High sensitivity detection of baicalein by N,S co⁃doped carbon dots and their application in biofluids

In this work,p⁃phenylenediamine and L⁃cysteine were used as raw materials,and water⁃soluble N,S co⁃doped carbon dots(N,S⁃CDs)with excellent performance were prepared through a one⁃step solvothermal method.The morphology and structure of N,S⁃CDs were characterized by transmission electron microscope,X⁃ray diffrac⁃tion,Fourier transform infrared spectroscopy,and X⁃ray photoelectron spectroscopy,and the basic photophysical properties were investigated via UV⁃Vis absorption spectra and fluorescence spectra.Meanwhile,the N,S⁃CDs have excellent luminescence stability with pH,ionic strength,radiation time,and storage time.Experimental results illus⁃trated the present sensor platform exhibited high sensitivity and selectivity in response to baicalein with a detection limit of 85 nmol·L-1.The quenching mechanism is proved to be the inner filter effect.In addition,this sensor can also detect baicalein in biofluids(serum and urine)with good accuracy and reproducibility.

Temperature and Salinity Dual-parameter Sensing Based on Forward Brillouin Scattering in 1060-XP SMF

A novel temperature and salinity discriminative sensing method based on forward Brillouin scattering(FBS)in 1060-XP single-mode fiber(SMF)is proposed.The measured frequency shifts corresponding to different radial acoustic modes in 1060-XP SMF show different sensitivities to temperature and salinity.Based on the new phenomenon that different radial acoustic modes have different frequency shift-temperature and frequency shift-salinity coefficients,we propose a novel method for simultaneously measuring temperature and salinity by measuring the frequency shift changes of two FBS scattering peaks.In a proof-of-concept experiment,the temperature and salinity measurement errors are 0.12℃and 0.29%,respectively.The proposed method for simultaneously measuring temperature and salinity has the potential applications such as ocean surveying,food manufacturing and pharmaceutical engineering.

A new type of fiber Bragg grating based seismic geophone

Aimed at the poor performance of conventional geophones in exploration for deeper and complex targets, we present the principle and theoretical design of a new geophone based on the optical fiber Bragg grating （FBG） sensing technology. The important parameters such as response functions are calculated theoretically. Because of the advantages of FBG sensing technology, the new FBG geophone has a high dynamic range of 94dB at （10-200 Hz）. This new generation of geophones will have wide use in seismic prospecting due to its higher sensitivity, lighter weight, and lower cost.

A bellow pressure fiber optic sensor for static ice pressure measurements

Static ice pressure affects safe operation of hydraulic structures. However, current detection methods are hindered by the following limitations： poor real-time performance and errors owing to the partial pressure of the surrounding wall on traditional electrical resistance strain bellow pressure sensors. We developed a fiber optic sensor with a special pressure bellow to monitor the static ice pressure on hydraulic structures and used the sensor to measure static pressure in laboratory ice growth and melting tests from -30℃ to 5℃. The sensor resolution is 0.02 kPa and its sensitivity is 2.74 × 10-4/kPa. The experiments suggest that the static ice pressure peaks twice during ice growth and melting. The first peak appears when the ice temperature drops to -15℃ owing to the liquid water to solid ice transition. The second peak appears at 0℃ owing to the thermal expansion of the ice during ice melting. The novel fiber optic sensor exhibits stable performance, high resolution, and high sensitivity and it can be used to monitor the static ice pressure during ice growth and melting.

DISTRIBUTED MICROBEND FIBER-OPTIC STRAIN SENSOR

The distributed strain sensor has significant application in real time measurement of strain status for large and important engineering structures such as aircraft, bridge and dam. In this paper, a quasi distributed optical fiber strain sensor system is set up using optical time domain reflect technique. The local strain sensors based on a novel microbend configuration are designed and applied to measure local strains along the optical fiber. As the result of the experimental research, the microbend sensors show high sensitivity, good linearity and repeatability in certain operation range.

