3 single crystal substrates using intentionally-oxidized platinum group metal (PGM) Schottky contacts (SCs), i.e. PtOx, IrOx, PdOx, and RuOx, fabricated via the reactive rf sputtering of plain PGM targets using an oxygen-containing plasma. All four types of oxidized PGM SCs showed rectification ratios of at least 10 orders of magnitude at temperatures up to 350 oC, significantly higher than their plain metal counterparts, with reverse leakage current densities (at -3 V) of less than ~ 2x10-8 Acm-2, the measuring limit of the Semiconductor Parameter Analyzer. At temperatures above 350 oC, measurable increases in reverse leakage current were observed, due to increasing thermionic emission over the respective Schottky barriers. However, the PtOx, IrOx, PdOx, RuOx SCs still showed rectification ratios of approximately 7, 6, 5, 4 orders of magnitude at an operating temperature of 500 oC. This remarkable high temperature SC performance is due to the thermal stability of these PGM oxides and their high work functions that increase with increasing oxygen content resulting in effective Schottky barriers in excess of 2.0 eV at 500 oC. These results show that intentionally-oxidized PGM SCs to β-Ga2O3 have significant potential for the fabrication of high temperature β-Ga2O3 rectifying diodes, UV photodetectors, and metal-semiconductor field effect transistors.
Melissa Ishii1, Deborah Munro1
1Mechanical Engineering, University of Canterbury
With technological advancements in rapid prototyping and 3D bioprinting, biocompatible hydrogel materials known as ‘bioinks’ can now be fabricated using these emerging technologies. Traditionally, scaffolds for tissue engineering were produced using moulds which allowed for very little control over the microstructure and overall anatomy. By utilizing additive manufacturing principles, biomaterials and cells can be precisely deposited in a layer-by-layer fashion to produce scaffolds.
Bioprinters have many adjustable parametric settings that affect the printability of a material. However, little is understood about the optimal parameters to print a wide range of these bioinks. Currently, anytime a novel bioink is created there is a process of trial and error that is required in order to determine the optimal printing parameters for the bioprinter and desired application.
Though bioprinters are a very useful tool for many researchers, the usage is limited due to the discovery process required to optimise the printing parameters for each new material. If an established method existed to determine optimal printing parameters, this would make the technology more accessible for groups who do not study 3D fabrication as part of their research interests. Additionally, more studies could to move from 2D environments to more biologically relevant 3D cultures.
Our research aim is to characterise the relationship between rheological properties and printability of various bioinks. Then, by drawing connections between the material properties and the printing parameters, an established protocol will be developed for a range of materials. The viscoelastic and shear-thinning properties of the hydrogel will be measured using rheological studies pre and post gelation, so the shear and storage moduli can be calculated.
Mahmood Jamil1, Shanghai Wei1,2, John Kennedy3, Mark Philip Taylor1,2
1Chemical & Materials Engineering, University of Auckland
2NZ Product Accelerator, University of Auckland
3National Isotope Centre, GNS Science, New Zealand
Hybrid nanostructured materials address the challenges of low energy and power density, and poor cyclic life of electrochemical energy storage systems. Nanostructured TiO2 is one such promising candidate because of its comparable capacity to graphite electrode (335 vs 372 mAhg-1). Tin (Sn) is a low cost, abundantly available material possessing a theoretical capacity of 994 mAhg-1 and an excellent electrical conductivity (91.7x103/cmΩ). However, the Sn insertion/deinsertion process causes massive volume expansion (~300%), resulting in severe pulverization.
This study focuses on the development of Sn/TiO2 based hybrid nanostructure material that will have advantages of both materials resulting in high electrochemical performance. A two-step electrochemical anodization process was applied to synthesize TiO2 nanotubes. It was found that altering the anodic conditions affected the morphology and arrays of nanotubes. Concurrently, Sn was deposited by ion beam sputtering and heat-treated at 350oC. XRD, SEM, TEM were employed for morphological analysis of Sn/TiO2 and cyclic voltammetry (CV) was applied to evaluate the electrochemical performance. TEM results confirmed the formation of core-shell structure-TiO2 as a core, and Sn as a shell.
