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Sensitivity comparison of graphene based surface plasmon resonance biosensor with Au, Ag and Cu in the visible region
摘要： In this paper, the sensitivities of graphene based surface plasmon resonance (SPR) biosensors with gold (Au), silver (Ag) and copper (Cu) layers are numerically analyzed and compared in the visible region. As the wavelength of the incident light increases, the sensitivity of a monolayer graphene based SPR biosensor with a specific metal (Au, Ag or Cu) layer firstly increases to a maximum value (called peak sensitivity), and then decreases. It is found that the peak sensitivity of a monolayer graphene based SPR biosensor with Ag layer (300.26 °/RIU) is 119% or 200% higher than the one of SPR biosensor with Au (137.02 °/RIU) or Cu (136.24 °/RIU) layer. In addition, with the increase of number of graphene layers, the peak sensitivity of the proposed SPR sensor with different metal layer decreases, but the resonance wavelength increases. Moreover, the origin of sensitivity enhancement is also investigated by analyzing the electric field intensity inside the proposed SPR biosensors. It is believed that a sensitivity comparison of graphene based SPR biosensors with Au, Ag and Cu layer is important and can be helpful for highly sensitive biosensors development.
关键词： graphene,surface plasmon resonance,biosensor,visible region,sensitivity
更新于2025-09-19 17:15:36
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Principles for Sensitive and Robust Biomolecular Interaction Analysis: The Limits of Detection and Resolution of Diffraction-Limited Focal Molography
摘要： Label-free biosensors enable the monitoring of biomolecular interactions in real time, which is key to the analysis of the binding characteristics of biomolecules. While refractometric optical biosensors such as surface plasmon resonance (SPR) are sensitive and well-established, they are susceptible to any change of the refractive index in the sensing volume caused by minute variations in composition of the sample buffer, temperature drifts, and most importantly nonspecific binding to the sensor surface in complex fluids such as blood. The limitations arise because refractometric sensors measure the refractive index of the entire sensing volume. Conversely, diffractometric biosensors–for example, focal molography–only detect the diffracted light from a coherent assembly of analyte molecules. Thus any refractive index distribution that is noncoherent with respect to this molecular assembly does not add to the coherent signal. This makes diffractometric biosensors inherently robust and enables sensitive measurements without reference channels or temperature stabilization. The coherent assembly is generated by selective binding of the analyte molecules to a synthetic binding pattern–the mologram. Focal molography has been introduced theoretically [C. Fattinger, Phys. Rev. X 4, 031024 (2014)] and verified experimentally [V. Gatterdam, A. Frutiger, K.-P. Stengele, D. Heindl, T. Lübbes, J. V?r?s, and C. Fattinger, Nat. Nanotechnol. 12, 1089 (2017)] in previous papers. However, further understanding of the underlying physics and a diffraction-limited readout is needed to unveil its full potential. This paper introduces refined theoretical models, which can accurately quantify the amount of biological matter bound to the mologram from the diffracted intensity. In addition, it presents measurements of diffraction-limited molographic foci, i.e., Airy discs. These improvements enable us to demonstrate a resolution in real-time binding experiments comparable to the best SPR sensors without the need for temperature stabilization or drift correction and to detect low-molecular-weight compounds label free in an endpoint format. The presented experiments exemplify the robustness and sensitivity of the diffractometric sensor principle.
关键词： biomolecular interaction analysis,diffractometric biosensors,focal molography,diffraction-limited foci,robustness,label-free detection,sensitivity
更新于2025-09-19 17:15:36
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Investigation of sensitivity enhancing and temperature compensation for fiber Bragg grating (FBG)-based strain sensor
摘要： This paper developed a novel method and relevant mechanical configurations to enhance strain sensitivity and realize temperature compensation simultaneously for fiber Bragg grating (FBG)-based strain sensor. The theoretical strain amplification model and temperature compensation model of the designed method and the manufactured sensor specimen were derived based on the theory of elastic mechanics and the methodology of matrices. The established theoretical sensing models were validated through finite element method (FEM) and experimental tests. The theoretical, FEM, and experimental results show good consistency. The overall sensitivities of the two FBGs in the developed sensor achieve 7.72 pm/με and ?2.94 pm/με respectively, which are respectively 6.43 and ?2.45 times of the strain sensitivity of a bare fiber Bragg grating strain sensor. The decoupling of strain and temperature was implemented theoretically and verified experimentally. The developed sensor in this paper can be used for long-term small-amplitude micro-strain monitoring in varying temperature environments for vital mechanical equipment.
