Development of nanostructured material based electrochemical sensors for food safety and quality control

The issue of foodborne related illnesses due to additives and contaminants poses a significant challenge to food processing industries. Electrochemical-based strategies offer simple and robust analytical tools, which are ideal for food safety and the quality assessment process, in contrast to conventional instrumentation methods. The development of nanomaterials based electrochemical sensors has garnered significant attention due to their capacity for accurate analytical quantification, which has strong potential toward the replacement of conventional techniques by offering advantages such as high sensitivity and selectivity, real-time monitoring, and ease of use. During my Ph.D. study, four distinct types of nanostructured materials were used to develop electrochemical sensors for the detection of food preservatives in food and beverage products. The consumption of excessive amounts of nitrite (NO2-) can be detrimental to the human body. In light of this, we developed an electrochemical sensor based on cobalt oxide nanosheets and gold nanoparticles (Co3O4/Au) for NO2- sensing. The nanomaterial was synthesized through the electrodeposition of gold (Au) on Co3O4 nanosheets. The Co3O4/Au/GCE was capable of electrooxidizing nitrite with a higher anodic peak current, and the sensor exhibited excellent linearity with a limit of detection (LOD) value of 0.11 μM. A nanoporous gold microelectrode was synthesized for the determination of contaminants (hydrazine, N2H4) and preservatives (sulfite (SO32-), nitrite (NO2-)). The fabricated microelectrode was characterized via scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). The nanoporous gold microelectrode exhibited excellent electrochemical performance for the simultaneous electrochemical oxidation of N2H4, SO32-, and NO2-. In addition, the nanoporous gold microelectrode possessed high selectivity and stability. The performance of ii the electrochemical sensor was further validated using actual samples such as water, wine, apple cider beer, and beef with good recovery rates, thereby confirming its potential for food safety and quality control applications. A novel electrochemical sensor was developed using fluorine-doped graphene oxide (F-GO) for the detection of caffeic acid (CA). The fabricated nanomaterial was systematically characterized using SEM and X-ray photoelectron spectroscopy (XPS). The electrochemical investigation of F-GO/GCE for CA oxidation revealed that it demonstrated high electrocatalytic activity compared with other electrodes (e.g., bare GCE and GO/GCE). The analytical quantitation of CA recorded with the F-GO/GCE produced a stable oxidation signal over the selected CA concentration range (0.5 μM to 100.0 μM, R2 = 0.9960) with a LOD value of 0.018 μM. The fabricated sensor successfully exhibited the capacity to directly detect CA in assorted wine samples without pretreatment. To further explore the applications of the F-GO, a nanocomposite material synthesized with Au and F-GO was employed for the development of an Au/F-rGO/GCE sensor for the detection of vanillin. The electrochemical performance and the analytical capabilities of this novel electrochemical sensor were investigated using electrochemical techniques such as CV and DPV. The excellent sensitivity, selectivity, augmented electrocatalytic activity, and reproducibility of these developed electrochemical sensors can be attributed to the high conductivity of the nanostructured materials. The dimensions and morphologies of the developed nanomaterials played a critical role in enhancing the electrochemical performance of these sensors

Engineered carbon-nanomaterial-based electrochemical sensors for biomolecules

The study of electrochemical behavior of bioactive molecules has become one of the most rapidly developing scientific fields. Biotechnology and biomedical engineering fields have a vested interest in constructing more precise and accurate voltammetric/amperometric biosensors. One rapidly growing area of biosensor design involves incorporation of carbon-based nanomaterials in working electrodes, such as one-dimensional carbon nanotubes, two-dimensional graphene, and graphene oxide. In this review article, we give a brief overview describing the voltammetric techniques and how these techniques are applied in biosensing, as well as the details surrounding important biosensing concepts of sensitivity and limits of detection. Building on these important concepts, we show how the sensitivity and limit of detection can be tuned by including carbon-based nanomaterials in the fabrication of biosensors. The sensing of biomolecules including glucose, dopamine, proteins, enzymes, uric acid, DNA, RNA, and H2O2 traditionally employs enzymes in detection; however, these enzymes denature easily, and as such, enzymeless methods are highly desired. Here we draw an important distinction between enzymeless and enzyme-containing carbon-nanomaterial-based biosensors. The review ends with an outlook of future concepts that can be employed in biosensor fabrication, as well as limitations of already proposed materials and how such sensing can be enhanced. As such, this review can act as a roadmap to guide researchers toward concepts that can be employed in the design of next generation biosensors, while also highlighting the current advancements in the field.ope

