Unconventional Synthesis of gamma-Fe2O3: Excellent Low-Concentration Ethanol Sensing Performance

This study reports on a simple unconventional procedure for synthesis of gamma-Fe2O3 nanopowder and its fabrication as a resistive ethanol sensor. gamma-Fe2O3 powder having an average particle size of similar to 15 nm was prepared by thermal decomposition of iron(III) acetylacetonate. Platinum incorporation (0.5-1.5 wt.%) was also carried out for enhancing sensing performance. The powders were characterized using an x-ray diffractometer, x-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area, field area scanning electron microscopy, transmission electron microscopy along with energy dispersion x-ray analyses. Sensor fabricated from pure gamma-Fe2O3 exhibited excellent ethanol sensing performance at concentrations down to 1 ppm, having a great demand in medical diagnosis and food-processing industries. The response observed for pure gamma-Fe2O3 (similar to 75% for 1 ppm ethanol) was enhanced similar to 10% after 1 wt.% Pt impregnation. Sensors were quite stable and selective towards ethanol vapour detection. A possible mechanism for high sensing performance has been discussed

Highly Sensitive and Wearable ZnO-Graphene Nanocomposite-Based Strain Sensors for Human Motion Detection

Flexible electronic sensors have garnered considerable interest in wearable health-monitoring devices and electronic skin. In this work, a simple method for the fabrication of flexible zinc oxide-graphene nanoplatelet (ZnO-GNP) nanocomposite-based strain sensors has been proposed. The sensing element was deposited on the polydimethylsiloxane (PDMS) substrate by a facile spin and peel strategy to yield flexible sandwiched sensors. The effect of varying the blending ratio of the constituents on the electromechanical responses of the sensors was studied. The sensors exhibited high stretchability, good sensitivity, high reversibility, and superior stability under tensile and bending loads. The flexible nanocomposite sensors were able to detect extensive human movements such as bending of the elbow, wrist, and finger and also subtle motions such as eye blinking, wrist pulse, and phonation. Owing to the facile and economical fabrication method, high sensitivity, and good reversibility, the ZnO-GNP sensors have a high prospect of application in wearable health-monitoring devices, robotics, and various forms of human-machine interface

Pd impregnated gallia: tin oxide nanocomposite An excellent high temperature carbon monoxide sensor

1 wt% Pd impregnated gallia: tin oxide nanocomposite sensors were investigated for high temperature carbon monoxide detection. Initially the mixed oxide nanopowder, containing 25 wt% gallia, was synthesised using a facile cost effective sol-gel procedure. 0.25 wt% antimony doping was done to facilitate lower resistance of the corresponding sensor in terms of electronic perspective. The structural and microstructural characterizations of the nanocomposites were carried out with X-ray diffractometer, BET surface area, XPS, TEM and EDX analyses. Taguchi design based thick film sensors were fabricated and CO sensing performance was evaluated in the operating temperature range of 300-500 degrees C. Nanocomposite sensor showed similar to 48% optimum response for 30 ppm CO at temperature of 425 degrees C with stable low resistance. Pd incorporation led to a significant improvement in sensing response (similar to 65%) at the same condition along with decrease in response and recovery times. Possible sensing mechanism of enhancement has been explored. (C) 2017 Elsevier B.V. All rights reserved

A novel ppm level ethanol sensor based on La loaded ITO impregnated with Pd and Sb additives

The present work reports on a novel resistive ppm level ethanol sensor, prepared from nanocrystalline lanthanum loaded indium tin oxide (ITO) impregnated with palladium and antimony additives. A simple unique gel calcination process was adapted to synthesize the nanocomposite powders from their water based precursor salts. This was followed by detailed material characterizations through X-ray diffractometer, FESEM, TEM, EDX and XPS analyses. Fabricated Taguchi type sensor with an optimum concentration of Pd exhibited an excellent sensing performance towards a wide concentration range of (1-100 ppm) ethanol vapour. The sensor showed similar to 87% sensing response for 10 ppm ethanol vapour at an operating temperature of 300 degrees C. Even at 1 ppm concentration, similar to 53% response was observed with fast response and recovery time. The sensing action has been elucidated as the catalytic oxidation of ethanol to carbon di oxide over the La loaded ITO surface layer that resulted in electron transfer to the indium tin oxide site. In addition, synergistic effect of palladium and antimony enhanced the sensing performance as well as reduced the base resistance of the sensor by chemical/electronic sensitization and increasing carrier ion concentration respectively. Comparatively low resistance, negligible cross sensitivity, quick response/recovery time and good long term stability makes the sensor suitable for deployment in practical applications

Enhanced performance of gamma-Fe2O3:WO3 nanocomposite towards selective acetone vapor detection

