Maximum Sensitivity Of Sensor Research Articles

Gold Nanoparticle Sensitized Zinc Oxide Nanorods-Based Nitric Oxide Gas Sensors with High Sensitivity, Selectivity and Low Detection Limit

Development of a low-cost hand-held nitric oxide (NO) sensor with high selectivity, sensitivity and low detection limit is attractive for environment and health monitoring applications. NO gas sensor was fabricated using hydrothermally grown ZnO nanorods (ZnO NRs). The sensing performance like sensor response, sensitivity, detection limit has been improved significantly by attaching gold nanoparticles (Au NPs) with ZnO NRs. Au NPs were synthesized by chemical reduction method from gold chloride trihydrate. The attachment of Au NPs on nanorods was done by spin coating method. The maximum sensor response and sensitivity were obtained at [Formula: see text]C operating temperature with [Formula: see text]l gold loading. The interference study of the sensor was carried out with acetone, ammonia, carbon monoxide, hydrogen peroxide and propanol. It demonstrated high selectivity towards the interfering gases and high humid condition. Au-decorated ZnO NRs exhibited very low detection limit [Formula: see text][Formula: see text]ppb, which is attractive for biomedical applications.

Increasing sensitivity of the electrostatic field mill sensor by determining its optimal configuration

The object of research is the process of measuring the strength of the electrostatic field for a low dynamic range (from 0 to 1 kV/m). This study is aimed at increasing the sensitivity of the sensor of the electrostatic field mill (EF) by determining its optimal geometric configuration, which will reduce the error of measuring the electrostatic field strength. To establish the actual value of the induced current, a computer model was built and simulation modeling of the EF sensor was carried out. On the basis of the constructed computer model, studies of the EF sensor were carried out to determine the numerical value of the induced current. As a result, it was established that the occurrence of edge effects leads to the appearance of methodological error, which occurs due to the fact that the average induced current is smaller compared to the calculated value. As a result of computer modeling of the EF sensor to determine the value of the optimal number of sectors, it was established that for the proposed design of the EF sensor, the optimal number of sectors is six. It was established that the optimal value of the distance between the sensitive plates and the shielded rotor should be in the range of 2.5–3 mm to ensure the maximum sensitivity of the EF sensor and its safe use. The determined optimal parameters of the EF geometric configuration will allow to form the necessary requirements for the construction of improved electrostatic field strength meters in a low dynamic range (from 0 to 1 kV/m). A promising direction of application of such devices in production will be the development of an additional system for monitoring the strength of the electrostatic field, which will allow to prevent the occurrence of a dangerous situation.

Modulation of the sensing bandwidth of dual-channel SPR sensors by TiO2 film

Facing the diversity and complexity of the types of parameters to be measured, multi-channel surface plasmon resonance (SPR) fiber sensors provide an excellent solution. However, the sensing bandwidth is a key factor affecting the sensor performance. In this paper, we explore a method to modulate the sensing bandwidth using the TiO2 film. A dual-channel SPR sensor with a wide sensing bandwidth is proposed. In this sensor, no-core fiber (NCF) is used as the sensing probe, and multimode fibers are used for the transmission of optical signals. The sensor has a cascaded composite film structure, the region coated with Ag film as the refractive index sensing region and the region coated with Ag/TiO2/PDMS as the temperature sensing region. The experimental results show that the sensing bandwidth of the sensor varies for different TiO2 coating times. It indicates that the TiO2 film can regulate the sensing bandwidth flexibly. Therefore, to achieve the optimal sensing effect, the TiO2 coating time can be flexibly adjusted according to the RI characteristics of the environment. The maximum sensitivity of this dual-channel sensor is 4.5 nm/°C and 3151 nm/RU when the temperature range is between 10 and 80 °C and the RI range is between 1.333 and 1.385, respectively. In addition, we discuss the repeatability and stability of this dual-channel sensor.

Design of Surface Plasmon Resonance-Based D-Type Double Open-Loop Channels PCF for Temperature Sensing.

