Effect of Reaction Temperature on Structural and Optical Properties of CuS Nanoparticles

447-451The present study exploits the hydrothermal method to synthesize Covellite CuS nanoparticles. To optimize the synthesized nanoparticles for their application in Blue Light Emitting Diode (BLEDs), the effect of reaction temperature on their structural and optical properties was studied at 100°C, 125 °C, and 150 °C for 12h. The diffraction and morphological studies were conducted using X-Ray Diffraction and Scanning Electron Microscopy analysis, respectively. The particle size increases with the increase in reaction temperature, and the structural parameters match well with the covellite CuS hexagonal phase prepared at 125 °C. Ultraviolet-visible absorption studies reveal that the bandgap of nanoparticles was found in the range of 2.9-3.1 eV. The Photoluminescence spectroscopy and CIE chromaticity plot show that the sample synthesized at 125 °C has a low recombination rate and emits light in the blue region, suggesting that it can be utilized in devices like BLEDs and lamps

Vibrational spectra and phonon dispersion analysis of a singlewalled zigzag carbon nanotube: A first principles study

This paper reports a vibrational spectroscopic study on a zigzag singlewalled carbon nanotube (SWCNT) using first principles method based on density functional theory. The most suitable exchange correlation functional for density functional theory (DFT) analysis was determined by comparing the predicted value of band gap of the SWCNT under study with the experimental value reported in the literature. General Gradient approximation (GGA) functional in combination with revised-Perdew-Burke-Ernzerh (RPBE) sub-functional was found to give the best results. Using this optimum combination, phonon density of states and phonon dispersion curves have been determined. The analysis of results obtained focuses on symmetry considerations, group theory analysis, segregation of Raman active and IR active vibrational modes and interpretation of the Raman and IR spectra obtained. The earlier approaches on the problem rely upon zone folding technique and force constant models in which structural relaxation factor is not taken care of. An ab initio approach has been adopted by the authors in this work which is advantageous as it neither depends on some predefined parameter nor does it ignore the structural relaxation factor. The analysis of Raman spectrum reveals some additional peaks other than the commonly known RBM, D, G Gâ bands in the SWCNT spectra which have been recently reported to be observed experimentally also. Similarly, the theoretically developed IR spectrum for the simulated SWCNT is also in agreement with experimental observations. The methodology presented, thus provides a very useful novel simulation route to predict the vibrational modes, Raman spectra and IR spectra of SWCNTs theoretically.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Effect of co-doping on dielectric function spectra and static refractive indices of singlewalled carbon nanotubes: A first principles study

This paper details a density functional theory (DFT) based ab initio study on the effect of co-doping on the dielectric function spectra and refractive indices of single-walled carbon nanotubes (SWCNTs). Dielectric function spectra of a pristine (8,0) SWCNT , (8,0) SWCNT co-doped with Aluminum (Al) Phosphorus (P) , (8,0) SWCNT co-doped with Al, P and Nitrogen (N), (9,0) SWCNT doped with Al and (9,0) SWCNT co-doped with Al Boron (B) have been calculated using DFT based Cambridge sequential total energy package (CASTEP) code. Polarized and unpolarized light as well as light through polycrystalline media have been considered. Analysis involves calculation and comparison of static refractive indices of the pristine and co-doped SWCNTs. Co-doping with Al and P results in a substantial increase in the value of the static refractive index while co-doping of Al, N and P results in a reduction in the value of static refractive index though it does not fall lower than that of the pristine SWCNT. Thus, it can be concluded that co-doping with atoms of different combinations of elements can be evolved as a novel and effective tool for tuning the dielectric function and static refractive index values of SWCNTs. It will prove to be highly significant for effective designing of various sensitive optical devices using SWCNTs.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Static studies of absorption and emission spectra of acid yellow 17-An azo dye

In the present paper, the absorption and emission spectra of acid yellow 17 (C16H10Cl2N4Na2O7S2), a fluorescent azo dye, have been recorded in water at concentrations between 10-3 M and 10-6 M. This dye is used in many scientific and industrial applications. This has led to the determination of optimum concentrations to record the absorption and emission spectra of the molecule. The absorption spectrum shows three peaks at 224, 254 and 400 nm, recorded in the spectral region 200-600 nm, which have been assigned to (* ← ) 1La ←1A (primary), (* ← ) 1Lb ←1A (secondary) and (* ← n)1 W ←1A transitions, respectively. Emission spectra of the compound show four peaks at 295, 306, 412 and 437 nm corresponding to absorption peaks at 224, 254 and 400 nm. Their corresponding Stokes shifts have also been determined

Vibrational analysis of 2-chloroheptane

385-392Infrared and Raman spectra of 2-chloroheptane were recorded at ambient temperatures as pure liquid. Fundamental frequencies of 2-chloroheptane have been identified by carrying out the analysis of these spectra. Normal coordinate calculations have been made for the five probable conformations of the molecule by transferring force-constants from the studies of 2-chlorohexane. All the observed frequencies in the spectra could be assigned to the five conformations within an average frequency error ±6.4 cm-1.</span

Vibrational analysis of 1-chlorononane

679-685Fourier transform infrared and Raman spectra of the organic compound 1-chlorononane have been recorded in its liquid state at ambient temperature in the ranges 4000-400 cm-1 and 3200-150 cm-1, respectively. A detailed vibrational analysis in terms of assignment of the observed vibrational bands of 1-chlorononane has been done to different modes of vibrations for its four most probable conformations with symmetries Cs and C1 in its liquid phase with the aid of normal co-ordinate calculations. The normal co-ordinate calculations have been carried out utilizing the computer program MOLVIB. The potential energy distribution has also been calculated for each mode of vibration

Vibrational analysis of 1-chlorohexane

69-80<span style="font-size:17.0pt;mso-bidi-font-size: 14.0pt;line-height:115%;font-family:Arial;mso-fareast-font-family:Calibri; color:black;mso-ansi-language:EN-IN;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-IN">Infrared and Raman spectra of 1-chlorohexane liquid at ambient temperatures have been reported earlier. However in the absence of normal coordinate calculations. The assignments of frequencies were only tentative. A detailed analysis and assignment of the vibrational frequencies of the spectra with the aid of normal coordinate calculations for the five probable confirmations of 1-chlorohexane molecule present in the neat liquid have been reported. This has necessitated modification in many previously suggested assignments<span style="font-size:10.5pt;mso-bidi-font-size:7.5pt;line-height:115%;font-family: Arial;mso-fareast-font-family:Calibri;color:black;mso-ansi-language:EN-IN; mso-fareast-language:EN-US;mso-bidi-language:HI" lang="EN-IN">.</span