Sensor Basedon Research Articles

A bifunctional fluorescent sensor based-on Pillar[5]arene for efficient detection of MnO4− as an oxidant and Hg2+ ion in aqueous media: Bio-imaging in living cells

The high amounts of oxidants and heavy metal ions caused undesirable health results and the detection of these ions gained increasing importance with new techniques. This paper focuses on a fluorescent macrocyclic sensor based on Pillar[5]arene and Bodipy (Bodipy-P[5]arene) for the recognition of oxidants and heavy metal ions in aqueous solution. After the characterization of the macrocyclic ligand, the spectroscopic measurements were carried out by Uv–vis and fluorescence spectroscopies. The bifunctional fluorescent macrocycle, Bodipy-P[5]arene, presents to a dual effect with fluorescence quenching response for fluorometrically recognizing MnO4- and Hg2+ ions. Bodipy-P[5]arene has low detection limits of MnO4- and Hg2+ such as 1.15 × 10-7 M and 8.12 × 10-7 M, respectively. Moreover, both Bodipy-P[5]arene can respectively detect the target ions in acidic and basic mediums and the macrocyclic ligand has short response times. In addition, the Bodipy-P[5]arene probe demonstrates low cellular toxicity and exceptional membrane permeability, making it a successful tool for fluorescently imaging Hg2+ and MnO4- ions within living HeLa cells.

Humidity Sensor Based-on Quartz Crystal Microbalance of Sprayed Silver Nanoparticles Films

The silver nanoparticles (Ag NPs) film was prepared in this work by the electrostatic spray deposition technique. The Ag NPs film properties were characterized by X-ray diffraction, UV-visible spectrophotometer, Raman spectroscopy, and scanning electron microscope. Then, the Ag NPs film was prepared on a 2 MHz crystal microbalance to fabricate the humidity sensor. The measurement systems are composed of a fabricated sensor, oscillator circuit, and frequency counter. The sensor performances were obtained in terms of the frequency shift of the device at various humidity levels. The conditions of saturated salt solutions following NIST standard were used as humidity values for measurement. It was found that the fabricated device exhibited approximately a frequency shift of 25 Hz in the humidity range of 11-93 %RH. Moreover, the device demonstrated low hysteresis at a value of about 1%RH with a humidity level of 43 %RH.

Topological enhancement of evanescent field localization in all-dielectric metasurfaces

Bound states in a continuum in periodic photonic structures can be described as topological defects in the k-space. These vortices can migrate within the Brillouin zone when the geometrical parameters of the system vary. In this study, we focus on the migration of the polarization vortex across the light line, from the radiation continuum to the waveguide mode domain. We found that during this transition, the far-field polarization vortex transforms into a near-field vortex. This near-field vortex is characterized by an enhanced localization of the evanescent field due to the vanishing fundamental Fourier harmonic of the Bloch amplitude. This mechanism can be used to improve polaritonic devices and optical sensors based on all-dielectric metasurfaces by increasing the overlap between optical modes and 2D excitons or thin layers of bio-analytes.

Design and test of a FBG acceleration sensor basedon multi-stage flexible hinges.

High-precision and high-sensitivity vibration acceleration sensors have been a research hotspot in engineering technology, which play an important role in engineering structural health monitoring, earthquakes, tsunamis, and geological exploration. A novel, to the best of our knowledge, fiber Bragg grating (FBG) acceleration sensor incorporating a mass block and flexible hinge was proposed against the low sensitivity and poor transverse interference resistance of existing FBG acceleration sensors. The FBG accelerometer with the multi-stage flexible hinge was modeled and theoretically analyzed, the structural parameters of the sensor were optimized and actual sensors were developed, and a sensor performance test experiment was carried out in the end. The result suggested that the sensor's natural frequency was as high as 1400Hz, and its response was flat in the frequency range of 50-800Hz; its sensitivity was 18.4pm/g, linearity R 2 was 0.9983, and transverse interference immunity was below 3.2%. The research findings offered a new way of thinking about high-precision and high-sensitivity vibration measurement in engineering technology.