Here, we document a D-type double open-loop channel floor plasmon resonance (SPR) photonic crystal fiber (PCF) for temperature sensing. The grooves are designed on the polished surfaces of the pinnacle and backside of the PCF and covered with a gold (Au) film, and stomata are distributed around the PCF core in a progressive, periodic arrangement. Two air holes between the Au membrane and the PCF core are designed to shape a leakage window, which no longer solely averts the outward diffusion of Y-polarized (Y-POL) core mode energy, but also sets off its coupling with the Au movie from the leakage window. This SPR-PCF sensor uses the temperature-sensitive property of Polydimethylsiloxane (PDMS) to reap the motive of temperature sensing. Our lookup effects point out that these SPR-PCF sensors have a temperature sensitivity of up to 3757 pm/°C when the temperature varies from 5 °C to 45 °C. In addition, the maximum refractive index sensitivity (RIS) of the SPR-PCF sensor is as excessive as 4847 nm/RIU. These proposed SPR-PCF temperature sensors have an easy nanostructure and proper sensing performance, which now not solely improve the overall sensing performance of small-diameter fiber optic temperature sensors, but also have vast application prospects in geo-logical exploration, biological monitoring, and meteorological prediction due to their remarkable RIS and exclusive nanostructure.

Optical temperature sensing behavior of aluminum sheet fused with CaSrSiO4:Yb3+, Er3+ phosphor

In this work, Al–CaSrSiO4:Yb3+,Er3+ temperature sensing materials were prepared by the high-temperature solid-phase reaction method, and the upconversion photoluminescence characteristics and optical temperature sensing properties were measured and discussed. Two intense green emissions were observed under the excitation of 980 nm semiconductor laser. The temperature sensing performance of the thermally coupled energy levels was evaluated based on the fluorescence intensity ratio technique in the temperature range from 303 to 723 K, and the maximum sensor sensitivity of the synthesized sample reaches 0.0059 K−1 at 453 K. Furthermore, the relationships between the absolute sensitivity SA and temperature T as well as between SA and energy gap ΔE are analyzed in depth. And then, a strategy to quickly match the temperature measurement range to a suitable temperature sensing material was proposed, and the as-prepared Al–CaSrSiO4:Yb3+,Er3+ sample was determined to be suitable for measuring the high-temperature environment. These observations suggest that Al–CaSrSiO4:Yb3+,Er3+ samples have promising applications for non-contact optical temperature measurement at high temperature and high sensitivity.

Highly sensitive detection of amoxicillin by polyaniline-AgBr amperometry sensor: Fabrication and application in tap water and lake water

In the human body, edible substances through water-polluting ingredients amplify the antibiotics that lead to harmful influences on health. State-of-the-art methods are inherently required to identify trace impurities in various aqueous mediums. We present amperometry amoxicillin (AMX) sensor fabrication and electrochemical performance using functionalized polyaniline-silver bromide (PANI-AgBr) hybrids. The intramolecular bonds of anilinium and bromide free radicals (–NH-Ag+-O- and –NH-Br°-NH-) give rise to synergistic effects. The flexible polyethylene terephthalate-designed carbon screen-printed electrodes (PET-SPEs) have recognized the AMX concentration. Modified SPEs produce rapidly escalated current amperometry responses. Cyclic voltammetry and linear kinetic analysis authenticate the experimental errors and assess the maximum sensitivity of the AMX antibiotic sensor. The sensor efficiently resulted in the AMX detection under optimized conditions in the ultra-low range (0.193–0.855 nM) and reached the 0.193 nM minimum detection limit. The wide detection range (1–500 ppb) scheme has excellent selectivity, repeatability, and stability, acquiring significant peak potentials to detect the AMX in natural water samples.

Facile synthesis, characterization and acetone sensing properties of n-type WO3, SnO2 and VO2 semiconducting materials and their cobalt doped performance: Outstanding SnO2-Co acetone selectivity and sensitivity

The n-type Semiconducting Metal Oxides have been widely studied and numerous studies have been reported on their excellent result to Volatile Organic Compounds such as ZnO, WO3, SnO2 etc., however their working temperature, response, selectivity, and long-term stability still require improvement. In this paper much effort has been put to improve the performance of acetone sensors by enhancing the surface activity, gas diffusion and decreasing the grain size. The n-type semiconducting sensors and their cobalt doped-counterparts were synthesized by a facile hydrothermal method. The SnO2-Co showed a maximum sensor sensitivity (Ra/Rg) to be as high as 45.8 at an operating temperature of 100 °C when exposed to 5 ppm of acetone. Additionally, the SnO2-Co sensor showed high selectivity to 5 ppm of acetone. The results demonstrate that the SnO2-Co architectures can be used for the detection of low acetone concentrations and have potential for the early diagnosis of diabetes.

