Ground State Of Er3 Research Articles

Antibacterial activity of SnO2 in visible light enhanced by erbium–cobalt co-doping

In this work, a series of SnO2 samples with systematically varied doping amounts of Er and Co were prepared via a precipitation–hydrothermal method. The results show that after Er doping, the 4I15/2 ground state of Er3+ jumps to the 4H11/2 higher-energy level, and the Er-doped SnO2 samples can efficiently convert low-energy light into high-energy light. Thus, Er doping is beneficial for improving the visible and near-infrared light response of SnO2 and thus enhances its photocatalytic performance. Furthermore, doping SnO2 with Co leads to a distortion of the SnO2 lattice. A proportion of the SnO2 lattice is replaced by Co atoms, which can effectively lower the bandgap of SnO2, widen its optical response range, and enhance its sunlight absorption efficiency. The photocatalytic antibacterial activities of pure SnO2, as well as SnO2 co-doped with Er and Co in visible light, were investigated under visible light using Escherichia coli. SnO2 shows the best antibacterial activity and electron–hole separation efficiency when co-doped with 1.5 mol. % Er and 1.5 mol. % Co (Er1.5Co1.5-SnO2). Gradient experiments reveal that mainly the reactive oxygen species affect the antibacterial activity of pure SnO2. The improved antibacterial performance of Er1.5Co1.5-SnO2 is attributed to the increased generation of·O2− and·OH. In addition, scavenger experiments reveal that·O2− is the key contributor to the enhanced antibacterial activity of SnO2.

NIR emission and up-conversion spectral studies of Er/Yb co-doped B2O3-Bi2O3-NaF-BaF2 glasses for optical amplifiers and laser applications

Er-singly and Er/Yb-codoped oxyfluoride glasses were prepared by conventional melt-quenching technique. Structural, optical, steady-state and time-resolved spectroscopy studies were performed. The down-conversion (DC) and up-conversion (UC) mechanisms in the Er3+, Yb3+ (single) and Er3+/Yb3+ (co-doped) systems were investigated under 980 nm laser excitation and the energy transfers involved in the emissions of Er3+ and Yb3+ ions were discussed. Judd-Ofelt intensity and radiative factors such as absorption cross-section (σabs) and emission cross-sections (σemi) were evaluated and an enhanced σemi was observed for the co-doped (1 mol% Er/1 mol% Yb) glasses. Gain cross-section profiles were estimated based on σabs and σemi from McCumber theory for the 4I13/2 ↔ 4I15/2 transitions. At the same time, the studied glasses also exhibited intense UC transitions from the excited states of 2H11/2, 4S3/2, and 4F9/2 to the 4I15/2 ground state of Er3+ ions and covered the strong green and red spectral regions. Time-resolved spectroscopic measurements are extended for NIR and UC emission transitions were discussed in detail.

Spectroscopy and Judd-Ofelt analysis of Er3+ ions in Li5La3Nb2O12 garnet-type ceramic powder

The optical spectroscopy of Er3+ activated Lanthanum Lithium Niobium Garnet ceramic powder is presented. The absorption and photoluminescence spectra have been both obtained at room temperature. Emission bands related to transitions starting at 4I13/2, 4I11/2, 4F9/2, (4S3/2, 2H(2)11/2) and 2H(2)9/2 manifolds are presented. Efficient excitation of the luminescence bands is obtained under ultraviolet excitation (270 nm) using a Mercury Xenon arc lamp. The Judd–Ofelt intensity parameters of Er3+ in this garnet are calculated using the absorption spectra. The obtained results Ω2 = 7.67 × 1020 cm2; Ω4 = 0.84 × 1020 cm2; Ω6 = 0.60 × 1020 cm2 are used to calculate the radiative lifetimes of the Er3+ luminescence originated up to 4G11/2 manifolds and the branching ratios of the radiative transitions on them. The luminescence decays from the main emission lines (2H(2)11/2:4S3/2), 4I11/2, and 4I13/2 excited levels to the 4I15/2 ground state of Er3+ have also been obtained. Experimental decay time values are compared with the radiative lifetime values obtained from the Judd–Ofelt analysis.

Valley-to-peak intensity ratio thermometry based on the red upconversion emission of Er3+.

Upon 976 nm diode laser excitation, the temperature dependence of the red upconversion emission of Er3+ in CaWO4:Yb3+/Er3+ phosphor was studied from 298 to 478 K. The spectrum was verified to consist of two Stark components originating from two Stark sublevels of 4F9/2 excited state to 4I15/2 ground state of Er3+. The valley-to-peak intensity ratio (VPR) of this double-peak spectrum was found to increase linearly with the rise of temperature. The maximum relative sensitivity of this VPR method was obtained to be about 0.20% K-1 at 298 K. Moreover, a study on the power dependence was also performed, suggesting that VPR method is immune to the pump power and is thus suitable for monitoring the temperature.

Surface enhanced Raman scattering and up-conversion emission by silver nanoparticles in erbium–zinc–tellurite glass

Enhancing the up-conversion luminescence and Raman intensity in rare-earth doped glasses is an important issue for nanophotonics. Erbium-doped zinc tellurite glass with and without silver nanoparticles (NPs) were prepared using melt quenching method. The effect of NPs concentration and annealing time on the Raman and photoluminescence (PL) response were investigated. The presence of silver NPs with Gaussian size distribution having average size ∼12nm were confirmed by transmission electron microscopy. The Raman spectra consist of six peaks that show red shift. The up-conversion emission exhibits three major visible lines corresponding to the transitions from 2H11/2, 4S3/2 and 4F9/2 excited states to 4I15/2 ground state of Er3+ ion. An eight times enhancement in the Raman and five times in photoluminescence (PL) intensities were attributed to the large electric field originated from the face-centered cubic silver NPs. Quenching of PL emission in the visible range for longer annealing time interval was observed and attributed to dissolution of the growth of NPs in the host glass. The prominent absorption plasmon bands of silver were also evidenced that confirms the non-spherical shape of nanoparticles.

