Effect of m-nitroaniline doping on the optical humidity-sensing characteristics of cobalt/poly(vinyl alcohol) nanocomposites (original) (raw)
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Cobalt chloride doped polymer film for relative humidity measurement
2008
We report a simple approach to measure relative humidity with high dynamic range and fast response time using Cobalt chloride (CoCl 2 ) doped polymer thin film. Anhydrous Cobalt chloride exhibits high absorption at low humidity level in the wavelength range 550-700 nm while possess very low absorption at high humidity level present in the environment . Thin CoCl 2 doped polymer films of different thickness were fabricated on thin cover slides using dip coating technique. Expanded light from a diode laser source ( 680 nm ) was allowed to transmit through the sensing film of the slide. The variation in intensity of the transmitted light with the moisture level present in the environment was monitored using silicon photodiode and finally the detector signal was taken through a computer. As large area of the sensing region is exposed to the environment, high sensitivity of the sensor is achieved . Further, sensor response was investigated in terms of chemically synthesized film thickness on the slides. A high dynamic range of the sensor is obtained with fully reversible and repeatable behavior. The advantage of the system is its simplicity and is a very low cost technique to monitor relative humidity present in environment .
Evaluation of Co-Polyaniline nanocomposite thin films as humidity sensor
Talanta, 2008
Spin coated films of Co-Polyaniline nanocomposite are evaluated for their transmission properties using He-Ne laser for humidity sensing. The thickness (17-29 m) of the films is varied by multiple deposition of Co-Polyaniline nanocomposite on a glass substrate. The samples exhibit typically two to three regions in their sensitivity curve when tested in the relative humidity (RH) range of 20-95%. The sensitivity ranges from 0.1 mV/%RH to 12.26 mV/%RH for lower to higher thickness. The sensors show quick response of 8 s (20-95%RH), and a recovery time of 1 min (95-20%RH) with good repeatability, reproducibility and low hysteresis effect. The sensitivity of the sensor increases with humidity and thickness. Material characterization is done by X-ray diffraction (XRD), scanning electron micrograph (SEM) and Fourier transform infra-red spectroscopy (FTIR).
Electrical and humidity characterization of m-NA doped Au/PVA nanocomposites
Talanta, 2009
The Meta-Nitroaniline (m-NA) doped (by varying weight percentage (wt. %)) gold/polyvinyl alcohol (Au/PVA) nanocomposites were synthesized using gold salt and hydrazine hydrate (HH) by in situ process. The composite was coated on ceramic rods having two end electrodes by drop casting method for studying their electrical behavior at different relative humidity (RH) levels, ranging from 4 to 95% RH at room temperature. The optimized wt. % was used to prepare coatings of various thicknesses (20-40 m) of the films. As the humidity decreases, the resistance increases. The low humidity sensing characteristic can be tailored by varying wt. % of m-NA and thicknesses of the nanocomposite films. The resistive-humidity sensor shows two regions of sensitivity having highest sensitivity for lower RH. The sensor response and recovery time is about 6-10 s and 52 s respectively. The dynamic range of variation of the resistance allows a promising use of the films as a humidity sensor. The material was characterized by X-ray diffraction (XRD) and impedance spectroscopy at 60% RH.
Cobalt chloride doped polymer film for relative humidity measurement
International Symposium on Photoelectronic Detection and Imaging 2007: Optoelectronic System Design, Manufacturing, and Testing, 2007
We report a simple approach to measure relative humidity with high dynamic range and fast response time using Cobalt chloride (CoCl 2 ) doped polymer thin film. Anhydrous Cobalt chloride exhibits high absorption at low humidity level in the wavelength range 550-700 nm while possess very low absorption at high humidity level present in the environment . Thin CoCl 2 doped polymer films of different thickness were fabricated on thin cover slides using dip coating technique. Expanded light from a diode laser source ( 680 nm ) was allowed to transmit through the sensing film of the slide. The variation in intensity of the transmitted light with the moisture level present in the environment was monitored using silicon photodiode and finally the detector signal was taken through a computer. As large area of the sensing region is exposed to the environment, high sensitivity of the sensor is achieved . Further, sensor response was investigated in terms of chemically synthesized film thickness on the slides. A high dynamic range of the sensor is obtained with fully reversible and repeatable behavior. The advantage of the system is its simplicity and is a very low cost technique to monitor relative humidity present in environment .
