scholarly journals A Facile Strategy for the Ion Current and Fluorescence Dual-Lock in Detection: Naphthalic Anhydride Azide (NAA)-Modified Biomimetic Nanochannel Sensor towards H2S

Chemosensors ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 298
Author(s):  
I Wu ◽  
Dan Zhang ◽  
Xuanjun Zhang
Keyword(s):  
High Sensitivity ◽  
Ion Current ◽  
Electric Signal ◽  
Detection Accuracy ◽  
Covalent Bonds ◽  
Naphthalic Anhydride ◽  
New Ideas ◽  
Temporal And Spatial ◽  
Lock In ◽  
Biological Channels

Inspired by biological channels, the electric signal-based artificial nanochannel system exhibits high sensitivity in various analyses. However, ion current may be affected by many other factors, leading to false-positive signals. For reliable detection, in this work, we apply a facile strategy to combine both current signal and fluorescence. Fluorescent probes were conjugated to the nanochannel surface by covalent bonds. By utilizing the specific reduction of azide groups in the probe to amino groups by H2S, a synchronizing change in fluorescence and nanochannel surface charge was established. As a result, both transmembrane ion current and fluorescence intensity showed significant changes. The photoelectric double-checked locking from temporal and spatial variation validly confirmed the response process and protected detection accuracy. The work may provide new ideas for the development of more sophisticated current and fluorescence dual-index nanochannel systems.

Small Molecule Permeation Across Membrane Channels: Chemical Modification to Quantify Transport Across OmpF

2018 ◽  
Author(s):  
Jiajun Wang ◽  
Jayesh Arun Bafna ◽  
Satya Prathyusha Bhamidimarri ◽  
Mathias Winterhalter
Keyword(s):  
Dwell Time ◽  
Covalent Binding ◽  
Channel Structure ◽  
Ion Current ◽  
E Coli ◽  
Current Fluctuation ◽  
Wide Range ◽  
Outer Membrane Channel ◽  
Biological Channels ◽  
Constriction Region

Biological channels facilitate the exchange of small molecules across membranes, but surprisingly there is a lack of general tools for the identification and quantification of transport (i.e., translocation and binding). Analyzing the ion current fluctuation of a typical channel with its constriction region in the middle does not allow a direct conclusion on successful transport. For this, we created an additional barrier acting as a molecular counter at the exit of the channel. To identify permeation, we mainly read the molecule residence time in the channel lumen as the indicator whether the molecule reached the exit of the channel. As an example, here we use the well-studied porin, OmpF, an outer membrane channel from <i>E. coli</i>. Inspection of the channel structure suggests that aspartic acid at position 181 is located below the constriction region (CR) and we subsequently mutated this residue to cysteine, where else cysteine free and functionalized it by covalent binding with 2-sulfonatoethyl methanethiosulfonate (MTSES) or the larger glutathione (GLT) blockers. Using the dwell time as the signal for transport, we found that both mono-arginine and tri-arginine permeation process is prolonged by 20% and 50% respectively through OmpF<sub>E181C</sub>MTSES, while the larger sized blocker modification OmpF<sub>E181C</sub>GLT drastically decreased the permeation of mono-arginine by 9-fold and even blocked the pathway of the tri-arginine. In case of the hepta-arginine as substrate, both chemical modifications led to an identical ‘blocked’ pattern observed by the dwell time of ion current fluctuation of the OmpF<sub>wt</sub>. As an instance for antibiotic permeation, we analyzed norfloxacin, a fluoroquinolone antimicrobial agent. The modulation of the interaction dwell time suggests possible successful permeation of norfloxacin across OmpF<sub>wt</sub>. This approach may discriminate blockages from translocation events for a wide range of substrates. A potential application could be screening for scaffolds to improve the permeability of antibiotics.

