P.P. Patil

Highly sensitive and fast responding CO sensor based on Co3O4 nanorods

Co(3)O(4) nanorods (diameters approximately 6-8 nm and lengths approximately 20-30 nm) were synthesized for the first time through a simple co-precipitation/digestion method by calcination of cobalt hydroxyl carbonate in air and their CO gas sensing properties were investigated. The Co(3)O(4) nanorods exhibited outstanding gas sensing characteristics such as, higher gas response (approximately 6.55-50 ppm CO gas at 250 degrees C), extremely rapid response (approximately 3-4s), fast recovery (approximately 5-6s), excellent repeatability, good selectivity and lower operating temperature (approximately 250 degrees C). Furthermore, the Co(3)O(4) nanorods are able to detect up to 5 ppm for CO with reasonable sensitivity (approximately 3.32) at an operating temperature 250 degrees C and they can be reliably used to monitor the concentration of CO over the range (5-50 ppm). The experimental results clearly demonstrate the potential of using the Co(3)O(4) nanorods as sensing material in the fabrication of CO sensors. Plausible CO sensing mechanism of the Co(3)O(4) nanorods is also discussed.

Acetone vapor sensing properties of screen printed WO3 thick films

This paper presents acetone vapor sensing properties of WO(3) thick films. In this work, the WO(3) thick films were prepared by standard screen-printing method. These films were characterized by X-ray diffraction (XRD) measurements, and scanning electron microscopy (SEM). The acetone vapor sensing properties of these thick films were investigated at different operating temperature and acetone vapor concentrations. The WO(3) thick films exhibit excellent acetone vapor sensing properties with the maximum sensitivity approximately 456% at 300 degrees C in air atmosphere with fast response and recovery time.

Synthesis and LPG sensing properties of nano-sized cadmium oxide.

This paper reports the synthesis and liquid petroleum gas (LPG) sensing properties of nano-sized cadmium oxide (CdO). The nano-sized CdO powder was successfully synthesized by using a chemical co-precipitation method using cadmium acetate and the ammonium hydroxide, as starting materials and water as a carrier. The resulting nano-sized powder was characterized by X-ray diffraction (XRD) measurements and the transmission electron microscopy (TEM). The LPG sensing properties of the synthesized nano-sized CdO were investigated at different operating temperatures and LPG concentrations. It was found that the calcination temperature and the operating temperature significantly affect the sensitivity of the nano-sized CdO powder to the LPG. The sensitivity is found to be maximum when the calcination temperature was 400 degrees C. The sensitivity to 75ppm of LPG is maximum at an operating temperature 450 degrees C and it was found to be approximately 341%. The response and recovery times were found to be nearly 3-5s and 8-10s, respectively. The synthesized nano-sized CdO powder is able to detect up to 25ppm for LPG with reasonable sensitivity at an operating temperature 450 degrees C and it can be reliably used to monitor the concentration of LPG over the range (25-75ppm). The experimental results of the LPG sensing studies reveal that the nano-sized CdO powder synthesized by a simple co-precipitation method is a suitable material for the fabrication of the LPG sensor.

Anticorrosive properties of electrosynthesized poly(o-anisidine) coatings on copper from aqueous salicylate medium

Poly(o-anisidine) (POA) coatings were electrosynthesized on copper (Cu) from an aqueous solution containing o-anisidine and sodium salicylate by using cyclic voltammetry, galvanostatic and potentiostatic modes. The extent of corrosion protection offered by these coatings to Cu in aqueous 3% NaCl solution was evaluated by the open circuit potential measurements, potentiodynamic polarization technique and electrochemical impedance spectroscopy. Potentiodynamic polarization and electrochemical impedance spectroscopy studies reveal that the POA acts as a protective layer on Cu against corrosion in 3% NaCl solution. The positive shift in the corrosion potential for the POA-coated Cu indicates the protection of the Cu surface by the POA. The POA coating synthesized by using cyclic voltammtery, galvanostatic and potentiostatic modes reduces the corrosion rate of Cu almost by a factor of 100, 100 and 7, respectively. The cyclic voltammetry was proved to be the better mode to adopt for the synthesis of more compact and strongly adherent POA coatings on Cu. The coatings synthesized by this mode were characterized by cyclic voltammetry, UV–visible absorption spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. It was found that the electrochemical polymerization of o-anisidine on Cu takes place after the passivation of its surface via the formation of Cu2O and/or copper salicylate complex and results in the generation of shiny, uniform and strongly adherent POA coatings. The optical absorption spectroscopy reveals the formation of the emeraldine salt form of POA. The results of this study clearly ascertain that the POA has outstanding potential to protect Cu against corrosion in a chloride environment.

Electrochemical synthesis of corrosion protective polyaniline coatings on mild steel from aqueous salicylate medium

Abstract Strongly adherent polyaniline coatings were electrochemically synthesized on mild steel from an aqueous salicylate medium. These coatings were characterized by cyclic voltammetry, UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy. The extent of the corrosion protection offered by polyaniline coatings to mild steel was investigated in aqueous 3% NaCl solution, 0.01 M Na2SO4 solution and in aqueous solutions of NaCl+Na2SO4 with different concentrations by potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results of these studies reveal that the corrosion resistance of the polyaniline-coated mild steel is significantly higher and the corrosion rate is considerably lower than that of uncoated steel.