Aditya Joshi1, Anton Good1, Bartosz Nowak1, George Dias2, Mark Staiger1
1Mechanical Engineering, University of Canterbury
2Department of Anatomy, University of Otago
Fractures to the skull often require surgical intervention with the insertion of stabilising mini-plates to assist the healing process. Typically, craniomaxillofacial mini-plates are subject to bending to match the contour of the skull, introducing plastic strain to the titanium-based implant material. Typically, the level of stress (or strain) that is generated during surgery is of little concern for the performance of titanium-based implants. However, it is postulated that the degradation rate of biodegradable implants (e.g. magnesium alloys) is increased via stress corrosion under the above conditions. It is demonstrated for the first time that a technique combining laser 3D scanning and finite element analysis can be used to estimate the stress and strain that is introduced in a craniomaxillofacial mini-plate following the implantation procedure. Mechanical testing was also carried out to calibrate an FEA model that captures the yield asymmetry exhibited by a magnesium alloy. The method was validated for its ability to predict the strain within an implant plate with the use of strain gauges directly attached to the mini-plate. The difference between the FEA-predicted strain and experimentally measured strain was less than was less 3 %. The results demonstrate the significant potential of the above technique to estimate the stress and strain in craniomaxillofacial implant plates. The technique is promising for the study (and prediction) of the mechano-corrosion performance of bioresorbable orthopedic implants based on magnesium alloys.
Michael Kammermeier1,2, Daisuke Iizasa3, Makoto Kohda3, Ulrich Zuelicke1, Junsaku Nitta1
1Chemical & Physical Sciences, Victoria University of Wellington
2MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand
3Tohoku University, Japan
In a semiconductor, collective excitations of spin textures usually decay rather fast due to D’yakonov-Perel’ spin relaxation [1]. The latter arises from spin-orbit coupling, which induces wave-vector (k) dependent spin rotations that, in conjunction with random disorder scattering, generate spin decoherence. However, symmetries occurring under certain conditions can prevent the relaxation of particular homogeneous and inhomogeneous spin textures. The inhomogeneous spin texture, referred to as a persistent spin helix, is especially appealing as it enables us to manipulate the spin orientation while retaining a long spin lifetime. Recently, it was predicted that such symmetries can be realized in zinc-blende two-dimensional electron gases if at least two growth-direction Miller indices agree in modulus and the coefficients of the Rashba and k-linear Dresselhaus spin-orbit couplings are suitably matched [2].
In this work [3], we systematically analyze the impact of the symmetry-breaking k-cubic Dresselhaus spin-orbit coupling, which generically coexists in these systems, on the stability of the emerging spin helices with respect to the growth direction. We find that, as an interplay between orientation and strength of the effective magnetic field induced by the k-cubic Dresselhaus terms, the spin relaxation is weakest for a low-symmetry growth direction that can be well approximated by a [225] lattice vector. These quantum wells yield a 30% spin-helix lifetime enhancement compared to [001]-oriented electron gases and, remarkably, require a negligible Rashba coefficient. The rotation axis of the corresponding spin helix is only slightly tilted out of the quantum-well plane. This makes the experimental study of the spin-helix dynamics readily accessible for conventional optical spin orientation measurements where spins are excited and detected along the quantum-well growth direction.
[1] M. I. Dyakonov, V. I. Perel, Sov. Phys. Solid State 13, 3023 (1972).
[2] M. Kammermeier, P. Wenk, and J. Schliemann, Phys. Rev. Lett. 117, 236801 (2016).
[3] D. Iizasa, M. Kohda, U. Zülicke, J, Nitta, M. Kammermeier, Phys. Rev. B 101, 245417 (2020).
