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Modulated up-conversion luminescence and low-temperature sensing of Gd3Ga5O12:Yb3+/Er3+ by incorporation of Fe3+ ions
摘要： Yb3+/Er3+ co-doped crystals show strong up-conversion luminescence and their temperature dependence of luminescence intensity enable the application of temperature sensors. Such sensors usually work at hundreds Kelvin with high sensitivity, while the sensors appropriate to very low temperatures are rarely reported. In this study, we report the low temperature sensing of Gd3Ga5O12:Yb3+/Er3+ nanocrystals by partial or total substitution of Ga3+ by Fe3+ ions. The up-conversion photoluminescence of the nanocrystals is measured on cooling from 300 to 4.2 K. The low-temperature sensing performance is improved, and the structure, magnetic and optical properties are modulated by the substitution of Fe3+ ions, rendering the nanocrystal useful for multi-functional sensing application.
关键词： Temperature sensor,Magnetic doping,Photoluminescence,Up-conversion
更新于2025-09-23 15:23:52
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Synthesis of ZnO nanowires/Au nanoparticles hybrid by a facile one-pot method and their enhanced NO2 sensing properties
摘要： ZnO nanowires (ZNWs) and ZnO nanowires/Au nanoparticles hybrid (Au-ZNWs) with various Au concentrations were synthesized by a facile one-pot hydrothermal method and characterized by XRD, SEM, TEM, XPS, and FTIR. The structural characterization results exhibited that Au nanoparticles were self-assembled onto the surface of ZNWs and the c-axis growth of ZNWs is suppressed by the addition of HAuCl4 in the synthesis of Au-ZNWs hybrid. Gas sensing properties demonstrated the favorite sensing performance could be achieved for 1 mol% Au-ZNWs compared to pure ZNWs and Au-ZNWs with other Au concentrations. The maximum response of 1 mol% Au-ZNWs to 1 ppm NO2 was 31.4 at 150 °C, which was nearly 4 times higher than 8.2 of pure ZNWs. And the shortest response and recovery times could also be achieved by 1 mol% Au-ZNWs in a wide range of operating temperature. Au-ZNWs with various Au concentrations showed better selectivity to NO2 than pure ZNWs. The mechanism of enhanced NO2 sensing performance of Au-ZNWs was investigated by the combination of electronic and chemical sensitizations via Au nanoparticles functionalization.
关键词： NO2,Nanowires,Gas sensor,Au functionalization,ZnO
更新于2025-09-23 15:23:52
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Squeezing-induced giant Goos-H?nchen shift and hypersensitized displacement sensor in a two-level atomic system
摘要： We analyze an efficient scheme to enhance the Goos-H?nchen (GH) shifts of the reflected and transmitted beams in a cavity containing two-level atomic medium. A broadband squeezed vacuum field is injected into the cavity to interact with the atomic medium. In the bad cavity limit, the Bloch equations for the atomic operators are identical to those in the free space, but with the modification of the system parameters. Using experimentally achievable parameters, we identify the conditions under which the squeezed vacuum allows us to enhance the GH shifts of the reflected and transmitted beams beyond what is achievable in the absence of the squeezed vacuum. The enhanced GH shifts originate from the coherent population oscillations controlled by the squeezed vacuum field. Furthermore, we also find that the GH shifts of the reflected and transmitted beams depend sensitively on the relative phase between the control field and the squeezed vacuum field. Subsequently, we propose a scheme for such a configuration of the GH shift as a family of hypersensitized displacement sensors. Based on the numerical analysis, the detection sensitivity and minimum detectable value for the tiny displacement can reach approximately 2340 μm/nm and 14.4 pm, respectively.
关键词： coherent population oscillations,Goos-H?nchen shift,two-level atomic system,displacement sensor,squeezed vacuum
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Auckland (2018.8.5-2018.8.8)] 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - An Automatic Sun Tracking System for Fiber Optic Lighting
摘要： An automatic sun tracking system for fiber optic lighting is proposed. Using STC89C52RC microcontroller as the core controller, together with the steering gear to control the system daylighting, the system is able to trigger the sun tracking system and auxiliary lighting system automatically for overheating protection and brightness adjustment. A practical sun tracking system with hardware and software is implemented and validated by experiments.
关键词： steering gear,sensor,sun tracking system,Fiber optic lighting
更新于2025-09-23 15:23:52
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Role of solvent H-bonding and polarity on photophysical properties of a benzothiazole-based ratiometric amyloid fibril sensor
摘要： Detailed photophysical properties of 2-[2′-Me,4′-(dimethylamino)-phenyl]benzothiazole (2Me-DABT), a potential ratiometric amyloid fibril sensor, have been investigated in different solvents and solvent mixtures using steady state and time-resolved spectroscopic techniques. Our studies show that emission properties of 2Me-DABT are significantly modulated by polarity of solvent media. Extent of solvatochromism (3585 cm?1) shown by 2Me-DABT is quite large and can be used to monitor micropolarity of different complex media. Further, Stokes’ shift (> 10,000 cm?1) shown by 2Me-DABT in all studied solvents is also much larger than most common molecular probes. It has also been shown that hydrogen bonding with solvent molecules results in large modulation in photophysical properties of 2Me-DABT. The H-bonding with water molecules induces a large change (39°) in the dihedral angle between benzothiazole and aniline moieties resulting large changes in photophysical properties of 2Me-DABT in polar protic solvents. Photophysical properties reported herein are used to explain observed amyloid sensing behaviour of 2Me-DABT. Detailed quantum chemical calculations are performed to support the experimental results.
