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A new kind of apatite-type red-emitting Ba2La8(GeO4)6O2:Eu3+ phosphor was prepared by high temperature solid-state method. The Rietveld analysis based on the powder diffraction data shows that Ba2La8(GeO4)6O2:Eu3+ phosphors possess a pure apatite phase without any impurity. The emission spectrum of Ba2La8(GeO4)6O2:Eu3+ phosphor consists of two bands, an orange emission band from 500 to 600 nm and a red emission band from 600 to 680 nm. By varying the amount of the doped europium ions from 0.02 to 0.14 mol, it is found that the luminescent properties of this rare earth phosphor are the best when the concentration of europium ion is 0.08 mol. The optimum concentration is eventually proved to be 0.08 mol. The Eu3+ doping dependent luminescence quenching can be further ascribed to dipole–quadrupole interactions. The quantum yield of Ba2La7.92(GeO4)6O2:0.08Eu3+ is 37.23%. The CIE analysis confirms a reddish emission in the near ultraviolet (n-UV) excitation. All these above properties of the phosphor can help in contribution of promoting white light-emitting diode.

Tb3+,Dy3+-co-doped Ca9TbxDy1–x(PO4)5(SiO4)F2 phosphors were prepared via high-temperature solid-phase reaction method and the potential application in optical temperature measurements due to their color-tunable property was investigated in detail. The photoluminescence emission (PL) and photoluminescence excitation (PLE) spectra results show that the as-prepared phosphors exhibit both Tb3+ and Dy3+ emissions at 546 nm (5D4–7F5 transition of Tb3+) and 587 nm (4F9/2–6H13/2 transition of Dy3+) upon 376 nm excitation, respectively. In addition, the fluorescence decay analysis shows that the lifetime of the Tb3+ emission rapidly decreases, which confirms the energy transfer existence between Dy3+ and Tb3+. Under 376 nm excitation, the temperature dependence of the fluorescence intensity ratios for the dual-mission bands peaked at 546 and 587 nm was studied in the temperature range from 303 to 573 K. The results show that with the increase of Dy3+ concentration, the relative sensitivity first increases and then decreases, what's more, the maximum relative sensitivity is 3.142 × 10−3%/K for Ca9TbxDy1–x(PO4)5(SiO4)-F2 (x = 0.4). As a consequence, this preliminary study provides a novel method for exploring the novel thermometers.

Novel scheelite structures of Li2Ca(WO4)2, Li2Ca2(WO4)(SiO4), and LiCa2(WO4)(PO4) fluorescent materials were successfully prepared using a high-temperature solid-phase process. The compounds were characterized by X-ray diffraction and energy dispersive spectroscopy. The tests revealed that the substitution of [WO4]2− by [SiO4]4− or [PO4]3− tetrahedron in tungstate had no significant influence on the crystal structure of the Li2Ca(WO4)2. When Dy3+ ions were introduced as an activator at an optimum doping concentration of 0.08 mol%, all of the as-prepared phosphors generated yellow light emissions, and the emission peak was located close to 576 nm. Replacing [WO4]2− with [SiO4]4− or [PO4]3− tetrahedron significantly increased the luminescence of the Li2Ca(WO4)2 phosphors. Among them, the LiCa2(WO4)(PO4):0.08Dy3+ phosphor had the best luminescence properties, decay life (τ = 0.049 ms), and thermal stability (87.8%). In addition, the as-prepared yellow Li2Ca(WO4)2:0.08Dy3+, Li2Ca2(WO4)(SiO4):0.08Dy3+, and LiCa2(WO4)(PO4):0.08Dy3+ phosphor can be used to fabricate white light emitting diode (LED) devices.

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.

Although transition-metal sulfides have emerged recently as a type of promising candidate to serve as lithium-ion battery anodes, the chemical synthesis of transition metal-sulfide materials usually involves a complex operation process and is time-consuming. The natural transition metal-sulfide minerals are potential materials for lithium-ion battery electrodes because of their abundant reserves and cost savings of the synthesis process. The synthesis of nanosized transition metal-sulfide-based materials from natural bulk minerals remains challenging. In our work, we demonstrate that a composite of ~ 10–50-nm ZnS nanoparticles that are anchored on reduced graphene-oxide nanosheets can be synthesized by using bulk natural sphalerite in a simple, rapid and pollution-free microwave shock method. As anode electrode, this composite exhibited a high reversible specific capacity (~ 611 mAh g−1 at 0.1 C), good rate performance and good cycling stability. This work provides a route for the high-value utilization of natural minerals.

