Significant effects of mixed cations on the morphology and photochemical activities of alkali-metal-antimony (Na,K)Sb3O7.

Oxide semiconductors with mixed-valence states generally exhibit excellent optoelectronic and photochemical properties due to facile charge transfer in redox reactions. In this work, we investigate the effects of mixed alkali on the optical absorption, luminescence spectra and photocatalytic abilities of (Na1-xKx)Sb3O7 nanoparticles. All the samples are fabricated using a simple one-step hydrothermal method. The structural studies show that the largest substitution of K+ ions in (Na1-xKx)Sb3O7 is at x = 0.3. In hydrothermal synthesis, the mixed arrangement of K+ and Na+ in (Na1-xKx)Sb3O7 has an influence on the crystal shape of particles. NaSb3O7 develops into a regular cube shape. With the increase of K+ ions in (Na1-xKx)Sb3O7, the edges and corners of the cube are further ground off, resulting in irregularly spherical particles. This mixed-alkali antimonite belongs to a p-type indirect allowed transition semiconductor, and the optical band gap is 2.71 eV (x = 0.3). The intrinsic luminescence of NaSb3O7 is detected at 540 nm, which is nearly quenched in Na0.7K0.3Sb3O7. It is demonstrated that the substitution of K+ in NaSb3O7 significantly increases the photodegradation of RhB solutions. There are two types of Sb cations, i.e., Sb5+ and Sb3+ mixed in the structure. The improved photocatalysis is attributed to the charge mediators between Sb5+/Sb3+ couples. The experiment shows that co-doping cations in antimonite oxides may be one of the strategies to improve photochemical properties.

Intrinsic- and Rare Earth Ion-Activated Luminescence in NbAlO4 with Wide Structure Channels.

Compounds with ordered and interconnected channels have versatile multifunctional applications in technological fields. In this work, we report the intrinsic- and Eu3+-activated luminescence in NbAlO4 with a wide channel structure. NbAlO4 is an n-type semiconductor with an indirect allowed transition and a band-gap energy of 3.26 eV. The conduction band and valence band are composed of Nb 3d and O 2p states, respectively. Unlike the common niobate oxide Nb2O5, NbAlO4 exhibits efficient self-activated luminescence with good thermal stability even at room temperature. The AlO4 tetrahedron effectively blocks the transfer/dispersion of excitation energy between NbO6 chains in NbAlO4, allowing for effective self-activated luminescence from NbO6 activation centers. Moreover, Eu3+-doped NbAlO4 displayed a bright red luminescence of 5D0 → 7F2 transition at 610 nm. The site-selective excitation and luminescence of Eu3+ ions in a spectroscopic probe were utilized to investigate the doping mechanism. It is evidenced that Eu3+ is doped in the structure channel in NbAlO4 lattices, not in the normal cation sites of Nb5+ or Al3+. The experimental findings are valuable in developing new luminescent materials and improving the understanding of the material's channel structure.

Immobile crystallization of radioactive iodide by redox transformation of a low crystalline copper phase.

Here we show an innovative way to effectively scavenge highly mobile radioiodide and to dramatically reduce its waste volume through a spontaneous phase transformation. Under an anaerobic condition, as metallic copper (II) was favorably associated with bicarbonate (HCO3-) in solution, a cupriferous carbonate compound (malachite) quickly formed, which was redox-sensitive and transformable to a compact crystal of CuI (marshite). The formation of CuI crystal was principally led by the spontaneous Cu-I redox reaction centering around the copper phase over the presence of sulfate (SO42-). The completely transformed CuI crystal was poorly soluble in water and grew to large microcrystals (∼µm) via a remarkable selectivity for I-. Interestingly, this redox-induced iodide crystallization was rather promoted over the existence of anionic competitors (e.g., HCO3- and SO42-), which usually exist in wastewater and natural water. Unlike the conventional methods, these competing anions positively behaved in our system by supporting that the initial malachite was more apt to be reactive to largely attract highly mobile I-. Under practical environments with various anions, such a selective I- uptake and fixation within a compact crystalline space will be a promising way to effectively remove I- in a great capacity.

