Stable Sensor Research Articles

A novel strategy towards the fabrication of highly stable and sensitive non-enzymatic glucose sensor based on Ni3N thin films using high power impulse magnetron sputtering

Glucose level surveillance in mankind is considered the greatest need of recent times to achieve healthy lifestyle goals due to its health-related concern for humans. To fulfill the need, Nickel-based compounds emerge with excellent bio-mimic properties. However, due to the poor electrical properties of oxides and hydroxides of Ni, developing a supporting base that can enhance electron transportation is mandatory. The present work is dedicated to non-enzymatic glucose detection by electrochemical means on the Ni3N thin film on an Indium-doped Tin Oxide (ITO) substrate as a working electrode in an alkaline medium. The Ni3N films use HiPIMS as a deposition technique due to its high ionization rate of sputtered species and dense plasma which helps the Ni ions to react with nitrogen in the formation of a perfect Ni3N phase, and it is a green process that can contribute to sustainable manufacturing. Ni3N thin film deposited at a 60 % N2 flow ratio shows the largest crystallinity and catalytic properties, which helps this modified electrode to have significant potential for glucose detection. The Ni3N modified electrode acquires a lower linear range of 0.001–1.25 mM with sensitivity and Limit of Detection (LOD) of 337.46 µAmM–1cm−2, and 0.78 µM, respectively, and a higher linear range of 1.25–7.3161 mM with a sensitivity of 158.58 µAmM–1cm−2. The amperometric measurements reveal the fast response of the electrode towards glucose detection at 2.46 secs. The key measures of the electrode according to the corresponding measurements are satisfactory selectivity, reproducibility, repeatability, and operational stability. The modified electrode shows a significant response for real samples such as commercially available honey, apple juice, and biological fluids.

Tunable and Stable Refractive Index Sensor Working Near Dispersion Turning Point

Tunable and Stable Refractive Index Sensor Working Near Dispersion Turning Point

Selective Recognition of Lead and Cadmium in Potable Water Using Single Polypyrrole Nanowire Decorated with Cobalt Oxide Nanoparticles Electrode

The fabrication and characterization of a high-performance, robust, and highly sensitive sensor based on a single polypyrrole nanowire (sPpy NW) decorated with cobalt oxide nanoparticles (CoOxNPs) for the selective recognition of lead (Pb2+) and cadmium (Cd2+) in potable water are described in this paper. The electrodeposition technique was used to prepare the sPpyNW/CoOxNPs assembly, and square wave anodic stripping voltammetry (SW-ASV) was used to assess sensor performance. Optimizing sensor performance, such as deposition time, deposition potential, and supporting electrolyte, was used to assess for best sensor performance. The developed sensor exhibited excellent linearity and the linear range for the detection of individual Cd2+ and Pb2+ ions was determined to be 0.00 to 0.11 μM and 0.00 to 0.12 μM, respectively. The detection limits observed for both Pb2+ and Cd2+ sensors are 0.22 μM (R2 = 0.9520) and 0.013 μM (R2 = 0.9723), respectively. The linear range for the detection of Pb2+ and Cd2+ sensors present in the same sample was determined to be 0.00 to 0.09 μM, with a detection limit of 0.026 μM (R2 = 0.8726) and 0.013 μM (R2 = 0.9468) for Pb2+ and Cd2+, respectively. The observed results revealed that the functionalization of CoOxNPs on the surface of a sPpyNW electrode seems to be a very effective way of developing a sensitive, selective, and stable electrochemical sensor for Pb2+ and Cd2+ions.

Ultrasensitive, Highly Stable, and Stretchable Strain Sensor Using Gated Liquid Metal Channel

AbstractDeveloping stretchable strain sensors with high sensitivity and stability is crucial for various applications such as prosthetic hands, human health monitoring, and human‐machine interactions. However, achieving these qualities simultaneously remains challenging. Here, an inherently stretchable strain sensor is presented that integrates ultrahigh sensitivity and robust stability, enabling stretch, press, or bend sensing capabilities. This sensor employs a softer elastomeric channel filled with liquid metal (LM) as the conductive path. A stiffer elastomer convex integrated into the channel serves as a strain‐manipulated gate, controlling opening gap of electrical current flow path. During deformation, the softer elastomer undergoes cross sectional reduction due to the Poisson effect, while the stiffer convex gate retains its geometry. This heterogeneous deformation behavior leads to significant contraction or closure of the LM channel, resulting in increased resistance and a remarkable enhancement in sensitivity by more than two orders of magnitude. The all‐soft design maintains exceptional stability even under extended or repetitive substantial deformations. With the ability to monitor subtle and large human body movements, detect grip actions of soft grippers reliably, and monitor the gradual and extended growth process of plants, this sensor holds significant potential for advancements in flexible electronics.

