Exposure to carcinogenic elongated mineral particles (EMPs), such as erionite, found in rocks and released into the air by construction, quarrying, or roading activities, poses a significant possible health risk due to their respirable size and potential for airborne dispersion. The detection of EMPs in the air is typically achieved by filter sampling and subsequent examination using a range of microscopic methods, including phase contrast microscopy (PCM) and scanning electron microscope (SEM). Such analyzes require the manual searching for fibers through many image fields and are both labor-intensive and time-consuming. Moreover, these methods do not result in conclusive particle identification, limiting their effectiveness in large-scale monitoring programmes. This paper introduces a novel methodology for the automated detection and quantification of EMPs using an automated SEM with energy dispersive spectroscopy (EDS) to identify fibers on pre-sampled polycarbonate (PC) filters. This method provides a streamlined workflow for fiber identification based on their size, morphology, and elemental composition. Performance evaluation (PE) standards were prepared by spiking filters with a series of known concentrations of one EMP, namely erionite, and fiber concentrations were measured using the automated SEM-EDS approach. Our results demonstrate a linear relationship (R2 = 0.98***) between the erionite mass percentage in a bulk sample and the fiber counts in an aerosolized air volume, with a detection limit of 7.4 f/cc. The approach can be optimized based on the time available for analysis and the choice of detection limit suitable for the specific site and application. Additionally, the automated SEM-EDS method has been applied to real-world air samples collected from Auckland, New Zealand, showing promising results for fiber detection in complex environmental matrices.

Plant pathogen zoospores play a vital role in the transmission of several significant plant diseases, with their early detection being important for effective pathogen management. Current methods for pathogen detection involve labour-intensive specimen collection and laboratory testing, lacking real-time feedback capabilities. Methods that can be deployed in the field and remotely addressed are required. In this study, we have developed an innovative zoospore-sensing device by combining a microfluidic sampling system with a microfluidic cytometer and incorporating a chemotactic response as a means to selectively detect motile spores. Spores of Phytophthora cactorum were guided to swim up a detection channel following a gradient of attractant. They were then detected by a transient change in impedance when they passed between a pair of electrodes. Single-zoospore detection was demonstrated with signal-to-noise ratios of ~17 when a carrying flow was used and ~5.9 when the zoospores were induced to swim into the channel following the gradient of the attractants. This work provides an innovative solution for the selective, sensitive and real-time detection of motile zoospores. It has great potential to be further developed into a portable, remotely addressable, low-cost sensing system, offering an important tool for field pathogen real-time detection applications.

Magnéli phase titanium oxide sheet electrodes and reactive membranes enable efficient electrochemical bromate reduction.

Rapid mixing and precise timing are key for accurate biomedical assay measurement, particularly when the result is determined as the rate of a reaction: for example rapid immunoassay in which the amount of captured target is kinetically determined; determination of the concentration of an enzyme or enzyme substrate; or as the final stage in any procedure that involves a capture reagent when an enzyme reaction is used as the indicator. Rapid mixing and precise timing are however difficult to achieve in point-of-care devices designed for small sample volumes and fast time to result. By using centrifugal microfluidics and transposing the reaction surface from a chamber to a single mm-scale bead we demonstrate an elegant and easily manufacturable solution. Reagents (which may be, for example, an enzyme, enzyme substrate, antibody or antigen) are immobilised on the surface of a single small bead (typically 1–2 mm in diameter) contained in a cylindrical reaction chamber subjected to periodically changing rotational accelerations which promote both mixing and uniform mass-transfer to the bead surface. The gradient of Euler force across the chamber resulting from rotational acceleration of the disc, dΩdisc/dt, drives circulation of fluid in the chamber. Oscillation of Euler force by oscillation of rotational acceleration with period, T, less than that of the hydrodynamic relaxation time of the fluid, folds the fluid streamlines. Movement of the bead in response to the fluid and the changing rotational acceleration provides a dynamically changing chamber shape, further folding and expanding the fluid. Bead rotation and translation driven by fluid flow and disc motion give uniformity of reaction over the surface. Critical parameters for mixing and reaction uniformity are the ratio of chamber radius to bead radius, rchamber/rbead, and the product Trchamber(dΩdisc/dt), of oscillation period and Euler force gradient across the fluid. We illustrate application of the concept using the reaction of horse radish peroxidase (HRP) immobilised on the bead surface with its substrate tetramethylbenzidine (TMB) in solution. Acceleration from rest to break a hydrophobic valve provided precise timing for TMB contact with the bead. Solution uniformity from reaction on the surface of the bead in volumes 20–50 uL was obtained in times of 2.5 s or less. Accurate measurement of the amount of surface-bound HRP by model fitting to the measured kinetics of colour development at 10 s intervals is demonstrated.

