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Significant improved selectivity of a fluorescent sensor for Al3+ made from a fluorinated rhodamine B Schiff base
摘要： Two rhodamine B-based Schiff bases (RBF, RBC) with different substituent groups (–F and –COOH) have been synthesized. In order to study the sensing properties of two Schiff bases for metal ions, the interaction of Schiff bases with different metal ions was studied over UV–Vis absorption spectra and photofluorescent spectra. The results show that the RBF is a turn-on fluorescent chemosensor for Al3+ ions with being highly selective and sensitive in ethanol. The value of the fluorescence increase factor shows a good linear relationship with the concentration of Al3+ in the range of 1–9 μM with a detection limit of 0.8 μM. Meanwhile, upon addition of Al3+ or Fe3+ ions, the fluorescence intensity of RBC increased significantly (FAl3+/FFe3+ = 0.77). These studies show that, compared with the carboxyl group (–COOH), the introduction of fluorine atoms (–F) to a rhodamine B-based Schiff base can significantly improve selectivity to Al3+.
关键词： Al3+ ion,Fluorine atoms,Fluorescent sensor,Rhodamine B
更新于2025-09-23 15:23:52
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A fluorescent Eu(III) MOF for highly selective and sensitive sensing of picric acid
摘要： A metal-organic framework [Eu3L3(CH3COO)2(H2O)2(μ3-OH)]?3DMF, (EuL, H2L=9H-carbazole-2,7-dicarboxylic acid, DMF=N,N-dimethylformamide) has been synthesized under solvothermal conditions and structurally characterized. In EuL, Eu6O8 clusters are four-bridged by carboxylates to form parallel-aligned Eu–O–C chains, which are further linked by the carbazole moieties of L2? ligands to form the three-dimensional framework with rhombic channels. The EuL material with characteristic emission of Eu3+ ion exhibits significant luminescence quenching response for picric acid (PA) and the linear Stern-Volmer plot was observed in the concentration range of 0.05–0.15 mM with Ksv of 98074 M?1. As far as we know, this Ksv is among the highest values for COFs and MOFs in detection of PA. The excellent anti-interference ability and repeatability were also verified by experiments. Lastly, we investigated the luminescence quenching mechanism in the EuL sensing system.
关键词： europium,picric acid,sensor,metal-organic frameworks
更新于2025-09-23 15:23:52
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Correlation of surface processes with characteristic sensing responses of PdO thin films to ethanol
摘要： Gas sensing characteristics of PdO nanoflake thin films exposed to ethanol (EtOH) at temperatures below 250 °C was studied. The PdO thin film responds distinctly to 0.15 ppm EtOH in dry air at temperatures above 100 °C. A characteristic valley-shaped response feature develops in the early stage of the exposure to EtOH at 150 °C and above. Formation of the valley feature is a result of the combined effects of two types of surface processes, which successively modify the sensor conductance in the opposite way. Dehydrogenation of adsorbed EtOH induces reduction of preadsorbed oxygen anions and the PdO substrate, resulting in the drop of the conductance. On the other hand, subsequent adsorption of EtOH and oxygen on newly growing Pd nanoclusters, which develop due to the reduction of the PdO substrate, causes the increase in the conductance. The Pd nanoclusters can be later reoxidized in the EtOH gas mixture, thereby modifying the sensing behavior of the PdO sensor. X-ray photoelectron spectroscopy (XPS), diffusive reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature programmed desorption (TPD) were used to study adspecies and gaseous species formed in the EtOH gas sensing reactions. On the basis of the characteristic electrical response and chemical characterizations, we proposed the formation mechanism for the characteristic response feature.
