A Study of The Viability of Poly(O-Methoxyanhine) Layer-by-Layer Films as Gas Sensors

1999 ◽  
Vol 558 ◽  
Author(s):  
M. Raposo ◽  
O.N. Oliveira
Keyword(s):  
Relative Humidity ◽  
Gas Sensors ◽  
Complex Impedance ◽  
Layer By Layer ◽  
Fixed Frequency ◽  
Humid Atmosphere ◽  
Impedance Measurements ◽  
The Real ◽  
Order Of Magnitude ◽  
Impedance Component

ABSTRACTThe electrical properties of layer-by-layer films of poly(o-methoxyaniline) (POMA) alternated with poly(vinylsulfonic acid) (PVS) have been investigated as a function of the surrounding atmosphere, in order to probe the sensitivity of POMA/PVS as a gas sensor. The POMA films have their conductivity increased with increasing humidity, near to one order of magnitude higher for 100% relative humidity when compared to nitrogen. The d.c. applied field may affect the POMA films, for these films become practically insulating if the field is applied for a prolonged time (typically 10-20 h) in humid air. In order to circumvent this problem, a.c. impedance measurements were conducted. For samples in nitrogen, oxygen and carbon dioxide, the real part of the complex impedance increases only when the frequency is lowered below 10 kHz. In a humid atmosphere, the onset for the real part occurs at higher frequencies than for dry atmospheres. Furthermore, at a fixed frequency in the range from 10 to 100 kHz this impedance component increases with the relative humidity.

Conduction Characteristics of Charge Ordering Type Ferroelectrics,YFe2O4

2006 ◽  
Vol 966 ◽  
Author(s):  
Ken Imamura ◽  
Yoichi Horibe ◽  
Takeshi Yoshimura ◽  
Norifumi Fujimura ◽  
Shigeo Mori ◽  
...  
Keyword(s):  
Room Temperature ◽  
Inflection Point ◽  
Oxygen Deficiency ◽  
Complex Impedance ◽  
Charge Ordering ◽  
Neel Temperature ◽  
Ohmic Conduction ◽  
Néel Temperature ◽  
Impedance Measurements ◽  
Conduction Properties

ABSTRACTElectrical conduction properties of charge ordering type ferroelectrics YFe2O4 were investigated. YFe2O4 was synthesized in reduced atmosphere at 1200 °C. Oxygen partial pressure of the reduced atmosphere was controlled by the equilibrium state of CO and CO2. YFe2O4 is paramagnetic at room temperature and has Néel temperature around 250K. The Néel temperature was decreased with increasing the amount of oxygen deficiency. Moreover, YFe2O4 showed ohmic conduction from 260 to 100 K. The temperature dependence of the DC conductivity showed an inflection point at the Néel temperature, which indicated the development of charge ordering of Fe2+ and Fe3+ ions. From the complex impedance measurements, the equivalent circuits of YFe2O4 with different oxygen deficiency were determined at various temperatures.

scholarly journals Complex impedance measurements of calorimeters and bolometers: Correction for stray impedances

2007 ◽  
Vol 78 (4) ◽  
pp. 043105 ◽  
Author(s):  
Mark. A. Lindeman ◽  
Kathleen A. Barger ◽  
Donald E. Brandl ◽  
S. Gwynne Crowder ◽  
Lindsay Rocks ◽  
...  
Keyword(s):  
Complex Impedance ◽  
Impedance Measurements

scholarly journals Electrochemical synthesis of poly(2-methyl aniline): electrochemical and spectroscopic characterization

2001 ◽  
Vol 66 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Aleksandra Buzarovska ◽  
Irena Arsova ◽  
Ljubomir Arsov
Keyword(s):  
Raman Spectroscopy ◽  
Cyclic Voltammetry ◽  
Redox Reactions ◽  
Electrochemical Polymerization ◽  
Spectroscopic Characterization ◽  
Potential Range ◽  
Cyclic Voltammograms ◽  
Impedance Measurements ◽  
Order Of Magnitude ◽  
Poly Aniline