Electrochemical dealloying has recently been highlighted as a promising technique for developing active electrodes for water electrosplitting. Intermetallic compounds of a base metal with passive film-forming element are effective oxygen evolution anodes for metal electrowinning. Cobalt-silicon alloys and titanium-nickel intermetallics are demonstrated as examples and related to the proposed paradigm of electrochemical dealloying. These systems illustrate the effects of scale in practical electrochemistry, where ‘scale’ has multiple meanings: the transition to practise; formation of surface deposits; and the evolution of the interface in extended use. In the case of cobalt-silicon alloys, the microstructure of the metal is critical. A highly porous surface layer is developed, within which the active phase is ‘nanostrands’ of cobalt metal in ‘nanoconfinement’ within a slowly-dissolving silicide matrix. Within the confined environment, a saturated solution of cobalt salt causes a salt film over the cobalt metal under which an oxygen-evolving cobalt anodic oxide is stabilised. In the case of TiNi, a nickel-rich surface forms over a thin titanium anodic oxide. Oxygen evolution occurs by field-assisted electron tunnelling to the surface nickel titanium oxide states. Field-driven ion migration both leads to these active states and leads to a slow dissolution of the metal. There is a useful range of composition between 51 and 55 wt% Ni (46 – 50 at %) which balances ductility against dissolution rate: excess titanium leading to a continuous phase of Ti2Ni results in a very brittle material; separation of TiNi3 leads to more rapid dissolution. In practise however, intrusion of oxygen during casting of large plates segregated Ti as the oxide Ti4Ni2O leading to separation of TiNi3 . The more rapid dissolution of this phase, in association with formation of MnO2 from Mn salts present in plant electrolyte, led in association with oxidation of cobalt salts to deposition of an adherent surface scale under which the solution became strongly acidic. The accelerated anode dissolution led to an under-scale of TiO2 which further increased acidification. Impractically rapid destruction of the anode resulted. The work illustrates how mass-transport and microstructure in the evolving interphase between electrode and electrolyte can interact in subtle ways important for practical application.

Biomass resources offer a diverse array of low-cost feedstocks for the manufacture electrocatalysts for the energy sector. In this study, haemoglobin (Hb), lignin, tannic acid and urea were used to develop FeSN/C electrocatalysts comprising iron highly dispersed on S,N-codoped carbon for the oxygen reduction reaction (ORR). By pyrolyzing precursor mixtures containing Hb, lignin, tannic acid and urea in appropriate mass ratios, S,N-codoped carbons with highly dispersed Fe sites were obtained with ORR performance superior to Pt/C. The developed FeSN/C electrocatalyst exhibited an ORR onset potential of 0.98 V vs. RHE in 0.1 M KOH, a half-wave potential (E1/2) of 0.87 V and a low Tafel slope of 54 mV/dec. Notably, the electrocatalyst selectively catalysed the 4-electron ORR pathway and exhibited a high methanol tolerance. This work encourages the design of biomass-derived electrocatalysts for oxygen reduction reaction, in particular showing that haemoglobin in bovine blood is a suitable for use an iron source when making Fe-N-C electrocatalysts.

We evaluate the potential of using a previously developed remote calibration framework we name MOMA (MOment MAtching) to improve the data quality in particulate matter (PM) sensors deployed in hierarchical networks. MOMA assumes that a network of reference instruments can be used as “proxies” to calibrate the sensors given that the probability distribution over time of the data at the proxy site is similar to that at a sensor site. We use the reference network to test the suitability of proxies selected based on distance versus proxies selected based on land use similarity. The performance of MOMA for PM sensors is tested with sensors co-located with reference instruments across three Southern Californian regions, representing a range of land uses, topography and meteorology, and calibrated against a distant proxy reference. We compare two calibration approaches: one where calibration parameters get calculated and applied at monthly intervals and one which uses a drift detection framework for calibration. We demonstrate that MOMA improves the accuracy of the data when compared against the co-located reference data. The improvement was more visible for PM10 and when using the drift detection approach. We also highlight that sensor drift was associated with variations in particle composition rather than instrumental factors, explaining the better performance of the drift detection approach if wind conditions and associated PM sources varied within a month.

