Response Performance Of Sensors Research Articles

Enhanced Long-Range Surface Plasmon Effect Based on Zr2CO2 MXene and MoSe2 Heterostructures for SPR Biosensors With High FOM

MXenes-based van der Waals heterojunction materials with excellent chemical stability and bioaffinity have been widely used in biosensing in recent years. We propose a new MoSe2@Zr2CO2 heterostructure as a long-range surface plasmon resonance (LRSPR) sensor based on the Kretschmann configuration from simulation and optimize the structure parameters algorithmically. First, we investigate the effect of different layers of MoSe2@Zr2CO2 heterojunction on the LRSPR wave. The results show that the optimal number of layers for heterogeneous layers is 18. Second, the effects of dielectric thickness and refractive index (RI) on sensitivity are investigated in depth, and optimized structural parameters are obtained. Finally, the effect of prisms with different refractive coefficients on the sensor performance is also discussed, and it is shown that prisms with lower refractive coefficients can effectively improve the sensitivity performance of the sensor. The sensor response performance to biomolecules is greatly enhanced due to the gain of light absorption and SPR. Compared with the conventional precious metal Au-based (50 nm) thin-film SPR sensor, the figure of merit (FOM) of the sensor is improved by a factor of 8.16, and higher sensitivity (92.48°/RIU) and quality factor (QF) (319.63 RIU−1) are obtained in the visible range.

Tunable fano resonance-enhanced surface plasmon biosensor based on MXene/MoS2 heterostructure

Two-dimensional materials have unique physical properties such as high electrical conductivity, excellent light absorption, and hydrophilicity, thus have been widely used as responsive materials for surface plasmon effect sensors in recent years. Here, we propose a Kretschmann configuration-based MXenes/MoS2 heterostructure film material as an improved sensing layer for surface plasmon resonance (SPR) sensors and introduce an optical waveguide layer into the nanostructure to achieve a remarkable Fano resonance (FR). By separately adjusting the thickness and refractive index of the coupling dielectric and optical waveguide layers, the effective coupling between the surface plasmon polarization and the planar optical waveguide mode is achieved, which significantly improves the sensor's response performance to biomolecules and achieves high sensitivity (S, 86.13°/RIU) and better figure of merit (FOM, 281.74 RIU−1) in the visible red range (around 632.8 nm). Benefiting from the light absorption gain of the heterostructure and the FR effect, the FOM of the MXene/MoS2 Fano resonance sensor (FRS) is improved by 7.1 times compared to the traditional SPR sensor based on noble metal Au (50 nm thickness) thin film.

Synthesis of Highly Dispersed CuPd@UiO-66-NH2 for Nonenzymatic Hydrazine Sensing

In this article, a core–shell CuPd@UiO-66-NH2 composite material was synthesized by a double-solvent reduction method, and an N2H4 electrochemical sensor based on CuPd@UiO-66-NH2 was constructed. The relationship between the morphology, type, composition, size of the sensor interface composite material and its electrocatalytic performance and sensor response performance was studied, and a new method for detecting N2H4 was established. The surface properties and composition of the materials were studied by transmission electron microscope(TEM),energy dispersive X-ray spectroscopy(EDX) and X-ray diffraction spectroscopy(XRD). The results showed that the synthesized CuPd@UiO-66-NH2 has a regular 3D structure, particle dispersion, and uniform particle size, the particle size is about 90 nm. Electrochemical performance studies showed the sensor is made into detecting N2H4 in a linear range of 0.25 μM ∼ 1.39 mM, with a sensitivity of 386.7 μA·mM−1·cm−2, and a detection limit of 0.08 μM(S/N = 3). Compared with other electrochemical sensors based on metal nanoparticles to detect N2H4, the new sensor exhibited a wider linear range; and its sensitivity was 3 times of that obtained by the Cu-BTC/OMC/GCE. So, the sensor can be used as a potential sensing material to detect hydrazine.

Synthesis of single-crystal α-MnO2 nanotubes-loaded Ag@C core–shell matrix and their application for electrochemical sensing of nonenzymatic hydrogen peroxide

A nonenzymatic hydrogen peroxide sensor was fabricated by combing the crystal α-MnO2 nanotubes and Ag@C core–shell matrix with their own superior characteristics. The morphology, size and electrochemical of the sensing interface materials and the relationship between the electrical catalytic properties and sensor response performance were also studied, established a new method for the detection of hydrogen peroxide (H2O2). The structure and morphology of hollow tubular-like MnO2 and MnO2-Ag@C film were characterized by scanning electron micrograph (SEM), transmission electron microscopy (TEM) and X-ray diffraction. The electrochemical properties of the sensor were explored by cyclic voltammetry and amperometry. The investigation showed that the MnO2-Ag@C at the sensor exhibited a high electrocatalytic activity towards electroreduction of hydrogen peroxide; and under the optimal conditions, the linear ranges of hydrogen peroxide were 0.5μM to 5.7mM with a low detection limit of 0.17μM (S/N=3) and high sensitivity of 127.2μAmM−1cm−2. Compared with other nonenzymatic hydrogen peroxide sensor, the fabricated sensor own lower detection limit, demonstrating that MnO2-Ag@C nanocomposite film will be a new promising platform for the construction of hydrogen peroxide sensors.

