Natasha Ross

University of the Western Cape, CHEMISTRY, Faculty Member

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My research niche area is the development sustainable energy storage devices. This is because energy sources and the conservation thereof are growing national concerns. My work involves synthesis and modification of nanostructured Manganese oxides (MnO) which are viable cathode materials to improve the stability and energy storage capacity of Lithium-ion batteries (LIB) for use in demanding applications. Concomitantly I am also involved in developing biosensors for determining the metabolic profile of anti-retroviral drugs in human serum as well as immunosensors for fatal disease biomarkers.
Supervisors: Prof Emmanuel Iwuoha

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Nanostructured Silver-Iron-Functionalized Titanium Dioxide Photo Electrocatalyst for Industrial Effluent Remediation

Environmental chemistry for a sustainable world, 2024

Electrochemical Studies on Novel LiMnPO<sub>4</sub> Coated with Magnesium Oxide-Gold Composite Thin Film in Aqueous Electrolytes

Journal of Nano Research, Nov 1, 2016

. Pristine LiMnPO4 and LiMnPO4/Mg-Au composite cathode materials were synthesized and their elect... more . Pristine LiMnPO4 and LiMnPO4/Mg-Au composite cathode materials were synthesized and their electrochemical properties interrogated using voltammetric, spectroscopic and microscopic techniques. The composite cathode exhibited better reversibility and kinetics than the pristine LiMnPO4. This was demonstrated in the values of the diffusion coefficient (D) and the charge and discharge capacities determined through cyclic voltammetry. For the composite cathode, D = 2.0 x 10-9 cm2/s while the pristine has a D value of 4.81 x 10-10 cm2/s. The charge and discharge capacities of LiMnPO4/Mg-Au at 10 mV/s were 259.9 mAh/g and 157.6 mAh/g, respectively. The corresponding values for pristine LiMnPO4 were 115 mAh/g and 44.75 mAh/g, respectively.. A similar trend was observed in the results obtained from electrochemical impedance spectroscopy measurements. These results indicate that LiMnPO4/Mg-Au composite has better conductivity and will facilitate faster electron transfer and better electrochemical performance than pristine LiMnPO4.

Graphenatedtantalum(IV)oxideandpoly(4-styrenesulphonicacid)-dopedpolyanilinenanocompositeascathodematerialinanelectrochemicalcapacito

Electrochemical Determination of Hydrogen Peroxide by a Nonenzymatic Catalytically Enhanced Silver-Iron (III) Oxide/Polyoxometalate/Reduced Graphene Oxide Modified Glassy Carbon Electrode

Analytical Letters, Apr 20, 2020

The synergism of phosphomolybdic acid hydrate (POM) decorated with silver-iron (III) oxide (Ag-Fe... more The synergism of phosphomolybdic acid hydrate (POM) decorated with silver-iron (III) oxide (Ag-Fe 2 O 3) nanoparticles and anchored on reduced graphene oxide (RGO) have been demonstrated to be effective as a nonenzymatic H 2 O 2 sensor platform. The assembly of the sensor components and their interactions were probed morphologically, spectroscopically and electrochemically. The Ag-Fe 2 O 3 / POM/RGO nanocomposite sensor provided an enhanced electroactive surface area, electrical conductivity and sensitivity for hydrogen peroxide compared to an unmodified glassy carbon electrode (GCE) at-0.55 V versus a saturated calomel electrode. The developed sensor amperometric response was linear across the concentration range from 0.3 mM to 3.3 mM (R 2 ¼ 0.992) with a detection limit and sensitivity of 0.2 lM and 271 lAÁmM-1 Ácm À2 respectively. Concomitantly, a short response time of T90 < 5 sec at a signal-tonoise ratio of 4 was achieved. The sensor was shown to determine hydrogen in the presence of interfering species, and exhibited high selectivity with relative standard deviation values less than 4.2%. The results indicate that the use of RGO to anchor and photochemically reduce POM also improved the reduction properties due to the irregular size distribution and catalytic activity of Ag-Fe 2 O 3 stimulated by its adhesion to the distinctive POM/RGO matrix.

