- Prof. Christopher Arendse
« Chemical vapour deposition of Pb-halide perovskite thin films and its application in solar cells »
Abstract : We demonstrate a two-step low-pressure vapour deposition of methylammonium lead iodide (MAPbI3) and mixed perovskite films in a single reactor. Continuous, polycrystalline lead iodide (PbI2) films were deposited in the first step and successfully converted to high quality perovskite films in the second step during exposure of PbI2 films to methylammonium iodide (MAI) vapor. A complete conversion was realized after 90 min of exposure with an average grain size of ~ 5 μm. The perovskite conversion starts at the PbI2 surface through the intercalation reaction of PbI2 and MAI vapor molecules and progresses toward the PbI2/substrate interface. The absorbance measurements confirmed air stability of the fully converted perovskite for 21 days, ascribed to its superior morphology and grain size. A planar single-junction perovskite solar cell with no additives or additional interfacial engineering was fabricated and tested under open-air conditions, yielding a best power conversion efficiency of 11.7%. The solar cell maintains 85% of its performance up to 13 days in the open air with a relative humidity up to 80%.
- Dr Francis Muya
« Development of next generation biological sensors system as an indication of carcinogenic drugs metabolism«
Abstract: Polymers material and Hydrogels have been a topic of extensive research because of their unique bulk and surface properties. They play a vital role in development of controlled release drug delivery systems. Polysulfone hydrogels are hydrophilic porous materials, which provide the advantage of biocompatibility and effective orientation of biomolecules in the design of the novel biosensors. Biosensors and sensors have also gained attention in the scientific field for their high sensitivity, specificity and easy use. Their broad applicability in medical diagnosis and innovation, food safety and drug analysis or environmental monitoring predicts their phenomenal growth. As highly sensitive, robust and accurate devices are appropriate to use in everyday analysis tasks.
- Dr Keagan Popkas
« Low-cost & Disposable Paper-based Microfluidic ElectroAnalytical Devices for Priority Environmental Pollutant Detection in Resource Limited Settings«
Abstract: The development of low-cost, disposable electrode materials has been at the forefront of sensor technology in recent decades. Paper, offers possibilities for multi-functional, disposable and economically friendly sensing capabilities and has proved to be a suitable reagent storage and substrate material in paper-based analytical devices (PADs). The real-time analysis offered by point-of-contamination devices are pivotal in developing areas where access to skilled labor and instrumentation is often lacking. Chelating agent based signal amplification methods in conjunction with metallic and carbon-based nanostructures have previously been employed in conjunction with electroplated metallic films to improve the electrode sensitivity in trace metal stripping analysis. In this work, an overview of our current research regarding the development of low-cost, sensitive electrochemical sensing approaches for the determination of trace metal contamination of drinking and real water samples is presented. In particular, (i) dry reagent storage approaches to prepare paper-based electrochemical cells, (ii) paper-based screen and inkjet printed electrodes and (iii) paper-based microfluidic flow/separation systems have been developed as sensing platforms for the quantitative analysis of Ni(II), based on the accumulation of Ni(dmgH)2 complexes at the modified electrode surface by square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV). Furthermore, the effect of chelating agents, graphene and gold nanomaterial functionalization and ionic liquid incorporation have been studied to improve the device sensitivity by offering enhanced selectivity, electron-transfer kinetics, increased active surface area and increased catalytic properties, respectively. This study offers the first investigation on the feasibility of adsorptive electrochemical sensing methods at porous cellulose paper-based substrates. Improved sensitivities were achieved at each developed sensing device well below the EPA and WHO standards of 0.1 mg L-1 or 0.1 ppm for Ni(II) in drinking water.
- Julie Beurienne (Master Student)
« Synthesis and characterization of Ionic Liquid
Polymers for electrochemical biosensors »
Abstract: The field of electrolyte gated organic field effect transistor (EGOFET) has been attracting a wide attention from the last two decades thanks to their sensitivity, selectivity and their low operating voltage. In the development of new materials for preparation of high performing EGOFET sensors, there is a rise in using polyelectrolytes instead of conventional electrolyte as dielectric layer. Thus, the use of polyelectrolyte could minimize these effects, leading to more performant devices. Furthermore, the use of polyelectrolyte could enhance the switching time (on/off) compared to conventional electrolyte, resulting from high ion polarization within the polyelectrolyte. Within this context, we propose to use poly(ionic liquid) – PIL, an emerging class of charged polymer with unique physico-chemical features, as new type of polyelectrolyte in EGOFET devices. In this work, we aim to develop negatively charged poly(ionic liquids) by means of two approaches, chemical and electrochemical polymerization. Then, the prepared polymers, Poly(2-acrylamido-2-methylpropane sulfonate) and Poly(3-sulfonyl(trifluoromethane sulfonyl) imide propyl methacrylate), were intensively investigated by different techniques to reveal their physicochemical and electrochemical behaviors.
- Mathilde Mittler (Master Student)
« Nanomaterials for reagentless biosensors »
Abstract: Aptasensors and reagentless biosensors have been being popular as compared to other biosensors (sandwich type immunosensors, enzymatic, …) because they are more stable, lower cost and easier in handling. In addition, in the field of biosensors the use of nanomaterials to increase surface area, electrochemical activity, probe immobilization and to act as a redox probe with high current response is of high interest to provide sensors with low limit of detection and high sensitivity. In this study, we develop a reagentless electrochemical aptasensor for detection of thrombin using silver nanoparticles (AgNPs) as nanoprobe. To this end, screen printed gold electrodes were modified with silver nanoparticles (redox probe with a low oxidation potential), thiol-modified aptamer (thrombin probe) and a co-thiol (to bloc free gold surface). This presentation will deal with the synthesis and characterization of AgNPs, the effect of 4 co-thiol on electrochemical oxidation and reduction of both [Fe(CN)6]3-/4- in solution and AgNPs deposits, as well as sensing layer preparation by successively immobilizing the thiol aptamer and the co-thiol.