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Performance Evaluation of Innovative Ion-Sensitive Field Effect Diode for pH Sensing
摘要： In this paper, we have successfully introduced and characterized an innovative ion sensitive device called “Ion sensitive field effect diode”, a completely new ion-sensitive sensor. In conventional ion-sensitive devices, electrolyte/insulator interface reactions produce a conductive channel between the drain and the source whereas in our proposed structure, a p-n junction forms and is responsible for the conductivity. Since it is for the first time that such device is proposed as an ion sensor, comprehensive characterizations have been performed based on our previously TCAD-based model which was developed to simulate electrolyte and electrolyte/insulator interface. Considering this reliable model, sensing parameters of pH sensors such as sensitivity and signal to noise ratio are investigated and evaluated. Meanwhile, an accurate model to approximate the noise behavior of the device is proposed. Moreover, the effect of Silicon active layer thickness and doping concentration on the sensitivity of the device have been studied. Results reveal that ion sensitive field effect diode can achieve sensitivity about 5 times higher than the Nernst limit and can be considered as a promising candidate toward accurate and more sensitive ion sensors and this new type of sensor deserves further attention and development.
关键词： pH sensor,Detection Limit,TCAD-based model,Ion Sensitive Field Effect Diode,Electrolyte/insulator interface
更新于2025-09-23 15:21:01
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A chemically modified laser-induced porous graphene based flexible and ultrasensitive electrochemical biosensor for sweat glucose detection
摘要： Porous laser-induced graphene (LIG) is an attractive and promising carbon material for electrochemical applications because it can immobilize various proteins, such as enzymes, antibodies, and receptors. However, poor inherent electrical properties caused by low surface conductivity is still a critical drawback for various applications. Here, we have proposed a surface modification method for the LIG electrode using acetic acid treatment via facile and practicable dipping technique. This simple acetic acid treatment dramatically increased the ratio of carbon-carbon bonds which effectively increased conductivity and decreased sheet resistance. Importantly, these unique properties also facilitated the stable and uniform dispersion of highly catalytic Pt nanoparticles (PtNPs) on LIG by avoiding the concentration of electric field on nanoparticles that can cause aggregation during electrodeposition. Finally, chitosan-glucose oxidase (GOx) composite was successfully immobilized onto the LIG/PtNPs electrode to fabricate a sweat glucose biosensor. The as-prepared LIG/PtNPs electrode exhibited a high sensitivity of 4.622 μA/mM as well as an ultra-low limit of detection (signal to noise ratio is 3) which was less than 300 nM and dynamic linear range up to 2.1 mM. Furthermore, we tested the variation of blood glucose level before and after meal using the amperometric response of the sensor which demonstrates the commercial potential of this unique sweat glucose biosensor.
关键词： Sweat glucose detection,Laser-induced graphene (LIG),Acetic acid treatment,Ultra-sensitive and -low detection limit,Electrochemical biosensor
更新于2025-09-23 15:19:57
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Concentric multipass cell enhanced double-pulse laser-induced breakdown spectroscopy for sensitive elemental analysis
摘要： Although double-pulse laser-induced breakdown spectroscopy (DP-LIBS) is regarded as a promising technique in trace element analysis, its limit of detection (LOD) is not sufficient for some applications. The enhancement of spectral signal is the key to further improve the sensitivity of DP-LIBS. To further increase the sensitivity of DP-LIBS, a concentric multipass cell (CMC) enhanced DP-LIBS (CMC-DP-LIBS) technique is proposed for the first time, which makes full use of the energy of reheating laser by multi-reflection in CMC to enhance the spectral signal and lower LOD. 2.3 times signal enhancement of Mn I 403.08 nm line and 2.3 times decrease of LOD of Mn on the surface of zinc bulk compared with traditional orthogonal reheating DP-LIBS were attained. The signal enhancement factor can reach to 3.6 theoretically with the increase of reflectivity and the sizes of mirrors of CMC. This CMC-DP-LIBS provides a new approach to further improve the sensitivity of DP-LIBS and promotes its application in trace element detection.
关键词： Double-pulse,Concentric multipass cell enhancement,Laser-induced breakdown spectroscopy,Detection limit
更新于2025-09-23 15:19:57
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A fluorometric aptasensor for bisphenol a based on the inner filter effect of gold nanoparticles on the fluorescence of nitrogen-doped carbon dots
摘要： An aptamer-based fluorometric assay is described for the determination of bisphenol A (BPA). The aptamer against BPA is first attached to the surface of the red AuNPs, and this prevents the AuNPs from salt-induced formation of a blue-colored aggregate. Hence, the blue fluorescence of added nitrogen-doped carbon dots (NCDots) is quenched via an inner filter effect (IFE) caused by the red AuNPs. After addition of BPA, the BPA/aptamer complex is formed, and the AuNPs are no longer stabilized agains aggregation. This weakens the IFE and results in the recovery of the fluorescence of the NCDots which is measured best at excitation/emission wavelengths of 300/420 nm. The recovered fluorescence increases linearly in the 10 to 250 nM and 250 to 900 nM BPA concentration ranges, and the detection limit is 3.3 nM. The method was successfully applied to the determination of BPA in spiked environmental tap water samples.