Using low-cost precipitated silica (SiO2) as the carrier, a ternary SiO2-TiO2/g-C3N4 composite photocatalyst was prepared via the sol-gel method associated with a wet-grinding process. The as-prepared composite exhibits photocatalytic hydrogen production and pollutant degradation performance under solar-like irradiation. The effect of SiO2 carrier on the properties of the heterostructure between TiO2 and g-C3N4 (CN) was systematically studied. It is found that SiO2 has important effects on promoting the interaction between TiO2 and CN. The particle size of TiO2 and CN was obviously reduced during the calcination process due to the effects of SiO2. Especially, the TiO2 particles exhibit monodispersed state with particle size below 10 nm (quantum dots), resulting in the improvement of the contact area and the interaction between TiO2 and CN, and leading to the formation of efficient TiO2/CN Z-scheme heterostructure in SiO2-TiO2/CN. Besides, the introduction of SiO2 can increase the specific surface area and light absorption of SiO2-TiO2/CN, further promoting the photocatalytic reaction. As expected, the optimum SiO2-TiO2/CN composite exhibits 12.3, 3.1 and 2.9 times higher photocatalytic hydrogen production rate than that of SiO2-TiO2, CN and TiO2/CN under solar-like irradiation, while the photocatalytic active component in SiO2-TiO2/CN is only about 60 wt%. Moreover, the rhodamine B degradation rate of SiO2-TiO2/CN is also higher than that of SiO2-TiO2, CN and TiO2/CN.

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.

As promising low-dimensional semiconductor materials, cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite-like nanowires (NWs) can be widely applied to the field of semiconductor devices and integrated optoelectronics. Therefore, developing a facile and efficient synthesis method of cesium lead halide perovskite-like NWs can bring both fundamental and practical impacts to the field of optoelectronics. Here, we developed a synthesis strategy of all-inorganic cesium lead halide CsPbI3 perovskite-like NWs under catalyst-free, solution-phase, and low-temperature conditions. The synthesis strategy was designed such that no inert gas is required and thus enables the synthesis to be carried out in air, which significantly reduces temperature, steps, time, and cost required for the reaction. The as-synthesized NWs were 7 μm in length and 80–100 nm in diameter with ideal morphology. Most of the CsPbI3 NWs were crystallized in orthorhombic phases that were arranged orderly with a uniform growth direction. In addition, the CsPbI3 NWs showed a photoluminescence peak near 610 nm and the fluorescence lifetime was 7.34 ns. The photoluminescence mechanism of CsPbI3 NWs involves the self-trapping behaviour in the radiative recombination process. The composition of CsPbI3 NWs is highly related to the synthesis temperature. The facile synthesis strategy has opened up a novel path for the synthesis of perovskite-like NWs, laying the foundation for the application of nano-optoelectronic devices, fluorescent anti-counterfeiting, and fluorescent composite materials.

Installing thermal insulation materials on the external and/or interior wall is a primary means for the conservation of building energy. Expanded perlite is one of the most widely used inorganic building insulation materials nowadays. However, it not only consumes a large amount of energy in the fabricated process, but also produces a great deal of perlite tailings during the exploiting or smashing process. In this work, a new kind of light foamy thermal insulation materials were prepared utilizing perlite tailings by an energy-saving and environment-friendly method. The influences of each raw materials, including perlite/sodium silicate, H2O2, cetyltrimethyl ammonium bromide and rock wool, on the physical properties (such as pores characters, thermal conductivity and mechanical strength) were discussed in detail based on the formation processes of the foamy thermal insulation materials. The optimized foamy materials showed low thermal conductivities (0.040–0.060 W·m−1·K−1) with low apparent densities (0.1–0.2 g cm−3) and relatively high mechanical strength (0.09–0.6 MPa). As compared with other reported inorganic thermal insulation materials, this new type of thermal insulation material was very light and exhibited much better heat-insulated performance. Therefore, this work not only proposed a new energy-saving method for obtaining a kind of promising non-flammability insulating materials, but also solved the problem of solid tailings utilization.

A novel orange-red emitting orthosilicate phosphor LiGd9(SiO4)6:Mn2+ (LGS:Mn2+) belongs to hexagonal lattice with P63/m space group was synthesized via solid-state method and the phase composition, crystal structure as well as luminescence properties were examined for potential application in near ultraviolet (n-UV) pumped white light emitting diodes (w-LEDs). The as-prepared LGS:Mn2+ phosphor exhibits three excitation bands peaked at 273, 312 and 410 nm, which corresponds to the transitions of Gd3+ from ground state 8S7/2 to 6I7/2, 6P7/2 and Mn2+ from ground state 6A1(6S) to the individual components of the multiplets [4A1(4G), 4E(4G)], respectively. Upon excitation at 312 nm, the phosphors display an intense broad orange-red emission peaked around 594 nm, which ascribed to the typical spin-forbidden transition (4T1(4G)-6A1(6S)) of the Mn2+ ions. The concentration quenching mechanism and average separation distance in conjunction with fluorescence decay times of Mn2+ ions in LGS:Mn2+ phosphor were discussed. The indispensable parameters for application in n-UV high-powered w-LEDs, such as the thermal quenching of photoluminescence and internal quantum efficiency of LGS:Mn2+ phosphor, have also been investigated in detail. The above results indicate that LGS:Mn2+ could play a key role as an orange-red emission for potential application in n-UV-based w-LEDs.