Synthesis and Characterization of SnO2/BNNTs Nanocomposite for Ethanol Vapour Sensing at Room Temperature

Ethanol vapour sensors based on tin oxide (SnO2) nanoparticles onto boron nitride nanotubes (BNNTs) have been synthesized as a promising solution for detecting ethanol vapour in air. The existence of encapsulation of BNNTs over SnO2 i.e. SnO2/BNNT was confirmed by AFM, FTIR and current-voltage characteristics. Activation energy of sensor has been investigated to study the nature of synthesized material. Ethanol sensitivity, responsiveness and response-recovery durations of the SnO2-BNNTs sensor, as well as other sensing features, was examined by exposure to various ethanol vapour concentrations starting from 70 to 500 mL/min at room temperature with increasing rate of pressure value at room temperature. The SnO2 nanoparticles have a high sensitivity to ethanol vapour, while BNNTs enhance the sensing performance and stability of the sensor. This is achieved by combining BNNT (large surface area) and SnO2 (good electrical conductivity). The ethanol vapour sensor based on SnO2-BNNTs has been shown to have a good response and recovery time around 1 min and 2 s, respectively. With its high sensitivity of ~110 and stability, it is an excellent option for practical applications.

HYDROGEN SENSOR BASED ON Pd/InP STRUCTURES

The development of a photoelectrical hydrogen sensor without sensor element heating is presented. For the sensitive element of the hydrogen sensor the Pd/n-InP (Schottkie diode) and Pd/oxide/InP (met-alinsulator-semiconductor) structures were developed and investigations of the photovoltage and the photocurrent of the structures depending on the hydrogen concentration in the range 0.1–100 vol.% in a nitrogen-hydrogen gas mixture were carried out. It is shown that the photovoltage and photocurrent decay rate and the hydrogen concentration are exponentially related to each other. The laboratory samples of sensor for
 hydrogen determination in the range 100–30000 ppm which able to operate at room temperature with response
 rate of 1–2 s are developed.

A fully water-soluble Calix[4]arene probe for fluorometric and colorimetric detection of toxic hydrosulfide and cyanide ions: Practicability in living cells and food samples

Although hydrosulfide and cyanide anions play important roles in daily life that they are available in a lot of foods. However, their excess amounts contaminate water, land, and food and cause serious problems to human health. Herein, we introduce a water-soluble macrocyclic sensor based-on Calix[4]arene (MPI-Calix[4]) with dual response sites for fluorescence recognizing cyanide (CN–) and hydrogen sulfide (HS-) under longwave light. MPI-Calix[4] exhibits a high selectivity and sensitivity in the detection of CN– and HS-, where the limits of detection were as low as 0.115 and 8.12 μmol/L, respectively. The cell imaging studies shows that this probe can be easily used in the detection of CN– and HS- on living cells. Full understanding of these results paved a fruitful system to improve an applicable analytical process for food safety and quality.

Single-mode fiber curvature sensor based on SPR.

A fiber surface plasmon resonance (SPR) sensor is widely used in high-sensitivity refractive index measurement, but there is less research on curvature measurement. In this paper, a single-mode fiber curvature sensor based on SPR is designed and fabricated. By employing bending, the transmitted light in the fiber core leaks into the cladding. A 50 nm gold film is coated outside the cladding, and the evanescent field of the cladding after bending contacts the gold film to cause SPR. When the curvature changes, the coupled cladding mode and intensity are different; that is, the SPR incident angle and evanescent field intensity are different, so as to realize the dual parameters of SPR resonance wavelength and depth of the resonance valley changing with curvature. By experiments, the influence of different cutoff wavelengths of single-mode fiber on the performance of the sensor is studied. The testing results indicate that with the decrease in cutoff wavelength of the single-mode fiber, the valley depth sensitivity of the sensor increases, and the half height width (FWHM) decreases. When the cutoff wavelength of the single-mode fiber is 630 nm, the valley depth sensitivity of the sensor is 0.0088a.u/m-1, the wavelength sensitivity is 0.26nm/m-1, and the average FWHM is only 21 nm. The proposed single-mode fiber curvature sensor based on SPR has a narrow FWHM and an opening threshold. It can also realize no opening threshold by introducing a coreless fiber, which provides a new solution, to the best of our knowledge, for the diversified detection of fiber SPR sensors.

