Excellent Sensor Properties Research Articles

Highly Efficient Electrochemical Sensing of Acetaminophen by Cobalt Oxide-Embedded Nitrogen-Doped Hollow Carbon Spheres.

With respect to sensor application investigations, hollow mesoporous carbon sphere-based materials of the spinel type of cobalt oxide (Co3O4) and heteroatom-doped materials are gaining popularity. In this contribution, dopamine hydrochloride (DA) and cobalt phthalocyanine (CoPc) precursors were employed to construct a highly homogeneous Co3O4-embedded N-doped hollow carbon sphere (Co3O4@NHCS) by a straightforward one-step polymerization procedure. The resulting Co3O4@NHCS materials may effectively tune the surface area, defect sites, and doping amount of N and Co elements by altering the loading amount of CoPc. The relatively high surface area, greater spherical wall thickness, enriched defect sites, and better extent of N and Co sites are all visible in the best 200 mg loaded Co3O4@NHCS-2 material. This leads to significant improvement in pyridine and graphitic N site concentrations, which offers exceptional electrochemical performance. Electrochemical analysis was used to study the electrocatalytic activity of Co3O4@NHCSs towards the sensing of pharmacologically active significant compounds (acetaminophen). Excellent sensor properties include the linear range (0.001-0.2 and 1.0-8.0 mM), sensitivity, limit of detection (0.07 and 0.11 μM), and selectivity in the modified Co3O4@NHCSs/GCE. The authentic sample (acetaminophen tablet) produces a satisfactory result when used practically.

Oxygen vacancy-enriched ALD NiO sub-50 nm thin films for enhanced triethylamine detection

p-type metal oxide semiconductors have received significant interest in the field of gas sensors; however, it is quite challenging to achieve high sensor response because of inferior surface and electronic properties. Herein, we report a high-performance gas sensor fabricated by plasma-etching an NiO thin film deposited by atomic layer deposition. Ar plasma treatment is found to introduce a large number of oxygen vacancies, which effectively adjusts the electronic and chemical characteristics of the p-type NiO films to afford improved response to toxic triethylamine. The effects of the thickness of the sensing layer on sensor properties are also studied, which reveals that the NiO film with a thickness of 40 nm has the greatest gas sensing performance. After Ar plasma treatment, the response of the NiO thin films is significantly enhanced to enable an excellent limit of detection of 27.4 ppb, which is much lower than the threshold limit of 1 ppm proposed by American Conference of Governmental Industrial Hygienists. The demonstrated strategy and excellent sensor properties suggest a pathway to high performance gas sensors.

Mechanisms of NO2 Detection in Hybrid Structures Containing Reduced Graphene Oxide: A Review.

The sensitive detection of harmful gases, in particular nitrogen dioxide, is very important for our health and environment protection. Therefore, many papers on sensor materials used for NO2 detection have been published in recent years. Materials based on graphene and reduced graphene oxide deserve special attention, as they exhibit excellent sensor properties compared to the other materials. In this paper, we present the most recent advances in rGO hybrid materials developed for NO2 detection. We discuss their properties and, in particular, the mechanism of their interaction with NO2. We also present current problems occuring in this field.

Temperature-Stress Bimodal Sensing Conductive Hydrogel-Liquid Metal by Facile Synthesis for Smart Wearable Sensor.

Conductive hydrogels have attracted great attention due to their promising applications in wearable sensors. However, developing conductive hydrogels with excellent sensor properties and multiple stimuli responsiveness for smart wearable devices is still a challenge. This paper presents a facile synthetic method of a crosslinked chitosan quaternary ammonium salt and liquid metal (CHACC-LM) composite hydrogel with temperature-stress bimodal sensing for smart wearable sensor. LM as liquid fillers toughen the hydrogel matrix (stress: 1.11MPa) and enhance the hydrogel extensibility (strain: 233%). The CHACC-LM hydrogel exhibits conductivity , excellent antibacterial properties (> 99%), an electrical self-healing property, and strain sensitivity (GF = 1.6). In addition, the CHACC-LM hydrogel can be used as wearable flexible sensors with the ability of monitoring human activities directly and the distinguished ability of discerning subtle motions (handwriting). It also shows sensitivity in the external environment such as low temperature, thermal response, and water solution. Importantly, the composite hydrogel simultaneous response to different stress and temperature stimuli. Furthermore, the CHACC-LM hydrogel can be used for gesture recognition and to control the manipulator in human-computer interaction. All these properties provide a great scope for researchers to achieve practical advances in smart wearable sensors.

