Response Time Of Sensor Research Articles

Layer-by-Layer Deposited Multi-Modal PDAC/rGO Composite-Based Sensors.

Different environmental parameters, such as temperature and humidity, aggravate food spoilage, and different volatile organic compounds (VOCs) are released based on the extent of spoilage. In addition, a lack of efficient monitoring of the dosage of pesticides leads to crop failure. This could lead to the loss of food resources and food production with harmful contaminants and a short lifetime. For this reason, precise monitoring of different environmental parameters and contaminations during food processing and storage is a key factor for maintaining its safety and nutritional value. Thus, developing reliable, efficient, cost-effective sensor devices for these purposes is of utmost importance. This paper shows that Poly-(diallyl-dimethyl ammonium chloride)/reduced Graphene oxide (PDAC/rGO) films produced by a simple Layer-by-Layer deposition can be effectively used to monitor temperature, relative humidity, and the presence of volatile organic compounds as indicators for spoilage odors. At the same time, they show potential for electrochemical detection of organophosphate pesticide dimethoate. By monitoring the resistance/impedance changes during temperature and relative humidity variations or upon the exposure of PDAC/rGO films to methanol, good linear responses were obtained in the temperature range of 10-100 °C, 15-95% relative humidity, and 35 ppm-55 ppm of methanol. Moreover, linearity in the electrochemical detection of dimethoate is shown for the concentrations in the order of 102 µmol dm-3. The analytical response to different external stimuli and analytes depends on the number of layers deposited, affecting sensors' sensitivity, response and recovery time, and long-term stability. The presented results could serve as a starting point for developing advanced multi-modal sensors and sensor arrays with high potential for analytical applications in food safety and quality monitoring.

Carbon nanotubes field-effect transistor pressure sensor based on three-dimensional conformal force-sensitive gate modulation

Pressure sensors based on field-effect transistor mechanism has received a lot of attention from researchers, which can effectively suppress low contrast and crosstalk effects. In this paper, we demonstrate a pressure sensor based on carbon nanotube field-effect transistor (CNTs-FET) and three-dimensional conformal force-sensitive top electrode with high sensitivity and easy integration. The high mobility field-effect transistor sensors were prepared using CNTs films with 99.9999% semiconductor concentration as the channel material. Conformal graphene nanowalls (GNWs) film on pyramidal micro-structure arrays worked as force-sensitive top electrode, the field-effect transistor sensor shows a sensitivity of 946.23 kPa−1 and 43.79 kPa−1 in the linear range of 0–30 Pa and 0.03–10 kPa, much higher than piezoresistive sensor (the sensitivity of about 377.73 kPa−1) and capacitive sensor (the sensitivity of 115.78 kPa−1). And the sensitivity and range of the sensor can be adjusted by the force-sensitive layer orientation design. Additionally, the sensor's response time is less than 30 ms, the recovery time is about 30 ms. The field-effect pressure sensor could detect ultra-low pressure (about 1.3 mg) of the chrysanthemum petals, and also could record the dynamic crawling process of the insect.

A Review of Biosensors and Their Applications

Abstract This paper reviews sensors with nano- and microscale dimensions used for diverse biological applications. A biosensor converts biological responses into electrical signals. In recent years, there have been significant advancements in the design and development of biosensors that generated a large spectrum of biosensor applications including healthcare, disease diagnosis, drug delivery, environmental monitoring, and water and food quality monitoring. There has been significant work to enhance the performance of biosensors by improving sensitivity, reproducibility, and sensor response time. However, a key challenge of these technologies is their ability to efficiently capture and transform biological signals into electric, optic, gravimetric, electrochemical, or acoustic signals. This review summarizes the working principle of a variety of biosensors in terms of their classification, design considerations, and diverse applications. Other lines of research highlighted in this paper are focused on the miniaturization of biosensing devices with micro and nano-fabrication technologies, and the use of nanomaterials in biosensing. Recently wearable sensors have had important applications such as monitoring patients with chronic conditions in home and community settings. This review paper mentions applications of wearable technology. Machine learning is shown to help discover new knowledge in the field of medical applications. We also review artificial intelligence (AI) and machine learning (ML)-based applications.