X-Ray photoelectron spectroscopic characterization of chemically modified electrodes used as chemical sensors and biosensors : a review

The characterization of chemically modified sensors and biosensors is commonly performed by cyclic voltammetry and electron microscopies, which allow verifying electrode mechanisms and surface morphologies. Among other techniques, X-ray photoelectron spectroscopy (XPS) plays a unique role in giving access to qualitative, quantitative/semi-quantitative and speciation information concerning the sensor surface. Nevertheless, XPS remains rather underused in this field. The aim of this paper is to review selected articles which evidence the useful performances of XPS in characterizing the top surface layers of chemically modified sensors and biosensors. A concise introduction to X-ray Photoelectron Spectroscopy gives to the reader the essential background. The application of XPS for characterizing sensors suitable for food and environmental analysis is highlighted

Electrochemical determination of gallic acid in food matrices using novel materials.

Gallic acid (GA), as an endogenous polyphenol, has shown many different important properties that have influenced its use in the food and pharmaceutical industry. These properties include its antioxidant, anti-cancer, anti-tumor, anti-HIV and anti-ulcerogenic activities. The most commonly used GA determination techniques have been the spectrophotometric and chromatographic techniques. However, these techniques have shown some drawbacks; they are expensive, labour intensive, time-consuming and are not suitable for in-situ measurements. Electrochemical methods using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at inert glassy carbon electrode (GCE) or carbon paste electrodes (CPE) have also been used in the determination of GA. However, despite their easy application and fast result generation, their sensitivity and selectivity have been relatively inadequate for the analysis of GA found in beverages and pharmaceutical products. The aim of this study is therefore to investigate and develop novel nanomaterials-based electrochemical sensors for determination and analysis of GA that is fast, sensitive, cost-effective and selective. In this study, the detection of GA in red and white wines was achieved using CV, through the development of carbon-based working electrodes modified with graphene oxide nanoparticles and other metal oxide nanoparticles. The synthesised metal oxide nanoparticles were characterised using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and Zetasizer (for particle size analysis). Meanwhile, characterisation of the developed electrodes was carried out using CV, DPV and electrochemical impedance spectroscopy. The electrochemical effects of the electrodes were analysed. This thesis presents the results of a novel graphene oxide nanocolloids-SiO2 nanoparticles combination used for the electrochemical determination of GA. The results show enhanced peak currents, with high sensitivity and selectivity. The anodic peak current was enhanced from 241 µA (for the bare GCE) to 411 µA (for the modified GCE) - with a limit of detection (LOD) of 2.09 x 10-6 mol L-1, within a concentration range of 6.25 x 10-6 to 1.0 x 10-3 mol L-1. The thesis also proposes that there is a synergistic effect between SiO2 nanoparticles and graphene oxide nanocolloids in the determination of GA. Synthesised amorphous zirconium oxide nanoparticles were used for the modification of a carbon paste electrode and used for the determination of GA. The electrode modification enhanced the electrochemical activity of GA, with increased sensitivity and selectivity. The modified electrode produced an enhanced anodic peak from 260 µA (for the bare electrode) to 451 µA (for the modified electrode) - with an LOD of 1.24 x 10-7 mol L-1, within a range of 1 x 10-6 to 1.0 x 1 x 10-3 mol L-1. The thesis additionally makes a novel proposal for the interaction and effect of the amorphous zirconia nanoparticles on the graphite in the CPE. Zinc oxide nanoparticles and cobalt oxide nanoparticles were also used individually for the modification of carbon paste electrodes. The modified electrodes showed an enhanced effect on GA oxidation. This enhanced effect was an increase in anodic peak current from 261 µA to 414 µA, when the CPE was modified. The LOD produced by the ZnO nanoparticles-modified CPE was 1.86 x 10-7 mol L-1, within a concentration range of 1 x 10-3 to 5 x 10-2 mmol L-1. Meanwhile, the effect of scan rate and the effect of pH show that the electrodes were more effective in acidic pH, and that the GA-electrode interaction was an adsorption-controlled process. Cobalt oxide nanoparticles were also synthesised, characterised and used for the modification of CPE. The modified electrode produced an enhanced anodic peak current from 302 µA (for the bare CPE) to 404 µA (for the modified electrode). The LOD of the modified electrode was studied and found to be 1.52 x 10-6 mol L-1, at a concentration range of 1 x 10-4 to 1 x 10-3 mol L-1. The modified electrodes were successfully used for the determination of GA in real samples of red and white wine. Based on the electrochemical activities of the different electrodes made, the Zirconium dioxide nanoparticles-modified carbon paste electrode seems to have produced the best results. The zirconium dioxide-modified CPE showed increased sensitivity and better limit of detection for GA