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Silicon-based anodes towards enhanced cycling efficiencies for next-generation lithium-ion batteries

International Journal of Electrochemical Science

Silicon, a cheap and abundant material, is widely considered to be the most promising anode mater... more Silicon, a cheap and abundant material, is widely considered to be the most promising anode material for Li-ion batteries (LiBs) due to its high theoretical specific capacity and low discharge potential. However, silicon-based anodes do have crucial shortcomings like its cycling instability and low conductivity which hinder its practical application. The compositing of silicon and carbon nanomaterials has been shown in literature to be an effective strategy to stabilize the silicon active material while still retaining most of its potential. This review highlights these problems, the various combinations of silicon and carbon nanomaterials presented in literature, and how effective these designs are at overcoming these hurdles toward commercialization. Additionally, challenges remain with regards to the industrialization of silicon-carbon nanocomposites as traditional methods applied in the lab are inefficient, expensive, and lack scalability. Therefore, this review will pay close attention to facile, environmentally friendly, cost-effective, and potentially scalable fabrication methods. This review found a rising trend in works that include, at least, some aspect of industrialization with regards to silicon-carbon nanocomposite synthesis methodology. This trend has been accompanied by a more recent rise in publications on the optimization of silicon-carbon nanocomposite anodes. This could point to the practical application and commercialization of these nanocomposites as next-generation, high-performance LiB anodes could arrive sooner than expected. Based on these findings and other observations made in literature, this review will make recommendations on future research efforts.

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Advances in Paper-Based Battery Research for Biodegradable Energy Storage

Advanced Sensor and Energy Materials

Electrochemical determination of hydrogen peroxide with cytochrome c peroxidase and horse heart cytochrome c entrapped in a gelatin hydrogel

Bioelectrochemistry, 2012

A novel and versatile method, based on a membrane-free enzyme electrode in which both the enzyme ... more A novel and versatile method, based on a membrane-free enzyme electrode in which both the enzyme and a mediator protein are entrapped in a gelatine hydrogel was developed for the fabrication of biosensors. As a proof of principle, we prepared a hydrogen peroxide biosensor by successfully entrapping both horse heart cytochrome c (HHC) and Saccharomyces cerevisae cytochrome c peroxidase (CCP) in a gelatin matrix which is immobilized on a gold electrode. This electrode was first pretreated with 6-mercaptohexanol. The biosensor displayed a rapid response and an expanded linear response range from 0 to 0.3 mM (R = 0.987) with a detection limit of 1 × 10 − 5 M in a HEPES buffer solution (pH 7.0). This method of encapsulation is now further investigated for industrial biosensor applications.

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Spectroscopic and Electrochemical Exploration of Carbon-Infused Intercalation-Type Spinel Composite for Aqueous Systems

Frontiers in Chemistry

Lithium-manganese-based compounds are promising intercalation host materials for aqueous battery ... more Lithium-manganese-based compounds are promising intercalation host materials for aqueous battery systems due to their synergy with high ionic conductive aqueous electrolytes, safety, eco-friendliness, and low cost. Yet, due to poor electrical conductivity and trapping of diffused electrolyte cations within its crystal formation, achieving optimum cycle stability and rate capability remains a challenge. This unfortunately limits their use in modern day high-powered devices, which require quality output with high reliability. Here, the authors propose a facile method to produce LiMn2O4 and LiFe0.5Mn0.5PO4 and compare their structural stability and corresponding electrochemical performance by controlling the interfacial layer through multi-walled carbon nanotubes’ (MWCNTs) infusion. High-resolution scanning electron microscopy results revealed that the active particles were connected by MWCNT via the formation of a three-dimensional wiring network, suggesting that stronger interfacial ...

Humidity Sensing Applications of Lead-Free Halide Perovskite Nanomaterials

Materials

Over the past decade, perovskite-based nanomaterials have gained notoriety within the scientific ... more Over the past decade, perovskite-based nanomaterials have gained notoriety within the scientific community and have been used for a variety of viable applications. The unique structural properties of these materials, namely good direct bandgap, low density of defects, large absorption coefficient, high sensitivity, long charge carrier lifetime, good selectivity, acceptable stability at room temperature, and good diffusion length have prompted researchers to explore their potential applications in photovoltaics, light-emitting devices, transistors, sensors, and other areas. Perovskite-based devices have shown very excellent sensing performances to numerous chemical and biological compounds in both solid and liquid mediums. When used in sensing devices, Perovskite nanomaterials are for the most part able to detect O2, NO2, CO2, H2O, and other smaller molecules. This review article looks at the use of lead-free halide perovskite materials for humidity sensing. A complete description of...