EXPERIMENTAL STUDY ON OPTIC PERFORMANCES OF OPTIC FIBER BRAIDED IN CARBON FIBER BRAIDED COMPOSITES

D braiding technology has stimulated a great deal of interest in the world at large and been widely used in aerospace, military, civil construction and medical fields. Although 3 D braided composites have many good features, their features are very complicated. Optic fiber sensors can be multi braided into 3 D braided composites to fulfill a new kind of 3 D smart composites to monitor RTM process, study mechanical behaviors and damage states after molding, and monitor its own condition during service life. Since optic performances of optic fibers have direct and important relation to the performances of optic fiber sensors, experimental research is done to devise a method to incorporate the optic fiber into a 3 D structure. The optical performances of the braided optic fibers are tested and compared with the original one to study the optic performances of optic fibers, before their being braided into composites and after the RTM process.

PLASMA RESONANCE FIBER OPTIC SENSOR FOR CURE MONITORING OF EPOXY COMPOSITE

The plasma resonance fiber optic sensor has a research values in theory and is widely used in engineering because of its simple structure and high sensitivity. It is a simple and sensitive method to measure the refractive index with optical fiber plasma wave. We make use of this characteristic to manufacture the plasma resonance fiber optic sensor which can detect the cure of epoxy compo site. We study the method of testing the solutions which have different refractive index with plasma resonance fiber optic sensor. A fiber optic sensing probe which has reliable performance and convenient operation for detecting the refractive index has been designed. The system for detecting the solution refractive index is developed and used to measure the refractive index of epoxy during the different phases in the cure process. Result shows that this system is credible and stable, the parameters tested are in accord with the facts.

AN OPTICAL FIBER SENSOR TECHNIQUE BASED ON SLIGHT DISTURBANCE RADIATION LOSS OF STOCHASTIC WALL

This paper presents an optical sensor technique used in the damage evaluation which is formed by structurally integrated fiber optic reticulate sensors embedded in the composite materials. The fibers are processed by chemical method and their outsides are peeled to form particles of irregular distribution and they differ in size, so the slight disturbance range of stochastic wall are formed in fibers. According to the characteristics of power loss of waveguide mode caused by slight disturbance of stochastic wall and radiative mode transmission, the range of slight disturbance of stochastic wall may be served as the sensitive range of the sensor. On the basis of theory of slight disturbance of stochastic wall of planar optical waveguide, the relation between the corrosion time and the opposite power loss by experiments is investigated. In this paper, the measurement results of object of SIFORS are also presented. The results show that the optical sensor technique may be used in the damage evaluation of an aircraft.

An Open-Loop Test of a Resonator Fiber Optic Gyro

The resonator fiber optic gyro （R-FOG） ,which utilizes a resonance frequency change due to the Sagnac effect,is a promising candidate for the next generation inertial rotation sensor. In this study, an open-loop R-FOG is set up using phase modulation spectroscopy. First,the demodulation curve is obtained using a lock-in amplifier. From the demodulation signal,a gyro dynamic range of ± 4.2rad/s is obtained. Then,using different phase modulation frequencies,the open-loop gyro output signal is measured when the gyro is rotated clockwise or counterclockwise. The bias drift as a function of time is also measured. The fluctuation of the output over 5s is about 0.02rad/s. The drift can be reduced by taking countermeasures against system noise.

FIBER OPTIC TEMPERATURE MEASURING SYSTEM

This paper presents a fiber optic temperature measuring system used for measuring the temperature in many occasions. The system is of reflective type and composed of thermostatic bimetal plate, lever piston framework, optical grating and optical fiber probes. When the temperature changes, the thermostatic bimetal plate deforms. Through lever piston framework, the optical grating produces displacement in the upright direction. Thus the change of the temperature is transformed into the upright displacement of the optical grating. Optical fiber probes are used for detecting the number of streak lines of the optical grating′s displacement depending on the change of temperature. The detected signal can be transmitted to the control center through optical fiber cable up to distance of 1 km. The measurable range of this system reaches 100℃ with accuracy of ±0.2℃.

