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Accurate and fast on-site detection of harmful microorganisms in food products is a key preventive step to avoid food-borne illness and product recall. In this study, screen-printed electrodes (SPEs) were functionalized via a facile strategy with surface imprinted polymers (SIPs). The SIP-coated SPEs were used in combination with the heat transfer method (HTM) for the real-time detection of Escherichia coli. The sensor was tested in buffer, with a reproducible and sensitive response that attained a limit of detection of 180 CFU/mL. Furthermore, selectivity was assessed by analyzing the sensor's response to C. sakazakii, K. pneumoniae and S. aureus as analogue strains. Finally, the device was successfully used for the detection of E. coli in spiked milk as proof-of-application, requiring no additional sample preparation. These results suggest the proposed thermal biosensor possesses the potential of becoming a tool for routine, on-site monitoring of E. coli in food safety applications.

An ultrahigh photosensitive diode was developed using a Cu-doped CeO2thin film through spray pyrolysis processing, which has made a unique contribution in the field of optoelectronic device fabrication process.

In this overview, we explore the electroanalytical sensing of the important chemical reagent hydrazine, highlighting the plethora of electrochemical sensing strategies utilised from the first reports in 1951 to the present day. It is observed that a large proportion of the work developing electrochemical sensors for hydrazine focus on the use of metallic nanoparticles and some other surface modifications, although we note that the advantages of such strategies are often not reported. The use of nanoparticle-modified electrodes to this end is explored thoroughly, indicating that they allow the same electrochemical response as that of a macroelectrode made of the same material, with clear cost advantages. It is recommended that significant studies exploring the surface coverage/number of nanoparticles are performed to optimise electroanalytical devices and ensure that thin-layer effects are not producing false observations through electrocatalysis. Development of these sensor platforms has begun to transition away from classical macroelectrodes, toward more mass producible supporting electrodes such as screen-printed and inkjet-printed electrodes. We suggest significant advances in this area are still to be found. The vast majority of developed electroanalytical sensors for hydrazine are tested in aqueous based environments, such as tap, river and industrial effluent waters. There is significant scope for development of hydrazine sensors for gaseous environments and biologically relevant samples such as blood, serum and urine, aiming to produce sensors for accurate occupational exposure monitoring. Finally, we suggest that the levels of publications with independent validation of hydrazine concentrations with other well-established laboratory-based measurements is lacking. We believe that improving in these areas will lead to the development of significant commercial products for the electroanalytical detection of hydrazine.

In this work, the electrochemical response of different morphologies (shapes) and dimensions of additively manufactured (3D-printing) carbon black (CB)/poly-lactic acid (PLA) electrodes are reported. The working electrodes (WE) are printed using standard non-conductive PLA based filament for the housing and commercial Protopasta (carbon black/PLA) filament for the electrode and connection parts. Discs, squares, equilateral triangles and six-point stars with varying working electrode (WE) widths from 2 to 10 mm are evaluated herein towards the well-known near-ideal outer sphere redox probe hexaamineruthenium(III) chloride (RuHex). The results obtained show that triangular and squared electrodes exhibit a faster heterogeneous electron transfer (HET) rate constant (

The effect of solvent ingress on additive manufacturing is reported.

In this minireview we overview the endeavors for the electroanalytical sensing of hydroxylamine.

Screen-printed electrodes (SPEs) are ubiquitous within the field of electrochemistry and are commonplace within the arsenal of electrochemists. Their popularity stems from their reproducibility, versatility, and extremely low-cost production, allowing their utilization as single-shot electrodes and thus removing the need for tedious electrode pretreatments. Many SPE studies have explored changing the working electrode composition and/or size to benefit the researcher's specific applications. In this paper, we explore a critical parameter of SPEs that is often overlooked; namely, we explore changing the length of the SPE connections. We provide evidence of resistance changes through altering the connection length to the working electrode through theoretical calculations, multimeter measurements, and electrochemical impedance spectroscopy (EIS). We demonstrate that changing the physical length of SPE connections gives rise to more accurate heterogeneous electrode kinetics, which cannot be overcome simply through IR compensation. Significant improvements are observed when utilized as the basis of electrochemical sensing platforms for sodium nitrite, β-nicotinamide adenine dinucleotide (NADH), and lead (II). This work has a significant impact upon the field of SPEs and highlights the need for researchers to characterize and define their specific electrode performance. Without such fundamental characterization as the length and resistance of the SPE used, direct comparisons between two different systems for similar applications are obsolete. We therefore suggest that, when using SPEs in the future, experimentalists report the length of the working electrode connection alongside the measured resistance (multimeter or EIS) to facilitate this standardization across the field.

