Kumar, G A; Thomas, J; George, N; Nampoori, V P N; Radhakrishnan, P; Vallabhan, C P G(Society of Glass Technology, 2000)
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Abstract:
Optical absorption and emission spectral studies of free and metal naphthalocyanine doped borate glass matrix are reported for the first time. Absorption spectra recorded in the UV- VIS-NIR region show the characteristic absorption bands, namely, the B-band and Q-band of the naphthalocyanine (Nc) molecule. Some of the important spectral parameters, namely, the optical absorption coefficient (α), molar extinction coefficient (ε) and absorption cross section (σa) of the principal absorption transitions are determined. Optical band gap (Eg) of the materials evaluated from the functional dependence of absorption coefficient on photon energy lies in the range 1.6 eV≤Eg≤2.1 eV. All fluorescence spectra except that of EuNc consist of an intense band in the 765 nm region corresponding to the excitation of Q-band. In EuNc the maximum fluorescence intensity band is observed at 824 nm. The intensity of the principal fluorescence band is maximum in ZnNc, whereas it is minimum in H2Nc. Radiative parameters of the principal fluorescence transitions corresponding to the Q-band excitation are also reported for the naphthalocyanine and phthalocyanine based matrices.
Junaid, Bushiri M; Mahadevan Pillai, V P; Pradeep, T; Jayasree, R S; Nayar, V U(Elsevier, 1997)
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Abstract:
FTIR and Raman spectra of FeClMoO4 single crystal and polycrystalline Na2MoO4, Na2MoO4·2H2O and
Na2MoO4·2D2O are recorded and analysed. The band positions for different modes suggest that MoO4 tetrahedron
is more distorted in FeClMoO4. The larger splitting observed for the bending modes and partial retention of
degeneracy of the asymmetric stretching mode indicate that angular distortion is greater than liner distortion in
MoO4 2 ion in FeClMoO4 confirming x-ray data. The non-appearance of the n1 and n2 modes in the IR and partial
retention of the degeneracies of various modes show that MoO4 2 ion retains Td symmetry in Na2MoO4. Wavenumber
values of the n1 mode indicate that the distortion of MoO4 tetrahedra in the four crystals are in the order
FeClMoO4\ Na2MoO4·2H2O\Na2MoO4·2D2O\Na2MoO4. The water bands suggest the presence of two
crystallographically distinct water molecules in Na2MoO4·2H2O. They form strong hydrogen bonds