Distributed environmental monitoring

With increasingly ubiquitous use of web-based technologies in society today, autonomous sensor networks represent the future in large-scale information acquisition for applications ranging from environmental monitoring to in vivo sensing. This chapter presents a range of on-going projects with an emphasis on environmental sensing; relevant literature pertaining to sensor networks is reviewed, validated sensing applications are described and the contribution of high-resolution temporal data to better decision-making is discussed

Analysis of relevant technical issues and deficiencies of the existing sensors and related initiatives currently set and working in marine environment. New generation technologies for cost-effective sensors

The last decade has seen significant growth in the field of sensor networks, which are currently collecting large amounts of environmental data. This data needs to be collected, processed, stored and made available for analysis and interpretation in a manner which is meaningful and accessible to end users and stakeholders with a range of requirements, including government agencies, environmental agencies, the research community, industry users and the public. The COMMONSENSE project aims to develop and provide cost-effective, multi-functional innovative sensors to perform reliable in-situ measurements in the marine environment. The sensors will be easily usable across several platforms, and will focus on key parameters including eutrophication, heavy metal contaminants, marine litter (microplastics) and underwater noise descriptors of the MSFD. The aims of Tasks 2.1 and 2.2 which comprise the work of this deliverable are: • To obtain a comprehensive understanding and an up-to-date state of the art of existing sensors. • To provide a working basis on “new generation” technologies in order to develop cost-effective sensors suitable for large-scale production. This deliverable will consist of an analysis of state-of-the-art solutions for the different sensors and data platforms related with COMMONSENSE project. An analysis of relevant technical issues and deficiencies of existing sensors and related initiatives currently set and working in marine environment will be performed. Existing solutions will be studied to determine the main limitations to be considered during novel sensor developments in further WP’s. Objectives & Rationale The objectives of deliverable 2.1 are: • To create a solid and robust basis for finding cheaper and innovative ways of gathering data. This is preparatory for the activities in other WPs: for WP4 (Transversal Sensor development and Sensor Integration), for WP(5-8) (Novel Sensors) to develop cost-effective sensors suitable for large-scale production, reducing costs of data collection (compared to commercially available sensors), increasing data access availability for WP9 (Field testing) when the deployment of new sensors will be drawn and then realized

Development, fabrication and application of electrochemical devices using 3D-printing