A series of reddish-emitting apatite-type phosphor LiGd9(SiO4)6O2:Sm3+ was prepared by using an appropriate solid-state method. The photoluminescence (PL), photoluminescence excitation (PLE) spectra, and decay times of the samples were characterized to investigate the photoluminescence properties for application in white light-emitting diodes (w-LEDs). The photoluminescence investigations showed that LiGd9(SiO4)6O2:Sm3+ phosphor emitted reddish emission, which ascribed to the transitions of the Sm3+ from the 4G5/2 excited state to the 6H5/2, 6H7/2, and 6H9/2 states, respectively. The critical quenching concentration of Sm3+ in LiGd9(SiO4)6O2 phosphors were determined to be about 3 mol%. Moreover, the spectroscopic data and fluorescence decay dynamics indicate that the energy transfer from Gd3+ to Sm3+ ions takes place in LiGd9(SiO4)6O2: Sm3+ phosphor. All the results indicated that the LiGd9(SiO4)6O2: Sm3+ phosphor could efficiently assimilate the near ultraviolet (n-UV) light and act as a suitable warm light candidate for n-UV w-LEDs.

A set of Eu3+, Dy3+ and Tb3+ doped novel scheelite-type LiCaGd(WO4)3 (LCGW)-based phosphors was prepared via a conventional solid-state reaction method. The X-ray diffraction (XRD), transmission electron microscopy (TEM) analysis, characteristics of luminescence, PL thermostability, decay lifetimes, as well as CIE coordination were investigated to characterize the as-prepared samples in detail. The XRD analysis indicated that the Eu3+, Dy3+ and Tb3+ ions were incorporated into the LCGW host lattice. Under the ultraviolet radiation, the characteristic emission lines of Eu3+ (5D0–7F2), Dy3+ (4F9/2–6H13/2) and Tb3+ (5D4–7F5) ions were observed. The Eu3+ and Tb3+ single-doped LCGW fluorescent powders showed bright red and green emissions, respectively, without concentration quenching. As well as the Dy3+ doped LCGW phosphors radiate a strong yellow light at optimal Dy3+ concentration 0.08 mol. The efficient energy transfer phenomenon was observed for the Eu3+/Dy3+ and Tb3+/Dy3+ ions. The emission color of the LCGW:xTb3+/0.08Dy3+ samples was tuned from yellow (0.4074, 0.4727) to green (0.3604, 0.5521) via adjusting the Tb3+ concentration. The emission color of LCGW:yEu3+/0.08Dy3+ can be tuned from yellow (0.491, 0.3856) to red (0.5694, 0.3512) by variation of the Eu3+/Dy3+ ratio. Additionally, the thermal stability of the luminescence in the LCGW phosphors doped by Eu3+, Tb3+, Dy3+ ions was studied. The results verified that the LCGW:Ln3+ (Ln = Tb, Eu, Dy) phosphors are promising for applications in white LEDs.

Cryolite has been considered as an appropriate host for up-conversion materials due to its low phonon energy, wide light transmission range, easy to form waveguide and stable structure. In this paper, a series of up-conversion materials Cs3YF6: Er3+, Yb3+ with cryolite structure were prepared by high-temperature solid-phase method. The structure, morphology, element composition and up-conversion luminescence properties of as-prepared samples were characterized. In addition, the number of photons absorbed during the up-conversion process and the possible up-conversion luminescence mechanism are analyzed in detail. Under the excitation of 980 ​nm, the Cs3YF6: Er3+, Yb3+ sample emits strong green light visible to the naked eye. Simultaneously, the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) were calculated. All the results indicated that Cs3YF6: Er3+, Yb3+ has potential applications in the fields of green light display and temperature sensing.

Because the commercialized graphitic carbon as an anode material is still limited by low capacities and poor long cyclic stability, new carbonaceous materials with good electrochemical performance are still needed to be sought. In the present work, a new fluorinated carbon material was obtained from natural black talc ore by HF acid-treating method. The influences of heat treatment on the composition, morphology and structure characteristics of the fluorinated carbon were investigated and possible fluorination/defluorination mechanisms were proposed. As an anode material for Li-ion battery, the electrochemical performance of the samples was greatly influenced by their surface characteristics. The fluorinated carbon showed high capacities of ∼756 mAh/g and ∼620 mAh/g at rate of 0.1 C and 0.2 C, which resulted from more active sites provided by plenty of fluoride groups on the surface of the fluorinated carbon. In contrast, the sample annealed at 800 °C exhibited relatively high capacity of ∼477 mAh/g at rate of 0.1 C with excellent rate performance due to its better electrical conductivity caused by the removal of the fluorine groups. The present work provides a new direction for the application of black talc and other similar natural minerals.

A novel cerium doped compounds Mn3Gd7–xCex(SiO4)6O1.5 with an apatite structure was found and used to achieve high-efficiency degradation of tetracycline in aqueous solution. The catalysts were characterized by XRD, XPS, EDS and other techniques. The characteristic results indicated that the catalytic activity of the compound was improved due to the introduction of Ce in the structure, because Ce3+ which was stably present in the apatite structure can serve as an active site for the reaction, and in addition, there was a high presence between Ce4+ and Ce3+ on the surface of the catalyst. The redox potential and high oxygen storage capacity were also beneficial for the catalytic reaction. The results of free radical capture indicated that both superoxide radicals and hydroxyl radicals participated in the catalytic oxidation process and played an important role in the reaction. The decomposition of tetracycline followed the pseudo second-order reaction kinetics. In addition, the catalyst exhibited long-term stability and low metal leaching during the reaction, which indicated that the novel cerium-doped apatite structure material could be a promising wastewater treatment material.