Fluorescent and Easy-Make Hybrid Sensor Based-on Silica Gel & BODIPY for the Detection of Cu (II) in Aqueous Medium: Fully Characterized, Effective and Visual Data

Cu (II) ion has potential roles in a lot of living metabolisms that its detection and removal are extremely important for flagship branches of science. In this paper, fluorescent and easy-make silica gel immobilized BODIPY were successfully prepared via a simple synthesis procedure for the rapid recognition of Cu (II) ions. The optimal emission and excitation wavelength of the synthesized hybrid material, Si-APTMS-BODIPY, was 543 nm and 460 nm, respectively. The new solid support surface fully characterized by several techniques has notable results and visual data for the detection of Cu (II) ion. The maximum fluorescent intensity of Si-APTMS-BODIPY was clearly quenched following the adding of Cu (II) ion owing to static and dynamic quenching mechanisms. Maybe, more importantly, there was a notable linear correlation between several concentrations of Cu (II) solution and the fluorescence quenching processes with a limit of detection (LOD) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.7 ~\mu \text{M}$ </tex-math></inline-formula> . Based on these, a fluorescent hybrid material having high selectivity and sensitivity was made up, and it provides a precious proposal for the recognition of Cu (II) ions.

STUDY OF TEMPERATURE COEFFICIENT OF RESISTANCE OF n-InSb FILMS ON i-GaAs (100) SUBSTRATE AND TEMPERATURE SENSORS BASED ON THEM

In the present work, explosive thermal evaporation was used to form n-InSb films on i-GaAs (100) substrates. The investigation results of crystal state, microstructure, phase and element composition, and electrical properties of n-InSb films deposited at the substrate temperature of 410-480°C are presented. It is shown that heteroepitaxial n-InSb films form in the deposition temperature of 410°C. At a substrate temperature of 430-440°C, the surface is inhomogeneous; precipitates oriented differently in the substrate plane are clearly observed. At a substrate temperature of 480°C, the phase composition of the film is a superposition of InSb and In phases, and the SEM image of the sample shows that the film is island-like. The resulting n-InSb films at a deposition temperature of 430°C have the highest temperature coefficient of resistance (-1.25 ± 0.02) %·deg-1. Temperature sensors based on n-InSb-i-GaAs show performance in a wide temperature range (-80°C to +150°C) and at liquid nitrogen temperature and can be used in the space industry and low-temperature electronics, as well as in the automotive and aircraft industries.

Nanozyme sensor based-on platinum-decorated polymer nanosphere for rapid and sensitive detection of Salmonella typhimurium with the naked eye

Increasingly frequent outbreaks of bacteria-caused illness heightened the need to develop a rapid, portable, sensitive, and reliable method for bacteria detection. Herein, a nanozyme Ps-Pt was synthesized by growing Pt nanoparticles (Pt) on the surface of carboxyl functionalized polymer nanospheres (Ps). The Pt endowed the Ps-Pt with ultrahigh peroxidase-like catalytic activity. Meanwhile, carboxyl groups enabled Ps-Pt to attach streptavidin via covalent binding, which showed higher activity and stability than physical adsorption. To get immune Ps-Pt (IPs-Pt), biotin-antibody was attached to the streptavidin modified Ps-Pt. The two-step binding method enabled the IPs-Pt to own more antibodies and possess high stability. Based on the immune nanozyme, a simple, sensitive colorimetric assay was reported for Salmonella typhimurium (S. typhi) detection. With the assay, as low as 100 CFU/mL S. typhi could be distinguished from the blank by measuring the absorbance, and the generated color change of 1000 CFU/mL S. typhi could be seen clearly with the naked eye. Additionally, the assay has been successfully applied to the detection of S. typhi in spiked milk, Luria-Bertani broth, and serum samples. The specificity and sensitivity of the IPs-Pt-based sensor demonstrated its feasibility in practical applications. Most importantly, the results of 24 single-blind milk samples demonstrated the high sensitivity and 100 % accuracy of the assay, indicated that the developed method could detect S. typhi in food samples.