Andrew Lange1, Mathieu Sellier1, James Hewett1, Elliot Wainwright2, Tim Weihs2
1Mechanical Engineering, University of Canterbury
2Johns Hopkins University, USA
Combusting metal powders are commonly used as an additive in energetic reactions such as explosives, propellents, or pyrotechnics, and also as a way of countering bio-agents. In observing the combustion of some metal powders the liquid droplets were found to burst apart due to rapid bubble growth in the interior of the droplet in a process termed a "microexplosion". When this occurs, new surfaces of unreacted metal are revealed which improve the properties of the reaction. It is thought that better understanding this process will help to design more optimised powders with greater benefits. Following the work of Wainwright et al. (2019), the bubble growth within these combusting metal droplets has data from experimental recordings compared with solutions from a derived mathematical model.
The model is developed from the Navier-Stokes equations in spherical coordinates and by applying assumptions and substituting expressions of mass continuity is simplified to coupled first order ordinary differential equations. These simplifications allow the equations to be solved using ode45 in MATLAB to obtain a plot of the bubble radius over time.
A number of candidate functions for expressing the molar flow of gas into the bubble are generated for use in the model. The graphs for different functions for molar flow rate are compared to radius data measured from images of bubble growth events from the experiments done by Wainwright et al. (2019) of a combusting aluminium and zirconium alloy powder. Within the limits of uncertainty there is most agreement between the model solution and experimental data when the flow of nitrogen into the bubble is linearly proportional to the bubble radius. This finding has limited agreement with the proposed mechanisms of molar transfer through the droplet as there is still a large amount unknown about properties of high temperature liquid metal alloys.
Thomas Nott1, James Storey1, John Kennedy2
1Engineering, Victoria University of Wellington
2National Isotope Centre, GNS Science, New Zealand
Nanoparticles (NPs) composed of Pb were formed just below the surface of an SiO2 substrate, these were produced by direct ion-beam implantation to deposit the ions with an energy of 20KeV. Theoretical calculations showed the projected range of the ions was 20nm this was confirmed with Rutherford Back-Scattering measurements. Atomic force microscopy showed signs of the NPs on the surface, approximately 10-20nm in size. This was corroborated by TEM measurements which show the formation of NPs below the surface and reaching a depth of 20nm with EDAX being used to show the composition of the implanted NPs. The distribution of the NPs was altered though annealing with the aim being to coalesce the NPs through Oswald ripening to form large, separate NPs.
Bartosz Nowak1, Karolina Nowak2, Kate Reid3
1Mechanical Engineering, University of Canterbury
2St George’s Cancer Care Centre, Christchurch, New Zealand
3Education, Health & Human Development, University of Canterbury
Lymphoedema is a medical condition causing swelling of the soft tissue due to excessive accumulation of lymph fluid. If lymphoedema remains undiagnosed and untreated, it can lead to severe complications such as tissue fibrosis, restriction of patient’s motion, and eventually immobility.
Mechanics of Materials offers a wide range of material models that can be adapted to predict the behaviour of both the normal tissue as well as the lymphoedematous tissue. Among many, there are single and two-phase models, including Terzaghi’s and Biot’s material models.
This work presents a review of some selected mechanical material models suitable to model the behaviour of soft tissue. Also, it discusses the potential of diagnosing lymphoedema based on measuring some selected mechanical properties of the soft tissue under clinical conditions.
The current state-of-the-art in lymphoedema diagnosis and treatment shows that its early detection, when its treatment is the most effective, is of utmost importance. Additionally, there is a need for a reliable, simple and non-invasive method which could deliver quantitative measures of the tissue state.
It is envisioned that the synergy of mechanics of materials and the current knowledge on lymphoedema can produce a bench-to-bedside solution improving the life of lymphoedema patients.
