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Pb2+-doped Cs2Mn(Cl/Br)4·2H2O PA NCs exhibit excellent luminescence properties and stability, and can be used in fibers and other uses.

Cs2Sn1−xTexCl6 crystals are synthesized and can be used for post-processing fibers for LED and anti-counterfeiting materials.

The photoluminescence spectra of Ca2La2.85−x(SiO4)3F:0.15Tb3+,xSm3+ phosphors (left) could emit typical multicolor light with increasing doping contents of samarium (right).

Single-component white-light-emitting phosphors based on resonance energy transfer exhibit ultra-high Ra and appropriate CCT.

In this paper, a novel cryolite-type up-conversion luminescent material K3Sc0.5Lu0.5F6: Er3+, Yb3+ with controllable crystal form was synthesized by a high temperature solid state method. K3Sc0.5Lu0.5F6: Er3+, Yb3+ can crystallize in monoclinic or cubic form at different temperatures. The composition, structure and up-conversion luminescence (UCL) properties of K3Sc0.5Lu0.5F6: Er3+, Yb3+ samples with different crystal form were investigated in detail. It is impressive that both monoclinic and cubic forms of K3Sc0.5Lu0.5F6: Er3+, Yb3+ show green emission (2H11/2/4S3/2→4I15/2). The luminescence intensity of cubic K3Sc0.5Lu0.5F6 is much higher than that of the monoclinic form, and the reasons are also discussed in detail. The results show that the luminescence intensity of up-conversion materials can be effectively tuned by controlling the crystal form. According to the power dependent UCL intensity, the UCL mechanism and electronic transition process were discussed. In addition, the fluorescence decay curves were characterized and the thermal coupling levels (TCLs) of Er3+ (2H11/2/4S3/2 → 4I15/2) in the range of 304–574 k were used to study the optical temperature sensing characteristics. All the results show that K3Sc0.5Lu0.5F6: Er3+, Yb3+ can be used in electronic components and have potential application value in temperature sensing fields.

Photocatalysis can effectively solve environmental pollution and energy supply problems by using inexhaustible sunlight. It is crucial to design high-efficiency photocatalysts with strong light-absorbing capability, strong redox potentials, high charge separation and excellent durability. Bismuth-based materials have unique crystal structures, electronic configurations and environmental friendliness. However, insufficient light absorption and charge separation greatly limit their application. Inspired by natural photosynthesis, the construction of artificial Z-scheme photocatalysts provides a feasible strategy to overcome these bottlenecks. This review mainly concentrates on the construction mechanism and structure genre of bismuth-based Z-scheme photocatalytic systems, including the liquid-phase Z-scheme photocatalytic system, all-solid-state Z-scheme photocatalytic system with a mediator, and direct Z-scheme photocatalytic system, and their applications in water splitting, CO2 reduction and pollutant degradation are summarized. The different reaction mechanisms in various applications are discussed in detail. Finally, challenges and opportunities are proposed to develop more efficient bismuth-based Z-scheme photocatalysts.

In recent years, synthetic apatite-doped rare-earth luminescent materials and their optical properties have attracted extensive worldwide attention. In this study, a series of novel green phosphors Sr2Y3(SiO4)2(PO4)O:Eu2+ with apatite structure was fabricated via a high temperature solid-state reaction. X-ray diffraction, structure refinement, photoluminescence excitation, emission spectra, and temperature-dependent emission intensity were employed to describe the phase and property of the samples. Under the excitation of 365 nm, the phosphors emit strong green emission in the broad band range from 400 nm to 700 nm, which almost covers the visible light spectrum. The quenching concentration of Eu2+ in Sr2Y3(SiO4)2(PO4)O was about 0.05, which was attributed to the dipole–dipole interactions. The evidence that the as-prepared phosphor can be successfully excited by near ultraviolet light indicates that it can be potentially used as a near UV-convertible phosphor for white light-emitting diodes.

Cryolite is a suitable host for up-conversion luminescent materials due to its low phonon energy and good optical transparency. In this work, a novel up-conversion material K3YF6:Yb3+, Er3+ with a cryolite structure was prepared successfully by a solid state method. The crystal structure, morphology, composition and up-conversion luminescence properties of the as-prepared sample were characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (SEM) and fluorescence spectrometer in detail. K3YF6:Er3+, Yb3+ has a cryolite structure. Under 980 nm excitation, the as-prepared sample can generate slight green emission at 524 and 546 nm (attributed to 2H11/2 → 4I15/2 transition, 4S3/2→4I15/2 transition of Er3+) and strong red emission at 661 and 672 nm (corresponding to 4F9/2 → 4I15/2 transition, 4I9/2 → 4I15/2 transition of Er3+). All the green and red up-conversion emission of K3YF6:Er3+, Yb3+ transfer and electronic transition process of the red and green light the sample emitted, the possible luminescence mechanism is discussed in this paper.

