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Water is a precious resource that is under threat from a number of pressures, including release of toxic compounds that can have damaging effect on ecology and human health. The current methods of water quality monitoring are based on sample collection and analysis at dedicated laboratories. This can provide an incomplete picture of the status of the water body as pollution events can be missed. Recently, electrochemical based methods have attracted a lot of attention for environmental sensing owing to their versatility, sensitivity and compatible integration with cost effective, smart and portable readout systems. In the present work, we report on the fabrication and characterization of platinum interdigitated microband electrodes arrays, and their application for trace detection of copper. Using square wave voltammetry after acidification with mineral acids, a limit of detection of 0.8 μg/L was achieved. Copper detection was also under taken on river water samples and compared with standard analytical techniques. The possibility of controlling the pH at the surface of the sensors – thereby avoiding the necessity to add mineral acids – was investigated. By applying potentials driving the water splitting reaction at one comb on the sensors electrode (the protonator), it was possible to lower the pH in the vicinity of the sensing electrode. Detection of standard copper solutions down to 5 μg/L using this technique is reported. This reagent free method of detection opens the way for autonomous, in situ monitoring of pollutants in water bodies.

Biocomputing systems based on engineered bacteria can lead to novel tools for environmental monitoring and detection of metabolic diseases. In this paper, we propose a Bacterial Molecular Computing on a Chip (BMCoC) using microfluidic and electrochemical sensing technologies. The computing can be flexibly integrated into the chip, but we focus on engineered bacterial AND Boolean logic gate and ON-OFF switch sensors that produces secondary signals to change the pH and dissolved oxygen concentrations. We present a prototype with experimental results that shows the electrochemical sensors can detect small pH and dissolved oxygen concentration changes created by the engineered bacterial populations' molecular signals. Additionally, we present a theoretical model analysis of the BMCoC computation reliability when subjected to unwanted effects, i.e., molecular signal delays and noise, and electrochemical sensors threshold settings that are based on either standard or blind detectors. Our numerical analysis found that the variations in the production delay and the molecular output signal concentration can impact on the computation reliability for the AND logic gate and ON-OFF switch. The molecular communications of synthetic engineered cells for logic gates integrated with sensing systems can lead to a new breed of biochips that can be used for numerous diagnostic applications., 11 pages, 6 figures

Global food production needs to increase in order to meet the demands of an ever growing global population. As resources are finite, the most feasible way to meet this demand is to minimize losses and improve efficiency. Regular monitoring of factors like animal health, soil and water quality for example, can ensure that the resources are being used to their maximum efficiency. Existing monitoring techniques however have limitations, such as portability, turnaround time and requirement for additional reagents. In this work, we explore the use of micro- and nano-scale electrode devices, for the development of an electrochemical sensing platform to digitalize a wide range of applications within the agri-food sector. With this platform, we demonstrate the direct electrochemical detection of pesticides, specifically clothianidin and imidacloprid, with detection limits of 0.22 ng/mL and 2.14 ng/mL respectively, and nitrates with a detection limit of 0.2 µM. In addition, interdigitated electrode structures also enable an in-situ pH control technique to mitigate pH as an interference and modify analyte response. This technique is applied to the analysis of monochloramine, a common water disinfectant. Concerning biosensing, the sensors are modified with bio-molecular probes for the detection of both bovine viral diarrhea virus species and antibodies, over a range of 1 ng/mL to 10 µg/mL. Finally, a portable analogue front end electronic reader is developed to allow portable sensing, with control and readout undertaken using a smart phone application. Finally, the sensor chip platform is integrated with these electronics to provide a fully functional end-to-end smart sensor system compatible with emerging Agri-Food digital decision support tools.

We report a two-step electrodeposition process incorporating glucose oxidase onto a platinum- modified gold microband electrode with an o-phenylenediamine and ß-cyclodextrin mixture. The bare microband electrodes were fabricated on silicon using standard microfabrication methods i.e. lithography and etching techniques. The two-step electrode modification process was characterized using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. The enzymatic based microband biosensor exhibited a linear response to glucose from 2.5-15 mM using both linear sweep voltammetry and chronoamperometric measurements in buffer based solutions. The resulting miniaturized glucose sensor presented a number of advantages such as ease of use, fast response time, measuring within physiologically relevant glucose concentrations in addition to sensing in small sample volumes without the need for an external counter and reference electrode. The biosensor performance was tested in 30 µl volumes of undiluted fetal bovine serum. Whilst a reduction in signal was evident within 100 % serum samples, the sensor achieved linear glucose detection with increasing glucose concentrations (2-12 mM).

Disinfection of water systems by chloramination is a method frequently used in North America as an alternative to chlorination. In such a case, monochloramine is used as the primary chlorine source for disinfection. Regular monitoring of the residual concentrations of this species is essential to ensure adequate disinfection. An amperometric sensor for monochloramine would provide fast, reagent-free analysis; however, the presence of dissolved oxygen in water complicates sensor development. In this work, we used in-situ pH control as a method to eliminate oxygen interference by conversion of monochloramine to dichloramine. Unlike monochloramine, the electrochemical reduction of dichloramine occurs outside the oxygen reduction potential window and is therefore not affected by the oxygen concentration. Potential sweep methods were used to investigate the conversion of monochloramine to dichloramine at pH 3. The pH control method was used to calibrate monochloramine concentrations between 1 and 10 ppm, with a detection limit of 0.03 ppm. Tests were carried out in high alkalinity samples, wherein it was found that the sensitivity of this method effectively remained unchanged. Monochloramine was also quantified in the presence of common interferents (copper, phosphate, and iron) which also had no significant impact on the analysis.

