Sensor Material Research Articles

Tailoring of Ultrasmall NiMnO3 Nanoparticles: Optimizing Synthesis Conditions and Solvent Effects

Nickel manganese oxide (NiMnO3) combines magnetic and dielectric properties, making it a promising material for sensor and supercapacitor applications, as well as for catalytic water splitting. The efficiency of its utilization is notably influenced by particle size. In this study, we investigate the influence of thermal treatment parameters on the phase composition of products from alkali co-precipitation of nickel and manganese (II) ions and identify optimal conditions for synthesizing phase-pure nickel manganese oxide. Ultrafine nanoparticles of NiMnO3 (with sizes as small as 2 nm) are obtained via liquid-phase ultrasonic dispersion, exhibiting a narrow size distribution. A systematic exploration of the solvent nature (water, N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide) on the efficiency of ultrasonic dispersion of NiMnO3 nanoparticles is provided. It is demonstrated that particle size is influenced not only by absorbed acoustic power, dependent on the physical properties of the used solvent (boiling temperature, gas solubility, viscosity, density) but also by the chemical stability of the solvent under prolonged ultrasonic treatment. Our findings provide insights for designing ultrasonic treatment protocols for nanoparticle dispersions with tailored particle sizes.

Anisotropic Redox on Pristine Graphene

AbstractChemically modified graphene is an attractive electrode material for electrocatalysis, energy devices, and sensors, whereas pristine graphene is electrochemically passive. The remarkable anisotropic electrochemical nature of graphene is uncovered by π–π interaction, making pristine graphene more active than bare Au. The π–π stacking during redox reaction “dopes” the graphene, disrupting the passivating hydration layer, making it a facile electrochemical electrode. The structure during π–π stacking‐mediated redox of methylene blue (MB) is quantitatively measured by the differential reflectivity of a polarized laser on a ≈100 micron spot. The local redox reaction current varies over fourfold due to the orientation of the ≈10 micron size grains. The mosaic‐grain anisotropy on each spot shows local uniaxial orientation. The redox signal at the optimum orientation is over 2.5‐fold greater than that for bare Au on the same electrode. The redox signal is over fivefold greater at the edges of graphene compared bare Au. Remarkably, the π–π interaction increases chemical stability significantly, leading to negligible photo‐degradation at the approximate absorption wavelength of MB. The exclusive redox activity due to π–π interaction on pristine graphene adds to the toolbox of making exotic opto‐electrochemical electrode materials for electrocatalysis, sensing, and electronics.

Study of the magnetic and structural properties of the simple perovskite YFeO3

In the present work, an experimental and theoretical study of the synthesis, magnetic, and structural properties of simple perovskite compounds YFeO3 has been investigated based on their potential applications, such as: solid oxide fuel cells, electrochemical sensors, sensor materials, magneto-optical materials, etc. Experimentally, the synthesis was carried out by the sol-gel method. X-rays and Rietveld refinements confirmed the orthorhombic structure. Scanning electron microscopy observations confirmed agglomerates of simple perovskite particles YFeO3. The study of the magnetic phase of the simple perovskite YFeO3 showed that it behaves like a weak ferromagnetic, this property delimits and directs magnetic fields into well-defined trajectories. On the other hand, the structural results, from a theoretical point of view, are in good agreement with the experimental ones. Through energy comparison, a possible competition was identified between the FM and AFM states, where the electronic properties are associated with the directional nature of the hybridization between the p orbitals of oxygen and the t2g states, where the superexchange mechanism prevails with e oxygen as mediator.

Angle-dependent ion-beam etching of RuAl thin films for structuring GHz-frequency electronics

