Response Recovery Time Research Articles

A novel peony shaped ZnO and its excellent ethanol gas-sensing performance

In order to improve the gas-sensing performance of ZnO, a novel peony shaped ZnO stacked with nanosheets were prepared using hydrothermal method, and the obtained ZnO was characterized and tested for gas sensitivity. The results showed that the particle distribution of the peony shaped ZnO was uniform, with a particle size of about 0.8μm. The gas-sensing response test results show that the peony shaped ZnO has excellent selectivity to ethanol gas. When the concentration of ethanol gas is 100ppm, the gas-sensing response of the peony shaped ZnO to ethanol gas reaches 17.4, and the response time and recovery time are 8 seconds and 12 seconds, respectively. Even at an ethanol gas concentration of 2ppm, the gas-sensing response of the peony shaped ZnO to ethanol gas can reach 2.1. Compared to existing literature reports, the peony shaped ZnO prepared in this paper has better gas-sensing performance. This study will provide data support and theoretical reference for the development of high-performance gas sensors.

Miniaturized Electrochemical Gas Sensor with a Functional Nanocomposite and Thin Ionic Liquid Interface for Highly Sensitive and Rapid Detection of Hydrogen.

Hydrogen has been widely used in industrial and commercial applications as a carbon-free, efficient energy source. Due to the high flammability and explosion risk of hydrogen-air mixtures, it is vital to develop sensors featuring fast-responding and high sensitivity for hydrogen leakage detection. This paper presents a miniaturized electrochemical gas sensor by elaborately establishing a nanocomposite and thin ionic liquid interface for highly sensitive and rapid electrochemical detection of hydrogen, in which a remarkable response time and recovery time of approximately 6 s was achieved at room temperature. A screen-printed carbon electrode was modified with a reduced graphene oxide-carbon nanotube (rGO-CNT) hybrid and platinum-palladium (Pt-Pd) bimetallic nanoparticles to realize high sensitivity. To achieve miniaturization and high stability of the sensor, a thin-film room-temperature ionic liquid (RTIL) was employed as the electrolyte with a significantly decreased response time. The fast-responding hydrogen sensor demonstrates excellent performance with high sensitivity, linearity, and repeatability at concentrations below the lower explosive limit of 4 vol %. The engineered high-performance interface and gas sensor provide a promising and effective strategy for gas sensor design and rapid hazardous gas monitoring.

Microstructured Self-Healing Flexible Tactile Sensors Inspired by Bamboo Leaves.

Wearable electronic devices with multifunctions such as flexible, integrated, and self-powered play a crucial role in the fields of health monitoring, motion monitoring, and human-computer interaction. However, their core basic components, flexible pressure sensors, face challenges including poor long-term stability and insufficient real-time sensing accuracy. In order to solve the challenges of long-term, stable, and accurate sensing of the sensor, this paper prepares polydimethylsiloxane (SHPDMS) with intrinsic self-healing property and designs a high-sensitivity self-healing capacitive flexible pressure sensor with dual microstructures (grating microstructured electrodes and microporous dielectric layer) as the substrate based on SHPDMS. Specifically speaking, the self-healing of the sensor under mild conditions was realized by introducing reversible imine bonds with low bonding energy into the polydimethylsiloxane (PDMS) flexible substrate, which solved the problem of the material's long-term service durability. A grating-like microstructure was introduced into the flexible electrode by using a spotted bamboo taro leaf as a template, and a dual microstructure sensor was constructed by combining it with a microporous dielectric layer doped with single-walled carbon nanotubes. This way reduces the elastic modulus of the dielectric layer, improves the dielectric constant of the sensor under loading, and thus significantly improves the sensor's sensitivity and extends the measurement accuracy in a low-stress range. The prepared self-healing flexible sensor achieves a sensitivity of 3.6 kPa-1, a minimum detection limit of 5 Pa, a response recovery time of less than 80 ms, and stability over 5000 cycles, which exceeds most previously reported silicone rubber-based capacitive flexible sensors.