In this study, we utilize nanosecond and femtosecond direct laser writing for the generation of hydrophobic and hydrophilic microfluidic valves on a centrifugal microfluidic disk made of polycarbonate, without the need for wet-chemistry. Application of a femtosecond (fs) laser at 800 nm resulted in an increased contact angle, from ∼80° to ∼160°, thereby inducing the formation of a hydrophobic surface. In contrast, employing a nanosecond (ns) laser at 248 nm led to the formation of superhydrophilic surfaces. Morphological studies identified the enhancement in the surface roughness for the hydrophobic surfaces and the creation of smooth patterns for the hydrophilic surfaces. Chemical modifications in the laser-ablated samples were confirmed via Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. These spectroscopic examinations revealed an increase of hydrophilic chemical groups on both surfaces, with a more pronounced increase on the nanosecond laser-modified surface. Furthermore, these surfaces were used as a case study for centrifugal microfluidic valves. These modified surfaces demonstrated peculiar pressure responses. Specifically, the hydrophobic valves necessitated a 29% increase in pressure for droplet passage through a microchannel. On the other hand, the superhydrophilic valves exhibited enhanced wettability, decreasing the pressure requirement for fluid flow through the modified area by 39%. However, similarly to the hydrophobic valves, the fluid exiting the hydrophilic valve area required an increased pressure. Overall, our study shows the potential for tailoring valve functionality in microfluidic systems through precise surface modifications using laser technology.

Nano-sized placental extracellular vesicles (nano-pEVs) are membrane-bound vesicles released into the maternal circulation during pregnancy by the syncytiotrophoblast, which covers the surface of the placenta. The nano-pEV cargo consists of proteins, lipids, and nucleic acids, which reflect the dynamic placental function during gestation. The ability to biopsy circulating nano-pEVs would aid investigations in placental functions, allowing substantial progress in obstetric care. We developed a simple and clean electrochemical methodology for the specific capture and fast release of nano-pEVs using an electro-chemically switchable conducting terpolymer-functionalized car-bon cloth. The conducting terpolymer was first reduced (at -0.8 V vs Ag/AgCl, 30 s in PBS) to form active thiols, which could then interact with a thiolated CD63 aptamer via oxidation (+1.0 V vs Ag/AgCl, 60 s) in PBS. Conjugation of the aptamer to the conducting terpolymer-coated carbon cloth was confirmed using SEM-EDS, FTIR, and Raman spectroscopy. As a proof of principle, thiolated fluorescently labeled CD63 aptamers were captured and released electrochemically using this technique. Thereafter, the CD63 aptamer-modified carbon cloth showed the specific capture of nano-pEVs and their subsequent release (-0.8 V vs Ag/AgCl, 120 s) following cleavage of the disulfide bond between the aptamer and the reduced terpolymer. This aptamer-modified conducting terpolymer-coated carbon cloth demonstrated good capture and release efficiencies of (2.09 +/- 0.26) x 108 and (1.35 +/- 0.14) x 108 particles, respectively, per 70 mm2 of the projected area of the terpolymer-coated carbon cloth. Confocal microscopy images clearly differentiated the carbon cloth fibers with captured nano-pEVs from those after the release. To the best of our knowledge, this work has developed for the first time an efficient, rapid, and straightforward methodology for the capture and release of nano-pEVs. This effective methodology could help to quickly determine fetal abnormalities, to diagnose obstetric disease and pathogenesis throughout pregnancy.

The development of microstructures which combine high total surface area and high porosity is crucial for technologies such as electrocatalysis, electrochromics, and sensors. High deposition rate, composition control of deposition, and low processing temperature to retain active compositions are also desirable. To this end, this study describes combining colloidal sol chemistry with a jet to print hybrid inorganic/organic tungsten trioxide/oxalic acid (WO3-x/OA) microspheres. Injection of an aerosol of oxalic acid stabilized colloidal tungstic acid into an atmospheric pressure plasma jet results in the deposition of spherical structures in which the colloid is trapped within a plasma-polymerized organic shell. Subsequent lowtemperature sintering produces hierarchical spherical shell-like structures comprising tungsten oxide nanosheets. Alteration of the gas flow rate changes the composition of the deposited material. The method has promise for the general preparation from colloidal precursors of porous materials of controlled morphology and composition with hierarchical microstructures, such as are required for applications in electrochemical devices and sensors which need a high ratio of surface area to volume and connectivity throughout the structure, yet also need a microstructure which is open for rapid exchange of reactants.