Highly Sensitive and Mechanically Stable MXene Textile Sensors for Adaptive Smart Data Glove Embedded with Near-Sensor Edge Intelligence

Highly Sensitive and Mechanically Stable MXene Textile Sensors for Adaptive Smart Data Glove Embedded with Near-Sensor Edge Intelligence

Zinc oxide bridges the nanofillers to enhance the wear resistance and stability of triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) have received widespread attention as a means of harvesting mechanical energy from the environment and converting it into electricity. As people continue to explore the field of infinite sensors, traditional TENGs have faced persistent challenges in practical application, mainly due to the poor abrasion resistance and stability of the existing polymers commonly used. Herein, the polyphenylene sulfide (PPS) was melt blended with liquid crystal polymer (LCP) to be used as matrix, and the interfacial bonding strength between the matrix and filler was improved by zinc oxide (ZnO) grafted carbon nanotubes/graphene oxide (CNTs/GO). Under friction conditions of 100 N load and 0.5 m/s, the friction coefficient and wear rate of resultant nanocomposites were significantly reduced to 0.2 and 2.09 × 10-5 mm3/N, respectively. The abrasion resistant TENG (AR-TENG) was fabricated based on 0.3ZnO/CNTs/GO/LCP/PPS exhibited outstanding electrical output performance, which was attributed to the high dielectric constant of 5.3, improved surface roughness and interfacial contact area of composites. Consequently, this study reported a novel approach to tailor AR-TENG into a highly abrasion resistant and stable sensor. This customization enabled the AR-TENG to operate reliably in harsh environments (high temperatures and humidity), thereby expanding its potential applications.

Stretchable, stable and high-performance optoelectronic sensors based on hydrogel for ultraviolet imaging and wireless alarm

Stretchable, stable and high-performance optoelectronic sensors based on hydrogel for ultraviolet imaging and wireless alarm

Highly stable flexible ozone gas sensors using Mn3O4 nanoparticles-decorated IGZO thin films through the SILAR method

Metal or semiconductor nanoparticles (NPs) can enhance the device performance of gas sensors due to their high surface area and unique electronic properties. However, this method requires additional thermal bonding with high temperatures to secure the NPs, making it unsuitable for flexible substrates. In this study, we develop a room-temperature flexible ozone (O3) gas sensor using Mn3O4 NPs on an amorphous InGaZnO (a-IGZO) film. The Mn3O4 NPs are synthesized by a successive ionic layer adsorption and reaction (SILAR) method at low temperatures. The sensor with Mn3O4 NPs exhibits a gas response of 4.06 against 5 ppm O3 gas at room temperature, which is much higher than that of its pristine counterpart. It also shows excellent selectivity for O3 over toxic gases and maintains stability over 60 days, with reproducible folding even after 500 bending cycles. Thus, the combination of SILAR-synthesized Mn3O4 NPs and a-IGZO films provides an effective way to fabricate flexible O3 gas sensors.

Super-Nernstian model based on acid doped polyaniline pH sensor

A polyaniline pH sensor with super-Nernstian sensitivity (>59.12 mV/pH) was obtained through acid doping. After preparing polyaniline sensor by potentiostatic electropolymerization, the electrochemical property of sensor can be modulated by adjusting acid doping formulas. The result shows that when using doping solution containing 2.2 g/L sodium dihydrogen phosphate and 5 g/L sodium chloride at pH = 6, the polyaniline sensor exhibits a linear super-Nernstian behavior (−69.31 ± 1.66 mV/pH) in PBS buffer (pH 5.00 ∼ 9.00). We observed that the surface of electrode has a three-dimensional network structure which can greatly increase the surface area of the sensing film, thus improving the conductivity and the sensitivity of the senor. The mechanism of acid doping is revealed: phosphate and polyaniline form salt, which makes polyaniline change from insulator to metal state and improves the conductivity. This is one important reason for its super-Nernstian behavior. In order to better understand this behavior, a new super-Nernstian model is established. The parameter 1/r > 1 is introduced to represent the acid doping index of the sensor, which directly affects the sensitivity of the film. According to the formula, super-Nernstian behavior of pH sensor can be mathematically modeled. This investigation yields a consistently stable super-Nernstian pH sensor while providing enhanced insights into its super-Nernstian characteristics and underlying mechanisms.

A Stable and Sensitive Engineering Bacterial Sensor via Physical Biocontainment and Two-Stage Signal Amplification.