Samarium (III) doped fluorapatite phosphors La6-xBa4(SiO4)6F2: xSm3+ (LBSF: Sm3+) were synthesized for the first time, via the conventional high-temperature solid-state method in the air atmosphere. The samples were measured by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy, i.e. emission and excitation spectra, as well as luminescence decay curves. The as-prepared samples can be excited in the range from 300–500 nm, centered at 404 nm. Photoluminescence measurements showed the emission spectra are composed of four sharp peaks characteristic of Sm3+ ions, at about 565, 603, 650 and 711 nm. The critical concentration for quenching of Sm3+ ions in the LBSF matrix is about 0.12 mol. According to the Dexter's theory, the mechanism of energy transfer between Sm3+ ions was considered to be dipole-quadrupole (d-q) interactions, with the critical distance calculated by the concentration quenching method to 9.89 A. Moreover, the temperature-dependent emission spectra showed that the as-prepared phosphors have good thermal stability, with an activation energy of about 0.161 eV. Finally, according to the CIE coordination, the phosphor exhibited reddish-orange emission. Thanks to the mentioned favorable structural and optical properties, the Sm3+-doped La6Ba4(SiO4)6F2 phosphors have a potential application character, for the near ultraviolet white light emitting diodes.

In this study, an organic dye lucigenin (BNMA) was successfully intercalated into the interlayer of montmorillonite (MMT) to prevent fluorescence quenching. With its enhanced fluorescent property, the composite was fabricated into solid strips for it fast and sensitive phenol detection in both liquid and gas phases. Under proper optimizations it is anticipated that the composite would show great potential for phenol determination in real world environment such as wastewater treatment industry.

Er3+ / Yb3+ doped BaIn2O4 up-conversion (UC) phosphors are synthesized and their UC luminescent properties are characterized. BaIn2O4 has P21/c space group but Rietveld refinement suggests it has twice smaller cell parameter (a = 10.3975 A, b = 5.8295 A, c = 14.4457 A) and volume than previous reported structure. Refinement also reveals Er3+/Yb3+ replaces In3+ ions in lattice because of the existence of InO6 octahedra. In these BaIn2O4 phosphors, co-doping with Yb3+ ions changes the predominant UC emission from green ( 2H11/2, 4S3/2 → 4I15/2 of Er3+) to red (about 665 nm, 4F9/2 → 4I15/2 of Er3+). By controlling of Er3+/Yb3+ concentrations, the BaIn2O4 phosphors have the potential of generating various UC spectra and color tunability. The pumping powers study shows two-photon process in these phosphors.

Cryolite was considered to be an ideal up-conversion host material due to its low phonon energy, which can effectively suppress the radiation-free transition process of excited state energy levels. In the present paper, a novel up-conversion material K3YF6:Ho3+, Yb3+ with cryolite structure was prepared successfully using a high-temperature solid state method. The up-conversion luminescence properties of K3YF6 doped with different Ho3+/Yb3+ doping ratio were investigated and the optimal doping ratio were confirmed in this system. Under 980 nm excitation, Ho3+/Yb3+ co-doped K3YF6 revealed a strong green emission at the 541 nm, 549 nm and a weak red emission peaking at 666 nm, corresponding to the 5F4, 5S2→5I8 and 5F5→5I8 transitions of Ho3+, respectively. All the red and green up-conversion emission of K3YF6:Ho3+, Yb3+ belong to two-photon process and energy transfer from Yb3+ to Ho3+ simultaneously. Additionally, to understand the energy transfer and electronic transition process of the red and green light emitted, the possible luminescence mechanism were also analyzed in this paper. All the results indicate that Ho3+/Yb3+ co-doped K3YF6 have potential application value in green up-conversion luminescent materials.

A series of novel luminescent emission-tunable phosphors Mg2La8(SiO4)6O2:Ce3+,Tb3+ (MLS:Ce3+,Tb3+) have been prepared by a solid-state reaction. The phase formation was firstly confirmed through X-ray diffraction technique and refined by the Rietveld method. The MLS:Ce3+,Tb3+ phosphors, which crystallized in apatite-type hexagonal phase, exhibited a broad excitation band ranging from 200 to 400 nm and several emission bands centered at 426 nm and 551 nm. Energy transfer from Ce3+ to Tb3+ ions via a dipole-dipole mechanism occurred in the as-synthesized phosphors upon ultraviolet (UV) excitation. The energy transfer efficiency increases with increasing doping content of Tb3+ ions, which was confirmed by the luminescence spectra and fluorescence decay curves of corresponding ions simultaneously. The energy transfer critical distance was calculated and evaluated by both the concentration quenching and spectral overlap methods. The chromaticity of emission-tunable phosphors was also characterized by the Commission International de l'eclairage (CIE) chromaticity indexes, and the color tone can be tuned from blue (0.179, 0.122) to green (0.267, 0.408) by controlling the ratio of Ce3+/Tb3+.

