I.S. Mulla

Optical and photocatalytic properties of single crystalline ZnO at the air-liquid interface by an aminolytic reaction.

Crystalline flowerlike ZnO was synthesized by an aminolytic reaction at the air-liquid interface in an aqueous media at an alkaline pH. A thin visible film was formed at the air-liquid interface by self-assembly of flowerlike ZnO. Diffraction studies show rearrangement of the single crystalline units at the air-liquid interface leading to the formation of nanobelts. These nanobelts overlap systematically to form petals of the flowerlike structure; individual petals get curved with time. Each nanobelt is found to be single crystalline and can be indexed as the hexagonal ZnO phase. The organic product formed in the aminolytic reaction and dissolution-reprecipitation mechanism is the driving force for the formation of flowerlike ZnO at the air-liquid interface. A clear relationship between the surface, photocatalytic, and photoluminescent properties of ZnO is observed. The flowerlike structure exhibits a blue shift (3.56 eV) in the band emission as compared to bulk ZnO (3.37 eV). The photodegradation of methylene blue over the flowerlike ZnO catalyst formed at the air-liquid interface and in the sediments shows enhanced photocatalytic activity. The sub-bands formed due to surface defects facilitate separation of charge carriers increasing their lifetime, leading to enhanced photocatalytic activity of flowerlike ZnO.

Enhanced acetone sensing performance of nanostructured Sm2O3 doped SnO2 thick films

Abstract In the present work, we synthesized Sm 2 O 3 doped SnO 2 in order to prepare a selective acetone sensor with fast response, quick recovery and good repeatability. Pure as well as 2 mol.%, 4 mol.%, 6 mol.% and 8 mol.% Sm 2 O 3 doped SnO 2 nanostructured samples were synthesized by using a co-precipitation method. The characterization of the samples was done by thermogravimetric and differential thermo-gravimetric analysis (TG-DTA), X-ray diffraction (XRD), field emission gun-scanning electron microscopy (FEG-SEM), energy dispersive analysis by X-rays (EDAX), high resolution scanning electron microscopy (HR-TEM), selected area X-ray diffraction (SAED), Brunauer-Emmet-Teller (BET) and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy techniques. The gas response studies of liquid petroleum gas, ammonia, ethanol and acetone vapor were carried out. The results showed that Sm doping systematically lowered operating temperature and enhanced the gas response and selectivity for acetone. The response and recovery time for 6 mol.% Sm 2 O 3 doped SnO 2 thick film at the operating temperature of 250 °C were 15 and 24 s, respectively.

Organic acids assisted hydrothermal synthesis of WO 3 nanoplates and their gas sensing properties

Tungsten oxide is amongst the most widely used materials in electro-, photo-chromic applications. Recently tungsten oxide has been employed as sensing layer for detection of hazardous gases. In this work, we report synthesis of WO3 nanoparticles via a facile hydrothermal method using sodium tungstate and different organic acids (viz. citric acid, oxalic acid, malonic acid, and (L+) tartaric acid). We have investigated the effect/role of organic acid on the morphology and gas sensing properties. The X-ray diffraction (XRD) studies confirmed that citric acid and oxalic acid assisted routes give monoclinic structure (m-WO3) while malonic acid and (L+) tartaric acid give hexagonal structure (h-WO3). The nanoplate-like morphology was revealed by Scanning electron microscopy (SEM) analysis. The thick film of WO3 powder was deposited by using a screen printing technique. The gas response of thick films fired at 400°C/2h was studied. The change in the gas response of WO3 nanoplates for various concentrations and operating temperatures were studied for NOX, acetone, ethanol and ammonia vapors. In general, we observed response towards acetone, ethanol and ammonia vapors at higher operating temperature. However, the citric acid, oxalic acid and tartaric acid assisted WO3 exhibited good response for NOX at lower operating temperature (from 80°C-200°C). The gas response studies revealed that WO3 synthesized by citric acid assisted route exhibits highest sensitivity (S=77%) at 130°C towards NOX gas.

Fabrication of WO 3 /PANI nanocomposites for ammonia gas sensing application

Herein present study, organic-inorganic hybrids based on WO3/PANI nanocomposites have been synthesized at room temperature, by using oxidative polymerization. The as-synthesized products have been studied by using X-ray diffraction analysis, FE-SEM and optical characterization. The XRD analysis depicts peak broadening and the shift in peak position from standard values, which can be attributed to the formation of WO3 in the polyaniline matrix. Study of FE-SEM micrograph revealed that the cube-like WO3 particles get well dispersed in PANI matrix. WO3/PANI composite shows enhanced response and recovery time towards ammonia gas at room temperature.

Nanoflakes of β-Co(OH)2 thin film for supercapacitor application

In the present investigation, we report facile synthesis method for the large area growth of nanoflakesof β-Co(OH)2 thin film on SS substrate. The X-ray diffraction studies confimi the phase formation with brucite structure. The average thickness of the nanoflakes is about 100 nm. The electrochemical capacitive behavior of β-Co(OH)2 thin film is investigated by cyclic voltammetry in 1M KOH electrolyte and shows maximum specifie capacitance of 374 Fg−1.

α-Fe 2 O 3 nanorods: Low temperature synthesis, characterization and humidity response properties

α-Fe2O3 nanorods have been prepared at low temperature by a facile surfactant free chemical route. The advantage of this method is good composition control and homogeneity. The products were characterized using various physicochemical characterization techniques such as X-ray Diffractometry, Raman spectroscopy, UV-Visible spectroscopy and Field Emission Scanning Electron Microscopy. These powders were further studied for their humidity sensing performance. The sensors exhibited quick responses for change in the humidity. The resistance systematically varies by four orders of magnitude on exposure to humidity from 20 to 90 % RH.