Zhiguo Song

Enhancement of the up-conversion luminescence of Yb3+/Er3+ or Yb3+/Tm3+ co-doped NaYF4 nanoparticles by photonic crystals

A new method for enhancing the upconversion (UC) emission of rare-earth doped nanoparticles is reported, in which Yb3+/Er3+ or Yb3+/Tm3+ co-doped NaYF4 nanoparticles are deposited on to the surface of photonic crystal (PC) films. The UC emission of the Yb3+/Er3+ or Yb3+/Tm3+ co-doped NaYF4 nanoparticles on the PC surface was notably enhanced when the UC emission bands of the Yb3+/Er3+ or Yb3+/Tm3+ co-doped NaYF4 nanoparticles were within the range of the photonic band gap of the PCs, indicating that the PCs were efficient and selective reflection mirrors. The results show that PCs may have potential applications in UC optoelectronics and lighting devices.

Energy transfer and photoluminescence modification in Yb–Er–Tm triply doped Y2Ti2O7 upconversion inverse opal

In this article, we fabricated Y2Ti2O7: Yb, Er, Tm upconversion inverse opal photonic crystals with energy transfer between Er3+ and Tm3+, and investigated the influence of the photonic band gap on the energy transfer between Tm3+ and Er3+. It is interesting that strong modification of the steady state upconversion emission spectra is observed, and the green or red upconversion emission from Er3+ was suppressed in the inverse opal. More significantly, the energy transfer between Tm3+ and Er3+ is enhanced by suppression of the red upconversion emission of Er3+, thus the blue upconversion emission from Tm3+ is considerably improved in the inverse opals. Additionally, the mechanisms for upconversion emission of the Y2Ti2O7: Yb, Er, Tm inverse opal are discussed. We believe that the present work will be valuable for the foundational study of upconversion emission modification and the application of upconversion displays and short wavelength upconversion lasers.

Effect of photonic bandgap on upconversion emission in YbPO 4 :Er inverse opal photonic crystals

We obtained upconversion (UC) light-emitting photonic materials (YbPO(4):Er) with an inverse opal structure by the self-assembly technique in combination with a solgel method. The effect of the photonic stopband on the UC luminescence of the (2)H(11/2), (4)S(3/2)→(4)I(15/2), and (4)F(9/2)→(4)I(15/2) transitions of Er(3+) has been observed in the inverse opals of the Er(3+)-doped YbPO(4). Significant suppression of the UC emission was detected if the photonic bandgap overlapped with the Er(3+) ions emission band, while enhancement of the UC emission occurs if the emission band appears at the edge of the bandgap.

Sm 3+ photoreduction in BaCl 2 nanophases precipitated fluoroaluminate glasses under femtosecond laser irradiation

Photoreduction of samarium-doped BaCl(2)-modified aluminofluoride glass by femtosecond laser irradiation and x-ray irradiation were investigated. Photoluminescence of samarium ions indicated that photoreduction of Sm(3+)→Sm(2+) efficiently occurred in glass samples containing more than 5 mol.% BaCl(2) after femtosecond laser irradiation, while dramatic change was not observed by x-ray irradiation. Transmission electron microscope results revealed that BaCl(2) nanophases only precipitated from glass matrix with a high BaCl(2) content by focusing femtosecond laser irradiation. Samarium ions were selectively incorporated into the precipitated nanophases, resulting in the enhancement of Sm(3+) photoreduction under lower laser power.

Optical properties of Ce3+–Nd3+ co-doped YAG nanoparticles for visual and near-infrared biological imaging

Ce(3+)-Nd(3+) co-doped Y3Al5O12 (YAG) nanoparticles, an average size of 20-30 nm clusters aggregated by 8-10 nm YAG nanoparticles, were synthesized by a solvothermal method. When excited by blue irradiation source, strong and broad yellow luminescence (centered at 526 nm) from Ce(3+) as well as near-infrared (NIR) luminescence (890, 1066 and 1335 nm) of Nd(3+) was observed simultaneously. It occurred by the effective dipole-dipole energy transfer from Ce(3+) to Nd(3+). Energy transfer efficiency from Ce(3+) to Nd(3+) was also calculated to be 50%. The optical property suggests that Ce(3+)-Nd(3+) co-doped YAG nanoparticles can be used as an efficient fluorescence imaging agent for not only visual but also near-infrared imaging.