Electrochemical catechol biosensor based on β-cyclodextrin capped gold nanoparticles and inhibition effect of ibuprofen

Herein, β-cyclodextrin-capped gold nanoparticle surface designed for tyrosinase (Tyr)-based nanosensor is proposed and demonstrated. Integration of the β-cyclodextrin-capped gold nanoparticles on graphite electrode surface was achieved via drop-casting method, Tyr was immobilized on the modified electrode and then used as drug inhibition platform with catechol as the substrate. All optimization studies that affect biosensor response were conducted, and catechol was detected in the linear range of 1.56 μM-25μM catechol concentration with a limit of detection of 0.42 μM and sensitivity of 2.094 μA.μM−1. cm-2. Tyr inhibition was followed with ibuprofen drug active compound with a 15 min incubation time, and the I50 value was found as 213 μM. The sensor is the first in the literature to use an electrochemical method for β-cyclodextrin-capped gold nanoparticles based Tyr biosensor and ibuprofen inhibition. This sensor presents an easy fabrication method, excellent sensor properties, and ibuprofen inhibition capabilities. As a result, it is proposed that the designed sensor is an ideal marker for detecting Tyr inhibition using electrochemical methods and an ibuprofen-based cosmetic cream formulation could be a viable option in the cosmetic market.

Effect of forming gas annealing on SnO2 sensing membranes in high-performance silicon-on-insulator extended-gate field-effect transistors

In this study, we fabricated a dual-gate (DG) structured field-effect transistor (FET)-based pH sensor with an extended gate (EG) using a silicon-on-insulator (SOI) substrate. The DG-SOI-EGFETs achieved sensitivities significantly exceeding the theoretical maximum sensitivity (Nernstian limit) of conventional single-gate ion-sensitive FETs of ~59.16 mV/pH at 25 °C. For further improvement in the sensitivity and reliability of DG-SOI-EGFETs, we investigated the effects of forming gas annealing (FGA) temperature on the SnO2 film used as the EG sensing membrane. We evaluated the pH sensitivity of EG with SnO2 membranes after FGA at temperatures of 100–400 °C and investigated the hysteresis, drift effects, and response times. In addition, the chemical composition, crystallinity, sheet resistance, transmittance, and surface morphology of the SnO2 membranes with respect to FGA temperature were analyzed. As the temperature of FGA was increased, the SnO2 membrane showed increased crystallite size, transmittance, and surface roughness. However, the sheet resistance was decreased with increasing FGA temperature with a minimum at 300 °C before increasing again at 400 °C. Excellent sensor properties with high sensitivity, the fastest response time, and high reliability were obtained from FGA processing at 300 °C. Therefore, we found that the optimum FGA temperature for SnO2 films was 300 °C; this may facilitate the manufacture of EG sensing membranes for high-performance DG-SOI-EGFETs with improved sensitivity, stability, and reliability.

Controllable synthesis of hierarchical assembled porous ZnO microspheres for acetone gas sensor

Three dimensional hierarchical ZnO micro-/nanostructures with controlled morphology and dimensionality are successfully synthesized through a facile aqueous solution route. The results of morphology, structure and microstructure of the 3D ZnO microspheres show that the microspheres are composed of interconnected nanosheets/nanorods with the uniform size of 1–2μm. Gas sensors based on hierarchically ZnO microspheres show high sensitivity for acetone as well as quick response and recovery time due to the high surface-to-volume ratio. The results show that the prepared 3D hierarchically ZnO microsphere demonstrated excellent sensor properties in terms of higher sensitivity and very fast response because of the unique structures.