Rapid and Finely-Tuned Expression for Deployable Sensing Applications.

Organisms from across the tree of life have evolved highly efficient mechanisms for sensing molecules of interest using biomolecular machinery that can in turn be quite valuable for the development of biosensors. However, purification of such machinery for use in in vitro biosensors is costly, while the use of whole cells as in vivo biosensors often leads to long sensor response times and unacceptable sensitivity to the chemical makeup of the sample. Cell-free expression systems overcome these weaknesses by removing the requirements associated with maintaining living sensor cells, allowing for increased function in toxic environments and rapid sensor readout at a production cost that is often more reasonable than purification. Here, we focus on the challenge of implementing cell-free protein expression systems that meet the stringent criteria required for them to serve as the basis for field-deployable biosensors. Fine-tuning expression to meet these requirements can be achieved through careful selection of the sensing and output elements, as well as through optimization of reaction conditions via tuning of DNA/RNA concentrations, lysate preparation methods, and buffer conditions. Through careful sensor engineering, cell-free systems can continue to be successfully used for the production of tightly regulated, rapidly expressing genetic circuits for biosensors.

Highly sensitive ammonia sensor using newly synthesized carbazole based hypercrosslinked polymer and tin dioxide

Tin Dioxide (SnO2), carbazole based hypercrosslinked polymer (C-HCP), and C-HCP/SnO2 nanocomposites by different C-HCP weight percent concentration (0.05–0.15 %wt.) were synthesized by precipitation method and used as sensing materials for ammonia sensor. These materials were applied for ammonia detection in various temperature (100–350 °C) and ammonia concentration (100, 200, and 300 ppm). The electrical conductivity of materials was measured at different temperature and decreasing of electrical conductivity observed by temperature increasing. The resistance of sensor in air to that in presence of ammonia was considered as sensor response. According to the results, SnO2 had much greater conductivity than different concentration of C-HCP/SnO2 composite under same conditions. The results showed that in maximum sensor response with adding the C-HCP in SnO2, the optimum temperature decrease. The optimum temperature for SnO2 and 0.05, 0.1, and 0.15 %wt. of C-HCP in SnO2 composites was obtained 300 °C, 250 °C, 200 °C, and 150 °C, respectively. According to the results, the maximum sensor response observed 0.10 %wt. for ammonia detection at 200 °C. The 0.10 %wt. C-HCP in SnO2 based sensor showed a response three times higher than that by pure SnO2 in ammonia detection. Finally, the repeatability of sensors to the ammonia was obtained suitable in 3 continuous cycle and the response and reduction times of sensors was measured.

Indium Oxide–Graphene Composites Prepared by the Sol–Gel Process and Single-Electrode Gas Sensors on Their Base

Indium oxide–graphene composites (containing 0–6.0 wt % graphene) were manufactured by the sol–gel process. The phase composition, microstructure, and gas-sensitive properties of the prepared materials were studied. The composites consist of isolated In2O3 and graphene phases, where graphene is predominantly adsorbed on the surfaces of indium oxide grains (the indium oxide grain sizes are 8–11 nm). The nanocomposites are distinguished by an enhanced sensitivity to both reducing gases (CH4, acetone) and oxidative gases (NO2). A far greater enhancement is in the sensory response to oxidative gases. Presumably, the major factors influencing the sensory properties of the composite are the high defectiveness of In2O3 and graphene phases, higher specific surface areas of composites compared to those of individual In2O3, and the likely formation of p–n junctions in the indium oxide and graphene contact zone. Graphene additives to indium oxide can improve the main performances (sensory response, response time, and recovery time) of single-electrode semiconductor sensors.

Soft, flexible conductivity sensors for ocean salinity monitoring.

