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1.
The electron paramagnetic resonance (EPR) spectra of Ce3+ and Nd3+ impurity ions in unoriented powders of the YBa2Cu3O6.13 compound are observed and interpreted for the first time. It is demonstrated that, upon long-term storage of the samples
at room temperature, the EPR signals of these ions are masked by the spectral line (with the g factor of approximately 2) associated with the intrinsic magnetic centers due to the significant increase in its intensity. 相似文献
2.
In this paper, the green synthesis of fluorescent carbon dots (CDs) via one-step hydrothermal treatment of cornstalk was investigated. This approach is facile, economical, and effective. The obtained CDs with an average diameter of 5.2 nm possess many excellent properties such as emitting blue fluorescence under UV light (365 nm), high monodispersity, good stability, excellent water dispersibility, and absolute quantum yield of 7.6%. Then, these CDs were used as sensing probes for the detection of Fe2+ and H2O2 with detection limits as low as 0.18 and 0.21 μM, respectively. This sensing platform shows advantages such as high selectivity, good precision, rapid operation, and avoiding the precipitation of iron oxyhydroxides. 相似文献
3.
We have studied the effect of doping with Eu2+ and Ce3+ ions on the photoluminescence (PL) of BaGa2Se4 crystals in the temperature range 77–300 K. We have established that the broad bands with maxima at wavelengths 456 nm and
506 nm observed in the photoluminescence spectra of BaGa2Se4:Ce3+ crystals are due to intracenter transitions 5d → 2F7/2 and 5d →2F5/2 of the Ce3+ ions, while the broad photoluminescence band with maximum at 521 nm in the spectrum of BaGa2Se4:Eu2+ is associated with 4f6 5d → 4f7 (8S7/2) transitions of the Eu2+ ion. We show that in BaGa2Se4:Eu2+,Ce3+ crystals, excitation energy is transferred from the Ce3+ ions to the Eu2+ ions. 相似文献
4.
High-frequency broad-band (65–240 GHz) EPR is used to study impurity centers of bivalent chromium in a CdGa2S4 crystal. It is found that the EPR spectra correspond to tetragonal symmetry. The spin Hamiltonian H = βB · g · S + B 2 0 O 2 0 + B 4 0 O 4 0 + B 4 4 O 4 4 with the parameters B 2 0 =23659±2 MHz, B 4 0 =1.9±1 MHz, |B 4 4 |=54.2±2 MHz, g‖=1.93±0.02, and g⊥=1.99±0.02 is used to describe the observed spectra. It is concluded that chromium ions occupy one of the tetrahedrally coordinated cation positions. 相似文献
5.
The emission and excitation spectra of Gd2SiO5∶Eu3+ were investigated using the VUV beam line of the Beijing Synchrotron Radiation Facility (BSRF). The experimental results
were discussed in the frame of visible quantum cutting process involved in Gd3+−Eu3+ system. Upon direct excitation into the6G
J
states of Gd3+, two visible photon emissions from Eu3+ were observed. Cursory evaluation proved that Gd2SiO5∶Eu3+ is an efficient visible quantum cutter. 相似文献
6.
Q. Zhang J. Wang M. Zhang W. Ding Q. Su 《Applied Physics A: Materials Science & Processing》2007,88(4):805-809
The effect of compensator on optical properties of Ca2Al2SiO7:Eu3+ is systematically investigated by the X-ray powder diffraction, photo-luminescence (PL) properties and lifetime. It is obviously
observed that the PL intensity of Eu3+ under 394 nm excitation increases in the order of Ca1.86Eu0.14Al2SiO7 (CAS), Ca1.72Na0.14Eu0.14Al2SiO7 (CASNa) and Ca1.86Eu0.14Al2.14Si0.86O7 (CASAl), the intensity of Eu3+ are 100%, 134%, 184%, and the lifetime of Eu3+ are 0.75 ms, 1.28 ms and 1.39 ms, respectively. A charge compensation model is proposed to explain the changes in the emission
intensity and lifetime of Eu3+ in Ca2Al2SiO7 with different compensation methods.
PACS 78.55.-m; 61.72.Ji; 61.43.Gt; 42.70.-a; 74.62.Dh 相似文献
7.
Terbium silica hybrid material with imidazole ring that can be emissive in water has been designed and showed host-guest interactions
with specific ions (cations and anions). In detail, we studied the sensing abilities of this material by addition of the anions
H2PO4-, HSO4-, F-, Cl-, Br- and I- to water suspension of the derived powders. Only dihydrogen phosphate resulted in the quenching of the lanthanide luminescence
(detection limit 10-5 M). The same way was found in Cu2+ ions which also gave rise to luminescence quenching (detection limit 10-5 M). More interestingly, luminescent sol-gel films were successfully prepared by the same materials and exhibited emission
responses to H2PO4- and Cu2+. For the sake of improving its mechanical property, the robust and flexible inorganic/PMMA hybrid material with sensing capability
was also developed for future use. 相似文献
8.