The COVID-19 pandemic has caused many social and economic problems in Hispanic America, a region with fragile health and economic systems and many inequalities. The pandemic has negatively influenced various aspects of life and led to changes in various habits and behaviours, including consumption. However, the extent to which the pandemic has influenced households, and waste production, in particular, is not well known. In this context, this paper reports on a study aimed at identifying changes in waste production across households under the special conditions created by the pandemic in Hispanic America. The majority of the respondents stated that their level of satisfaction with waste management policies in their countries did not change much during the pandemic. Only a few stated that they were more satisfied than before. Overall, the results suggest that, like previous crises, the COVID-19 outbreak may generate changes regarding household consumption and waste management in Hispanic America. At the same time, these findings stress the need to improve waste management practices. Some measures that may be adopted to allow Hispanic American countries to better cope with increases in waste production in times of pandemics are listed.

We demonstrate that a novel functionalized interface, where molecularly imprinted polymer nanoparticles (nanoMIPs) are attached to screen-printed graphite electrodes (SPEs), can be utilized for the thermal detection of the cardiac biomarker troponin I (cTnI). The ultrasensitive detection of the unique protein cTnI can be utilized for the early diagnosis of myocardial infraction (i.e., heart attacks), resulting in considerably lower patient mortality and morbidity. Our developed platform presents an innovative route to develop accurate, low-cost, and disposable sensors for the diagnosis of cardiovascular diseases, specifically myocardial infraction. A reproducible and advantageous solid-phase approach was utilized to synthesize high-affinity nanoMIPs (average size = 71 nm) for cTnI, which served as synthetic receptors in a thermal sensing platform. To assess the performance and commercial potential of the sensor platform, various approaches were used to immobilize nanoMIPs onto thermocouples or SPEs: dip coating, drop casting, and a covalent approach relying on electrografting with an organic coupling reaction. Characterization of the nanoMIP-functionalized surfaces was performed with electrochemical impedance spectroscopy, atomic force microscopy, and scanning electron microscopy. Measurements from an in-house designed thermal setup revealed that covalent functionalization of nanoMIPs onto SPEs led to the most reproducible sensing capabilities. The proof of application was provided by measuring buffered solutions spiked with cTnI, which demonstrated that through monitoring changes in heat transfer at the solid-liquid interface, we can measure concentrations as low as 10 pg L-1, resulting in the most sensitive test of this type. Furthermore, preliminary data are presented for a prototype platform, which can detect cTnI with shorter measurement times and smaller sample volumes. The excellent sensor performance, versatility of the nanoMIPs, and reproducible and low-cost nature of the SPEs demonstrate that this sensor platform technology has a clear commercial route with high potential to contribute to sustainable healthcare.

In the present work, we report an innovative approach for immunosensors construction. The experimental strategy is based on the anchoring of biological material at screen-printed carbon electrode (SPE) modified with electrodeposited Graphene Quantum Dots (GQD) and polyhydroxybutyric acid (PHB). It was used as functional substract basis for the recognition site receptor-binding domain (RBD) from coronavirus spike protein (SARS-CoV-2), for the detection of Anti-S antibodies (AbS). SEM images and EDS spectra suggest an interaction of the protein with GQD-PHB sites at the electrode surface. Differential pulse voltametric (DPV) measurements were performed before and after incubation, in presence of the target, shown a decrease in voltametric signal of an electrochemical probe ([Fe(CN)