The ruthenium aluminide (RuAl) alloy is a promising electrode material for wireless surface acoustic wave sensors working under harsh conditions at high temperatures. However, during the structuring of RuAl thin films using ion-beam etching, etched material can redeposit at the edges of the electrodes and form objects, so-called fences, on top of the structured features. These decrease the high-temperature stability and lead to an undesired alteration of the sensor performance. In this work, the angle-dependent ion-beam etching of RuAl thin films was investigated to inhibit the formation of such fence structures. The etch rate was determined as a function of the etching angle between ion-beam and sample surface in a range between 90° and 40°. Furthermore, finger structures with pitches below 500 nm, which are required for devices working in the intended GHz regime, were patterned to study the influence of the etching angle on the profile of the RuAl electrode fingers using transmission electron microscopy and energy-dispersive x-ray spectroscopy. The results show that an etching angle of 50° results in the highest etch rate. For etching angles of 50° and below, the width of the fences is reduced below 10 nm, so they break off during standard resist removal procedures. Such low etching angles lead to shadowed areas on the side of structured features in which unetched material remains. However, this material can be removed by using a two-step etching process combining a 50° step with a 90° step. This process is capable of structuring fence-free trapezoidal-shaped electrode finger profiles. Therefore, the developed process is well suited for the fabrication of high-temperature GHz-frequency RuAl electrodes.

An intelligent CFRP bolt with embedded carbon nanotube eddy current sensors for damage self‐diagnosis of bolted composite joints

AbstractRecognizing the critical demand for composite bolts and the damage‐mode complexity of composite bolt joints, this study introduces the concept of an intelligent carbon fiber reinforced polymer (CFRP) bolt, which achieves self‐monitoring of damage in small and complex CFRP bolted joints. The proposed eddy current sensor (ECS) is mainly composed of a coil made of carbon nanotube film and encapsulated with epoxy resin film. This achieves homogeneous embedding of the sensor by using the same material for both sensor and bolt. The CFRP bolt is fabricated by molding process, with the proposed ECS embedded in bolt shank. The numerical simulation results indicate that hole‐edge damages impact the distribution of induced current density and eddy current flow in CFRP plates. Additionally, the impedance amplitude of the ECS effectively monitors bearing damage propagation. Shear tests confirm that the integration method of the proposed ECS within the CFRP bolt introduces negligible intrusion to the host bolt's integrity. Experimental results demonstrate that the intelligent CFRP bolt can effectively monitor the damage propagation at the hole edge, with an accuracy for bearing damage exceeding 0.5 mm. At a working frequency of 10 MHz, the sensor's sensitivity in detecting a 0.5 mm bearing damage reaches 4.20%.Highlights An intelligent CFRP bolt was fabricated using the molding method. The embedding of the ECS did not cause adverse effects on the bolt. The proposed EC sensor is composed of carbon nanotube and epoxy resin adhesive films. The eddy current distribution at the hole edge of the CFRP bolted joints is analyzed. The ability of intelligent bolts to monitor hole edge damage is verified by experiments.

Reaction-driven restructuring of defective PtSe2 into ultrastable catalyst for the oxygen reduction reaction.

PtM (M = S, Se, Te) dichalcogenides are promising two-dimensional materials for electronics, optoelectronics and gas sensors due to their high air stability, tunable bandgap and high carrier mobility. However, their potential as electrocatalysts for the oxygen reduction reaction (ORR) is often underestimated due to their semiconducting properties and limited surface area from van der Waals stacking. Here we show an approach for synthesizing a highly efficient and stable ORR catalyst by restructuring defective platinum diselenide (DEF-PtSe2) through electrochemical cycling in an O2-saturated electrolyte. After 42,000 cycles, DEF-PtSe2 exhibited 1.3 times higher specific activity and 2.6 times higher mass activity compared with a commercial Pt/C electrocatalyst. Even after 126,000 cycles, it maintained superior ORR performance with minimal decay. Quantum mechanical calculations using hybrid density functional theory reveal that the improved performance is due to the synergistic contributions from Pt nanoparticles and the apical active sites on the DEF-PtSe2 surface. This work highlights the potential of DEF-PtSe2 as a durable electrocatalyst for ORR, offering insights into PtM dichalcogenide electrochemistry and the design of advanced catalysts.

