Effect of ZnO doping on morphology and electrochemical properties of sub-micron RuO2 sensing electrode of DO sensor

Thick-film 20 mol% ZnO-doped RuO₂ sensing electrodes (SEs) were fabricated by screen-printing technique on the platinised alumina substrate of the planar electrochemical dissolved oxygen (DO) sensor. The effect of ZnO doping on morphology, electrochemical properties and sensing characteristics of the sensor was investigated. It was found that ZnO doping has not only improved the SE structure, but has also enhanced selectivity of the DO sensor. Selectivity testing exhibited that the presence of Cl⁻, Li⁺, SO₄²⁻, NO³⁻, Ca²⁺, PO₄³⁻, Mg²⁺, Na⁺ and K⁺ with a concentration range of 10⁻⁷ to 10⁻¹ mol/L in the solution had practically no effect on the sensor's emf. The reason in enhancement of the sensor characteristics could be related to the establishment of the better structured SE as more advanced crystallization is achieved for the doped RuO₂-SE.     

Scleral Lens Sensor for Ocular Electrolyte Analysis

The quantitative analysis of tear analytes in point-of-care settings can enable early diagnosis of ocular diseases. Here, a fluorescent scleral lens sensor is developed to quantitatively measure physiological levels of pH, Na⁺, K⁺, Ca²⁺, Mg²⁺, and Zn²⁺ ions. Benzenedicarboxylic acid, a pH probe, displays a sensitivity of 0.12 pH units within pH 7.0–8.0. Crown ether derivatives exhibit selectivity to Na⁺ and K⁺ ions within detection ranges of 0–100 and 0–50 mmol L⁻¹, and selectivities of 15.6 and 8.1 mmol L⁻¹, respectively. A 1,2 bis(o-aminophenoxy)ethane-N,N,-N',N'-tetraacetic-acid-based probe allows Ca²⁺ ion sensing with 0.02–0.05 mmol L⁻¹ sensitivity within 0.50–1.25 mmol L⁻¹ detection range. 5-Oxazolecarboxylic acid senses Mg²⁺ ions, exhibiting a sensitivity of 0.10–0.44 mmol L⁻¹ within the range of 0.5–0.8 mmol L⁻¹. The N-(2-methoxyphenyl)iminodiacetate Zn²⁺ ion sensor has a sensitivity of 1 µmol L⁻¹ within the range of 10–20 µmol L⁻¹. The fluorescent sensors are subsequently multiplexed in the concavities of an engraved scleral lens. A handheld ophthalmic readout device comprising light-emitting diodes (LEDs) and bandpass filters is fabricated to excite as well as read the scleral sensor. A smartphone camera application and an user interface are developed to deliver quantitative measurements with data deconvolution. The ophthalmic system enables the assessment of dry eye severity stages and the differentiation of its subtypes.     

Quartz Tuning Fork: Thermometer, Pressure- and Viscometer for Helium Liquids

Commercial quartz oscillators of the tuning-fork type with a resonant frequency of ∼ 32 kHz have been investigated in helium liquids. The oscillators are found to have at best Q values in the range 10⁵–10⁶, when measured in vacuum below 1.5 K. However, the variability is large and for very low temperature operation the sensor has to be preselected. We explore their properties in the regime of linear viscous hydrodynamic response in normal and superfluid ³He and ⁴He, by comparing measurements to the hydrodynamic model of the sensor. Dedicated to former JLTP editor Frank Pobell.     

Neutral N,N′-bis(2-pyridinecarboxamide)-1,2-ethane as sensing material for determination of lutetium(III) ions in biological and environmental samples

The biological properties of the lutetium as well as other lanthanide ions, primarily based on their similarity to calcium, have been the bases for research into potential therapeutic applications of lanthanide series since the early part of the twentieth century. In this research, a Lu(III) potentiometric membrane sensor based on N,N′-bis(2-pyridinecarboxamide)-1,2-ethane (PCAE) is described. The sensor exhibits a Nernstian response over a concentration range of 1.0 × 10^? 6 mol L^? 1–1.0 × 10^? 1 mol L^? 1, with a detection limit of 6.0 × 10^? 7 mol L^? 1. The best performance was achieved with a membrane composition, consisting of 30% PVC, 63% o-nitrophenyl octyl ether (NPOE), 5% PCAE and 2% sodium tetraphenylborate (NaTPB). It was found that at the pH range of 4.0–9.0, the potential response of the sensor was not affected by the pH. Furthermore, the electrode presents satisfactory reproducibility, very fast response time (5 s) and relatively good discriminating ability for Lu(III) ions with respect to many common cations and other lanthanide ions. The sensor has been applied to the determination of Lu(III) in human serum and in some soil samples where domestic devices were stored.     