HE1,1 mode excited surface plasmon resonance for high-sensitivity sensing by photonic crystal fibers.

Surface plasmon resonance (SPR) is widely used in photonic crystal fiber sensors. In this work, a photonic crystal fiber sensor based on HE1,1 mode excited SPR is designed and analyzed by the finite element method. The maximum wavelength sensitivity, optimal resolution, and amplitude sensitivity of the optical fiber sensor are 24,600 nm/RIU, 4.07×10-6RIU, and 1164.13RIU-1, respectively, for the refractive index range between 1.29 and 1.39. The sensor has excellent properties and wide application prospects in bimolecular and biochemical sensing, environmental monitoring, food safety, and other fields.

Coupling plasmon-waveguide resonance and multiple plasma modes in hyperbolic metamaterials for high-performance sensing

A sensor based on plasmon-waveguide resonance (PWR) exhibits an impressive narrow linewidth and has attracted extensive attention in plasmon label-free sensing. However, the low surface electric field intensity limits the detection ability of biomolecules, where the refractive index changes are restricted at the sensor surface. In this study, we study the coupling of PWR and multiple plasma modes in a hyperbolic metamaterial (HMM), combining narrow linewidth and electric field enhancement advantages. The PWR-HMM sensor includes a gold film, lossless dielectric layer, and metal/dielectric multilayer HMM array composed of 2-layer Au/Al2O3 stacks. The evanescent field of PWR is used to excite multiple plasma modes in the HMM. The figure of merit of the proposed structure reaches 5417/RIU owing to the existence of lossless dielectric layer, which is 11.7 times than the conventional gold film structure. The maximum bulk sensitivity of the PWR-HMM sensor was 43 000 nm/RIU. In comparison with PWR, the surface electric field intensity and the surface sensitivity of PWR-HMM increase by four and two times, respectively. Furthermore, comparing the sensing performance of the PWR-HMM sensor and PWR-nanoparticle (NP) sensor (coupling PWR and localized surface plasmon resonance), it was found that PWR-HMM has 20% higher surface sensitivity than the PWR-NP. A sensing mechanism coupling PWR and multiple plasma modes in the HMMs opens a gate to significantly improve the PWR sensors performance, which is expected to be used to resolve urgent issues in biological, medical and clinical applications.

Energy density capability and upconversion luminescence in Er3+/Yb3+-codoping BNT-based ferroelectric thin films

Smart materials with multiple functions are the preferred materials for technological applications in military, medical, aerospace science and technology, and architecture. However, developing newly single-phase material coupling with multiple functions is still subjects with enormous challenge. Herein, the rare-earth elements Er3+/Yb3+ substitution of lead-free 0.7Bi0·5Na0·5TiO3-0.3Sr0·7Bi0·2TiO3 (BNT-SBT) ferroelectric thin films are designed and fabricated to improve energy storage capability and upconversion luminescence. Optimized BNT-SBT thin films achieves superior discharged energy density of 52.4 J/cm3 with high efficiency of 70.2%, as well as excellent temperature stability (RT to 150 °C) and fatigue endurance (107 circles). Additionally, the emission color of BNT-SBT thin films could be controlled through changing Yb3+ ion concentrations. More importantly, the maximum sensor sensitivity of the Er3+/Yb3+ codoped BNT-SBT thin films could reach 0.0049 K−1 at 363 K. This contribution paves a novel avenue for preparing lead-free multifunctional ferroelectric thin films, which are interested in potential application in the field of optoelectronic devices.

A MEMS Electrochemical Seismometer Based on the Integrated Structure of Centrosymmetric Four Electrodes.