关键词： Strain,Lever structure,Fiber Bragg grating,Sensitivity enhancement,Temperature compensation
更新于2025-09-19 17:15:36
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Tunable local surface plasmon resonance and refractive index sensitivity ability of three-layered dielectric-silver bimetallic nanoshells
摘要： Optical properties and refractive index sensitivity abilities of three-layered silver/gold-dielectric-silver bimetallic nanoshells are investigated based on quasi-static theory. The results show that absorption spectra of silver/gold-dielectric-silver bimetallic nanoshells can be well tuned by changing the inner core radius, middle dielectric radius and outer shell layer thickness. Local surface plasmon resonance (LSPR) shifts of |ω? ?? mode show a red-shift with increasing the inner core radius and the thickness of middle dielectric layer, while a blue-shift with increasing the thickness of outer shell. It is interesting to find that the shifts of |ω+ ?? mode are related to the ratio ε2∕ε4, the component of core and nanoshell. In addition, the refractive index sensitivity abilities of three-layered silver/gold-dielectric-silver bimetallic nanoshells are also reported. A higher refractive index sensitivity ability can be obtained by adjusting its geometric size and component. |ω? ?? mode gets more intensity with increasing the surrounding medium dielectric function, while |ω+ ?? mode fades down. The intensity difference between |ω? ?? mode and |ω+ ?? mode is mainly effected by the surrounding medium dielectric function, its geometric parameter, middle layer dielectric function, the component of core and nanoshell. Our study provides a way to analyze sensitivity application of nanoshells and broadens the application of nanoshells in sensor ability.
关键词： Plasmon hybridization theory,Local surface plasmon resonance (LSPR),Dielectric-silver bimetallic nanoshells,Refractive index sensitivity ability
更新于2025-09-19 17:15:36
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Interpretive Performance and Inter-Observer Agreement on Digital Mammography Test Sets
摘要： Objective: To evaluate the interpretive performance and inter-observer agreement on digital mammographs among radiologists and to investigate whether radiologist characteristics affect performance and agreement. Materials and Methods: The test sets consisted of full-field digital mammograms and contained 12 cancer cases among 1000 total cases. Twelve radiologists independently interpreted all mammograms. Performance indicators included the recall rate, cancer detection rate (CDR), positive predictive value (PPV), sensitivity, specificity, false positive rate (FPR), and area under the receiver operating characteristic curve (AUC). Inter-radiologist agreement was measured. The reporting radiologist characteristics included number of years of experience interpreting mammography, fellowship training in breast imaging, and annual volume of mammography interpretation. Results: The mean and range of interpretive performance were as follows: recall rate, 7.5% (3.3–10.2%); CDR, 10.6 (8.0–12.0 per 1000 examinations); PPV, 15.9% (8.8–33.3%); sensitivity, 88.2% (66.7–100%); specificity, 93.5% (90.6–97.8%); FPR, 6.5% (2.2–9.4%); and AUC, 0.93 (0.82–0.99). Radiologists who annually interpreted more than 3000 screening mammograms tended to exhibit higher CDRs and sensitivities than those who interpreted fewer than 3000 mammograms (p = 0.064). The inter-radiologist agreement showed a percent agreement of 77.2–88.8% and a kappa value of 0.27–0.34. Radiologist characteristics did not affect agreement. Conclusion: The interpretative performance of the radiologists fulfilled the mammography screening goal of the American College of Radiology, although there was inter-observer variability. Radiologists who interpreted more than 3000 screening mammograms annually tended to perform better than radiologists who did not.
关键词： Screening,Sensitivity and specificity,Observer variation,Radiologists,Medical audit
更新于2025-09-19 17:15:36
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Characterization and NO2 gas sensing performance of CdO:In2O3 polycrystalline thin films prepared by spray pyrolysis technique
摘要： Polycrystalline CdO:In2O3 thin films for gas sensor applications were prepared on glass and silicon substrates by using one-step spray pyrolysis technique from the aqueous solution of CdCl2 and InCl3 at a substrate temperature of 300 °C. The structure, surface morphology, and the optoelectronic properties of prepared films were characterized respectively by means of X-ray diffraction (XRD), atomic force microscope and UV–visible spectroscopy. Based on the XRD results, the polycrystalline nature of CdO films has been confirmed, and In2O3 films were found to exhibit a preferred orientation along (222) diffracted plane. The grain size varies between 9.0 and 28.4 nm. The results of Hall effect measurement of CdO:In2O3 thin films confirms that all films were an n-type semiconductor. The electrical properties of prepared thin films and their sensitivity to nitrogen dioxide (NO2) gas are also studied. The influence of the operating temperature and In2O3 concentration on the NO2 response were investigated. It is found that all films are sensitive to NO2 gas, and the ideal operating temperature for the film contented 20 vol% of In2O3 was found to be 200 °C at a gas concentration of 25 ppm. The sensing mechanism of the CdO:In2O3 thin film is discussed and attributed to electron transfer between the sensing element and NO2 molecules.