Manganese dioxides (MOs) are excellent microwave absorbing materials and have been used as substrates or catalysts for enhanced degradation of organic compounds. In this study, we extended our research on using birnessite (Birn), a type of MOs, for the degradation of tetracycline (TC) in aqueous solution under microwave induction (MI). The Birns were fabricated to achieve different ratios of Mn(II)/Mn(III)/Mn(IV) in the crystal structure. Their physical and chemical characteristics were determined by X-ray diffraction, field-emission environmental scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption fine structure spectra, and a microwave network analyzer. Their removal of TC under MI was evaluated under different physicochemical conditions. Lower solution pH, higher MI power, and higher Mn(II) and Mn(III) in the structure resulted in more TC removal. And the Birns are regenerable. LC–MS analyses confirmed the presence of degradation intermediates. The better performances of TC removal by Birns under MI was attributed to the high magnetic spin moment of Mn(II) and Mn(III) in the structure that has higher MI response.

Divalent mercury ion (Hg2+) is one of the most common pollutants in water with high toxicity and significant bioaccumulation, for which sensitive and selective detection methods are highly necessary to carry out its detection and quantification. Fluorescence detection by organic dyes is a simple and rapid method in pollutant analyses and is limited because of quenching caused by aggregation dye molecules. Hydrotalcite (LDH) is one of the most excellent carrier materials. In this study, an organic dye acridine orange (AO) was successfully loaded on the LDH layers, which significantly inhibited fluorescence quenching of AO. The composite AO/LDH reaches the highest fluorescence intensity when the AO initial concentration is 5 mg/L. With its enhanced fluorescent property, the composite powder was fabricated to fluorescence test papers. The maximal fluorescence intensity was achieved with a pulp to AO/LDH ratio of 1:5 which can be used to detect Hg2+ in water by naked eyes. Hg2+ in aqueous solution can be detected by instruments in the range of 0.5 to 150 mM. The novelty of this study lies on both the development of a new type of mineral-dye composite material, as well as its practical applications for fast detection.

The structural and luminescence properties of apatite-type compound Mn 2 Gd 8 (SiO 4 ) 6 O 2 have been investigated. The crystal structure of Mn 2 Gd 8 (SiO 4 ) 6 O 2 has been obtained from the X-ray diffraction data by Rietveld method in the hexagonal system, space group P6 3 / m , a = 9.3851 A, c = 6.7904 A, V = 517.97 A 3 , Z = 1. The Mn 2 Gd 8 (SiO 4 ) 6 O 2 phase contains two cationic sites, one site ( 4f site with point symmetry C 3 ) is a distorted tricapped trigonal prismatic polyhedron formed by nine oxygen atoms, and other site ( 6h sites with point symmetry C s ) is an irregular polyhedron of pentagonal bipyramidal geometry with the coordination by seven oxygen atoms. It is found that the Mn 2+ ions occupy only 4f sites with C 3 point symmetry, that has been verified by photoluminescence spectrum and decay curves. This work provides an insight to the novel inorganic compound design and gives an impetus to discover new functional materials and develop new applications.

A novel apatite structure phosphor Ca 9 La(PO 4 ) 5 (GeO 4 )F 2 :Dy 3+ (CLPGF:Dy 3+ ) with a hexagonal lattice in the P 6 3 / m space group was synthesized via a facile solid state technique. The crystal and fine local structure as well as their photoluminescence properties were investigated in detail. The CLPGF:Dy 3+ phosphor can absorb in the UV-vis spectral region of 290–475 nm and exhibit two intense emission bands centered at 485 and 580 nm, which ascribes to 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 transitions of Dy 3+ , respectively. The concentration quenching of Dy 3+ emission occurs via the energy transfer among the nearest-neighbor ions and the corresponding quenching mechanism was verified to be the dipole-dipole interaction. The quantum efficiencies of the phosphors were examined to be 72.9% and its luminescence intensity at 150 °C decreases to 93.8% and 98.6% of the initial value at room temperature, which corresponds to 4 F 9/2 to 6 H 15/2 transition and 4 F 9/2 to 6 H 13/2 transition of Dy 3+ ions, respectively. Their interesting photoluminescence properties indicate that the CLPGF:Dy 3+ phosphor is a promising white-emitting candidate for w -LEDs applications.

Herein, a facile surfactant-free hydrothermal method assisted with coprecipitation has been explored in order to prepare size-controlled HAP nanorods, and the growth mechanism of HAP nanostructures has also been proposed. In this article, the size of the HAP crystallites, ranging from 40 to 1500 nm, were controlled by varying the reaction conditions. Likewise, the experimental conditions can be changed to alter the shapes of the HAP nanostructures from nanorods to nanobelts. Additionally, interesting optically properties were induced in nano-HAP by doping with rare earth elements. The samples doped with terbium and europium generated green and red orange emissions, respectively, under irradiation by blue light, which is popularly used for wound healing and skin disease treatment. Thus, the doped HAP nanocrystals through the surfactant-free method have potential applications in blue phototherapy and photodynamic therapy.