Flexible electrochemical sensors that measure the concentrations of specific analytes (e.g., ions, molecules, and microorganisms) provide valuable information for medical diagnosis, personal health care, and environmental monitoring. However, the conductive electrodes of such sensors need to be exposed to the surrounding environments like chloride-containing aqueous solutions during their operation, where chloride ions (Cl-) can potentially cause corrosion and dissolution of the sensors, negatively impacting their performance and durability. In this work, we develop soft, flexible conductivity sensors made of gold (Au) electrodes and systematically study their electrochemical behaviors in sodium chloride (NaCl) solutions to prevent chloride-induced corrosion and enhance their sensitivity for marine environmental monitoring. The causes of gold chlorination reactions and polarization effects are identified and effectively prevented by analyzing the effects of direct current (DC) and alternating current (AC) voltages, AC frequencies, and exposed sensing areas of the conductivity (salinity) sensors. Accordingly, a performance diagram is constructed to provide guidance for the selection of operation parameters for the salinity sensor. We also convert the varying impedance values of salinity sensors at different salinity levels into output voltage signals using a voltage divider circuit with an AC voltage (0.6 V) source. The results offer an assessment of the accuracy and response time of the salinity sensors, as well as their potential for integration with data transmission components for real-time ocean monitoring. This study has important implications for the development of soft, flexible, Au-based electrochemical sensors that can operate efficiently in diverse biological fluids and marine environments.

High-performance metal-oxide gas sensors based on hierarchical core-shell ZnFe2O4 microspheres for detecting 2-chloroethyl ethyl sulfide.

Mustard gas, an erosive chemical agent, is primarily used as a chemical weapon, which seriously threatens human life and health. Therefore, detecting mustard gas and its simulant, 2-chloroethyl ethyl sulfide (2-CEES), is a very important task. As a binary metal oxide with a spinel structure, ZnFe2O4 is widely used for fabricating gas sensors because of its stable chemical structure and abundant oxygen vacancies. In this study, gas-sensing ZnFe2O4 microspheres with a hierarchical core-shell nanosheet structure were prepared via a simple one-step solvothermal method. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and N2 adsorption analyses were performed to characterize the morphology, structure, and chemical composition of these microspheres. A gas sensor was fabricated from the as-synthesized material, and its gas sensing performance was evaluated, using 2-CEES as a target gas. The obtained ZnFe2O4-based sensor exhibited a high sensitivity of 9.07 to 1 ppm 2-CEES at the optimal working temperature of 250 °C. The sensor response and recovery times were 18 and 546 s, respectively, and its detection sensitivity of 2.87 achieved at a 2-CEES concentration of 0.01 ppm was within an acceptable range. Additionally, the sensor demonstrated sufficiently high 2-CEES selectivity, repeatability, and long-term stability.

Влияние состояния рабочей поверхности гальванического датчика импульсного рентгеновского излучения на его быстродействие

A new design of a galvanic sensor of pulsed X-ray radiation is proposed, which is a flat electric capacitor with a window in one metal lining and a solid dielectric made of the single crystal sapphire with a thickness of 200-300 µm inside. The influence of the surface roughness of the sapphire in the window area on the galvanic linear sensor of X-ray radiation has been established. Tests have shown that with ultra-smooth polishing of the sapphire plate working surface in the window area to a roughness of Rq≤ 0.2 nm, it is possible to provide the galvanic linear detection of X-rays with an energy in the range of 0.1-1 keV and a power density of 1-2 MW•cm-2 with a sensor response time of about 8 ns. Sensors of this type can be used in studies of inertial nuclear fusion processes

Influence of the working surface roughness of the pulsed X-ray radiation galvanic sensor on its performance

A new design of a galvanic sensor of pulsed X-ray radiation is proposed, which is a flat electric capacitor with a window in one metal lining and a solid dielectric made of a single-crystal sapphire with a thickness of 200-300 μm inside. The influence of the surface roughness of the sapphire in the window area on the galvanic linear sensor of X-ray radiation has been established. Tests have shown that, with ultra-smooth polishing of the sapphire plate working surface in the window area to a roughness of Rq≤ 0.2 nm, it is possible to provide the galvanic linear detection of X-rays with an energy in the range of 0.1-1 keV and power density of 1-2 MW· cm-2 with a sensor response time of about 8 ns. Sensors of this type can be used in studies of inertial nuclear fusion processes. Keywords: X-ray radiation, galvanic sensor, sapphire, dielectric, flat capacitor.

Timing matters: the overlooked issue of response time mismatch in pH-dependent analyte sensing using multiple sensors.