Siddarth Raajasekar1, Steven Gieseg1
1School of Biological Sciences, University of Canterbury
Cardio vascular disease (CVD) remains as one of the leading causes of death in OECD countries, despite much advancement in the field of medicine including various therapies and surgical procedures. This is in part because the disease is asymptomatic with no clinical warning occurring until there is a clinical event such as stroke or a heart attack.
CVD is a chronic inflammatory disease which occurs within the walls of the artery. Clinically the pathology is described as atherosclerosis, where there is narrowing and hardening of the artery wall. The inflammatory activity is primary driven by macrophages within the artery wall. The macrophages appear to be responsible for most of the pathology causing the growth in the artery wall thickness. Monocytes, the precursor of macrophage, are recruited in to the arterial wall during the initial stages of the disease often described as an atherosclerotic lesions or fatty streak.
This research is focussed on the process of the inflammation in the progression of atherosclerotic plaques and the effect of the macrophage antioxidant 7,8-dihydroneopterin, has on inflammation. The stability of 7,8-NP within the cells and its oxidation pathways has also been characterised in this research.
Jackson Roberts1, Steven Marsh1, Juergen Meyer2, Alicia Moggre3
1School of Physical and Chemical Sciences, University of Canterbury
2University of Washington, USA
3Canterbury District Health Board, New Zealand
Introduction: New Zealand sees 20,000 new cancer registrations every year. Approximately half of these patients are treated using radiation therapy. Safe and effective radiotherapy requires measuring the energy (dose) prescribed and delivered to the patient. Established measurement techniques perturb the radiation beam, or do not measure dose directly in water, adding to the uncertainty of cancer treatments. Optical Calorimetry (OC) is an interferometry-based technique that provides a direct measurement of absorbed dose to water by measuring refractive index changes induced by radiation.
Methods: A radiation dosimeter using the principles of OC was designed in optical modelling software. Traditional image quality instruments, fencepost and contrast phantoms, were utilized to investigate noise reduction techniques and to test the spatial and dose resolution of the system. Absolute dose uncertainty was assessed by measurements in a 6 MV flattening filter free (FFF) photon beam. The dosimeter was improved by isolating the system from external vibrations and controlling the system’s internal temperature. Mathematical noise reduction techniques were also applied.
Results: Optical modelling software predicted that these improvements should increase the spatial resolution from 12 to 35 lp/mm and resolve a minimum dose difference of ±0.2 Gy, these predictions were confirmed experimentally. In the FFF beam the absolute dose uncertainty was dose rate dependent and decreased from ±0.8 to ±0.2 Gy for dose rates of 0.2 and 6 Gy/s, respectively.
Conclusion: A radiation dosimeter utilizing the principles of optical calorimetry has been constructed. Water has been probed directly to determine absorbed dose. Optical modelling software and image quality phantoms have allowed for refinement resulting in a prototype system capable of measuring absorbed dose to water in a 6 MV FFF beam. Reduced uncertainty at higher dose rates indicates the potential for OC as a dosimetry system for cutting-edge radiotherapy techniques such as microbeam and FLASH radiotherapy.
Shailendra Kumar Sharma1, Vladimir Golovko1, Aaron Marshall2
1School of Physical and Chemical Sciences, University of Canterbury
2Chemical & Process Engineering, University of Canterbury
The rising atmospheric CO2 concentration is the major cause of facilitating global warming already causing major catastrophic climate-driven events on Earth. Recently, atomically precise metal clusters have attracted increasing interest in the research field of catalysis due to their unique size-dependent electronic and chemical properties [1]. For the robust application and reusability of catalysts, the metal clusters are deposited on a support. A binder is added to glue the supported catalyst before casting in the form of a catalytic layer. Binder remains in the secondary/outer coordination sphere of the supported catalyst, thus, may influence the catalytic activity.