When you bite into a chile pepper or eat food containing chile (chilli), one might feel heat, or other associated feelings, some good such as the release of endorphins, and some bad. The heat, or pungency, and related feelings from eating chile peppers are the result of their chemical composition, i.e. the concentrations of capsaicinoids. The major components are capsaicin and dihydrocapsaicin, which occur in chiles in the ratio of 6 : 4. Other capsaicinoids occur in smaller concentrations and are known as the “minor” capsaicinoids. Wilbur L. Scoville in 1912 created an organoleptic test, now known as the Scoville scale, which asked a panel of tasters to state when an increasingly dilute solution of the chile pepper in alcohol no longer burned the mouth. Following the Scoville scale, a plethora of analytical techniques later followed. In this overview, we explore the endeavours directed to the development of electrochemical-based sensors for the determination of capsaicin and related compounds, starting from their use in hyphenated laboratory set-ups to their modern use as stand-alone electroanalytical sensors. The latter have the advantage of providing a rapid and sensitive methodology that has the potential to be translated in the field; future trends and issues to be overcome are consequently suggested.

2D hexagonal boron nitride (2D-hBN) is a lesser utilised material than other 2D counterparts in electrochemistry due to initial reports of it being non-conductive. As we will demonstrate in this review, this common misconception is being challenged, and researchers are starting to utilise 2D-hBN in the field of electrochemistry, particularly as the basis of electroanalytical sensing platforms. In this critical review, we overview the use of 2D-hBN as an electroanalytical sensing platform summarising recent developments and trends and highlight future developments of this interesting, often overlooked, 2D material.

The use of biological components in the development of new methods of analysis and point-of-care (POC) devices is an ever-expanding theme in analytical chemistry research, due to the immense potential for early diagnosis of diseases and monitoring of biomarkers. In the present work, the evaluation of an electrochemical microfluidic device based on the immobilization of horseradish peroxidase (HRP) enzyme into chemically treated cotton threads is described. This bioreactor was used as a channel for the build of the microfluidic device, which has allowed to use of a non-modified screen-printed electrode (SPE) as an amperometric detector. Cotton threads were treated using citric acid, and the immobilization of HRP has been performed by EDC/NHS crosslinking, connecting amine groups of the enzymes to carboxylic acids in the cellulosic structure. For the analytical evaluation, an amperometric assay for hydrogen peroxide detection was performed after the injection of H

Rapid antigen tests are currently used for population screening of COVID-19. However, they lack sensitivity and utilize antibodies as receptors, which can only function in narrow temperature and pH ranges. Consequently, molecularly imprinted polymer nanoparticles (nanoMIPs) are synthetized with a fast (2 h) and scalable process using merely a tiny SARS-CoV-2 fragment (∼10 amino acids). The nanoMIPs rival the affinity of SARS-CoV-2 antibodies under standard testing conditions and surpass them at elevated temperatures or in acidic media. Therefore, nanoMIP sensors possess clear advantages over antibody-based assays as they can function in various challenging media. A thermal assay is developed with nanoMIPs electrografted onto screen-printed electrodes to accurately quantify SARS-CoV-2 antigens. Heat transfer-based measurements demonstrate superior detection limits compared to commercial rapid antigen tests and most antigen tests from the literature for both the alpha (∼9.9 fg mL

Determination of specific cardiac biomarkers (CBs) during the diagnosis and management of adverse cardiovascular events such as acute myocardial infarction (AMI) has become commonplace in emergency department (ED), cardiology and many other ward settings. Cardiac troponins (cTnT and cTnI) and natriuretic peptides (BNP and NT-pro-BNP) are the preferred biomarkers in clinical practice for the diagnostic workup of AMI, acute coronary syndrome (ACS) and other types of myocardial ischaemia and heart failure (HF), while the roles and possible clinical applications of several other potential biomarkers continue to be evaluated and are the subject of several comprehensive reviews. The requirement for rapid, repeated testing of a small number of CBs in ED and cardiology patients has led to the development of point-of-care (PoC) technology to circumvent the need for remote and lengthy testing procedures in the hospital pathology laboratories. Electroanalytical sensing platforms have the potential to meet these requirements. This review aims firstly to reflect on the potential benefits of rapid CB testing in critically ill patients, a very distinct cohort of patients with deranged baseline levels of CBs. We summarise their source and clinical relevance and are the first to report the required analytical ranges for such technology to be of value in this patient cohort. Secondly, we review the current electrochemical approaches, including its sub-variants such as photoelectrochemical and electrochemiluminescence, for the determination of important CBs highlighting the various strategies used, namely the use of micro- and nanomaterials, to maximise the sensitivities and selectivities of such approaches. Finally, we consider the challenges that must be overcome to allow for the commercialisation of this technology and transition into intensive care medicine. Graphical abstract