Electrochemical polymerization of poly(o-anisidine) thin films: effect of synthesis temperature studied by cyclic voltammetry

The effect of temperature on the electrochemical synthesis of poly(o-anisidine) (POA) thin films has been investigated. The POA films were synthesized electrochemically under cyclic voltammetric conditions in aqueous solutions of H2SO4 at various temperatures between -6°C and 40°C. These films were characterized by cyclic voltammetry (CV), UV–visible spectroscopy and scanning electron microscopy (SEM). It has been found that the rate of polymer formation depends on the synthesis temperature and is highest at 15°C. The optical absorption spectra indicate a major peak at about 800nm and a shoulder at about 440nm independent of the synthesis temperature. The peak at about 800nm corresponds to the presence of the emeraldine salt phase of POA, while the latter may be attributed to the formation of radical cations. The absorbance and width of the peak at about 800nm is observed to increase at low synthesis temperatures. The POA film synthesized at 15°C shows predominant formation of the emeraldine salt phase of POA. The surface morphology as revealed by SEM, is observed to depend on the synthesis temperature, and is caused by different rates of polymer formation at different temperatures.

High performance H2 sensor based on ZnSnO3 cubic crystallites synthesized by a hydrothermal method

Zinc stannate (ZnSnO3) cubic crystallites have been successfully synthesized by hydrothermal reaction at 140°C. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) have been employed to characterize the crystal structure and morphology of the as-synthesized ZnSnO3. The ZnSnO3 cubic crystallites exhibited selective sensing performance towards H2 in terms of higher gas response, rapid response-recovery, repeatability and relatively lower operating temperature. This experimental result demonstrates that the synthesized ZnSnO3 cubic crystallites have noteworthy H2 sensing characteristics which make them a promising material for the fabrication of high performance H2 sensor.

Influence of supporting electrolyte on the electrochemical synthesis of poly(o-methoxyaniline) thin films

Abstract The influence of supporting electrolyte on the electrochemical, optical and morphological properties of poly( o -methoxyaniline) (POMA) thin films has been investigated. The POMA films were synthesized electrochemically under cyclic voltammetric conditions in aqueous solutions of HCl, H 2 SO 4 , HNO 3 and HClO 4 at room temperature. These films were characterized by cyclic voltammetry, UV–visible spectroscopy and scanning electron microscopy (SEM). It was observed that the rate of polymerization is strongly influenced by the size and type of the anion present in the electrolyte. The optical absorption spectra reveal the formation of the conducting emeraldine salt phase irrespective of the electrolyte used. It was found that the size and type of the anion present in the electrolyte also affect the surface morphology of the POMA films.

Growth of poly(2,5-dimethoxyaniline) coatings on low carbon steel

Abstract Poly(2,5-dimethoxyaniline) (PDMA) coatings on low carbon steel (LCS) substrates have been grown by the electrochemical polymerization (ECP) of 2,5-dimethoxyaniline (DMA). The ECP was carried out in an aqueous solution of oxalic acid at room temperature under galvanostatic conditions. Uniform, strongly adherent dark green PDMA coatings were obtained on LCS substrates. These coatings were characterized by potential–time (E–t) curves, UV-visible absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). It has been found that the oxalic acid is a suitable medium for the ECP of DMA on the LCS substrate and the electrochemical growth process is characterized by three distinct stages-induction time for ECP of DMA, complete passivation of LCS electrode surface and decomposition of the interphase followed by the ECP of DMA. The induction time is observed to decrease with increase in the applied current density. The optical absorption spectroscopy study reveals the exclusive formation of emeraldine salt (ES) phase of PDMA at lower current density whereas at higher current density coating constitutes the mixed phase of emeraldine base (EB) and ES. The FTIR spectroscopy indicates that the formation of PDMA coating. The surface morphology of PDMA coating is observed to depend on the applied current density and it improves with the increase in the current density.

Electrochemical synthesis of poly(O-methoxyaniline) thin films: effect of post treatment

The influence of post treatments on the optical absorption, morphology and electrical conductivity of galvanostatically synthesized poly(O-methoxyaniline) (POMA) thin films has been investigated. For post treatment studies, the films were treated with distilled water, supporting electrolyte and NaOH. With water treatment, the optical absorption spectrum shows the formation of pernigraniline base (PB) along with emeraldine salt (ES) phase of POMA, whereas the supporting electrolyte treatment does not indicate any major changes except decrease in the overall absorbance level with the simultaneous increase in the sharpness of the peak at ∼780 nm as compared to the as-deposited films. After the NaOH treatment, the spectrum exhibits significant changes and shows a single well-defined peak at ∼540 nm corresponding to the PB. The Fourier transform infrared (FTIR) spectra exhibit systematic spectral changes with the post treatments. The FTIR spectroscopic study reveals the formation of PB upon NaOH treatment and supports the optical absorption spectroscopy results. It is found that the post treatments affect the electrical conductivity. The surface morphology of the films is also strongly influenced by the post treatments.