Phase-formations of Mg2P2O7-Mn2P2O7 mixed pyrophosphates and their desired luminescence abilities.

In this work, a series of mixed pyrophosphates (Mg1-xMnx)2P2O7 (x = 0-1.0) were prepared for the first time using a solid-state reaction method, which exhibits two kinds of structural variants, that is, α-(low temperature) and ß-(high temperature) phases. The detailed phase-formations were determined via structural Rietveld refinements and the luminescence transitions of 4T1 → 6A1 in Mn2+. The phase-formation of (Mg1-xMnx)2P2O7 (x = 0-1.0) shows a strict dependence on Mn2+ doping contents in the lattices. (Mg1-xMnx)2P2O7 has an α-Mg2P2O7 phase when the Mn2+-doping concentration is lower than x ≤ 0.1. With an increase of Mn2+ substitution above 20 mol% (x = 0.2-1.0), (Mg1-xMnx)2P2O7 presents only the ß-phase even at room temperature, while (Mg1-xMnx)2P2O7 (x = 0.15) shows a mixed formation of α- and ß-Mg2P2O7 phases. The crystallographic surrounding of the Mn2+ activators in different structures had a strict influence on the spectral profile, luminescence efficiency, and color centers. Interestingly, in this series of phosphors, (Mg1-xMnx)2P2O7 (x = 0.15) with the mixed phases of α- and ß-type has overwhelming luminescence abilities such as the best luminescence intensity and high thermal stability. The pyrophosphates were confirmed to qualify for red-emitting LED lamps.

Photoenergy Conversion Behaviors of Photoluminescence and Photocatalysis in Silver-Coated LiBaPO4:Eu2.

LiBaPO4:Eu2+ phosphor and Ag-coated LiBaPO4:Eu2+ composites (Ag/LiBaPO4:Eu2+) were prepared via solid-state reaction and traditional photoreduction methods, respectively. The samples were characterized via XRD, SEM, and UV-vis optical absorption spectroscopy. Two photoenergy conversion processes, namely, photocatalysis and photoluminescence, were investigated in detail. In comparison with as-prepared LiBaPO4:Eu2+ phosphor, Ag-modified composites exhibited the enhanced photocatalytic effects together with the quenched Eu2+ luminescence. A Schottky barrier was created on the interface between Ag nanoparticles and LiBaPO4 host, thereby greatly delaying the recombination between the light-induced holes and electrons. A photoenergy conversion mechanism was suggested and discussed on the basis of the experiments. The Eu2+ ion luminescence centers directly participated in the photodegradation with the meditation of Ag nanoparticles on the surface. With the increase of the Ag coating level on the surfaces, some emission peaks corresponding to 5D0 → 7F0,1,2,3,4 transitions of Eu3+ ions were detected. Eu2+/Eu3+ couples also play an important role in improving photocatalysis. LiBaPO4:Eu2+ phosphor is a good candidate for the investigation of multimodal photoenergies of photoluminescence and photocatalysis.

Anti-Stokes Ultraviolet Luminescence and Exciton Detrapping in the Two-Dimensional Perovskite (C6H5C2H4NH3)2PbCl4.

Recently, it has been found that low-dimensional organometallic halide perovskites can be adopted as nonlinear monolayer emitters because of their efficient spontaneous anti-Stokes visual luminescence under visual or near-infrared laser excitation. Herein, we demonstrate a luminescence up-conversion process from the visible self-trapped exciton (STE) to an ultraviolet (UV) free exciton (FE) in the two-dimensional perovskite (C6H5C2H4NH3)2PbCl4 quantum wells excited by nanosecond pulse laser excitation. An ultraviolet 347 nm near-band-edge FE emission is obtained under the excitation of 579 nm dye laser at 10 K by a two-step, two-photon absorption process from the real intermediate exciton state. In addition, the decay rise time of higher-laying states of STE indicates the excitonic detrapping procedure could occur by the annihilation of phonons. Our results suggest that the low-dimensional halide perovskites with deformable structure are able to be applied in visible light-pumped UV-emitting devices.