Pd-anchored VSe2 for glucose sensing: Prediction from first principle simulations

Accurate detection of glucose molecule is clinically important for treatment of diabetes. The sensor should efficiently detect the glucose molecule with suitable response time. The conductivity of the sensor material thus plays a vital role in fast and precise sensing. Layered vanadium di-selenide (VSe2) is a transition metal dichalcogenide (TMDC) with metallic characteristics. The current study is to portray a theoretical exhaustive investigation about enhancement in effectual detection of glucose using VSe2 decorated with transition metals (TM) such as Ag and Pd. We have performed extensive DFT simulations to relate adsorption energy of glucose with pristine and decorated VSe2. Introduction of TM to pristine VSe2 was found to increase the adsorption energy of glucose which increases the sensitivity of metal- anchored VSe2. Comprehensive partial density of states (PDOS) and total density of states (TDOS) analysis has been carried out to analyse orbital interaction and qualitative charge transfer which has also been measured using Bader charge analysis. In addition to that, permanency of the best decorated system has been verified through molecular dynamics calculation and modality of recurrent serviceability has been determined by means of recovery time estimation. This is crucial since as on today, most of the available glucose detectors are meant for single usage. Our theoretically derived findings clearly point to the prediction that TM-decorated layered VSe2 can be an efficient glucose sensor, if practically developed in forthcoming times. The obtained results will thus potentially be beneficial for experimentalists for scheming and evolving VSe2-based glucose sensors.

Monolayer Penta-BeAs2: A Promising 2D Materials for Toxic Gas Sensor with High Selectivity.

The discovery of novel materials with high gas sensing selectivity is a key driver of gas sensor technology. Based on the recently reported two-dimensional (2D) pentagonal BeP2, we introduce penta-BeAs2 as a new member of the pentagonal family of materials for toxic gas sensors based on density functional theory (DFT). For electronic applications, a band structure calculation showed that penta-BeAs2 has indirect band gaps of 0.38 and 0.79 eV, using GGA-PBE or HSE functionals. Stability analysis confirmed that penta-BeAs2 is dynamically, mechanically, and thermally stable. The adsorption of toxic gases (CO, NO, and NO2) and nontoxic gases (H2, N2, H2O, and CO2) on the penta-BeAs2 monolayer was studied. The contrasting adsorption behavior observed between toxic and nontoxic gases on penta-BeAs2 (physisorption vs chemisorption) underscores its high selectivity for toxic gas-sensing applications. Adsorption energies for toxic gases fall within a moderate range (0.4-0.8 eV), indicating good reversibility and short recovery times at room temperature. Additionally, the quantum transport properties of penta-BeAs2 were studied using the nonequilibrium Green's function (NEGF) approach, confirming strong sensitivity and selectivity toward toxic gases.

N-n type In2O3@-WO3 heterojunction nanowires: enhanced NO2 gas sensing characteristics for environmental monitoring.

Solvothermal synthesis of 1D n-In2O3@n-WO3 heterojunction nanowires (HNWs) and their NO2 gas sensing characteristics arereported. The n-In2O3@n-WO3 HNWs have been well-characterised using XRD, Raman spectroscopy, XPS, SEM and HRTEManalyses. The NO2 sensing performance of n-In2O3@n-WO3 HNWs showed superior performance compared withpristine WO3 NWs. Due to the distinctive configuration of WO3-In2O3 heterojunctions, the n-In2O3@n-WO3 HNWs demonstrated remarkable sensitivity reaching 182% in response towards 500ppb of NO2 gas at operating temperature of 200°Cwhich is nearly 3.5 times greater than the response observed with pristine WO3 (50%). Moreover, the n-In2O3@n-WO3 HNWs also exhibited fast response (8-13s)/recovery (54-62s) time characteristics. A plausible sensing mechanism has been discussed. The enhancement in sensor characteristics shows that n-In2O3@n-WO3 HNWs could serve as a promising material for high-performance NO2 gas sensors for real-time environmentalmonitoringapplications. This work could provide new understandings of the sensing mechanism of n-In2O3@n-WO3-based heterojunction nanowires, which can be applied to the design of novel n-n type MOS heterojunction materials for the application of low-temperature real-time high-performance NO2 sensors.