In electroanalysis, solution pH is a critical parameter that often needs to be adjusted and controlled for the detection of particular analytes. This is most commonly performed by the addition of chemicals, such as strong acids or bases. Electrochemical in-situ pH control offers the possibility for the local adjustment of pH at the point of detection, without additional reagents. FEA simulations have been performed to guide experimental design for both electroanalysis and in-situ control of solution pH. No previous model exists that describes the generation of protons at an interdigitated electrode array in buffered solution with one comb acting as a protonator, and the other as the sensor. In this work, FEA models are developed to provide insight into the optimum conditions necessary for electrochemical pH control. The magnitude of applied galvanostatic current has a direct relation to the flux of protons generated and subsequent change in pH. Increasing the separation between the electrodes increases the time taken for protons to diffuse across the gap. The final pH achieved at both, protonators and sensor electrodes, after 1 second, was shown to be largely uninfluenced by the initial pH of the solution. The impact of buffer concentration was modelled and investigated. In practice, the pH at the electrode surface was probed by means of cyclic voltammetry, i.e., by cycling a gold electrode in solution and identifying the potential of the gold oxide reduction peak. A pH indicator, methyl red, was used to visualise the solution pH change at the electrodes, comparing well with the model’s prediction

A sensitive and selective electrochemical sensor, based on reduced graphene oxide and gold nanoparticles obtained by simple co-electrodeposition, was developed for the detection of uric acid and ascorbic acid. Because of the electrochemical oxidation of both uric and ascorbic acid depending on the pH, the sensor performances were studied at different pH values. Excellent results were obtained for uric acid detection in a linear range from 10 to 500 µmol dm−3 with a sensitivity of 0.31 µA cm−2 µM−1. A limit of detection and quantification of 3.6 µM and 10.95 µmol dm−3, respectively, was calculated. Sensors showed good selectivity toward different interfering species present in the matrix of milk, fruit juice and urine (Na+, NH4+, Cl− and glucose). A simultaneous detection of uric acid and ascorbic acid was also carried out reaching a limit of detection of 2.26 and 5.63 µmol dm−3, respectively. Sensors were also validated measuring both acids in real samples of foods and body fluids (commercial milk and fruit juice and urine). Excellent results were achieved in good agreement with conventional techniques.

In electroanalysis, solution pH is a critical parameter that often needs to be tailored and controlled for the detection of particular analytes. This is most commonly performed by the addition of chemicals, such as strong acids or bases. Electrochemical in-situ pH control offers the possibility for the local adjustment of pH at the point of detection, without the need for additional reagents. Finite element analysis (FEA) simulations have been performed on interdigitated electrodes, to guide experimental design in relation to both electroanalysis and in-situ control of solution pH. No previous model exists that describes the generation of protons at an interdigitated electrode arrays in solution with one comb acting as a protonator, and the other as the sensor. In this work, FEA models are developed to provide insight into the optimum conditions necessary for electrochemical pH control. The magnitude of applied galvanostatic current has a direct relation to the flux of protons generated and subsequent change in pH. Increasing the separation between the electrodes increases the time taken for protons to diffuse across the gap between the electrode combs. The final pH achieved after 1 second, at both protonator and sensor electrodes, was shown to be largely uninfluenced by a solution's initial pH. The impact of buffer concentration was also modelled and investigated. In practice, the pH at the electrode surface was probed by means of cyclic voltammetry, i.e., to identify the potential of the gold oxide reduction peak. A pH indicator, methyl red, was used to visualise the solution pH change at the electrodes, comparing well with the model's prediction. Finally, we show that in-situ pH controlled detection of mercury in water, using square wave stripping voltammetry, is almost identical to samples acidified to pH 3.5 using nitric acid.

Bovine antibodies, such as immunoglobulin G (IgG), cannot pass the placental barrier and as such are not transferred from the mother to the foetus, in utero. Instead a calf must absorb antibodies following ingestion of colostrum postpartum. Failure of Passive Transfer (FPT) is a condition that predisposes calves to development of disease and increases the risk of mortality. Thus, continuous early monitoring of IgG absorption in a calf, within the first 6 to 12 hours of life, is imperative to allow faster treatment and prevent FPT. In this paper, we present the development of a label-free impedimetric immunosensor device for bovine IgG in serum and demonstrate its suitability to determine early FPT in new-born calves. The developed sensors were challenged to discriminate between new born calf sera, both pre- and post-colostrum feeding, and demonstrated efficient detection of IgG in under 15 minutes. Such a device could enable rapid determination of FPT, thereby improving calves' vitality and survival rate.

Residual free-chlorine concentration in water supplies is a key metric studied to ensure disinfection. High residual chlorine concentrations lead to unpleasant odours and tastes, while low concentrations may lead to inadequate disinfection. The concentration is most commonly monitored using colorimetric techniques which require additional reagents. Electrochemical analysis offers the possibility for in-line analysis without the need for additional reagents. Electrochemical-based detection of chlorine is influenced by the solution pH, which defines the particular chlorine ionic species present in solution. As such, controlling the pH is essential to enable electrochemical based detection of residual chlorine in water. To this end, we explore the application of solid state interdigitated electrodes to tailor the in-situ pH of a solution while simultaneously detecting free-chlorine. Finite element simulations and subsequent electrochemical characterization, using gold interdigitated microelectrode arrays, were employed to explore the feasibility of an in-situ pH control approach. In practice, the approach converted residual chlorine from an initial mixture of two species (hypochlorous acid and hypochlorite ion), to one species (hypochlorous acid). Chlorine detection was shown in water samples using this exploratory method, resulting in a two-fold increase in signal response, compared to measurements without pH control. Finally, tap water samples were measured using the in-situ pH control method and the results showed excellent correlation (within experimental error) with a commercial instrument, demonstrating the efficacy of the developed technique. This work establishes the possibility of deploying an electrochemical based reagent-free, in-line chlorine sensor required for water distribution networks.

This article explores recent advances in the development of electrochemical biosensors on microneedle platforms towards on-device sensing of biomarkers present in dermal interstitial fluid. The integration of a biosensor with a microneedle platform opens the possibility for minimally invasive bio-chemical detection or continuous monitoring within the dermal interstitial fluid. An introduction to interstitial fluid is provided placing emphasis on sampling methods that have been employed to extract and/or sample tissue fluid for analysis. We look briefly at microneedle technologies used to extract dermal interstitial fluid for subsequent analysis. Successive content will focus on microneedle technologies which have been integrated with electrochemical biosensors for the quantification of various metabolites, electrolytes and other miscellaneous entities known to be present in the dermal interstitial fluid. The review concludes with some of the key challenges and opportunities faced by this next-generation wearable sensing technology.

An electrochemical sensor for the detection of lead, mercury and copper in neutral solutions is described. The electrode is made of two distinct parallel gold interdigitated microband electrodes that can be polarized separately. Biasing one electrode “protonator” sufficiently positive to begin water electrolysis, results in the production of H+ ions which consequently drops the pH in the locality around the other second interdigitated “sensing” electrode. This decrease in pH permits the electodeposition (and consequent stripping) of metals at the sensing electrode without the need to acidify the whole test solution. In this work, the local pH can be adjusted from 1 to 7 in a stable and reproducible way by tailoring the applied potential to the protonator electrode. Using this approach, linear ranges for lead 10-100 ppb, copper 5-100 ppb and mercury 1-75 ppb, respectively were demonstrated which exhibit extremely high sensitivity. This technique allowed detection of these metals in a complex water matrix (river water) without sample pretreatment, with excellent results. The electrode reproducibility is high (RSD < 10%) and the metals can be co-detected when present all together. This is the first demonstration of the in-situ pH control for heavy metal detection using solid state sensors and will unable real time and in situ analysis of heavy metals by unskilled personnel in remote settings.

