H.P. Deshmukh

Multicoloured electrochromic thin films of NiO/PANI

NiO/polyaniline (PANI) thin films have been prepared by a two-step process. NiO thin films were electrodeposited from an aqueous solution of NiCl2 6H2O at pH 7.5 on fluorine-doped tin oxide coated glass substrates and a layer of PANI was formed on NiO thin films by chemical bath deposition. The films were characterized for their structural, optical, morphological and electrochromic properties. X-ray diffraction and Fourier-transform infrared spectroscopy indicated the formation of NiO and PANI, in which NiO is of cubic structure. Scanning electron micrographs represent porous granular NiO, which get uniformly carpeted with PANI, leading to a matty morphology of NiO/PANI samples. The electrochromic performance of NiO/PANI films has been studied using cyclic voltammetry and chronoamperometry over the −1.2 to +2.2 V (versus saturated calomel electrode (SCE)) potential window in 1M LiClO4 + propylene carbonate. The NiO/PANI films exhibit electrochromism with colour that changes from pale yellow (leucoemeraldine base at −0.7 V versus SCE) to dark green (emeraldine salt at 0.4 V versus SCE) to purple (pernigraniline at 0.8 V versus SCE) in the reduced states and dark blue (nigraniline at 0.5 V versus SCE) to dark green (emeraldine salt at 0.1 V versus SCE) to light green (photoemeraldine at −0.3 V versus SCE) in its oxidized states. These colours, though akin to pure PANI, have higher contrast, high speed of operation and high stability, owing to the properties of NiO. The colouration efficiency of the NiO/PANI film was estimated to be 85 cm2 C−1.

Synthesis of electrochromic vanadium oxide by pulsed spray pyrolysis technique and its properties

A new improved pulsed spray pyrolysis technique (PSPT) was employed to deposit a vanadium oxide (V2O5) thin film from a methanolic vanadium chloride precursor onto glass and conducting F : SnO2 coated glass substrates. The structural, morphological, electrical, optical and spectroscopic properties of the film deposited at 573 K were studied. Infrared spectroscopy and x-ray diffraction confirmed the presence of the V2O5 phase. The V2O5 film (thickness ~118 nm) is polycrystalline with a tetragonal crystal structure. Scanning electron microscopy reveals compact granular morphology consisting of ~80–100 nm size grains. The film is transparent in the visible region (average %T ~70%) with an optical band gap energy of 2.47 eV involving both direct and indirect optical transitions. The room temperature electrical resistivity (conductivity) of the film is 1.6 × 108 Ω cm (6.25 × 10−9 S cm−1) with an activation energy of 0.67 eV in the temperature range 300–550 K. It exhibited cathodic electrochromism in the lithium containing electrolyte (0.5 M LiClO4 + propylene carbonate).

Functionalized Multi-Walled Carbon Nanotubes for Nitrogen Sensor

Multiwalled Carbon Nanotubes (MWCNTs) produced by the arc discharge method are chemically functionalized with acid mixture. The functionalization of MWCNTs was confirmed by simple characterization techniques. This revealed that carboxylic group introduced, without disrupting main structure of MWCNTs. The gas sensing performance of the functionalized MWCNTs towards NO2 is studied. The highest sensitivity of 26.88 % for 100 ppm of NO2 at 27°C is observed towards functionalized MWCNTs. Keywords: Carbon nanotubes, Functionalization, Reflux, Response time, Carboxylation