A novel white light emitting phosphor KCaBi(PO 4 ) 2 :Dy 3+ for UV excitations has been synthesized by the solid state reaction technique. The powder X-ray diffraction patterns, Rietveld refinement and XPS were utilized to confirm the phase composite and crystal structure. The excitation and emission spectra, decay curves and chromaticity coordinates of the as-prepared phosphors were characterized to investigate the photoluminescence properties for application in white light-emitting diodes. The results revealed that the KCaBi(PO 4 ) 2 :Dy 3+ phosphors can be effectively assimilated with near ultraviolet, and exhibit two emission bands peaked at 480 nm(blue light) and 580 nm(yellow light) originating from the 4 F 9/2- 6 H 15/2 , 4 F 9/2 - 6 H 13/2 transitions of Dy 3+ , respectively. The critical distance was calculated to be about 17.96 A and the concentration quenching mechanism was verified as dipole-dipole interaction. Additional, the optimal chromaticity coordinates were determined to be (0.3118, 0.3309) and a better thermal stability of the phosphors have been illustrated.

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.

Although the electrochemical properties of porous LiMn2O4 microspheres are usually improved compared to those of irregular LiMn2O4 particles, the effects of the different synthesis conditions on the preparation of the porous LiMn2O4 microspheres are rarely discussed in detail. In the present work, porous LiMn2O4 microspheres were successfully synthesized by using molten LiOH and porous Mn2O3 spheres as a template. Multiple factors were considered in the preparation process, including reagent concentration, pH, adding mode, heating time, etc. The morphology of the MnCO3 template was crucial for the preparation of porous LiMn2O4 microspheres and it was mainly affected by the concentration of reactants and the pH value of the solution during the precipitation process. During the lithiation of Mn2O3 microspheres, the heating temperature and the ratio between Mn2O3 and lithium salt were the most significant variables in terms of control over the morphology and purity of the LiMn2O4 microspheres. Furthermore, we demonstrated that the porous LiMn2O4 microspheres presented better rate capability and cyclability compared to commercial LiMn2O4 powder as cathode materials for lithium-ion batteries (LIBs). This study not only highlights the shape-controllable synthesis of LiMn2O4 microspheres as promising cathode materials, but also provides some useful guidance for the synthesis of porous LiMn2O4 microspheres and other LIB' electrode materials.

Thin and lightweight flexible lithium-ion batteries (LIBs) with high volumetric capacities are crucial for the development of flexible electronic devices. In the present work, we reported a paper-like ultrathin and flexible Si/carbon nanotube (CNT) composite anode for LIBs, which was realized by conformal electrodeposition of a thin layer of silicon on CNTs at ambient temperature. This method was quite simple and easy to scale up with low cost as compared to other deposition techniques, such as sputtering or CVD. The flexible Si/CNT composite exhibited high volumetric capacities in terms of the total volume of active material and current collector, surpassing the most previously reported Si-based flexible electrodes at various rates. In addition, the poor initial coulombic efficiency of the Si/CNT composites can be effectively improved by prelithiation treatment and a commercial red LED can be easily lighted by a full pouch cell using a Si/CNT composite as a flexible anode under flat or bent states. Therefore, the ultrathin and flexible Si/CNT composite is highly attractive as an anode material for flexible LIBs.

In this paper, K3ScF6:Er3+,Yb3+ up-conversion luminescent materials with cryolite structure were synthesized via solid-state method. The X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL) under the excitation of a 980 nm laser with different power density were used to investigate the phase structure, elemental composition, and up-conversion luminescence properties of K3ScF6:Er3+,Yb3+. The quenching concentrations of Yb3+ and Er3+ were confirmed to 0.15 and 0.05 (mol concentration) in this system, respectively. Upon 980 nm excitation, the K3ScF6:Er3+,Yb3+ showed a typical transition of Er3+ which contains two main bands in the visible region that green and red. According to the fitting result of the pump power dependence of up-conversion intensity, all the green and red up-conversion emission of K3ScF6:0.05Er3+,0.15 Yb3+ belong to the two-photon process. To better understand the origin of radiation and energy transfer mechanism of the red and green up-conversion, the possible mechanism and electron transition process were also discussed.

The simple high-temperature solid-state route was adopted to synthesize a series of related Ba 3 LaK(PO 4 ) 3 F: x Eu 2+ (BLKPF: x Eu 2+ ) blue phosphors. The photoluminescence (PL) and diffuse reflection spectra have been investigated in detail. These phosphors which can be well excited by the 388 nm near ultraviolet light, produce the emitted blue light peaks located at about 460 nm. The critical Eu 2+ concentration quenching mechanism was ascribed to the dipole–dipole interaction, and the optimum concentration was eventually proved to be 0.1 mol. All above results indicate that Ba 3 LaK(PO 4 ) 3 F: x Eu 2+ phosphor can act as an appropriate candidate of the blue phosphor in the future.