关键词： Wide linear range,Quick response,Salt-induced aggregation,Tap water,Low detection limit,BPA/aptamer complexes,Aggregated AuNPs,Environmental-friendly,Fluorescence quenched,Fluorescence recovery
更新于2025-09-23 15:19:57
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Microsecond Resolved Infrared Spectroelectrochemistry Using Dual Frequency Comb IR Lasers
摘要： A dual infrared frequency comb spectrometer with heterodyne detection has been used to perform time resolved electrochemical attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The measurement of the potential dependent desorption of a monolayer of a pyridine derivative (4-dimethylaminopyridine, DMAP) with time resolution as high as 4 μs was achieved without the use of step-scan interferometry. An analysis of the detection limit of the method as a function of both time resolution and measurement co-additions is provided and compared to step-scan experiments of an equivalent system. Dual frequency comb spectroscopy is shown to be highly amenable to time-resolved ATR-SEIRAS. Microsecond resolved spectra can be obtained with high spectral resolution and fractional monolayer detection limits in a total experimental duration that is two orders of magnitude less than the equivalent step-scan experiment.
关键词： 4-dimethyamino pyridine (DMAP),noise analysis,Dual frequency comb spectroscopy,time resolved spectroelectrochemistry,RC constant,attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS),detection limit
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Research on Laser Cavity Ring-down Spectroscopy and Fiber-Based Measurement for SF6 Decomposed Gases
摘要： The four species gases including H2S, CO, HF and SO2 in the decomposition gas of SF6 were monitored online, according to the power industry requirements. The calibration technology and the algorithm, the optical path of cavity and signal to noise ratio of detection circuit are the key steps in the development of decomposed gas monitoring device. This paper first introduces the calibration method and technology of multi-component trace gas analysis instrument based on photo-acoustic spectroscopy. An on-line monitoring device for SF6 decomposition gas based on laser absorption spectroscopy is developed. The calibration algorithm is proposed and verified by experiment. Within the range of 0~200ppm, the stability is less than 2%. The concentration calibration method proposed in this paper can effectively monitor the concentration of H2S, CO, HF, SO2 typical characteristic gases, and provide theoretical technical guidance for SF6 gas insulated and high-voltage combined electrical apparatus.
关键词： cavity design,detection limit,SF6 decomposition gases,cavity ring-down spectroscopy
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Lossy Mode Resonance Fiber-Optic Biosensing Allowing Ultra-Low Detection Limit
摘要： Fiber-optic biosensors can offer great advantages over other optical technology platforms thanks to the typical features of optical fibers. Moreover, the opportunity of depositing nm-thick overlays on optical fibers with a high degree of accuracy, repeatability and reproducibility has enabled spreading the application domains of this technology. Recently, the concept of guided mode resonance has been exploited in thin film coated fiber-optic sensors, under the name of lossy mode resonance (LMR). LMR occurs when the real part of the thin film permittivity is positive and greater in magnitude than both its own imaginary part and the permittivity of the material surrounding the thin film. Therefore, metallic oxides and polymers can be used to generate LMRs, instead of the noble metals typically used in SPR devices. Instead of using multi-mode fibers, D-shaped single-mode fibers have been used to excite LMR, which enables tracking the spectral displacement of the 1st LMR, the most sensitive LMR, at wavelengths in the NIR, where the sensitivity is enhanced if compared to the visible region. By coating the D-shaped region of the fiber with a nanometric layer of tin oxide (SnO2) and integrating it into an ad-hoc microfluidic system, an ultra-low detection limit (LOD) biosensing device has been developed. The sensing principle is quite simple: when the target analyte interacts with the fiber-functionalized surface, this induces a change in the optical properties of the overlay (i.e. effective refractive index and thickness); in turn, this causes a change in the spectral position of the LMR that can be accurately and precisely measured through a conventional wavelength interrogation system. The deposition of the tin oxide layer (roughly 160-180 nm), which is performed with a DC sputter machine (ND-SCS200, Nadetech S.L.), has been characterized by FESEM images (UltraPlus Carl Zeiss Inc.). The round inset of the same figure details the functionalization of the sensitive region, which is carried out with the deposition of a nm-thick polymeric layer of poly(methyl-methacrylate) (Eudragit L100) that provides free functionalities necessary for the IgG antibody immobilization. The assay has been completed by spiking increasing concentrations of anti-IgG antigen (from 1 pg mL-1 up to 10 μg mL-1) in a real sample of CRP-free human serum. The real-time tracking of the LMR shift has enabled following all the biochemical steps during the assay implementation and then the calibration curve (n=4) of the proposed biosensor has been obtained, together with the sigmoidal fit with the Hill function, which is a well-accepted mathematical model used to quantify the degree of interaction between ligand binding sites. A LOD of 150 fg mL-1 has been attained. This result has confirmed a big leap in performance thanks to the capability to detect analyte concentrations down to few fM in real samples, enhancing the LOD by three orders of magnitude when compared with other fiber-based configurations and matching a LOD comparable with the most outstanding optical technology platforms.
关键词： Fiber-optic biosensors,lossy mode resonance,microfluidic system,ultra-low detection limit,tin oxide
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 15th International Conference on Group IV Photonics (GFP) - Cancun (2018.8.29-2018.8.31)] 2018 IEEE 15th International Conference on Group IV Photonics (GFP) - System-Level Integrated Active Silicon Photonic Biosensor for Detecting Small Molecule Interactions
摘要： We present a system-level integration of active silicon photonic biosensors. With on-chip photodetectors, sensors are characterized in the photovoltaic mode. A biotin-avidin affinity assay is employed to exemplify the detection of small molecule interactions, showing a detection limit in the order of 10?5 M.
关键词： photovoltaic mode,small molecule interactions,detection limit,silicon photonic biosensors,biotin-avidin affinity assay
更新于2025-09-04 15:30:14