This paper presented an electrochemical seismic micro sensor based on an integrated structure of four centrosymmetric electrodes. In this integrative structure, cathodes were not only distributed on wafer surfaces but also on the inner walls of the flow holes of the wafer, which increased the effective cathode areas and improved the sensitivity of the sensor. Numerical simulations were conducted to validate the feasibility of the integrated structure of four centrosymmetric electrodes in monitoring seismic vibrations where variations in the arrangements of the flow holes and anode width were investigated. The integrated structure of the four centrosymmetric micro electrodes was fabricated based on Micro-Electro-Mechanical Systems (MEMS) without the requirement of manual alignments. Experimental characterizations revealed that: (1) the maximum sensitivity of the electrochemical seismic sensor based on the integrated structure of four centrosymmetric electrodes was two orders of magnitude higher than that of the commercial counterpart of CME6011 and three times higher than the electrochemical seismic sensor based on the integrated structure of four planar micro electrodes; (2) the electrochemical seismic sensor based on the integrated structure of four centrosymmetric micro electrodes demonstrated comparable and even lower noise levels in comparison to CME6011. Thus, the electrochemical seismic micro sensor developed in this study may function as an enabling tool in future applications of seismic monitoring and geophysical explorations.

Magnetic Sensing System for Potential Applications in Deep Earth Extremes for Long-Term Continuous Monitoring

Long-term monitoring of weak changes in the magnetic field in the deep part of the Earth, allows to detect anomalies related to the pre-natural disaster stage at the onset of the deformation of the earth’s crust. However, standard electronic instruments are unable to work under high temperatures and high-pressure harsh environments for a long time. To address this problem, an in-well magnetic field measurement system, including a three-axis “residence times difference” fluxgate magnetometer, a heat exchange system with a coolant, and a control module, is designed. The measured maximum sensor sensitivity at room temperature is 0.02 s/(A/m). The rms input noise is within ±2 nT, corresponding to a noise spectral density of 200 pT/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> @1 Hz, that is sufficient to accurately detect the fluctuations of the geomagnetic field. The feasibility of the system was verified in laboratory at four temperatures, from 120°C to 210°C, corresponding to 2000 m - 5000m subsurface depths. When, in the experiments performed at 210 °C, the magnetic field was changed of some hundreds of nT, the sensor outputs responded very well in the three directions, with a dynamic detectability of few tens of nT. The control module maintains the internal temperature in the range 25 °C - 40 °C when the external temperature varies between 120 °C and 210°C, allowing a good long-term stability, as demonstrated by aging tests in laboratory. Finally, field experiments were conducted to verify the engineering feasibility of the system for ten days at 100 m depth and 15~18 °C.

Refractive index sensor based on Fano resonance in a ring with a rectangular cavity structure

This paper presents an innovative plasmonics-based refractive index sensor structure that consists of a circular ring containing a rectangular cavity (CRRC) and a metal–insulator–metal (MIM) waveguide with two rectangular stubs. The narrowband mode of the CRRC interacts with the broadband mode of the bus waveguide stub to generate sharp and asymmetric Fano resonance. The transmission characteristics were simulated using the finite element method. A maximum refractive-index sensor sensitivity of 2300 nm/RIU and figure of merit (FOM) of 57.5 were achieved. The proposed structure is simple yet highly sensitive and has the potential to be useful in detecting electrolyte concentration in blood. The results of this study provide a foundation for developing highly sensitive plasmonic sensors biomedical applications.

High-frequency electric field intensity sensor based on double-slot waveguides filled with electro-optical polymer

We consider the structure of a high-frequency external electric field sensor based on microring resonators using waveguides with two horizontal or vertical slots filled with an electro-optical polymer. The method of lines is used to calculate the propagation constants and mode field distributions of such waveguides. It is shown that double-slot waveguides filled with an electro-optical polymer exhibit higher optical radiation intensity in the slot region compared to single-slot waveguides, which makes it possible to increase the sensor sensitivity. The distances between the slots and the values of their widths at which a maximum sensor sensitivity is achieved are determined. The sensor allows alternating electric fields with frequencies up to 10 GHz to be measured in the range of 100−16 × 106 V m−1 with an accuracy of 150 V m−1.

Enhanced Sensitivity and Detection of Near-Infrared Refractive Index Sensor with Plasmonic Multilayers.