Mn intercalated hydrotalcite was prepared using a reconstruction method. And Mn intercalation was confirmed by XRD, FTIR, and thermal analyses. The different valences of Mn were present as determined by XPS. Calcination slightly promoted the isomorphic replacement of Mn(2+) and Mn(3+) for Mg(2+) and Al(3+), especially the replacement of Mn(2+) for Mg(2+) and Al(3+), and to some extent, reduced Mn intercalation. Ultrasonic treatment significantly increased Mn intercalation in permanganate form (Mn(7+)), and promoted the replacement of Mn(2+) for Mg(2+) and Al(3+). XRF analysis showed that ultrasonic treatment decreased the unbalanced layer charge of Mn intercalated hydrotalcite, while prolonged calcination increased it. These results may provide guidance on the preparation and application of Mn intercalated hydrotalcite. Extended calcination time and ultrasonic vibration increased the interlayer spacing of hydrotalcite, as a result of reduction in layer charge. As the layer charge was not completely balanced after Mn intercalation, a certain amount of CO3(2-) was re-adsorbed into the interlayer space. Mn-hydrotalcites with different layer charges, different contents of Mn with varying valences are expected to have different performances in the process of adsorption, degradation, and catalysis.

Among inorganic phosphors used in solid-state lighting, the warm white light phosphors have drawn significant attention because of their high color rendering (CRI) and appropriate warm correlated color temperature (CCT). Herein, novel green emission KLa0.90Tb0.10Sr3(PO4)3F and red emission KLa0.90Eu(3+)0.10Sr3(PO4)3F phosphors were successfully synthesized for the first time. Besides, the phase constitution and photoluminescence properties were investigated in detail. The KLa0.90Tb0.10Sr3(PO4)3F phosphor shows a green emission with a maximum at 545 nm under excitation of 231 nm, while KLa0.90Eu(3+)0.10Sr3(PO4)3F displays a red emission centered at 617 nm excited at 393 nm. Temperature-dependent emission spectra reveal that these phosphors have better thermal stability and color stability. What is more, the white light emission phosphor can be generated by mixing three kinds of KLaSr3(PO4)3F:Re phosphors (Re=Eu2+, Tb3+, and Eu3+), exhibiting a CRI of ∼85 and a warm CCT of ∼3946 K. All the results indicated that the white light emission phosphor with high color rendering and appropriate warm correlated color temperature could be reached by combining these tri-color phosphors with proper ratio.

An appropriate solid-state route was adopted to synthesize a series of related Ba 3 Sc(PO 4 ) 3 : x Sm 3+ red-orange phosphors. The Rietveld method was used to explore the structure of the phosphor. At present the PL, PLE, diffuse reflection and decay curves have been investigated in detail. These phosphors can be accurately excited by the 406 nm n-UV light and produce the emitted red-orange light whose peaks locate at about 566 nm, 603 nm and 650 nm. The quantum efficiency of Ba 3 Sc 0.95 (PO 4 ) 3 :0.05Sm 3+ was 53.5%. All above results indicate that Ba 3 Sc(PO 4 ) 3 :Sm 3+ phosphor can act as a suitable candidate of the warm components of n -UV w-LEDs.

Nanocrystalline silicon thin films were successfully prepared via a magnesiothermic reduction process. The initial magnesium content was restricted by the thickness of the film deposited on a quartz glass substrate by magnetron sputtering. After the magnesiothermic reduction process, the Raman spectroscopy results revealed a strong correlation between the thickness of the nanocrystalline thin films and the initial magnesium content. The thickness of the nanocrystalline thin films first increased to a maximum and then decreased as the initial magnesium content was further increased. Based on the solid-state reaction between Mg and SiO2, the mechanism behind this phenomenon is explained. In addition, the Raman spectroscopy results showed that the average grain size was almost constant and the crystalline volume fraction was found to be proportional to the silicon content. The band gap of the nanocrystalline silicon thin film was estimated to be 2.94 eV.

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.

Although pitchstone (Ps) can be used to construct expanded and vitrified small balls (EVSBs) for building thermal insulation materials, the processing of the EVSBs requires substantial amounts of energy and produces many unusable tailings. The complete utilization of Ps resources in an energy-efficient manner is still challenging. In this study, a novel inorganic thermal insulation board was prepared by Ps powder through a chemical foaming method at room temperature and heat treatment method at 400 °C. The influence of sodium silicate solution on Ps powder mass ratio, surfactant content, foaming agent dosage, and that of low-temperature heat treatment process on the performance of the samples of the insulation material were systematically studied. Accordingly, the thermal conductivity (TC), density, and compressive strength (CS) of the samples could be engineered in the 0.114–0.270 g/cm3, 0.051–0.086 W/(m·K), and 0.12–1.46 MPa ranges, respectively, by modifying the abovementioned factors. Therefore, this work provides an energy-efficient way for the complete utilization of Ps resources.