Synthesis and upconversion emission properties of Pb0·9La0·1TiO3:Yb, Tb inverse opals by sol–gel technique

Abstract Inverse opal photonic crystals of Yb3+, Tb3+ codoped Pb0·9La0·1TiO3 were synthesised by a sol–gel technique in combination with a self-assembly method. Opal template was self-assembled from suspensions of monodisperse polystyrene microspheres with a mean diameter of 400 nm via a vertical deposition process. After infiltrating the Yb3+, Tb3+ codoped Pb0·9La0·1TiO3 sol into the opal template, the polystyrene microspheres were removed by calcination at 670°C, and Yb3+, Tb3+ codoped Pb0·9La0·1TiO3 inverse opal photonic crystals were formed. The effect of photonic band gap on upconversion emissions was investigated in the Yb3+, Tb3+ codoped Pb0·9La0·1TiO3 inverse opals. Significant suppression of the upconversion emission was detected if the photonic band gap overlapped with the Tb3+ ions emission band, leading to colour tuneable upconversion photonic crystals with applications in solid state colour displays.

Blue and green upconversion luminescence modification of Tb3+–Yb3+ co-doped Ca5(PO4)3F inverse opal

Tb3+–Yb3+ co-doped Ca5(PO4)3F inverse opal photonic crystals were prepared by a self-assembly technique in combination with a sol–gel method. Upconversion luminescence characteristics of the inverse opals were investigated. The results indicate that photonic band gap has a significant effect on upconversion luminescence of Tb3+–Yb3+ co-doped Ca5(PO4)3F inverse opal. Significant inhibition of the green or blue upconversion luminescence was inspected if the photonic band gap overlapped with the emission band of Tb3+ ions.

Upconversion Emission Modification and White Light Generation in NaYF 4 :Yb 3+ , Er 3+ , Tm 3+ Nanocrystals/Opal Photonic Crystal Composites

In this paper, we fabricated NaYF 4:Yb³⁺, Er³⁺, Tm³⁺ nanocrystal/opal photonic crystal composites by depositing NaYF 4:Yb³⁺, Er³⁺, Tm³⁺ nanocrystals on the surface of opal photonic crystals, and we investigated the influence of photonic bandgaps on upconversion (UC) emission properties of NaYF 4:Yb³⁺, Er³⁺, Tm ³⁺ nanocrystals. When the photonic bandgaps overlapped with the UC emission bands of NaYF 4:Yb³⁺, Er³⁺, Tm³⁺ nanocrystals on the opal photonic crystal surfaces, the suppression or enhancement of UC emissions was observed due to the Bragg reflection effect of photonic crystal, resulting in the modification of red, green, and blue UC emissions. Thus, white UC emission was realized.

Upconversion Luminescence with Adjustable Multi-Color in Rare Earth Co-Doped Transparent Oxyfluoride Glasses

Transparent oxyfluoride glasses with highly efficient upconversion (UC) luminescence were developed in the 47.4SiO₂-19Al₂O₃- 28.4CaF₂- xTbF₃- 0.1TmF₃- 3.2YbF₃- (2-x)GdF₃ composition, in mol%. The colors of upconversion luminescence could be tuned easily by adjusting the excitation power of laser and concentration of doped rare earth ions simultaneously. The relationship between the emission intensity of Tb³⁺/Tm³⁺/Yb³⁺ - codoped oxyfluoride glasses and the excitation pump power revealed that three-photon and two-photon absorption predominated in the conversion process from the infrared into blue and red luminescence, respectively. And a novel UC mechanism of red emission from Tm³⁺ is proposed and discussed.

Synthesis and Near-Infrared Fluorescent Properties of Nd3+-Yb3+ Co-Doped Lanthanum Phosphate

In the present work, LaPO₄: Ln (Ln = Nd, Yb) samples were prepared via a simple hydrothermal method and characterized by X-ray diffraction, UV-Vis spectrophotometer, and fluorescence spectrophotometer. The XRD patterns show that the crystal structure of samples was lanthanum phosphate phase that belongs to monoclinic system with a space group of P2₁/n. Nd³⁺, as a sensitizer, was excited to ⁴I_9/2 by 808 nm laser diode, and then transfer the energy to Yb³⁺, resulting in the fluorescent emission at 980 nm. This fluorescent emission arises from the ²F_5/2→²F_7/2 transition. And the luminescent intensity depends on the concentration of Yb³⁺ ions. This implies that the concentration quenching is observed in the present work. The optimal Yb³⁺ ions concentration is 4 mol %.