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Modern electronic nose and such systems, typically employ gas sensors in arrays. Access to the individual elements in an m × n resistive sensor array requires m + n interconnect lines and effect of crosstalk becomes inevitable. The crosstalk is caused due to the leakage currents in the multiplexer channels as well as the parasitic paths among the non-selected elements in the array. Here, the authors present a novel circuit arrangement to suppress crosstalk in two-dimensional chemo-resistive sensor arrays. The proposed circuit employs a transistorised bypassing scheme, diodes in series and voltage feedback to non-selected elements of an array for crosstalk elimination. Simulation results of a resistive sensor array are presented. Finally, the proposed arrangement has been applied on an 8 × 2 sensor array and the result has been compared with the same array with a normal feedback arrangement for data acquisition. The work can also be extended for general resistive sensor arrays.

This article demonstrates an optical fiber sensor probe coated with hierarchical nanostructures of zinc oxide (ZnO) for trace level detection of volatile amines. The nanostructure is grown by hydrothermal process on a multimode optical fiber probe coated with ZnO nanofibrous mat prepared by electrospinning technique. The high surface area of the hierarchical structures facilitated diffusion of amines, which, on interaction with ZnO surface, changes the effective refractive index of the optical fiber probe. The modulation of the transmitted intensity through the optical sensor probe in presence of the target analyte is monitored for sensing the amine. An increase in absorbance is observed in proportion to amine concentrations with the emergence of a broad peak at around 500nm. The sensor is able to detect as low as 25ppb of different volatile amines such as ammonia, triethylamine, aniline, and ethylenediamine with responses of 1, 0.65, 0.75, and 0.5, respectively. The sensor is further demonstrated for detection of volatile amines released during protein degradation in salmon fish to show its usability for real time applications.

In this work, a multimode optical fiber sensor probe coated with polypyrrole-polyethylene oxide (PPO) nanofibrous mat is investigated to detect volatile compounds such as ammonia, triethylamine, methanol, ethanol and acetone vapours. The fibrous mat on the fiber cladding is deposited using electrospinning method followed by vapour phase polymerization. The affinity of PPO towards different volatile compounds changes the effective refractive index of optical fiber cladding, modulating the intensity of the transmitted spectrum. The intensity variation in presence of volatile vapours of different concentration is investigated to determine the responses of the sensor probe. The sensor probe shows different detection limit such as 0.1 ppm, 2 ppm, 2 ppm, and 1 ppm and recovery time of 10 min, 54.4s, 21.06 s and 11.08 s for ammonia, ethanol, methanol and triethylamine vapours respectively. Thus, the electrospinning technique can be used for coating optical fiber cladding with special material such as PPO to develop optical fiber based sensor to detect trace amount of volatile compound.

Herein, we report noble metal free, cathodically co-electroreduced rGO/MnO2 nanohybrid (NH) on glassy carbon electrodes for arsenite (As (III)) detection in water by square wave anodic stripping voltammetry (SWASV). Cyclic voltammetry, scaning electron microscopy, X-ray diffraction, trasnsmission electron microsocpy and Fourier transform infra-red (FT-IR) spectroscopy were used to probe the rGO/MnO2/GCE surface, revealing the formation of NHs. The arsenite sensing parameters such as deposition potential and time was optimized allowing a detection range of 0.1 ppb to 50 ppb in 0.1 M acetate buffer. This in-situ fabricated NHs electrodes exhibit favourable sensitivity of 0.175 μA/ppb with a theoritical limit of detection of 0.05 ppb for arsenite, which is well below the levels set by World Health Organization. Moreover, the fabricated electrode exhibited good selectivity, stability and reproducibility, in near alkaline condition without using any noble metal as sensing electrode component, desirable for practical application. These findings suggest the possibility of a cost effective electrochemical sensing electrode for a portable embedded system to determine As (III) in water.

Zinc oxide (ZnO) and bacteriorhodopsin (bR) hybrid nanostructures were fabricated by immobilizing bR on ZnO thin films and ZnO nanorods. The morphological and spectroscopic analysis of the hybrid structures confirmed the ZnO thin film/nanorod growth and functional properties of bR. The photoactivity results of the bR protein further corroborated the sustainability of its charge transport property and biological activity. When exposed to ethanol vapour (reducing gas) at low temperature (70 °C), the fabricated sensing elements showed a significant increase in resistivity, as opposed to the conventional n-type behaviour of bare ZnO nanostructures. This work opens up avenues towards the fabrication of low temperature, photoactivated, nanomaterial–biomolecule hybrid gas sensors.

In this work, an artificial lipid membrane was synthesized using tetra-dodecyl ammonium bromide (TDAB) and doped with gold nanoparticles (AuNP). The taste sensor designed using artificial lipid membrane is composed of tetradodecylammonium bromide (TDAB) as a lipid, dioctylphenyl phosphonate (DOPP) as a plasticizer, and polyvinyl chloride (PVC) as a supporting polymer in the ratio of 1:3:2. The lipid/polymer membrane acts as the recognition element which transforms the taste information generated by the chemical substances into an electric potential change. The fundamental taste analytes (like fructose for sweetness, HCl for sourness, NaCl for saltiness, MgCl2 for bitterness and MSG for umami) were used to study the effect of doping on taste sensing at different concentrations (10μM to 10mM). The study was based on the open circuit potential (OCP) change of the membrane with the analytes. The observations implicate that the doping increases the specificity of the artificially synthesized lipid membrane taste sensor for the sweet analytes, particularly for fructose.

Tin oxide-polypyrrole composites have been widely studied for their enhanced sensing performance towards ammonia vapours, but further investigations are required for an understanding of the interaction mechanisms with different target analytes. In this work, polypyrrole coated tin oxide fibers have been synthesized using a two-step approach of electrospinning and vapour phase polymerization for the sensing of ammonia, ethanol, methanol, 2-propanol and acetone vapours. The resistance variation in the presence of these vapours of different nature and concentration is investigated for the determination of sensor response. A decrease in resistance occurred on interaction of tin oxide-polypyrrole with ammonia, as opposed to previous reported works. Partial reduction of polypyrrole due to interfacial interaction with tin oxide has been proposed to explain this behavior. High sensitivity of 7.45 is achieved for 1 ppm ammonia concentration. Furthermore, the sensor exhibited high sensitivity and a faster response towards ethanol vapours although methanol has the highest electron donating capability. The catalytic mechanism has been discussed to explain this interesting behavior. The results reveal that interaction between tin oxide and polypyrrole is crucial to control the predominant sensing mechanism.

Access to potable water for the common people is one of the most challenging tasks in the present era. Contamination of drinking water has become a serious problem due to various anthropogenic and geogenic events. The paper demonstrates the application of evolutionary algorithms, viz., particle swan optimization and genetic algorithm to 24 water samples containing eight different heavy metal ions (Cd, Cu, Co, Pb, Zn, Ar, Cr and Ni) for the optimal estimation of electrode and frequency to classify the heavy metal ions. The work has been carried out on multi-variate data, viz., single electrode multi-frequency, single frequency multi-electrode and multi-frequency multi-electrode water samples. The electrodes used are platinum, gold, silver nanoparticles and glassy carbon electrodes. Various hazardous metal ions present in the water samples have been optimally classified and validated by the application of Davis Bouldin index. Such studies are useful in the segregation of hazardous heavy metal ions found in water resources, thereby quantifying the degree of water quality.