Intense green light emission in Sr2 ZnGe2 O7 :Mn2+ phosphors by the design of high symmetry melilite structure.

A green phosphor Sr2 ZnGe2 O7 :Mn2+ with a melilite structure was prepared using a high-temperature solid-state reaction. When the 535 nm emission was monitored, the excitation spectrum of the Sr2 ZnGe2 O7 :Mn2+ was found to contain two excitation bands in the ultraviolet (UV) region. When excited by UV light, the sample shows bright green emission at 535 nm, which corresponds to the distinctive transition of Mn2+ (4 T1 →6 A1 ). Moreover, the quantum efficiency of Sr2 ZnGe2 O7 :Mn2+ could reach 67.6%. Finally, a high-performance white-light-emitting diode (WLED) with a low correlated colour temperature of 4632 K and a high colour rendering index (CRI) of 92.3 were packaged by coating commercial blue and red phosphors with an optimized Sr2 ZnGe2 O7 :Mn2+ sample on a 310 nm UV chip. This indicated that Sr2 ZnGe2 O7 :Mn2+ has the potential application as a green component in the WLED lighting field.

UCNP-Bi2 Se3 Upconverting Nanohybrid for Upconversion Luminescence and CT Imaging and Photothermal Therapy.

Non-invasive theranostics that integrate the advantages of multimodality imaging and therapeutics have great potential in the field of biomedicine. Herein, a new nanohybrid based on Bi2 Se3 -conjugated upconversion nanoparticles (UCNPs) has been successfully developed through a simple in situ growth strategy. Under 808 nm near-infrared laser irradiation, the UCNPs can emit bright visible light, whereas the Bi2 Se3 nanomaterial exhibits efficient photothermal conversion capacity. Moreover, the as-synthesized UCNP-Bi2 Se3 nanohybrid exhibits efficient cell upconversion luminescence (UCL), reasonable CT imaging, and admirable cancer cell ablation capacity, further emphasizing the efficiency of this strategy for simultaneous UCL imaging and photothermal therapy. The designed theranostic strategy guided by dual-modal imaging endowed with real-time dynamic monitoring, remote controllability, and non-invasiveness makes the UCNP-Bi2 Se3 nanohybrid an ideal candidate for non-invasive multimodal imaging-guided photothermal therapy for the precise diagnosis and treatment of cancer.

ZnGa2-yAlyO4:Mn2+,Mn4+ Thermochromic Phosphors: Valence State Control and Optical Temperature Sensing.

Dual-emitting and thermochromic manganese ion single doped ZnGa2-yAlyO4 phosphors were prepared by solid-state reaction. The regulation of the valence state and the luminescent properties, especially the luminescent thermal stability of manganese ions in ZnGa2-yAlyO4, are discussed in detail. When excited by ultraviolet (UV) light, the emission spectra of ZnGa2O4:Mn2+,Mn4+ present an ultranarrow green emission band at 503 nm with a fwhm of 22 nm, which derives from the Mn2+ ions formed by the self-reduction of doped Mn4+, and a red emission band of the Mn4+ ions at 669 nm. In addition, a ZnGa2-yAlyO4:Mn2+,Mn4+ solid solution was designed and synthesized by Al3+ replacing Ga3+. The doping of Al3+ effectively inhibited the degree of Mn4+ self-reduction to Mn2+, thus realizing the regulation of valence state of manganese ions. Interestingly, the thermal stability of luminescence shows that the response of Mn2+ and Mn4+ to temperature is obviously different in ZnGa2-yAlyO4, implying the potential of the prepared phosphors as optical thermometers. Subsequently, three kinds of optical thermometers with superior color discrimination and high relative sensitivity (Sr) based on the fluorescence intensity ratio (FIR) technique were realized in 100-475 K. The Sr value of ZGO:0.005Mn/ZGA0.5O:0.005Mn/ZGAO:0.005Mn phosphors can be as high as 4.345%/4.001%/3.488% K-1 (at 350/325/400 K), reflecting the great potential of ZnGa2O4:Mn2+,Mn4+ for optical thermometry applications.

Novel tunable green-red-emitting oxynitride phosphors co-activated with Ce3+, Tb3+, and Eu3+: photoluminescence and energy transfer.