Mode-locked soliton pulse generation using copper phthalocyanine absorber in long erbium-doped fibre laser cavity

We present the development of a mode-locked erbium-doped fibre laser (EDFL) utilizing Copper Phthalocyanine (CuPc) as a saturable absorber (SA). CuPc exhibits unique optical properties, including its high nonlinear optical response and rapid recovery time. To seamlessly integrate CuPc into the laser cavity, we employed a simple embedding technique within a polymer film. The SA demonstrates a modulation depth of 3.1% and a saturation intensity of 17 MW/cm2. Operating within a pump power range of 90.6 to 122.9 mW, the laser achieves mode-locked operation, producing a soliton pulse train with a fundamental frequency of 1.82 MHz and a pulse width of 6.4 ps at a wavelength of 1561.5 nm. It attains a maximum output power of 13.97 mW and a pulse energy of 7.67 nJ. These results underscore CuPc's potential as a promising material for generating mode-locked pulses, suggesting new avenues in ultrafast laser development for diverse applications.

Ultra-compact dual-channel integrated CO2 infrared gas sensor

Expiratory CO2 concentrations can directly reflect human physiological conditions, and their detection is highly important in the treatment and rehabilitation of critically ill patients. Existing respiratory gas analyzers suffer from large sizes and high power consumption due to the limitations of the internal CO2 sensors, which prevent them from being wearable to track active people. The internal and external interference and sensitivity limitations must be overcome to realize wearable respiratory monitoring applications for CO2 sensors. In this work, an ultra-compact CO2 sensor was developed by integrating a microelectromechanical system emitter and thermopile detectors with an optical gas chamber; the power consumption of the light source and ambient temperature of the thermally sensitive devices were reduced by heat transfer control; the time to reach stabilization of the sensor was shortened; the humidity resistance of the sensor was improved by a dual-channel design; the light loss of the sensor was compensated by improving the optical coupling efficiency, which was combined with the amplitude trimming network to equivalently improve the sensitivity of the sensor. The minimum size of the developed sensor was 12 mm × 6 mm × 4 mm, and the reading error was <4% of the reading from −20 °C to 50 °C. The minimum power consumption of the sensor was ~33 mW, and the response time and recovery time were 10 s (@1 Hz), and the sensor had good humidity resistance, stability, and repeatability. These results indicate that the CO2 sensor developed using this strategy has great potential for wearable respiratory monitoring applications.

Preparation of aerogels with SBS@rGO structure by Pickering emulsion method for innovative applications in pressure sensors

Pressure sensors based on graphene conductive fillers show great promise for application in the field of smart wearable devices. The SBS@rGO structured aerogel sensors covered herein were prepared by the Pickering emulsion method based on a solution of styrene-butadiene-styrene (SBS) and reduced graphene oxide (rGO) dispersion. The mechanical properties of SBS@rGO aerogel were tested with 100 independent loading-unloading cycles in a graded compressive strain range of 10–40 %. The results indicate that the SBS@rGO aerogel have fast and slightly destructive resilience after unloading at low compressive strains (ε ≤ 30 %). Moreover, the presence of rGO endowed SBS@rGO with pressure sensing properties such as high electrical conductivity (2.294 S/m), high sensitivity (0.016 kPa−1 at 6.36–100 kPa), short signal response time (60 ms) and recovery time (30 ms). The SBS@rGO pressure sensors were integrated into shoe soles to simulate walking scenes, whose response signals had excellent reproducibility and could be differentiated according to three different walking states. The potential and feasibility of SBS@rGO aerogel as wearable flexible pressure sensors has been demonstrated.

High Sensitivity Bi2O3/Ti3C2Tx Ammonia Sensor Based on Improved Synthetic MXene Method at Room Temperature.

The MXene Ti3C2Tx was synthesized using hydrofluoric acid and an improved multilayer method in this study. Subsequently, a Bi2O3/Ti3C2Tx composite material was produced through hydrothermal synthesis. This composite boasts a unique layered structure, offering a large surface area that provides numerous contact and reaction sites, facilitating the adsorption of ammonia on its surface. The prepared Bi2O3/Ti3C2Tx-based sensor exhibits excellent sensing performance for ammonia gas, including high responsiveness, good repeatability, and rapid response-recovery time. The sensor's response to 100 ppm ammonia gas is 61%, which is 11.3 times and 1.6 times the response values of the Ti3C2Tx gas sensor and Bi2O3 gas sensor, with response/recovery times of 61 s/164 s at room temperature, respectively. Additionally, the gas sensitivity mechanism of the Bi2O3/Ti3C2Tx-based sensor was analyzed, and the gas sensing response mechanism was proposed. This study shows that the sensor can effectively enhance the accuracy and precision of ammonia detection at room temperature and has a wide range of application scenarios.

