Simultaneous detection of different probe molecules using silver nanowires as SERS substrates.

Metallic silver nanowires with high yield were synthesized using a modified seed mediated approach at room temperature. Ribbon-like nanostructures were obtained when the concentration of NaOH was lower and further increase of NaOH transformed it into long nanowires. These nanowires possess high aspect ratio, with length and diameter ~6.5 µm and 17 nm respectively. The surface enhanced Raman scattering activity of these nanowires was tested with three different probe molecules viz., crystal violet, malachite green and nile blue chloride using visible (514.4 nm) and near-infrared (784.8 nm) excitation lines. The minimum detection limits for crystal violet and nile blue chloride molecules were found to be down to 10-7 M with good linear responses, as evidenced by values of correlation coefficients, indicating their potential for a variety of applications such as sensing. Principal component analysis was performed with the surface enhanced Raman spectra in order to discriminate the dye molecules and their mixture, simultaneously. The first two principal components, which provided 69.80 and 27.93% of the total data variance, could be conveniently represented as a two dimensional PCA score plot. The score plot showed clear clustering of probe molecules and their mixture. The relative contribution of wavenumbers to each of the two principal components was identified by plotting the PCA loading matrix. These results further promote possibilities of quantification of multiplexed SERS detection and analysis.

Spectroscopic and thermal analysis of a submandibular sialolith of Wharton's duct resected using Nd:YAG laser.

A sialolith observed in the Wharton's duct of a male patient was resected using an Nd:YAG laser. This is the first report on the resection of sialolith using laser. The resected sample was analyzed for structural details using Fourier transform infrared (FTIR), FT-Raman, and fluorescence spectroscopic techniques. Other techniques like energy dispersive X-ray analysis, scanning electron microscopy, and thermal analysis were also used for the analysis of structural details. The major peaks of the vibrational spectra are observed to be due to the vibrations of the phosphate and hydroxyl groups of the inorganic part of the sample and the proteinaceous component of the organic part. The major elements in the sample are identified as calcium and phosphorous in the ratio 7:3. The fluorescence spectra recorded at excitation wavelengths 280, 325, and 410 nm showed emission maxima corresponding to the endogenous fluorescence of structural proteins and amino acids. The inorganic part of the sialolith remained stable even at temperatures up to 1,673 K. The spectroscopic studies indicated that the structure of the sialolith is similar to that of the dentine part of the human teeth. In situ disintegration of the sialolith involves very high temperature. High calcium and phosphorous content in the food may be attributed to one of the reasons for the formation of sialoliths.

Vibrational spectra of mono, di and trimethyl ammonium double sulphates of rare earths Pr, Nd, Ho and Eu.

Infrared and Raman spectra of four rare earth (Ho, Eu, Nd and Pr) double sulphates have been recorded and analysed based on the vibrations of methyl ammonium cations, sulphate anions and water molecules. Formation of hydrogen bonds of the type N-H...O and O-H...O are identified in all the compounds. Bifurcated hydrogen bonds are present in the compounds with dimethyl ammonium cations. The sulphate anions are distorted and occupy a lower site symmetry in the compounds. The bands obtained for (CH(3))(2)NH(2) and SO(4)(2-) ions indicate that the structural bonding of (CH(3))(2)NH(2)Eu(SO(4))(2).H(2)O and (CH(3))(2)NH(2)Ho(SO(4))(2).4H(2)O is identical. Electronic transition bands of Eu(3+) and Nd(3+) observed in the Raman spectra of these two compounds have been identified and discussed.

Temperature dependent polarized Raman spectra of nonaaqualanthanoid (Pr) single crystal.

Polarized Raman spectral changes with respect to temperature were investigated for Pr(BrO3)3.9H2O single crystals. FTIR spectra of hydrated and deuterated analogues were also recorded and analysed. Temperature dependent Raman spectral variation have been explained with the help of the thermograms recorded for the crystal. Factor group analysis could propose the appearance of BrO3 ions at sites corresponding to C3v (4) and D3h (2). Analysis of the vibrational bands at room temperature confirms a distorted C3v symmetry for the BrO3 ion in the crystal. From the vibrations of water molecules, hydrogen bonds of varying strengths have also been identified in the crystal. The appearance upsilon1 mode of BrO3- anion at lower wavenumber region is attributed to the attachment of hydrogen atoms to the BrO3- anion. At high temperatures, structural rearrangement is taking place for both H2O molecule and BrO3 ions leading to the loss of water molecules and structural reorientation of bromate ions causing phase transition of the crystal at the temperature of 447 K.

Raman and FTIR spectra of [Cu(H2O)6](BrO3)2 and [Al(H2O)6](BrO3)3 x 3H2O.

Raman and FTIR spectra of [Cu(H2O)6](BrO3)2 and [Al(H2O)6](BrO3)3 x 3H2O are recorded and analyzed. The observed bands are assigned on the basis of BrO3- and H2O vibrations. Additional bands obtained in the region of v3 and v1 modes in [Cu(H2O)6](BrO3)2 are due to the lifting of degeneracy of v3 modes, since the BrO3- ion occupies a site of lower symmetry. The appearance v1 mode of BrO3- anion at a lower wavenumber (771 cm(-1)) is attributed to the attachment of hydrogen to the BrO3- anion. The presence of three inequivalent bromate groups in the [Al(H2O)6](BrO3)3 x 3H2O structure is confirmed. The lifting of degeneracy of v4 mode indicates that the symmetry of BrO3- anion is lowered in the above crystal from C3v to C1. The appearance of additional bands in the stretching and bonding mode regions of water indicates the presence of hydrogen bonds of different strengths in both the crystals. Temperature dependent Raman spectra of single crystal [Cu(H2O)6](BrO3)2 are recorded in the range 77-523 K for various temperatures. A small structural rearrangement takes place in BrO3- ion in the crystal at 391 K. Hydrogen bounds in the crystal are rearranging themselves leading to the loss of one water molecule at 485 K. This is preceded by the reorientation of BrO3- ions causing a phase transition at 447 K. Changes in intensities and wavenumbers of the bands and the narrowing down of the bands at 77 K are attributed to the settling down of protons into ordered positions in the crystal.

Infrared and polarized Raman spectra of (CH3)2NH2Al(SO4)2 x 6H2O.

FTIR and single crystal Raman spectra of (CH3)2NH2Al(SO4)2 x 6H2O have been recorded at 300 and 90 K and analysed. The shifting of nu1 mode to higher wavenumber and its appearance in Bg species contributing to the alpha(xz) and alpha(yz) polarizability tensor components indicate the distortion of SO4 tetrahedra. The presence of nu1 and nu2 modes in the IR spectrum and the lifting of degeneracies of nu2, nu3, and nu4 modes are attributed to the lowering of the symmetry of the SO4(2-) ion. Coincidence of the IR and Raman bands for different modes suggest that DMA+ ion is orientationally disordered. One of the H atoms of the NH2 group of the DMA+ ion forms moderate hydrogen bonds with the SO4(2-) anion. Al(H2O)6(3+) ion is also distorted in the crystal. The shifting of the stretching modes to lower wavenumbers and the bending mode to higher wavenumber suggest that H2O molecules form strong hydrogen bonds with SO4(2-) anion. The intensity enhancement and the narrowing of nu1SO4, deltaC2N and Al(H2O)6(3+) modes at 90 K confirm the settling down of the protons in the hydrogen bonds formed with H2O molecules and NH2 groups. This may be one of the reasons for the phase transition observed in the crystal.