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Organic Nanostructured Materials for Sustainable Application in Next Generation Solar Cells

Applied Sciences, 2021

Meeting our current energy demands requires a reliable and efficient renewable energy source that... more Meeting our current energy demands requires a reliable and efficient renewable energy source that will bring balance between power generation and energy consumption. Organic photovoltaic cells (OPVs), perovskite solar cells and dye-sensitized solar cells (DSSCs) are among the next-generation technologies that are progressing as potential sustainable renewable energy sources. Since the discoveries of highly conductive organic charge-transfer compounds in the 1950s, organic semiconductors have captured attention. Organic photovoltaic solar cells possess key characteristics ideal for emerging next-generation technologies such as being nontoxic, abundant, an inexpensive nanomaterial with ease of production, including production under ambient conditions. In this review article, we discuss recent methods developed towards improving the stability and average efficiency of nanostructured materials in OPVs aimed at sustainable agriculture and improve land-use efficiency. A comprehensive over...

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Enhanced Electrochemistry of Carbon Supported Functionalized Nanocomposite Cathode for Aqueous Lithium‐ion Batteries

Electroanalysis, 2020

Nano Silver-Iron-Reduced Graphene Oxide Modified Titanium Dioxide Photocatalytic Remediation System for Organic Dye

Environments, 2019

The organic water contaminant, methyl orange contaminant (M.O), has shown a hazardous increase in... more The organic water contaminant, methyl orange contaminant (M.O), has shown a hazardous increase in our water systems over the past few years due to its increasing demand in industrial processes. The photocatalytic degradation of the commercial dye was studied through the application of modified TiO2 composite catalysts in aqueous solution under artificial irradiation. The improvement of photocatalytic activity is strongly affected by the various functional groups emerging in the organic substances. In this work, the effect of both silver-iron and silver-iron-reduced graphene oxide-modified titanium dioxide towards M.O remediation as a cost-effective photocatalyst was investigated. We confirmed that the novel AgFe functionalized TiO2 catalyst (AgFe-TiO2) showed more superior remediation activity than the reduced graphene oxide (rGO)-modified TiO2 due to the decreased band gap from 3.02 eV–2.5 eV with increased photocatalysis. Based on the spectroscopic and microscopic results, the enh...

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Electrochemical Immunosensor Based on the Interactions Between Polypyrrole and Cobalt (II) Salicylaldiimine Dendrimer

Transglutaminase is primarily involved with activation and progression of coeliac disease through... more Transglutaminase is primarily involved with activation and progression of coeliac disease through the ingestion of gluten which initiates the production of antibodies against transglutaminase. This results in the damage of the small intestine reducing the diffusion of digested foods into the blood vessels. The diagnosis of coeliac disease can be done by the measurement of antibodies against transglutaminase. This work involves the development of an electrochemical immunosensor for the detection of anti-transglutaminase antibodies. A platinum modified polypyrrole-cobalt (II) salicyladiimine metallodendrimer composite capped with transglutaminase and bovine serum albumin was used for the determination of anti-transglutaminase antibodies. Surface roughness of 879.24 nm, 76.55 nm and 364.27 nm for polypyrrole, cobalt (II) salicyladiimine metallodendrimer and their respective composite in conjunction with cyclic voltammetry showed that such composites provide a suitable micro-environment...

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Graphenatedtantalum(IV)oxideandpoly(4-styrenesulphonicacid)-dopedpolyanilinenanocompositeascathodematerialinanelectrochemicalcapacito

Investigation of the Electrocatalytic Properties of Spherical Palladium Nanoparticles and Palladium(100)iridium Bimetallic Nanocomposites towards Ammonia Electrooxidation on Pt Electrodes

The electrocatalytic properties of cubic palladium-iridium {Pd(100)Ir} bimetallic nanocomposite a... more The electrocatalytic properties of cubic palladium-iridium {Pd(100)Ir} bimetallic nanocomposite and spherical nanoparticles {Pd NPs} towards the electrochemical oxidation of ammonia were investigated in sodium hydroxide on platinum electrode. Interrogation of their electrocatalytic properties through cyclic and square wave voltammetric techniques (CV and SWV)) revealed that the bimetallic nanocomposite {Pd(100)Ir} has better conductivity and higher catalytic activity as evidenced by the maximum current density reached for NH3 oxidation at 1.9838 x 10 -4 A with a decreased onset potential. The Pd NPs gave a maximum catalytic current value of 1.45 x 10 -4 A. This was further validated by the results from electrochemical impedance spectroscopy (EIS) where the bimetallic nanocomposite gave charge transfer and solution resistance values of 96.35 Ω and 137.9 Ω, respectively with the nanoparticles exhibiting higher resistances at 670.6 and 189.5 Ω. These results confirm that facile interfa...