Cobalt Nanoparticles and Atomic Sites in Nitrogen‐Doped Carbon Frameworks for Highly Sensitive Sensing of Hydrogen Peroxide

In situ monitoring of hydrogen peroxide (H₂O₂) during its production process is needed. Here, an electrochemical H₂O₂ sensor with a wide linear current response range (concentration: 5 × 10^?8 to 5 × 10^?2 m ), a low detection limit (32.4 × 10^?9 m ), and a high sensitivity (568.47 µA mm ^?1 cm^?2) is developed. The electrocatalyst of the sensor consists of cobalt nanoparticles and atomic Co‐N_x moieties anchored on nitrogen doped carbon nanotube arrays (Co‐N/CNT), which is obtained through the pyrolysis of the sandwich‐like urea@ZIF‐67 complex. More cobalt nanoparticles and atomic Co‐N_x as active sites are exposed during pyrolysis, contributing to higher electrocatalytic activity. Moreover, a portable screen‐printed electrode sensor is constructed and demonstrated for rapidly detecting (cost ≈40 s) H₂O₂ produced in microbial fuel cells with only 50 µL solution. Both the synthesis strategy and sensor design can be applied to other energy and environmental fields.     

Tailor‐Made Micro‐Object Optical Sensor Based on Mesoporous Pellets for Visual Monitoring and Removal of Toxic Metal Ions from Aqueous Media

Methods for the continuous monitoring and removal of ultra‐trace levels of toxic inorganic species (e.g., mercury, copper, and cadmium ions) from aqueous media such as drinking water and biological fluids are essential. In this paper, the design and engineering of a simple, pH‐dependent, micro‐object optical sensor is described based on mesoporous aluminosilica pellets with an adsorbed dressing receptor (a porphyrinic chelating ligand). This tailor‐made optical sensor permits ultra‐fast (≤ 60 s), specific, pH‐dependent visualization and removal of Cu²⁺, Cd²⁺, and Hg²⁺ at sub‐picomolar concentrations (～10^?11 mol dm^?3) from aqueous media, including drinking water and a suspension of red blood cells. The acidic active acid sites of the pellets consist of heteroatoms arranged around uniformly shaped pores in 3D nanoscale gyroidal mesostructures densely coated with the chelating ligand. The sensor can be used in batch mode, as well as in a flow‐through system in which sampling, target ion recognition and removal, and analysis are integrated in a highly automated and efficient manner. Because the pellets exhibit long‐term stability, reproducibility, and versatility over a number of analysis/regeneration cycles, they can be expected to be useful for the fabrication of inexpensive sensor devices for naked‐eye detection of toxic pollutants.     

Praseodymium analysis in aqueous solution by Pr3+–PVC membrane sensor based on N,N′-bis(4-hydroxysalicylidene)-1-3-phenylenediamine

A new Pr³⁺ poly vinyl chloride PVC membrane sensor based on a membrane containing 3% N,N′-bis(4-hydroxysalicylidene)-1-3-phenylenediamine (HSPDA) as an ionophore, 2% sodium tetraphenyl borate (NaTPB) as an anionic additive, 65% benzyl acetate (BA) as solvent mediator and 30% poly(vinyl chloride) was prepared. This sensor responds to praseodymium ion in a wide linear dynamic range of 1.0 × 10^?6 to 1.0 × 10^?2 mol L^?1 with Nernstian slope of 19.8 ± 0.4 mV per decade and a detection limit of 5.7 × 10^?7 mol L^? 1 in pH range of 3.1 to 9.8. It has a fast response time of ~5 s in the whole concentration range, and can be used for at least 2 months without any considerable divergences in the potentials. The proposed sensor displays an excellent selectivity for Pr³⁺ ions with respect to a large number of alkali, alkaline earth, transition and heavy metal ions. The developed sensor was successfully applied as an indicator electrode in Pr³⁺ ion potentiometric titration with EDTA, and in direct determination of fluoride ion in two mouth wash samples.     