Although engineering bacterial sensors have outstanding advantages in reflecting the actual bioavailability and continuous monitoring of pollutants, the potential escape risk of engineering microorganisms and lower detection sensitivity have always been one of the biggest challenges limiting their wider application. In this study, a core-shell hydrogel bead with functionalized silica as the core and alginate-polyacrylamide as the shell have been developed not only to realize zero escape of engineered bacteria but also to maintain cell activity in harsh environments, such as extremely acidic/alkaline pH, high salt concentration, and strong pressure. Particularly, after combining the selective preconcentration toward pollutants by functionalized core and the positive feedback signal amplification of engineering bacteria, biosensors have realized two-stage signal amplification, significantly improving the detection sensitivity and reducing the detection limit. In addition, this strategy was actually applied to the detection of As(III) and As(V) coexisting in environmental samples, and the detection sensitivity was increased by 3.23 and 4.39 times compared to sensors without signal amplification strategy, respectively, and the detection limits were as low as 0.39 and 0.86 ppb, respectively.

A highly stable electrochemical sensor with antifouling and antibacterial capabilities for mercury ion detection in seawater

The monitoring of heavy metal ions in ocean is crucial for environment protection and assessment of seawater quality. However, the detection of heavy metal ions in seawater with electrochemical sensors, especially for long-term monitoring, always faces challenges due to marine biofouling caused by the nonspecific adsorption of microbial and biomolecules. Herein, an electrochemical aptasensor, integrating both antifouling and antibacterial properties, was developed for the detection of Hg2+ in the ocean. In this electrochemical aptasensor, eco-friendly peptides with superior hydrophilicity served as anti-biofouling materials, preventing nonspecific adsorption on the sensing interface, while silver nanoparticles were employed to eliminate bacteria. Subsequently, a ferrocene-modified aptamer was employed for the specific recognition of Hg2+, leveraging the aptamer's ability to fold into a thymine-Hg2+-thymine (T-Hg2+-T) structure upon interaction, and bringing ferrocene nearer to the sensor surface, significantly amplifying the electrochemical response. The prepared electrochemical aptasensor significantly reduced the nonspecific adsorption in seawater while maintaining sensitive electrochemical response. Furthermore, the biosensor exhibited a linear response range of 0.01–100 nM with a detection limit of 2.30 pM, and realized the accurate monitoring of mercury ions in real marine environment. The research results offer new insights into the preparation of marine antifouling sensing devices, and it is expected that sensors with antifouling and antimicrobial capabilities will find broad applications in the monitoring of marine pollutants.

A highly stable membrane-free potentiometric pH sensor with nickel cobalt sulfide as the solid contact layer and ion recognition

In this work, a new NiCo2S4 based H+ ion-selective electrode (ISE) without a polymer membrane was proposed and used to rapidly monitor the pH values of wetland soils in the Yellow River Delta in China. This NiCo2S4-based potentiometric pH sensor without an ion-selective membrane (ISM) exhibited a near-Nernstian response slope (50.9 ± 0.4 mV/dec) and good sensitivity. Furthermore, the developed pH sensors using NiCo2S4 as a solid contact (SC) layer present good reproducibility and the standard deviation of Eo is only 0.75 mV (n = 6). The water layer at the SC/ISM interface of the NiCo2S4-based membrane-free potentiometric pH sensor vanished, thus yielding excellent long-term potential stability (8.6 ± 0.4 μV/h over 264 h). This pH sensor offers a new design strategy for the construction of miniaturized highly stable ISEs without ISM.

Environmental Stability Stretchable Organic Hydrogel Humidity Sensor for Respiratory Monitoring with Ultrahigh Sensitivity

AbstractReal‐time monitoring of respiration plays a very important role in human health assessment, especially in monitoring and analyzing respiration during exercise and sleep. However, traditional humidity sensors still have problems in flexibility, sensitivity, and durability, so there is an urgent need to develop humidity sensors with high sensitivity, stretchability, and environmental resistance as respiratory monitoring applications. Here, based on the double network hydrogel structure of polyvinyl alcohol and polyacrylamide, a highly sensitive, highly stretchable, and environmentally stable organic hydrogel humidity sensor has been manufactured by using the synergistic effect of lithium chloride and MXene. The hydrogel humidity sensor shows rapid response in the humidity range of 40–85% RH, and has a high sensitivity of −103.4%/% RH. In addition, it exhibits more than 3000% mechanical strain and excellent environmental resistance, which is attributed to the chemical cross‐linking in the hydrogel network and the synergistic effect of multiple hydroxyl groups in glycerol forming rich hydrogen bonds with water and polymer chains. The hydrogel humidity sensor is used for real‐time monitoring of breathing and sleep processes. This work provides a new strategy for preparing high‐performance, extensibility, and environmental stability hydrogel‐based sensors for respiratory monitoring.

