Effect of Al2O3/Ga2O3 ratio on the structure and luminescence properties of Sm3+ doped SrO-Nb2O5-Al2O3-Ga2O3-SiO2 glasses.

The Sm3+ doped SrO-Nb2O5-Al2O3-Ga2O3-SiO2 glasses in this work were prepared using the conventional melt quenching method. The effects of Al2O3/Ga2O3 ratio on the structure and orange light emission properties were studied by XRD, Raman spectroscopy, spectrophotometer and J-O theory, respectively. With the increase of Al2O3 content, the absorption coefficient of the glass sample gradually increases, which might be attributed to an increase in non-bridged oxygen bonds caused by a change in the glass network structure. Under 403 nm excitation, the emission spectra show clear peaks at 602 nm and 649 nm, representing the 4G5/2 â†’ 6H7/2, and 4G5/2 â†’ 6H9/2 transitions, respectively. When the Al2O3/Ga2O3 ratio is 0.25, the sample luminescence intensity is the highest, and the emission cross section of A2 glass sample is 4.34 × 10-22 cm2. The CIE color coordinates, color purity, and color temperature values of all samples were determined, and they were all located in the orange-red light region. The experiments results reveal that the prepared silica-aluminum-gallium glasses has a potential application prospect in orange-red LEDs, solid state lasers and other fields.

Hexagonal Halide Perovskite Cs2LiInCl6: Cation Ordering, Face-Shared Octahedral Trimers and Mn2+ Luminescence.

The In-based double perovskite halides have been widely studied for promising optical-electric applications. The halide hexagonal perovskite Cs2LiInCl6 was isolated using solid-state reactions and investigated using X-ray diffraction and solid-state NMR spectra. The material adopts a 12-layered hexagonal structure (12R) consisting of layered cationic orders driven by the cationic charge difference and has Li+ cations in the terminal site and In3+ in the central site of face-shared octahedron trimers. Such a cationic ordering pattern is stabilized by electrostatic repulsions between the next-nearest neighboring cations in the trimers. The LiCl6 octahedron displays large distortion and is confirmed by 7Li SS NMR in the Cs2LiInCl6. The Cs2LiInCl6 material has a direct bandgap of ~4.98 eV. The Cs2LiInCl6: Mn2+ displays redshift luminescence (centered at ~610-622 nm) from the substituted Mn2+ emission in octahedron with larger PLQY (17.8 %-48 %) compared with that of Cs2NaInCl6: Mn2+. The Mn-doped materials show luminescent concentration quenching and thermal quenching. The composition Cs2Li0.99In0.99Mn0.02Cl6 exhibits the highest PL intensity, a maximum PLQY of 48 %, and high luminescent retention rate of ~86 % below 400 K and is suitable for application for pc-LED. These findings contribute to our understanding of the chloride perovskites and hold potential for widespread optical applications.

A multidentate polymer microreactor route for green mass fabrication of mesoporous NaYF4 clusters.

We report a "multidentate polymer microreactor" method for the creation of secondary structures of colloidal nanocrystals. Using NaYF4:Yb,Er as an example, we demonstrate that the use of sodium polyacrylate (PAAS) as a "multidentate polymer microreactor" allows the controllable growth of primary nanocrystals and induces aggregation of the nanocrystals into well-defined mesoporous clusters.

High efficient and broadband ∼3.5 µm emission of Er3+:YAG crystal.

The YAG single crystals doped with 10 at.%, 20 at.% and 50 at.% Er3+ were successfully grown by the micro-pulling down method and spectroscopic properties of the crystals were investigated. The main interest was focus on the relation between the Er3+ concentration and ∼3.5 µm emission of Er3+:YAG crystals. Room temperature absorption spectra were analyzed by the Judd-Ofelt theory. The stimulated emission cross-sections were calculated by the Füchtbauer-Ladenburg equation. The fluorescence intensities and peak emission cross-sections of the crystals at ∼3.5 µm are slightly decreasing with the increase of Er3+ concentration. The trend of the emission properties in NIR and visible region with the Er3+ concentration was also discussed and compared. The results indicate that the highly doped Er3+ concentration is beneficial to realize the ∼3.5 µm laser output.

Effect of Acidic Polymers on the Morphology of Laser-Induced Nucleation of Cesium Chloride.

An approach to controlling morphology and size is presented through the combination of laser-induced nucleation and polymer additives. Here, we apply the technique of non-photochemical laser-induced nucleation to irradiate a supersaturated solution (S = 1.15) of cesium chloride (CsCl). The solution immediately responds to laser exposure, and spherical crystallites are produced along the laser pathway. The crystals gradually grow into snowflake-like crystals with different sizes. In this report, two types of acidic polymers including polyepoxysuccinic acid (PESA) and polyaspartic acid (PASA) were individually added in supersaturated CsCl solution to shape its crystalline morphology; we found that a particular property of this control from PESA is uniformity in modification of crystal sizes. Additionally, we observed that both PESA and PASA were able to decrease crystal growth velocity and the quantity of crystals after laser irradiation. With the effect of more than 0.2 wt % PESA in solution, spherical crystallites were initially induced by laser; after that, crystal growth velocities and sizes became slower and smaller with increase in mass fraction of PESA, which led to identical crystal sizes. With the effect of more than 5 wt % PESA, the resulting crystalline morphology obtained by laser was flower-like crystals, whilst cuboid-shaped crystals could be obtained by spontaneous nucleation. Classical nucleation theory, crystal growth rate, and additives as large-size impurities were discussed to analyze the underlying mechanism of the change in morphology.

Sensitivity improvement induced by thermal response behavior for temperature sensing applications.

Overcoming the restriction of the energy gap (700-800 cm-1) in Er3+-doped upconversion (UC) materials to achieve high detection accuracy is crucial for practical temperature detection applications. Herein, we design a feasible route based on the different thermal response behaviors of various hosts to enhance the SA value in a double perovskite NaLaMgWO6:Er,Mo system. The maximum SA value is 222.8 × 10-4@423 K in the NLMW:5%Er3+ host, and this can be promoted to 275.4 × 10-4 K-1@323 K in the NaLaMgWO6:Er,Mo system. The SR values decrease monotonously as the temperature rises, and this is due to the dependency of the SR values on the energy gap. A mechanism that is ascribed to the different thermal response behaviors of the various hosts is proposed, and this mechanism is further proved by investigating the temperature sensing properties of barium gadolinium zincate phosphors that possess the same thermal response behaviors. In addition, this study introduces the idea that a host with a high emission intensity for the 2H11/2 level and a lower emission intensity for the 4S3/2 level is highly suitable for temperature measurements. A thorough investigation of this system offers a strategy to acquire a high SA value and reveals the broad prospects of NaLaMgWO6:Er,Mo in the temperature detection field.