July 12th 2021
Prof. Francis Ntumba (SensorLab, Department of Chemistry, UWC).
Title: “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 Pokpas (SensorLab, Department of Chemistry, UWC).
Title: « 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 paperbased analytical devices (PADs). The real-time analysis offered by point-ofcontamination 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
July 13th 2021
Pr. Christopher Arendse (Department of Physics and Astronomy, UWC).
Title: « 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%.
Julie Beurienne (M2 student, LPPI, CYU)
Title: « Synthesis and characterization of polymeric ionic liquids towards preparation of EGOFET based sensors »
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 (M2 student, LPPI, CYU)
Title: « 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.
September 14th 2021
Dr Philippe Banet (LPPI, Department of Chemistry, CYU).
Course to the Honor SA students (Level4) (2 hours)
Title: Electrochemical sensors and applications
September 15th 2021
Dr Alae El Haitami (LPPI, Department of Chemistry, CYU).
Course to the Honor SA students (Level4) (2 hours)
Title: Introduction and application of Langmuir polymer films
September 17th 2021
Prof. Thuan Nguyen Pham Truong (CY – LPPI, Department of Chemistry, CY Cergy Paris Université) thuan-nguyen.pham-truong@cyu.fr
Title: “Electrolyte gated organic field effect transistor. An introduction”
Abstract: With the unstoppable growth of the world population, the amount of chemicals that has been uncontrollably released to the environment and thus to the ecosystem becomes nowadays one of the biggest issues. In large dose, these chemicals cause very harmful consequences to living organisms, including human beings. Accordingly, highly sensitive systems need to be developed to detect these products as well as presence of eventually tiny harmful seedlings towards people’s health. In responding to the problem, classical analytical technologies, such as gas/liquid chromatography, mass spectroscopy, etc., provide high performance in sensing selective analytes with precision and reliability. However, these techniques are not capable for on-field investigations and for integration in portable devices alongside with their high cost and they have to be operated by skilled people. Within this context, transistor-based sensors, especially electrolyte gated organic field effect transistors, have appeared as one of excellent candidates for detection of analytes with ultra-high precision and selectivity. The working principle of EGOFET sensors is based on the change in capacitance coupled with electronic devices. Indeed, seeking for new materials and new approaches to understand and to amplify the capacitance changes for boosting the performance of the sensor is still matter of interest for scientific researches. Accordingly, this seminar aims to provide recent advancements in the field to open a scientific discussion towards elaboration of next generation of transistor-based sensors.
Mr. Kevin Tambwe (PhD student, SensorLab, Department of Chemistry, UWC)
Title: “Synthesis and construction of lead-free metal halide perovskite/polymer nanocomposites for use in high-performance humidity sensors.”
Abstract: Lead halide perovskites have demonstrated outstanding achievements in photoelectric applications owing to their unique properties. They have emerged as possible materials of choice for use in humidity sensors which is a much lesser-known application for perovskite materials. However, the moisture sensitivity of lead halide perovskite has rarely been exploited for use into an applicable humidity sensor due to the intrinsic instability and toxicity issues. In this project, due to their extraordinary humidity-dependent electrical properties and good stability, three highly stable lead-free perovskites, Cs2BiAgBr6, Cs2PdBr6 and Cs2InBr5.H2O will each be impregnated within the pores of the polymer matrix to form part of the active material for humidity sensor. The as fabricated humidity sensors response and recovery times is going to be evaluated in terms of their impedance or capacitance outputs under a relative humidity range going from 11% to 95%. These lead-free perovskites are said to possess great potential for real-time humidity sensing application.
Mr. Rabelani Leonard Sithi (PhD student, SensorLab, Department of Chemistry, UWC)
Title: “Novel polyHIPE materials for site directed coronavirus immunosensor devices.”
Abstract: This study will investigate the synthesis and modification of the characteristics of polyamic acid (PAA)-divinylbenzene (DVB)-based poly(high internal phase emulsions)s polyHIPE by incorporating an additive into the polyHIPE matrix, i.e. graphene to enhance the mechanical and physical properties. The modified polyHIPEs will be functionalized with antibodies for detection of SARS-CoV-2. PolyHIPEs composites will be prepared in water in oil (w/o) emulsion system. The polyHIPEs will be obtained through the removal of internal phase after curing of continuous phase at 70°C. Surface properties and morphologies of obtained polyHIPEs will be studied by scanning electron microscopy. The ongoing corona virus disease 2019 (COVID-19) has not just challenged the global health care system to the teeth but also disturbed different facets of humankind. In this time of catastrophe, researchers globally have applied intensive effort to curb the spread of the disease in many feasible strategies, including diagnosis, treatment and vaccination. Since the transmission of the disease has not yet ceased, investigating new ways to diagnose the disease could be crucial to the management of the disease. A timely and effective diagnosis could be an advantage until a highly efficient vaccine is manufactured. In the COVID-19 diagnosis, the currently preferred molecular tests are the commercial and in-house kits. Nevertheless, the constraint of high cost and extended procedures hinder their application in large-scale testing. Bearing in mind the ongoing disease transmission, the hunt for a substitute test that is economical, easy, and appropriate for mass testing and monitoring is the current priority. Immunological tests could be such a substitute. In recent months, a large amount of immunological prompt tests has been developed and approved the world over. The objective of this investigation is to develop a polyHIPE-based immunosensor for the detection of SARS-CoV-2.
October 15th 2021
Dr. Cédric Vancaeyzeele (LPPI, Department of Chemistry, CYU).