Shape controlled synthesis and crystal facet dependent gas sensitivity of tungsten oxide

Gas sensors can achieve remarkable functionality through the optimization of particle size, shapes, crystal facets, and oxygen defects, resulting in unsaturated coordination atoms, high charge densities, and enhanced bond energies. In this study, WO2.72 nanourchins, WO3-x nanowires, and WO3 nanorods/nanocube with (010), (001), (200), and (002) dominant crystal facets were synthesized and used as gas sensing materials. It was found that WO2.72 nanourchins exhibit an excellent response of Ra/Rg=21 to 100 ppm acetone with good selectivity among other sensors as-fabricated. First-principle calculations of Density Functional Theory were performed on acetone's adsorption on different crystal planes of tungsten oxide. The results verify spontaneous and fast adsorption on the (010) crystal plane than on the (001) and (200) planes. Further characterizations indicate that WO2.72 nanourchins with (010) crystal facets contain more reactive sites with high surface energy, facilitating charge separation, increasing charge carrier mobility, and enabling the redox reactions to occur independently at different rates. Moreover, their richer electron-donor surface oxygen defects, smaller feature sizes, and higher surface area (SBET) with hierarchical porous structures, all contribute to the enhanced acetone sensing. Our work provides a strategy for improved acetone sensing based on optimizing the particle shape with different crystal facets and oxygen vacancy density. We further expect our strategy to be applicable in designing other sensor materials with efficient charge separation and fast surface redox reactions to detect toxic gases.

Processing and development of ferroelectric Bi(Fe2/3V1/3)O3-based electronic material for temperature sensor

Processing and development of ferroelectric Bi(Fe2/3V1/3)O3-based electronic material for temperature sensor

TFE Terpolymers: Once Promising - Are There Still Perspectives in the 21st Century? Part II: Processing, Properties, Applications.

Tetrafluoroethylene (TFE) terpolymers have emerged as advantageous substitutes for polytetrafluoroethylene (PTFE). Therefore, they are being considered as alternatives to PTFE in many application areas. The advantages of TFE terpolymers include their facile processability at elevated temperatures, their solubility in some polar organic solvents, their inertness against aqueous acids, aqueous bases and a large number of mostly nonpolar organic solvents, their low dielectric constant, their low refractive index as well as useful electro- and thermochemical properties. This review on TFE terpolymers focuses on their processing including shaping and surface modification as well as on selected properties including wettability, dielectric properties, mechanical response behavior, chemical stability, and degradability. Applications including their use as elastomeric sealing material, liner and cladding layer as well as their use as material for membranes, microfluidic devices, photonics, photovoltaics, energy storage, energy harvesting, sensors, and nanothermitic composites will be discussed. The review concludes with a discussion of the future potential of TFE terpolymers and scientific challenges to be addressed by future research on TFE terpolymers.

Interface engineering of NiCo LDH and 2D materials for advanced non-invasive glucose sensors

Interface engineering of NiCo LDH and 2D materials for advanced non-invasive glucose sensors

Multifunctional organohydrogels enabling sensitive strain sensing and self-powered triboelectricity

Hydrogels have broad application prospects in portable strain sensors and triboelectric nanogenerators (TENG), and have attracted great attention in the field of wearable electronic devices and energy transfer devices. However, the development of multifunctional gels that can meet a variety of application scenarios is still a challenging problem. In this study, a multifunctional poly(acrylamide-co-2-acrylamide-2-methylpropanesulfonic acid)/lignosulfonate/Zr4+ organohydrogel noted as “P(AM-co-AMPS)/LS/Zr4+” was fabricated based on dynamic metal coordination bonds and hydrogen bonds, which could be used as flexible strain sensor and TENG electrode material. The organohydrogel based strain sensor could monitor both large and tiny human movements due to the high sensitivity (GF = 4.37, up to 200 %) and circulation stability. The assembled organohydrogel-based triboelectric nanogenerator (O-TENG) could generate an open-circuit voltage of 70.47 V and a short-circuit current of 25.21 μA. It is worth mentioning that the O-TENG could light up 44 LED bulbs by tapping with the palm at −20 °C, and the electronic output performance of the O-TENG after self-healing was unaffected. Additionally, the O-TENG exhibited enormous potentials in the biomechanical energy harvesting and self-powered motion sensors in the areas of human movements detection, human–computer interaction, electronic skin and self-powered devices.