Accurate measurement of pH-dependent analytes is crucial for a wide range of applications, including environmental monitoring, industrial processes, and healthcare diagnostics. In multi-sensor systems, combining data from multiple sensors offers the potential for more comprehensive analysis, yet it is important to be aware of the limitations of this approach. In this paper, we investigate the often-overlooked issue of response time mismatch among sensors, which can introduce significant errors in calculated sum parameters. We present a model and software application (SensinSilico) that allows predicting the error arising from a mismatch of sensor response times. The model was compared and validated using experimental results from calculations of total dissolved sulphide (TDS). These calculations were based on data from concurrent sensor measurements of hydrogen sulfide (H2S) and pH, which had different response times. We believe that SensinSilico has the potential to be a powerful tool for researchers, professionals, and end-users, enabling them to estimate and minimize errors arising from response time mismatches, enhancing the accuracy and reliability of their results.

WS2 Gas Sensor Based on Photothermocatalytic Effect for Ammonia Detection With High Response

In this article, four different light sources are utilized to enhance the WS2-based gas sensors properties, and the improvement effects of different light sources on the sensitive characteristics of the sensors are systematically analyzed. First, the WS2 nanomaterials are synthesized by hydrothermal method. In addition, the nanostructures and morphologies are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Finally, the effect of different temperatures and different ammonia concentrations on the sensor response is examined, including darkness, various light illumination (365, 532, 650, and 980 nm). Under dark conditions, the sensor response time is 46 s and recovery time is 55 s in 100-ppm ammonia gas, while the sensor has excellent selectivity for ammonia with a response of up to 81.84 times and only weak response for other gases. The results reveal that the four types of light are capable of reducing the operating temperature where the response value reach the peak. Meanwhile, the maximum response value is effectively increased, from a maximum value of 27 in the dark to a maximum value of 57 under light illumination. The 650-nm light illumination and the 980-nm light illumination exhibit the best effect on improving the response value. Therefore the 180 °C measured by the sensor response curve under 650-nm light conditions is defined as the optimal temperature. At the same time, light illumination can degrade the detection limit of the sensor. Under dark conditions, the ammonia detection limit of the sensor is 100 ppm, while under light illumination conditions, the ammonia detection limit of the sensor is 20 ppm.

Recent advances in ZnO nanostructure as a gas-sensing element for an acetone sensor: a short review.

Air pollution is a severe concern globally as it disturbs the health conditions of living beings and the environment because of the discharge of acetone molecules. Metal oxide semiconductor (MOS) nanomaterials are crucial for developing efficient sensors because of their outstanding chemical and physical properties, empowering the inclusive developments in gas sensor productivity. This review presents the ZnO nanostructure state of the art and notable growth, and their structural, morphological, electronic, optical, and acetone-sensing properties. The key parameters, such as response, gas detection limit, sensitivity, reproducibility, response and recovery time, selectivity, and stability of the acetone sensor, have been discussed. Furthermore, gas-sensing mechanism models based on MOS for acetone sensing are reported and discussed. Finally, future possibilities and challenges for MOS (ZnO)-based gas sensors for acetone detection have also been explored.

Efficient electrochemical detection of L-lactic acid using platinum nanoparticle decorated Chitosan/ZnTiO3 nanocomposites

Herein, a facile L-lactic acid electrochemical sensor based on Pt-nanoparticles (NPs)@Chitosan/ZnTiO3 nanocomposites (NCs) coated on a glassy carbon electrode (GCE) is demonstrated. Ultra-sonication method followed by irradiation using an Osram Hg-lamp was applied to prepare Pt-NPs@Chitosan/ZnTiO3 NCs, and the characterization of prepared NCs was executed by Field Emission Scanning Electron Microscopy FESEM, Energy Dispersive Spectroscopy EDS, Transmission Electron Microscopy TEM, High Resolution Transmission Electron Microscopy HRTEM, Fourier Transform Infrared Spectroscopy FTIR, Ultraviolet–visible spectroscopy UV–vis., and X ray Diffraction XRD analysis. A linear current versus potential responses relation was obtained in a concentration range of L-lactic acid of 0.30 ∼ 2.40 mM at differential pulse voltammetric (DPV) analysis in a pH 7.0 buffer medium and resulted concentration range was defined as the dynamic detection range (LDR) for L-lactic acid analysis. The L-lactic acid sensor sensitivity (0.4529 µAµM-1cm−2), limit of detection (LOD; 22.36 ± 1.12 µM), and limit of quantification (LOQ; 79.88 µM) were obtained. Besides this, the sensor reproducibility and response time were found to be reliable. Finally, the assembled sensor probe was validated by the testing of real samples, which exhibited acceptable and satisfied results. It is introduced a new route for the detection of chemicals using novel nanocomposite materials by electrochemical approach for the safety of healthcare fields in a broad scales.