This work describes a flexible and portable data acquisition system that has been developed to interface to nano and ultra-micro scale electrochemical sensors at the point of use. It can perform a range of voltammetric tests, including Cyclic Voltammetry, Square Wave Voltammetry and Generator Collector Voltammetery. The data acquisition system interfaces to a smartphone, operates from a rechargeable battery and is of suitable form factor to ensure that it’s fully portable. By utilising commercially available components, this system has been developed to lower the barrier for entry for the development of emerging portable electrochemical sensing technologies at micro and nano scale. To show the full range of functionality of the system, a use case involving river water quality monitoring is presented through generation of a calibration curve, using a recently developed Tyndall National Institute ultra-microband electrochemical sensor, for the detection of dissolved oxygen in river water.

The use of Surface Enhanced Raman Spectroscopy in the development of low cost, portable sensor devices that can be used in the field for nitroguanidine neonicotinoid insecticide detection is appealing. However, a key challenge to achieving this goal is the lack of detailed analysis and vibrational assignment for the most popular neonicotinoids. To make progress towards this goal, this paper presents an analysis of the bulk Raman and SERS spectra of two neonicotinoids, namely clothianidin and imidacloprid. Combined with first principles simulations, this allowed assignment of all Raman spectral modes for both molecules. To our knowledge, this is the first report of SERS analysis and vibrational assignment of Clothianidin and a comprehensive assignment and analysis is provided for imidacloprid. Silver nanostructured surfaces were fabricated for qualitative SERS analysis, which provides the characteristic spectra of the target molecules, and demonstrates the ability of SERS to sense these molecules at concentrations as low as 1 ng/L. These detection limits are significantly lower than reported solid state electrochemical techniques and are on a par with high-end chromatographic-mass spectroscopy laboratory methods. These SERS sensors thus allow for the selective and sensitive detection of neonicotinoids, and provides complementary qualitative and quantitative data for the molecules. Furthermore, this technique can be adapted to portable devices for remote sensing applications. Further work focuses on integrating our device with an electronics platform for truly portable residue detection.

Bovine antibodies, such as immunoglobulin G (IgG), cannot pass the placental barrier and as such are not transferred from the mother to the foetus, in utero. Instead a calf must absorb antibodies following ingestion of colostrum postpartum. Failure of Passive Transfer (FPT) is a condition that predisposes calves to development of disease and increases the risk of mortality. Thus, continuous early monitoring of IgG absorption in a calf, within the first 24 hours of life, is imperative to allow faster treatment and prevent FPT. In this paper, we present the development of a label-free impedimetric immunosensor device for bovine IgG in serum and demonstrate its suitability to determine early FPT in new-born calves. The developed sensors were challenged to discriminate between new born calf sera, both pre- and post-colostrum feeding, and demonstrated efficent detection of IgG in under 15 minutes. Such a device could enable rapid determination of FPT, thereby improving calves’ vitality and survival rate

International audience; This paper presents the vision of the H2020 EU project SARMENTI whose objective is to develop an IoT device that monitors in real-time and in situ nutrients in the soil and gaseous emissions just above the soil, and provide advices to the farmer regarding appropriate fertilization strategies. The development methodology is presented here, the measurement requirements being established with end-users. Then the device architecture is summarized.

Gold interdigitated nanowire electrode arrays (INEAs) (∼100 nm wide, ∼50 nm high, ∼45 μm long and ∼500 nm spacing) on a Si/SiO2 chip substrate were fabricated and characterised. Arrays were employed in both non-generator-collector (non-GC) mode (one array electrically connected) and in generator-collector (GC) mode (both arrays electrically connected). In non-GC mode, the individual arrays were confirmed to behave as microelectrodes arising from linear diffusion to the total area of the array. By contrast, in GC-mode, arrays displayed steady-state electrochemical behaviour arising from enhanced diffusion to the nanowires and redox cycling (RC) between adjacent electrodes. Finite element simulations were investigated to explore the effect of altering connected and non-connected electrodes on the diffusional behaviour of the arrays with 500 nm separations. They correlated well with the experimental observations for the influence of the collector electrode potential on redox reactions taking place at the generator for a range of scan rates. The suitability of the gold INEAs towards iron sensing in water is also reported. A calibration curve is obtained for 0.5–40 μM (28–2234 μg L−1) Fe2+ with a limit of detection (LOD) of 0.01 μM (0.6 μg L−1) well below the permitted level in drinking water. Finally, iron determination in tap water using a standard addition technique is presented.

This paper demonstrates the reproducible fabrication of transparent Surface Enhanced Raman Scattering (SERS) substrates, fabricated by employing an aluminium soda can to template nanostructures on a flexible thermoplastic polymer surface, followed by deposition of a silver over layer. Electron microscopy and finite element modelling simulations strongly suggested the SERS response arose at regions of high electromagnetic field strength occurring between metallic clusters following illumination by monochromatic radiation. The sensors exhibited rapid, quantitative and high sensitivity, for example, 5 × 10−10 M (204 pg/mL) crystal violet detection in 10 min using a simple drop and dry method. We also show detection of glucose employing a chemically modified silver surface bearing a pre-deposited SAM layer. Furthermore, the transparent substrates permitted back excitation and collection through the substrate with corresponding spectra exhibiting clear and well-defined spectral SERS peaks. Finally, we present the detection of trace amounts of melamine in complex media solution (milk and infant formula). We benchmark the sensor performance using commercial analytical instrumentation (MS-MS) and show comparable sensitivity between the SERS substrates and MS-MS.