A series of novel Ce3+, Tb3+ and Eu3+ ion doped Y4SiAlO8N-based oxynitride phosphors were synthesized by the solid-state method and characterized by X-ray powder diffraction, scanning electron microscopy, photoluminescence, lifetimes and thermo-luminescence. The excitation of the Ce3+/Tb3+ co-doped and Ce3+/Tb3+/Eu3+ tri-doped phosphor with near-UV radiation results in strong linear Tb3+ green and Eu3+ red emission. The occurrence of Ce3+-Tb3+ and Ce3+-Tb3+-Eu3+ energy transfer processes is responsible for the bright green or red luminescence. The Tb3+ ion acting as an energy transfer bridge can alleviate MMCT quenching between the Ce3+-Eu3+ ion pairs. The lifetime measurements demonstrated that the energy-transfer mechanisms of Ce3+→ Tb3+ and Tb3+→ Eu3+ are dipole-quadrupole and quadrupole-quadrupole interactions, respectively. The temperature dependent luminescence measurements showed that as-prepared green/red phosphors have good thermal stability against temperature quenching. The obtained results indicate that these phosphors might serve as promising candidates for n-UV LEDs.

Development of a novel Eu2+ activated oxonitridosilicate cyan phosphor for enhancing the color quality of a violet-chip-based white LED.

Cyan phosphors are urgently needed to fill the cyan gap and improve the spectral continuity of white light-emitting diodes (LEDs) to cater to the high demand for high-quality lighting. Here, a series of new Eu2+-activated La3Si6.5Al1.5N9.5O5.5 (LSANO) cyan phosphors were prepared, and their luminescence properties and color centers were analyzed through fluorescence spectral measurements from 7 K to 475 K. At 300 K, the photoluminescence excitation (PLE) spectrum monitored at 483 nm presents a broadband of 200-460 nm with a peak at 398 nm, matching well with commercial violet LED chips. When excited by 398 nm violet light, the photoluminescence emission (PL) spectrum of LSANO:0.01Eu2+ exhibits a cyan emission band at about 483 nm. At 7 K, the emission spectrum clearly shows an asymmetric emission band and the emission peak wavelength changes from 483 nm (300 K) to 500 nm (7 K), indicating that there are two possible color centers in the LSANO:Eu2+ phosphor. Moreover, the maximum emission value can be adjusted from 480 to 499 nm by adjusting the doping content of Eu2+. Finally, a violet-chip-based white LED with the optimized color quality of Ra = 91.4, Rf = 90.1, and Rg = 93.6 was fabricated by adding the prepared cyan phosphor, verifying the potential application of the prepared cyan phosphor LSANO:Eu2+ in high-quality white LEDs.

Cs2MnCl4:Eu2+: A Near-Violet Light-Triggered Single-Component White Light Emitter.

Single-component white-light luminescent materials are considered an economical and facile choice for phosphor-converted white light-emitting diodes (pc-WLEDs). Here, a new single-component white-light-emitting material Cs2MnCl4:Eu2+ based on the combination of a lead-free halide structure and a rare-earth ion is first reported. Benefiting from the smart dilution-sensitization design strategy, white light composed of dual broad emission originating from Eu2+ (blue light, 444 nm, 4f65d1 → 4f7) and Mn2+ (yellow light, 566 nm, 4T1g → 6A1g) was successfully realized under near-ultraviolet light (404 nm) radiation with a high photoluminescence quantum yield of 66%. Based on the single-source Cs2MnCl4:Eu2+ phosphor, a pc-WLEDs device with "eye-friendly" white light production was successfully fabricated. The pc-WLEDs exhibit suitable color coordinates of (0.3294, 0.2746) and a high color rendering index of 82.3, demonstrating the potential in the future health-conscious illumination application by reducing the risk of eye strain and high-energy blue-light damage. This work achieves a new single-component white-light-emitting Mn-based halide phosphor and provides a new path for the design of single-component white light sources in Mn-based halides.

Site occupancy preference of Bi3+ and Bi3+-Eu3+ codoped yttrium galliate phosphors for white LEDs.

