A novel analog fuzzy controller for intelligent sensors

A new analog fuzzy logic controller implemented in CMOS technology is described. The chosen membership function generator keeps the needed area for the inference engine very small while giving a big flexibility in the configuration of the membership function. The proposed solution for defuzzification gives an additional area reduction over earlier implementations. High speed, low power fuzzy controller hardware make the chip appropriate for intelligent sensor application. Simulation results as well as test measurements are presented and discussed to illustrate the properties and robustness of the proposed circuit.     

Multiplexing Techniques for Noninterferometric Optical Point-Sensor Networks: A Review

This article presents a review of the strategies that have been both demonstrated and proposed for the multiplexing of multiple noninterferometric optical fiber point sensors to form a sensor network. The focus, which avoids consideration of interferometric sensor types, enables discussion of conventional multiplexing tech niques, namely, spatial, time division, frequency division, and wavelength division prior to dealing with combined or hybrid schemes, which exhibit the potential for increased multiplexing gain. Specific advantages and potential drawbacks of the different strategies are provided together with an indication of the number of point sensors that each multiplexing scheme can support.     

Novel NO2 Gas Sensor Based on Cr(III) Complex Thin Film

The results concerning the gas‐sensing characteristics of novel NO₂ gas sensors, fabricated from complex [Cr(bipyO₂)Cl₂]Cl thin films, were first presented. The sensors exhibited high response to NO₂ gas in the concentration range from 1.97% to 6.67% at relative low temperatures (from room temperature to 348 K). No response to H₂S and SO₂ was observed. The maximum response for 6.03% NO₂ was approximately 11.7 at 338 K and 10 V operating voltage. The response time of the sensors was about 4.5 min for NO₂ and the recovery time about 40 s. The effect of the electrical resistance change of the sensors in the presence of NO₂ could be used for gas sensing measurements. The performance and reliability of the sensors showed their potential applications for monitoring and controlling NO₂ component continuously in chemical production.     

Chemical Sensors and Biosensors—Principles and Applications

Chemical and environmental engineering and biotechnology are among the fields now being transformed by continually increasing levels of automation. Whereas the objective in other sectors of industry is simply to increase efficiency, here considerations of system theory or safety demand a high level of automation. Either the processes are too complex and require multifunctional control with feedback, or an analysis of the safety requirements shows the necessity for a certain degree of redundancy in the safety measures, and for elimination of human error as a risk factor. With regard to quality control, cost-benefit analyses lead to striking conclusions which again indicate the need for highly automated, and above all reliable, systems to eliminate rejects. The crux of any automated system is the measurement and control technology; of central importance is the rapid, reliable, and in some cases continuous, measurement and interpretation of key processes or control variables. For this purpose a wide variety of recording instruments and sensors are used to give as accurate a picture as possible of the state of the system. It is obvious from this that the performance of the control system is critically dependent on the sensors. Errors in the measured quantities can become amplified in the control variables or, in dynamic systems, can lead to undesirable operating conditions. Moreover, as a consequence of great advances in microelectronics, “intelligent sensors” which can calibrate and control themselves will be one of the key technologies of the nineties. Unless fast and immediate information on the true current status of a system is available, microprocessors as control devices react blindly and unpredictably to errors in input information. New discoveries in the fields of electronic, electrochemical, and optical transducers are now being applied in heterogeneous catalysis and surface physics, and in biochemistry (enzymology and immunology); in these fields new chemical sensor principles are being tested, which could revolutionize instrumental methods of molecular analysis in particular, owing to their very favorable cost-performance relationship. This article aims to give an up-to-date overview of the current state of the art in these developments, with emphasis on their importance for analysis and their significance in relation to the chemist's interest in mechanisms for identifying substances.     

Development and Infrared Applications of Chalcogenide Glass Optical Fibers

Chalcogenide glass fibers based on sulphide, selenide, telluride, and their rare earth doped compositions are being actively pursued both at the Naval Research Laboratory in Washington, D.C. (NRL) and worldwide. Great strides have been made in reducing optical losses using improved chem ical purification techniques, but further improvements are needed in both purification and fiberization technology to attain the theoretical optical losses. Despite this, current singlemode and multimode chalcogenide glass fibers are enabling numerous applications. Some of these applications include laser power delivery, chemical sensing, imaging, scanning near field microscopy spectroscopy, fiber infrared (IR) sources lasers, amplifiers, and optical switches. The authors assert that the research and development of chalcogenide glasses will grow in the foreseeable future, especially with respect to improvements the optical quality of the fibers and the performance of the fibers in existing future applications.     

