B. T. Raut

Polypyrrole Thin Film: Room Temperature Ammonia Gas Sensor

Polypyrrole thin films were synthesized in situ by chemical polymerization. The morphological studies by Scanning Electron Microscopy showed formation of uniform granular structure with average grain size of 0.6 μm. Fourier transform infrared spectroscopy revealed formation of polypyrrole. The film composition was also characterized by UV-Vis Spectroscopy. These films were investigated for their sensing behavior towards NH3, C2H5OH and CH3OH gases at room temperature. It has been observed that these films are selective for ammonia gas, and the sensitivity exhibited a linear response in range of 5-100 ppm. These studies show that polypyrrole films can be used as room temperature ammonia sensors.

Structural, Morphological, Optical, and Electrical Properties of PANi-ZnO Nanocomposites

Thin films of polyaniline (PANi) and PANi–Zinc oxide (ZnO) nanocomposites have been synthesized by a spin-coating technique. The ZnO powder of particle size 50–60 nm was synthesized by sol–gel technique and the polyaniline was synthesized by chemical oxidative polymerization of aniline. The nanocomposite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), UV–Vis spectroscopy, and four probe technique, and the results were compared with polyaniline films.

Room Temperature Ammonia Gas Sensor Based on Polyaniline-TiO

In the present work, we report on the performance of room temperature ammonia gas sensor based on polyaniline-titanium dioxide (PANi-TiO2) nanocomposite. The nanocomposite was fabricated using the spin coating method on glass substrates. PANi-TiO2 (0%-50%) nanocomposite films were characterized for their structural as well as surface morphologies, UV-Vis and various gas responses were studied. The XRD analysis showed formation of nanocrystalline TiO2, while polyaniline exhibited amorphous nature. Morphological analysis using scanning electron microscopy of PANi-TiO2 nanocomposite film revealed uniform distribution of TiO2 nanoparticles in PANi matrix. The absorption peaks in FTIR and UV-Vis spectra of PANi-TiO2 composite film were found to shift to a higher wave number as compared to those observed in pure PANi. The observed shifts were attributed to the interaction between the TiO2 particle and PANi molecular chains. The gas sensing properties showed the sensor exhibit selectivity to ammonia (NH3) at room temperature.

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The polyaniline-titanium dioxide (PANi-TiO₂) nanocomposite was prepared from PANi, and TiO₂, which were synthesized by oxidative chemical polymerization and sol gel methods, respectively. Nanocomposites of PANi- TiO₂ were doped with Camphor Sulfonic Acid (CSA) with concentrations as high as 50 wt%. The composites obtained (PT CSA) were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). The CSA doped PANi-TiO₂ thin-film sensors were prepared by the sol gel spin coating technique. The sensitivity measurements were carried out for ammonia (NH₃), ethanol (C₂H₅-OH), methanol (CH₃-OH), nitrogen dioxide (NO₂) and hydrogen sulfide (H₂S) gases, and it was found that the sensor exhibited selectivity to NH₃. The effect of varying doping percentage on response to varying NH₃ concentration was also studied. The result showed increasing response of sensor when NH₃ concentration was changed from 20 to 100 ppm. It was also found that, the sensor exhibited smaller response time and larger response magnitude but at the cost of longer recovery time.

Nanocomposite

A nanocomposite of polyaniline-titanium dioxide (PANi-TiO2, 50 wt%) was doped with camphor sulfonic acid (CSA) by solid state reaction with increasing CSA content up to 50 wt% in a smooth agate mortar. CSA doped PANi-TiO2 was dissolved in m-cresol and films were cast using a spin-coating technique. The doping effect of CSA on PANi-TiO2 nanocomposite was characterized and evaluated by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and electrical conductivity measurement. The XRD spectra showed that the addition of CSA has no effect on crystallinity of PANi-TiO2. SEM studies revealed that CSA has a strong effect on morphology of PANi-TiO2. The FTIR spectra revealed the interaction between CSA and PANi-TiO2 nanocomposite. Electrical conductivity measurements indicated that with the increasing content of CSA, the conductivity shows an orderly increase.

New Method for Fabrication of CSA Doped PANi-

Nanocrystalline copper oxide (CuO) thin films were deposited onto glass substrates by a spin coating technique using an aqueous solution of copper acetate. These films were characterized for their structural, mor-phological, optoelectronic properties by means of X-ray diffraction (XRD) scanning electron microscopy (SEM), UVspectroscopy and four probe method. The CuO films are oriented along (1 1 1) plane with the monoclinic crystal structure. These films were utilized in H2S sensors. The dependence of the H2S response on the operating temperature, H2S concentration of CuO film (annealed at 700。C) was investigated. The CuO film showed selectivity for H2S. The maximum H2S response of 25.2 % for the CuO film at gas concentra-tion of 100 ppm at operating temperature 200oC was achieved.

{\rm TiO}_{2}

Nanocrystalline titanium oxide thin films have been deposited by spin coating technique and then have been analyzed to test their application in NH3 gas-sensing technology. In particular, spectrophotometric and con-ductivity measurements have been performed in order to determine the optical and electrical properties of titanium oxide thin films. The structure and the morphology of such material have been investigated by X ray diffraction, Scanning microscopy, high resolution electron microscopy and selected area electron diffrac-tion. The X-ray diffraction measurements confirmed that the films grown by this technique have good crys-talline tetragonal mixed anatase and rutile phase structure The HRTEM image of TiO2 thin film showed grains of about 50-60 nm in size with aggregation of 10-15 nm crystallites. Selected area electron diffraction pattern shows that the TiO2 films exhibited tetragonal structure. The surface morphology (SEM) of the TiO2 film showed that the nanoparticles are fine The optical band gap of TiO2 film is 3.26 eV. Gas sensing proper-ties showed that TiO2 films were sensitive as well as fast in responding to NH3. A high sensitivity for ammo-nia indicates that the TiO2 films are selective for this gas.

Thin-Film Ammonia Sensor

Films of polyaniline (PANi) and PANi‐ ZnO nanocomposites have been synthesized by spin coating technique. Fourier transform infrared and UV‐Vis spectroscopic studies of PANi and PANi‐ ZnO nanocomposite films indicated the presence of interaction between nano ZnO particles and molecular chains of PANi. The resistivity measurement shows that molecular chain constitution of polyaniline is the most important carrier in polyaniline‐ nano‐ZnO composite.

Camphor Sulfonic Acid Doped Polyaniline-Titanium Dioxide Nanocomposite: Synthesis, Structural, Morphological, and Electrical Properties

The polypyrrole-zinc oxide (PPy-ZnO) hybrid sensor doped with different weight ratios of camphor sulphonic acid (CSA) were prepared by spin coating technique. These CSA doped PPy-ZnO hybrids were characterized by field emission scanning electron microscope (FESEM) and fourier transform infrared (FTIR) which proved the formation of polypyrrole, PPy-ZnO and the interaction between polypyrrole – ZnO (PPy-ZnO) hybrid with CSA doping. The gas sensing properties of the PPy-ZnO hybrid films doped with CSA have been studied for oxidizing (NO2) as well as reducing (H2S, NH3, CH4OH and CH3OH) gases at room temperature. We demonstrate that CSA doped PPy-ZnO hybrid films are highly selective to NO2 along with high-sensitivity at low concentration (80% to 100 ppm) and better stability, which suggested that the CSA doped PPy-ZnO hybrid films are potential candidate for NO2 detection at room temperature.