Porous Au-embedded WO3 Nanowire Structure for Efficient Detection of CH4 and H2S.

We developed a facile method to fabricate highly porous Au-embedded WO3 nanowire structures for efficient sensing of CH4 and H2S gases. Highly porous single-wall carbon nanotubes were used as template to fabricate WO3 nanowire structures with high porosity. Gold nanoparticles were decorated on the tungsten nanowires by dipping in HAuCl4 solution, followed by oxidation. The surface morphology, structure, and electrical properties of the fabricated WO3 and Au-embedded WO3 nanowire structures were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and current–voltage measurements. Formation of a nanowire structure resulted in significant enhancement in sensing response to H2S and CH4 gases. Furthermore, Au embedment into the WO3 nanowire structures remarkably improved the performance of the sensors. The increase in response performance of sensors and adsorption–desorption kinetic processes on the sensing layers were discussed in relation with the role of Au embedment.

Synthesis and characterization of N-(4-Aminophenylethynylbenzonitrile)-N′ -(1-naphthoyl)thiourea as single molecular chemosensor for carbon monoxide sensing

This contribution reports on the design, preparation, and characterization of a novel acetylide-thiourea presenting N-(4-Aminophenylethynylbenzonitrile)-N′-(1-naphthoyl)thiourea (AETU) obtained from continuous reaction of intermediate compound 4[(4aminophenyl)ethynyl benzonitrile] (AMEB) with 1-naphthoyl chloride prior to form an active substrate for the detection of carbon monoxide (CO). These compounds were then characterized via several spectroscopic and analytical methods, namely Fourier transform infrared spectroscopy, UV–visible spectroscopy, nuclear magnetic resonance (1H and 13C NMR), carbon, hydrogen, nitrogen, and sulfur elemental analysis, and Thermogravimetric analysis. The performance of sensor response toward CO was measured using difference response in spectral features of UV–VIS spectrophotometry in thin-film studies with and without the presence of CO. The findings revealed that AETU possibly has an interaction with CO of concentrations 10, 20 and 30 ppm. In addition, quantum chemical calculations also proved that AETU exhibits potential sense interaction toward CO with stabilization energy−6.30 kJ/mol and interaction distance is about 3.14 Ǻ. This proposed material sensor gives an ideal indication for application in the aspect of direct detection of CO in real sample and for development of single molecule gas sensor devices.

NH3 sensing properties of ZnO thin films prepared via sol–gel method

An 80nm-thick ZnO film was prepared via the sol–gel method at 500°C using zinc acetate, 2-methoxyethanol, and monoethanolamine as precursors. Characterization of the film showed that it was composed of 20–30nm sintered ZnO nanoparticles with good crystallinity. The NH3 sensing properties of gas-sensing devices with a 5μm gap that utilized the prepared ZnO film were examined. The highest sensor response (57.5%) was achieved with 600ppm NH3 in air at 150°C. The response and recovery times were 160s and 660s, respectively. This study also examined the effects of NH3 and oxygen concentration as well as the temperature on the sensor response performance. The findings show that oxygen plays an important role in the conductivity of ZnO thin films, and thus affects the sensor response toward NH3.

Reducing cross-sensitivity of TiO2-(B) nanowires to humidity using ultraviolet illumination for trace explosive detection

Environmental humidity is an important factor that can influence the sensing performance of a metal oxide. TiO2-(B) in the form of nanowires has been demonstrated to be a promising material for the detection of explosive gases such as 2,4,6-trinitrotoluene (TNT). However, the elimination of cross-sensitivity of the explosive detectors based on TiO2-(B) toward environmental humidity is still a major challenge. It was found that the cross-sensitivity could be effectively modulated when the thin film of TiO2-(B) nanowires was exposed to ultraviolet (UV) light during the detection of explosives under operating conditions. Such a modulation of sensing responses of TiO2-(B) nanowires to explosives by UV light was attributed to a photocatalytic effect, with which the water adsorbed on the TiO2-(B) nanowire surface was split and therefore the sensor response performance was less affected. It was revealed that the cross-sensitivity could be suppressed up to 51% when exposed to UV light of 365 nm wavelength with an intensity of 40 mW cm(-2). This finding proves that the reduction of cross-sensitivity to humidity through UV irradiation is an effective approach that can improve the performance of a sensor based on TiO2-(B) nanowires for the detection of explosive gas.