Ag modified ZnO nanoflower gas sensitive sensor for selective detection of n-butanol

Ag modified ZnO nanoflowers were successfully prepared by sunlight induced solvent reduction method. The samples were characterized by x-ray diffractometer, field emission scanning electron microscope, transmission electron microscope and energy dispersive x-ray spectrum, and the results confirmed the presence of Ag nanoparticles on the ZnO nanoflower. The gas sensing performance of the materials was studied at different operating temperatures and different n-butanol concentrations. The results showed that the Ag modified ZnO nanoflower sensor responded to 50 ppm n-butanol up to 147.17 at 280 °C, and the Ag modified ZnO nanoflower sensor exhibited excellent repeatability, stability and response recovery time. In addition, different target gases were employed for the selectivity study of the Ag modified ZnO nanoflower. It can be found that the Ag modified ZnO nanoflower had good selectivity for n-butanol. The improved response of the Ag modified ZnO nanoflower sensor was attributed to the catalytic effect of Ag nanoparticles. The results indicate that the Ag modified ZnO nanoflower will become a very promising sensing material for n-butanol gas detection.

Coral-like Co-doped ZnO nanostructures for enhanced triethylamine detection

In this work, coral-like Co-doped ZnO nanostructures were obtained using simple precipitation and hydrothermal methods. Co-doping reduced the composite particle size to 20 nm, and the controlled growth direction formed a larger adsorption area. The gas sensor results suggest that the maximum response to triethylamine at 200 °C was achieved at 5 mol% doping content. The sensor also performed well for the 30-day stability test, displaying excellent selectivity and repeatability. Besides, 5CZO showed a response-recovery time of 52/70 s and a good response to different gas concentrations. The doping mechanism for the improved gas sensing performance with triethylamine was thoroughly investigated.

Multiple-Yolk-Shell NiO Microspheres for Selective Detection of m-Xylene.

m-Xylene is a volatile organic compound that is extensively used in various industrial processes. It is toxic, posing significant risks to human health and the environment. Therefore, developing gas sensors with high sensitivity and selectivity for m-xylene detection is critical. In this work, we demonstrated the synthesis of NiO-yolk double-shell (NiO-YDS) and NiO-yolk triple-shell (NiO-YTS) derived from NiO/Ni-BTC and NiO/Ni-PTA composites, respectively, using the microwave-assisted solvothermal method from Ni-BTC-derived NiO spheres. The NiO/Ni-BTC composite has trimesic acid (H3BTC) as an organic linker, while NiO/Ni-PTA has p-terephthalic acid (PTA). We investigated the sensing properties of these materials for 2-butanone, 2-nonanone, 3-methyl-1-butanol, acetone, benzene, ethanol, methanol, and m-xylene. These composites exhibited excellent sensitivity and selectivity for detecting m-xylene under dry conditions. Specifically, the NiO-YTS sensor showed a sensitivity of 217.5% to m-xylene, while the NiO-YDS sensor demonstrated a sensitivity of 179.8% at 350 °C in dry air. We emphasize the NiO-YTS composite due to its superior sensitivity and selectivity in detecting m-xylene compared with the NiO-YDS composite. The NiO-YTS sensor exhibited stable and reproducible sensing performance for 100 ppm of m-xylene under optimum working conditions, with a theoretical detection limit of 5.43 ppb and relatively fast response time (89 s) and recovery time (191 s). This work describes an easy method for synthesizing NiO-YDS and NiO-YTS derived from NiO/Ni-BTC and NiO/Ni-PTA composites. It demonstrates that these composites represent a new class of materials that can potentially enhance the sensitivity and selectivity of m-xylene gas sensors.