关键词： Pd nanoclusters,Dehydrogenation,Reduction,PdO,Ethanol,MOS gas sensor
更新于2025-09-23 15:23:52
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Core-shell structure of ZnO/Co3O4 composites derived from bimetallic-organic frameworks with superior sensing performance for ethanol gas
摘要： In recent years, metal-organic frameworks (MOFs), especially zeolite-imidazole frameworks (ZIFs), have been attracting widespread attention as templates for the synthesis of sensing materials. Limited researches, however, have been carried out to utilize bimetallic ZIFs in gas sensing, as the existing studies mostly involve mono-metallic ZIFs. Here in, the core-shell structure of ZnO and Co3O4 composite (CS-ZnO/Co3O4) was synthesized via chemical etched to Co/Zn based zeolitic imidazolate framework (Co/Zn-ZIF) with subsequent annealing. The morphology, composition and surface characteristics of the as-obtained samples were confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET). Moreover, the gas sensing measurements were implemented under various atmospheres. The response of CS-ZnO/Co3O4 sensor to 100 ppm ethanol at 200 °C achieves 38.87, which is 2.8 times that of single-shell ZnO/Co3O4 (SS-ZnO/Co3O4). The improved response is mainly attributed to the core-shell structure, which offers larger surface area, more active sites for gas diffusion and the formation of p-n heterojunction between ZnO and Co3O4.
关键词： Bimetallic-organic framework,Core-shell structure,ZnO/Co3O4,Ethanol gas sensor
更新于2025-09-23 15:23:52
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Fully Packaged Portable Thin Film Biosensor for the Direct Detection of Highly Pathogenic Viruses from On-Site Samples
摘要： The thin film transistor (TFT) is a promising biosensor system with great sensitivity, label-free detection, and a quick response time. However, even though the TFT sensor has such advantageous characteristics, the disadvantages hamper the TFT sensor's application in the clinical field. The TFT is susceptible to light, noise, vibration, and limited usage, and this significantly limits its on-site potential as a practical biosensor. Herein, we developed a fully packaged, portable TFT electrochemical biosensor into a chip form, providing both portability through minimizing the laboratory equipment size and multiple safe usages by protecting the semiconductor sensor. Additionally, a safe environment that serves as a miniature probe station minimizes the previously mentioned disadvantages, while providing the means to properly link the TFT biosensor with a portable analyzer. The biosensor was taken into a biosafety level 3 (BSL-3) laboratory setting to analyze highly pathogenic avian influenza virus (HPAIV) samples. This virus quickly accumulates within a host, and therefore, early stage detection is critical to deterring the further spread of the deadly disease to other areas. However, current on-site methods have poor limits of detection (105?106 EID50/mL), and because the virus has low concentration in its early stages, it cannot be detected easily. We have compared the sample measurements from our device with virus concentration data obtained from a RT-PCR (virus range: 100?104 EID50/mL) and have identified an increasing voltage signal which corresponds to increasing virus concentration.
关键词： avian influenza virus,label-free detection,portable biosensor,chip sensor,rapid detection
更新于2025-09-23 15:23:52
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Morpholino Oligonucleotide Cross-Linked Hydrogels as Portable Optical Oligonucleotide Biosensors
摘要： Morpholino Oligonucleotides (MOs), an uncharged DNA analogue, are functionalized with an acrylamide moiety and incorporated into polymer hydrogels as responsive crosslinks for microRNA sequence detection. The MO crosslinks can be selectively cleaved by a short target analyte single-stranded DNA (ssDNA) sequence based on microRNA, inducing a distinct swelling response measured optically. The MO crosslinks offer significant improvement over DNA based systems through improved thermal stability, no salt requirement and 1000-fold improved sensitivity over a comparative biosensor, facilitating a wider range of sensing conditions. Analysis was also achieved using a mobile phone camera, demonstrating portability.