Covalent Organic Frameworks for Electrochemical Sensors: Recent Research and Future Prospects

2021 ◽  
Vol 17 ◽  
Author(s):  
Linyu Wang ◽  
Shasha Hong ◽  
Yuxi Yang ◽  
Yonghai Song ◽  
Li Wang
Keyword(s):  
Specific Surface ◽  
Electrochemical Sensors ◽  
Gas Adsorption ◽  
Low Cost ◽  
High Sensitivity ◽  
Crystalline Polymer ◽  
Synthesis Methods ◽  
High Porosity ◽  
Covalent Organic Frameworks ◽  
Covalent Bonds

Background: In recent years, electrochemical sensors are widely preferred because of their high sensitivity, rapid response, low cost and easy miniaturization. Covalent organic frameworks (COFs), a porous crystalline polymer formed by organic units connected by covalent bonds, have been widely used in gas adsorption and separation, drug transportation, energy storage, photoelectric catalysis, electrochemistry and other aspects due to their large specific surface, excellent stability, high inherent porosity, good crystallinity as well as structural and functional controllability. The topological structure of COFs can be designed in advance, the structural units and linkage are diversified, and the structure is easy to be functionalized, which are all beneficial to their application in electrochemical sensors. Methods: The types, synthesis methods, properties of covalent organic frameworks and some examples of using covalent organic frameworks in electrochemical sensors are reviewed. Results: Due to their characteristics of a large specific surface, high porosity, orderly channel and periodically arranged π electron cloud, COFs are often used to immobilize metal nanoparticles, aptamers or other materials to achieve the purpose of building electrochemical sensors with high sensitivity and good stability. Since the structure of COFs can be predicted, different organic units can build COFs with different structures and properties. Therefore, organic units with certain functional groups can be selected to build COFs with certain properties and used directly for electrochemical sensors. Conclusion: COFs have a good application prospect in electrochemical sensors.

The Application of Signal Processing Techniques in Improving Spectrometer Detection Limit

2011 ◽  
Vol 148-149 ◽  
pp. 1045-1050
Author(s):  
Zhi Ying Wu ◽  
Yi Zhang ◽  
Zuo Yuan Shen
Keyword(s):  
Signal Processing ◽  
Detection Limit ◽  
High Sensitivity ◽  
Processing Technique ◽  
Laser Source ◽  
Sampled Data ◽  
High Concentration ◽  
Signal Processing Technique ◽  
Processing Techniques ◽  
Lock In

Improving spectrometer detection limit using statistical principle and signal-processing technique are described simply in this work. In the detection of gas photoacoustic(PA) signal, accurate partitions of the sampled data affect on the detection limit to some extent although Lock-in amplification technique with high SNR and microphone sensor with high sensitivity have been used. A model and the resulting algorithm are proposed from PA-signal samples. The techniques are validated at ppb level on PA spectrometer for NH3 breath detection in high concentration of CO2 and H2O based on tunable erbium-doped fiber laser (TEDFL) or for multicomponent trace gas detection based on waveguide CO2 laser or on other laser source.

The Design of Sound and Light Controlled Corridor LED Lamp Based on Double Integration Detection

2013 ◽  
Vol 347-350 ◽  
pp. 93-97
Author(s):  
Xiu Lei Cui ◽  
Yong Gao Jin
Keyword(s):  
Power Consumption ◽  
Supply Voltage ◽  
High Sensitivity ◽  
Current Drive ◽  
Constant Current ◽  
Detection Accuracy ◽  
Double Integration ◽  
Detection Circuit ◽  
Micro Power ◽  
Operation Stability

The design of a high-sensitivity LED lamp with low standby consumption, sound and light controlled type based on the micro-power consumption characteristic of MK6A12P is presented in this paper. The standby power consumption is less than 0.07W. And the problem of the light sense unit influenced by the change of the supply voltage is solved by the design of double integration detection circuit, thereby, the detection accuracy of brightness is improved. The service life of LED lamp is greatly prolonged with constant current drive. It is proved by the experiment that the LED lamp has the advantages of simple circuit structure, high operation stability and high cost performance.