Novel Ag-Doped- Poly (aniline-co-pyrrole)/Titanium-Dioxide Nanocomposite Sensor Material for Ammonia Detection in Spoiled Meat

Silver-doped poly(aniline-co-pyrrole)/titanium dioxide (Ag-doped PANI-PPy/TiO2) conducting copolymer-based nanocomposite ammonia gas sensor was synthesized through in situ chemical oxidative polymerization by taking different amounts (4%, 5%, 6%, 7%, and 8%) of Ag-TiO2 (1:1 ratio) nanoparticles. Zetasizer; dynamic light scattering, scanning electron microscopy, transmit ion electron microscopy, Fourier transform infrared, X-ray diffraction, UV–vis spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and cyclic voltammetry characterization techniques were used to confirm the real formation of nanocomposites and to evaluate the detection performance of the sensor. The interaction sensitivity of the synthesized nanocomposite sensor with ammonia (NH3) was determined by changing the amounts of nanoparticles. Spectroscopic determination exhibited excellent porosity and a better shift in the absorption bands having band gaps (1.87 eV) for the Ag-doped PANI-PPy/TiO2 nanocomposite sensor than the PANI-PPy copolymer (3.17 eV). Morphological (10 μm) and nanoparticle arrangement studies (20 μm) have shown the uniform allocation of nanoparticles in the copolymer matrix when 6% of Ag-TiO2 (1:1 ratio) was added, while agglomeration occurred when <6% or >6% of Ag-TiO2 was added to the copolymer. A decrease in the amorphous domain of the copolymer with an increase in nanoparticles was observed from the X-ray diffraction and other results.

Ca2HfSi4O12:Eu2+: A novel blue phosphor with excellent temperature sensitivity for temperature sensor and cathodoluminescence properties for field-emission displays

A new silicate blue phosphor Ca2HfSi4O12:Eu2+ (CHSO:Eu2+) was designed and synthesized via a solid-state reaction. The structure of CHSO:Eu2+ was analyzed by structure refinement. The electronic structure of CHSO was calculated using first-principles calculations, revealing its effect on luminescence and long-persistent properties. Owing to the O vacancies in the crystal structure, undoped CHSO showed wide blue emission (400–650 nm, λmax = 486 nm) under 296 nm excitation. After being irradiated with a UV lamp for 10 min, the CHSO sample showed obvious afterglow properties that could persist for approximately 50 min above the recognizable intensity level (≥0.32 mcd m−2). CHSO:Eu2+ exhibited excellent temperature sensitivity with a relative sensitivity of 4.5 % K−1@473K, which is higher than those of other Eu2+-based temperature sensor materials. The mechanism between thermal quenching and electronic structure was proposed. Moreover, CHSO:Eu2+ shows excellent cathode ray saturation and aging resistance. This study provides a potential temperature sensor, field-emission-display material, and theoretical reference for developing high-sensitivity temperature-sensing materials.

Synthesis of NiO-SnO2 cauliflower-like gas sensor material using a facile hydrothermal method for acetone detection

Abstract The present study has successfully synthesized a cauliflower-like hierarchy microstructure of NiO-SnO2 through a facile and cost-effective hydrothermal method for acetone detection. S2 sensor, containing 0.25 mole% Ni, exhibited great performance in acetone gas sensing, with a response of 1734 at 1000 ppm at 350°C, two times more than pristine SnO2. At lower concentrations, the responses were recorded to be 325, 170, 70, and 35 for 200 ppm, 100 ppm, 50 ppm, and 20 ppm of acetone balanced in nitrogen, respectively. Moreover, at the optimal operating temperature, 350°C, swift response and recovery times of 8 seconds and 2 minutes 18 seconds were recorded when exposed to 20 ppm of acetone balanced in nitrogen, respectively. Also, the sensor was further assessed for its ability to distinguish acetone from other gases by exposing it to equal concentrations of 200 ppm of acetone, carbon dioxide, ammonia, and ethanol, all balanced in nitrogen, and tested at 350°C. The sensor showed 142.74, 143.39, and 2.42 times higher responses in acetone than carbon dioxide, ammonia, and ethanol, respectively, indicating outstanding selectivity for detecting acetone. Lastly, the sensor showed remarkable operational stability when tested over repeated exposure cycles of acetone gas.&amp;#xD;

Adsorption of NH [formula omitted], HCHO and C[formula omitted]H[formula omitted] onto Y-modified MoS[formula omitted] monolayer : A DFT study