High response methane sensor based on Au-modified hierarchical porous nanosheets-assembled ZnO microspheres

Detecting methane (CH4) gas is very important owing to its widely use as a fossil fuel with an explosive hazard in modern society. In this study, a CH4 gas sensor was prepared, which is based on hierarchical porous nanosheets-assembled Au/ZnO microspheres with diameters of 10–12 μm. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the textural properties and morphology of the nanocomposites. In addition, the gas sensing properties of the sensors basedon pure ZnO and Au/ZnO nanomaterials were systematically investigated. By modifier Au nanoparticles, the characteristics of ZnO based sensor for CH4 detection were significantly enhanced. Especially, the Au/ZnO based sensor with an Au content of 1.0 at.% exhibited the best sensing performances (4.16) of 100 ppm CH4 at 250 °C. Furthermore the sensor also exhibited a good linear relation (10–2000 ppm CH4 concentration), excellent repeatability, satisfactory stability and a low detection limit of detection (1.83 ppm). The possible enhanced sensing mechanism could be attributed to the synergism between the unique hierarchical porous nanosheets-assembled microspheres structure and the sensitizing actions utilized by the Au nanoparticles.

Co3O4 /N-doped RGO nanocomposites derived from MOFs and their highly enhanced gas sensing performance

Co3O4/N-doped reduced graphene oxide (N-RGO) nanocomposite with mesoporous structure was fabricated by using metal organic frameworks (MOFs) as both template and precursor growing on RGO sheets. Porous Co3O4 cubes were assembled and grown on the surface of N-RGO layers, while N was doped into RGO to form N-RGO in situ synthesis route. The effect of RGO initial concentration on structure, component and gas-sensing properties of Co3O4/N-RGO nanocomposite was studied. The gas-sensing result demonstrated that the sensor based-on Co3O4/N-RGO-0.5 (the mass of RGO was 0.5 mg) nanocomposite possessed better gas-sensing performances to ethanol, such as higher response, faster response-recovery time and lower working temperature than that of other samples. The enhanced gas-sensing properties of sensor based-on Co3O4/N-RGO-0.5 nanocomposite to ethanol could be attributed to increasing of specific surface area, coupling effect between Co3O4 and nitrogen doped RGO as well as the existence of N-doping RGO which improved electron transferring of material in sensing process. Co3O4/N-RGO-0.5 nanocomposite has been proved to be a promising gas-sensing material for detecting ethanol at a low temperature.

Analysis and estimation of NEP and DR in CMOS TOF-3D image sensor based on MDSI

This paper presents an accurate analysis of noise equivalent power ( NEP) and optical dynamic range ( DR), for CMOS-3D image sensor based-on, indirect time-of-flight ( TOF) technique with its derived algorithm: MDSI (multiple double short time integration). Considering, in addition, the maximum distance-range, scene features, and appropriate noise analysis a new approach for estimating NEP and DR has been proposed; exhibiting high correlation with MDSI principle, in contrast to the conventional approach where both parameters are only a function of incident-light power and integration time, which provides a general approach for all sort of image sensor including ordinary 2D image. Further analysis shows that NEP, for CMOS 3D-MDSI sensor, is at least 10 times the commonly quoted, and corresponds to the minimum required LASER-pulse power to achieve 90% of a given distance-range measurement, under a specific background light illumination (indoor/outdoor applications). Based-on the present analysis, an optimization criteria has been developed and applied to the design of 3D-MDSI sensor using 0.6 μm standard CMOS process; a good agreement between experiment results and the conducted analysis has been found.

Theoretical investigation on refractive index sensor basedon Bragg grating in micro/nanofiber

Subwavelength and nanometer diameter optical fibers have the optical property of enhanced evanescent fields, which makes them very sensitive to the index change of the ambient medium. In this paper, a novel refractometric sensor based on fiber Bragg grating in micro/nano-fiber (MNFBG) is proposed, integrating the enhanced evanescent fields of micro/nano-fiber (MNF) with wavelength choice feature of FBG, and the fabrication about MNFBG is discussed. Refractive index sensing characteristics is comprehensively investigated in theories, and the simulation of sensing the variation of ambient refractive index is performed by using the software of OptiGrating. Results show the sensitivity of the MNFBG is increasing with the decrease of the radium of the MNF. MNFBG with the radius of 400nm can achieve the sensitivity as high as 993nm/RIU. This value is enhanced by 170 times over that of the FBG with etched cladding, which demonstrates that MNFBG has great potential of application in miniaturized, high-sensitivity refractometric sensors.