Optical sensor based on 1,3-di(2-methoxyphenyl)triazene for monitoring trace amounts of mercury(II) in water samples

A new optical sensor for highly sensitive and selective determination of mercury(II) ion in aqueous solutions is developed. The mercury sensing membrane was prepared by incorporating 1,3-di(2-methoxyphenyl)triazene (MPT) as chromoionophore in the plasticized PVC membrane containing tris(2-ethylhexyl)phosphate (TEHP) as plasticizer. The proposed sensor displays a wide linear range of 9.0 × 10^?10–2.5 × 10^?7 M with a low detection limit of 2.0 × 10^?10 M in aqueous solutions at pH 4.0. This sensor has a relatively fast response time of less than 5 min. In addition to high stability and reproducibility, it shows a unique selectivity towards Hg²⁺ ion with respect to common coexisting cations. The sensor can readily be regenerated by exposure to a solution of sodium iodide (0.01 M). The proposed optode was applied to the determination of Hg²⁺ in water samples.     

Magnetic Susceptibility Study of Sub‐Pico‐emu Sample Using a Micromagnetometer: An Investigation through Bistable Spin‐Crossover Materials

A promising and original method to study the spin‐transition in bistable spin‐crossover (SCO) materials using a magnetoresistive multiring sensor and its self‐generated magnetic field is reported. Qualitative and quantitative studies are carried out combining theoretical and experimental approaches. The results show that only a small part of matter dropped on the sensor surface is probed by the device. At a low bias‐current range, the number of detected nanoparticles depends on the amplitude of the current. However, in agreement with the theoretical model, the stray voltage from the particles is proportional to the current squared. By changing both the bias current and the concentration of particle droplet, the thermal hysteresis of an ultrasmall volume, 1 × 10^?4 mm³, of SCO particles is measured. The local probe of the experimental setup allows a highest resolution of 4 × 10^?14 emu to be reached, which is never achieved by experimental methods at room temperature.     

Non-ambiguous Evanescent-wave Fibre Refractive Index and Temperature Sensor

The dependence of the leakage of the LP₀₁ mode of a polished single-mode fibre section on the refractive index of an external medium provides non-ambiguous intensity modulation of the guided wave and a single-point in situ calibration of a sensor based on this refractive index, or temperature, transducing mechanism. Refractive index and temperature resolution of 10^m4 and 0·1°, has been obtained over an adjustable range of 0·02 and 80°, respectively.     

A Digital−Analog Bimodal Memristor Based on CsPbBr3 for Tactile Sensory Neuromorphic Computing

Memristor with digital and analog bipolar bimodal resistive switching offers a promising opportunity for the information-processing component. However, it still remains a huge challenge that the memristor enables bimodal digital and analog types and fabrication of artificial sensory neural network system. Here, a proposed CsPbBr₃-based memristor demonstrates a high ON/OFF ratio (>10³), long retention (>10⁴ s), stable endurance (100 cycles), and multilevel resistance memory, which acts as an artificial synapse to realize fundamental biological synaptic functions and neuromorphic computing based on controllable resistance modulation. Moreover, a 5 × 5 spinosum-structured piezoresistive sensor array (sensitivity of 22.4 kPa⁻¹, durability of 1.5 × 10⁴ cycles, and fast response time of 2.43 ms) is constructed as a tactile sensory receptor to transform mechanical stimuli into electrical signals, which can be further processed by the CsPbBr₃-based memristor with synaptic plasticity. More importantly, this artificial sensory neural network system combined the artificial synapse with 5 × 5 tactile sensing array based on piezoresistive sensors can recognize the handwritten patterns of different letters with high accuracy of 94.44% under assistance of supervised learning. Consequently, the digital−analog bimodal memristor would demonstrate potential application in human–machine interaction, prosthetics, and artificial intelligence.     

Typical flow between enclosed corotating disks and its dependence on Reynolds number

Abstract

The flow in an enclosed co‐rotating disk pair is investigated by Laser Doppler Velocimetry (LDV) measurements and flow visualizations. First, the typical flow structure at Re = 5.25 × 10⁵ and S = 0.09 is clarified. The flow fields in the r – θ and the r – z planes are both investigated and then divided into several flow regions based on the distinct flow types observed. The flow regions found in the two different planes are also compared and integrated. Second, with S fixed, the dependence of the flow field structure upon the Reynolds number is discussed. Three regimes of the r – θ plane flow with different Reynolds numbers are identified based on the measured mean velocity and spectral intensity. When Re < 1.6 × 10⁵, no solid body region is found and the flow is in a laminar regime. In the range 1.6 × 10⁵ ≤ Re ≤ 2.0 × 10⁶, the solid body region and the outer region vortices coexist, and an empirical equation is developed to estimate the number of vortices. When Re > 2.0 × 10⁶, the flow becomes turbulent. As Re increases from 9.3 × 104 to 5.25 × 10⁵, the spectral intensity initially increases and then decreases before increasing again to an even higher level, resulting in an increasing sawtooth pattern.     