S. Kang Y.-M. Liu T.-Y. Shi 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(1):37-42
The energy spectra of H2
+-like impurities confined in
finite spherical quantum dots have been calculated as a function
of the distance between nuclear with different sizes on the basis
of effective-mass approximation by linear variational method.
B-splines have been used as basis functions, which can easily
construct the trial wavefunctions with appropriate boundary and
cusp conditions. The quantitative analyses of the partial wave
weights for ground state and some low lying states have been done. 相似文献
9.
A Cu2+-doped single crystal of catena-trans-bis(N-(2-hydroxyethyl)-ethylenediamine) zinc(II)-tetra-m-cyanopaladate(II) [ZnPd(CN)4(C4H12N2O2)] complex has been investigated by electron paramagnetic resonance (EPR) technique at room temperature. EPR spectra indicate
that Cu2+ ions substitute for magnetically equivalent Zn2+ ions and form octahedral complexes in [ZnPd(CN)4(C4H12N2O2)] hosts. The crystal field affecting the Cu2+ ion is nearly axial. The optical absorption studies show two bands at 322 nm (30864 cm−1) and 634 nm (15337 cm−1) which confirm the axial symmetry. The spin Hamiltonian parameters and the relevant wave function are determined. 相似文献
10.
K. A. Petrovykh V. S. Kortov N. V. Gaponenko A. A. Rempel’ M. V. Rudenko L. S. Khoroshko S. S. Voznesenskii A. A. Sergeev V. A. Pustovarov 《Physics of the Solid State》2016,58(10):2062-2067
The photoluminescence properties of a composite material prepared by the introduction of the nanosized phosphor Zn2SiO4:Mn2+ into porous anodic alumina have been investigated. Scanning electron microscopy studies have revealed that Zn2SiO4:Mn2+ particles are uniformly distributed in 70% of the volume of the pore channels. The samples exhibit an intense luminescence in the range of 2.3–3.0 eV, which corresponds to the emission of different types of F centers in alumina. After the formation of Zn2SiO4:Mn2+ nanoparticles in the pores, an intense photoluminescence band is observed at 2.4 eV due to the 4T1–6A1 electronic transition within the 3d shell of the Mn2+ activator ion. It has been found that the maximum of the photoluminescence of Zn2SiO4:Mn2+ xerogel nanoparticles located in the porous matrix is shifted to higher energies, and the luminescence decay time decreases significantly. 相似文献
11.
N. V. Znamenskiy T. G. Yukina Yu. V. Malyukin P. N. Zhmurin Yu. N. Velikhov 《Laser Physics》2007,17(4):491-495
For the fist time in Y2SiO5:Pr3+ nanocrystals, the ordered stage in the 1 D 2 luminescence decay curves for Pr3+ ions has been observed at anomalously low doped ion concentration (0.5 at %). This effect is caused by preferred location of the activator ions in the near-surface layer of the nanocrystal that provides the relaxation of elastic tension arising due to the difference of ionic radii of Pr3+ and Y3+ ions. Concentration quenching of Pr3+ luminescence is caused by the cooperative cross-relaxation. 相似文献
12.
V. S. Kortov K. A. Sergeeva V. A. Pustovarov A. A. Rempel 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2017,11(4):727-731
The photoluminescence of Zn2SiO4:Mn2+ ceramics with a particle size of 120 ± 10 nm, which is excited in the range of 3.5–5.8 eV and subjected to synchrotron radiation with photon energies of up to 20 eV, is investigated. Nanoscale Zn2SiO4:Mn2+ ceramics possesses intense luminescence with a maximum of 2.34 eV, the position and half-width of the band are independent of the excitation energy. It is found that the photoluminescence at 2.34 eV decays nonexponentially upon ultraviolet excitation. In the case of nanoscale ceramics is irradiated by vacuum ultraviolet, an additional photoluminescence-excitation channel is likely to occur due to interaction of band states and intrinsic vacancy-like defects of the Zn2SiO4 matrix. 相似文献
13.
A. S. Nizamutdinov V. V. Semashko A. K. Naumov R. Yu. Abdulsabirov S. L. Korableva M. A. Marisov 《Physics of the Solid State》2005,47(8):1457-1459
The photochemical properties of CaF2 crystals activated by Ce3+ and Yb3+ ions are studied. A model of the photodynamic processes induced by pumping UV or VUV radiation in active media is suggested and experimentally verified. This model explains both the presence of color centers of electronic and hole nature in crystals activated by cerium and the mechanism of suppressing of solarization processes after additional activation of the samples by Yb3+ ions. The cross sections of the processes of free-carrier capture by various ytterbium impurity centers are estimated. These impurity centers are established to be effective centers of recombination of free carriers of both signs. 相似文献
14.