Esta tese tem como foco o uso de recentes inovações em manufatura aditiva (impressao 3D) na confecção de células e sensores eletroquímicos. Como introdução este trabalho faz uma revisão completa sobre o tema, seguida de construção, caracterizações e aplicações de sensores e células impressas em 3D na eletroanalítica. A primeira delas é uma célula eletroanalítica para medidas hidrodinâmicas e estacionárias. A segunda se trata de sensores impressos por 3D baseado em um termoplástico condutivo, dopado com materiais carbonáceos (grafeno ou negro de fumo). A combinação destas células e eletrodos impressos em 3D contendo grafeno, foram aplicados na área forense na amostragem, identificação e quantificação do explosivo 2,4,6-trinitrotolueno, o conhecido TNT. O dispositivo foi proposto para amostragens em locais suspeitos de crimes que envolvam manuseio deste material. Um limite de detecção (LOD) de 0,4 −1 em uma faixa linear de 1 – 870 mol L−1 foram reportados. Na área de bioanalítica, 3 moléculas foram analisadas em metodologias propostas. A primeira utilizando ou amperometria de múltiplos pulsos, para analise simultânea de nitrito e ácido úrico, em saliva e urina atingindo resultados de faixa linear de 0,5–250 mol L−1 para ambos analitos e LODs de 0,02 e 0,03 mol L−1 para ácido úrico e nitrito respectivamente, com precisão calculada de até RSD < 2,1 %. A modificação do sensor com a enzima glicose oxidase (GOx) foi proposta, atingindo LOD de 15 mol L−1, precisão intra-dia de 5% e índices de recuperação entre 90–105 % para glicose em plasma sanguíneo. Todos os dispositivos apresentaram custo inferior a U$0,50/unidade e alta precisão de fabricação (RSD = 4uma caneta 3D pode ser utilizada na construção de sensores com termoplástico condutivo contendo negro de fumo como material condutor. Em uma comparação o eletrodo impresso por impressora 3d! apresentou melhores característica analíticas em comparação ao eletrodo 3 em 1 proposto usando a caneta 3D, porém características promissoras foram observadas como possibilidade de análise em uma gota, baixo consumo de plástico condutivo na construção e resultados voltamétricos comparáveis a eletrodos SPE’s comerciais. Tudo isso com formato portátil e totalmente adaptável.CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorFAPEMIG - Fundação de Amparo a Pesquisa do Estado de Minas GeraisFAU - Fundação de Apoio UniversitárioIQUFU - Instituto de Química da Universidade Federal de UberlândiaTese (Doutorado)Recent advances in the manufacturing of electroanalytical sensors, cells and devices using 3D-printing is the focus of this work. This thesis introduces this theme/topic with a wide and critical literature review, followed by several proposed applications at electroanalytical prototyping and sensing. The first of those is an electroanalytical cell, for hydrodynamic and stationary measurements, and 3D-printed sensors based on a conductive thermoplastic with carbonaceous materials (graphene or carbon black). The electrodes were applied in the forensic field by quantification, detection and sampling 2,4,6-trinitrotoluene, well known as TNT. The proposed device is a flexible samplersensor for suspect powders in crime scenes and presented proper analytical characteristics reaching a LOD of 0.4 mol L−1 in a linear interval of 1 – 870 molL−1 for TNT. This thesis also shows how a 3D pen can be used to fabricate electrochemical sensors, also proposed for TNT detection,presenting higher LOD, but interesting characteristics such as low volume in a drop of 100 L, low conductive plastic consumption and voltammetric results similar to a commercial SPE. All this in portable shape cylindrical or three in one electrode. In the field of bioanalytics, glucose was a target molecule for 3D-printed electrodes modified with glucose oxidase, using chronoamperometry, reaching LOD of 15 molL−1, inter-day and intra-day precision lower than 5 analysis of blood plasma. A simultaneous method using amperometric detection of nitrite and uric acid within a linear range from 0.5–250 mol L−1 for both analytes, LODs of 0.02 and 0.03 mol L−1 for uric acid and nitrite, respectively, and high precision (RSD < 2.1 biosensors for the analysis of real biological samples with analytical features comparable to conventional modified electrodes.All the 3D-printed devices presented a unit cost lower than U$0.50 and high precision of fabrication (RSD = 4%)

Biomolecular engineered sensors for diagnostic applications

Electrochemistry is a powerful technique that offers multiple possibilities and which is in constant evolution. Simple modifications of the electrode surface can result in an improvement of the selectivity and sensitivity of the method. However some situations require more complex modifications such as the incorporation of an external agent to the electrode surface, or within the actual electrode. This thesis describes the development and characterization of a range of novel electrochemical sensors for multiple applications covering agri-food, biomedical and environmental contexts. The foundations of the approach rest upon the development of carbon-loaded polycarbonate composite films. Their fabrication is described and the ease with which they can be modified and physically adapted is highlighted and critically evaluated. The response of the resulting sensors have been validated against conventional techniques. An overview of the technologies employing carbon electrodes is presented in Chapter 1 and serves to set the context of the subsequent research. The various methodologies employed are outlined in Chapter 2. Preliminary modifications of the analytical process has evolved from the ex situ functionalisation of the conventional carbon electrodes with copper (Chapter 3) through to the examination of the versatility and complexities of sample pre-treatment (Chapter 4). The pre-treatment of the sample using naphthoquinones as labeling agents has been developed and this work was extended to examine a wholly new derivatisation agent which could have analytical and clinical/veterinary diagnostic merit. A new direction was sought to overcome the limitations of the conventional analytical approach and composite systems were envisaged as providing an accessible yet flexible method of developing electrochemical sensors for discrete probe and flow systems. The basic procedure has been characterization and optimized for a range of analytes such as neurotransmitters (Chapter 5), anti-oxidants (Chapter 6), purine metabolites (Chapter 8) and phosphate (Chapter 9). Each chapter highlights a different aspect and applicability of the composite and go from simple physical surface modification (Chapter 5) to the incorporation of chemical agents (Chapter 6) and more complex systems such as enzymes (Chapters 8 and 9)