© 2020 Wiley-VCH GmbH An electrochemical sensor using glassy carbon electrode modified with carbon black within a poly(allylamine hydrochloride) film is proposed in this work. The novel sensor was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry using the redox probe Fe(CN)63−/4−. The sensor was applied for the simultaneous determination of dopamine (DA), paracetamol (PAR), amlodipine (AML), and rosuvastatin (RSV). The quantification of all four analytes was carried out by linear sweep voltammetry and presented a linear concentration range for all analytes from 1.0 to 90 μmol L−1, with limit of detection of 0.55, 1.3, 5.7, and 3.0 μmol L−1 for DA, PAR, AML, and RSV, respectively. This sensor was successfully applied in the simultaneous determination of these analytes in environmental, pharmaceutical, and biological samples.

Additive manufacturing (AM) provides a unique platform for the rapid design and fabrication of complex structures. Printed structures can be used as is or as templates to be decorated with electrochemical deposited nanomaterials, which may be utilised as electrocatalytic sensing platforms. Novel methods are required to determine the electrochemical deposited morphology present on the electrode surfaces. Additively manufactured graphene macroelectrodes (AM-GMs) were fabricated using a commercially available feedstock and molybdenum (di)oxide (MoO2) was successfully electrochemically deposited onto the electrode surface. The electrochemically deposited MoO2 was analysed using scanning electron microscopy (SEM), optical interferometry, Raman spectroscopy and multifractal analysis (MFA). Although the electrochemical deposition of MoO2 nanowires were clearly visible using SEM, MFA enabled quantification of the MoO2 nanowires, deposited at a variety of time points (20 – 300 s). MFA was utilised to generate quantitative data, derived from ƒ(α) curves, to determine the area of the electrochemical deposited MoO2 nanowires, including coverage, density, dispersion and clustering. The AM-GMs which were subjected to 300 s (maximum time period) of MoO2 electrodeposition demonstrated the greatest percentage area coverage (20.14 %). The use of such mathematical systems offers an inexpensive method to characterise the parameters of electrochemically-deposited materials.

Burn infections caused by Pseudomonas aeruginosa pose a major complication in wound healing. This study aimed to determine the antimicrobial effect of metal ions, graphene (Gr), and graphene oxide (GO), individually and in combination, against the planktonic and biofilm states of two antimicrobially resistant clinical strains of P. aeruginosa each with different antibiotic resistance profiles. Minimum inhibitory, minimum bactericidal, and fractional inhibitory concentrations were performed to determine the efficacy of the metal ions and graphene composites individually and their synergy in combination. Crystal violet biofilm and XTT assays measured the biofilm inhibition and metabolic activity, respectively. Molybdenum, platinum, tin, gold, and palladium ions exhibited the greatest antimicrobial activity (MIC = 7.8–26.0 mg/L), whilst GO and Gr demonstrated moderate-to-no effect against the planktonic bacterial cells, irrespective of their antibiograms. Biofilms were inhibited by zinc, palladium, silver, and graphene. In combination, silver–graphene and molybdenum–graphene inhibited both the planktonic and biofilm forms of the bacteria making them potential candidates for development into topical antimicrobials for burns patients infected with antibiotic-resistant P. aeruginosa.