A new kind of multicolor phosphor Ba2La3(GeO4)3F:0.15Tb3+,xEu3+ (BLGOF:0.15Tb3+,xEu3+) has been acquired through the traditional high temperature solid phase synthesis method. The structural information of the phosphor was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rietveld refinement. The optical properties of the phosphor have also been studied in detail, including its photoluminescence spectra (PL), photoluminescence excitation spectra (PLE), fluorescence decay curves, energy transfer mechanism and thermal quenching spectra. It has been found that the optimum concentration of Eu3+ in BLGOF:0.15Tb3+,xEu3+ is 0.24 mol and the energy transfer mechanism from Tb3+ to Eu3+ in BLGOF is quadrupole–quadrupole. The color of BLGOF:0.15Tb3+,xEu3+ phosphors can be changed from green to yellow/orange to red. Some details of the energy transfer are reviewed and the effect of complex anion regulation on thermal stability has also been studied. All the properties are good and can contribute to the promotion from the laboratory to practical application for the phosphor.

Single-phase CaSr2(PO4)2:Sm3+,Li+ phosphors were prepared via a high-temperature solid-state method under air. The powder X-ray diffraction patterns, scanning electron microscopy images, photoluminescence spectra, and concentration-dependent emission spectra were measured to characterize the as-prepared phosphors and luminescence decay curves. The results showed that the CaSr2(PO4)2:Sm3+,Li+ phosphors exhibited red luminescence, and the emission spectra of the phosphors consisted of four sharp peaks at around 565, 601 (the strongest one), 647 and 707 nm. The optimum doping concentration of Sm3+ ions was 0.09 (mol concentration), and the mechanism of energy transfer among Sm3+ ions was defined to be quadrupole–quadrupole (q–q) interactions using Dexter's theory. The Blasse concentration quenching method was used to determine the critical distance Rc for energy transfer among Sm3+ as 10.99 A. The results indicate that the as-prepared phosphors have good thermal stability with an activation energy of 0.773 eV via temperature-dependent emission spectra. Therefore, CaSr2−2x(PO4)2:xSm3+,xLi+ materials can be used as red-emitting phosphors for UV-pumped white-light emitting diodes.

We develop a facile and rapid cation exchange method for upconversion nanocrystals (UCNCs) without removing surface ligands. It avoids the tedious pretreatment of as-synthesized UCNCs, and the luminescent intensities of nanocrystals after Tb3+ exchange using the new method are much stronger than those of the nanocrystals obtained using conventional cation exchange in water.

In this study, we investigated the structure, luminescence properties and morphology of La6Ba4(SiO4)6F2:Dy3+ in detail using X-ray diffraction (XRD), photoluminescence spectroscopy, scanning electron microscopy (SEM) and decay kinetics measurements. The results indicate that La6Ba4(SiO4)6F2:Dy3+ was well crystallized, and its structure is of apatite-type and belongs to the hexagonal system. The prepared samples exhibit two intense characteristic bands in the blue (484 nm) and yellow (579 nm) spectral ranges corresponding to the Dy3+ transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2, respectively. These dominant photoluminescence bands are accompanied by a weak red band (670 nm) due to the 4F9/2 → 6H11/2 transition. The emission color of La6Ba4(SiO4)6F2:Dy3+ phosphors are found to fall in the white light region. The Dy3+ optimal dopant concentration in the La6Ba4(SiO4)6F2 host was found to be 0.12 (mol). In addition, the phosphors have high thermal stability. Hence, La6Ba4(SiO4)6F2:Dy3+ may have an application in white light-emitting diodes.

The integration of flexible carbon-based materials and high capacity anode materials is an effective route to obtain superior flexible electrode materials. In this work, nickel sulfide nanoparticles were electrodeposited on a CNT thin film to form a paper-like composite (NS@CNT). As a binder-free flexible Li-ion battery anode, a record specific capacity to date of ∼845 mA h g−1 at a current density of 60 mA g−1 in terms of the mass of the composite has been achieved. The high capacities were mainly attributed to reversible conversion reactions of nickel sulfide and the capacitance effect of the nanostructured composite.