In this work, the multilayer of the surface plasmon resonance (SPR) sensor was optimized to achieve the maximum sensor sensitivity. By optimizing the thickness of the silver layer (Ag) and dielectric films (TiO2 and AlAs), the optimum sensitivity of the SPR sensor could be obtained. The performance of the SPR sensor proposed was compared with control simulations utilizing zinc oxide (ZnO) and molybdenum oxide (MoO3). The numerical results indicate that the figure-of-merits (FOM) of the SPR sensor was achieved around 150/RIU, corresponding to the sensor sensitivity of 162.79°/RIU with the optimized thicknesses of the TiO2, Ag, and AlAs layers of 140 nm, 60 nm, and 25 nm, respectively. This refractive index sensor shows the FOM to have high detection accuracy and high sensitivity that lead to finding potential application in bio-chemical detection with a small volume of liquid used in biological diagnosis.

Simulation analysis and experimental verification for sensitivity of IDE-QCM humidity sensors

• A facile and effective approach to improve the sensitivity of piezoelectric quartz crystal humidity sensors was presented. • Both IDE and QCM are used as sensitive components to improve humidity sensitivity. • The superposition relationship of the frequency change in IDE-PQC and QCM was proved using equivalent circuit method. • The sensitivity of the IDE-QCM humidity sensor reaches 262.21 Hz/%RH in the humidity range of 11.3–97.3 % RH. This paper proposes a new, simple, and effective approach that uses both an interdigital electrode (IDE) and a quartz crystal microbalance (QCM) as sensitive components to improve humidity sensitivity. First, a simulation analysis of the equivalent electronic circuit was used to verify that the frequency response of the IDE-QCM humidity sensor is the sum of that of the QCM and interdigital electrode-piezoelectric quartz crystal (IDE-PQC) sensors. Then, cellulose nanocrystals (CNCs) were used as humidity-sensitive materials deposited on IDE and QCMs, respectively, to fabricate several PQC sensors. The humidity-sensing performances of all sensors were tested at room temperature, including the dynamic response, sensitivity, response/recovery time, repeatability, and long-term stability. The experimental results prove the superposition relationship and can be used to enhance the humidity sensitivity. The maximum sensitivity of the IDE-QCM sensor reaches 262.21 Hz/%RH in the humidity range of 11.3 %–97.3 %, which is higher than that of all frequency-modulated piezoelectric quartz crystal humidity sensors. Moreover, the humidity hysteresis (∼ 8.1 %RH) and response/recovery time (68/4 s) did not significantly increase compared with the IDE-PQC and QCM sensors. All the sensors exhibited good repeatability and long-term stability. Finally, the humidity-sensing mechanism of the CNC-based IDE-QCM sensor is discussed in detail. This work demonstrates that using both IDE and QCM as sensitive elements is a simple and effective method to improve the humidity sensitivity of frequency-modulated piezoelectric quartz crystal sensors. This superposition relationship of capacitance-inductance frequency modulation to enhance sensitivity also provides an excellent reference for the design of other high-performance sensors.

Optical Temperature Sensing of YbNbO4:Er3+ Phosphors Synthesized by Hydrothermal Method

The novel YbNbO4:Er3+ phosphors were firstly synthesized through the hydrothermal method by adding LiOH·H2O as flux in the H2O/EG system. YbNbO4:Er3+ phosphors showed the agglomerated irregular polygons coexisting with some tiny grains. XRD and Raman spectra were measured to understand the phase structure and the crystal growth mechanism of YbNbO4:Er3+ phosphors. The upconversion (UC) emission spectra, the pump power dependency and UC mechanism were studied under 980 nm excitation. Based on the fluorescence intensity ratio technique, YbNbO4:Er3+ exhibited the maximum sensor sensitivity of 0.00712 K−1 at 220 K, providing a promising application in optical low-temperature sensors.