关键词： Amyloid sensor,H-bonding,Photophysics,Time-resolved spectroscopy,Fluorescence
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE Biomedical Circuits and Systems Conference (BioCAS) - Cleveland, OH, USA (2018.10.17-2018.10.19)] 2018 IEEE Biomedical Circuits and Systems Conference (BioCAS) - Monitoring Red Blood Cell Aggregation Dynamics in Stasis and Under Flow Using a Microfluidic Dielectric Sensor
摘要： This paper reports on monitoring the red blood cell (RBC) aggregation dynamics under flow and in static condition using a microfluidic dielectric sensor. The sensor employs a three-dimensional (3D), parallel-plate, capacitive sensing structure with a floating electrode integrated into a microfluidic channel with a height of 50μm. Using an impedance analyzer, the sensor is shown to measure the real part of complex relative dielectric permittivity of human whole blood in a frequency range of 10kHz–100MHz under flow and in static condition. The dielectric permittivity of human whole blood at 1MHz indicates the formation of RBC aggregate structures called rouleaux under static condition and their complete breakdown under a physiological shear flow rate of 500s-1. This work also demonstrates that the kinetics of RBC aggregation is dependent on fibrinogen concentration of the blood sample and establishes that the sensor is capable of distinguishing this difference in the aggregation process even under physiological shear flow rates. This work demonstrates the potential of dielectric spectroscopy in obtaining information on RBC aggregation dynamics using μL-volumes of whole blood under flow and in stasis.
关键词： red blood cells,capacitive sensor,dielectric spectroscopy,Aggregation,rouleaux formation,microfluidics
更新于2025-09-23 15:23:52
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A microporous Tb-MOF luminescent sensor based on a flexible tricarboxylate for highly sensitive detection of acetone and Fe3+ ions in aqueous and isopropanol
摘要： One novel microporous terbium (III) framework, [Tb(DBB)(H2O)2](1), has been prepared from 4-(3,5-dicarboxylatobenzyloxy) benzoic acid (DBB) with terbium salt under hydrothermal condition. Structural analysis shows complex 1 possesses three-dimensional frameworks based on 2D double sheets linking by DBB ligands into porous channels. The gas adsorption experiments of N2 and CO2 show that complex 1 possesses microporous properties. Fluorescence analyses exhibit the characteristic luminescence of Tb3+ ion both in solid state and in aqueous. In particular, the Tb-MOF can detect acetone for its luminescence entirely quenching in acetone. Furthermore, the ionic detection experiments indicate complex 1 could be a good sensor for highly and sensitively sensing Fe3+ ion in aqueous and isopropanol, and the detection limit could reach at 10?9 M in aqueous.
关键词： The microporous Tb-framework,Luminescent sensor for acetone and Fe(III) ion,Crystal structure
更新于2025-09-23 15:23:52
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CO Gas Sensor based on E-beam Evaporated ZnO, MgZnO and CdZnO Thin Films: A Comparative Study
摘要： This paper reports a comparative study of electron-beam evaporated ZnO, MgZnO and CdZnO thin film based gas sensor. At room temperature (RT), these semiconductive thin films were deposited on Si/SiO2 substrate and an interdigitated pattern of chromium electrode deposited on these films. Device properties such as structural, optical and electrical have been reported and analyzed. The sensors have been tested at different operating temperatures. At 250 ℃, the sensor shows the best response for CdZnO thin films. We have obtained sensor response 4.86 with response time 15 sec for 100 PPM carbon mono oxide (CO) gas concentration for CdZnO thin film. Based on experimental results, Cd-doped ZnO has been found most suitable among these semiconducting metal oxides, when used as a CO gas sensor. A correlation between structural, optical and electrical properties with these thin films has also been established.
关键词： Thin film,ZnO,MgZnO,CO Gas sensor,CdZnO,E-beam evaporation
更新于2025-09-23 15:23:52
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An interferometric structure with a dual-resonance long period grating for strain sensing
摘要： Spectral characteristics and amplitude tunability of a long period grating with a dual-resonance inside fiber loop mirror are studied in terms of applied stress caused by elongation. Inserting the polarization controller between grating and part of polarization maintaining fiber in the loop structure enables tuning of resonance and interferometric peaks. The maximum sensitivity of demonstrated sensor is of 1.943 dB/mε for the range of 1.1–4.4 mε. Combination of these two optical components allows to measure strain in a wider range comparing with sensors based on standard long period grating.
关键词： Fiber loop mirror,Polarization controller,Polarization maintaining fiber,Strain sensor,Long period grating
更新于2025-09-23 15:23:52
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Investigation of an in-line fiber Mach–Zehnder interferometer based on peanut-shape structure for refractive index sensing
摘要： An in-line fiber Mach–Zehnder interferometer (MZI) for refractive index (RI) sensing was proposed, and the interferometer was fabricated by cascading two peanut-shape structures in the single mode fiber using the commercial fusion splicer. A model of the peanut-shape profile was used to calculate the power distribution of the modes in the device. The RI sensing performances of the peanut-shape structure in-line fiber MZIs with two different arm length (30 and 100 mm) were investigated. As the sensor with a short arm length of 30 mm, the RI sensitivity of ?67.355 nm/RIU was achieved for the RI range of 1.33–1.37. As the sensor with a long arm length of 100 mm, the simultaneous RI and temperature measurement was realized to eliminate the temperature and RI cross sensitivity, and the highest RI and temperature sensitivities of ?67.953 nm/RIU and 0.073 nm/?C were obtained, respectively.
关键词： Simultaneous refractive index and temperature measurement,Optical fiber sensor,Refractive index measurement,Mach–Zehnder interferometer,Peanut-shape structure
更新于2025-09-23 15:23:52