Biomineralization of tellurium and selenium-tellurium nanoparticles by the white-rot fungus Phanerochaete chrysosporium

We report the electrical and optical studies of thin films of a-GaxSe100−x nanorods (x = 3, 6, 9 and 12). Thin films of a-GaxSe100−x nanorods have been synthesized thermal evaporation technique. DC electrical conductivity of deposited thin films of a-GaxSe100−x nanorods is measured as a function of temperature range from 298 to 383 K. An exponential increase in the dc conductivity is observed with the increase in temperature, suggesting thereby a semiconducting behavior. The estimated value of activation energy decreases on incorporation of dopant (Ga) content in the Se system. The calculated value of pre-exponential factor (σ0) is of the order of 101 Ω−1 cm−1, which suggests that the conduction takes place in the band tails of localized states. It is suggested that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges. On the basis of the optical absorption measurements, an indirect optical band gap is observed in this system, and the value of optical band gap decreases on increasing Ga concentration.

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Effect of Composition on Electrical and Optical Properties of Thin Films of Amorphous Ga(x)Se(100-x) Nanorods.

Field emission (FE) phenomena are generally explained in the frame-work of Fowler Nordheim (FN) theory which was given for flat metal surfaces In this work, an effort has been made to present the field emission mechanism in carbon nanotubes (CNTs) which have tip type geometry at nanoscale High aspect ratio of CNTs leads to large field enhancement factor and lower operating voltages because the electric field strength in the vicinity of the nanotubes tip can be enhanced by thousand times The work function of nanostructure by using FN plot has been calculated with reverse engineering With the help of modified FN equation, an important formula for effective emitting area (active area for emission of electrons) has been derived and employed to calculate the active emitting area for CNT field emitters Therefore, it is of great interest to present a state of art study on the complete solution of FN equation for CNTs based field emitter displays This manuscript will also provide a better understanding of calculation of different FE parameters of CNTs field emitters using FN equation

Fowler Nordheim theory of carbon nanotube based field emitters

http://eli.kau.edu.sa/Files/130/Researches/60236_31048.pdf

Characterization of Se88Te12 nanostructured chalcogenide prepared by ball milling

ZnO nanofiber (NFs) growth from ZnO nanowires (NWs) by controlling growth temperature on flexible Teflon substrate by CBD technique for UV photodetector

Se–Te nanostructured thin films were deposited on glass substrates in the presence of oxygen and argon by thermal evaporation. The properties of Se–Te thin films strongly depend on the deposition method. During the process used, the substrate is cooled to a temperature of 77 K employing liquid nitrogen. The nanostructured thin films of Se 100− x Te x (where x =4, 8 and 16) are deposited on glass substrate. The surface morphology of the deposited films was investigated through Scanning Electron Microscopy (SEM). The typical size of these nanostructures is in the range 40–100 nm and the length is of the order of several micrometers. The optical parameters i.e. optical gap ( E g ), absorption coefficient ( α ), and extinction coefficient ( k ) are calculated in the wavelength range 190–1100 nm. It was found that the optical band gap decreased from 3.4 to 2.9 eV when Te concentration was increased in the Se 100− x Te x nanostructured thin films. The large bandgap may be attributed to the decrease in particle size which clearly exhibits a quantum size effect. XRD analysis was performed to confirm glassy nature of the nanostructured thin films.

Optical properties of selenium–tellurium nanostructured thin film grown by thermal evaporation

Carbon nanotubes (CNTs) were synthesized by low-pressure chemical vapour deposition (LPCVD) using N2:C2H2:H2 gas mixtures on nanocrystalline Ni95Ti5 film. This nanocrystalline film was deposited on silicon substrate using vapour condensation method. The growth temperature and growth time was kept at 800 degrees C and 30 mins, respectively and the pressure was maintained at 10 Torr. The growth mechanism of CNTs was investigated using FESEM, TEM, HRTEM, and Raman Spectroscopy. From FESEM image of Ni95Ti5 nanocrystalline film, it is clear that the particle size varies from 5-10 nm. EDX analysis suggests that Ni95Ti5 alloy contains Ni and Ti both. It is clear from TEM images that CNTs are multiwalled with the diameter varying from 10-30 nm and length of several micrometers. HRTEM image shows that the structure of these multi-walled nanotube (MWNTs) is bamboo-shaped and the catalyst exists at the tip of MWNTs. Fourier Transform Raman Spectroscopy confirmed that graphitic structure of as-prepared CNTs. Field emission measurements reveal that the carbon nanotubes grown for 30 mins showed a turn-on field of 7.2 V/microm, when the current density achieves 10 microA/cm2. The field enhancement factor was calculated to be 708.50 for carbon nanotubes grown for 30 mins.

Synthesis of carbon nanotubes using Ni95Ti5 nanocrystalline film as a catalyst.

Multi-walled carbon nanotubes were grown on nanocrystalline Fe70Pt30 film using low-pressure chemical vapour deposition (LPCVD) method. The growth time was varied between 5 min to 30 min. SEM micrograph of this film revealed that the size of nanoparticles varied from 5 nm to 10 nm. The diameter of the carbon nanotubes varied from 20 nm to 50 nm as verified by TEM. HRTEM image confirmed that the carbon nanotubes are bamboo-shaped multiwalled carbon nanotubes (MWNTs). Field emission characteristics of MWNTs at various growth times (5 min, 15 min and 30 min) with working distances (50 µm, 100 µm and 150 µm) were also studied. The carbon nanotubes grown for 30 min with working distance 150 µm exhibited the lowest turn-on field of 2.45 V/µm. The turn-on field increases from 2.45 V/µm to 6.21 V/µm as the growth time decreases from 30 min to 5 min whereas for lower working distances (100 µm and 50 µm), the turn-on field increases from 4.74 V/µm to 6.74 V/µm and from 8.79 V/µm to 14.49 V/µm respectively. The turn...

Field emission properties of Fe70Pt30 catalysed multiwalled carbon nanotubes

Nanostructures of zinc oxide are synthesized by physical vapor condensation method From the SEM image, it is observed that these nano structures look like nanosprings mixed with nanorods The typical diameter of these nanostructures is in the range of 80-150 nm and the length is of the order of several micrometers The XRD data shows a sharp peak at 3687deg which is very close to that of zinc oxide nanorods grown by oxidation in the presence of ambient gases ie oxygen mixed with argon UV visible spectra of these nanostructures shows a peak at 371 nm and 373 nm The broad peak at 373 nm is responsible for the conversion of zinc into zinc oxide

Synthesis and characterization of ZnO nanostructures

A physical vapour condensation method is used to synthesise the nanoparticles of ZnO. The size of these nanoparticles varies from 40 nm to 100 nm. Mostly, these nanoparticles are spherical in shape but contain some impurities. The XRD data shows a sharp peak at 36.87°, which is very close to that of zinc oxide nanoparticles grown by oxidation in the presence of ambient gases i.e., oxygen mixed with argon. From UV visible spectra of these nanoparticles, a peak at 381 nm and 373 nm is observed. The broad peak at 373 nm is responsible for the conversion of zinc into zinc oxide.

Karunapati Tripathi

Papers

Optical properties of selenium–tellurium nanostructured thin film grown by thermal evaporation

Synthesis of carbon nanotubes using Ni95Ti5 nanocrystalline film as a catalyst.

Field emission properties of Fe70Pt30 catalysed multiwalled carbon nanotubes

Synthesis and characterization of ZnO nanostructures

Synthesis and characterisation of ZnO nanoparticles