The detection of indoor hazardous gases poses significant complexity and challenges. Based on first-principles theoretical calculations, Y-adsorbed MoS2 (Y-MoS2) monolayer is selected to investigate its adsorption, magnetism and sensitivity to NH3, HCHO and C6H6 gas molecules. The presence of Y atom profoundly alters the electronic and magnetic properties of MoS2 while enhancing its gas adsorption capability. The adsorption capacity of Y-MoS2 monolayer for these indoor hazardous gases follows the order: HCHO ¿ C6H6 ¿ NH3. Notably, at temperatures around 500 K, the Y-MoS2 monolayer exhibits potential as a sensor material for NH3 based on an analysis of recovery performance in the adsorption system. Although the Y-MoS2 monolayer is not suitable for gas sensing applications with regards to HCHO and C6H6, it can be effectively employed as a gas cleansing substance. These findings provide valuable insights into detecting indoor hazardous gases and contribute to our understanding of the gas sensing mechanisms exhibited by MoS2 materials.

Swift and Cost-Effective Detection of Nitrite in Environmental Samples Using Ru@Pt Modified PGE

The development of a straightforward method is crucial for detecting and quantifying nitrite ions within the surrounding environment. This study involves the electrochemical fabrication of a bi-metallic alloy composed of Ruthenium and Platinum on a graphene-modified pge, the first-ever electrodeposition on pencil graphite (RuNPs@PtNPs/Gr-CHI). This study aims to establish a highly responsive and specific approach for identifying nitrite ions while demonstrating the efficacy of a commercially available pencil graphite electrode in detecting this environmental contaminant. The prevalence and structural characteristics of bimetallic nanoalloy particles are confirmed through X-ray diffraction, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The composite exhibited a core–shell shape at a size of 26.998 nm. The electrooxidation of nitrite at RuNPs@PtNPs/Gr-CHI/PGE was investigated using differential pulse voltammetry. The results demonstrated a satisfactory linear relationship from 0.025 mM to 1.625 mM. The method revealed a low detection limit of 0.33 μM. The composite electrode exhibited favorable outcomes regarding selectivity, sensitivity (25.5 μAμM−1cm−2), and repeatability, which are desirable characteristics of the electrochemical sensor material. The constructed electrode underwent testing for five weeks to determine the stability. The suggested sensor’s capability is demonstrated by detecting nitrite ions in real samples such as water, soil, and fruit juice.

Tetrapyrrolic macrocycles self-organization into floating layers and sensory properties of their Langmuir-Schaefer films

The influence of the chemical structure of the 5,10,15,20-tetraphenylporphyrin (I) and 2-aza-21-carba-5,10,15,20-tetraphenylporphyrin (II) on their supramolecular organization in floating layers at the air/water interface and sensor properties in Langmuir-Schaefer films has been investigated. It was shown that a minor change in the macrocycle structure (namely, the replacement of a single nitrogen atom from the center to the periphery of macrocycle) has a considerable effect on the surface properties and hysteresis processes of the floating layers. Using the Bruster angle microscopy, it was established that both porphyrins aggregate even before the compression of their floating layers begins. The aggregation is more pronounced in porphyrin I. The analysis of hysteresis loops showed that the formation of a floating layer by the modified porphyrin II requires approximately 100 times more energy than for the unmodified porphyrin I. Using the Langmuir-Schaefer (LS) method, the floating layers were transferred onto solid substrates and the resulting thin films were analyzed by atomic force microscopy, scanning electron microscopy, polarization optical microscopy, and spectrophotometry. The combination of these methods revealed a general tendency of the porphyrins to form 3D structures on the surface of LS-films. The study of the basic properties of the porphyrin's LS-films showed that both porphyrins are diprotonated. The protonation process in porphyrin II occurs at a concentration of HClO4 that is 1000 times lower than that observed in porphyrin I. The greater tendency to protonation of porphyrin II is caused by the availability of both nitrogen atoms (the external nitrogen atom located at the macrocycle periphery and the internal nitrogen atom, which becomes more assesible to interactions due to the distortion of the macrocycle). As for the sensor properties of LS-films for iodide ion in aqueous solutions, it was observed that the diprotonated form of porphyrin I exhibited higher sensitivity due to a more developed film surface because of the presence of a greater number of 3D aggregates. The data obtained can be used in the development of efficient pH-controlled thin-film sensor materials for halide ions.