Modified optical properties via induced cation disorder in self-activated NaMg2V3O10.

Cation disorder in the phosphor lattice could be one of the effective approaches to modify the luminescence efficiency. In this work, cation substitutions of (Mo6+→ V5+) and (Na+→ Mg2+) were conducted in the self-activated NaMg2V3O10. All the samples of Na1+xMg2-xV3-xMoxO10 (x = 0, 0.01, 0.05, 0.1, 0.2, 0.3) were prepared via solid-state reaction. The morphological properties were measured via SEM and EDS analyses. Structural Rietveld refinement was performed to investigate the microstructure in the lattices. The cation substitution brings about structural disorder in the phosphor, which exerts great modifications in the luminescence properties. NaMg2V3O10 presents an intrinsic indirect transition with a band gap of 3.22 eV. The incorporation of Mo6+ and Na+ in the lattices moves the optical absorption to a longer wavelength bringing about a narrower band gap. The luminescence intensity, thermal stability and corresponding lifetime were modified by the cation disorder in the self-activated phosphor.

Optical Thermometry Based on Vibration Sidebands in Y2MgTiO6:Mn4+ Double Perovskite.

Mn4+-doped Y2MgTiO6 phosphors are synthesized by the traditional solid-state method. Powder X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectrometer are employed to characterize the samples. The Mn4+-doped Y2MgTiO6 phosphors show the far-red emission at ∼715 nm, which is assigned to the 2Eg → 4A2 spin-forbidden transition of Mn4+. The temperature-dependent luminescent dynamics of Mn4+ is described by a complete model associated with electron-lattice interaction and spin-orbit coupling. The noncontact optical thermometry of Y2MgTiO6:Mn4+ is discussed based on the fluorescence intensity ratio of thermally coupled anti-Stokes and Stokes sidebands of the efficient ∼715 nm far-red emission in the temperature range of 10-513 K. The maximum sensor sensitivity of Y2MgTiO6:Mn4+ is determined to be as high as 0.001 42 K-1 at 153 K, which demonstrates potential applications for the optical thermometry at low-temperature environments.

Excitation power dependent optical temperature behaviors in Mn4+ doped oxyfluoride Na2WO2F4.

A Mn4+ doped Na2WO2F4 phosphor was synthesized through a two-step wet chemical method. The relationship between crystal structure and luminescence properties is discussed and unusual strong intense zero phonon lines (ZPLs) have been found in a distorted octahedral environment. The power dependent luminescence spectra exhibit the existence of down conversion luminescence intensity saturation under a high pumping power limit. The fluorescence intensity ratios of anti-Stokes bands to the ZPL and Stokes bands reveal an obvious temperature dependent relationship based on thermal de-population from the low states to the upper states of an intrinsic Mn4+ 2Eg → 4A2g transition. The temperature dependent emission intensity of Mn4+ is investigated by changing the excitation power, and an optical temperature sensitivity as high as 0.00658 K-1 is achieved at 193 K with the intensity ratio of anti-Stokes bands to the ZPL under 488 nm excitation by a Xenon lamp. This work presents a new method to realize optical thermometry at low temperature by controlling the intensity ratio of the anti-Stokes bands to the ZPL.

A new silver metaniobate semiconductor of Ag0.5La0.5Nb2O6 with defect-perovskite structure.

Silver-containing lanthanum metaniobate Ag0.5La0.5Nb2O6 nanoparticles were synthesized by sol-gel polymerized complex method. A typical defect-perovskite structure was confirmed by XRD Rietveld refinements. The surface characteristics of the sample were tested by SEM, TEM and EDS measurements. SEM and TEM show that the sample presents ball-like particles with the diameters of 100nm to 400nm. The sample shows both self-activated luminescence and photocatalytic activities. Ag0.5La0.5Nb2O6 has a direct transition with band energy of 2.85eV. The Ag4d-O2p hybridization in the valence band contributes to the narrowed band gap. The luminescence properties of Ag0.5La0.5Nb2O6 have been investigated for the first time. The luminescence is characterized by two emission centers with maximum wavelength near 460 and 530nm. The emission and excitation spectra, decay curves and the thermal quenching mechanism were discussed. Ag0.5La0.5Nb2O6 shows the efficient photocatalytic activities and the photodegradation rate for methylene blue dye (MB) can reach about 95% under visible light (>420nm) irradiation in 5h. The trapped experiments for the active species were tested and discussed, which verified that OH radicals could be the major active species in photocatalysis.