Disposable electrochemical flow cells for catalytic adsorptive stripping voltammetry (CAdSV) at a bismuth film electrode (BiFE)

Catalytic adsorptive stripping voltammetry (CAdSV) has been demonstrated at a bismuth film electrode (BiFE) in an injection-moulded electrochemical micro-flow cell. The polystyrene three-electrode flow cell was fabricated with electrodes moulded from a conducting grade of polystyrene containing 40% carbon fibre, one of which was precoated with Ag to enable its use as an on-chip Ag/AgCl reference electrode. CAdSV of Co(II) and Ni(II) in the presence of dimethylglyoxime (DMG) with nitrite employed as the catalyst was performed in order to assess the performance of the flow cell with an in-line plated BiFE. The injection-moulded electrodes were found to be suitable substrates for the formation of BiFEs. Key parameters such as the plating solution matrix, plating flow rate, analysis flow rate, solution composition and square-wave parameters have been characterised and optimal conditions selected for successful and rapid analysis of Co(II) and Ni(II) at the ppb level. The analytical response was linear over the range 1 to 20 ppb and deoxygenation of the sample solution was not required. The successful coupling of a microfluidic flow cell with a BiFE, thereby forming a “mercury-free” AdSV flow analysis sensor, shows promise for industrial and in-the-field applications where inexpensive, compact, and robust instrumentation capable of low-volume analysis is required

New Directions in Screen Printing and Related Fabrication Processes

This thesis reports the development of screen printed electrodes and associated fabrication processes in order to develop and understand new electrochemical based sensors. There are three main sections to this thesis. In the first part, an overview of sensors, in particular electrochemical sensors, that are commercially available and their current problems and limitations with conventional electrodes and electrode materials is discussed. Second, an introduction into screen printing and their advantages are given. The full process by which these next generation electrodes are manufactured is thoroughly described followed by examples of screen printed-electrodes and their powerful application as well as their low detection limits which compare well to existing literature on the market. The first example of a copper (II) oxide screen-printed electrode is reported, which is characterised with microscopy and its efficiency for the electrochemical sensing of glucose, maltose, sucrose and fructose is explored. It is shown that the non-enzymatic electrochemical sensing of glucose with cyclic voltammetry and amperometry is possible with low micro-molar up to milli-molar glucose readily detectable, which compares competitively with nano-catalyst modified electrodes. An additional benefit of this approach is that metal oxides with known oxidation states can be incorporated into the screen-printed electrodes allowing one to identify exactly the origin of the observed electro-catalytic response which is difficult when utilising metal oxide modified electrodes formed via electro-deposition techniques which result in a mixture of metal oxides/oxidation states. These next generation screen printed electrochemical sensing platforms provide a simplification offering a novel fabrication route for the mass production of electro-catalytic sensors for Analytical and Forensic applications. Other examples such as, bespoke screen printed electrodes which can be used as a template to produce randomly dispersed electro-catalytic micro-domains for analytical sensing purposes, are also shown to further demonstrate the applications and utility of screen printed electrodes. The final section focuses on electrode design. It is demonstrated that the electron transfer properties of disposable screen-printed electrodes can be readily tailored via the introduction of a polymeric formulation into the ink used in their fabrication. This approach allows the role of the binder on the underpinning electrochemical properties to be explored and quantified for the first time, allowing the electrochemical reactivity of the screen-printed electrodes to be tailored from that of edge plane-like to basal plane-like reactivity of highly ordered pyrolytic graphite. Building on this fundamental study of the origin of electron transfer at these novel electrodes, the first example of “Cosmetic Electrochemistry” is demonstrated where a commercially available cosmetic product, a deodorant, can be used to confer microelectrode behaviour on a macroelectrode. Proof-of-concept is shown that a graphite screen-printed electrode can be sprayed with an off-the-shelf cosmetic product and within seconds is ready to use. The polymer contained within the cosmetic product partially blocks the graphite screen-printed electrode surface leaving the underlying graphite electrode exposed in the form of graphite micron-sized sites which are randomly distributed across the electrode surface. The creation of microdomain sites enhance mass transport of the target analyte and it is shown that the electroanalytical performance of the cosmetically modified electrode, via the cathodic stripping of lead, could achieve a similar performance to current state-of-the-art methodologies. Further examples are also reported with the introduction of plaster-trodes where a commercially available plaster is electrolytically modified with electrocatalytic material and is used to detect various alcohol