关键词： microRNA,Biosensor,Oligonucleotide sensor,Morpholino oligonucleotide,Hydrogel
更新于2025-09-23 15:23:52
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Deformation sensing and electrical compensation of smart skin antenna structure with optimal fiber Bragg grating strain sensor placements
摘要： Skin antenna structure is a kind of multifunctional composite structure in which printed antennas are integrated. This paper proposes a new smart skin antenna structure with embedded fiber Bragg grating (FBG) strain sensors. Utilizing the measured strains from limited FBG strain sensors, the deformation shapes are reconstructed by using a strain–displacement transformation, and the deteriorated radiation patterns caused by the deformations are compensated by using a strain-electromagnetic coupling mode which is derived and validated for the first time in the paper. Moreover, a two-step sensor placement method considering the information redundancy is proposed to determine optimal FBG strain sensor locations. The comparisons show that the two-step sensor placement method is advantageous in terms of the sensor distribution and computational cost. The fabrication process of the smart skin antenna structure was presented, and an experimental system with optimal sensor placements was developed. The measured results demonstrate that the reconstructed shapes agree well with the real ones, and that the deteriorated radiating patterns were almost completely restored to the desired ones. The proposed smart skin antenna structure which can provide the electromagnetic receiving-sending, structural deformation monitoring and electrical correction functions has a potential application prospect in the future mobile vehicle.
关键词： Fiber Bragg grating,Deformation sensing,Electrical compensation,Smart skin antenna,Optimal sensor placement
更新于2025-09-23 15:23:52
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Design and development of a novel level transmitter utilizing lithium niobate (LiNbO3) Mach-Zehnder modulator for hazardous regions
摘要： In the proposed work, a very low-cost transducer and a novel photonic based transmission technique have developed for liquid level measurement. Two copper parallel plates are used to measure the liquid level in the sensing tube. For transmission of the measured quantity to the remote location, electrical (1–5 V DC), as well as optical technique, has been used. A lithium niobate (LiNbO3) based Mach Zehnder interferometer has been used for the optical transmission. In the proposed method 40GHz, Photline made MXAN-LN-40 light intensity Mach-Zehnder modulator was used. The optical output was analyzed with the help of optical spectrum analyzer (MS9710B) as well as optical meter. Optical transmission was not affected by EMI interference and very advantageous in the inflammable regions. With the help of the proposed method, the sensitivity of 7.02 pF/cm. from the sensor and ?0.236 dBm/cm. from the modulator were achieved. The output of the sensor, signal conditioning, and optically transmitted data has been analyzed experimentally.
关键词： Level transmitter,Optical intensity modulator,Optical spectrum analyzer (OSA),Level sensor,Optical power meter
更新于2025-09-23 15:23:52
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Superstructure Fiber Bragg Gratings for Simultaneous Temperature and Strain Measurement
摘要： A new and simple fiber optic sensor based on a superstructure fiber Bragg grating (SFBG) for simultaneous temperature and strain measurement is proposed. The SFBG is a superimposed grating for which a long period fiber grating (LPG) and a fiber Bragg grating (FBG) is written in the same section of a Corning SMF-28 fiber. The reflection spectrum of the SFBG possesses two resonant peaks and a trough. By measuring the wavelength shift of the main resonant peak and the reflection power change of the trough, temperature and strain can be determined simultaneously. The accuracy of the sensor in measuring strain and temperature is estimated to be ±13.01 με in a range from 0 με to 1000 με and ±0.75 ℃ from 20 ℃ to 100 ℃, respectively.
关键词： CO2 laser,SFBG,simultaneous measurement of temperature and strain,fiber optic sensor
更新于2025-09-23 15:23:52
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Fluorescent sensor for copper(II) ion based on coumarin derivative and its application in cell imaging
摘要： A novel fluorescent sensor CHT was designed based on the excellent optical properties of coumarin derivatives. It was synthesized by Schiff base reaction connected by 7-(N,N-diethylamino) coumarin-3-aldehyde and 2-hydrazinobenzothiazole. The sensor CHT displayed exhibited a significant fluorescence quenching at 540 nm upon the addition of Cu2+ ions. And the sensor exhibited good sensitivity, fast response time, high selectivity for Cu2+ ions in the presence of other important relevant metal ions. In addition, CHT fluorescent sensor was successfully applied for fluorescent imaging of Cu2+ ions in A549 and MCF-7 cells, demonstrating its potential applications in live cell imaging.
关键词： fluorescent sensor,coumarin,cell imaging,copper(II) ion
更新于2025-09-23 15:23:52