Determinação simultânea de dopamina, serotonina e triptofano utilizando eletrodo modificado com resíduos derivados da indústria do aço.

TCC (graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Físicas e Matemáticas. Curso de Química.Neurotransmissores e seus precursores são fundamentais para o estudo do funcionamento do cérebro, pois estes compostos estão ligados a distúrbios físicos, como síndrome do intestino irritável e até anomalias psicológicas, como a esquizofrenia. Portanto, obter formas de quantificação destas espécies é imprescindível para o tratamento de doenças, além de ser um meio de aliar dados laboratoriais com estudos comportamentais. Neste trabalho foi elaborado uma plataforma de detecção inédita para quantificação simultânea de três analitos, dois neurotransmissores, a dopamina (DP) e a serotonina (5-HT), e o precursor da serotonina, o triptofano (TP). A arquitetura eletródica desenvolvida consiste na modificação química de eletrodos a base de pasta de carbono por meio do resíduo provindo da laminação do aço. Este resíduo utilizado como modificação é formado por uma mistura de três óxidos de ferro, FeO, Fe2O3, e Fe3O4, presentes em diferentes proporções. Medidas por voltametria cíclica (CV) foram conduzidas em eletrólito suporte, solução tampão Britton-Robinson (B-R). Utilizando a voltametria de onda quadrada (SWV), com os devidos parâmetros otimizados, foram construídas curvas de calibração para dopamina, serotonina e triptofano, nas faixas entre 0,49-21 μmol L‒1, 0,49-13,6 μmol L‒1 e 2,9-25 μmol L‒1, respectivamente. Os limites de detecção (LoD) e quantificação (LoQ) foram de 0,21 μmol L‒1 e 0,49 μmol L‒1 (DP), 0,13 μmol L‒1 e 0,48 μmol L‒1 (5-HT), e 2,18 μmol L‒1 e 2,87 μmol L‒1 (TP) (para n=3). O sensor desenvolvido apresenta seletividade e compromisso entre o perfil voltamétrico e as intensidades de corrente para cada analito, permitindo a detecção simultânea de três neurotransmissores. Estudos mais detalhados podem ser conduzidos para uma melhor performance analítica, a partir do emprego de etapas de pré-concentração dos analitos na superfície do eletrodo

Progress of Advanced Nanomaterials in the Non-Enzymatic Electrochemical Sensing of Glucose and H2O2