Porous tungsten oxide nanoflakes for highly alcohol sensitive performance

Porous tungsten oxide (WO(3)) nanoflakes have been synthesized by a simple and green approach in an ambient environment. As a precursor solution a polycrystalline hydrated tungstite (H(2)WO(4)·H(2)O) nanoparticles colloid was first prepared by pulsed-laser ablation of a tungsten target in water. The H(2)WO(4)·H(2)O nanoflakes were produced by 72 h aging treatment at room temperature. Finally, porous WO(3) nanoflakes were synthesized by annealing at 800 °C for 4 h. Considering the large surface-to-volume ratio of porous nanoflakes, a porous WO(3) nanoflake gas sensor was fabricated, which exhibits an excellent sensor response performance to alcohol concentrations in the range of 20 to 600 ppm under low working temperature. This high response was attributed to the highly crystalline and porous flake-like morphology, which leads to effective adsorption and desorption, and provides more active sites for the gas molecules' reaction. These findings showed that the porous tungsten oxide nanoflake has great potential in gas-sensing performance.

Electrodeposited Cobalt-Iron Alloy Thin-Film for Potentiometric Hydrogen Phosphate-Ion Sensor

A cobalt-iron alloy thin-film electrode-based electrochemical hydrogen-phosphate-ion sensor was prepared by electrodepositing on an Au-coated Al2O3 substrate from an aqueous solution of metal-salts. The use of a cobalt-iron alloy electrode greatly improved the hydrogen-ion sensor response performance, i.e., the sensor worked stably for more than 7 weeks and showed a quick response time of several seconds. Among the cobalt and iron alloy systems tested, the electrodeposited Co58Fe42 thin-film electrode showed the best EMF response characteristics, i.e., the sensor exhibited a linear potentiometric response to hydrogen-phosphate ion at the concentration range between 1.0 × 10–5 and 1.0 × 10–2 M with the slope of –43 mV/decade at pH 5.0 and at 30℃. A sensing mechanism of the Co-based potentiometric hydrogen-phosphate ion sensor was proposed on the basis of results of instrumental analysis.

Influence of Anion Doped Polypyrrole Film as Ion-to-Electron Transducer on the Response Performance of Internal Solid Contact Potentiometric Sensors

The internal solid contact potentiometric sensors (ISCSs) based on the use of conducting polymers (e.g. polypyrrole (PPy), polyaniline(PAn) etc.) as inner contact ion-to-electron transducer material and ion-selective polymeric membrane as the ion sensing membrane possess pronounced potential stabilities, in comparison with the coated wire electrodes. Furthermore, the response performances of ISCS are mainly dependent on the composition of the polymeric sensing membrane including the types of ionophore, plasticizer, ionic additives, and their mass percentages. This study is focused on investigating experimentally whether there is a negligible effect of an anion doped within PPy film for an ISCS on the response performances of the sensor or not. Five anions including Cl−, , SCN−, ClCH2COO− and Cl3CCOO− were used as the doped anions and five types of ion exchanger were used as the electroactive substances in the ion-selective PVC membranes to fabricate these sensors. The results indicate that the nature of dopant can influence the response behaviors, such as detection limit, response slope and potential selectivity, of the ISCSs to some extent, which are dependent on the type of primary ion tested. The size and lipophilicity of dopant in PPy layer could be important factors influencing response performances of an ISCS. The origin of the influences has been discussed from models proposed in this paper.

Non-invasive method to detect and locate haemorrhagic focus of GI tract

Traditional diagnostic methods do not work well for gastrointestinal bleeding, and location of the haemorrhagic focus is even more difficult. Here a novel method with a microelectronic system is presented effectively to detect and locate the haemorrhagic focus. The outstanding advantage of this method is that it is non-invasive. The composition and working principles of the system are described in detail. Key to this system is the development of a haemoglobin (Hb) sensor. Through MEMS technology a micro haemoglobin sensor is developed and fabricated. The sensor's response performance, pH dependence and temperature dependence are tested experimentally. Initial tests suggest that the device is sufficiently sensitive to Hb concentration and insensitive to pH and temperature changes in the working range. As a result, the system has potential for development of an advanced instrument for detecting, localizing and treating gastrointestinal bleeding.