Poly(2-methyl aniline) or poly(ortho-toluidine), as ring substituted derivative of aniline, has been synthesized electrochemically in various concentrations of H2SO4 and HCl, and then characterized by cyclic voltammetry, as well as by impedance and Raman spectroscopy. The cyclic voltammograms of poly(o-toluidine) and poly(aniline) show that the electrochemical polymerization of these two polymers proceeds by almost identical mechanisms. The Raman spectroscopical measurements suggest that the redox reactions of poly(aniline) and poly(o-toluidine) are similar in the potential range between -0.2 and 0.7V vs. SCE. The impedance measurements showed that the conductivity of poly(o-toluidine) is an order of magnitude lower than that of the corresponding poly(aniline) form.

scholarly journals Enhanced NO2-Sensing Properties of Au-Loaded Porous In2O3 Gas Sensors at Low Operating Temperatures

Chemosensors ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 72
Author(s):  
Taro Ueda ◽  
Inci Boehme ◽  
Takeo Hyodo ◽  
Yasuhiro Shimizu ◽  
Udo Weimar ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Gas Sensors ◽  
Adsorption Mechanism ◽  
Operating Temperature ◽  
Oxide Surface ◽  
Free Electrons ◽  
Sensing Properties ◽  
Semiconductor Gas Sensors ◽  
No2 Adsorption ◽  
Adsorption Desorption

NO2-sensing properties of semiconductor gas sensors using porous In2O3 powders loaded with and without 0.5 wt% Au (Au/In2O3 and In2O3 sensors, respectively) were examined in wet air (70% relative humidity at 25 °C). In addition, the effects of Au loading on the increased NO2 response were discussed on the basis of NO2 adsorption/desorption properties on the oxide surface. The NO2 response of the Au/In2O3 sensor monotonically increased with a decrease in the operating temperature, and the Au/In2O3 sensor showed higher NO2 responses than those of the In2O3 sensor at a temperature of 100 °C or lower. In addition, the response time of the Au/In2O3 sensor was much shorter than that of the In2O3 sensor at 30 °C. The analysis based on the Freundlich adsorption mechanism suggested that the Au loading increased the adsorption strength of NO2 on the In2O3 surface. Moreover, the Au loading was also quite effective in decreasing the baseline resistance of the In2O3 sensor in wet air (i.e., increasing the number of free electrons in the In2O3), which resulted in an increase in the number of negatively charged NO2 species on the In2O3 surface. The Au/In2O3 sensor showed high response to the low concentration of NO2 (ratio of resistance in target gas to that in air: ca. 133 to 0.1 ppm) and excellent NO2 selectivity against CO and ethanol, especially at 100 °C.

scholarly journals The effect of ozone on wet atmospheric corrosion of aluminium of high-voltage lines

2019 ◽  
Vol 294 ◽  
pp. 05010
Author(s):  
Galina Tatarchenko ◽  
Nataliia Beloshitskaya ◽  
Viktor Sychenko ◽  
Vitalii Liashuk
Keyword(s):  
Oxide Film ◽  
Traffic Safety ◽  
Electric Energy ◽  
Protective Layer ◽  
Cyclic Polarization ◽  
Humid Atmosphere ◽  
Electrode Layer ◽  
Positive Side ◽  
Order Of Magnitude ◽  
Auger Spectra

One of the factors influencing traffic safety is the uninterrupted power supply of interlocking devices. As a rule transmission of electric energy is carried out using aluminum wires. In order to assess the reliability of power lines in the work, research was carried out on the influence of ozone on corrosion of aluminum in a humid atmosphere and acidic medium. It was found that the presence of oxygen dissolved in acetic acid leads to anode currents increase, while at crossover ozone, cathode currents increase by an order of magnitude and 2-3 times the anode decreases; the corrosion potential of an Ecor shifts to the positive side at 0.15V. The decrease in the density of anode currents in the presence of ozone proceeds due to the growth of the thickness of the aluminum oxide film. According to the Auger-spectra, the film is increased by 3-4 times compared with the nonzonized medium, due to which the corrosion resistance of aluminum Кm increases from 0.066 to 0.025 g/(m2·h). The rate of formation of oxides depends on the concentration of oxidants in the solution, and on their oxidative activity. According to calculations of thermodynamic factors that determine the preferred route of oxidation, the probability of formation of oxides in the presence of ozone is significantly higher. Local destruction of the protective layer occurs mainly in defective places and places of local increase in pH of the electrode layer. Investigation of the cyclic polarization of a sample of aluminum, pre-cathode activated by a current of 1 mA/cm2 density, showed the presence of hysteresis, which decreases in the next 2-3 cycles. In this case, the exterior of the aluminum shifts to (0.10 ÷ 0.15) V is more positive and the corrosion rate is reduced, which indicates the formation of an oxide film in which irreversible changes occur. The change in the inclination of the polarization curves indicates that the cathodic reaction is delayed and is associated with the change in the structure of the surface layer of the electrode and the diffusion restrictions of ozone recovery.