Metal oxide nanocomposite sensors based on gamma-Fe2O3 and WO3 were investigated in acetone vapor of various concentrations (1-100 ppm) at operating temperatures between 250 and 350 degrees C. The composites were prepared by simple solid state mixing and porous thick-film gas sensors were fabricated on alumina substrates. The gamma-Fe2O3:WO3 (50:50) nanocomposite showed a marked enhancement in sensing response down to 1 ppm acetone vapor detection at 300 degrees C. The response was similar to 2-fold better compared to pure WO3 or pure gamma-Fe2O3 with a very fast response (1 s) and very short recovery time (3 s). No appreciable sensitivity was observed towards alcohol vapor (an interfacing agent for diabetics) and in moisture (present in breath). The enhanced performance was due to n-n heterojunction effect. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Synergistic effect of Pd and Sb incorporation on ethanol vapour detection of La doped tin oxide sensor

4 wt% La-doped SnO2 nanocrystalline powders impregnated with 0.5-1.5 wt% Pd were synthesized by a facile sol-gel method. The powders characterized through XRD, TEM, EDX as well as XPS analyses were used for the fabrication of sensors. 0.5 wt% Sb2O3 was incorporated in each case to reduce the resistance of sensors. The gas response studies revealed a large enhancement in low concentration (1-100 ppm) ethanol vapour sensing at comparatively lower operating temperature (300 A degrees C) on 1.0 wt% Pd incorporation. The response observed (86 %) for 10 ppm vapour was 16 % greater compared to 4 wt% La-doped SnO2 with improved response (2 s) and recovery (15 s) times. The high ethanol vapor response at comparatively lower operating temperature of this sensor is attributed to the combinatorial effect of alkalescence of SnO2 due to La-doping and widening of depleted region by spill-over process of PdO present on SnO2 surface

Fast detection of low concentration carbon monoxide using calcium-loaded tin oxide sensors

Solid state sensors with noble metal-loaded tin oxide as sensing elements are widely used for the detection of flammable and toxic gases and volatile organic compounds (VOCs). Apart from rendering high cost, incorporation of noble metals often increases the preconditioning time and introduces a drift in baseline properties of the sensors. Herein, we report on the development of stable and economically viable sensor modules for fast and efficient detection of carbon monoxide (CO) in air. The sensing layer comprises sonochemically synthesized calcium-loaded tin oxide (Ca-SnO2) nanocrystals, in which calcium primarily gets segregated at the SnO2 grain boundaries as calcium oxide (CaO) and thereby restricts the growth of SnO2 particles. Due to larger ionic radius of Ca2+ as compared to that of Sn4+, a minute quantity of calcium can be doped as well into the SnO2 lattice. The variation of calcium concentration in SnO2 has a prominent effect on the sensor performance, where 5 wt% calcium loading shows the highest sensor response. The sensors exhibit a lower detection limit of 1 ppm CO in air. The response time (10-12 s) and recovery time (30-45 s) of our sensors, for different concentrations of CO, are equivalent or less compared to those of commercially available metal-oxide sensors. Additionally, a highly stable baseline with minimal drift even after being operational for over 1.5 years is observed. (C) 2014 Elsevier B.V. All rights reserved

Synthesis, characterization and low concentration ethanol sensing performance of sol-gel derived La(III) doped tin oxide

Nanocrystalline undoped and lanthanum(III) doped (2, 4 and 6 at%) tin oxide powders were synthesized using sol-gel processing from their water based precursor sols. Microstructures and surface morphologies of all powders were characterized using X-ray diffractometer, BET surface area, UV-Visible spectrophotometer, scanning and transmission electron microscope along with energy dispersive X-ray diffractometer. XRD and UV-Vis spectral analyses revealed decrease of tin oxide crystallite size on La(III) doping. 4 at% La(III) doped powder showed similar to 5 nm average particle size and similar to 42 m(2)/g surface area respectively. A systematic comparison study revealed that sensors made from 4 at% La(III) doped SnO2 powder exhibited optimum ethanol vapor sensing performance at operating temperature, 350 degrees C (response similar to 70 % for 10 ppm ethanol) with excellent response and recovery times. Even for very low concentration ethanol vapour (1 ppm) response observed was similar to 53 %. A possible mechanism for enhancing sensitivity on La(III) doping has been discussed

A New Functional Composite for Photovoltaic and Sensor Applications

As a preliminary drive to eventually develop dye-sensitized solar cell (DSSC)-powered gas sensors, many oxide-based systems have been explored to fabricate sensors that can show response at room temperature for any analyte gas. As an outcome of recent work in this endeavor, a composite nanorod of anatase TiO2 with Na0.23TiO2 is found to exhibit both photovoltaic performance and gas sensing at room temperature as demonstrated here. An interesting morphology change along with a phase change from nanoparticle to nanorod is observed during the hydrothermal synthesis of anatase TiO2 nanoparticles with sodium hydroxide under a highly basic condition. In order to understand the effect of the minor phase Na0.23TiO2 on the inherent properties of anatase TiO2, the application of nanorod composite in two unique potential application areas, DSSC and acetone sensings is investigated. The composite material exhibits an enhanced efficiency of 7.85% for a DSSC. Surprisingly, a resistive sensor fabricated with the synthesized composite material exhibits room temperature p-type sensing behavior toward different concentrations of acetone (10, 5, 3, 2, and 1 ppm) with high selectivity