A variety of Bi3+-activated and Bi3+-Eu3+ codoped Y3GaO6 phosphor samples were obtained by solid-state reaction. The phase purity and crystal structure of the specimens were characterized via powder X-ray diffraction (XRD) analysis and Rietveld refinement. For the single Bi3+-doped Y3GaO6 phosphor, two different PL peaks at 410 and 595 nm were obtained, resulting from the two different Bi3+ sites occupied. The site occupation is driven by Bi3+ ion concentration. There is an energy transfer from the Bi3+ to Eu3+ ions in the YGO:Bi3+,Eu3+ phosphors. Besides, the energy transfer mechanism, efficiencies, quantum efficiency and thermal stability have been discussed in detail, demonstrating that the sample possesses high quantum efficiency and good thermal stability. The high color-rendering index Ra (92.9, and 81.6) and low CCT (3286 K, and 3904 K) of the white light-emitting diodes (WLEDs) clearly indicate that these samples are promising candidates for WLEDs.

Highly thermally stable Cr3+ and Yb3+ codoped Gd2GaSbO7 phosphors for broadband near-infrared applications.

Gd2GaSbO7:Cr3+,Yb3+ phosphors with efficient broadband NIR emission were prepared by a solid-state reaction. Under the excitation of 448 nm, the Gd2GaSbO7:Cr3+ (GGS:Cr3+) phosphor exhibits a broadband NIR emission band centered at approximately 770 nm with a full width at half maximum (FWHM) of 160 nm. In addition, Yb3+ codoping can distinctly improve the photoluminescence properties of the GGS:Cr3+ phosphor, leading to broadening of the FWHM and greatly enhancing the thermal stability of the phosphor. Moreover, the energy conversion process of Cr3+ → Yb3+ ions was analyzed in detail, demonstrating that the energy transfer mechanism conformed to electric dipole-dipole interaction. The NIR pc-LEDs assembled with the GGS:Cr3+ phosphor and blue LED chips possessed a maximum NIR output power of ∼21 mW at 100 mA driving current, indicating promising applications of the synthesized phosphor in NIR pc-LEDs.

Novel SrGd2Al2O7:Mn4+, Nd3+, and Yb3+ phosphors for c-Si solar cells.

Novel single-doped and codoped SrGd2Al2O7-based (SGA) phosphors with tunable emission were synthesized via the solid-state reaction approach. The optimal SGA:0.0008Mn4+ phosphor presents an emission band peaking at 709 nm and shows great red luminescence properties. With the incorporation of Nd3+/Yb3+ into SGA:0.0008Mn4+, an efficient energy transfer Mn4+→ Nd3+/Yb3+ was observed. When Nd3+ and Yb3+ were codoped into SGA:0.0008Mn4+, an energy transfer mechanism from Mn4+ to Nd3+ to Yb3+ was found on the basis of the energy transfer mediation of Nd3+ connecting the Mn4+ and Yb3+ luminescent centers. It results in a strong near-infrared emission in the spectral region of high response of c-Si solar cells, which suggests a potential approach to improve the energy conversion efficiency of c-Si solar cells. The findings offer a novel route to design new down-conversion luminescent materials for the c-Si solar cells.

A Novel Red-Emitting Na2NbOF5:Mn4+ Phosphor with Ultrahigh Color Purity for Warm White Lighting and Wide-Gamut Backlight Displays.

In this work, a novel red-emitting oxyfluoride phosphor Na2NbOF5:Mn4+ with an ultra-intense zero-phonon line (ZPL) was successfully synthesized by hydrothermal method. The phase composition and luminescent properties of Na2NbOF5:Mn4+ were studied in detail. The photoluminescence excitation spectrum contains two intense excitation bands centered at 369 and 470 nm, which match well with commercial UV and blue light-emitting diode (LED) chips. When excited by 470 nm blue light, Na2NbOF5:Mn4+ exhibits red light emission dominated by ZPL. Notably, the color purity of the Na2NbOF5:Mn4+ red phosphor can reach 99.9%. Meanwhile, the Na2NbOF5:Mn4+ phosphor has a shorter fluorescence decay time than commercial K2SiF6:Mn4+, which is conducive to fast switching of images in display applications. Profiting from the intense ZPL, white light-emitting diode (WLED) with high color rendering index of Ra = 86.2 and low correlated color temperature of Tc = 3133 K is realized using yellow YAG:Ce3+ and red Na2NbOF5:Mn4+ phosphor. The WLED fabricated using CsPbBr3 quantum dots (QDs) and red Na2NbOF5:Mn4+ phosphor shows a wide color gamut of 127.56% NTSC (National Television Standard Committee). The results show that red-emitting Na2NbOF5:Mn4+ phosphor has potential application prospects in WLED lighting and display backlight.