Highly sensitive graphene-based ammonia sensor enhanced by electrophoretic deposition of MXene

Herein, we reported a gas sensor based on MXene/Graphene composite sensitive film for low-concentration ammonia detection. Specifically, we use the electrophoretic deposition method to uniformly deposit MXene on the graphene film surface of the graphene sensor, thereby constructing the MXene/Graphene composite sensitive film. The ammonia sensitivity test results show that the MXene/Graphene composite film sensor exhibits fast response, high sensitivity and excellent selectivity to ammonia at room temperature and high humidity. At the same test concentration (100 ppm), the sensitivity of the MXene/Graphene sensor is 3 times higher than that of the graphene sensor, 2 times higher than that of the MXene film sensor, reaching 25%, and its theoretical limit of detection is 56 ppb. The response time is only 26 s and the recovery time is 148 s, while the response time of the graphene sensor is 228 s. The MXene/Graphene sensitive film takes full advantage of the hydrophilicity and abundant surface functional groups of MXene, and the excellent electrical conductivity of graphene, which solves the problems of low sensitivity, slow response speed, and inability to completely desorb ammonia gas of pure MXene or graphene. Potential applications in designing next-generation portable gas sensors for human breath detection analysis.

Enhanced cataluminescence sensing of MIL-53(Al)/Sb2SnO5 composites for isobutanol detection

In this study, MIL-53(Al) and Sb2SnO5 were synthesized by hydrothermal and precipitation methods, respectively. The doped MIL-53(Al)/Sb2SnO5 showed excellent catalytic properties, specifically for selectivity and sensitivity for isobutanol (IBN). To assess the catalytic properties of MIL-53(Al)/Sb2SnO5, an IBN gas sensor based on cataluminescence of MIL-53(Al)/Sb2SnO5 was developed, and it demonstrated detection of IBN with high sensitivity, high specificity, fast detection, and good stability. The signal response and recovery time of IBN gas sensor were 0.5 s and 6 s, respectively, and a good linear relation was 0.050–2.5 μg ml−1 (R 2 = 0.9956) with a low detection limit of 0.015 μg ml−1. Further, the IBN sensor applied in the detection of real samples had satisfactory recoveries (90.0%–108%) with relative standard deviations of 3.2%–6.7%. The developed sensor based on MIL-53(Al)/Sb2SnO5 has great prospects for the practical detection of IBN gas in the fields of environmental analysis, safety monitoring, etc.

Design and Fabrication of a Thermopile-Based Thin Film Heat Flux Sensor, Using a Lead—Substrate Integration Method

An accurate and continuous measurement of heat flux is needed in many long-term operation facilities in order to monitor and improve the life of its machinery. A thin film heat flux sensor is usually fabricated via sputtering, according to different spatial arrangements of thermocouple junctions. A novel thin film heat flux sensor was designed, fabricated, and calibrated, but the connection between the thin film and the leads could not be fixed quickly and steadily. For this purpose, in this paper a method to seamlessly integrate the leads and the thin film has been proposed to improve the sensor output signal. The sensor is capable of simultaneously measuring surface heat flux and temperature magnitude, to address the current situation of the single design of heat flux sensors. The novel thin film heat flux sensor is structured as follows: Thirty pairs of NiCr-NiSi thermocouple junctions are deposited in an annular pattern on a well-designed ceramic substrate. Over the annular thermopile, a 2000 nm-thick thermal insulator layer is deposited to create a temperature gradient across the layers. In addition, in this study a new calibration method was used to evaluate the static and dynamic properties of this novel thin film heat flux sensor. The analysis and experimental results show that the heat flux calculated from the sensor output was in good agreement with the value obtained from the pre-calibrated standard sensor. The sensitivity and response time of the novel sensor were measured at 0.06 mV/(kW/m2) and 475 ms, respectively. The heat flux measurements made with the sensor presented good repeatability. The heat-transfer coefficient of the Al2O3 thin film was 4.477 w/(m∙k) for the novel thin film heat flux sensor described in this paper.