S. V. Zaitsev A. N. Gruzintsev Yu. V. Yermolayeva N. A. Matveevskaya I. I. Zverkova G. A. Emelchenko A. V. Tolmachev 《JETP Letters》2017,106(3):145-151
The kinetics of luminescence of Eu3+ ions in Lu2O3:Eu nanospheres with diameters of 100–270 nm and a small standard deviation of the size distribution <15% has been studied. A sharp decrease in the decay time of luminescence of Eu3+ ions in the red range with an increase in the diameter of nanospheres has been attributed to the appearance of a photon mode accelerating spontaneous luminescence, which is confirmed by the calculation of ranges of existence of whispering-gallery modes in studied nanospheres. 相似文献
15.
The influence of the oxygen partial pressure P
O
2 in the growth atmosphere on the coefficient of chromium distribution between the crystal and the melt of forsterite, the
Cr3+ and Cr4+ ion contents in crystals, and the concentration of color centers induced by irradiation has been investigated. It has been
established that the crystals grown at low oxygen partial pressures P
O
2 (0.01–0.05 kPa) are characterized by low concentrations of Cr4+ ions and color centers. A change in the oxygen partial pressure to P
O
2 ∼ 0.85 kPa leads to an increase in the Cr4+ center concentration by a factor of ∼10 and in the color center concentration by a factor of ∼5. A further increase in the
oxygen partial pressure to P
O
2 to 12 kPa remains the concentration of these centers almost unchanged. A model has been proposed according to which the intrinsic
defects formed under conditions of a relative excess of oxygen leads to both the self-oxidation of chromium and the formation
of color centers in the forsterite crystals under irradiation. 相似文献
16.
17.
A. D. Prokhorov M. T. Borowiec M. C. Pujol I. M. Krygin A. A. Prokhorov V. P. Dyakonov P. Aleshkevych T. Zayarnyuk H. Szymczak 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):389-395
The electron paramagnetic resonance (EPR) of Yb3+
ions in a KY(WO4)2 single crystal was investigated at T=4.2 K and
fixed frequency of 9.38 GHz. The resonance absorption observed on the lowest
Kramers doublet represents the complex superposition of three spectra,
corresponding to the ytterbium isotopes with different nuclear moments. The
EPR spectrum is characterized by a strong anisotropy of the g-factors. The
temperature dependence of the g-factors is shown to be caused by the strong
spin-orbital and orbital-lattice coupling. The resonance lines broaden with
increasing temperature due to the short spin-lattice relaxation times. 相似文献
18.
T. N. Vasilevskaya A. A. Kaplyanskii A. B. Kulinkin S. P. Feofilov 《Physics of the Solid State》2003,45(5):961-968
The properties of Cr3+-doped Li2Ge7O15 (LGO) lithium germanate nanocrystals produced in lithium germanate glasses under isothermal heating were studied. The samples were characterized by x-ray diffraction and small-angle scattering, as well as by transmission electron microscopy. The luminescence spectra of the impurity chromium measured in lithium germanate glasses containing LGO crystals revealed transitions in Cr3+ ions residing in the glass phase and in LGO crystallites starting from extremely small clusters. This provided the possibility of following the process of crystallization of the lithium germanate glass from Cr3+ luminescence spectra. The effects observed in the Cr3+ luminescence spectrum revealed a ferroelectric phase transition in LGO nanocrystals embedded in the glass. 相似文献
19.
S. V. Zaitsev Yu. V. Ermolaeva N. A. Matveevskaya I. I. Zver’kova A. V. Tolmachev 《Optics and Spectroscopy》2017,122(6):906-911
A study of the luminescence of Eu3+ ions in Y2O3 nanospheres indicates a significant influence of the porous structure of nanoparticles on the luminescence of dopant ions. It is shown that filling the nanopores of initially porous Y2O3 nanospheres shortens the decay time of the spontaneous luminescence of doping europium ions. The change in the decay time is associated with the change in the effective refractive index of the porous nanospheres. 相似文献
20.
A. V. Egranov T. Yu. Sizova V. A. Kozlovskiy 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(9):1069-1074
The ground state of monovalent ions of transitional metals in alkaline-earth fluorides is localized in the conduction band. It is shown by the example of monovalent Co and Ni ions in CaF2 and SrF2 crystals that this is responsible for the unstable state of these ions in cubic environments. A stable state is achieved by the monovalent ions shifting to off-center positions. 相似文献