During in vitro culture, bereft of their optimal tissue context, tenocytes lose their phenotype and function. Considering that tenocytes in their native tissue milieu are exposed simultaneously to manifold signals, combination approaches (e.g. growth factor supplementation and mechanical stimulation) are continuously gaining pace to control cell fate during in vitro expansion, albeit with limited success due to the literally infinite number of possible permutations. In this work, we assessed the potential of scalable and potent physicochemical approaches that control cell fate (substrate stiffness, anisotropic surface topography, collagen type I coating) and enhance extracellular matrix deposition (macromolecular crowding) in maintaining human tenocyte phenotype in culture. Cell morphology was primarily responsive to surface topography. The tissue culture plastic induced the largest nuclei area, the lowest aspect ratio, and the highest focal adhesion kinase. Collagen type I coating increased cell number and metabolic activity. Cell viability was not affected by any of the variables assessed. Macromolecular crowding intensely enhanced and accelerated native extracellular matrix deposition, albeit not in an aligned fashion, even on the grooved substrates. Gene analysis at day 14 revealed that the 130 kPa grooved substrate without collagen type I coating and under macromolecular crowding conditions positively regulated human tenocyte phenotype. Collectively, this work illustrates the beneficial effects of combined physicochemical approaches in controlling cell fate during in vitro expansion., Graphical abstract Image 1

Monochloramine amperometric determination was investigated using a pH control method to eliminate dissolved oxygen as an interferent. This method allowed local pH conditions to become more acidic, causing the production of dichloramine. This species showed an onset of electro-reduction at 450 mV, far outside of the oxygen reduction region. Monochloramine was calibrated using this method and showed good linearity (0.99) and a limit of detection of 0.03 ppm.

Fabrication and characterization of polymer microneedle arrays, compatible with in-vivo glucose sensing, is described. The process generates a polymer microneedle electrode array comprised of an on-chip working, counter and reference electrodes. Glucose oxidase was entrapped in an o-phenylenediamine/ sulphonated-β-cyclodextrin polymer matrix at working electrodes The sensor array demonstrated glucose detection over the range of 0.5 – 19.5 mM. An interference study and a preliminary cytotoxicity study were carried to assess the sensors potential for future use in interstitial fluid.

Nanoelectrochemical sensors comprising of single gold nanowires or interdigitated nanowire arrays were simulated, designed and then fabricated on silicon chip substrates. Each chip comprised of six nanoscale electrodes (100 nm wide, 50 nm high and 45 μm long), on-chip counter & reference electrodes and an SD pinout. Finite element simulations, confirmed by experiment, suggested that electrolysing water, which increases H+ and OH-ions at the anode and cathode, respectively, would allow local pH control at interdigitated nanowire sensors. The interdigitated nanowire arrays also enabled generator-collector type measurements to be undertaken, providing more sensitive results and also the ability to tailor the chemistry temporally and spatially at sensor locations. SIRC behaviour was also observed when one comb of the interdigitated array was allowed to electrically float and the electrode array demonstrated enhanced sensitivity. Dissolved oxygen detection using nanowire arrays showed enhanced sensing when compared to state of the art sensors.

Interfacial metal-oxide systems with ultra-thin oxide layers are of high interest for their use in catalysis. The chemical activity of ultra-thin metal-oxide layers can be substantially enhanced compared to interfacial models with thicker oxide. In this study, we present a Density Functional Theory (DFT) investigation of the structure of ultra-thin rutile layers (one and two TiO2 layers) supported on TiN and the stability of water on these interfacial structures. The rutile layers are stabilized on the TiN surface through the formation of interfacial Ti-O bonds. Charge transfer from the TiN substrate leads to the formation of reduced Ti3+ cations in TiO2. The concentration of Ti3+ is proportionally higher in the ultra-thin oxide, compared to interfacial models with thicker oxide layers. The structure of the one-layer oxide slab is strongly distorted at the interface while the thicker TiO2 layer preserves the rutile structure. The energy cost for the formation of a single O vacancy in the one-layer oxide slab is only 0.5 eV with respect to the ideal interface. For the two-layer oxide slab, the introduction of several vacancies in an already non-stoichiometric system becomes progressively more favourable, which indicates the stability of the highly defective interfaces. Isolated water molecules dissociate when adsorbed at the TiO2 layers. At higher coverages, the preference is for molecular water adsorption. Our ab initio thermodynamics calculations show the fully water covered stoichiometric models as the most stable structure at typical ambient conditions. This behaviour is similar to that observed on thicker oxide in TiO2-TiN interfaces or pure TiO2 surfaces. In contrast, interfacial models with multiple vacancies are most stable at low (reducing) oxygen chemical potential values. The high concentration on reduced Ti3+ introduces significant distortions in the O-defective slab. Whereas, a water monolayer adsorbs dissociatively on the highly distorted 2-layer TiO1.75-TiN interface, where the Ti3+ states lying above the top of the valence band contribute to a significant reduction of the energy gap compared to the stoichiometric TiO2-TiN model. Our results provide a guide for the design of novel interfacial systems containing ultra-thin TiO2 with potential application as photocatalytic water splitting devices.