Near-infrared emission of CaAl6Ga6O19:Cr3+,Ln3+ (Ln = Yb, Nd, and Er) via energy transfer for c-Si solar cells.

A series of CaAl6Ga6O19:Cr3+,Ln3+ (Ln = Yb, Nd, and Er) novel near-infrared (NIR) emitting phosphors were prepared via a high-temperature solid-state reaction. The luminescence spectra and decay lifetimes of these samples were measured to prove the energy transfer process from the Cr3+ to Ln3+ ions. The CaAl6Ga6O19:Cr3+,Ln3+ (Ln = Yb, Nd, and Er) phosphors can efficiently convert the short-wavelength sunlight in the near-ultraviolet and visible (UV-Vis) regions into near-infrared emission, which matches the higher sensitivity region of the c-Si solar cells. The maximal energy transfer efficiencies of CaAl6Ga6O19:Cr3+,Ln3+ (Ln = Yb, Nd, and Er) were 25.84%, 73.90%, and 29.46%, respectively. Our results show that the CaAl6Ga6O19:Cr3+,Ln3+ (Ln = Yb, Nd, and Er) phosphors have potential applications as luminescent downshifting convertors for enhancing the photoelectric conversion efficiency of the c-Si solar cells.

Enhancing Luminescence and Controlling the Mn Valence State of Gd3Ga5-x-δAlx-y+δO12:yMn Phosphors by the Design of the Garnet Structure.

Gd3Ga5-x-δAlx-y+δO12:yMn solid solutions with improving luminescence properties were prepared via cation substitution and a controllable Mn valence state. The abnormal autoreduction from Mn4+ to Mn2+ ions was observed during the formation of Gd3Ga5-x-δAlx-y+δO12:yMn. The doped manganese ions occupy octahedral Ga3+(1) and Al3+(1) sites to form the Mn2+ luminescent center with red emission at 630 nm and Mn4+ luminescent centers with deep red light emission at 698 nm, respectively, matching well with the red light absorption of phytochrome (PR) and the far-red light absorption of phytochrome (PFR). With the design of the concentration of Al3+ and doped manganese ions, the photoluminescence (PL) of Mn4+/Mn2+ (corresponding to PFR/PR) can be tuned, which is very useful for controlling the plant growth. Moreover, the PL intensity of Gd3Ga5-x-δAlx-y+δO12:yMn can be increased by 6.8 times by substituting Al3+ for Ga3+. The thermal stability is also enhanced significantly. Finally, a series of warm white-light-emitting diodes (WLEDs) with good performance were fabricated using the as-prepared Gd3Ga5-x-δAlx-0.012+δO12:0.012Mn phosphor. The results show that the designed Gd3Ga5-x-δAlx-y+δO12:yMn phosphors have potential practical values in plant-growth light-emitting diodes (LEDs) and high-performance WLEDs. Moreover, our strategy not only provides a unique inspiration for tuning the valence states of Mn but also designs new advanced luminescent materials.

Enhanced red luminescence in CaAl12O19:Mn4+via doping Ga3+ for plant growth lighting.

A series of solid solution CaAl12-xGaxO19:Mn4+ phosphors were prepared via a high-temperature solid-state reaction. Their structural properties were characterized by X-ray diffraction (XRD) and the luminescence was investigated via photoluminescence spectra. The obtained CaAl12-xGaxO19:Mn4+ phosphor has a strong broad excitation band in the range of 250-550 nm, which can be easily excited by the UV, NUV and blue light, and a broad emission band centered at 655 nm between 600 nm and 800 nm due to the 2Eg → 4A2g transition of the Mn4+ ion. The PL spectra indicate that the intensity of CaAl12O19:Mn4+ can be enhanced when the Ga3+ concentration equals 1. Furthermore, the element mapping, optical properties, thermal stability, fluorescence lifetime and CIE chromaticity reveal that the CaAl12-xGaxO19:Mn4+ phosphors can be considered as potential candidates in indoor plant cultivation.