Heterovalent substitution of group IV and V diamagnetic ions in the ferromagnetic spinel CuCr2S4

Heterovalent substitution of As⁵⁺, Sb⁵⁺, V⁵⁺, and Sn⁴⁺ diamagnetic ions in CuCr₂S₄ was studied. The results show that, similar to other 3d¹⁰ diamagnetic ions, the As⁵⁺ ions occupy only tetrahedral interstices in the close packing of sulfur ions, while the Sb⁵⁺ and Sn⁴⁺ 4d¹⁰ ions, as well as the Sc³⁺, Ti⁴⁺, and V⁵⁺ 3d⁰ ions occupy only octahedral sites. A new compound of composition Cu₃AsCr₈S₁₆ was synthesized and characterized. It crystallizes in an orthorhombic (sp. gr.Pmm2) spinel-derived structure containing ordered Cu and As ions in tetrahedral sites(a = 13.942 ± 0.004 Å,b = 6.878 ± 0.002 Å,c = 19.692 ± 0.006 Å, Z = 4, V = 1888.43 ± 0.92 Å). The CuCr_1.5Sb_0.5S₄ spinel phase is found to crystallize in sp. gr.Fd3m (a = 10.009 ± 0.002 Å,u = 0.3815 ± 0.0004 Å) with partial ordering on octahedral sites.     

The mechanical and structural properties of Y1Ba2Cu3O7−x superconductors

Mechanical losses spectroscopy of two superconducting Y₁Ba₂Cu₃O_7–x samples (T _c=93 K) measured at 5, 10, 20 and 30 MHz revealed four peaks. As the frequency of measurement was increased, the peaks shifted to higher temperatures. The relaxation process was found to have an activation enthalpy of 0.188, 0.092, 0.209 and 0.314 eV with an attempt frequency,f _o, equal to 2.46 × 10¹⁵, 5.95 × 10¹⁰, 1.64 × 10¹⁴, and 7.82 × 10¹³ Hz for P₁, P₂, P₃ and P₄ peaks, respectively. The mechanism responsible for these relaxation peaks is discussed. The infrared spectra of some of these compounds provide evidence for oxygen rearrangement on going from tetragonal to orthorhombic phase. X-ray diffraction analysis shows that these compounds correspond to a single phase which is an orthorhombic perovskite structure.     

Effect of rare-earth doping on the electrical properties of InSe single crystals

The effect of rare-earth doping (R = Gd, Dy, Ho) to different levels (0, 10^?5, 10^?4, 10^?3, 10^?2, and 10^?1 at %) on threshold switching and low-frequency current oscillations in single crystals of indium selenide, a layered III–VI semiconductor, has been studied in broad ranges of temperatures (77–400 K), wavelengths (0.30–3.50 μm), and illuminances (up to ～10² lx). The results are interpreted in terms of the anisotropic chemical bonding in n-InSe and its response to rare-earth doping.     

Thermal Expansion of Simulated Fuels with Dissolved Fission Products in a UO2 Matrix

As a part of the DUPIC (direct use of spent PWR fuel in CANDU reactors) fuel development program, the thermal expansion of simulated spent fuel pellets with dissolved fission products has been studied by using a thermo-mechanical analyzer (TMA) in the temperature range from 298 K to 1773 K to investigate the effects of fission products forming solid solutions in a UO₂ matrix on the thermal expansions. Simulated fuels with an equivalent burn-up of (30 to 120) GWd/tU were used in this study. The linear thermal expansions of the simulated fuel pellets were higher than that of UO₂, and the difference between these fuel pellets and UO₂ increased monotonically with temperature. For the temperature range from 298 K to 1773 K, the values of the average linear thermal expansion coefficients for UO₂ and simulated fuels with an equivalent burn-up of (30, 60, and 120) GWd/tU are 1.19 × 10⁻⁵ K⁻¹, 1.22 × 10⁻⁵ K⁻¹, 1.26 × 10⁻⁵ K⁻¹, and 1.32 × 10⁻⁵ K⁻¹, respectively.     

