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A novel solvent-thermal Y2O3 template method was explored to synthesise NaYF4:Yb3+,Tm3+ inverse opal photonic crystals (IOPCs), which show highly improved up-conversion luminescence properties. [ABSTRACT FROM AUTHOR]

Here, we report the wavelength-dependent and angle-dependent upconversion luminescence (UCL) enhancement of NaYF4:Yb3+,Tm3+@NaYF4:Yb3+,Nd3+ core–shell nanocrystals (NCs) resulting from Ag grating structures, which provides a novel insight for improving UCL. [ABSTRACT FROM AUTHOR]

In the present work, a novel strategy for the synthesis of Nd2O3/Au nanocomposites was successfully applied by a co-precipitation process, in which the upconversion luminescence (UCL) of Nd2O3 was a white broadband emission under 780–980 nm excitation. UCL enhancement in Nd2O3/Au nanocomposites with different doped concentrations of Au nanorods (NRs) under 980 nm and 808 nm excitation was systemically studied. It was observed that by the interaction of Nd2O3 with surface plasmon (SP) of Au NRs, the threshold power for generating broadbands was largely suppressed in contrast to the Nd2O3 nanoparticles (NPs). Further, it was interesting to observe that the enhancement was strongly dependent on the doped concentration of Au NRs and the excitation power of 980 nm and 808 nm laser diodes. The optimum UCL enhancement was 11-fold and 9-fold at 980 nm and 808 nm excitation, respectively. In addition, the upconversion (UC) broadband emission and UCL enhancement mechanism of Nd2O3/Au nanocomposites were proposed. [ABSTRACT FROM AUTHOR]

In this work, novel upconversion lanthanide oxyfluoride (LnOF:Yb3+, Er3+, Ln = La, Y, Gd) inverse opal photonic crystals (IOPCs) were successfully fabricated by the sol–gel method combined with polymethylmethacrylate (PMMA) template technique and the modulation of the photonic stop band (PSB) on the green emissions 2H11/2/4S3/2→4I15/2 for Er3+ ions were systemically studied under 980 nm excitation. The results showed that the LaOF IOPCs (annealed at 500 °C) were of cubic phase while GdOF and YOF matrices were of rhombohedral phase, and the LaOF IOPCs demonstrated more efficient upconversion luminescence (UCL) than GdOF and YOF due to the phase transition. In contrast to the ground reference (REF) samples, strong suppression of UCL was observed in the IOPCs while the PSB overlapped with the 2H11/2/4S3/2→4I15/2 lines. Furthermore, the spontaneous decay rates (SDRs) of 2H11/2/4S3/2→4I15/2 were suppressed in the IOPCs, independent of the location of the PSB. In LaOF IOPCs, the decay time constants of 4S3/2→4I15/2 were increased by as much as 9 times in contrast to the corresponding REFs. It was also significant to observe that in the IOPCs the local thermal effect was greatly suppressed. In addition, broadband UCL extending into the visible range was observed in LnOF:Yb3+, Er3+ REF samples under high excitation power, and the origin was identified by electron paramagnetic resonance (EPR) spectroscopy. [ABSTRACT FROM AUTHOR]

Here, we report the wavelength-dependent and angle-dependent upconversion luminescence (UCL) enhancement of NaYF4:Yb(3+),Tm(3+)@NaYF4:Yb(3+),Nd(3+) core-shell nanocrystals (NCs) resulting from Ag grating structures, which provides a novel insight for improving UCL.

Three-dimensional (3D) inverse opal photonic crystals can not only modulate the emissions of the inserted emitters, they also have the advantage of a large surface to volume ratio, which permits their use in noninvasive fluorescence detection. In this work, novel NaY(MoO4)2:Eu(3+) and NaY(MoO4)2:Tb(3+), Eu(3+) inverse opals were synthesized using a polymethylmethacrylate (PMMA) template by the sol-gel method. It was observed that the photoluminescence (PL) intensity and spontaneous decay rates (SDRs) of the inverse opals were suppressed, in contrast to the corresponding ground reference (REF) samples, due to the modulation of the effective refractive index (n(eff)). The concentration quenching of Eu(3+) and energy transfer from Tb(3+) to Eu(3+) were suppressed, due to the periodic empty cavity structure of the inverse opals.