Hangjun Wu

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.

Enhancement of near-infrared to near-infrared upconversion emission in the CeO₂: Er³⁺, Tm³⁺, Yb³⁺ inverse opals.

In this Letter, CeO₂: Er³⁺, Tm³⁺, Yb³⁺ inverse opal with near-infrared to near-infrared upconversion emission was prepared by polystyrene colloidal crystal templates, and the influence of photonic bandgap on the upconversion emission was investigated. Comparing with the reference sample, suppression of the blue or red upconversion luminescence was observed in the inverse opals. It is interesting that the near-infrared upconversion emission located at about 803 nm was enhanced due to the inhibition of visible upconversion emission in the inverse opals. Additionally, the variety of upconversion emission mechanisms was observed and discussed in the CeO₂: Er³⁺, Tm³⁺, Yb³⁺ inverse opals.

UPCONVERSION LUMINESCENCE ENHANCEMENT OF NaYF4:Yb3+, Er3+ NANOPARTICLES ON INVERSE OPAL SURFACE

LaPO4 inverse opal photonic crystals with different photonic band gaps were fabricated by template-assisted method. The Yb3+/Er3+ co-doped NaYF4 nanoparticles were deposited on the surfaces of the inverse opals, and their up-conversion emission properties were investigated. The upconversion emissions of Yb3+/Er3+ co-doped NaYF4 nanoparticles on the inverse opal surfaces have been enhanced when the upconversion emission bands of the nanoparticles are in the range of photonic band gaps of the inverse opals, which is attributed to an efficient and selective reflection of photonic band gaps.

Investigation of upconversion and near infrared emission properties in CeO 2 : Er 3+ , Yb 3+ inverse opals

The upconversion emission of rare earth ions can be modified in photonic crystals, however, the influence of upconversion emission modification of rare earths on near infrared emission has not been investigated yet in the photonic crystals. In the paper, CeO₂: Er³⁺, Yb³⁺ inverse opals with the photonic band gaps at 545, 680 and 450 nm were prepared by polystyrene colloidal crystal templates. The upconversion and the near infrared emission properties of Er³⁺ ions were systematically investigated in the CeO₂: Er³⁺, Yb³⁺ inverse opals. Comparing with the reference sample, significant suppression of both the green and red upconversion luminescence of Er³⁺ ions were observed in the inverse opals. It is interesting that the infrared emission located at 1,560 nm was enhanced due to inhibition of upconversion emission in the inverse opals. Additionally, mechanism of upconversion emission of the inverse opal was discussed. The photon avalanche upconversion process is observed.

Continuous modification of upconversion luminescence of fluorescent dye in the crystalline colloidal arrays

The crystalline colloidal arrays with controllable photonic bandgaps were prepared by the change of volume fraction of the polystyrene microspheres. Upconversion emission property of fluorescent dye has investigated in crystalline colloidal array, and continuous modification of the upconversion emission of fluorescent dye was observed. A significant suppression of upconversion emission of dye in the range of the photonic bandgap as well as enhancement at the bandgap edge was obtained in the crystalline colloidal arrays. In addition, upconversion emission of dye was also enhanced when the excited light overlapped with the long or short bandgap edge of the crystalline colloidal arrays, which is due to slow photons effect near the edges of a photonic bandgap. The continuous modification and enhancement of upconversion emission may be important for the development of low-threshold upconversion lasers and displays.

Upconversion emission properties of CeO2: Tm3+, Yb3+ inverse opal photonic crystals

The ordered and disordered templates were assembled by vertical deposition of polystyrene microspheres. The CeO2: Tm3+, Yb3+ precursor solution was used to infiltrate into the voids of the ordered and disordered templates, respectively. Then the ordered and disordered templates were calcined at 950°C in an air furnace, and the CeO2: Tm3+, Yb3+ inverse opals were obtained. The upconversion emissions from CeO2: Tm3+, Yb3+ inverse opals were suppressed due to the photon trapping caused by Bragg reflection of lattice planes when the upconversion emission band was in the range of the photonic band gaps in the inverse opals.

Preparation and upconversion emission modification of Yb, Er co-doped Y2SiO5 inverse opal photonic crystals.

Yb, Er co-doped Y2SiO5 inverse opal photonic crystals with three-dimensionally ordered macroporous were fabricated using polystyrene colloidal crystals as the template. Under 980 nm excitation, the effect of the photonic stopband on the upconversion luminescence of Er3+ ions has been investigated in the Y2SiO5:Yb, Er inverse opals. Significant suppression of the green or red UC emissions was detected if the photonic band-gap overlaps with the Er3+ ions emission band.

Blue and Green Upconversion Emission Modification in Tb, Yb Co-Doped Y2Ti2O7 Inverse Opal

We obtained upconversion light-emitting photonic materials (Y₂Ti₂O₇: Tb, Yb) with an inverse opal structure by a self-assembly technique in combination with a sol-gel method, and investigated their upconversion emission properties. The results showed that the photonic band gap has a significant influence on the upconversion emission of Yb, Tb co-doped Y₂Ti₂O₇ inverse opal photonic crystals. Significant suppression of the blue or green upconversion emission was detected if the photonic band gap overlapped with the Tb³⁺ ions emission band.

Preparation and Upconversion Emission Properties of Y2O3 : Er, Yb Inverse Opal

Upconversion light-emitting photonic band gap materials (Y₂O₃: Yb, Er) with inverse opal structure were prepared by a self-assembly technique in combination with a sol-gel method. The effect of the photonic stop-band on the upconversion luminescence of Er³⁺ ions has been investigated in the Y₂O₃: Yb, Er inverse opals. Suppression of the upconversion emission was detected if the photonic band-gap overlaps with the Er³⁺ ions emission band, while enhancement of the upconversion emission occurs if the emission band appears at the edge of the band gap.