Electrical and humidity sensing properties of synthesized hydrophosphoric acid doped polyaniline
Polymers for Advanced Technologies, 2008
Novel impedance-type humidity sensors were made of 1-(4-carboxylic acid phenyl)-2,5-dimethyl-1Hpyrrole that was doped with KOH and K 2 CO 3 salts. The humidity-sensing properties of 1-(4-carboxylic acid phenyl)-2,5-dimethyl-1H-pyrrole were improved by doping with two alkali salts (KOH and K 2 CO 3), whose dissociation constants differed greatly from each other. The electrical properties of 1-(4-carboxylic acid phenyl)-2,5-dimethyl-1H-pyrrole that was doped with KOH or a mixture of KOH and K 2 CO 3 were examined in detail and found to be functions of relative humidity (RH). Additionally, the effects of the salts on the sensing properties (linearity and sensitivity) were elucidated. The sensor that was made of the 1-(4-carboxylic acid phenyl)-2,5-dimethyl-1H-pyrrole/KOH/K 2 CO 3 composite film exhibited favorable impedance, high sensitivity, good linearity, small hysteresis, a short response/recovery time, a weak dependence on temperature and high long-term stability over the humidity range studied. The sensing mechanism of the 1-(4-carboxylic acid phenyl)-2,5-dimethyl-1H-pyrrole/KOH/K 2 CO 3 composite film was elucidated using impedance plots.
The 6th International Electronic Conference on Sensors and Applications, 2019
Hydrophobically modified poly(vinyl alcohol)s of varied copolymer composition were tested as active media for optical sensing of humidity. Copolymer thin films were deposited on silicon substrate using water-methanol solution in a volume ratio of 20:80 and concentration of 1 wt%. Films were subjected to low (60 °C) and moderate (180 °C) temperature annealing in order to study the temperature influence on optical and humidity sensing properties. Refractive index, extinction coefficient along with thickness of the films were determined by non-linear minimization of the goal function comprising measured and calculated reflectance spectra at normal light incidence. The humidity sensing ability of the films was studied through reflectance measurements at different humidity levels in the range 5–95 %RH. The influence of temperature annealing on optical and sensing properties was demonstrated and discussed.
Sensing Properties of Cobalt-Phthalocyanine-Based Multipurpose Sensor
Journal of Electronic Materials, 2016
Cobalt phthalocyanine (CoPc), an organic semiconductor, has been introduced as an active sensing layer in a surface-type multipurpose sensor owing to its stability, low fabrication cost, and multifunctional sensitivity. The capacitance of the sensor was recorded to increase 26.7-fold for a change in relative humidity (RH) from 0% to 92.3%, 12.6-fold for a change in illumination from 11.5 lx to 23,000 lx, and 5.2-fold for a change in temperature from 27°C to 187°C. The morphology of the active thin film of the sensor was analyzed by atomic force microscopy, revealing a rough surface favorable for moisture absorption and light harvesting. The CoPc film was amorphous in nature according to x-ray diffraction analysis. By virtue of its response to humidity, light, and temperature, this represents an attractive approach for cost-effective environmental sensing applications.
Humidity sensing and electrical properties of polyaniline/cobalt oxide composites
Journal of Applied Polymer Science, 2007
Polyaniline/cobalt oxide composites were synthesized by an in situ chemical polymerization method with ammonium persulfate as an oxidizing agent. This was a single-step polymerization process for the direct synthesis of the emeraldine salt phase of the polymer. The polymers were characterized with X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectral analysis. The formation of mixed phases of the polymer together with the conducting emeraldine salt phase was confirmed by spectroscopic techniques. High-temperature conductivity measurements showed thermally activated behavior. A change in the resistance was observed with respect to the relative humidity when the pellets were exposed to a wide humidity range of 10–95%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 653–658, 2007