RGO modified α-Fe2O3–ZnFe2O4 heterojunction for improving sensing performance of α-Fe2O3 to triethylamine

In order to develop a sensitive, stable and cheap gas sensor for detection of triethylamine (TEA), the bimetal oxide of ZnFe2O4 with α-Fe2O3 heterojunctions with different proportions were synthesized and reduced graphene oxide (rGO) modified on heterojunctions by hydrothermal and chemical precipitation methods. The gas-sensing tests to TEA showed that the 6α-Fe2O3/ZnFe2O4-rGO (0.8 wt%) composite has highest response reaches 10.48–20 ppm TEA with a rapid response time of 29 s, an impressively low detection limit of 0.145 ppm and reliable stability within 32 days at operating temperature of 143 °C. Compared with reported before, it has higher response at lower operating temperature and lower concentration of test gas. The enhancing mechanism is attributed to the formation of semiconductor heterojunction, which makes the resistance of composite in air further increase and further decrease in TEA compared with α-Fe2O3 due to generating an additional electron depletion layer in the heterojunction interface, while rGO accelerates the electron transfer and provides more active sites for gas adsorption.

Mussel-inspired ionic hydrogel for tactile perception: Toward versatility, robustness and sustainability

The ever-growing wearable and implantable medical devices have spawned an urgent demand for integrating tactile sensors and portable power sources into a single device. However, identifying a suitable material that balances electronic and mechanical performance to simultaneously meet the requirements of high biocompatibility, elasticity, conductivity, and versatility for such soft electronic applications remains a challenge. Here, highly conductive and robust ionic hydrogel is synthesized via a mussel-inspired strategy, where cellulose nanofibers (CNFs) and ZIF-8 particles are introduced into poly(acrylic acid-co-2-(methacryloyloxy)ethyl trimethylammonium chloride) (PADH) matrix for achieving mechanical reinforcement. Besides adhesive strengths of 30.26 kPa, strong hydrogen-bonding central to the embedded CNFs/ZIF-8 joint induces densely cross-linked tough panel points and soft-hard layered network structure that provide tensile strength of 110 kPa, elongation at break up to 697 % (increased by ∼2.2 times and ∼1.9 times, respectively) and compressive strength of 984 kPa. Excellent self-healing (89 % within 12 h) and self-adhesion capabilities (adhesion strength of about 30.26 kPa) are also witnessed, which can be attributed to the reversibility of the abundant hydrogen bonds. Meanwhile, the ion-rich tunnels promoted by the migration of IL/Gly/H2O ternary solvent system (EgHTS) not only significantly enhance the ionic conductivity, but also improve temperature tolerance and provide prolonged resistance to dehydration. The dynamical balance of the electric double layers at the CNF-ZIF-PADH interface leads to highly stable and durable hybrid triboelectric-piezoresistive sensors that are capable identifying both the physical characteristic of dynamic objects and static forces while harvesting mechanical energy, thus enabling versatile, robust, temperature-tolerant conductive hydrogels for self-powered soft electronics.

Bulk Trapping Organic Semiconductor with Amino-Additive Enabling Ultrasensitive NO2 Sensors.

Organic semiconductor (OSC) gas sensors have garnered considerable attention due to their promising selectivity and inherent flexibility. Introducing a functional group or modification layer is an important route to modulate the doping/trapping state of the active layer and the gas absorption/desorption process. However, the majority of the functionalization lies in the surface/interface assembling process, which is difficult to control the functional group density. This in turn brings challenges for precise modulation of the charge transport and the doping/trapping density, which will affect the repeatability and reproducibility of sensing performance. Herein, we propose a facile bulk trapping strategy incorporating amino-terminated additive molecules via the vacuum deposition process, achieving ultrahigh sensitivity of ∼2000%/ppm at room temperature to NO2 gas and approaching ∼3000%/ppm at 50 °C. Additionally, the device exhibits commendable reproducibility, stability, and low concentration detection ability, reaching down to several ppb, indicating promising potential for future applications. Comprehensive analysis of electrical properties and density functional theory calculations reveals that these exceptional properties arise from the favorable electrical characteristics of the bulk trapping structure, the high mobility of C8-BTBT, and the elevated adsorption energy of NO2. This approach enables the construction of stable and reproducible sensitive sensors and helps to understand the sensing mechanism in OSC gas sensors.