关键词： NO2 gas sensor,Sensitivity,Optoelectronic properties,Structural,Morphology,Metal-oxide semiconductors
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Singapore, Singapore (2018.4.22-2018.4.26)] 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Novel Mechanical Coupling Piezoelectric Micromachined Ultrasonic Transducers Based on Base Excitation System
摘要： This paper presented a novel piezoelectric micromachined ultrasonic transducer (PMUT) based on mechanical coupling between an annular diaphragm and a circular diaphragm stacking together. The circular diaphragm whose pedestal grounded on the middle of the annular diaphragm, which formed a base excitation system. Compared to the non-coupled traditional circular diaphragm PMUTs, the proposed PMUTs achieved higher transmission sensitivity by 173% with the resonant frequency of 6.14 MHz in water, due to the base excitation amplification of the circular diaphragm. Also, the array transmission performance of the proposed PMUT and non-coupled traditional PMUT with circular diaphragm was compared in the same array dimension. The results indicated that the array composed by the proposed PMUT had less cross-talk effect, which kept the central working frequency almost the same when it work solely.
关键词： mechanical coupling,PMUT,high transmission sensitivity,low cross-talk effect
更新于2025-09-19 17:15:36
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Enhanced sensitivity of distributed-temperature sensor with Al-coated fiber based on OFDR
摘要： In this paper, we present a distributed-optical fiber temperature sensor with enhanced sensitivity with Al coating using the Rayleigh backscattering (RBS) spectrum shift measured via optical frequency-domain reflectometry (OFDR). The Al-coated sensing fiber having a larger thermal expansion coefficient than that of silica produces a strain-coupled shift in the RBS under an increase in temperature. This effect leads to an enhanced temperature sensitivity of the distributed measurement scheme. In order to analyze the principle of temperature sensitivity enhancement, a simple analysis was performed by considering the fiber directional strain and force equilibrium between the optical fiber and Al-coated layer. Our results revealed that the temperature sensitivity achieved with the Al-coated fiber in OFDR was ～56% higher relative to that of a single-mode fiber.
关键词： Al-coated fiber,Distributed sensor,Thermal expansion,Optical frequency-domain reflectometry,Temperature sensitivity
更新于2025-09-19 17:15:36
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Measuring the Contrast Sensitivity Function Using the qCSF Method With 10 Digits
摘要： Purpose: The Bayesian adaptive quick contrast sensitivity function (qCSF) method with a 10-letter identification task provides an efficient CSF assessment. However, large populations are unfamiliar with letters and cannot benefit from this test. To overcome the barrier, we conducted this study. Method: A new font for digits (0~9) was created. The digits were then filtered with a raised cosine filter, rescaled to different sizes to cover spatial frequencies from 0.5 to 16 cycles per degree (cpd), and used as stimuli in a 10-alternative forced choice (10AFC) digit identification task. With the 10AFC digit identification task, the CSFs of five young and five old observers were measured using the qCSF and Psi methods. The estimates from the latter served as reference. Results: The new digit font showed significantly improved similarity structure, Levene’s test, F(1, 88) ? 6.36, P ? 0.014. With the 10-digit identification task, the CSFs obtained with the qCSF method matched well with those obtained with the Psi method (root mean square error [RMSE] ? 0.053 log10 units). With approximately 30 trials, the precision of the qCSF method reached 0.1 log10 units. With approximately 75 trials, the precision of the CSFs obtained with the qCSF was comparable to that of the CSFs measured by the Psi method in 150 trials. Conclusions: The qCSF with the 10 digit identification task is validated for both young and old observers. Translational Relevance: The qCSF method with the 10-digit identification task provides an efficient and precise CSF test especially for people who are unfamiliar with letters.
关键词： contrast sensitivity function,precision,Bayesian adaptive procedure,qCSF,Sloan digit
更新于2025-09-19 17:15:36
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Synthesis and Properties of Highly Sensitive Ether Ring Fused <i>O</i>-Acyloxime Esters as Photoradical Initiator
摘要： High sensitivity of O-acyloxime ester, which is widely used as a photo radical polymerization initiator for color resist, was investigated. Introduction of an ether ring structure to the periphery of oxime was aimed at increasing rigidity of dye scaffold. As a result, the absorption spectrum at i-line (365 nm) became sharp, the absorption efficiency was greatly improved, and the sensitivity was increased by about five times as much as conventional linear type oximes by improving the radical generation quantum yield.
关键词： Photoradical initiator,i-Line,High sensitivity,Radical curing reaction,Ether ring-fused structure,Carbazole dye,O-Acyloxime ester
更新于2025-09-19 17:15:36