Visible light-induced catalytic performance of composite photocatalyst synthesized with nanomaterials WO3 and two-dimensional ultrathin g-C3N4.

To improve the visible light-induced catalytic activities of Ultrathin g-C3N4 (UCN), a promising photocatalyst WO3/UCN (WU) was synthesized. Its visible light-driven photocatalysis performance was controllable by adjusting the theoretical mass ratio of WO3/UCN. We have calibrated the optimal preparation conditions to be: WO3/UCN ratio as 1:1, the stirring time of the UCN and sodium tungstate mixture as 9 h and the volume of concentrated hydrochloric acid as 6 mL which was poured into the mixture solution with an extra stirring time of 1.5 h. The optimal photocatalyst WUopt had porous and wrinkled configurations. Its light absorption edge was 524 nm while that of UCN was 465 nm. The band gap of WUopt was 2.13 eV, 0.3 eV less than that of UCN. Therefore, the recombination rate of photo-generated electron-hole pairs of WUopt reduced significantly. The removal rate of WUopt on RhB was 97.3%. By contrast, the removal rate of UCN was much lower (53.4%). WUopt retained a high RhB removal rate, it was 5.5% lower than the initial one after being reused for five cycles. The photodegradation mechanism was facilitated through the strong oxidation behaviors from the active free radicals ·O2-, ·OH and h+ generated by WUopt under the visible light irradiation.

Phosphors Ba2 LaTaO6 :Mn4+ and its alkali metal charge compensation for plant growth illumination.

A series of Mn4+ -doped and Mn4+ ,K+ -co-doped Ba2 LaTaO6 (BLT) double-perovskite phosphors was synthesized using a high-temperature solid-state reaction. The phase purity and luminescence properties were also studied. The optimum doping concentration of Mn4+ and K+ was obtained by investigating the photoluminescence excitation spectra and photoluminescence emission spectra. The comparison of BLT:Mn4+ phosphors with and without K+ ions shows that the photoluminescence intensity of K+ -doped phosphors was greatly enhanced. This is because there was a charge difference when Mn4+ ions were doped with Ta5+ ions in BLT. Mn4+ -K+ ion pairs were formed after doping K+ ions, which hinders the nonradiative energy transfer between Mn4+ ions. Therefore, the luminescence intensity, quantum yield, and thermal stability of phosphors were enhanced. The electroluminescence spectra of BLT:Mn4+ and BLT:Mn4+ ,K+ were measured. The spectra showed that the light emitted from the phosphors corresponded well with chlorophyll a and phytochrome PR . The results show that the BLT:Mn4+ ,K+ phosphors had good luminescence properties and application prospects and are ideal materials for plant-illuminated red phosphors.

Toward Noise-Resistant Graph Embedding With Subspace Clustering Information.

Most existing approaches of attributed network embedding often combine topology and attribute information based on the homophily assumption. In many real-world networks, such an assumption does not hold since the nodes are usually associated with many noisy or irrelevant attributes. To tackle this issue, we propose a noise-resistant graph embedding method, called NGE, by leveraging the subspace clustering information (i.e., the formation of communities is driven by different latent features in distinct subspaces). Specifically, we first construct a tensor to represent a given attributed network and then map it into different feature subspaces to capture community structure via tensor decomposition. For structure embedding, the link-level and community-level constraints are imposed. For attribute embedding, the feature-selection constraint is used to reinforce the relationship between topology and noise-removal attributes. By learning structure and attribute embedding with subspace clustering information, NGE can benefit both community detection, link prediction, and node classification. Extensive experimental results have demonstrated the superiority of NGE over many state-of-the-art approaches.

Efficient Broadband Near-Infrared Emission from Lead-Free Halide Double Perovskite Single Crystal.

Ultra-broadband near-infrared (NIR) luminescent materials are the most important component of NIR light-emitting devices (LED) and are crucial for their performance in sensing applications. A major challenge is to design novel NIR luminescent materials to replace the traditional Cr3+ -doped systems. We report an all-inorganic bismuth halide perovskite Cs2 AgBiCl6 single crystal that achieves efficient broadband NIR emission by introducing Na ions. Experiments and density functional theory (DFT) calculations show that the NIR emission originates from self-trapped excitons (STE) emission, which can be enhanced by weakening the strong coupling between electrons and phonons. The high photoluminescence quantum efficiency (PLQY) of 51 %, the extensive full width at half maximum (FWHM) of 270 nm and the stability provide advantages as a NIR luminescent material. The single-crystal-based NIR LED demonstrated its potential applications in NIR spectral detection as well as night vision.

In Situ Embedding Synthesis of CsPbBr3@Ce-MOF@SiO2 Nanocomposites for High Efficiency Light-Emitting Diodes: Suppressing Reabsorption Losses through the Waveguiding Effect.