A Self-Referenced Fiber-Optic Refractive Index Sensor for Cure Monitoring of Epoxy Composites

A self referenced fiber optic refractive index sensor is developed to measure quantitative cure extent of epoxy. In case the sensor is applied to in situ cure monitoring of epoxy composites, each sensor embedded in different location within the structure is self referenced and can be normalized to a common scale. Therefore, the real time comparative of each sensor’s output becomes possible and variations in the extent of cure at different locations can be monitored. The developed sensor was used to monitor the isothermal cure of an epoxy system. The output of the sensor was compared with the results of the differential scanning calorimetry (DSC). The self referencing function of the sensor is confirmed.

Numerical Simulation and Analysis of Bipolar Junction Photogate Transistor for CMOS Image Sensor

A new photodetector--bipolar junction photogate transistor is presented for CMOS image sensor and its analytical model is also established.With the technical parameter of the 0.6μm CMOS process,the bipolar junction photogate transistor is analyzed and simulated.The simulated results illustrate that the bipolar junction photogate transistor has the similar characteristics of the traditional photogate transistor.The photocurrent density of the bipolar junction photogate transistor increases exponentially with the incidence light power due to introducing the injection p+n junction.Its characteristic of blue response is rather improved compared to the traditional photogate transistor that benefits to increase the color photograph made up of the red,the green,and the blue.

Affinity and fluorescent detection of surfactants/ssDNA and single-walled carbon nanotube

A new biosensor platform was explored for detection of surfactant based on fluorescence changes from single strand DNA （ssDNA） and single-walled carbon nanotubes （SWNTs）. Thermodynamics assay was performed to value the stability of probe. The affinities of SWNT to five common surfactants （SDS, DBS, Triton X-100, Tween-20 and Tween-80） were investigated by real-time fluorescence method. The effects of Mg^2＋ and pH on the fluorescence intensity of self-assembled quenched sensor were performed. The fluorescent emission spectra were used to measure the responses of self-assembled quenched fluorescent of ssDNA/SWNTs to different concentration surfactant（Triton X-100）. The FAM-DNA wrapped SWNTs probe was stable in a wide temperature range （5 ℃ to 80℃）. The binding strength of surfactants and single-stranded DNA （ssDNA） on SWNTs surfaces was shown as follows： Triton X-100〉DBS〉Tween-20〉Tween-80〉ssDNA〉SDS, and the optimized reaction conditions included pH 7.4 and 10 mmol/L Mg2＋. The fluorescence of FAM-ssDNA wrapped SWNTs was proportionally recovered as a result of adding different concentrations of Triton X- 100, which realizes the quantitative detection of Triton X- 100.

Research on stress characteristics of Fabry-Perot sensor with center microbubble structure

The optical fiber based on silicon materials has a smaller thermal expansion coefficient, therefore it can be used for the preparation of sensor devices which are insensitive to temperature but sensitive to refractive index, strain, stress, etc. For example, we can use optical fiber Fabry-Perot （F-P） sensor to achieve high sensitivity stress sensing. In this paper, we design an optical fiber F-P sensor with low cost and high sensitivity based on chemical etching method and analyze the stress sensing properties. Hydrofluoric acid is used to prepare the end face concave hole of the optical fiber first, and then the hollow struc-ture of the fiber F-P sensor is obtained by melting and discharge. This preparation method contributes greatly to enhancing the stress sensing properties and temperature insensitivity of the optical fiber device. The experimental results show that interference spectrum peak change is proportional to the stress change of optical fiber F-P sensor, stress sensitivity can reach 5. 2, and the cost is relatively low. Based on this,it has a certain application value in the stress sensing field.