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Orthorhombic Nanostructured Li2 MnSiO4 /Al2 O3 Supercapattery Electrode with Efficient Lithium-Ion Migratory Pathway

Batteries & Supercaps, 2018

nanocomposite (LMSA) was prepared as positive electrode material for aqueous supercapatteries by ... more nanocomposite (LMSA) was prepared as positive electrode material for aqueous supercapatteries by hydrothermal synthesis of Li 2 MnSiO 4 nanoparticles (LMS) followed by wet chemical coating with Al 2 O 3. Scanning electron microscopy (SEM) mapping of the spherical LMSA nanoparticles indicated a homogenous distribution of the constituent atoms. Small-angle X-ray scattering (SAXS) measurements revealed that a prominent population of the nanoparticles show a center-tocenter spacing of 7 nm. This is resulting in a large surface area accessible for the migration of Li-ions and efficient charge storage, leading to improved electrochemical performance as a supercapattery electrode. X-ray diffraction (XRD) and solid-state nuclear magnetic resonance spectroscopy (SS NMR) studies portrayed the orthorhombic (Pmn2 1) crystalline phase of the LMSA and LMS materials which provides a good migratory pathway for the Li-ions. The nanocomposite showed a high rate performance as a positive electrode in an aqueous supercapattery assembled with activated carbon as the negative electrode. The hybrid cell delivered a maximum specific capacitance of 141.5 F g À1 and a maximum specific power of 4020.8 W kg À1 with good cyclic stability and capacitance retention of 93.6 % after 100 cycles. These results the promising potential of the Li 2 MnSiO 4 /Al 2 O 3 nanocomposite as candidate for advanced supercapatteries.

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New Generation Nanoelectrochemical Biosensors for Disease Biomarkers: 1. Indium Telluride Quantum Dots Signaling of Telomerase Cancer Biomarker

Journal of Nanoscience and Nanotechnology, 2016

Herein is a first time report of the development of a highly sensitive 3-mercaptopropionic acidca... more Herein is a first time report of the development of a highly sensitive 3-mercaptopropionic acidcapped indium telluride (3MPA-In 2 Te 3) quantum dots (QDs) genosensor for telomerase detection. This system consists of 3MPA-In 2 Te 3 QDs deposited on gold electrode through cysteamine sulphur linkages.1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide coupling chemistry was used to activate the carboxyl groups of the peripheral 3MPA of the QDs for the attachment of the probe (5-NH 2-GGGATTGGGATTGGGATTGGGTT-3) single-stranded DNA (ssDNA). The sensor functioned by the electrochemical signaling of the hybridization of the probe ssDNA and its complementary (5-AACCCAATCCCAATCCCAATCCC-3) target ssDNA that is native to the telomerase ribonucleo-protein complex. Comparative studies of the amperometric (using cyclic voltammetry, CV) and impedimetric (using electrochemical impedance spectroscopy, EIS) signal transductions of the genosensor revealed that the latter was a better technique. The impedimetric genosensor exhibited high sensitivity and a detection limit (DL) value as low as 0.5 ng/mL, which is one order of magnitude lower than the DL value of 5 ng/mL previously reported for a quartz crystal microbalance (QCM) DNA-based telomerase genosensor.

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Electrochemical Immunosensor Based on the Interactions Between Polypyrrole and Cobalt (II) Salicylaldiimine Dendrimer

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Graphenatedtantalum(IV)oxideandpoly(4-styrenesulphonicacid)-dopedpolyanilinenanocompositeascathodematerialinanelectrochemicalcapacito

Investigation of the Electrocatalytic Properties of Spherical Palladium Nanoparticles and Palladium(100)iridium Bimetallic Nanocomposites towards Ammonia Electrooxidation on Pt Electrodes

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