Introduction With the global population expected to grow to over 9.6 billion by 2050 it is a projected that a 50-60 % increase in food production will be required. In addition, the increasing wealth of the BRIC (Brazil, Russia, India and China) countries is driving the transition from traditional to more westernized high protein diets. A key challenge then, going forward, will be to close the food gap. This must be achieved against the backdrop of climate change & desertification, labor shortages and competition for energy, land & resources. It is clear then, that addressing this challenge will require the development of more efficient and sustainable food production techniques and processes. Digitizing the entire food chain using smart sensor systems would help enable such an approach. This convergence between the Internet of Things (IoT) and the agri-food industry requires sensor systems and technologies that provide real time data to producers and processers; required for rapid, but informed, decision making. To this end, we are using microelectronic fabrication approaches to develop advanced end-to-end chemical and bio-chemical nanosensor sensor systems specifically tailored to the needs of both producers and processors [1-3]. These sensor systems are being designed to be used by non-specialists and be rugged enough for field deployment [4, 5]. Sensor Development On-chip devices containing six gold microband electrodes, a gold counter and a platinum pseudo-reference electrodes were fabricated using standard nanofabrication processes on Si/SiO2 substrates as described in detail previously [6]. A custom built Teflon cell permit analysis of small sample volumes (~50 µL), see Fig 1. Gold contact pads were configured on-chip to permit electrical connection to the potentiostat via a microSD port. Chips could be easily plugged in/out enabling rapid analysis of multiple samples. Optical micrographs were acquired using a calibrated microscope (Axioskop II, Carl Zeiss Ltd.) with a charge-coupled detector camera (CCD; DEI-750, Optronics). Electrochemical experiments were carried out using an Autolab Potentiostat/ Galvanostat PGSTAT128N (Metrohm Ltd, Utrecht, The Netherlands) controlled by the Autolab NOVA software. All experiments employed a standard three-electrode cell configuration using a single gold nanoband as the working electrode, versus the on-chip gold counter and platinum pseudo-reference electrodes,. In this study, microband sensors were applied to the detection of Bovine IgG and anti-Fasciola antibodies in serum samples. On-chip microband electrodes were first cleaned using a mixed solvent clean process (acetone, isopropyl alcohol and DI water) for 15 minutes. Cyclic voltammetry was then employed for electropolymerisation of o-aminobenzoic acid (o-ABA, 50 mM in 0.5 M H2SO4) to create a carboxylic terminated polymer layer at the gold electrode surface. A fresh NHS/EDC mixture was prepared in 10 mM acetate buffer, pH 4.0 and subsequently deposited onto the polymerised electrodes, for approximately 30 min, to activate the surface. Concerning IgG, activated electrodes were modified with 1 ng/ml anti-Bovine IgG in 10 mM sodium acetate buffer, pH 4.0 (AB). Anti-IgG was incubated on the electrode for 15 min. Following deposition of these capture biomolecules, unbound active-sites on all electrodes were blocked with ethanolamine (1 M) for 20 minutes. A secondary blocking of 1 % NANNY care® goat based milk in PBS was used for the IgG assay, for a comparison. Results and Conclusions Electrochemical Impedance Spectroscopy (EIS) techniques allows for the monitoring of the increase of the Rct signal and was used to interrogate antigen binding. The reduction of the electron transfer causes an increase in the Rct as seen in Figure 2. Following exposure to igG antibodies an increase in impedance was observed. A semi-logarithmic relationship exists between the concentration of the target and the change in Rct. This correlates with the trend seen in the ELISA calibration plot. The Nyquist plot shows a much larger change in signal between each concentration of Bo IgG than the CV and thus EIS is widely used for evaluating immunosensors such as these. References [1] A. Wahl, S. Barry, K. Dawson, J. MacHale, A. Quinn, and A. O'Riordan, "Electroanalysis at ultramicro and nanoscale electrodes: a comparative study," Journal of The Electrochemical Society, vol. 161, no. 2, pp. B3055-B3060, 2014. [2] M. N. Hossain, J. Justice, P. Lovera, B. McCarthy, A. O’Riordan, and B. Corbett, "High aspect ratio nano-fabrication of photonic crystal structures on glass wafers using chrome as hard mask," Nanotechnology, vol. 25, no. 35, p. 355301, 2014. [3] N. C. Creedon, P. Lovera, A. Furey, and A. O’Riordan, "Transparent polymer-based SERS substrates templated by a soda can," Sensors and Actuators B: Chemical, vol. 259, pp. 64-74, 2018. [4] K. Dawson et al., "Fully integrated on-chip nano-electrochemical devices for electroanalytical applications," Electrochimica Acta, vol. 115, pp. 239-246, 2014. [5] P. Lovera et al., "Low-cost silver capped polystyrene nanotube arrays as super-hydrophobic substrates for SERS applications," Nanotechnology, vol. 25, no. 17, p. 175502, 2014. [6] A. Montrose, N. Creedon, R. Sayers, S. Barry, and A. O’riordan, "Novel single gold nanowire-based electrochemical immunosensor for rapid detection of bovine viral diarrhoea antibodies in serum," J. Biosens. Bioelectron, vol. 6, no. 3, pp. 1-7, 2015. Figure 1

Water is a precious resource that is under threat from a number of pressures, including, for example, release of toxic compounds, that can have damaging effect on ecology and human health. The current methods of water quality monitoring are based on sample collection and analysis at dedicated laboratories. Recently, electrochemical-based methods have attracted a lot of attention for environmental sensing owing to their versatility, sensitivity and their ease of integration with cost effective, smart and portable readout systems. In the present work, we report on the fabrication and characterization of platinum-based interdigitated microband electrodes arrays, and their application for trace detection of copper. Using square wave voltammetry after acidification with mineral acids, a limit of detection of 0.8 μg/L was achieved. Copper detection was also undertaken on river water samples and compared with standard analytical techniques. The possibility of controlling the pH at the surface of the sensors—thereby avoiding the necessity to add mineral acids—was investigated. By applying potentials to drive the water splitting reaction at one comb of the sensor’s electrode (the protonator), it was possible to lower the pH in the vicinity of the sensing electrode. Detection of standard copper solutions down to 5 μg/L (ppb) using this technique is reported. This reagent free method of detection opens the way for autonomous, in situ monitoring of pollutants in water bodies.

Herein we report on the development of an electrochemical sensor for silver ions detection in tap water using anodic sweep voltammetry with in-situ pH control; enabled by closely spaced interdigitated electrode arrays. The in-situ pH control approach allowed the pH of a test solution to be tailored to pH 3 (experimentally determined as the optimal pH) by applying 1.65 V to a protonator electrode with the subsequent production of protons, arising from water electrolysis, dropping the local pH value. Using this approach, an initial proof-of-concept study for silver detection in sodium acetate was undertaken where 1.25 V was applied during deposition (to compensate for oxygen production) and 1.65 V during stripping. Using these conditions, calibration between 0.2 and 10 μM was established with the silver stripping peak ∼0.3 V. The calculated limit of detection was 13 nM. For the final application in tap water, 1.65 V was applied to a protonator electrode for both deposition and stripping of silver. The chloride ions, present in tap water (as a consequence of adding chlorine during the disinfection process) facilitated silver detection and caused the striping peak to shift catholically to ∼0.2 V. The combination of the complexation of silver ions with chloride and in-situ pH control resulted in a linear calibration range between 0.25 and 2 μM in tap water and a calculated limit of detection of 106 nM without the need to add acid or supporting electrolytes.

Contamination of water with nitrate ions is a significant problem that affects many areas of the world. The danger from nitrates is not so much their toxicity, rather low, as their transformation into nitrites and in particular into nitrosamines, substances considered to be a possible carcinogenic risk. For this reason, European legislation has set the maximum permissible concentration of nitrates in drinking water at 44 mg/l. Thus, it is clear that a continuous monitoring of nitrate ions is of high technological interest but it must be rapid, easy to perform and directly performed in situ. Electrochemical detection is certainly among the best techniques to obtain the above requirements. In particular, in this work we have developed a nanostructured sensor based on array of copper nanowires obtained with the simple method of galvanic deposition. The nanostructured sensors have a very short response time with a detection limit less than 10 M. Different interfering species were tested finding a negligible effect except for the chlorine ions. However, this problem has been solved by removing chlorine ions from the water through a simple precipitation of chloride compounds with low solubility. Nanostructured sensors were also used to analyze real water samples (rain, river and drinking water). In the case of drinking water, we have measured a concentration of nitrate ions very close to the that measured by conventional laboratory techniques.