Luminescence, energy transfer and optical thermometry of a novel narrow red emitting phosphor: Cs2WO2F4:Mn4.

A novel red emitting Cs2WO2F4:Mn4+ phosphor was successfully synthesized by a two-step wet chemical method. The crystal structure, morphology, and elemental composition were confirmed by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The luminescence properties were investigated from emission, excitation and luminescence decay curves in the temperature region of 10-500 K. The application of non-contact optical thermometry of Cs2WO2F4:Mn4+ based on the fluorescence intensity ratio (FIR) of the two coupled anti-Stokes and Stokes sidebands is discussed. The as-prepared Cs2WO2F4:Mn4+ phosphor shows a bright narrow red emission at 632 nm under excitation by a blue lamp at 470 nm and it also presents a broad and yellow-white intrinsic tungstate emission (∼520 nm) under UV excitation. The mechanism of energy transfer from [WO2F4]2- (the sensitizer) to Mn4+ (the activator) is discussed.

A novel optical thermometry based on the energy transfer from charge transfer band to Eu3+-Dy3+ ions.

Optical thermometry based on the up-conversion intensity ratio of thermally coupled levels of rare earth ions has been widely studied to achieve an inaccessible temperature measurement in submicron scale. In this work, a novel optical temperature sensing strategy based on the energy transfer from charge transfer bands of W-O and Eu-O to Eu3+-Dy3+ ions is proposed. A series of Eu3+/Dy3+ co-doped SrWO4 is synthesized by the conventional high-temperature solid-state method. It is found that the emission spectra, emission intensity ratio of Dy3+ (572 nm) and Eu3+ (615 nm), fluorescence color, lifetime decay curves of Dy3+ (572 nm) and Eu3+ (615 nm), and relative and absolute sensitivities of Eu3+/Dy3+ co-doped SrWO4 are temperature dependent under the 266 nm excitation in the temperature range from 11 K to 529 K. The emission intensity ratio of Dy3+ (572 nm) and Eu3+ (615 nm) ions exhibits exponentially relation to the temperature due to the different energy transfer from the charge transfer bands of W-O and Eu-O to Dy3+ and Eu3+ ions. In this host, the maximum relative sensitivity Sr can be reached at 1.71% K-1, being higher than those previously reported material. It opens a new route to obtain optical thermometry with high sensitivity through using down-conversion fluorescence under ultraviolet excitation.

Influence of Doping and Excitation Powers on Optical Thermometry in Yb3+-Er3+ doped CaWO4.

Optical thermometry has been widely studied to achieve an inaccessible temperature measurement in submicron scale and it has been reported that the temperature sensitivity depends mainly on host types. In this work, we propose a new method to improve the optical temperature sensitivity of Yb3+-Er3+ co-doped CaWO4 phosphors by doping with Li+, Sr2+, and Mg2+ ions and by controlling excitation powers of 980 nm laser. It is found that the thermometric parameters such as upconversion emission intensity, intensity ratio of green-to-red emission, fluorescence color, emission intensity ratios of thermally coupled levels (2H11/2/4S3/2), and relative and absolute temperature sensitivity can be effectively controlled by doping with Li+, Sr2+, and Mg2+ ions in the Yb3+-Er3+ co-doped CaWO4 system. Moreover, the relative sensitivity SR and the absolute sensitivity SA are proved to be dependent on the pump power of 980 nm laser. The sensitivities of SR and SA in Yb3+-Er3+ co-doped CaWO4 increase about 31.5% and 12%, respectively, by doping with 1 mol% Sr2+.

Detecting the origin of luminescence in Er3+-doped hexagonal Na1.5Gd1.5F6 phosphors.