All-inorganic perovskite quantum dots (PQDs), which possess outstanding photophysical properties, are regarded as promising materials for optoelectronic applications. However, the poor light conversion efficiency and severe stability problem hinder their widespread applications. In this work, a novel encapsulation strategy is developed through the in situ growth of CsPbX3 PQDs in presynthesized mesoporous cerium-based metal organic frameworks (Ce-MOFs) and further silane hydrolysis-encapsulation, generating stable CsPbX3@Ce-MOF@SiO2 composites with greatly enhanced light conversion efficiency. Moreover, the simulation results suggest that the pore boundary of Ce-MOFs has a strong waveguide effect on the incident PQD light, constraining PQD light inside the bodies of Ce-MOFs and suppressing reabsorption losses, thus increasing the overall light conversion efficiency of PQDs. Meanwhile, the Ce-MOF@SiO2 protective shell effectively improves the stability by blocking internally embedded PQDs from the harmful external environment. Further, the obtained white-light-emitting diode shows an ultrahigh luminous efficiency of 87.8 lm/W, which demonstrates their great potential in optoelectronic applications.

A temperature sensor based on the enhanced upconversion luminescence of Li+ doped NaLuF4:Yb3+,Tm3+/Er3+ nano/microcrystals.

In this paper, fluorescent and optical temperature sensing bi-functional Li+-doping NaLuF4:Ln (Ln = Yb3+, Tm3+/Er3+) nanocrystals were synthesized via a simple hydrothermal method using oleic acid as a capping ligand. The crystal phase, size, upconversion (UC) properties, and optical temperature sensing characteristics of the crystals can be easily modified by Li+ doping. The results reveal that additional Li+ can promote the transformation from the hexagonal phase to the cubic phase and reduce the size of the nanocrystals. In addition, NaLuF4:Ln (Ln = Yb3+, Tm3+, Li+) nanocrystals present efficient near infrared (NIR) emission, which is beneficial for in vivo biomedical applications due to the increased penetration depth and low radiation damage of NIR light in bio-tissues. More importantly, under 980 nm excitation, the temperature dependent UCL from the 2H11/2 and 4S3/2 levels of Er3+ ions in NaLuF4:Yb3+,Er3+,Li+ microcrystals was investigated systematically. The fluorescence intensity ratios (FIR) of the pairs of thermally coupled levels were studied as a function of temperature in the range of 298-523 K. The maximum sensor sensitivities were found to be about 0.0039 K-1 (523 K) by exploiting the UC emissions from the 2H11/2 and 4S3/2 levels. This suggests that the Li+-doped upconversion luminescence (UCL) materials are promising prototypes for application as multi-mode probes for use in bio-separation and optical thermometers.

An upconversion luminescence and temperature sensor based on Yb3+/Er3+ co-doped GdSr2AlO5.

GdSr2AlO5:Yb3+/Er3+ micro-particles were synthesized by a simple solid state method. The structure, morphology, size and upconversion luminescence features have been characterized. These results indicated that GdSr2AlO5 has a contracted tetragonal cell and has irregular block shaped particles with sizes of about 5 µm. During upconversion, green (2H11/2, 4S3/2 → 4I15/2) (527 nm, 549 nm) and red (4F9/2 → 4I15/2) (665 nm) emissions had been observed, both of which occurred via a two-photon population process. In addition, green UC emission characteristics were studied, and it was found that its temperature ranged from 293 K to 473 K and the sensitivity was 0.0054 K-1 at 473 K. This indicated that GdSr2AlO5:Yb3+/Er3+ micro-particles may have potential application in high temperature environments for safety signs.

Emission in Gd6O5F8:Yb3+,Er3+ micro-particles for multimodal luminescence and temperature sensing upon 980 nm excitation.

Mono-dispersed Gd6O5F8:Yb3+/Er3+ micro-particles with different doping concentrations (Er3+: 0.1-1%) were synthesized by a facile hydrothermal route. The emission spectra, luminescent dynamic power-dependence and temperature sensing of up-conversion photoluminescence were investigated in detail. Under 980 nm excitation, the as-prepared samples exhibit intense red up-conversion and NIR emissions, which are influenced by the doping concentrations of Er3+ within Gd6O5F8. With increasing concentrations of Er3+ ions, the visible up-conversion emissions first increase and then decrease, but NIR down-conversion emissions display a distinct trend, in which one peak at 1010 nm is highly suppressed and another at 1530 nm is increased quickly. Furthermore, the 980 nm excited optical temperature sensing property of the synthesized sample is realized over a wide temperature range by monitoring the intensity of up-conversion luminescence. The study provides a novel strategy based on lanthanide oxy-fluoride micro-particles for multifunctional displays, lighting and temperature sensing in a single system.