We report on the use of a spectroelectrochemical method for the investigation of mercury amalgamation on gold nanorods. Hg2+ was electrochemically reduced at gold nanorod electrodes, and the consequent optical changes resulting from deposition of mercury were monitored by dark-field microscopy. Nanorods displayed marked scattering color transitions from red to green and longitudinal surface plasmon resonance (LSPR) blue-shifts up to 197 nm. Corresponding cathodic voltammograms showed strong reduction peaks at potentials which were attributed to Hg2+ reduction. The highest optical blue-shifts were observed for working electrodes constituted by well-separated gold nanorods deposited on ITO substrates, which also showed transition from diffusion-limited to steady-state electrochemical behavior. Theoretical simulations were carried out to support experimental results and to obtain further insight into the diffusional behavior of mercury reduction at nanorod electrodes. Real time observation of the amalgamation process was performed by monitoring the evolution of spectral response from single nanorods in the presence of Hg2+ and subjected to either linear sweep voltammetry or chronoamperometry. The analysis confirmed a direct correlation between the occurrence of spectral changes and the formation of an amalgam resulting from deposition and subsequent diffusion of reduced mercury into the nanorods. This work shows the potential of this method for elucidation of reaction mechanisms occurring at nanoscale electrodes and for sensitive detection of mercury for environmental applications.

In utilising metal surfaces that are in constant contact with each other, metal-on-metal (MoM) surgical implants present a unique challenge, in the sense that their necessity is accompanied by the potential risk of wear particle generation, metal ion release and subsequent patient toxicity. This is especially true of orthopaedic devices that are faulty and subject to failure, where the metal surfaces undergo atypical degradation and release even more unwanted byproducts, as was highlighted by the recent recall of orthopaedic surgical implants. The aim of this review is to examine the area of metallosis arising from the wear of MoM articulations in orthopaedic devices, including how the surgical procedures and detection methods have advanced to meet growing performance and analytical needs, respectively.

Quantitative point-of-care (POC) devices are the next generation for serological disease diagnosis. Whilst pathogen serology is typically performed by centralized laboratories using Enzyme-Linked ImmunoSorbent Assay (ELISA), faster on-site diagnosis would infer improved disease management and treatment decisions. Using the model pathogen Bovine Herpes Virus-1 (BHV-1) this study employs an extended-gate field-effect transistor (FET) for direct potentiometric serological diagnosis. BHV-1 is a major viral pathogen of Bovine Respiratory Disease (BRD), the leading cause of economic loss ($2 billion annually in the US only) to the cattle and dairy industry. To demonstrate the sensor capabilities as a diagnostic tool, BHV-1 viral protein gE was expressed and immobilized on the sensor surface to serve as a capture antigen for a BHV-1-specific antibody (anti-gE), produced in cattle in response to viral infection. The gE-coated immunosensor was shown to be highly sensitive and selective to anti-gE present in commercially available anti-BHV-1 antiserum and in real serum samples from cattle with results being in excellent agreement with Surface Plasmon Resonance (SPR) and ELISA. The FET sensor is significantly faster than ELISA (

peer-reviewed This data article contains data related to the research article entitled “Substrate topography: A valuable in vitro tool, but a clinical red herring for in vivo tenogenesis” [1]. We report measurements on tenocyte viability, metabolic activity and proliferation on substrates with different topographies. We also report the effect of substrates with different topographies on host cells in a subcutaneous model.

ObjectivesThe BASHH guidelines recommend molecular tests to aid diagnosis of Trichomonas vaginalis (TV) infection; however many clinics continue to use relatively insensitive techniques (pH, wet-prep microscopy (WPM) and culture). Our objectives were to establish a laboratory pathway for TV testing with the Becton-Dickinson Qx (BDQx) molecular assay, to determine TV prevalence and to identify variables associated with TV detection.MethodsA prospective study of 901 women attending two urban sexual health services for STI testing was conducted. Women were offered TV BDQx testing in addition to standard of care. Data collected were demographics, symptoms, results of near-patient tests and BDQx results for TV, Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC). Women with any positive TV result were treated and followed up for test of cure (TOC).Results901 women had a TV BDQx test. 472 (53%) were white, 143 (16%) black and 499 (55%) were symptomatic. Infections detected by BDQx were: 11 TV (1.2%), three GC (0.3%) and 44 CT (4.9%). Of the 11 BDQx-detected TV infections, 8 (73%) were in patients of black ethnicity. Of these, four of seven cases (57%) were WPM-positive. All patients received treatment and nine of nine (100%) were BDQx-negative at TOC. In univariate analysis, only black ethnicity was associated with likelihood of a positive TV BDQx result (relative risk (RR) 10.2 (95% CI 2.15 to 48.4)).ConclusionsThe use of the BDQ enhanced detection of TV in asymptomatic and symptomatic populations. Cost-effective implementation of the test will rely on further work to reliably detect demographic and clinical variables that predict positivity.

This work describes a flexible and portable data acquisition system that has been developed to interface to nano and ultra-micro scale electrochemical sensors at the point of use. It can perform a range of voltammetric tests, including Cyclic Voltammetry, Square Wave Voltammetry and Generator Collector Voltammetery. The data acquisition system interfaces to a smartphone, operates from a rechargeable battery and is of suitable form factor to ensure that it’s fully portable. By utilising commercially available components, this system has been developed to lower the barrier for entry for the development of emerging portable electrochemical sensing technologies at micro and nano scale. To show the full range of functionality of the system, a use case involving river water quality monitoring is presented through generation of a calibration curve, using a recently developed Tyndall National Institute ultra-microband electrochemical sensor, for the detection of dissolved oxygen in river water.

In veterinary medicine, diagnostic tools enabling early detection of infectious disease in cattle could play a pivotal role in the control and eradication of bovine viral diarrhoea (BVD). Early identification of cattle persistently infected with bovine viral diarrhoea virus (BVDV) is critical for early diagnosis and isolation of the animal from a susceptible herd. The immediate availability of electronic test results to a veterinarian on-farm, would eliminate the need to submit samples to a commercial laboratory thereby improving animal therapeutic outcomes considerably. An impedimetric silicon chip-based biosensor platform, containing six gold nanoband electrodes as six individual sensors, was developed in this study for detection of BVD disease target molecules. Gold nanoband electrodes were first coated with an electrodeposited polymer and then modified with either monoclonal antibodies or Erns protein, for the subsequent detection of BVD virus and antibodies in whole serum, respectively. We demonstrate that the nanoband sensors have sufficient sensitivity and specificity for serological detection of both targets, with a low time-to-result (20 minutes). All serological samples were benchmarked against, and in complete agreement with, gold standard commercial ELISA methods. These initial proof-of-concept findings are of particular significance for potential on-farm point of use applications, where rapid analysis times and specificity are required to permit early diagnostics by veterinarians.