Understanding site-selective fluorescence is one of valuable importance for spectrum modulation. In this Letter, we observed the existence of two non-equivalent Gd-activated crystallographic sites in an Er3+-doped hexagonal Na1.5Gd1.5F6 phosphor. It is proved that two green emissions from the S3/24 level separately originate from the Gd1 (540 nm) and Na2/Gd2 (550-555 nm) crystallographic sites, and the 657 nm red emission from the F9/24 level only originates from Na2/Gd2 site through using the time-resolved luminescence spectra. The 142.2% absolute enhancement of the red emission is realized through the synergistic effect of ultraviolet downconversion and infrared upconversion induced by the 370 nm and 1.54 µm dual-mode excitation.

Excitation powder dependent optical temperature behavior of Er3+ doped transparent Sr0.69La0.31F2.31 glass ceramics.

The knowledge of the pump power for which the population of thermally coupled energy levels (TCL) changes with power increase is of valuable importance for optical temperature sensors. In this paper, novel Er3+ doped transparent Sr0.69La0.31F2.31 glass ceramics was fabricated successfully, and its structure is studied by XRD, TEM and HRTEM analyses. The 2H11/2/4S3/2, 4F9/2(1)/4F9/2(2), and 4I9/2(1)/4I9/2(2) levels of Er3+ are proved as TCL by analyzing the temperature dependent fluorescence intensity ratios. The spectrum split, thermal quenching ratio, population stability, and temperature sensitivity from three TCL are observed to be dependent on the pump power. A new fitting method has been developed to establish the relation between fluorescence intensity ratios and temperature. It is found that the combined use of 2H11/2/4S3/2 and 4F9/2(1)/4F9/2(2) as thermally coupled energy levels will get a more precise temperature reading from 62.7 K to 800 K with the help of low excitation power at 66.8 mW/mm2.

Enhancing the Feasibility of Microcystis aeruginosa as a Feedstock for Bioethanol Production under the Influence of Various Factors.

Microcystis aeruginosa, a freshwater microalga, is capable of producing and accumulating different types of sugars in its biomass which make it a good feedstock for bioethanol production. Present study aims to investigate the effect of different factors increasing growth rate and carbohydrates productivity of M. aeruginosa. MF media (modified BG11 media) and additional ingredients such as aminolevulinic acid (2 mM), lysine (2.28 mM), alanine (1 mM), and Naphthalene acetic acid (1 mM) as cytokine promoted M. aeruginosa growth and sugar contents. Salmonella showed growth-assisting effect on M. aeruginosa. Enhanced growth rate and carbohydrates contents were observed in M. aeruginosa culture grown at 25°C under red LED light of 90 µmolm(-2)s(-1) intensity. More greenish and carbohydrates rich M. aeruginosa biomass was prepared (final OD660 nm = 2.21 and sugar contents 10.39 mM/mL) as compared to control (maximum OD660 nm = 1.4 and sugar contents 3 mM/mL). The final algae biomass was converted to algae juice through a specific pretreatment method. The resulted algae Juice was used as a substrate in fermentation process. Highest yield of bioethanol (50 mM/mL) was detected when Brettanomyces custersainus, Saccharomyces cerevisiae, and Pichia stipitis were used in combinations for fermentation process as compared to their individual fermentation. The results indicated the influence of different factors on the growth rate and carbohydrates productivity of M. aeruginosa and its feasibility as a feedstock for fermentative ethanol production.

Tunable White Fluorescent Copper Gallium Sulfide Quantum Dots Enabled by Mn Doping.

Fluorescence of semiconductor quantum dots (QDs) can be tuned by engineering the band gap via size and composition control and further doping them with impurity ions. Targeting on highly bright white-emissive I-III-VI -type copper gallium sulfide (Cu-Ga-S, CGS) host QDs with the entire visible spectral coverage of blue to red, herein, Mn(2+) ion doping, through surface adsorption and lattice diffusion is fulfilled. Upon doping a distinct Mn emission from (4)T1-(6)A1 transition successfully appears in white photoluminescence (PL) of undoped CGS/ZnS core/shell QDs and with varying Mn concentration a systematic white spectral evolution of CGS:Mn/ZnS QDs is achievable with high PL quantum yield retained. The origins of white PL of CGS:Mn/ZnS QDs that is well decomposed into three emission bands are appropriately assigned. The resulting single-phased, doped QDs are then employed as near-UV-to-white down converters for the fabrication of white light-emitting diodes (LEDs). Electroluminescent properties of white QD-LEDs depending on Mn concentration of CGS:Mn/ZnS QDs and forward current are also discussed in detail.