Electrochemical sensors are used to measure electroactive gases in ambient air monitoring applications. These sensors typically contain sulfuric acid electrolyte, and porous carbon working, reference, and counter electrodes. Current fluctuations caused by fluctuations in the meniscus contact shape or area at the 3 phase gas-electrolyte -electrode interface as a result of ambient pressure fluctuations have been suggested as a potentially significant source of error in sensor measurements. We confirm in the present work that the pressure oscillations associated with ambient sound can indeed lead to significant signals. We show, for a variety of commercial sensors for ambient nitrogen dioxide (NO2), that acoustic noise equivalent to that from a nearby motorcycle or heavy goods vehicle can cause transient current fluctuations at 2 Hz sampling rate equivalent in the sensor output to as much as that due to 100 parts per billion by volume (ppb) of NO2, and with a root mean square (RMS) variation averaged over 10 s of approximately 40 ppb equivalent. These observations indicate that electrochemical gas sensors can behave as "microphones" in response to loud noise. The impact of acoustic noise should be considered when using electrochemical sensors to measure ambient air quality in areas of significant noise pollution, particularly if the aim is to resolve local transient concentration variations.

Burkle et al. [1] present an elegant study using a flow cell designed to allow synchrotron X-ray diffraction study of the growth of siderite layers on carbon steel at elevated temperature in the presence of CO2 under rigorously de-oxygenated conditions. However, they state that in earlier work, “the growth of the corrosion product was accelerated by applying excessive currents/voltages (unlike in this research) to the sample under study which were not realistic of the actual corrosion kinetics encountered in the field and consequently prevented the true processes of film formation from being established”. In the present comment, the hydrodynamics of the cell of Burkle et al. are analysed using an approximate model and it is shown that the results of the different studies are in fact completely consistent, further supporting the deductions and model of the earlier work for the effects of hydrodynamics on anodic crystal growth. Further it is shown that fitting of their results to the Avrami model used in the earlier studies illustrates the transition from anodic to cathodic reaction rate control with increase of solution pH. Comparison of the different studies indeed illustrates “the true processes of film formation”. The hydrodynamic model in conjunction with that developed in previous studies implies a significant variation over the surface of the anodic electrocrystallisation rate in the cell used by Burkle et al..

At low copy number, sequence detection by polymerase chain reaction (PCR) requires up to 30 cycles (amplification by a factor of 109) to produce a reliably detectable concentration of fluorescently-labelled amplicons. The cycle number and hence detection time is determined by the analytical sensitivity of the detector. Hybridisation of complementary DNA strands to oligonucleotide-modified conducting polymer electrodes yields an increase in the charge transfer resistance for the ferri-ferrocyanide redox couple. Sensors using this technology for e-PCR offer a label-free method with detector sensitivity in the pM range, potentially decreasing the required cycle number from 30 to 10 and offering a much simplified instrument construction. We demonstrate sensors using screen-printed carbon electrodes modified with a conducting polymer formed from a monomer pre-functionalised with complementary oligonucleotide. Off-chip pre-functionalisation of the conducting polymer precursor is a key step towards practical manufacture and the method is potentially a general one for sensors which require a capture probe-functionalised surface. We demonstrate reliable sensitivity of the interfacial resistance change at the pM scale for short (20-mer) sequences and at the aM scale for bacterial lysate, with dynamic range extending to μM scale and response time-scale 5 min. Donnan exclusion of the redox couple from the surface, as previously proposed, seems unlikely as a mechanism for such ultra-high sensitivity. We demonstrate that the most important element in the response at the lowest concentrations is due to variation of an electrical resistance within the polymer film. We develop a mechanism based on repulsion from the solution interface of dopant anions and attraction towards and trapping at the interface of radical cations (polarons) by the charge associated with surface-bound DNA. With results for >160 single-use sensors, we formulate a response model based on percolation within a random resistor network and highlight challenges for large-scale manufacture of such sensors. We propose a PCR device concept for rapid use at point-of-sampling.

The increase of COVID-19 breakthrough infection risk with time since vaccination has a clear relationship to the decrease of antibody concentration with time. The empirically-observed dependence on blood IgG anti-receptor binding domain antibody concentration of SARS-CoV-2 vaccine efficacy against infection has a rational explanation in the statistics of binding of antibody to spike proteins on the virus surface, leading to blocking of binding to the receptor: namely that the probability of infection is the probability that a critical number of the spike proteins protruding from the virus are unblocked. The model is consistent with the observed antibody concentrations required to induce immunity and with the observed dependence of vaccine efficacy on antibody concentration and thus is a useful tool in the development of models to relate, for an individual person, risk of infection given measured antibody concentration. It can be used to relate population breakthrough infection risk to the distribution across the population of antibody concentration, and its variation with time.