Developing excellent plantar pressure sensors for monitoring human motions by using highly compressible and resilient PMMA conductive iongels

Based on real-time detection of plantar pressure, gait recognition could provide important health information for rehabilitation administration, fatigue prevention, and sports training assessment. So far, such researches are extremely limited due to lacking of reliable, stable and comfortable plantar pressure sensors. Herein, a strategy for preparing high compression strength and resilience conductive iongels has been proposed by implanting physically entangled polymer chains with covalently cross-linked networks. The resulting iongels have excellent mechanical properties including nice compliance (young’s modulus < 300 kPa), high compression strength (>10 MPa at a strain of 90 %), and good resilience (self-recovery within seconds). And capacitive pressure sensor composed by them possesses excellent sensitivity, good linear response even under very small stress (∼kPa), and long-term durability (cycles > 100,000) under high-stress conditions (133 kPa). Then, capacitive pressure sensor arrays have been prepared for high-precision detection of plantar pressure spatial distribution, which also exhibit excellent sensing performances and long-term stability. Further, an extremely sensitive and fast response plantar pressure monitoring system has been designed for monitoring plantar pressure of foot at different postures including upright, forward and backward. The system achieves real-time tracking and monitoring of changes of plantar pressure during different static and dynamic posture processes. And the characteristics of plantar pressure information can be digitally and photography displayed. Finally, we propose an intelligent framework for real-time detection of plantar pressure by combining electronic insoles with data analysis system, which presents excellent applications in sport trainings and safety precautions.

Highly Sensitive and Stable Flexible Smart Sensors Based on Commercial Carbon Fiber Powder Inks.

With the fast development of the smart lifestyle in recent years, simple and flexible body condition monitoring has become more and more important. However, currently, commercially available motion-sensing devices always lack flexibility or at a high cost. This article has fully explored the merits of a commercial and easily available material of carbon fiber powder (CFP) and prepared CFP-based screen printing inks. This conductive ink can be directly and quickly printed onto a variety of different flexible common substrates, such as paper, cotton fabrics, etc., to prepare flexible sensors. At the same time, as a result of the good photothermal performance and conductivity of CFP, the printed flexible sensors have fast and stable performance on thermal and human motion detection. The use of CFP as the smart element to construct a wearable device will offer a choice for the intelligent industry.

Tuning electrochemical water activation over NiIr single-atom alloy aerogels for stable electrochemiluminescence

The anodic oxygen evolution reaction is a well-acknowledged side reaction in traditional aqueous electrochemiluminescence (ECL) systems due to the generation and surface aggregation of oxygen at the electrode, which detrimentally impacts the stability and efficiency of ECL emission. However, the effect of reactive oxygen species generated during water oxidation on ECL luminophores has been largely overlooked. Taking the typical luminol emitter as an example, herein, we employed NiIr single-atom alloy aerogels possessing efficient water oxidation activity as a prototype co-reaction accelerator to elucidate the relationship between ECL behavior and water oxidation reaction kinetics for the first time. By regulating the concentration of hydroxide ions in the electrolyte, the electrochemical oxidation processes of both luminol and water are finely tuned. When the concentration of hydroxide ions in electrolyte is low, the kinetics of water oxidation is attenuated, which limits the generation of oxygen, effectively mitigates the influence of oxygen accumulation on the ECL strength, and offers a novel perspective for harnessing side reactions in ECL systems. Finally, a sensitive and stable sensor for antioxidant detection was constructed and applied to the practical sample detection.

Moisture reaction mechanism of Au-modified SnO2 ultrathin nanosheets with exclusive detection of formaldehyde

Exploring the reaction mechanism at the molecular level in detecting different target gases and providing the optimal operating temperature can improve selective detection performance and extend the lifetime of chemiresistors in practical sensing applications. While the humidity effect interaction mechanism between gas and sensor hinders its practical application. Therefore, exploring the reaction mechanism of humidity to detect different target gases at the molecular level can promote the development of exclusive detection performance and service life of sensors. To further disclose this, a one-step chemical method is applied to synthesize the defect-rich SnO2 with an ultrathin nanosheet structure. The experimental results confirmed that the inhibitory effect of humidity on the detection of formaldehyde by Au-SnO2 is significantly lower than that of other interfering volatile organic compounds (VOCs). The response value of Au-SnO2 detect 10 ppm of formaldehyde at 55 °C is 78, which is larger than that of methanol, ethanol, and acetone. This study sheds light on the mechanistic insight into the correlation between operating temperatures and humidity on the excellent performance of the Au-SnO2 chemiresistive sensor. We consider our work significant in developing highly efficient and stable electrochemical sensors to detect VOC gases at room temperature.