High-sensitivity humidity sensor based on Mach-Zehnder interferometer in seven-core fiber

A Mach-Zehnder Interferometer (MZI) based on seven-core fiber (SCF) for humidity sensing is proposed and experimentally demonstrated. The MZI is formed by sandwiched a section of SCF in between two single mode fibers (SMFs), while a fiber taper and a brief multimode fiber (MMF) act as fiber couplers to excite and couple the intermodal interference in the SCF. The optical field distribution and coupling efficiency of the MZI with different SCF lengths are analysed. The theoretical results show that the MZI is sensitive to SCF lengths, and it is expected to obtain highly sensitive humidity response. Humidity sensing experiments shows a high sensitivity of 0.6603 nm/%RH over a relative humidity (RH) range of 44–83 %RH, and the maximum measurement uncertainty introduced by the long-term stability is 0.0006 %RH. Human respiration measurement exhibits the response time and recovery time of the MZI are 0.44 s and 1.24 s respectively. The temperature effect is also experimentally investigated. Such an all-fiber MZI presents advantages of simple configuration, high sensitivity and good stability, making it has potential in humidity measurement fields.

Enhanced ethanol gas sensing performance of Ag/SnO2 composites

A simple hydrothermal method was adopted to synthesize rectangular block-shaped SnO2 nanomaterials loaded with different amounts of Ag. The structural composition, morphology and chemical state of the nanomaterials were systematically investigated using XRD, SEM, TEM and XPS analysis. The gas sensing performance to ethanol was comprehensively evaluated by testing key parameters including gas response, optimal operating temperature, response-recovery time, and selectivity. The result demonstrates that the Ag/SnO2 composite, compared to pure SnO2, exhibits enhanced efficiency in detecting ethanol. The gas sensor fabricated by the sample Ag/SnO2-2 had a response of up to 80 for 200 ppm ethanol at 300℃. Moreover, the response time (reduced from 52 s to 29 s) and the selectivity were significantly improved. The superior gas sensing performance of Ag/SnO2 is attributed to the generation of highly active sites from Ag ion loading, accelerated electron transfer processes, and modulation of Schottky heterojunctions. In summary, this work demonstrates an effective strategy to improve the gas sensing performance of SnO2-based sensors by Ag loading.

γ- WO3 decorated MXene: An advanced nanomaterial for room temperature operable enhanced ammonia sensor

The proliferation of Internet of Things (IoT) applications necessitates the deployment of high-performance ammonia (NH3) sensors. In recent studies, Ti3C2Tx, a novel two-dimensional (2D) material, has been extensively investigated for its potential as a room temperature NH3 sensor. However, pristine MXene-based sensors have exhibited deficiencies in long-term stability and reproducibility. In response, an MXene/γ-WO3 composite has been synthesized using an ultra-sonication method to address these challenges. The resulting composite sensor has demonstrated remarkable performance, attributable to, increased active sites from defects induced by WO3, and the presence of a p-n heterojunction. Notably, electron transfer from WO3 to Ti3C2Tx has been identified as a critical contributing factor to the enhanced characteristics of these nanohybrids, as evidenced by observed alterations in binding energies for the Ti 2p and W 4f core levels. These findings have expanded our understanding of the electrical interactions in Ti3C2/WO3 and their potential applications in diverse domains. The pristine MXene sensor exhibited a response of 59.39% at 300 ppm at room temperature, while the composite MXene/γ-WO3 displayed a response of 92.3%. Additionally, the response recovery time was recorded at 22seconds and 9seconds, respectively. The chemiresistive ammonia sensor's performance was evaluated across a range of concentrations (25–300 ppm) and relative humidity levels (11–94% RH). The composite sensor has demonstrated reproducibility and long-term stability, coupled with high sensitivity to NH3. This manuscript aims to highlight the enhanced ammonia sensing properties and selectivity of MXene/γ-WO3 composite materials.

