'Spillout' effect in gold nanoclusters embedded in c-Al2O3(0001) matrix

Gold nanoclusters are grown by 1.8 MeV Au^\sup{2+} implantation on c-Al\sub{2}O\sub{3}(0001)substrate and subsequent air annealing at temperatures 1273K. Post-annealed samples show plasmon resonance in the optical (561-579 nm) region for average cluster sizes ~1.72-2.4 nm. A redshift of the plasmon peak with decreasing cluster size in the post-annealed samples is assigned to the 'spillout' effect (reduction of electron density) for clusters with ~157-427 number of Au atoms fully embedded in crystalline dielectric matrix with increased polarizability in the embedded system.Comment: 14 Pages (figures included); Accepted in Chem. Phys. Lett (In Press

Laser-Raman spectroscopic studies on graphite from East Antarctica

We report here the Laser-Raman spectroscopic data on the carbonaceous matter (CM) from Schirmacher Oasis (70°45\u27S, 11°40\u27E), East Antarctica for the first time. The sample was collected from the Precambrian rock, which consists of garnet-biotite gneiss. The first order Laser-Raman spectra of the sample shows a strong well-ordered Raman peak (0) at 1581 cm^ and a weak broad peak due to disorder (D) at 1354 cm^. The intensity ratio disordered-to-ordered Raman peak (D/O)_ has been used to estimate the in-plan crystallite size (L_a) of the graphite. The experimental values of D/0=0.143 and D/D+O=0.125 indicate that the CM is well crystallized graphite, thereby indicating the high metamorphic grade of the host rocks. Powder X-ray diffraction studies on the same sample of CM also indicate that the CM is well-crystalline hexagonal graphite with d_=0.3354 nm. The structural parameters obtained by Raman spectroscopic method and the estimated in-plane crystallite size (L_a=298A) indicate that the metamorphic grade of the host rock of the studied sample falls in the upper sillimanite zone. The present study suggests that the peak metamorphic temperature of the host rock could be in the temperature range of about 700℃

Re-examination of high pressure orthorhombic-I phase of ZrO

Currently there is ambiguity about the space group of the first high pressure phase of ZrO2. Early Raman spectroscopic measurements on a single crystal in a diamond anvil cell pointed to a structural transformation at 3.5 GPa, and later in-situ X-ray diffraction studies concluded that this structure is orthorhombic with space group Pbcm. From a subsequent analysis of neutron diffraction patterns of ortho-I phase quenched from 6 GPa and 600 °C it was concluded that the space group of this phase is Pbca and not Pbcm. We have re-investigated this using Raman spectroscopy and factor group analysis, and show that the space group indeed is Pbcm and not Pbca