Structural, optical and sensing properties of pure and Cu-doped SnO2 nanowires.

In present work, pure and copper (Cu) doped SnO2 nanowires have been synthesized by thermal evaporation process at ambient pressure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated the growth of wire-like pure and Cu-doped SnO2 nanostructures with their length of about 50 microm and 80 microm whereas transverse dimension of about 50-80 nm and 20-50 nm, respectively. The HRTEM and SAED pattern reveals the growth of single crystalline Cu-doped SnO2 nanowire. The EDX confirms that Cu has been doped in the SnO2 nanowires and atomic fraction of Cu in nanowires is about 2.5 at% when concentration of CuO in starting source powder is 50 wt%. X-ray diffraction showed that Cu gets incorporated into the SnO2 lattice and also confirms their tetragonal rutile structure. For comparative study of gas sensing properties of pure and Cu-doped SnO2 nanowire, isolated single nanowire based sensors have been fabricated for detection of ethanol gas. The doping of Cu was found to enhance the ethanol sensitivity of SnO2 nanowire based sensors and the sensor response improves with increase in ethanol concentration. This sensing behaviour offers a suitable application of the Cu-doped SnO2 nanowire sensor for detection of ethanol gas.

Effect of substrates on structural and optical properties of tin oxide (SnO2) nanostructures.

We report on controlling the morphology of tin oxide (SnO2) nanostructures and the study of the effect of surface morphology on structural and optical properties of SnO2 nanostuctures. In present work, Tin oxide (SnO2) nanostructures such as nanowires and nanorods have been grown by thermal evaporation of SnO2 powder. To demonstrate the effect of different substrates on the morphology of grown SnO2 nanostructures, the thermal evaporation of SnO2 powder was carried out on Si and gold catalyzed Si (Au/Si) substrates. The scanning-electron-microscopic analysis shows the growth of SnO2 nanowires on Au/Si substrate and growth of SnO2 nanorods on Si substrate. The scanning-and transmission-electron-microscopic analysis shows that the diameter of SnO2 nanowires and nanorods are about 70 nm and 95 nm respectively and their length is about 80 microm and 30 microm respectively. The vapor-liquid-solid (VLS) growth of SnO2 nanowires and vapor-solid (VS) growth of SnO2 nanorods is also confirmed with the help of TEM and EDX spectra. The synthesized SnO2 nanowires show tetragonal rutile structure of SnO2, whereas SnO2 nanorods show tetragonal rutile as well as cassiterite structure of SnO2. UV-Vis absorption spectra showed the optical band gaps of 4.1 eV and 3.8 eV for the SnO2 nanowires and the nanorods, respectively. The SnO2 nanowires and nanorods show photoluminescence with broad emission peaks centred at around 600 nm and 580 nm respectively. Raman spectra of SnO2 nanowires shows three Raman shifts (478, 632, 773 cm(-1)) corresponding to Eg, A1g and B2g vibration modes, whereas in Raman spectra of SnO2 nanorods, A1g peak is dramatically reduced and the B2g mode is totally quenched.

Anti-malarial activity of some xanthones isolated from the roots of Andrographis paniculata.

Four xanthones were isolated from the roots of Andrographis paniculata using a combination of column and thin-layer chromatographic methods. They were characterized as (i) 1,8-di-hydroxy-3,7-dimethoxy-xanthone, (ii) 4,8-dihydroxy-2,7-dimethoxy-xanthone, (iii) 1,2-dihydroxy-6,8-dimethoxy-xanthone and (iv) 3,7,8-trimethoxy-1-hydroxy xanthone by IR, MS and NMR spectroscopic methods. In vitro study revealed that compound 1,2-dihydroxy-6,8-dimethoxy-xanthone possessed substantial anti-plasmodial activity against Plasmodium falciparum with its IC(50) value of 4 microg ml(-1). Xanthones bearing hydroxyl group at 2 position demonstrated most potent activity while xanthones with hydroxyl group at 1,4 or 8 position possessed very low activity. In vivo anti-malarial sensitivity test of this compound on Swiss Albino mice with Plasmodium berghei infection using Peters' 4-day test gave substantial reduction (62%) in parasitaemia after treating the mice with 30 mg kg(-1) dose. In vitro cytotoxicity against mammalian cells revealed that 1,2-dihydroxy-6,8-dimethoxy-xanthone is non-cytotoxic with its IC(50) > 32 microg ml(-1).

Adenosine triphosphatase activity in few tissues of a fresh water teleost, Channa gachua following in vivo exposure to endosulfan.

Fresh water teleost fish, Channa gachua, were chronically exposed to various sublethal concentrations of endosulfan (0.00534, 0.00355, 0.00213 and 0.00174 mg/1) at 25 +/- 4 degrees C for 30 and 60 days respectively. The study shows enzyme inhibitions, greatest in oligomycin-insensitive Mg2+ ATPase in brain, gill and liver tissues, with pronounced effects at highest endosulfan concentration for 60 days exposure. However, in kidney the highest inhibition was of oligomycin-sensitive (mitochondrial) Mg2+ ATPase. The study indicates that endosulfan interferes with energy metabolism in vivo. The marked sensitivity of mitochondrial Mg2+ ATPase to endosulfan is suggestive of the potential for endosulfan to interfere markedly with various energy requiring processes in the fish body.