We report on the novel fabrication and characterisation of plasmonic arrays of elliptical nanohole, and their use for refractive index based sensing. The substrates were fabricated using nanoimprint lithography into a chromium hard mask followed by transfer of the patterns into the underlying gold layer by dry etching—a combination of processes amendable to mass manufacturing. 3D-FDTD simulations were undertaken and showed the transmission spectrum was dependant upon the polarisation of the incident light, with a series of minima that can be attributed to plasmonic effects on the gold/water or gold/substrate interfaces. Each polarisation showed two peaks on the gold/water interface, one in the visible and one in the near-infrared part of the spectrum. Simulated electric field profiles showed that the electric field in the infrared propagates deep in the bulk while the one in the visible was more tightly bound to the surface. Experimental transmission spectra of the fabricated samples showed good agreement with the simulated ones. Bulk refractive index experiments were carried out and sensitivities of 293 nm/RIU and 414 nm/RIU were obtained for the two spectral features of interest when the polarisation was along the long axis of the elliptical nanohole for the visible and infrared features, respectively, and 293 nm/RIU and 323 nm/RIU measured when the polarisation was along the short axis of the nanohole.

Orthogonal sensing of nitroguanidine neonicotinoid insecticides is explored by combining both surface enhanced Raman Spectroscopy (SERS) and nanoelectrochemical analysis. Silver nanostructured surfaces were fabricated for qualitative SERS-based detection of clothianidin and imidacloprid, to provide characteristic molecular spectra of the molecules, Density functional theory (DFT) studies were undertaken to assign the Raman active vibrational modes for clothianidin and imidacloprid. The Raman spectrum of clothianidin is assigned for the first time. Discrete arrays of on-chip fully integrated gold nanowire electrodes were developed to provide quantitative detection of the insecticides. Square-wave voltammetry permits highly sensitive and rapid determination of the neonicotinoids. Two electrochemical reduction peaks for clothianidin and imidacloprid were identified, and detection limits of 0.22 ng/mL and 2.15 ng/mL were subsequently achieved, respectively. These detection limits are significantly lower than previously reported electrochemical techniques and are comparable with significantly more complex and expensive chromatographic methods. By employing both techniques in combination, SERS characterisation provides the unique molecular fingerprint of each pesticide, while the nanoelectrochemical measurement provides a quantitative determination to ultra-low limits of detection. This combined spectro-electrochemical approach has the potential to significantly reduce false positives, that arise in remote monitoring, greatly increasing the robustness and credibility of these measurements.

In this work, interdigitated arrays of nanowire electrodes are used with one array acting as the working electrode while the other is used to generate the required protons. Finite element simulations of the pH control electrodes were performed to provide insight on the generation and subsequent diffusion of protons. This informed the inter-tine spacing of the electrodes used.. This electrochemical pH control method was then used to enable the detection of analytes of interest.

Silver is more often used in consumer products and that in consequence leads to its release into the water. Quick and easy methods for detection of silver ions in water are required. In present work electrochemical-based sensor was developed for detection of silver ions in aqueous solutions. The solution's pH for detection was lowered either with nitric acid or reagent-free using localized pH control. Linear regions for the current peak height against the silver concentration have been found between 100–1000 nM and 250–5000 nM for samples acidified with nitric acid and using localized pH control respectively. In present work the limit of detection was lower than comparing to similar work without the need to modify the electrode.

This paper describes a unique method of developing a device capable of interfacing to interdigitated nanowire electrochemical sensors using a potentiostat and a digital to analog converter. As a test case, a system is described, which was developed using commercial components, to perform cyclic voltammograms using the generator collector method. The system was verified through the detection of ferrocene monocarboxylic acid and comparing results against benchtop laboratory potentiostats.

© 2018 American Chemical Society. Titanium nitride (TiN) surfaces can oxidize, and the growth of a TiOx layer on the surface along with the likely presence of water in the surrounding environment can modify the properties of this widely used coating material. The present density functional theory study, including Hubbard + U correction (DFT+U), investigates the stability of adsorbed water at TiO2-TiN interfaces with different defects that serve as a model for an oxide layer grown on a TiN surface. Surface free energy calculations show the stability of a perfect TiN-TiO2 interface at regular O pressures, while oxygen vacancy-rich TiO1.88-TiN is more favorable at reducing conditions. An isolated water is preferentially adsorbed dissociatively at perfect and oxygen-defective interfaces, while molecular adsorption is more stable at higher coverages. The adsorption energy is stronger at the oxygen-defective interfaces which arise from the high concentration of reduced Ti3+ and strong interfacial atomic relaxations. Ab initio atomistic thermodynamics show that water will be present at high coverage on TiO2-TiN interfaces at ambient conditions, and the pristine interface is only stable at very low pressure of O and H2O. The results of these DFT+U simulations are important for the fundamental understanding of wettability of interfacial systems involving metal oxides.

This paper describes a low cost portable point of test data acquisition system, made of commercial components, that was developed to interface to electrochemical sensors. The proposed system has demonstrated that it can support cyclic voltammetry, square wave voltammetry and collector generator voltammetry, with dual electrode control. The system has demonstrated its capability to detect a range of ferrocene monocarboxylic acid concentrations using nanowire electrochemical sensors, while benchmarking the results against dedicated laboratory based equipment. This work has identified and highlighted the unique challenges of interfacing to electrochemical sensors.

Titanium Nitride (TiN) surfaces can oxidise and the growth of a TiOx layer on the surface along with the likely presence of water in the surrounding environment can modify the properties of this widely used coating material. The present Density Functional Theory study, including Hubbard +U correction (DFT+U), investigates the stability of adsorbed water at TiO2-TiN interfaces with different defects, that serve as a model for an oxide layer grown on a TiN surface. Surface free energy calculations show the stability of perfect TiN-TiO2 interface at regular O pressures, while oxygen vacancy-rich TiO1.88–TiN is more favourable at reducing conditions. An isolated water is preferentially adsorbed dissociatively at perfect and oxygen defective interfaces while molecular adsorption is more stable at higher coverages. The adsorption energy is stronger at the oxygen defective interfaces which arises from the high concentration of reduced Ti3+ and strong interfacial atomic relaxations. Ab initio atomistic thermodynamics show that water will be present at high coverage on TiO2-TiN interfaces at ambient conditions and the pristine interface is only stable at very low pressure of O and H2O. The results of these DFT+U simulations are important for the fundamental understanding of wettability of interfacial systems involving metal oxides.