100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming thefundamental limitation of network-based sensors

Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have beenconsidered impractical due to several fundamental limitations such as a poor sensitivityand small signal-to-noise ratio. Herein, we present a strategy to overcome thesefundamental problems and build highly-sensitive low-noise nanoscale sensors simply bycontrolling the structure of the SWNT networks. In this strategy, we prepared nanoscalewidth channels based on aligned SWNT networks using a directed assembly strategy.Significantly, the aligned network-based sensors with narrower channels exhibited evenbetter signal-to-noise ratio than those with wider channels, which is opposite toconventional random network-based sensors. As a proof of concept, we demonstrated100 nm scale low-noise sensors to detect mercury ions with the detection limit of∼1 pM, which is superior to any state-of-the-art portable detection system and is below theallowable limit of mercury ions in drinking water set by most government environmentalprotection agencies. This is the first demonstration of 100 nm scale low-noise sensors basedon SWNT networks. Considering the increased interests in high-density sensor arrays forhealthcare and environmental protection, our strategy should have a significant impact onvarious industrial applications.

Alcohol vapor sensory properties of nanostructured conjugated polymers

The response to relative humidity (RH) and alcohol vapors of resistive-type sensors basedon nanobeads of conjugated polymers, namely polyphenylacetylene (PPA) and copolymerpoly[phenylacetylene-(co-2-hydroxyethyl methacrylate)] (P(PA/HEMA)), wereinvestigated. Sensors based on ordered arrays of these nanostructured polymeric materialsshowed stable and reproducible current intensity variations in the range 10–90% of relativehumidity at room temperature. Both polymers also showed sensitivity to aliphatic chainprimary alcohols, and a fine tuning of the sensor response was obtained by varying thechain length of the alcohol in relation to the polarity. The nanostructured feature ofpolymeric-based membranes seems to have an effect on the sensing response andan enhancement of the sensitivity was observed for the response to water andalcohol vapor variations with respect to previous studies based on amorphouspolyphenylacetylene. High stability of the polymeric nanostructured membranes wasdetected with no aging after two weeks in continuum stressing measurement conditions.

Abstracts

NOVEL IMIDAZOLE PVC‐BASED MEMBRANE SENSOR BASED ON 4‐METHYL‐2,6 DIPHENYLTHIOPYRYLIUM by M. Reza Ganjali and H. Pirelahi, Department of Chemistry, Tehran University, Tehran, Iran; M. Abdi and M. Reza Sohrabi, Department of Chemistry, Islamic Azad University, Branch of North, Tehran, Iran; and A. Moradzadegun, Department of Chemistry, Shahid Chamran University, Ahvaz, Iran ABSTRACT: A novel poly(vinyl chloride) (PVC)‐based membrane sensor based on 4‐methyl‐2,6‐diphenylpyrylium perchlorate (MPPP) is presented. The best performance was obtained with a membrane containing 30% poly(vinyl chloride) (PVC), 53% plasticizer dibutyl phthalate (DBP), 7% ionophore MPPP and 10% oleic acid. The proposed membrane electrode responds to imidazole in a wide concentration range 1.0 × 10−5 to 1.0 × 10−1 M, with a sub‐Nernstian slope of +36.2 ± 0.2 mV per decade of activity of imidazole. The detection limit of the sensor is 2.0 × 10−6 M and can be used for at least four weeks without any measurable change in sensitivity. The sensitivity of the electrode is high enough to permit the detection of as little as 0.15 µg/mL of imidazole without any significant interference from high levels of other components such as common cations and anions and specially, amino acids. The potentiometric selectivity coefficient data revealed negligible interference from common cations, inorganic and organic anions and amino acids. The electrode shows a relatively fast response time in whole concentration range (<30 s). The proposed membrane electrode was used for fast direct potentiometric monitoring of imidazole in synthetic serum samples. Analytical Letters, 37(2), 179–190 (2004)

Delivering the right dose

For treatment with high intensity focused ultrasound (HIFU), delivering the correctamount of energy to the patient is critical. This paper describes a novel design of sensor basedon the pyroelectric principle for monitoring the output power from HIFU transducers of thetype used for tissue ablation. The sensor is intended to be minimally perturbing to theultrasound field, so that it can remain in the ultrasound field throughout treatment and providea constant monitor of ultrasound power. The main advantages of the technique are: power canbe measured or monitored without dismantling the HIFU system, thus reducing equipmentdowntime; power can be measured immediately before or during every patient treatment, thusensuring accurate dosimetry; power can be measured at the output levels used for treatment(whereas a radiation force balance may be damaged by overheating); the method usescomponents which are robust and simple to use compared to radiation force balances orhydrophone scanning systems.