Incorporation of a Multi-Valent Aptamer into Electrochemical Biosensors to Achieve an Improved Performance for Thrombin Analysis in Blood Serum.

The electrochemical aptamer-based (E-AB) biosensor usually has a long reaction time when detecting thrombin. This work reports the design of an E-AB biosensor with dual recognition sites to quickly detect thrombin. Specifically, two specific recognition sites of thrombin were used to design three aptamer sequences (TBA-15, TBA-29 and TBA-U), followed by fabrication of corresponding sensors. First, we tested these three types of biosensors in tris buffer solution, and found that the response time of the TBA-U sensor to the same concentration of thrombin was about 2 hours, which is shorter than TBA-15 and TBA-29 sensors. Then, we also did the same test in 50 % diluted serum with 500 nM thrombin. The response time of the TBA-U sensor was about 2 hours, which is still faster than the 3 hours of TBA-15 sensor and the 5.5 hours for TBA-29 sensor. In addition, in terms of dynamic range and specificity, TBA-U has good performance.

A highly efficient room-temperature formaldehyde gas sensor based on a Ni-doped ZnO hierarchical porous structure decorated with NiS illuminated by UV light

Developing room-temperature formaldehyde gas sensors with superior response-ability is crucial for many applications including the detection of indoor air pollutants. Herein, we synthesized a series of Ni-doped ZnO (Ni-ZnO) hierarchical porous structures decorated with NiS (NiS/Ni-ZnO) composite materials by the simple hydrothermal method, and the room-temperature (25 ± 1 ℃) UV light-activated photoelectronic formaldehyde sensors based on the ZnO, Ni-ZnO and NiS/Ni-ZnO composites were presented and compared. The response value of 0.2% NiS/0.4% Ni-ZnO material reached 330% toward 10 ppm formaldehyde gas, which was nearly 2.5 times higher than that of pure ZnO, and the faster response/recovery time (39.4 s/40.7 s) was obtained using UV light at room temperature. XPS, SPV, TPV spectrum analysis, and density functional theory (DFT) calculation showed that 0.2% NiS/0.4% Ni-ZnO sensor's excellent sensing performance was due to the synergistic effect of Ni doping and NiS modification which improved the separation efficiency and accelerated the migration of charge carriers. Here, the relationship between the response time of photoelectric gas sensors and the behavior of photogenerated carriers is firstly discussed in detail, which provides new insight into the development of room-temperature photoelectric gas sensors with superior response-ability. • NiS/Ni-ZnO hierarchical porous structure has been fabricated using hydrothermal method. • NiS/Ni-ZnO sensor exhibits fast response and high responsivity to formaldehyde at room temperature. • Excellent gas sensing performance of NiS/Ni-ZnO sensor is explained from the dynamic behavior of photogenerated carriers. • The relationship between the response time of gas sensor and the behavior of carriers is firstly discussed in detail.

Easy regulation of chitosan-based hydrogel microstructure with citric acid as an efficient buffer

Being an important soft material, the chitosan-based hydrogel exhibits colorful features and widespread applications stemmed mainly from its intrinsic microstructure. In particular, the design of hydrogels with oriented channel structures is of significance importance. In this paper, polyvinyl alcohol (PVA)/chitosan (CS)/MXene-CA hydrogels with directional channel structure were obtained by simple freezing and thawing method with citric acid (CA) as a buffer. The introduction of CS increased the tensile strength of PVA hydrogel from 5.38 kPa to 29.22 kPa. The uniform distribution of MXene was efficiently enhanced within the constructed channel microstructure, and conductivity was increased to 1.91 S/m. The response time of the flexible sensor based on the hydrogel was 200 ms. It can sensitively detect large-scale deformation (blending of joints), small-scale activity (frowning), and electrocardiogram. Therefore, the paper provided an efficient way to regulate the microstructure in hydrogel network and enhance the uniform dispersion of functional nanomaterials.