Upconversion Optical Properties Research Articles

In situ doped Cs2AgIn0.9Bi0.1Cl6:8%Yb,2%Er/PVDF composite films for the printing of multimodal fluorescent anti-counterfeiting marks

The fluorescent anti-counterfeiting technology has become one of the most desirable candidates in practical anti-counterfeiting applications owing to its adjustable emission, high recognition and design flexibility. However, the security level of single emitting fluorescent materials was lower, and no longer able to cope with current forgery techniques, so the development of higher level multimodal fluorescent anti-counterfeiting technologies was urgent. In this report, lead-free double perovskite (DP) material CsAgBiCl6 was chosen as the host and a technique for in situ growth in polymer polyvinylidene difluoride (PVDF) was proposed to obtain large-scale high-quality Cs2AgBiCl6/PVDF composite films (CFs). Subsequently, the Cs2AgIn0.9Bi0.1Cl6:8%Yb,2%Er/PVDF CFs with both down-conversion and up-conversion optical properties was achieved by hybrid (In3+/Yb3+/Er3+) doping, which was able to displayed inconsistent fluorescence emission (orange and green) under different excitation sources, and their fluorescence intensities exhibited tunability with the change of the environmental temperature, greatly enhancing its competitiveness in the field of fluorescent anti-counterfeiting. Finally, different anti-counterfeiting marks have been designed by the screen-printing process, and the complex encryption once again ensured the security of the information, while bringing a new gospel to the subsequent development of lead-free DP materials.

Er/Yb co-doped LiYF4 transparent oxyfluoride glass-ceramics with up-conversion optical properties

Transparent oxyfluoride glass-ceramics doped with rare earth ions (RE3+) are promising materials for photoluminescence up- and down-conversion. In this study, glass compositions within the system 40SiO2–25Al2O3–18Li2O–7LiF–10YF3 (mol.%) doped with ErF3 and codoped with ErF3/YbF3 were prepared by melt-quenching method and subjected to thermal treatment at temperatures above glass transition (Tg + 35 °C) for long dwell times to obtain the corresponding glass-ceramics. The formation of LiYF4 and LiAlSiO4 nanocrystals was confirmed by XRD analysis after thermal treatment at 540 °C for 20 h. The increase in the treatment time up to 80 h resulted in the enhancement of the UC luminescence yield and the decrease of the Red to Green ratio (R/G) emission intensity. Due to the nano-sized crystals, the glass-ceramic products were transparent (%T) in near-infrared (NIR) and visible spectral region with %T remaining approximately 85% and 75%, respectively, after 20 h treatment. However, the visible window transparency reduced, with %T dropping to around 50% after 80 h due to the increase in crystal size and crystalline fraction. The influence of Yb3+ co-doping on the up-conversion (UC) luminescence has been investigated in the glass-ceramics and compared to the parent glasses, confirming that Yb3+ ions were also a key factor for facilitating up-conversion via energy transfer (ET), leading to a greater luminescence yield than for Er3+ single doped glass-ceramics and tuning of R/G intensities.

Upconversion luminescence of Yb3+/Er3+ co-doped NaSrPO4 glass ceramic for optical thermometry

In order to expand the types of up-conversion (UC) luminescent materials used for optical thermometry, a novel Yb3+/Er3+ double doped glass ceramic (GC) containing NaSrPO4 nanocrystals was synthetised via melt quenching and heat treatment. The crystal structure morphology and UC optical properties were systematically studied, and the luminescence mechanism and energy transfer process were described. In addition, the relationship between the UC luminescence and temperature change of the GC specimen from 298 K to 573 K was measured under a 980 nm laser. The optical thermo-sensitive performance of GC was studied by the luminescence intensity ratio based on the thermally coupled emission states of Er3+, 2H11/2 and 4S3/2. For the GC sample annealed at 630 °C for 3 h, the maximum relative sensitivity Sr-max at 298 K was 1.78% K−1, the maximum absolute sensitivity Sa-max at 573 K was 5.28 × 10−3 K−1, which indicated that the GC materials might be potential candidates for optical temperature sensors.

Cu2+离子共掺杂的β-NaYF4∶Yb3+, Er3+晶体的制备与上转换发光性能的提高

Cu²⁺离子共掺杂的β-NaYF₄∶Yb³⁺, Er³⁺晶体的制备与上转换发光性能的提高

ChemInform Abstract: Lab on Upconversion Nanoparticles: Optical Properties and Applications Engineering via Designed Nanostructure

AbstractReview: 268 refs.

Engineering homogeneous doping in single nanoparticle to enhance upconversion efficiency.