Biofouling on surfaces, caused by the assimilation of proteins, peptides, lipids and microorganisms, leads to contamination, deterioration and failure of biomedical devices and causes implants rejection. To address these issues, various antifouling strategies have been extensively studied, including polyethylene glycol-based polymer brushes. Conducting polymers-based biointerfaces have emerged as advanced surfaces for interfacing biological tissues and organs with electronics. Antifouling of such biointerfaces is a challenge. In this study, we fabricated electrospun fibre mats from sulphonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (sSEBS), infused with conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) (sSEBS-PEDOT), to produce a conductive (2.06 ± 0.1 S/cm), highly porous, fibre mat that can be used as a biointerface in bioelectronic applications. To afford antifouling, here the poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) brushes were grafted onto the sSEBS-PEDOT conducting fibre mats via surface-initiated atom transfer radical polymerization technique (SI-ATRP). For that, a copolymer of EDOT and an EDOT derivative with SI-ATRP initiating sites, 3,4-ethylenedioxythiophene) methyl 2-bromopropanoate (EDOTBr), was firstly electropolymerized on the sSEBS-PEDOT fibre mat to provide sSEBS-PEDOT/P(EDOT-co-EDOTBr). The POEGMA brushes were grafted from the sSEBS-PEDOT/P(EDOT-co-EDOTBr) and the polymerization kinetics confirmed the successful growth of the brushes. Fibre mats with 10-mers and 30-mers POEGMA brushes were studied for antifouling using a BCA protein assay. The mats with 30-mers grafted brushes exhibited excellent antifouling efficiency, ~82% of proteins repelled, compared to the pristine sSEBS-PEDOT fibre mat. The grafted fibre mats exhibited cell viability >80%, comparable to the standard cell culture plate controls. Such conducting, porous biointerfaces with POEGMA grafted brushes are suitable for applications in various biomedical devices, including biosensors, liquid biopsy, wound healing substrates and drug delivery systems.

Martin Fleischmann was an electrochemist whose work revolutionized the subject. He was a consummate mathematician and inspired inventor of new experimental methods. His work led to the development of several important techniques in the field: ground-breaking studies of electrocrystallization stemming from the development of high-speed potentiostats; the discovery of the surface-enhanced Raman effect; the development of microelectrodes; the study of stochastic effects as a means to derive basic information about electrochemical reactions; and the systematic development of concepts of electrochemical engineering. But for many, his name is indelibly associated with the ‘cold fusion’ episode that took place at the end of his career in the late 1980s. Regarded by some as a blemish on Fleischmann's highly distinguished life in science, cold fusion continues even today to excite debate and controversy. Nevertheless, he is remembered with esteem and affection by his many colleagues and leaves a powerful legacy in his discipline.

Materials platforms that enable controlled isolation and subsequent release of chemical/biological entities are in great demand for a diverse range of practical applications. Current technologies lack good control and efficiency of the release, which is needed to preserve the captured targets of interest. Here, this need is addressed by providing a versatile, controllable, electrochemical capture/release interface. The interface consists of a highly porous electrospun membrane, electrodeposited with a thiol‐functionalized 3,4‐ethylenedioxythiophene (EDOT) conductive terpolymer, in which the thiol moiety undergoes oxidation/reduction cycles at moderate potentials (+1.0 and −0.8 V, respectively) to enable capture/release. The fast oxidative capture (1 min) and reductive release (2 min) of a model thiol molecule in a highly controllable manner, followed by successful capture/release of an antibody, are demonstrated. Then, femtosecond laser‐patterning is used to fabricate an array of ≈30 µm pores on the electrospun membrane, subsequently coated with the conducting terpolymer, enabling the highly efficient (>90%), fast (20 min) and selective capture of MCF7 cancer cells with 33% release efficiency when polarized at −0.8 V. The released cells show a high level of viability, indicating the capture and release process does not affect cell survival.

Electrochemical sensors are used to measure electroactive gases in ambient air monitoring applications. These sensors typically contain sulfuric acid electrolyte, and porous carbon working, reference, and counter electrodes. A response to ambient sound has been suggested as one source of error in sensor measurements, which we confirm in the present work. We show, for a variety of commercial sensors for ambient nitrogen dioxide (NO2), that acoustic noise equivalent to that from a nearby motorcycle or heavy goods vehicle can cause current fluctuations equivalent to as much as 100 parts per billion by volume (ppb) of NO2, with a sustained loud noise causing a root mean square (RMS) variation at low sampling rate of approximately 40 ppb equivalent. These observations indicate that electrochemical gas sensors can behave as “microphones” in response to loud noise. We hypothesize that these baseline current fluctuations are induced by mechanical perturbations of the meniscus at the three-phase interface of the working electrode. Mechanical perturbations of the meniscus would result from changes in air pressure at the interface, which could be caused by acoustic noise. The impact of acoustic noise should be considered when using electrochemical sensors to measure ambient air quality in areas of significant noise pollution, particularly if the aim is to resolve local transient concentration variations.