Here we have studied the role of Nafion binder in the electrochemical reduction of CO2 on [Au9(PPh3)8](NO3)3 clusters (Au9) deposited on Vulcan carbon. [Au9(PPh3)8](NO3) were chemically synthesized, characterized, and deposited on Vulcan carbon. The electrocatalytic cathode prepared by spraying Au9/C along with Nafion served as a cathode for electrochemical CO2 reduction. A potentiostatic electrochemical reduction was carried out, and gaseous and liquid products were studied using gas chromatography and highperformance liquid chromatography, respectively. The effect of the amount of Nafion in the catalytic layer and the role of solvent used in fabrication of the catalytic layer on the catalytic performance were studied. UV-vis spectroscopy was used to investigate the interactions between Nafion and the Au9 clusters. The best performing electrocatalytic layer was fabricated by spraying a Vulcan carbon layer first, then making it electrocatalytically active by drop-casting Au9 clusters. The highest observed selectivity CO2 of conversion to CO (80%) with the reasonably high current (5 mA/cm2)) was achieved at -1.3 V vs. Ag|AgCl. Effects of electrocatalytic activation of electrodes prepared in this study was also investigated.
1. Jin R. , et al., Atomically precise colloidal metal nanoclusters and nanoparticles: Fundamentals and opportunities. Chemical Reviews, 2016. 116(18): p. 10346-10413.
Alibe Wasa1, Rukmini Gorthy2, Johann Land2, Susan Krumdieck2, Catherine Bishop2, William Godsoe3, Jack Heinemann1
1Biological Sciences, University of Canterbury
2Mechanical Engineering, University of Canterbury
3BioProtection Research Centre, Lincoln University
Contaminated surfaces are a major vehicle for the spread of infectious diseases. A strategy to prevent the spread of the organisms causing these infections is through making these surfaces antimicrobial. Photo-activated titania (TiO2) is an antimicrobial agent with self-cleaning properties and could be used to coat door handles and similar surfaces. This coating can reduce viability, spread and colonization of the surface by pathogens. Nanostructured anatase rutile and carbon (NsARC), a TiO2 formulation was tested for antimicrobial (AMA) and antibiofilm (ABA) activity under a variety of light wavelengths and intensities (high intensity visible, UV and ambient light). There was a significant reduction in survival of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Saccharomyces cerevisiae on NsARC coated coupons than on uncoated coupons.
An important materials advancement is AMA of NsARC in the dark. To investigate the role of the co-deposited carbon in AMA of the composite coatings, a set of NsARC coating were heat-treated in air to remove the co-deposited amorphous carbon. There was a marginal increase in performance upon the heat-treatment.
To determine if exposure of microbes to NsARC could induce some form of adaptive resistance to antibiotics, two reporter strains of E. coli was used, each having a plasmid with a reporter gene construct that expressed the mScarlet fluorescent protein (FP) under the control of the promoters of the tolC and soxS genes associated with adaptive resistance. These designed constructs are strains that “report” when the expression of tolC and soxS changes. Reporter strains that were on NsARC exhibited significant increase in expression of the two genes than the ones that were on stainless steel indicating that NsARC can prevent the spread of infections and may also induce genes associated with adaptive resistance to antibiotics.
Kate Wislang1, Rodrigo Martinez Gazoni1
1School of Physical and Chemical Sciences, University of Canterbury
Transparent and conductive SnO2 films were produced using sol-gel, an inexpensive room temperature technique with high throughput that can be used on the industrial scale. The films were tuned over a series of growths and their structural, optical, and electrical properties were investigated using multiple techniques. The films were optimised by investigating different deposition speeds and polymerisation in the solution to produced improved structural properties. Through this process, the density of cracks in the surface of the films was drastically reduced for all deposition speeds used, which led to developing multi-layered films. Continuous layered films were produced successfully to increase the thickness. The electrical properties of the films produced were tuned over two orders of magnitude by Sb-doping, without any noticeable reduction of the transparency for dopant levels up to 2% in the solution. Burstein-Moss shifts were observed for the band gaps of films doped beyond 0.005%, consistent with the presence of degenerate states and the filling of the conduction band. For higher doping levels the structure of the film was destroyed, causing discontinuous films not suitable for optical or electrical applications. All of the films produced had been amorphous. The amorphous films were heated to temperatures higher than the annealing temperature, 450 °C. At 700 °C hints of polycrystallinity could be seen. The transition from amorphous to polycrystalline films was relatively fast and all the changes occurred within the first hour of the films being heated at each temperature. At a temperature of 800 °C polycrystalline films were formed. Although by making the films polycrystalline the electrical properties of the films were significantly reduced. The developed procedure to produce these films was able to be tuned to generate films that exhibit certain structural, optical and electronic properties.