Additive manufacturing is a promising technology for the rapid and economical fabrication of portable electroanalytical devices. In this paper we seek to determine how our bespoke additive manufacturing feedstocks act as the basis of an electrochemical sensing platform towards the sensing of manganese(ii) via differential pulse cathodic stripping voltammetry (DPCSV), despite the electrode comprising only 25 wt% nanographite and 75 wt% plastic (polylactic acid). The Additive Manufactured electrodes (AM-electrodes) are also critically compared to graphite screen-printed macroelectrodes (SPEs) and both are explored in model and real tap-water samples. Using optimized DPCSV conditions at pH 6.0, the analytical outputs using the AM-electrodes are as follows: limit of detection, 1.6 × 10-9 mol L-1 (0.09 μg L-1); analytical sensitivity, 3.4 μA V μmol-1 L; linear range, 9.1 × 10-9 mol L-1 to 2.7 × 10-6 mol L-1 (R2 = 0.998); and RSD 4.9% (N = 10 for 1 μmol L-1). These results are compared to screen-printed macroelectrodes (SPEs) giving comparable results providing confidence that AM-electrodes can provide the basis for useful electrochemical sensing platforms. The proposed electroanalytical method (both AM-electrodes and SPEs) is shown to be successfully applied for the determination of manganese(ii) in tap water samples and in the analysis of a certified material (drinking water). The proposed method is feasible to be applied for in-loco analyses due to the portability of sensing; in addition, the use of AM-printed electrodes is attractive due to their low cost.

Additive manufacturing (AM/3D printing) is an emerging technology of vast applicability, receiving significant interest in a plethora of industrial domains and scientific research since it allows the rapid translation of designs produced via computer software, into AM/3D printed objects. To date, AM/3D printed devices have been examined for their utilisation as convenient and cost-effective tools towards the detection and quantification of prevalent drugs of abuse. Herein, a novel AM/3D printed wall-jet flow cell was fabricated specifically for employment in high performance liquid chromatography-amperometric detection (HPLCAD) of various analytes (New Psychoactive Substances). Five sensing platforms were investigated, utilising different working electrodes, namely; screen-printed graphite electrodes (SPEs), AM/3D Proto-Pasta, AM/3D Black Magic, graphite sheet and AM/3D printed nanographite (NG) /polylactic acid (PLA)) towards the detection of New Psychoactive Substances. The flow cell was also optimised with respect to the cell geometry demonstrating significant benefits such as simple production and operation and the ability to tailor the platform to a variety of working electrodes. The AM/3D printed sensing platforms were characterised towards the (electro) analytical detection of four N-benzylmethoxy- derivatives: 25F-NBOMe, 25C-NBOMe, 25B-NBOMe and 25I-NBOMe. Furthermore, the (electro) analytical performance of the flow cell was compared with the findings in our previous work comprising of a commercially available impinging jet flow cell. The SPEs and the graphite sheet were found to demonstrate superior electrochemical (analytical) sensitivity and higher reproducibility towards the quantification of the drugs in question, followed by the NG/PLA AM, Proto-Pasta and the Black Magic. The working electrodes that exhibited satisfactory (electro) analytical responses were employed for the analysis of NBOMe derivatives in three simulated blotter papers.

Monolayer hexagonal-boron nitride films (2D-hBN) are typically reported within the literature to be electrochemically inactive due to their considerable band gap (ca. 5.2–5.8 eV). It is demonstrated herein that introducing physical linear defects (PLDs) upon the basal plane surface of 2D-hBN gives rise to electrochemically useful signatures. The reason for this transformation from insulator to semiconductor (inferred from physicochemical and computational characterisation) is likely due to full hydrogenation and oxygen passivation of the boron and/or nitrogen at edge sites. This results in a decrease in the band gap (from ca. 6.11 to 2.36/2.84 eV; theoretical calculated values, for the fully hydrogenated oxygen passivation at the N or B respectively). The 2D-hBN films are shown to be tailored through the introduction of PLDs, with the electrochemical behaviour dependent upon the surface coverage of edge plane-sites/defects, which is correlated with electrochemical performance towards redox probes (hexaammineruthenium(III) chloride and Fe2+/3+) and the hydrogen evolution reaction. This manuscript de-convolutes, for the first time, the fundamental electron transfer properties of 2D-hBN, demonstrating that through implementation of PLDs, one can beneficially tailor the electrochemical properties of this nanomaterial.