Theoretical Analysis and Basic Experiments for the 3D Displacement Measurement Using Ring-Shaped Laser Beam

2005 ◽  
Vol 295-296 ◽  
pp. 295-300
Author(s):  
S. Usuki ◽  
Kazuyuki Enami ◽  
M. Hiraki ◽  
S. Takahashi ◽  
Kiyoshi Takamasu
Keyword(s):  
Theoretical Analysis ◽  
Laser Beam ◽  
Optical System ◽  
High Sensitivity ◽  
Displacement Measurement ◽  
Contact Method ◽  
New Ideas ◽  
3D Positioning ◽  
The One ◽  
Basic Experiments

For flexible 3D positioning of a complex 3D mechanism, it is needed to measure 3D displacement of the end-effecter of the mechanism in high precision and by non-contact method. It was common to use plural sensors or scales together to measure the 3D displacement. However, it is difficult to calibrate the sensitivities of the plural sensors or scales. A novel 3D displacement measurement is proposed using an optical system in which lens focuses are collected at the center of the sphere, which has been used for the radius measurement of the sphere. Instead of facing in the XY direction that has high sensitivity, new ideas are necessary for the measurement in the Z direction of the optics where focuses are collected at the center of the sphere. The displacement in the XY direction and the one in the Z direction can be measured at the same time by using a ring-shaped laser beam instead of a simple ray.

Development of a Non-Contact Precision Measurement Technique Using Optical Frequency Combs

2012 ◽  
Vol 523-524 ◽  
pp. 877-882 ◽  
Author(s):  
Taro Onoe ◽  
Satoru Takahashi ◽  
Kiyoshi Takamasu ◽  
Hirokazu Matsumoto
Keyword(s):  
High Resolution ◽  
Frequency Comb ◽  
High Sensitivity ◽  
Distance Measurement ◽  
New Method ◽  
Optical Frequency ◽  
Optical Frequency Combs ◽  
High Frequencies ◽  
Frequency Combs ◽  
Lock In

We develop a new method for high-resolution and contactless distance measurement based on self frequency beats of optical frequency combs. We use two optical frequency comb lasers with Rb-stabilized repetition frequencies for doing accurate distance measurement. The repetition frequencies of the optical frequency combs are different, thus parts of the high frequencies such as several gigahertz of self beats are beat-downed to several megahertz without an RF frequency oscillator. The phases of the beat signals of several megahertz frequencies are measured by a lock-in amplifier with a high resolution and high sensitivity. The new method is applied to distance measurement for objects which have rough-surface in the distance range of several-meters.

The Optical Rotatory Dispersion and Linear Dichroism Option of the JASCO J-500 A-Type CD Spectropolarimeter

1989 ◽  
Vol 43 (8) ◽  
pp. 1471-1475 ◽  
Author(s):  
Yohji Shindo ◽  
Hiroshi Hayakawa ◽  
Masahiro Sudani
Keyword(s):  
Optical Axis ◽  
High Sensitivity ◽  
Linear Dichroism ◽  
Null Point ◽  
Optical Rotatory Dispersion ◽  
Polarization Modulation ◽  
Know How ◽  
Harmonic Rejection ◽  
Lock In ◽  
Point Detection

We have made an ORD option for our JASCO J-500 A-type CD spectrometer based on the know-how obtained from the studies of our new polarization-modulation spectrometer. The Mueller matrix approach is used to analyze and evaluate important factors determining the performance of our ORD option. These are (1) the harmonic rejection and “in band” overload capability of the lock-in amplifier, (2) the position of the analyzer's optical axis, (3) the residual static birefringence of the PEM. The capability of our ORD option is equal to that of commercially available ORD spectropolarimeters, in the range from 200 to 700 nm. Furthermore, our option has much faster speed for ORD measurements than does the ORD spectropolarimeter of the null-point detection type. Our ORD option can also be used to measure linear dichroism in high sensitivity.

scholarly journals Enhanced Sensitivity and Detection of Near-Infrared Refractive Index Sensor with Plasmonic Multilayers

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7056
Author(s):  
Tan Tai Nguyen ◽  
Nguyen Van Sau ◽  
Quang Minh Ngo ◽  
Gauthier Eppe ◽  
Ngoc Quyen Tran ◽  
...  
Keyword(s):  
Refractive Index ◽  
Near Infrared ◽  
High Sensitivity ◽  
Dielectric Films ◽  
Silver Layer ◽  
Refractive Index Sensor ◽  
Detection Accuracy ◽  
Spr Sensor ◽  
Enhanced Sensitivity ◽  
Sensor Sensitivity