The structures and luminescence properties of Sr4Gd3Na3(PO4)6F2:Ce3+,Tb3+ green phosphors with zero-thermal quenching of Tb3+ for WLEDs.

In this paper, novel green-emitting Sr4Gd3Na3(PO4)6F2:Ce3+,Tb3+ phosphors with zero-thermal quenching of Tb3+ have been prepared and investigated. X-ray diffraction together with Rietveld structure refinement was employed to give an insight into the structures of the samples. The luminescence spectra at 300 K and 80 K confirmed that the Ce3+ ions in Sr4Gd3Na3(PO4)6F2:Ce3+ were distributed randomly on the cation sites and gave intense emission. Utilizing the Ce3+ → Tb3+ energy transfer, intense green emitting Sr4Gd3Na3(PO4)6F2:Ce3+,Tb3+ had been obtained. The energy migration mechanism of Ce3+ in Sr4Gd3Na3(PO4)6F2:Ce3+ and the energy transfer mechanism of Ce3+ → Tb3+ in Sr4Gd3Na3(PO4)6F2:Ce3+,Tb3+ were determined by the analysis of photoluminescence spectra and decay curves. Sr4Gd3Na3(PO4)6F2:Ce3+,Tb3+ exhibited a thermal-induced enhancement of Tb3+ emission at 25-300 °C, indicating an excellent thermal stability. Moreover, utilizing our prepared Sr4Gd3Na3(PO4)6F2:0.06Ce3+,0.15Tb3+ phosphor, green and white emitting LED devices have been fabricated. Our investigation indicated the potential application of prepared green phosphors in UV WLEDs and a feasible method to explore highly thermally stable phosphors utilizing the high thermal stability of donors together with energy transfer from donors to acceptors.

One-pot synthesis of Ln3+-doped porous BiF3@PAA nanospheres for temperature sensing and pH-responsive drug delivery guided by CT imaging.

The design and synthesis of responsive inorganic nanocapsules have attracted intensive research interest in cancer treatment. The combination of non-invasive diagnosis and chemotherapy into a single theranostic nanoplatform is prospective in the biomedical field. In this work, a polyacrylic acid (PAA)-functionalized porous BiF3:Yb,Er nanocarrier was constructed via a straightforward one-pot solvothermal strategy. Compared with the undoped BiF3 sub-microspheres, the lanthanide ion (Ln3+) doping endowed the BiF3 material with a smaller size and increased BET specific surface area and pore volume, which make it suitable as a drug carrier. It was found that the synthesized nanomaterial could effectively relieve the side effects of doxorubicin (DOX) and exhibited pH-dependent DOX loading and release. Its satisfactory biocompatibility and efficient tumor inhibition were emphasized by a series of in vitro/in vivo experiments. In addition, the synthesized nanomaterial exhibited favorable CT contrast efficacy due to the excellent X-ray attenuation coefficient of Bi. Moreover, characteristic upconversion luminescence and temperature sensing in a wide temperature range were realized over the synthesized BiF3:Yb,Er sample. Therefore, carboxyl-functionalized BiF3:Yb,Er can be expected to be an ideal candidate in the fabrication of temperature sensing and multifunctional theranostic nanoplatforms.

Novel NIR LaGaO3:Cr3+,Ln3+ (Ln = Yb, Nd, Er) phosphors via energy transfer for C-Si-based solar cells.

A series of Cr3+-Yb3+/Nd3+/Er3+ codoped LaGaO3 phosphors were synthesized by a traditional solid-state method. The morphology, crystal structure, phase purity, and the luminescence properties of samples were characterized by using X-ray diffraction, Rietveld refinement, field-emission scanning electron microscopy, and photoluminescence. The obtained phosphors exhibit efficient broad absorption in the near ultraviolet and visible (UV-Vis) region and intense near infrared (NIR) emission, due to the energy transfer process from the Cr3+ to Yb3+/Nd3+/Er3+ ions, which match well with the maximum photon flux region of the solar spectrum and the optimal spectral response of the C-Si solar cell. Moreover, we also observed an energy transfer from the Nd3+/Er3+ to Yb3+ ions. The efficiency was investigated and analyzed by the visible and NIR emission spectra and lifetime decay curve and the energy transfer efficiency was as high as 77%. Our results reveal that the Cr3+-Yb3+/Nd3+/Er3+ codoped phosphors are promising materials for enhancing the efficiency of solar cells.