As most heavy metals are highly toxic upon accumulation in the human body, it is urgent to develop accurate, low-cost, and on-site methods to detect multiple heavy metal ions in real water samples. Quantum dots (QDs) are an approved choice for use in sensors and exhibit favorable luminescence in aqueous solution, but they often become quenched when isolated from their suspensions due to agglomeration. Therefore, QDs must exist in a solid state in order to be successfully applied to luminescence detection. This work reports the fabrication of a novel luminescence composite based on glutathione-capped Mn-doped ZnS quantum dots (GSH-Mn-ZnS QDs) and layered double hydroxides (LDH). The composite is solid and exhibits enhanced luminescence intensity, as the structure of LDH prevents the aggregation of QDs. Most importantly, it exhibits a similar response when used as a sensor for detecting Pb2+, Cr3+ and Hg2+ with a linear range of 1 × 10−6 M to 1 × 10−3 M for each heavy metal, and a detection limit for the mixed metal ions of 9.3 × 10−7 M. In addition, the composite was successfully applied for detection in lake water with low interference. Therefore, a practical method is presented for the design and fabrication of a QD–LDH composite that can be used for qualitative and quantitative testing of mixed heavy metal ions simultaneously in real water samples.

A novel single-phase white light emitting phosphor Ca9La(PO4)5(SiO4)F2:Dy3+ was prepared through traditional high-temperature solid state technology. The crystal structures of Ca9La(PO4)5(SiO4)F2 with or without Dy3+ ions were refined by the Rietveld method. The diffuse reflection spectra, excitation spectra, emission spectra, and decay times were characterized to investigate the photoluminescence properties for application in white light-emitting diodes. The results showed that the Ca9La(PO4)5(SiO4)F2:Dy3+ phosphor could efficiently assimilate n-UV light and emit blue (∼485 nm) and yellow light (∼580 nm), originating from the f–f transitions of Dy3+. The critical Dy3+ quenching concentration (QC) was determined to be about 15 mol%, and the corresponding QC mechanism was verified to be the dipole–dipole interaction. Additionally, the emission colors of all samples were located close to the ideal white light region, and the optimal chromaticity coordinates and correlated color temperature (CCT) were determined to be (x = 0.338, y = 0.336) and 5262 K. All the above results indicate that the as-prepared Ca9La(PO4)5(SiO4)F2:Dy3+ phosphor could serve as a promising candidate for white-light n-UV-LEDs.

A series of novel emission-tunable ScPO4:xTb3+, yEu3+ phosphors were prepared by a high temperature solid-state reaction. The phase purity was examined using X-ray diffraction refinement. X-ray photoelectron spectroscopy (XPS) and the crystal information, luminescence properties and energy transfer between Tb3+ and Eu3+ are analyzed systematically. The cross relaxation from 5D3 to 5D4 of single doped Tb3+ in the host is investigated. The energy transfer between Tb3+ and Eu3+ has been demonstrated by the decay times, which are ascribed to the dipole–dipole (d–d) mechanism, and the ηT reaches 54.4%. Additionally, the energy transfer critical distance between Tb3+ and Eu3+ was calculated to be about 12.95 A. The emission color can be adjusted from green to yellow to orange-red by tuning the ratio of Tb3+/Eu3+. The ScPO4:0.03Tb3+, 0.025Eu3+ exhibits good thermal stability, indicating its great potential in w-LED applications.

The lutetium containing nitride apatite Lu5(SiO4)3N was prepared by a solid state reaction at high temperature for the first time. Rietveld refinement indicated that the Lu5(SiO4)3N compound has a hexagonal space group of P63/m with cell parameters a = b = 9.700 Å and c = 7.238 Å. Additionally, the results revealed that there are two distinct lutetium sites in the Lu5(SiO4)3N host lattice, i.e. a Lu(1) site with nine coordination (Wyckoff site 4f) and a Lu(2) site with seven coordination (Wyckoff site 6h). Furthermore, the ratio of the number of Lu atoms in Lu(1) and Lu(2) sites is 3 : 2. The band gap for Lu5(SiO4)3N was determined to be 4.12 eV based on the density functional theory (DFT). In the Ce(3+) doped Lu5(SiO4)3N:0.03Ce(3+) compound, the emission peak centered at 462 nm was observed with the Commission International de I'Eclairage (CIE) coordinates of (0.148, 0.184), indicating blue-emission. Remarkably, in Ce(3+) and Tb(3+) co-doped Lu4.97-y(SiO4)3N:0.03Ce(3+),yTb(3+) compounds, the color-tunability was observed with increasing Tb(3+) co-doping rate on moving from blue at Tb(3+) = 0.00 to green at Tb = 0.09, due to the energy transfer from Ce(3+) to Tb(3+) ions being matched well with the decay curve results. Under the excitation at 359 nm, the absolute quantum efficiency (QE) for Lu5(SiO4)3N:0.03Ce(3+) was determined to be 42.13%. This phosphor material could be a platform for modeling a new phosphor and application in the solid-state lighting field.