Tao Xu1, Luke Liu1
1School of Chemical and Physical Sciences, Victoria University of Wellington
Covalent Organic Frameworks (COFs) are theoretically the most porous materials. However, their porosity potentials have not been demonstrated due to the dense packing of 2D framework sheets, or entangled growth of 3D networks. Here we design 3D COF monomers with geometries that resemble inorganic clusters. These monomers are expected to produce COFs with record-breaking porosities and gas storage capacities, as predicted by our preliminary theoretical calculation and
computational simulation. COFs with colossal porosities will benefit carbon-neutral society through advancing technologies for natural gas- and hydrogen-powered vehicles with longer driving range, and creating better CO2 capture materials for emission control.
Tingxuan Yang1, Peng Cao1
1Chemical and Materials Engineering, University of Auckland
Phosphor-converted white light-emitting diodes (pc-WLEDs) are an essential solid-state lighting technology for general illumination and outdoor applications. The excellent phosphors, core component of pc-WLEDs, should meet the following three requirements simultaneously: (1) high quantum efficiency (QE); (2) stable photoluminescence (PL) intensity at elevated temperatures; (3) narrow band emission spectra. However, the high performance blue phosphors with these three traits is still ongoing.
Solid solution substitution method has been widely adopted to tailor the local environment of activators through host structure modification. In this work, we successfully synthesized K2SrBa(PO4)2:xEu2+ (KSBP:Eu2+) phosphor with a FWHM of 37 nm (2088 cm-1) and 0.93 high color purity, has shown excellent thermal intensity property and high quantum efficiency. Both experiments and DFT calculation models indicate the doped Eu2+ cation occupy the doped Eu2+ cation occupy the Sr/Ba shared sites, where the similar lattice environments and compacted polyhedral network ensure the narrow band of the photoluminescence spectra. Moreover, this KSBP:xEu2+ displayed outstanding enhancement of internal quantum efficiency (IQE) internal (96%@0.01 Eu2+). Besides, KSBP:Eu2+ phosphors demonstrated excellent thermal stability that they retained 100% integral intensity at 200 °C. The KSBP:Eu2+ phosphors have the potential to be applied in the high-power white light emitting diodes (WLEDs) and backlight display fields.
Ting Zhang1, Wei Gao1
1Chemical and Materials Engineering, University of Auckland
Application of cocatalyst has attracted significant attention in recent years. In this paper, Ag and Co3O4 nanoparticles have been used to decorated on black TiO2 nanotube array. After electrochemical doping Ag and drop cast doping Co3O4, Ag@Co3O4@TiO2-x exhibits a superior degradation efficiency of methylene blue aqueous solution under visible light irradiation. The efficiency is up to 87%, and around 1.5 times higher than that of pure TiO2 nanotube arrays. The improved photocatalyst properties attribute to the surface plasmon resonance properties of Ag nanoparticles and the well separation of electrons and holes after irradiation under visible light. Tube structures provide fast electron transfer channel, which makes electrons transfer fast to react with organic pollution. This nanocomposite can effectively increase photocurrent under irradiation of visible light and improve the photocatalyst efficiency of TiO2 nanotube.