In this work, the multilayer of the surface plasmon resonance (SPR) sensor was optimized to achieve the maximum sensor sensitivity. By optimizing the thickness of the silver layer (Ag) and dielectric films (TiO2 and AlAs), the optimum sensitivity of the SPR sensor could be obtained. The performance of the SPR sensor proposed was compared with control simulations utilizing zinc oxide (ZnO) and molybdenum oxide (MoO3). The numerical results indicate that the figure-of-merits (FOM) of the SPR sensor was achieved around 150/RIU, corresponding to the sensor sensitivity of 162.79°/RIU with the optimized thicknesses of the TiO2, Ag, and AlAs layers of 140 nm, 60 nm, and 25 nm, respectively. This refractive index sensor shows the FOM to have high detection accuracy and high sensitivity that lead to finding potential application in bio-chemical detection with a small volume of liquid used in biological diagnosis.

scholarly journals High-Sensitivity Biosensor Based on Glass Resonance PhC Cavities for Detection of Blood Component and Glucose Concentration in Human Urine

Coatings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1555
Author(s):  
Abduladheem Turki Jalil ◽  
Shameen Ashfaq ◽  
Dmitry Olegovich Bokov ◽  
Amer M. Alanazi ◽  
Kadda Hachem ◽  
...  
Keyword(s):  
Human Urine ◽  
Glucose Concentration ◽  
Free Spectral Range ◽  
High Sensitivity ◽  
Optical Biosensor ◽  
Optical Signal ◽  
Blood Component ◽  
Detection Accuracy ◽  
Worst Case ◽  
Detection Range

In this work, a novel structure of an all-optical biosensor based on glass resonance cavities with high detection accuracy and sensitivity in two-dimensional photon crystal is designed and simulated. The free spectral range in which the structure performs well is about FSR = 630 nm. This sensor measures the concentration of glucose in human urine. Analyses to determine the glucose concentration in urine for a normal range (0~15 mg/dL) and urine despite glucose concentrations of 0.625, 1.25, 2.5, 5 and 10 g/dL in the wavelength range 1.326404~1.326426 μm have been conducted. The detection range is RIU = 0.2 × 10−7. The average bandwidth of the output resonance wavelengths is 0.34 nm in the lowest case. In the worst case, the percentage of optical signal power transmission is 77% with an amplitude of 1.303241 and, in the best case, 100% with an amplitude of 1.326404. The overall dimensions of the biosensor are 102.6 µm2 and the sensitivity is equal to S = 1360.02 nm/RIU and the important parameter of the Figure of Merit (FOM) for the proposed biosensor structure is equal to FOM = 1320.23 RIU−1.

Measurement of quadratic electrogyration effect in KDP crystals for light propagating along the optical axis

2019 ◽  
Vol 52 (1) ◽  
pp. 158-167 ◽  
Author(s):  
Marek Izdebski
Keyword(s):  
Optical Axis ◽  
Potassium Dihydrogen Phosphate ◽  
High Sensitivity ◽  
Measurement Procedure ◽  
Measuring System ◽  
Dihydrogen Phosphate ◽  
Kdp Crystal ◽  
Potassium Dihydrogen ◽  
Electro Optic ◽  
Lock In

In this paper, a method of measuring the β31 coefficient of the quadratic electrogyration effect in potassium dihydrogen phosphate (KDP)-type crystals is proposed. It is shown that this very weak effect can be decoupled from other stronger effects occurring simultaneously in the real measuring system, even when small inaccuracies in crystal cutting and alignment are taken into account. Theoretical and numerical analyses are illustrated by experimental data obtained for the KDP crystal. High sensitivity, which is required for successful measurements at room and higher temperatures, has been achieved by using the polarimetric method for a light beam propagating along the optical axis of the crystal in combination with the lock-in technique and a new measurement procedure that compensates for the contribution of other effects such as electro-optic effects, natural birefringence and dichroism. It was found that the β31 coefficient measured at a wavelength of 632.8 nm decreases linearly from 2.53 × 10−21 m2 V−2 at a temperature of 298 K to 2.08 × 10−21 m2 V−2 at 343 K.

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