Synthesis, Self-Assembly, and High Performance in Gas Sensing of X-Shaped Iron Oxide Crystals

X-shaped goethite iron oxide crystals were synthesized by a surfactant-free mild hydrothermal synthesis method with the aid of fluorine ions. The X-shaped goethite crystals could readily self-assemble into microscopic hollow spheres through an oil-water interface induced self-assembly method. X-shaped hematite crystals were obtained by phase topotactic transformation of the goethite precursors. The gas sensor properties of X-shaped hematite iron oxide were investigated, and the mechanism for excellent sensor properties was discussed.

3D hierarchically porous ZnO structures and their functionalization by Aunanoparticles for gas sensors

Three-dimensional (3D) hierarchically porous nanostructures with controlled morphology and dimensionality represent one kind of important material and have received enormous attention for a series of applications. In this work, 3D hierarchically porous ZnO architectures were synthesized via an amino acid-assisted biomimetic hydrothermal method combined with subsequent calcination. First a basic zinc carbonate (BZC) precursor with a lamellar spherical morphology assembled by interconnected nanosheets was synthesized. By subsequent calcination, the as-obtained BZC precursor can be facilely transformed into porous ZnO with a large surface area of 193.7 m2/g, while maintaining its 3D hierarchical morphology. The 3D hierarchically porous ZnO superstructures are further employed as a support to load Au nanoparticles (AuNPs) to construct hybrid nanomaterials for chemical gas sensors. The AuNP-functionalized 3D hierarchically porous ZnO nanomaterials, combining the high surface accessibility of porous materials and catalytic activity of small AuNPs, demonstrated excellent sensor properties in terms of higher sensitivity and very fast response. Furthermore, it is expected this AuNP-functionalized 3D hierarchically porous nanostructure may provide a new pathway to develop advanced nanomaterials for applications like gas sensors, low temperature CO oxidation and photocatalysis.

Gas sensing properties of WO 3 thick film for NO 2 gas dependent on process condition

The thick film sensor of tungsten oxide for NO 2 gas detection was fabricated by changing the process conditions, which were firing temperature and annealing atmosphere. The origin of sensor property variation was interpreted by the characterization of crystallite size, specific surface area and microstructure. The degree of oxygen deficiency in the WO 3 sensor also affected sensor properties and the optimum oxygen content of WO 3 was necessary to get high sensitivity for NO 2. The WO 3 thick film fired at 700°C and operated at 100°C showed excellent sensor properties, and its operation temperature is lower than that from other reports.

Effect of Sorbed Water on the Dielectric Properties of Acetylene‐Terminated Polyimide Resins and Their Application to a Humidity Sensor

A cured acetylene‐terminated polyisoimide oligomer was used to prepare a capacitive‐type humidity sensor. Sorption behavior of water on the cured film was examined by measuring the dielectric constant and water content. The amount of sorbed water was small and the sorbed water did not form clusters. This is due to the hydrophobic nature and rigid structure of the film. The sorption behavior reflects its excellent sensor properties, i.e., low hysteresis, low temperature coefficient, durability against acetone vapor, and long‐term stability in a high temperature and humid atmosphere. Among the polyimides prepared by curing the oligomers with different chain lengths, the most suitable composition for a reliable capacitive‐type humidity sensor was API‐3‐API‐1.

高強度を有する多孔質圧電セラミックスの作製と評価

In general, the porous lead- titanate-zirconate ceramics, Pb(Zr, Ti)O3 exhibit the excellent properties for ultrasonic sensor, though the mechanical properties are not so good for their porous structure. The wide application for electronics components was restricted because of their poor reliance. In this study, the Pb(Zr, Ti)O3/SiC whisker composites (PZT/SiC) were prepared by the normal ceramics processing. With the increase in the contents of SiC whisker, the electrical and mechanical properties changed gradually. For the study of the change in properties, the microstructures were investigated by the scanning electron microscopy (SEM) and transmittion electron microscopy (TEM). The results obtained is as follows;SiC+2O2 ?? SiO2+CO2SiO2+Pb(Zr, Ti)O3 ?? Pb, Zr, Ti, Si glass.The grain boundary and three pockets were coated by this glass. As a result, the mechanical properties of bending strength and fracture toughness, K1c increased. By using this idea, the porous PZT ultrasonic sensor with a high mechanical strength has been developed and the excellent sensor properties were obtained;piezoelectric constant=99-110×10-3 Vm/Nbending strength =50 kg/cm2.