Non-enzymatic sensing has been in the research limelight, and most sensors based on nanomaterials are designed to detect single analytes. The simultaneous detection of analytes that together exist in biological organisms necessitates the development of effective and efficient non-enzymatic electrodes in sensing. In this regard, the development of sensing elements for detecting glucose and hydrogen peroxide (H2O2) is significant. Non-enzymatic sensing is more economical and has a longer lifetime than enzymatic electrochemical sensing, but it has several drawbacks, such as high working potential, slow electrode kinetics, poisoning from intermediate species and weak sensing parameters. We comprehensively review the recent developments in non-enzymatic glucose and H2O2 (NEGH) sensing by focusing mainly on the sensing performance, electro catalytic mechanism, morphology and design of electrode materials. Various types of nanomaterials with metal/metal oxides and hybrid metallic nanocomposites are discussed. A comparison of glucose and H2O2 sensing parameters using the same electrode materials is outlined to predict the efficient sensing performance of advanced nanomaterials. Recent innovative approaches to improve the NEGH sensitivity, selectivity and stability in real-time applications are critically discussed, which have not been sufficiently addressed in the previous reviews. Finally, the challenges, future trends, and prospects associated with advanced nanomaterials for NEGH sensing are considered. We believe this article will help to understand the selection of advanced materials for dual/multi non-enzymatic sensing issues and will also be beneficial for researchers to make breakthrough progress in the area of non-enzymatic sensing of dual/multi biomolecules.Scopu

Carbon-Based Nanomaterials for (Bio)Sensors Development

Carbon-based nanomaterials have been increasingly used in sensors and biosensors design due to their advantageous intrinsic properties, which include, but are not limited to, high electrical and thermal conductivity, chemical stability, optical properties, large specific surface, biocompatibility, and easy functionalization. The most commonly applied carbonaceous nanomaterials are carbon nanotubes (single- or multi-walled nanotubes) and graphene, but promising data have been also reported for (bio)sensors based on carbon quantum dots and nanocomposites, among others. The incorporation of carbon-based nanomaterials, independent of the detection scheme and developed platform type (optical, chemical, and biological, etc.), has a major beneficial effect on the (bio)sensor sensitivity, specificity, and overall performance. As a consequence, carbon-based nanomaterials have been promoting a revolution in the field of (bio)sensors with the development of increasingly sensitive devices. This Special Issue presents original research data and review articles that focus on (experimental or theoretical) advances, challenges, and outlooks concerning the preparation, characterization, and application of carbon-based nanomaterials for (bio)sensor development

Advance Nanomaterials for Biosensors

The book provides a comprehensive overview of nanostructures and methods used to design biosensors, as well as applications for these biosensor nanotechnologies in the biological, chemical, and environmental monitoring fields. Biological sensing has proven to be an essential tool for understanding living systems, but it also has practical applications in medicine, drug discovery, food safety, environmental monitoring, defense, personal security, etc. In healthcare, advancements in telecommunications, expert systems, and distributed diagnostics are challenging current delivery models, while robust industrial sensors enable new approaches to research and development. Experts from around the world have written five articles on topics including:Diagnosing and treating intraocular cancers such as retinoblastoma; Nanomedicine in cancer management; Engineered nanomaterials in osteosarcoma diagnosis and treatment; Practical design of nanoscale devices; Detect alkaline phosphatase quantitatively in clinical diagnosis; Progress in the area of non-enzymatic sensing of dual/multi biomolecules; Developments in non-enzymatic glucose and H2O2 (NEGH) sensing; Multi-functionalized nanocarrier therapies for targeting retinoblastoma; Galactose functionalized nanocarriers; Sensing performance, electro-catalytic mechanism, and morphology and design of electrode materials; Biosensors along with their applications and the benefits of machine learning; Innovative approaches to improve the NEGH sensitivity, selectivity, and stability in real-time applications; Challenges and solutions in the field of biosensors

The 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry

The 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry was held on 1–15 July 2021. The scope of this online conference was to gather experts that are well-known worldwide who are currently working in chemical sensor technologies and to provide an online forum for the presention and discussion of new results. Throughout this event, topics of interest included, but were not limited to, the following: electrochemical devices and sensors; optical chemical sensors; mass-sensitive sensors; materials for chemical sensing; nano- and micro-technologies for sensing; chemical assays and validation; chemical sensor applications; analytical methods; gas sensors and apparatuses; electronic noses; electronic tongues; microfluidic devices; lab-on-a-chip; single-molecule sensing; nanosensors; and medico-diagnostic testing