Cheap and disposable gold and silver electrodes: Trends in the application of compact discs and digital versatile discs for electroanalytical chemistry

© 2017 Increasingly more reports have focused on the use of digital versatile discs (DVDs) and compact discs (CDs) for the fabrication of electrodes. The majority of discs use Al to reflect the laser. However, a notable percentage utilise Au or Ag. This layer can be mechanically or chemically exposed allowing for the economic fabrication of otherwise expensive Ag and Au electrodes. Cleaning steps are not required due to the layer's mirror like surface. Mass production of these discs means they are available, reproducible and disposable. Modifications can be made by laser, inkjet printing, etching or xurography. Self-assembled monolayers and the attachment of functional groups can also be made. This review (97 references and 6 figures) is divided into four sections. The first describes the development of these electrodes and their fabrication and modification. The next three sections focused on applications for the determination of metal ions, biomedical and environmental analysis

Recommendations for the Determination of Nutrients in Seawater to High Levels of Precision and Inter-Comparability using Continuous Flow Analysers

The Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP) brings together scientists with interests in physical oceanography, the carbon cycle, marine biogeochemistry and ecosystems, and other users and collectors of ocean interior data to develop a sustained global network of hydrographic sections as part of the Global Ocean Climate Observing System. A series of manuals and guidelines are being produced by GO-SHIP which update those developed by the World Ocean Circulation Experiment (WOCE) in the early 1990s. Analysis of the data collected in WOCE suggests that improvements are needed in the collection of nutrient data if they are to be used for determining change within the ocean interior. Production of this manual is timely as it coincides with the development of reference materials for nutrients in seawater (RMNS). These RMNS solutions will be produced in sufficient quantities and be of sufficient quality that they will provide a basis for improving the consistency of nutrient measurements both within and between cruises. This manual is a guide to suggested best practice in performing nutrient measurements at sea. It provides a detailed set of advice on laboratory practice for all the procedures surrounding the use of 1 gas-segmented continuous flow analysers (CFA) for the determination of dissolved nutrients (usually ammonium, nitrate, nitrite, phosphate and silicate) at sea. It does not proscribe the use of a particular instrument or related chemical method as these are well described in other publications. The manual provides a brief introduction to the CFA method, the collection and storage of samples, considerations in the preparation of reagents and the calibrations of the system. It discusses how RMNS solutions can be used to “track” the performance of a system during a cruise and between cruises. It provides a format for the meta-data that need to be reported along side the sample data at the end of a cruise so that the quality of the reported data can be evaluated and set in context relative to other data sets. Most importantly the central manual is accompanied by a set of nutrient standard operating procedures (NSOPs) that provide detailed information on key procedures that are necessary if best quality data are to be achieved consistently. These cover sample collection and storage, an example NSOP for the use of a CFA system at sea, high precision preparation of calibration solutions, assessment of the true calibration blank, checking the linearity of a calibration and the use of internal and externally prepared reference solutions for controlling the precision of data during a cruise and between cruises. An example meta-data report and advice on the assembly of the quality control and statistical data that should form part of the meta-data report are also given