Dysprosium selective potentiometric membrane sensor

A novel Dy(III) ion-selective PVC membrane sensor was made using a new synthesized organic compound, 3,4-diamino-N′-((pyridin-2-yl)methylene)benzohydrazide (L) as an excellent sensing element. The electrode showed a Nernstian slope of 19.8 ± 0.6 mV per decade in a wide concentration range of 1.0 × 10^? 6–1.0 × 10^? 2 mol L^? 1, a detection limit of 5.5 × 10^? 7 mol L^? 1, a short conditioning time, a fast response time (< 10 s), and high selectivity towards Dy(III) ion in contrast to other cations. The proposed sensor was successfully used as an indicator electrode in the potentiometric titration of Dy(III) ions with EDTA. The membrane sensor was also applied to the F^– ion indirect determination of some mouth washing solutions and to the Dy^3 + determination in binary mixtures.     

Concentration and spectrophotometric determination of zirconium(IV) during the analysis of rock using a chelating sorbent

The technique of spectrophotometric determination of Zr(IV) in rock based on preliminary individual extraction (concentration) of this element by a polymer chelating sorbent, namely, polystyrene-2-oxi-(azo-1)-2′-oxi-3′,5′-dinitrobenzene, is described. The determination is not hindered by 6 ×10⁴-fold mass amounts of Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, and Sr²⁺; 2 × 10⁴-fold mass amounts of Al³⁺, Cu²⁺, Pb²⁺, Co²⁺, Ni²⁺, Zn²⁺, and Cd²⁺; 5 × 10³-fold mass amounts of Sn²⁺, Fe²⁺, Be²⁺, and Ce³⁺; and 2 × 10³-fold mass amounts of Fe³⁺, Sc³⁺, and Y³⁺. Quantitative extraction of the element takes place in static conditions within the acidity range of 1 M HCl—2.5 pH. The correctness of the technique was tested by the analysis of standard rock specimens. The relative standard deviation is 0.01–0.04 during determination of Zr(IV) at the concentration level of n × 10^?2-n × 10^?4%.     

Effect of pressure on the coking yields of coal tar pitches

Pyrolysis of five coal tar pitches with wide ranging characteristics, made from the same coal tar precursor, has been studied under nitrogen pressures of 10⁵, 50×10⁵, 90×10⁵ and 160×10⁵ Pa, at a temperature of 550 °C. The residues were further heat-treated to 900 °C to obtain the ultimate normal (10⁵ Pa) and pressure coking yields of these pitches. The literature states that for pitches with relatively lower softening points the carbonization pressure not only increases the coking yield but also lowers the temperature at which the pyrolysis is complete. This is seen to hold true for the present set of pitches, having a much wider range of softening points. Further, one of the pitches, earlier reported by us to be a good preforming pitch for carbon-carbon composites, gave an ultimate coking yield of 88% on subjection to a nitrogen pressure of 160×10⁵ Pa at 550 °C followed by ambient pressure carbonization to 900 °C. It thus appears that a carbonization pressure of 160×10⁵ Pa for a suitable preforming pitch can act as a reasonably good alternative to the expensive hot isostatic pressure impregnation carbonization technique employed in the production of carbon-carbon composites.     

Selective recognition of Pr3 + based on fluorescence enhancement sensor

(E)-2-(1-(4-hydroxy-2-oxo-2H-chromen-3-yl)ethylidene)hydrazinecarbothioamide (L) has been used to detect trace amounts of praseodymium ion in acetonitrile–water solution (MeCN/H₂O) by fluorescence spectroscopy. The fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to Pr^3 + ions in MeCN/H₂O (9/1:v/v) solution. The fluorescence enhancement of L is attributed to a 1:1 complex formation between L and Pr^3 +, which has been utilized as the basis for selective detection of Pr^3 +. The sensor can be applied to the quantification of praseodymium ion with a linear range of 1.6 × 10^? 7 to 1.0 × 10^? 5 M. The limit of detection was 8.3 × 10^? 8 M. The sensor exhibits high selectivity toward praseodymium ions in comparison with common metal ions. The proposed fluorescent sensor was successfully used for determination of Pr^3 + in water samples.