A novel apatite phosphor Ca6La4(SiO4)2(PO4)4O2:Eu2+ was prepared by conventional high-temperature solid-state reaction. Phase purity was examined by XRD and XPS analysis. The crystal structure information, such as space group, cell parameters and atomic coordinates, were refined by the Rietveld method, revealing that Eu2+ occupied the sites of Ca2+ ions. Moreover, low-temperature experiments, including low-temperature PL spectra and low-temperature decay curve, were used to prove the existence of two luminescence centers in Ca6La4(SiO4)2(PO4)4O2:Eu2+. With the increase in doping concentration of Eu2+, the emission wavelength shows a red shift from 498 nm to 510 nm, which is mainly caused by the increase in crystal-field splitting by Eu2+. The optimized concentration of Eu2+ was confirmed to be 0.01, the Rc was calculated to be 20.09 A and the energy transfer between Eu2+ was demonstrated to be by exchange interaction. Moreover, good thermal stability has been proved by a temperature-dependence experiment; it shows that the phosphor can maintain 55% of emitting intensity at 150 °C compared to that at room temperature. Finally, the Ca6La4(SiO4)2(PO4)4O2:Eu2+ phosphor was fabricated with commercial red (CaAlSiN3:Eu2+) and blue (BAM:Eu2+) phosphor coating on a n-UV chip. This proves that this green phosphor has the potential to be used in a w-LED lamp.

Eu2+- and Mn2+-co-doped KMg4(PO4)3 phosphors were prepared via conventional high temperature solid-state reactions. Their crystal structures, luminescence properties, emission red shifts, and energy transfer between Eu2+ and Mn2+ were investigated systematically. Under excitation at 365 nm, KMg4(PO4)3:Eu2+,Mn2+ phosphors exhibited a broad excitation band ranging from 250 to 425 nm and two broad emission bands that peaked at 450 nm and 625 nm, which were ascribed to the 4f–5d transition of Eu2+ and the 4T1 → 6A1 transition of Mn2+ ions, respectively. Three emission bands of Mn2+ were observed in KMg4(PO4)3: Eu2+,Mn2+, which can be attributed to the disordering of Mn2+ in the Mg2+ sites to form different luminescence centers. The energy transfer between the Eu2+ and Mn2+ ions is of a resonant type via a dipole–quadrupole mechanism. The emission red shift that takes place with increasing Mn2+ concentration and operating temperature are discussed in relation to the crystal structure and energy transfer in KMg4(PO4)3:Eu2+,Mn2+. Utilizing the redshift and the energy transfer from Eu2+ to Mn2+, KMg4(PO4)3:Eu2+,Mn2+ phosphors can be tuned from blue to pink by appropriate adjustment of the Mn2+ content and may have potential application for white light-emitting diodes and plantlet culturing.

Up-conversion (UC) phosphors of (Ca1−xSrx)In2O4 : Yb3+/Ho3+ (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) were prepared. Based on the crystal structure evolution of these series solid solution samples, which were characterized by Rietveld refinement, the variation of UC luminescent properties was discussed in detail. Sr and Ca occupied one position and Yb/Ho dissolved in the In ion site in the (Ca1−xSrx)In2O4 lattice. With increasing Sr substituting Ca atoms, the cell parameters and cell volumes of these samples increased linearly, and distortions of (Ca/Sr)O8 polyhedron were formed. The distortions on crystal structures showed a negative relation with UC luminescent intensities in these series phosphors.

Up-conversion (UC) phosphors Gd2(WO4)3:Er3+/Yb3+ were synthesized by a high temperature solid-state reaction method. The crystal structure of Gd2(WO4)3:3% Er3+/10% Yb3+ was refined by Rietveld method and it was showed that Er3+/Yb3+ were successfully doped into the host lattice replacing Gd3+. Under 980 nm laser excitation, intense green and weak red emissions centered at around 532 nm, 553 nm, and 669 nm were observed, which were assigned to the Er3+ ion transitions of 4H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively. The optimum Er3+ doping concentration was determined as 3 mol% when the Yb3+ concentration was fixed at 10 mol%. The pump power study indicated that the energy transfer from Yb3+ to Er3+ in Er3+, Yb3+ co-doped Gd2(WO4)3 was a two-photon process, and the related UC mechanism of energy transfer was discussed in detail.