In 2020, the new European Drinking Water Directive will be updated to include new drinking-water safety parameters. These will introduce reduced thresholds for the presence of heavy metals, pesticides and other contaminants in domestic drinking water. The aim of these reduced thresholds is to impose a higher level of consumer protection as well as provide guidance for effective monitoring, planning and water management. An example of a newly proposed threshold is the concentration of lead ions (Pb2+) within drinking water, which has been reduced from 10 to 5 parts per billion (ppb). The strict timeframe for water suppliers to meet the new thresholds has created an impetus to develop in situ detection techniques to quantify the levels of chemical contamination on-site in drinking water, allowing them to make prompt interventions. This review explores and discusses the current advances related to electrochemical methods, electrode materials and modifications that have the potential to be the foundations of a new generation of portable electrochemical sensors towards trace-level ion in situ heavy metal sensors.

We report the electroanalytical properties of graphene and graphite paste electrodes comprising varying lateral flake sizes. The fabricated electrodes are first electrochemically validated using a standard redox probe prior to the influence of their heterogeneous electron transfer (HET) kinetics/flake sizes being explored towards sensing applications. Electrochemical analysis is employed using a range of relevant biomolecules and prominent drugs of abuse. It is inferred that smaller lateral flake sizes result in an increased number of edge plane sites ‘available’ upon the electrode surface, leading to greater sensitivity and Limit of Detection (LOD) values. Calibration plots show an improvement in LODs from 0.7 to 0.19 μM and sensitivity from 0.023 to 0.038 A M−1 for the detection of ascorbic acid and LODs from 3.43 to 1.3 μM and sensitivities from 0.009 to 0.025 A M−1 for the detection of β-nicotinamide adenine dinucleotide (NADH) when comparing ‘typical’ (12.2 μm) and ‘small’ (0.5 μm) lateral flake sizes. In the case of uric acid, the reported sensitivity and LOD with typical sizes is 0.046 A M−1 and 1.42 μM, in comparison to 0.168 A M−1 and 0.85 μM with smaller flakes, with dopamine also supporting these findings. In terms of the drugs of abuse considered, methamphetamine exhibits an improved LOD from 0.82 to 0.65 μg mL−1 and sensitivity from 0.15 to 0.25 A μg mL−1 when comparing typical and small flakes respectively. However, cocaine and 3,4-methylenedioxymethamphetamine (MDMA) exhibit variable results, likely due to complex oxidation mechanisms and each paste electrode's specific heterogeneous surface nature. This work demonstrates the sensing capabilities of graphene and graphite paste electrodes comprising varying lateral flake sizes. It is inferred that smaller lateral flake sizes give rise to improved electroanalytical responses and enhanced graphitic based electrochemical sensors; which is important to consider when designing and optimising carbon based electrochemical sensor devices and likely has wider implications in the energy sector when utilising such electrodes.

Redesigning 3D-printed flow cells is reported used for heat transfer based detection of biomolecules from a flow-through system to an addition-type measurement cell. The aim of this study is to assess the performance of this new measurement design and critically analyse the influence of material properties and 3D printing approach on thermal analysis. Particular attention is paid to reduce the time to stabilisation, the sample volume in order to make the technique suitable for clinical applications, and improving the sensitivity of the platform by decreasing the noise and interference of air bubbles. The three different approaches that were studied included a filament polylactic acid cell using only fused filament fabrication (FFF), a resin cell printed using stereolitography (SLA), and finally a design made of copper, which was manufactured by combining metal injection moulding (MIM) with fused filament fabrication (FFF). Computational fluid dynamic (CFD) modelling was undertaken using ANSYS Fluent V18.1 to provide insight into the flow of heat within the measurement cell, facilitating optimisation of the system and theoretical response speed.It was shown that the measurement cells using SLA had the lowest noise (~ 0.6%) and shortest measurement time (15 min), whereas measurement cells produced using other approaches had lower specificity or suffered from voiding issues. Finally, we assessed the potential of these new designs for detection of biomolecules and amoxicillin, a commonly used beta lactam antibiotic, to demonstrate the proof of concept. It can be concluded that the resin addition-type measurement cells produced with SLA are an interesting affordable alternative, which were able to detect amoxicillin with high sensitivity and have great promise for clinical applications due to the disposable nature of the measurement cells in addition to small sample volumes. Graphical abstract