In situ hydroxyapatite nanofiber growth on calcium borate silicate ceramics in SBF and its structural characteristics.

A novel calcium silicate borate Ca11Si4B2O22 ceramic was firstly prepared by the conventional solid-state reaction. In vitro hydroxyapatite mineralization was investigated by soaking the ceramics in simulated body fluid (SBF) solutions at body temperature (37 °C) for various time periods. Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) measurements were applied to investigate the samples before and after the immersion of ceramics in SBF solution. The elemental compositions of a hydroxyapatite layer on the ceramics during the mineralization were confirmed by X-ray energy-dispersive spectra (EDS). Meanwhile, the bending strength and elastic modulus of Ca11Si4B2O22 ceramics were also measured, which indicate that the biomaterials based on Ca11Si4B2O22 ceramics possess bioactivity and might be a potential candidate as biomaterials for hard tissue repair. The bioactive mineralization ability was evaluated on the base of its crystal structural characteristics, i.e., silanol (Si-OH) and B-OH groups can be easily induced on the surface of Ca11Si4B2O22 ceramics soaked in SBF solutions.

The effect of 1,8-cineole inhalation on preoperative anxiety: a randomized clinical trial.

The aim of this study was to investigate the effect of inhalation of eucalyptus oil and its constituents on anxiety in patients before selective nerve root block (SNRB). This study was a randomized controlled trial carried out in 62 patients before SNRB. The patients were randomized to inhale limonene, 1,8-cineole, or eucalyptus oil, each at concentrations of 1% vol/vol in almond oil or almond oil (control). Anxiety-visual analog scale (A-VAS), state-trait anxiety inventory (STAI), profile of mood states (POMS), pain-visual analog scale (P-VAS), blood pressure, and pulse rate were measured before and after inhalation prior to SNRB. Measures of anxiety, including A-VAS (P < 0.001), STAI (P = 0.005), and POMS (P < 0.001), were significantly lower in 1,8-cineole than in the control group and significantly greater in 1,8-cineole than in the eucalyptus group in A-VAS. P-VAS was significantly lower after than before inhalation of limonene, 1,8-cineole, and eucalyptus, despite having no significant difference in the four groups compared with control group. 1,8-Cineole, a major constituent of eucalyptus, was effective in decreasing anxiety before SNRB. The present findings suggest that inhalation of 1,8-cineole may be used to relieve anxiety before, during, and after various operations, in addition to SNRB.

Theasaponin E1 as an effective ingredient for anti-angiogenesis and anti-obesity effects.

Theasaponin E1 (TSE1) has been suggested to have higher biological activity than other saponins present in tea seed. Saponins have recently been considered as a potential chemotherapeutic agent for treating cancer. We examined the anti-angiogenic and anti-obesity properties of TSE1 contributing to anti-cancer efficacy. Treating with a 10 µg/mL concentration of TSE1 completely inhibited tube formation in human umbilical vein endothelial cells (HUVECs). TSE1 showed toxicity toward cancer cells and inhibited in vivo growth of the tumor. The vascular endothelial growth factor (VEGF) receptor complex was suppressed, leading to the inhibition of protein kinase B (Akt) expression and down-regulation of nuclear factor-kappa B (NF-kB) activation. The differentiating 3T3-L1 cells treated with TSE1 had decreased lipid droplet formation measured by Oil Red O staining. Reduced weight was measured in mice fed with a TSE1 plus high-fat diet. The results taken together, and particularly the NF-kB inhibition, suggest that TSE1 may have multi-target action for treating cancer as a novel chemotherapeutic agent.