Optical properties of Si/Si:Er multi-nanolayer structures grown by SMBE method

Among Er-doped crystalline Si materials, Si/Si:Er multi-nanolayer structures grown by sublimation molecular beam epitaxy (SMBE) technique present extraordinary optical properties, with a narrow linewidth of the Er-related emission at 1.5 μm. Based on spectral analysis, the splitting of the ground state of Er3+ ions and the presence of only a single type of Er-related optical center, labeled Er-1, have been conclusively established. In this contribution, we briefly summarize some of the unique optical properties of Si/Si:Er multi-nanolayer structures: preferential formation of the Er-1 center and its microscopic structure, level of optical activity of Er, and relations with a donor level as well as with oxygen co-doping. Then we report on the most recent results on optical gain in Si/Si:Er multi-nanolayers. From variable stripe-length (VSL) and shifted excitation spot (SES) experiments, we estimated maximum gain cross section of Er-1 in the multi-nanolayer structure at about σ~10−17 cm2. We also evaluate the magnitude of induced absorption by free carriers, and show that it precludes observation of the net optical gain.

Room-temperature photon avalanche up-conversion in Er-doped fluoride glass and fibre pumped at 700 nm

A strong emission at 550 nm as well as a series of other wavelengths have been observed in Er-doped ZrF4-BaF2-LaF3-AlF3-NaF fibres and bulk glass at room temperature when the excitation wavelength is about 700 nm, which is far away from the absorptions from the ground state of Er3+ ions. Measurements of excitation, time delay and intensity dependence versus pump power suggest that these emissions are caused by the photon avalanche effect originating from the multiphonon side-band absorption. The excitation mechanisms of this photon avalanche have been analysed. Spectral measurement also show some strong emissions in the IR region, some features of which are probably linked with laser action.

Effect of the Er3+ Concentration on the Luminescence of Ca1-xErxF2+x Thin Films Epitaxially Grown on Si(100)

AbstractCa1-xErxF2+x thin films, with a substitution rate, x, varying from 1 to 20%, were deposited on Si(100) substrates by sublimation of high purity solid solution powders under ultra-high-vacuum. Rutherford backscattering studies have shown that the films have the composition of the initial solid solution powders, are quite homogeneous and are epitaxially grown on the substrates.The optical properties of these films were studied by means of cathodoluminescence and photoluminescence. At room temperature, the emissions due to the de-excitations from the 4S3/2, 4F9/2, 4I11/2 and 4I13/2 excited levels to the 4I15/2 ground state of Er3+ (4f11) ions are easily detected (λ = 0.548, 0.66, 0.98 and 1.53 μm)The strong 1.53 μm infrared luminescence, which presents evident potential applications for optical communications, is maximum for an erbium substitution rate included between 15 and 17%. These Er concentrations are three or four orders of magnitude greater than the optimum ones in the case of Er-doped semiconductors, which are close to 1018 cm-3. In the visible range, the luminescences are also important.They allow us to detect high energy ion or electron beams. However their maximum efficiencies were observed for a relatively low erbium concentration, close to 1%. These different behaviours are explained by the cross relaxation phenomena, which depopulate the higher levels to the benefit of the 4I13/2 → 4I15/2 transition.The energy distribution of the Stark sublevels of the 4I15/2 state, which results from crystal field splitting, was deduced from a photoluminescence study at 2K. The obtained results show that the environment of the luminescent centres does not change with the erbium concentration.At last, it must be noted that the refractive index of the layers increases with the erbium concentration, leading to the realization of optical guides. Consequently opto-electronic components could be developed from such erbium doped heterostructures.

Superconductivity and paramagnetism in ErBa2Cu3O7−y

We report detailed magnetic susceptibility and magnetization studies for the high Tc oxide superconductor ErBa2Cu3O7−y. The magnetic susceptibility χ of ErBa2Cu3O7−y follows a Curie–Weiss law both above and below Tc with the magnetic moment Peff=9.2μB, which is close to that of 9.58μB deduced from the ground state of Er3+ ion. Magnetization data at various temperatures have revealed a very large magnetic hysteresis. By analyzing the hysteretic magnetization data, we obtain the critical current density Jc(H) and the reversible magnetization Me(H) at 4.2 K. The saturation of Me in high fields at low temperature can be explained by the standard theory of paramagnetism with a Brillouin function. We find that superconductivity and paramagnetism in ErBa2Cu3O7−y exist largely independently of one another.

The specific heats of ErAg and TbAg between 0.5 and 21 K

Measurements of the specific heats of ErAg and TbAg are reported; those for TbAg are complicated by the effects of Tb2O3 impurity, but it is shown to be possible to correct for this when the correction is not too large. The main conclusions are: (i) the hyperfine specific heat of ErAg corresponds to an ionic moment of 7.6+or-0.1 mu B for Er3+; (ii) there are magnetic transitions of some complexity in ErAg in the range 10 to 18 K, and the entropy associated with them is close to R in 4, confirming that the crystal-field ground state of Er3+ is Gamma 8(3); (iii) the electronic specific heat coefficients of ErAg and TbAg are 11+or-1 and 7.5+or-0.5 mJ K-2 mol-1; (iv) the hyperfine specific heat of TbAg appears to be anomalously large.