Respiratory rate monitoring based on all-fiber strain-induced humidity sensor

In this paper, an agarose coated-fiber Bragg grating (AG-FBG) based respiratory rate (RR) sensor for evaluating respiratory function and health status by all-fiber strain-induced humidity-sensitive material is proposed and experimentally demonstrated. The variation of the environment humidity leads to changes in the film morphology of AG, i.e., expansion and contraction, which impose strains on FBG to dynamically shift the central wavelength. In the experiment, the average sensitivity of the proposed AG-FBG-based RR sensor is 23.6 pm/%RH in the range of 30 %RH–90 %RH. Under the monitoring of a commercial FBG demodulator with a wavelength resolution of 1 pm, rich human breathing information is collected. The RR monitoring under different human postures and breathing patterns are respectively measured. In one breathing cycle, the response time and recovery time are 778 ms and 762 ms, respectively. The proposed sensor is simple and low-cost, shows easy signal demodulation, stable signal wavelength variation, and high repeatability, which has potential applications in vital signs monitoring and medical treatment.

Synthesis, analysis and characterization of surfactant-assisted TiO2 nanoparticles for ammonia gas sensor applications

In our study, we focused on gas sensing, particularly ammonia detection. We synthesized and examined three types of nanoparticles: pure and conducting polymer-based TiO2 nanoparticles. The nanoparticles were prepared by an easy sol-gel approach. All of the samples were characterized using XRD, FTIR, UV-vis, FESEM, EDAX and BET. Gas sensing measurements were carried out for each sample. Among them, PEG-TiO2 stood out with remarkable gas sensing abilities, distinguishing it from other gas detection technologies. We thoroughly investigated the sensor performance, focusing close scrutiny to metrics such as response and recovery times. The greatest reduction in response time and recovery time (95 s / 123 s) was achieved at 25 ppm. These metrics provide insights into how quickly the sensor detects and recovers from the presence of the target gas. Our findings offer important insights for optimizing the sensor performance of PEG-TiO2, highlighting its remarkable gas sensing capabilities.

UV-enhanced O2 sensing using β-Ga2O3 nanowires at room temperature

Oxygen sensors based on β-Ga2O3 nanowires were prepared by a chemical vapor deposition method and investigated in detail. β-Ga2O3 nanowires grew on sapphire substrate at 1100 °C with Au as a catalyst. The polycrystalline structure was confirmed according to the X-ray diffraction (XRD) patterns. Scanning electron microscope (SEM) images revealed the average diameter of the nanowires was 150 nm. The ratio of Ga to O was 0.765 according to energy dispersive spectroscopy (EDS) results. Photoluminescence emissions at 445 and 484 nm originated from oxygen vacancies and gallium-oxygen vacancy pairs. Both EDS results and photoluminescence revealed intrinsic oxygen vacancies in β-Ga2O3 nanowires. We coated the β-Ga2O3 nanowires on an interdigitated electrode to fabricated an oxygen sensor. Under ultraviolet light irradiation, at room temperature, the sensor’s response rise time and recovery time were 1034 s and 1283 s to 600 ppm oxygen, those were 1290 s and 1709 s to 1200 ppm oxygen. The mechanism of oxygen sensing was discussed.

Perovskite CsPbBr3 quantum dots enhanced In2O3 nanospheres for triethylamine detection at low temperature

In recent years, the vigorous industrial development of the country has brought about serious air pollution, and the development of low-temperature gas sensors with high response and short response/recovery time has become ideal for monitoring the industrial environment. This work demonstrates a composite gas sensor based on CsPbBr3 perovskite quantum dots (QDs) and In2O3 nanospheres for the detection of TEA gases at low temperatures. Compared with pure In2O3, the best responsive gas for the In2O3-CsPbBr3 QDs composite was triethylamine (TEA), with a response value of 52.92 at an optimal operating temperature of 60 °C. In addition, due to the sensitive optical properties of the CsPbBr3 QDs, UV irradiation of the In2O3-CsPbBr3 composites was performed, and the samples were found to have response values as high as 156.42. The In2O3-CsPbBr3 composite also has a short response recovery time (1/19 s), which is favorable for timely warning. The results of the gas-sensing experiments showed that the sensor has good sensitivity, reproducibility, and stability for triethylamine.

