Function Of Tb3 Research Articles

Preparation, patterning and luminescent properties of oxyapatite La9.33(SiO6)4O2:A(A = Eu3+, Tb3+, Ce3+)phosphor films by sol–gel soft lithography

Silicate oxyapatite La9.33(SiO6)4O2:A(A = Eu3+,Tb3+ and/orCe3+)phosphor films and their patterning were fabricated by a sol–gel process combinedwith soft lithography. X-ray diffraction(XRD), Fourier transform infraredspectroscopy, atomic force microscopy, optical microscopy and photoluminescencespectra, as well as lifetimes, were used to characterize the resulting films. The resultsof XRD indicated that the films began to crystallize at 800 °Cand the crystallinity increased with the increase in annealing temperatures.Transparent nonpatterned phosphor films were uniform and crack-free, whichmainly consisted of rodlike grains with a size between 150 and 210 nm.Patterned thin films with different bandwidths(20, 50µm) wereobtained by the micromoulding in capillaries technique. The doped rare earth ions(Eu3+, Tb3+ andCe3+)showed their characteristic emission in crystalline La9.33(SiO6)4O2phosphor films, i.e. Eu3+5D0 −−7FJ(J = 0, 1, 2, 3, 4), Tb3+5D3,4 −−7FJ(J = 3, 4, 5, 6)and Ce3+ 5d(2D)−− 4f(2F2/5,2F2/7)emissions, respectively. Both the lifetimes and PL intensity of the Eu3+, Tb3+ ionsincreased with increasing annealing temperature from 800 to 1100 °C,and the optimum concentrations for Eu3+, Tb3+were determined to be 9 and 7 mol% of La3+ in La9.33(SiO6)4O2films, respectively. An energy transfer from Ce3+ toTb3+was observed in the La9.33(SiO6)4O2:Ce,Tb phosphor films, and the energy transfer efficiency was estimated as a function of Tb3+concentration.

Luminescence and decay behaviors of Tb-doped yttrium silicate

The photoluminescence of terbium-activated yttrium silicate with the general formula Y2−XTbxSiO5 was investigated as a function of Tb3+ concentration. Especially, the main attention was focused on the 5D3 fluorescence and its energy transfer behavior. The emission and excitation spectra were measured in terms of Tb3+ concentration. The diffuse reflectance spectrum was also measured in the range from VUV to UV. As a result, yttrium silicate was found to have a broad absorption band extended from the VUV to UV range. The concentration quenching was investigated in terms of luminance and decay time both for 5D3 and 5D4 fluorescence. The energy transfer was also investigated by analyzing the decay curve of 5D3 emission on the basis of the multipolar interaction. The decay curves of 5D3 emission, for which well-known cross-relaxation has been accepted as a main factor, were analyzed by Inokuti and Hirayama's formula on the basis of the direct quenching scheme. Furthermore, the rate equations including a newly proposed quenching scheme were taken into consideration. The rate equations accept the emission quenching as due to the cross-relaxation from 5D3 or 4 to some upper levels such as 7D and the charge-transfer band.

Effect of inter-ionic interaction on photoluminescence property of yttrium aluminate garnet phosphors

The photoluminescence of Terbium-activated yttrium aluminate with the general formula Y3-xTbXAl5O12was investigated as a function of Tb3+concentration. The main attention is focused on the 5D3/5D4fluorescence and its energy transfer behavior. The emission and excitation spectra were measured in terms of Tb3+concentration and analyzed in view of the application for plasma display panel (PDP). Also, the diffuse reflectance spectra were measured and analyzed in the range from VUV to UV. As a result, the yttrium aluminate was found to have a broad excitation band extending from VUV to UV range and to show the typical concentration quenching behaviors both for 5D3and 5D4fluorescence. The energy transfer was investigated by analyzing the decay curve of 5D3and 5D4emission based on the multipolar interaction or the exchange interaction. The decay curves of 5D3emission, for which well known cross relaxation has been accepted as a main factor, were analyzed by Inokuti and Hirayama's formula based on the direct quenching scheme. The decay curves of 5D4emission were analyzed by Yokota and Tanimoto's formula based on the diffusion limited quenching scheme.

Metal-ion-binding properties of synthetic conantokin-G.

The secondary structure of the synthetic 17-residue peptide, conantokin-G (con-G), a gamma-carboxyglutamate-containing marine cone snail neuroactive protein, is altered from a random conformation to one containing a very high level (>70%) of alpha-helix on binding of multivalent cations. The proportion of alpha-helix formed correlated well with the size of the cation and ranged from a low of approx. 7% with large cations, such as Ba2+, to more than 70% with smaller cations, such as Mn2+, Mg2+ and Zn2+. The valency of the multivalent cation was not as important, since tervalent lanthanides (Eu3+, Gd3+ and Tb3+) of ionic radius 106-109 pm induced similar levels (50-60%) of helix to those induced by Ca2+ and Cd2+ (ionic radii 109 and 114 pm respectively). Although the correlation was not as tight, smaller cations of the same valency allowed the helical transition to occur at lower concentrations than the larger cations. The spectroscopic and spectrometric properties of some of these cations permitted a more detailed analysis of the molecular nature of the cation-con-G binding. EPR-based titrations with Mn2+ provided a binding isotherm that was deconvoluted to a single class of 2-3 Mn2+ sites of average Kd 3.9 microM. This number of sites was similar to that for Ca2+ [Prorok, Warder, Blandl and Castellino (1996) Biochemistry 35, 16528-16534], but a much lower Kd was displayed with Mn2+. Determinations by 1H NMR of the longitudinal relaxation rates of the water protons in Mn2+/con-G solutions at different magnetic field strengths corresponding to the proton Langmuir frequencies of 24, 300 and 500 MHz permitted calculation of the hydration number of Mn2+ in the complex, which was found to be 1.0. This indicates that five of the six co-ordination sites of Mn2+ are occupied by peptide atoms, probably oxygens. Titrations of the changes in Tb3+ fluorescence as a result of its binding to con-G gave an EC50 of 58 microM, a value nearly identical with that obtained by titration of the change in helicity of the peptide as a function of Tb3+ concentration. This shows that the macroscopic binding of Tb3+ to con-G is directly responsible for the alteration in secondary structure of the peptide. Finally, Cd2+ was found to be an extremely suitable cation for an NMR-based investigation of the amino acid residues of apo-con-G that are perturbed by cation binding. In a limited example of the results of this study, it was discovered that originally equivalent CH2(delta) protons of Arg13 became distinctly magnetically non-equivalent in the Cd2+-bound helical form of con-G. This indicates that Arg13 is situated in the helix in such a way that the mobility of its side chain is highly restricted. In conclusion, the data show that a variety of multivalent cations with measurable spectroscopic and spectrometric properties interact similarly with con-G and generate extensive alpha-helical conformation in this peptide.