Preparation and photoluminescence of novel La8Ca2(Si4P2O22N2)O2 oxynitride phosphors containing Eu2+/Ce3+/Tb3+ ions.

A series of novel Eu2+/Ce3+/Tb3+ ion doped La8Ca2(Si4P2O22N2)O2-based apatite structure oxynitride phosphors have been synthesized by a solid-state method. The phase purity has been checked by X-ray diffraction (XRD) and the Rietveld method. The photoluminescence excitation (PLE) spectra indicate that the obtained phosphors have broad excitation bands in the n-UV range, which is a favourable property for application as n-UV-WLED phosphors. The concentration quenching has been investigated in detail. The temperature-dependent luminescence and efficiency study shows that the as-prepared phosphors have a good thermal stability and high quantum efficiency. Moreover, a warm white LED device with a low color temperature of 4288 K and a high color rendering index (Ra) of 80.8 has been obtained by coating a La8Ca1.99(Si4P2O22N2)O2:0.01Eu2+ phosphor with a (Sr,Ca)AlSiN3:Eu2+ red phosphor on a n-UV chip. Our results reveal that the La8Ca2(Si4P2O22N2)O2:Eu2+ phosphor is a promising bluish-green phosphor for WLEDs.

Designing of UCNPs@Bi@SiO2 Hybrid Theranostic Nanoplatforms for Simultaneous Multimodal Imaging and Photothermal Therapy.

Herein, a novel multifunctional nanoplatform was designed toward multimodality imaging and photothermal therapy (PTT). It was found that Bi nanoparticles could grow in situ on the surface of NaYF4:20%Yb,2%Er@NaYF4:40%Yb@NaGdF4 core-shell nanoparticles (labeled as UCNPs). In this structure, UCNPs were mainly employed as an upconversion luminescence (UCL) imaging agent, whereas the Bi nanoparticles worked as an effective CT imaging and photothermal agent. Importantly, a dense SiO2 shell was employed to protect the Bi nanoparticles from oxidation, and it also endowed the nanoplatform with excellent hydrophilic ability. The effective UCL/CT imaging and PTT performances were emphasized by a series of in vivo experiments, which suggest that the integrated nanoplatform with imaging and therapy functions shows great promise in the biomedical field.

Four new compounds from the leaves of Acer truncatum.

Four new compounds, 3-(4-hydroxy-3,5-dimethoxyphenyl)propyl formate (1), 2,6-dimethoxy-4-[(1S)-3-methoxypropyl]phenol (2), (1R,2R)-4-[(3R)-3-hydroxybutyl]-3,3,5-trimethylcyclohex-4-ene-1,2-diol (3), and (1S,3R,3aR,6S,7S,9aR)-decahydro-1-(hydroxymethyl)-1,7-dimethyl-3a,7-methano-3aH-cyclopentacyclooctene (4) were isolated from the leaves of Acer truncatum, together with twelve known compounds. Their structures were elucidated on the basis of extensive spectroscopic techniques. The absolute configuration of compound 3 was established by the modified Mosher's method. All compounds were evaluated for antibacterial activities.

A new neolignan glycoside from the leaves of Acer truncatum.

A new neolignan glycoside, (7R,8R)-7,8-dihydro-9'-hydroxyl-3'-methoxyl- 8-hydroxymethyl-7-(4-hydroxy-3-methoxyphenyl)-1'-benzofuranpropanol 9'-O-beta-D- glucopyranoside (1) was isolated from the leaves of Acer truncatum along with (7R,8R)-7,8-dihydro-9'-hydroxyl-3'-methoxyl-8-hydroxymethyl-7-(4-O-alpha-L-rhamno- pyranosyloxy-3-methoxyphenyl)-1'-benzofuranpropanol (2), schizandriside (3), lyoniresinol (4), berchemol (5), (-)-pinoresinol-4-O-beta-D-glucopyranoside (6), hecogenin (7), chlorogenic acid (8) and neochlorogenic acid (9). Their structures were elucidated on the basis of extensive spectroscopic data. The absolute configuration of compounds 1 was established by its CD spectrum. The antibacterial activities of compounds 1-7 were evaluated.