scholarly journals A Miniature pH Probe Using Functional Microfiber Bragg Grating

Optics ◽  
2020 ◽  
Vol 1 (2) ◽  
pp. 202-212 ◽  
Author(s):  
Yang Ran ◽  
Peng Xiao ◽  
Yongkang Zhang ◽  
Deming Hu ◽  
Zhiyuan Xu ◽  
...  
Keyword(s):  
Self Assembly ◽  
Ph Sensor ◽  
Fiber Surface ◽  
Bragg Grating ◽  
Wavelength Shift ◽  
Layer By Layer ◽  
Compact Size ◽  
Layer Technique ◽  
Order Of Magnitude ◽  
Ph Probes

Operando and precisely probing aqueous pH is fundamentally demanded, both in chemical and biological areas. Conventional pH probes, subjected to the larger size, are probably unfit for application in some extreme scenarios, such as a trace amount of samples. In this paper, we have further developed the pH sensor that leverages the microfiber Bragg grating with an ultra-compact size down to an order of magnitude of 10−14 m3. Using the electrostatic self-assembly layer-by-layer technique, the functional film consisting of sodium alginate, which harnesses a pH-dependent hygroscopicity, is immobilized on the fiber surface. Consequently, the alteration of aqueous pH could be quantitatively indicated by the wavelength shift of the grating resonance via the refractive index variation of the sensing film due to the water absorption or expulsion. The grating reflections involving fundamental mode and higher order mode exhibit the sensitivities of −72 pm/pH and −265 pm/pH, respectively. In addition, temperature compensation can be facilitated by the recording of the two reflections simultaneously. Furthermore, the modeling and simulation results predict the pivotal parameters of the configuration in sensitivity enhancement. The proposed proof-of-concept enriches the toolbox of pH sensor for catering to the need of detection in some extremely small spaces—for example, the living cells or the bio-tissues.

Impedance measurements of chemical gas sensors

2003 ◽  
Author(s):  
F. Vyslouzil ◽  
M. Vrnata ◽  
V. Myslik ◽  
M. Kovanda ◽  
R. Frycek ◽  
...  
Keyword(s):  
Gas Sensors ◽  
Impedance Measurements

Electrical Impedance Based Characterization of Wettability During Electrostatic Suppression of the Leidenfrost State

2019 ◽  
Author(s):  
Onur Ozkan ◽  
Vaibhav Bahadur
Keyword(s):  
Heat Transfer ◽  
Electrical Impedance ◽  
Statistical Nature ◽  
Impedance Measurements ◽  
Threshold Voltages ◽  
Different Temperatures ◽  
Order Of Magnitude ◽  
Wetted Area ◽  
Impedance Characterization

Abstract An electric field can suppress the Leidenfrost state by electrostatically attracting liquid to the surface, which results in significantly higher heat transfer. This study highlights and quantifies the statistical nature of wetting during electrostatic suppression via electrical impedance characterization of Leidenfrost pools. Firstly, electrical impedance characterization is used to study the onset of suppression of the Leidenfrost state. Two different threshold voltages are defined and measured. The first threshold voltage corresponds to the onset of transient (intermittent) wetting and the second threshold corresponds to the onset of continuous wetting. The effect of the temperature and the applied AC waveform frequency on the threshold voltages is studied. Next, the wetted area is measured for different temperatures and voltages. The statistical nature of wetting during electrostatic suppression of the Leidenfrost state is characterized. The measured wetting enhancement indicates that heat transfer can be enhanced by an order of magnitude via electrostatic suppression. Together, these results provide an in-depth understanding of electrostatic suppression, and highlight electrical impedance measurements as a powerful diagnostic tool for this field.

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