TDDFT Study on Different Sensing Mechanisms of Similar Cyanide Sensors Based on Michael Addition Reaction

The solvents and substituents of two similar fluorescent sensors for cyanide, 7-diethylamino- 3-formylcoumarin （sensor a） and 7-diethylamino-3-（2-nitrovinyl）coumarin （sensor b）, are proposed to account for their distinct sensing mechanisms and experimental phenomena. The time-dependent density functional theory has been applied to investigate the ground states and the first singlet excited electronic states of the sensor as well as their possible Michael reaction products with cyanide, with a view to monitoring their geometries and photophysieal properties. The theoretical study indicates that the protic water solvent could lead to final Michael addition product of sensor a in the ground state, while the aprotic acetonitrile solvent could lead to carbanion as the final product of sensor b. Furthermore, the Michael reaction product of sensor a has been proved to have a torsion structure in its first singlet excited state. Correspondingly, sensor b also has a torsion structure around the nitrovinyl moiety in its first singlet excited state, while not in its carbanion structure. This could explain the observed strong fluorescence for sensor a and the quenching fluorescence for the sensor b upon the addition of the cyanide anions in the relevant sensing mechanisms.

Monitoring and Warning of Landslides and Debris Flows Using an Optical Fiber Sensor Technology

Landslides and debris flows are typical geo-hazards which occur in hilly or mountainous regions. Debris flows may result from landslides. Geotechnical instrumentation plays an important role in monitoring and warning of landslides and resulted debris flows. Traditional technologies for monitoring landslides and debris flows have certain limitations. The new optical fiber sensors presented in this paper can overcome those limitations. This paper presents two new optical fiber sensor systems: one is the Fiber Bragg Grating (FBG)-based in-place inclinometer for monitoring landslides and the other is the FBG-based column-net system for monitoring debris flows. This paper presents the calibration results of FBG-based in-place inclinometers in laboratory. It is found that the calibration results are in good agreement with theoretical results. Both the FBG-based in-place inclinometers and the FBG-based column-net system have been installed at a site in Weijiagou valley, Beichuan County, Sichuan Province of China. Some preliminary results have been obtained and reported in the paper. The advantages of the FBG monitoring systems and their potential applications are also presented.

Two Rhodamine-based Turn on Chemosensors with High Sensitivity, Selectivity, and Naked-Eye Detection for Hg^2＋

Two novel rhodamine-based fluorescence enhanced molecular probes （RA1 and RA2） were synthesized, which were both designed as comparative fiuoroionophore and chromophore for the optical detection of Hg^2＋. The recognizing behaviors were investigated both experimentally and computationally. They exhibited high selectivity and sensitivity for Hg^2＋ over other commonly coexistent metal ions in CH3CN/H2O （1：1, V/V） solution. Test shows that hydroxy benzene of rich electron was beneficial to the chelate of Hg^2＋ with sensors. The detection limit was measured to be at least 0.14 p.mol/L. After addition of Hg^2＋, the color changed from colourless to pink, which was easily and hydrogel sensor. detected by the naked eye in both solution

A novel temperature-insensitive strain sensor based on tapered fiber grating

A novel temperature-insensitive strain sensor based on bandwidth demodulation of the reflected light from the tapered fiber grating is presented, which is simple and low-cost and has considerable potential particularly application for strain sensing,and with the development of the interrogation system, it can demodulate both the bandwidth and the center wavelength of the reflected light from TFG to measure strain and temperature simultaneously.

Study of a high-temperature and high-pressure FBG sensor with Al_2O_3 thin-wall tube substrate

A fiber Bragg grating(FBG) high-temperature and high pressure sensor has been designed and fabricated by using the Al2O3 thin-wall tube as a substrate.The test results show that the sensor can withstand a pressure range of 0-45 MPa and a temperature range of -10-300 ℃,and has a pressure sensitivity of 0.0426 nm/MPa and a temperature sensitivity of 0.0112 nm /