A Highly Sensitive, Low Creep Hydrogel Sensor for Plant Growth Monitoring

Ion−conducting hydrogels show significant potential in plant growth monitoring. Nevertheless, traditional ionic hydrogel sensors experience substantial internal creep and inadequate sensitivity, hindering precise plant growth monitoring. In this study, we developed a flexible hydrogel sensor composed of polyvinyl alcohol and acrylamide. The hydrogel sensor exhibits low creep and high sensitivity. Polyvinyl alcohol, acrylamide, and glycerol are crosslinked to create a robust interpenetrating double network structure. The strong interactions, such as van der Waals forces, between the networks minimize hydrogel creep under external stress, reducing the drift ratio by 50% and the drift rate by more than 60%. Additionally, sodium chloride and AgNWs enrich the hydrogel with conductive ions and pathways, enhancing the sensor’s conductivity and demonstrating excellent response time (0.4 s) and recovery time (0.3 s). When used as a sensor for plant growth monitoring, the sensor exhibits sensitivity to small strains and stability for long−term monitoring. This sensor establishes a foundation for developing plant health monitoring systems utilizing renewable biomass materials.

Study of doping effect of cd on ZrO2 nanostructures for gas sensing applications

Abstract Here, we enforced the conventional precipitation approach to yield pure and cadmium doped (3% and 8%) ZrO2 powder, to examine the gas sensing proficiency of Zirconium metal oxide. Drop casting mechanism is hired for the formation of pure and cadmium doped ZrO2 films. The X-ray diffraction (XRD) outcomes recommended that the prepared pure and cadmium doped ZrO2 powder samples are pure with no subordinate phase, but slight shift in peaks were detected. Scanning Electron Microscope (SEM) portrait substantiates the uniform spherical like morphology of the samples. The Current Voltage (I-V) study affirms the good conducting nature of the samples. The photoluminescence (PL) inspection, confirms that the oxygen vacant spots are present in the processed samples. The UV-Diffuse Reflectance Spectra validates the decrement of band gap of the prepared samples with rise in dopant concentration. The gas sensing capabilities of the drop casted samples were examined for different gas concentrations of reducing gases like ammonia, acetone, ethanol, formaldehyde and xylene. From the output data, we interpreted that the prepared samples show favorable response towards the target gas, explicitly the 8% cadmium doped sample shows 39% of an extreme response towards ammonia gas. Likewise, it also accomplishes an expeditious response time (RST) and recovery time (RCT) among all samples. Thus, we resolved that the inclusion of cadmium content stacks up the gas sensing adaptability of the zirconium metal oxide.

Captivating 2H-MoS2 nanoflowers for efficient NH3 detection and photocatalytic dye degradation

This research unveils the gas sensing and photocatalytic potential of 2H-MoS2 nanoflowers, offering a promising solution for ammonia sensing and wastewater remediation. The 2H phase of MoS2 nanoflowers is synthesized via a simple one-step hydrothermal method using ammonium heptamolybdate and thiourea. The elemental and morphological study confirms the formation of the 2H phase of MoS2 nanoflowers with an average sheet thickness of 14 nm. The XRD and HR-TEM analysis findings are in good accordance with the interlayer spacing of MoS2, calculated to be 0.64 nm. The 2H-MoS2 nanomaterial based chemiresistive sensor is tested for six different targets (NH3, C2H5OH, C3H6O, C3H7OH, HCHO, and C6H5CH3) and shows good selectivity towards ammonia (NH3) with the highest response of 81 %. The response-recovery time, repeatability, concentration, and humidity-based analysis are conducted for the analysis of the sensor. The fabricated 2H-MoS2 based sensor shows a response time of 8.5 s and a recovery time of 4.3 s. Furthermore, three model water contaminated dyes, MB, MO, and RB, are chosen for the photocatalytic experiment under visible light irradiation. The reusability, relative degradation, and pseudo-first-order analysis are used to evaluate the photocatalytic dye degradation properties of 2H-MoS2 nanoflowers. The reaction rate constant of 2H-MoS2 nanomaterials for MB, MO, and RB dyes is calculated to be (0.05010) min−1, (0.03458) min−1, and (0.02516) min−1, respectively. The maximum degradation efficiency of 2H-MoS2 nanoflowers towards MB, MO, and RB dye is 95 %, 86 %, and 76 %, respectively, under visible light irradiation. These findings suggest that the hydrothermally synthesized 2H-MoS2 nanoflowers have multifunctional applications such as effective NH3 sensors as well as photocatalysts for organic dye degradation, paving the way for more efficient and sustainable gas sensing and wastewater treatment technologies.