Ultra sensitive NO2 gas detection using the reduced graphene oxide coated etched fiber Bragg gratings

We report a simple and highly sensitive methodology for the room temperature NO2 gas sensing using reduced graphene oxide (RGO) coated clad etched fiber Bragg grating (eFBG). A significant shift (>10 pm) is observed in the reflected Bragg wavelength (lambda(B)) upon exposing RGO coated on the surface of eFBG to the NO2 gas molecules of concentration 0.5 ppm. The shift in Bragg wavelength is due to the change in the refractive index of RGO by charge transfer from the adsorbing NO2 molecules. The range of NO2 concentration is tested from 0.5 ppm to 3 ppm and the estimated time taken for 50% increase in Delta lambda(B) ranges from 20 min (for 0.5 ppm) to 6 min (for 3 ppm). (C) 2015 Elsevier B.V. All rights reserved.

Effects of sensing temperature on the NO2-sensing properties of octa-iso-pentyloxymetallonaphthalocyanine spin-coated films

A kind of 1,6,10,15,19,24,28,33-octa-iso-pentyloxy-2,3-metallonaphthalocyanines complexes MNc(iso-PeO)(8) (M = Co, Cu, Pd) are used as spincoating film-forming materials. The surface morphologies of the films prepared were studied first. These films were then used for the experiments of NO2 sensing. The effects of sensing temperature as well as the NO concentration on the sensing properties were studied. The experimental results showed that the three MNc(iso-PeO)(8) films were uniform, smooth and dense. Due to the different metal ions (M) on the center of naphthalocyanine, the CoNc(iso-PeO)(8) film had a higher film resistance and response-recovery rate in the NO2 sensing experiments. On the contrary, the response to NO2 of the PdNc(iso-PeO)(8) and CuNc(iso-PeO)(8) films were superior to that of CoNc(iso-PeO)(8). By varying the sensing temperature, it was found that the elevation of sensing temperature could improve the sensing response, recovery ratio, and sensitivity of the sensing films. At high concentrations of NO2, the response time became shorter. (c) 2007 Elsevier B.V. All rights reserved.

Síntesis y caracterización de perovskitas LaCoO3 y LaMnO3 para la oxidación de NO a NO2

Las perovskitas con fórmula general ABO(3) son una alternativa prometedora a los catalizadores convencionales basados en metales nobles para la reducción de contaminantes procedentes de motores diésel, debido a su bajo coste, excelentes propiedades redox y alta durabilidad. En este trabajo se sintetizarán las perovskitas LaCoO3 y LaMnO3, por el método del ácido cítrico. Las muestras preparadas serán caracterizadas por técnicas como XRD, BET, H2-TPR y SEM. Se analizará su actividad en la reacción de oxidación de NO a NO(2).

High sensitive NO2 gas sensor with low power consumption using selectively grown ZnO nanorods.

The noble gas sensor using multiple ZnO nanorods was fabricated with CMOS compatible process and sol-gel growth method on selective area and gas response characteristics to NO2 gas of the sensor device were investigated. We confirmed the sensors had high sensitive response denoted by the sensitivity of several tens for NO2 gas sensing and also showed pretty low power consumption close to 20 mW even though the recovery of resistance come up to almost the initial value.

A high temperature SOI CMOS NO2 sensor

For more than 20 years researchers have been interested in developing micro-gas sensors based on silicon technology. Most of the reported devices are based on micro-hotplates, however they use materials that are not CMOS compatible, and therefore are not suitable for large volume manufacturing. Furthermore, they do not allow the circuitry to be integrated on to the chip. CMOS compatible devices have been previously reported. However, these use polysilicon as the heater material, which has long term stability problems at high temperatures. Here we present low power, low cost SOI CMOS NO2 sensors, based on high stability single crystal silicon P+ micro-heaters platforms, capable of measuring gas concentrations down to 0.1 ppm. We have integrated a thin tungsten molybdenum oxide layer as a sensing material with a foundry-standard SOI CMOS micro-hotplate and tested this to NO2. We believe these devices have the potential for use as robust, very low power consumption, low cost gas sensors. © 2011 American Institute of Physics.

Graphene SOI CMOS sensors for detection of PPB levels of NO2 in air

There is considerable demand for sensors that are capable of detecting ultra-low concentrations (sub-PPM) of toxic gases in air. Of particular interest are NO2 and CO that are exhaust products of internal combustion engines. Electrochemical (EC) sensors are widely used to detect these gases and offer the advantages of low power, good selectivity and temporal stability. However, EC sensors are large (1 cm3), hand-made and thus expensive ($25). Consequently, they are unsuitable for the low-cost automotive market that demands units for less than $10. One alternative technology is SnO2 or WO3 resistive gas sensors that are fabricated in volume today using screen-printed films on alumina substrates and operate at 400°C. Unfortunately, they suffer from several disadvantages: power consumption is high 200 mW; reproducibility of the sensing element is poor; and cross-sensitivity is high. © 2013 IEEE.

The geometry of the NO2- anion: ab initio calculations and Franck-Condon analysis

Geometry optimization and harmonic vibrational frequency calculations have been performed on the (X) over bar (2)A(1) state of NO2 and (X) over bar (1)A(1) state of NO2-. Franck-Condon analyses and spectral simulations were carried out on the NO2((X) over bar (2)A(1))-NO2-((X) over bar (1)A(1)) photo detachment process. In addition, the equilibrium geometry parameters, r(NO)= 1.248 +/- 0.005 Angstrom and angle(ONO) 116.8 +/- 0.5degrees, of the (X) over bar (1)A(1) state of NO2-, are derived by employing an iterative Franck-Condon analysis procedure in the spectral simulation. Our conclusions regarding the anion geometry suggest a reinterpretation of the results of Woo et al. (C) 2004 Published by Elsevier B.V.

Microstructure and NO2 sensing properties of Fe2O3 thin films

W-doped Fe2O3 films have been fabricated on polycrystalline alumina substrates by the RF magnetron sputtering method, and effects of annealing temperature on the NO2 sensing properties have been examined. The crystal structure of the obtained film changed from Fe3O4 to α-Fe2O3 after annealing at temperatures of 500 to 500°C in air. An increase in the annealing temperature increased the particle size, resulting in a decrease in the NO2-gas sensitivity. These results suggest that the NO2 sensitivity of W-doped Fe2O3 film depends on the particle size.