Adjusting the structure and luminescence properties of Sr2-x Bax MgAl22 O36 :Eu2+ phosphors by Sr:Ba ratio.

Europium ion (Eu2+ )-doped phosphors exhibit adjustable photoluminescence due to the sensitivity of their luminescence to the local environment. It is of great significance to adjust the luminescence of Eu2+ by changing their local environment in the host. In this work, we investigated the effect of strontium/barium (Sr:Ba) ratio on the structure and luminescence properties of Sr2-x Bax MgAl22 O36 :Eu2+ phosphors. Our investigation indicates that with the decrease of Sr:Ba ratio, the matrix lattice gradually expands and the peak wavelength for the luminescence of Eu2+ presents an obvious blue shift. The occupancy of Eu2+ was analyzed and the reason for the blue shift was explained. Thermal stability for the luminescence of Eu2+ can also be adjusted by changing the Sr:Ba ratio. This work has a positive effect on the regulation of the emission of phosphors and the improvement of thermal stability, which will promote the application of Sr2-x Bax MgAl22 O36 :Eu2+ phosphors in the field of white light emitting diodes.

Experimental and Theoretical Studies of Ultrafine Pd-Based Biochar Catalyst for Dehydrogenation of Formic Acid and Application of In Situ Hydrogenation.

In this work, a novel "foaming" strategy uses sodium bicarbonate (NaHCO3) and ammonium oxalate ((NH4)2C2O4) as the foaming agent, turning biomass-derived carboxymethyl cellulose (CMC) into N-doped porous carbon. Highly active palladium nanoparticles (Pd NPs) immobilized on nitrogen-doped porous carbon (Pd@MC(2)-P) are produced through a phosphate-mediation approach. The phosphoric acid (H3PO4) becomes the key to the synthesis of highly dispersed ultrafine Pd NPs on active Pd-cluster-edge (the edge of the Pd-cluster-100 and Pd-cluster-111 surfaces). The Pd@MC(2)-P exhibits high activity for formic acid (FA) dehydrogenation with an initial TOFg of 971 h-1 at room temperature. The subsequent hydrogenation of phenol using FA as an in situ hydrogen source on Pd@MC(2)-P and the highly efficient hydrogenation of phenol to cyclohexanone reaches more than 90% selectivity and 80% conversion. Density functional theory (DFT) calculations reveal that the reduced H poisoning and more exposed (100) surface over Pd nanoparticles are the keys to the Pd nanoparticles' high activity.

Accurately Controlling the Occupation of Eu2+ in Cs(K, Na)3(Li3SiO4)4 to Achieve Narrow-Band Green Emission for Wide Color Gamut Displays.

The development of narrow-band phosphors for wide color gamut displays in multimodal phosphors through selective site occupancy engineering is an important challenge. In this work, by replacing Na ions with K ions in the cyan-green double-band emitting phosphor CsK0.9Na2(Li3SiO4)4: 10%Eu2+, the occupation of Eu2+ in Cs(K, Na)3(Li3SiO4)4 was accurately controlled from occupying three sites of Cs, K1, and Na to occupying only one site of K2/Na. The obtained phosphor CsK1.9Na(Li3SiO4)4: 10%Eu2+ exhibits a single narrow-band green emission at 531 nm (the full width at half-maximum of 46 nm) with excellent thermal stability of luminescence from 80 to 523 K (96.3% @423 K of the intensity of integrated emission at room temperature and 94.9% @300 K of the intensity of integrated emission at 80 K). The white light-emitting diode (wLED) that was fabricated by combining a blue LED chip with this narrow-band green phosphor and red phosphor K2SiF6: Mn4+ presents a satisfactory wide color gamut of 128.1% of the National Television Standards Committee, which demonstrates the important application value of the phosphor in the wide color gamut displays field. This work provides an effective design strategy for exploring narrow-band phosphors through selective site occupancy engineering, which will facilitate the exploration of relevant narrow-band emitters in the future.

Trivalent Chromium Ions Doped Fluorides with Both Broad Emission Bandwidth and Excellent Luminescence Thermal Stability.

Recently, trivalent chromium ion doped phosphors have exhibited significant application potential in broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs). However, developing an NIR phosphor with both broad emission bandwidth and excellent luminescence thermal stability is still a great challenge. Here, we demonstrate an NIR phosphor, ScF3:Cr3+, which can fulfill both conditions simultaneously. The prepared phosphors show broadband emission in the range of 700 to 1100 nm, with a full width at half-maximum (FWHM) of 140 nm peaking at 853 nm. These phosphors also demonstrate an excellent luminescence thermal stability (the emission intensity of ScF3:Cr3+ keeps 85.5% at 150 °C compared with the value at room temperature). An NIR pc-LED based on blue LED chips was fabricated and tested. The results show that the NIR pc-LED can yield strong broadband NIR emission. This work not only provides a promising phosphor for the application of NIR pc-LEDs but also has important guiding significance for effect of synthesis conditions on the luminescence properties of Cr3+-doped fluorides.

The design of dual-switch fluorescence intensity ratio thermometry with high sensitivity and thermochromism based on a combination strategy of intervalence charge transfer and up-conversion fluorescence thermal enhancement.

Currently, the temperature sensing performances of inorganic photoluminescence materials based on fluorescence intensity ratio technology have become a research hotspot in the optical thermometry field due to their non-contact sensing, fast response and high stability. However, several problems have obstructed the development of optical temperature sensing materials, including low sensitivity and narrow temperature measurement ranges. In view of the above dilemma, a new optical thermometer La2Mo3O12:Yb3+,Pr3+ designed based on the combination strategy of intervalence charge transfer and up-conversion fluorescence thermal enhancement was developed. Under excitation at 450 nm, the thermometer can work in a range from 298 to 648 K and the relative sensitivity reaches as high as 2.000% K-1 at 648 K. Under excitation at 980 nm, the thermometer can sense temperature with a wide range from 298 to 748 K and the relative sensitivity reaches as high as 4.325% K-1 at 598 K. A dual-switch optical temperature sensing material with high-sensitivity and a wide temperature measurement range has been successfully developed. Our research design strategies will give inspiration to the research on multi-switch temperature sensing materials with high sensitivity and a wide temperature measurement range.