Subject: « PolyHIPE »
November 30th 2021
Dr. Demetrio de Silva Filho (Institute of Physics – University of Brasilia dasf@unb.br)
Title: « Organic semiconductors: Research and Applications »
Abstract: Organic semiconductors have been known for more than a century, but it was only in the past 30 years that intense research has been conducted to move it to practical applications. One of the promising applications, Organic Light-Emitting Diodes, is already a part of our daily lives. On the other hand, organic photovoltaics is still struggling to reach the performance necessary for commercialization. In this talk, a brief introduction of this novel class of materials will be provided, along with how Quantum Chemistry can be used to a better understanding of the mechanisms behind the operation of these devices. Also, an introduction of hybrid perovskite solar cells will be presented together with our current joint efforts with LPPI to understand better the hole transport layer’s role and to design new organic molecules to compose this layer.
In 2022 :
18 February 2022
Prof. Francis Ntumba (UWC – SensorLab) fntumba@uwc.ac.za
Title: “Development of an electro-analytical chemical sensor for the effective detection of benzo(a)pyrene as a marker for polyaromatic hydrocarbons in seawater”
Abstract: Marine pollution is a global environmental problem; human activities in the coastal area and marine water contribute to the discharge of various kinds of pollutants such as heavy metal and polyaromatic hydrocarbons (PAH) into the marine ecosystem [1]. Heavy metal ions and PAH represent a common health hazard throughout the world, due to their toxic effects. The main reason for these contaminations is considered as persistent due to their toxicity properties, which could create a serval problem for different kinds of marine ecosystems which can be accumulated in marine organisms. Three compounds isolated from marine organisms, are in preclinical development as possible anticancer agents [2] and may marine organisms have the potential to bioconcentrate high levels of metal from their environment. Metal bioaccumulation by marine organism has been the subjects of considerable interest in recent years because of serious concern that high levels of metal ions may have detrimental effects on the marine organism and may create problems in relation to their suitability as food for humans [3]. The accumulation of heavy metal ions and polyaromatic hydrocarbons can cause health problems such as hypertension, brain damage, kidney failure, and cancer. Therefore, it is imperative to develop an effective electro-analytical method for the quantification of metal ions and detection of PAH in the South African Maritime Safety Authority (SAMSA) seawater as an indication of toxicity to the marine ecosystem. The electro-analytical techniques will be evaluated by cyclic voltammetry (CV), square waves voltammetry (SVW), stripping voltammetry (STV) or electrochemical impedance spectroscopy (EIS). These methods will be compared to the traditional methods such as HPLC and ICP in terms of selectivity, sensitivity and rapidity.
Prof. Natthawat Semakul (Chiang Mai University) natthawat.semakul@cmu.ac.th
Title: “New tools for N-heterocycles synthesis and molecular engineering of materials for energy storage.”
Abstract: Nitrogen-containing heterocycles are present in an array of natural products and small molecule drugs. Therefore, developing expedient methods for accessing nitrogen-heterocycles from readily available precursors are a top priority. In this context, Rh(III)-catalyzed C-H activation of acrylamide following by alkene insertion to provide d-lactams will be described. Additionally, the ability to controlling regio-, diastereo-, and enantio- selectivity in alkene insertion by the modulation of cyclopentadenyl architecture on Rh(III) metal center will be discussed. Batteries based on earth abundant elements (C, H, O, N) are being investigated as more sustainable alternative to conventional materials. In this regard, designing and developing organic-based electrode materials with good specific capacity, rate capability, and cycling stability are highly desirable. In the second part of seminar, recent efforts on the utilization of porous organic polymer for anode in Li-organic battery as well as the idea of bi-redox polymers for allorganic battery will be described.
13th April 2022
Dr. Keagan POKPAS (Lecturer & Senior Researcher at SensorLab, University of the Western Cape, South Africa)
Title: Disposable, Graphenated Pencil Graphite Electrode Arrays for Pollutant Determination by Stripping Voltammetric Techniques
Abstract: Great interest has been placed on methods to improve the detection sensitivity and reproducibility of electrochemical sensors for synthetic xenoestrogen, Bisphenol A, a common painkiller, Paracetamol, and metal analysis monitoring in recent years. In this work, current research into the development of disposable electrode materials with high sensitivity is explored for the determination of common pollutants in water samples by a pencil graphite array modified with an electrochemically reduced graphene oxide, antimony nanoparticle (ERGO–SbNP) nanocomposite. The combined synergistic effects, improved electron-transfer kinetics, and the active surface of the metallo-carbon nanostructure on the performance of the electrolytic determination of various water pollutants at the low-cost, disposable electrode array is studied. The work presents (i) a novel multi-electrode coating technique as a simple, time-saving approach for the fabrication of highly reproducible single-use electrodes to limit the effect of electrode fouling and the need for anti-fouling modifiers commonly associated with the formation of secondary products produced during detection, and (ii) enhanced detection sensitivity arising from the improved active surface area. The novel dual-functional working electrode array, consisting of 8 interconnected disposable pencil graphite rods (with a single Ag/AgCl reference and Pt wire counter electrode) was utilized for the stripping voltammetric determination of the target analyte. Here, preconcentration of the electrode array surface precedes the electrolytic determination of the redox-active analyte allowing for improved selectivity and sensitivity. The results show good detection sensitivity for each studied contaminant in tap water samples below WHO, USEPA, and South African drinking water standards.
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