Aim: Topographically modified substrates are increasingly used in tissue engineering to enhance biomimicry. The overarching hypothesis is that topographical cues will control cellular response at the cell–substrate interface. Materials & methods: The influence of anisotropically ordered poly(lactic-co-glycolic acid) substrates (constant groove width of ˜1860 nm; constant line width of ˜2220 nm; variable groove depth of ˜35, 306 and 2046 nm) on in vitro and in vivo osteogenesis were assessed. Results & discussion: We demonstrate that substrates with groove depths of approximately 306 and 2046 nm promote osteoblast alignment parallel to underlined topography in vitro. However, none of the topographies assessed promoted directional osteogenesis in vivo. Conclusion: 2D imprinting technologies are useful tools for in vitro cell phenotype maintenance.

New approaches to enable more effective management of diabetes mellitus, such as continuous glucose monitoring are being developed both to prevent unstable episodes of hypo or hyper glycaemia and also to provide an improved user experience. One emerging approach to realize these requirements is to fabricate a minimally invasive transdermal sensor for the direct in vivo detection of glucose in the interstitial fluid. Microneedles – sharp, microscopic structures measuring less than 1 mm in length – have been previously employed to allow painless penetration of the stratum corneum for delivery of drugs and vaccines. In this work we present, ultra sharp gold coated polymer microneedle arrays (sub micron tip radii) which are fabricated using a low cost polymer replication approach. Critical dimensions of the microneedle arrays are characterized using a combination of optical and scanning electron microscopies. Fabricated microneedle devices are characterized by cyclic voltammetry to explore functionality. The voltammetric detection of glucose is performed using ferrocene monocarboxylic acid as an oxidising mediator in the presence of glucose oxidase. The biosensor can be applied to the quantification of glucose in the physiological range (2 – 13.5 mM). The sensors demonstrate high selectivity towards glucose with negligible interference from other oxidizable species including uric acid, ascorbic acid, mannose, fructose, salicylic acid (Aspirin) and acetaminophen (Paracetamol). This demonstrates potential future use of these microneedle devices for in vivo glucose detection. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0141510jss] All rights reserved.

A fully integrated system that combines extended gate field-effect transistor (EGFET)-based potentiometric biosensors and electrochemical impedance spectroscopy (EIS)-based biosensors has been demonstrated. This integrated configuration enables the sequential measurement of the same immunological binding event on the same sensing surface and consequently sheds light on the fundamental origins of sensing signals produced by FET and EIS biosensors, as well as the correlation between the two. Detection of both the bovine serum albumin (BSA)/anti-BSA model system in buffer solution and bovine parainfluenza antibodies in complex blood plasma samples was demonstrated using the integrated biosensors. Comparison of the EGFET and EIS sensor responses reveals similar dynamic ranges, while equivalent circuit modeling of the EIS response shows that the commonly reported total impedance change (ΔZtotal) is dominated by the change in charge transfer resistance (Rct) rather than surface capacitance (Csurface). Using electrochemical kinetics and the Butler-Volmer equation, we unveil that the surface potential and charge transfer resistance, measured by potentiometric and impedance biosensors, respectively, are, in fact, intrinsically linked. This observation suggests that there is no significant gain in using the FET/EIS integrated system and leads to the demonstration that low-cost EGFET biosensors are sufficient as a detection tool to resolve the charge information of biomolecules for practical sensing applications.

Novel poly(9,9-dioctlylfluorene) (PFO) nanofibers were fabricated by solution template wetting of anodic aluminum oxide (AAO) templates with a pore diameter of 25 nm. Individual nanofibers displayed a pronounced axially polarized luminescence with a typical emission dichroic ratio of 15 and low spread of the emissive species angular distribution. The strong optical characteristics were ascribed to intrachain reorientation of amorphous PFO to a more planar and elongated β-phase conformation induced by mechanical strain during polymer template pore infiltration. Absorption optical spectroscopy on nanofiber mats confirmed formation of 24% β-phase emissive segments, which dominated the nanofiber luminescence characteristics. X-ray diffraction measurements were used to confirm and quantify the extent of nanofiber internal molecular alignment.

Tetrodotoxin (TTX) is a naturally occurring toxin that has been responsible for human intoxications and fatalities. Its usual route of toxicity is via the ingestion of contaminated puffer fish which are a culinary delicacy, especially in Japan. TTX was believed to be confined to regions of South East Asia, but recent studies have demonstrated that the toxin has spread to regions in the Pacific and the Mediterranean. There is no known antidote to TTX which is a powerful sodium channel inhibitor. This review aims to collect pertinent information available to date on TTX and its analogues with a special emphasis on the structure, aetiology, distribution, effects and the analytical methods employed for its detection.

In this work, we report a fully integrated nanowire-based electrochemical device that enables a suite of highly sensitive electroanalytical techniques in small sample volumes at silicon chip substrates. A hybrid wafer-level lithography approach is employed whereby an array of twelve individually addressable discrete gold nanowire electrodes, written by electron beam lithography, along with on-chip gold counter and silver pseudo-reference electrodes are deposited on silicon chips. An inorganic silicon nitride passivation ensures the devices are compatible with both aqueous and organic media. Peripherally located probe pads enables facile and direct electrical connection to electrodes using a reusable push-pin interface within a bespoke sample holder. This approach eliminates the requirement for costly microelectronic packaging techniques and also the requirement for large volume sample analysis. Nanowire electrodes with highly reproducible dimensions and low surface roughness are routinely fabricated and display characteristic Ohmic responses during two-point I–V measurements. The magnitude and shape of the voltammetric responses of a model molecule ferrocene monocarboxylic acid at nanowire electrodes were found to be highly reproducible on different electrodes and chips from multiple wafers and fabrication runs. Quasi-steady-state electrochemical behaviour was demonstrated for scan rates up to 5000 mV s −1 , without any observed changes to the voltammetric shape, enabling the potential for reliable electroanalysis with a millisecond response time. Square wave voltammetry was applied to the detection of 2,4-dinitrotoluene in the absence of a supporting electrolyte. Devices exhibited excellent limit of detection of 7 ng mL −1 using pristine unmodified nanowire electrodes. Consequently, these integrated nano-electrochemical devices represent a platform excellently positioned for providing reliable, rapid electroanalytical sensing suitable for a wide range of analytical applications.