Model improvement for super-Nernstian pH sensors: the effect of surface hydration

The maximum sensitivity of pH sensors is given by the Nernst equation, and its theoretical value is 59.2 mV pH−1. However, countless sensors developed and reported in the literature have their sensitivity higher than the Nernstian limit. These are called super-Nernstian sensors. To understand the causes of this behavior, the sensitivity of polyaniline thin films was studied by evaluation of an important parameter: the hydration of the film’s surface. Sensitivities were measured before and after varied heat treatments, and the sensor's parameters were associated with the amount of water lost in the process. Polyaniline thin films were fabricated by galvanostatic electrodeposition in aqueous solution, and their sensitivity was measured before and after heating of the samples. An endothermic process, typical of evaporation, was revealed by the analysis of mass loss during the heating process. A decrease in the sensitivity of the films was observed after heating process. For comparison, polyaniline thin films were also fabricated by spin coating, in the absence of water, and their sensitivity proved to be smaller than for the galvanostatically fabricated ones and it did not change significantly after the heating processes. The results indicated that the Nernst model can be adjusted using a parameter ( $$1/r$$ ) related to the hydration of the surface of the sample, which directly affects the sensitivity of the thin films. The lowest reachable $$1/r$$ value for samples containing no water is approximately 0.9. The parameter also describes the upper limits for the sensitivity of super-Nernstian sensors.

Up- and downconversion emission studies in Er3+/Yb3+: Ca3 (PO4)2 phosphor for thermometry

Up- and downconversion emission and sensing sensitivity is studied in Er3+/Yb3+ co-doped biocompatible Ca3(PO4)2 phosphor synthesized via co-precipitation (CPT) and hydrothermal (HYDT) methods. The emission bands are observed at 523, 549 & 656 nm due to the 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions, respectively on excitation under 980 nm diode laser. The sample prepared via hydrothermal method has shown higher upconversion emission as compared to the sample prepared via co-precipitation method. The temperature sensing performance on green upconverted-emission from two thermally coupled 2H11/2 and 4S3/2 levels of Er3+ ion was measured in the 300–473 K temperature range and maximum sensor sensitivity of 0.34 %/K for HYDT and 0.26 %/K for CPT sample at 300 K is observed. Cell survivability at various sample concentrations (0 μM to 100 μM) was studied and finally, no significant toxicity on WI-38 cells was assessed by the MTT assay method.

Ultra high-sensitive, prompt response and recovering Pt/(Pt+SiO2) cermet layer/GaN-based hydrogen sensor for life-saving applications

In this work, we report an ultra-high sensitive (S = 1.4 × 108%), prompt response and recovering Pt/Pt+SiO2 cermet layer/GaN-based hydrogen (H2) sensor. A sensor fabricated with a 15 nm cermet layer, comprising Pt and SiO2, deposited between 15 nm Pt and GaN layers, exhibits significantly enhanced sensitivity in the detection of 4 %H2 by ≈ 300×, as compared to the reference Pt/GaN sensor at ambient temperature (300 K). Furthermore, the sensitivity of the our sensor shows very weak dependence on temperature (T) with maximum sensitivity () reducing from 1.4 × 108% to 2.3 × 107% as temperature increases from 300 to 423 K. The shift in the threshold voltage of the test sensor (ΔVt,test = 767 mV) increases by 50 % as compared to the shift in threshold voltage of the control sensor (ΔVt,control = 511 mV) at 1 mA/cm2. In addition, the cermet sensor also demonstrates fast response/recovery time, which reduces from 4.58 (2.36) seconds to 94 (39) milliseconds as the temperature increases from 300 to 423 K. The maximum sensitivity (), response (τa) and recovery (τb) times of the test sensor when exposed to 10 000 ppm of H2 are 3.9 × 107%, 30 secs and 30.1 secs respectively. The shift in the threshold voltage of the test sensor at 1 mA/cm2 when exposed to 100 ppm, 1000 ppm, 5000 ppm, and 10 000 ppm are 40 mV, 70 mV, 460 mV, and 600 mV, respectively. The 2-Dimensional (2D) trapping of H-atoms by the oxygen atoms present in the Pt+SiO2 cermet layer and porous/compact layer models explains the underlying mechanism, which results in a significant improvement of the sensing characteristics of the test sensor. The Thermionic Emission (TE) model effectively models the current density (J) - voltage (V) characteristics of both control and test sensors, with and without hydrogen. The prompt detection of high percentages of hydrogen in life-saving and commercial fuel applications becomes possible with the Pt+SiO2 cermet-based sensor, with its response and recovery times in the order of milliseconds for a temperature range of 363–423 K.