Upconversion nanoparticles (UCNPs) have shown considerable promises in many fields; however, their low upconversion efficiency is still the most serious limitation of their applications. Herein, we report for first time that the homogeneous doping approach based on the successive layer-by-layer method can greatly improve the efficiency of the UCNPs. The quantum yield as high as 0.89 ± 0.05% is realized for the homogeneous doping NaGdF4:Yb,Er/NaYF4 UCNPs, which is nearly 2 times higher than that of the heterogeneous doping NaGdF4:Yb,Er/NaYF4 UCNPs (0.47 ± 0.05%). The influences of spatial distributions and local relative concentrations of the dopants on the optical properties of UCNPs were investigated in the single particle level. It was found that heterogeneous doping indeed existed during the spontaneous growth process of the nanoparticles. The heterogeneous doping property can further induce many negative effects on the optical properties of UCNPs, especially the luminescent efficiency. The spatial distributions and local relative concentrations of the dopants can be well controlled by the successive layer-by-layer homogeneous doping method on the monolayer level and homogeneously distributed in the single particle level. Furthermore, by using homogeneous doping NaGdF4:Yb,Tm as initial core, the multicolor emission intensity of NaGdF4:Yb,Tm/NaGdF4:A (A = Tb(3+), Eu(3+)) core/shell nanoparticles can also exhibit 20%-30% improvement. We believe that such a homogeneous doping model can open the door to improve the upconversion optical properties by engineering the local distribution of the sensitizer, activator, host, etc., in a microcosmic and provide a track for engineering the high quality UCNPs with advanced nanostructure and optical properties.

The effect of MgO on the optical properties of lithium sodium borate doped with Cu+ ions

The current work presented the photoluminescence (PL) properties of a new glass system, which are reported for the first time. Based on the attractive properties of borate glass, a mixture of boric acid (70�x mol %) modified with lithium (20 mol %) and so dium carbonate (10 mol %) was prepared. The current study illustrated the effect of dopant and codopant te chniques on the lithium sodium borate (LNB). Firstly, 0.1 mol % of copper ions doped with LNB was excited at 610 nm. The emission spectrum showed two prom� inent peaks in the violet region (403 and 440 nm). Then, we remarked the effect of adding different concen� tration of MgO on the optical properties of LNB. The results showed the great effect of magnesium oxide on the PL intensities (enhanced more than two times). Moreover, an obvious shifting has been defined toward the blue region (440 475 nm). The upconversion opti cal properties were observed in all emission spec� tra. This enhancement is contributed to the energy transfer from MgO ions to monovalent Cu + ion. It is well known that magnesium oxide alone generates weak emission intensity, but during this increment the MgO act as an activator (codoped) for Cu io ns. Finally, energy band gap, density, ion concentration, molar volume, Polaron radius and internuclear distance all were measured for the current samples. The current samples were subjected to XRD for amorphous confirmation and IR for glass characterization before and after dopants addition. Finally, some of significant physical and optical parameters were also calculated.

Two-photon pumped upconversion and nonlinear optical properties of a new lasing dye: HMASPS

Two-photon pumped frequency upconversion optical properties and two-photon absorption (TPA) induced nonlinear absorption of a new dye, trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium ptoluene sulfonate (abbreviated to HMASPS) have been experimentally investigated. This new dye exhibits strong superradiation properties when the pumping power is above its threshold. The superradiation upconversion efficiency from 900 to 1150 nm and the nonlinear absorption from 720 to 1100 nm have been measured. The largest effective molecular TPA cross-section was measured to be 44.3 × 10−48 cm4·s·photon−1at 920 nm. At 1064 nm, it was 2.77 × 10−48 cm4·s·photon−1, much smaller than that at 920 nm. The highest conversion efficiency is 7% at 990 nm, whereas 4.2% at 1064 nm.

Two Photon Pumped Upconversion and Nonlinear OpticalProperties of a New Lasing Dye: DEASPI

The two-photon pumped frequency upconversion optical properties and thetwo-photon absorption (TPA) induced nonlinear absorption of a new dyetrans-4-[p-(N,N-diethylamino)styryl]-N-methylpyridinium iodide (abbreviatedas DEASPI) have been experimentally investigated. This new dye exhibitsstrong superradiation properties when the pumping power is above thethreshold. Furthermore, the superradiation upconversion efficiency and thenonlinear absorption at different wavelengths have been measured. Thelargest effective molecular TPA cross section was measured to be 3.9×10-47 cm4·s/photon at 930 nm. At 1064 nm, itwas 3.85×10-48 cm4·s/photon, much smallerthan that at 930 nm. The highest upconversion efficiency is 7.57% at1020 nm, whereas it is 4.5% at 1064 nm.