In this paper, K3ScF6:Yb3+, Tm3+ phosphor with a cubic cryolite phase were prepared by means of high-temperature solid-state method. The crystal structure and up-conversion luminescence properties of Tm3+ and Yb3+ co-doped K3ScF6 were investigated in detail. Scanning electron microscope (SEM), energy disperse spectroscopy (EDS), elemental mapping and X-ray photoelectron spectroscopy (XPS) were used to analyze the elements composition, elemental distribution and valence states of samples. Under an excitation wavelength at 980 nm, all the samples displayed blue and red emission. When gradually increasing the concentration of Tm3+ in K3ScF6:0.2 Yb3+, Tm3+ and Yb3+ in K3ScF6: 0.01 Tm3+, Yb3+, the emission intensity of the samples appeared obviously concentration quenching effect, and the optimum concentration of Tm3+ and Yb3+ were confirmed to 0.01 and 0.20 mol%. Additionally, the effect of pump power on up-conversion emission intensity and the energy transfer mechanism between the Tm3+ and Yb3+ in these samples were analyzed in detail.

Design and preparation of nanostructured conducting polymers (CPs) is a very important research direction for high performance CPs-based supercapacitors (SCs). With hollow structure, high surface area, tunable surface properties and abundant resources, natural halloysite is a promising template agent for preparing new nanotubular-structure CPs. Here, nanotubular-structure polyaniline was successfully synthesized using natural tubular halloysite as hard template. The obtained tubular polyaniline presents high specific capacitance at various current density as electrode material for supercapacitors. After a facile carbon coating, the carbon coated tubular polyaniline shows high specific capacitance of 654 F g−1 at the current density of 1 A g−1 and excellent electrochemical stability with capacitance retentions ∼87% after 10000 cycles. This work may prove the feasibility of preparing high performance CPs-based nanostructure electrode materials for SCs application based on inexpensive natural clay minerals.

Hexavalent chromium species, Cr(VI), activates teratogenic processes, disturbs DNA synthesis and can give rise to mutagenous changes leading to malignant tumors. It is necessary to carry out its detection and quantification. Fluorescence detection by organic dye molecules is a simple and rapid method in pollutant analysis. Its application is limited because of concentration quenching caused by aggregation of fluorescent molecules. In this study, 7-amino-4-methylcoumarin (AMC) was successfully intercalated into the interlayer space of montmorillonite (MMT), which resulted in significant inhibition in fluorescence quenching. With its enhanced fluorescent property, the composite was fabricated into a film with chitosan to detect Cr(VI) in water. Cr(VI) in aqueous solution can be detected by instruments in the range of 0.005 to 100 mM with a detection limit of 5 μM.

Si3N4 was produced using diatomite and sucrose as silicon and carbon sources, respectively. The effect of the C/SiO2 molar ratio, heating temperature and soaking time on the morphology and phase compositions of the final products was investigated by scanning electron microscopy, x-ray diffraction analysis and energy dispersive spectroscopy. The phase equilibrium relationships of the system at different heating temperatures were also investigated based on the thermodynamic analysis. The results indicate that the phase compositions depended on the C/SiO2 molar ratio, heating temperature and soaking time. Fabrication of Si3N4 from the precursor via carbothermal reduction nitridation was achieved at 1550°C for 1–8 h using a C/SiO2 molar ratio of 3.0. The as-prepared Si3N4 contained a low amount of Fe3Si (

Up-conversion phosphors BaLa2ZnO5 co-doped with Ho3+/Yb3+ were synthesized by high temperature solid-state reaction method. The phase composition of the phosphors was characterized by X-ray diffraction (XRD). The structure of BaLa2ZnO5: 0.75% Ho/15% Yb phosphor was refined by the Rietveld method and results showed the decreased unit cell parameters and cell volume after doping Ho3+ and Yb3+, indicating Ho3+ and Yb3+ have successfully replaced La3+. Under the excitation of 980 nm diode laser, the strong green and weak red up-conversion emissions centered at 548 nm, 664 nm and 758 nm were observed, which originating from 5S2, 5F2→5I8, 5F4→5I8 and 5S2, 5F2→5I7 transitions of Ho3+ ions, respectively. The optimum doping concentrations of Ho3+ and Yb3+ were determined to be 0.75% and 15%, and the corresponding Commission International de L'Eclairage (CIE) coordinates are calculated to be x=0.298 and y=0.692. The related UC mechanism of Ho3+/Yb3+ co-doped BaLa2ZnO5 depending on pump power was studied in detail. The results indicate that BaLa2ZnO5: Ho3+/Yb3+ can be an effective candidate for up-conversion yellowish-green light emitter.

Raw montmorillonite (Mt) was cation-exchanged with Ca2 +, Mg2 +, and Fe3 +, and Pb2 + was tested for its adsorption on the exchanged Mt. The d-value and the cation exchange capacity (CEC) of Ca-exchanged montmorillonite (Ca2 + + Mt) were larger than those of Mg-exchanged montmorillonite (Mg2 + + Mt) and Fe-exchanged montmorillonite (Fe3 + + Mt). The Pb2 + adsorption on the homoionic Mt was fast and the amount of Pb2 + adsorption followed the order of Ca2 + + Mt > Mg2 + + Mt > Fe3 + + Mt. Simulation of Pb2 + adsorption on the Mt revealed a much larger energy drop when Pb2 + is substituting for Ca2 + in comparison to Pb2 + exchanging for Fe3 +.