Ag/ZnO Catalysts with Different ZnO Nanostructures for Non‐enzymatic Detection of Urea

Silver coated ZnO nanorods and nanoflakes with different crystallographic orientations were synthesized by a combination of sputter deposition and solution growth process. Catalytic properties of morphology‐dependent Ag/ZnO nanostructures were then investigated for urea sensors without enzyme. Ag/ZnO nanorods on carbon electrodes exhibit a higher catalytic activity and an improved efficiency than Ag/ZnO nanoflakes on carbon electrodes. Ag/ZnO nanorod catalysts with more electrochemically surface area (169 cm² mg^?1) on carbon electrode facilitate urea electrooxidation due to easier electron transfer, which further promotes the urea electrolysis. The Ag/ZnO nanorod catalysts also show a significant reduction in the onset voltage (0.410 V vs. Ag/AgCl) and an increase in the current density (12.0 mA cm^?2 mg^?1) at 0.55 V vs Ag/AgCl. The results on urea electrooxidation show that Ag/ZnO nanostructures can be a potential catalyst for non‐enzymatic biosensors and fuel cells.     

Far‐ and Deep‐Ultraviolet Surface Plasmon Resonance Sensor

Plasmonics in the UV region has been widely focused because of the higher energy and the abundant electronic resonances compared to the conventional visible plasmonics. Recently, we have investigated the surface plasmon resonance (SPR) properties of the Al film, aiming for the application as refractive index sensors. Utilizing the UV lights, we expect three advantages: high sensitivity, material selectivity, and surface selectivity. By using an original attenuated total reflectance spectroscopic instrument, Al‐SPR angle and wavelength were investigated with changing environments on the Al film. Al film thickness and materials of prisms on which Al was evaporated were also important factors for the SPR properties. By optimizing the conditions, the Al film worked as a sensor both in air and in liquids. In addition, our established system expands the plasmonics into an even higher energy region than 200 nm, while the UV‐plasmonics have been studied in the wavelength region longer than 200 nm.     

Nanomaterials for electrochemical detection of pollutants in water: A review

The survival of living beings, including humanity, depends on a continuous supply of clean water. However, due to the development of industry, agriculture, and population growth, an increasing number of wastewaters is discarded, and the negative effects of such actions are clear. The first step in solving this situation is the collection and monitoring of pollutants in water bodies to subsequently facilitate their treatment. Nonetheless, traditional sensing techniques are typically laboratory-based, leading to potential diminishment in analysis quality. In this paper, the most recent developments in micro- and nano-electrochemical devices for pollutant detection in wastewater are reviewed. The devices reviewed are based on a variety of electrodes and the sensing of three different categories of pollutants: nutrients and phenolic compounds, heavy metals, and organic matter. From these electrodes, Cu, Co, and Bi showed promise as versatile materials to detect a grand variety of contaminants. Also, the most commonly used material is glassy carbon, present in the detection of all reviewed analytes.     

Fine Pore-Structure Engineering by Ligand Conformational Control of Naphthalene Diimide-Based Semiconducting Porous Coordination Polymers for Efficient Chemiresistive Gas Sensing

Exploring new porous coordination polymers (PCPs) that have tunable structure and conductivity is attractive but remains challenging. Herein, fine pore structure engineering by ligand conformation control of naphthalene diimide (NDI)-based semiconducting PCPs with π stacking-dependent conductivity tunability is achieved. The π stacking distances and ligand conformation in these isoreticular PCPs were modulated by employing metal centers with different coordination geometries. As a result, three conjugated PCPs (Co−pyNDI, Ni−pyNDI, and Zn−pyNDI) with varying pore structure and conductivity were obtained. Their crystal structures were determined by three-dimensional electron diffraction. The through-space charge transfer and tunable pore structure in these PCPs result in modulated selectivity and sensitivity in gas sensing. Zn−pyNDI can serve as a room-temperature operable chemiresistive sensor selective to acetone.     

Photochemical Mechanisms of Fluorophores Employed in Single-Molecule Localization Microscopy

Decoding cellular processes requires visualization of the spatial distribution and dynamic interactions of biomolecules. It is therefore not surprising that innovations in imaging technologies have facilitated advances in biomedical research. The advent of super-resolution imaging technologies has empowered biomedical researchers with the ability to answer long-standing questions about cellular processes at an entirely new level. Fluorescent probes greatly enhance the specificity and resolution of super-resolution imaging experiments. Here, we introduce key super-resolution imaging technologies, with a brief discussion on single-molecule localization microscopy (SMLM). We evaluate the chemistry and photochemical mechanisms of fluorescent probes employed in SMLM. This Review provides guidance on the identification and adoption of fluorescent probes in single molecule localization microscopy to inspire the design of next-generation fluorescent probes amenable to single-molecule imaging.