A zero-thermal-quenching phosphor.

Phosphor-converted white light-emitting diodes (pc-WLEDs) are efficient light sources used in lighting, high-tech displays, and electronic devices. One of the most significant challenges of pc-WLEDs is the thermal quenching, in which the phosphor suffers from emission loss with increasing temperature during high-power LED operation. Here, we report a blue-emitting Na3-2xSc2(PO4)3:xEu2+ phosphor (λem = 453 nm) that does not exhibit thermal quenching even up to 200 °C. This phenomenon of zero thermal quenching originates from the ability of the phosphor to compensate the emission losses and therefore sustain the luminescence with increasing temperature. The findings are explained by polymorphic modification and possible energy transfer from electron-hole pairs at the thermally activated defect levels to the Eu2+ 5d-band with increasing temperature. Our results could initiate the exploration of phosphors with zero thermal quenching for high-power LED applications.

A Phosphosilicate Compound, NaCa3PSiO8: Structure Solution and Luminescence Properties.

NaCa3PSiO8 was synthesized in a microwave-assisted solid-state reaction. The crystal structure of the synthesized compound was solved using a least-squares method, followed by simulated annealing. The compound was crystallized in the orthorhombic space group Pna21, belonging to Laue class mmm. The structure consisted of two layers of cation planes, each of which contained three cation channels. The cation channels in each of the layers ran antiparallel to that of the adjacent layer. All the major cations together constituted four distinct crystallographic sites. The Rietveld refinement of the powder X-ray diffraction data, followed by the maximum-entropy method analysis, confirmed the obtained structure solutions. The electronic band structure of the compound was analyzed through density function theory calculations. Luminescence properties of the compound, upon activating with Eu2+ ions, were analyzed through photoluminescence measurements and decay profile analysis. The compound was found to exhibit green luminescence centered at ∼502 nm, with a typical broadband emission due to the transition from the crystal-field split 4f65d to 4f7 levels.

Engineering the Lattice Site Occupancy of Apatite-Structure Phosphors for Effective Broad-Band Emission through Cation Pairing.

A series of britholite compounds were synthesized by simultaneous introduction of trivalent La3+ and Si4+ ions into an apatite structure. The variations in the average structure, electronic band structure, and microstructural properties resulting from the introduction of cation pairs were analyzed as a function of their concentration. The effects of the structural variance and microstructural properties on the broad-band-emitting activator ions were studied by introducing Eu2+ ions as activators. For the resulting compound, which had dual emission bands in the blue and yellow regions of the spectrum, the emission peak position and strength were dependent upon the concentration of La3+-Si4+ pairs. By engineering the relative sizes of the two possible activator sites in the structure, 4f and 6h, through the introduction of a combination of trivalent La3+ and a polyanion, the preferential site occupancy of the activator ions was favorably altered. Additionally, the activator ions responsible for the lower-Stokes-shifted blue component of the emission functioned as a sensitizer of the larger-Stokes-shifted yellow-emitting activators, and predominantly yellow-emitting phosphors were achieved. The feasibility of developing a white light-emitting solid-state device using the developed phosphor was also demonstrated.

Laparoscopically assisted suprapubic surgery for adnexal tumors under epidural anesthesia.

OBJECTIVE: To evaluate the feasibility and safety of laparoscopically assisted surgery for benign ovarian tumors via a single suprapubic incision under epidural anesthesia. METHODS: Forty-three patients underwent laparoscopically assisted surgery via a single suprapubic incision under epidural anesthesia. Types of surgery were classified as follows: type I - suprapubic incision surgery without laparoscopic support, type II - suprapubic incision surgery with laparoscopic support but without CO2 inflation; and type III - suprapubic incision surgery with laparoscopic support and CO2 inflation. RESULTS: Type I, II, and III procedures were performed on 16, 21, and six patients, respectively. Most patients (n = 35) were discharged on postoperative day 1 or 2. No surgical complication was encountered. Types of surgery exhibited different surgical characteristics. Type I was adopted for larger diameter tumors than types II or III (p = .016), whereas type III had a longer operative time (p = .024) than types I and II. Other characteristics, such as age, body mass index, and length of hospital stay, did not differ significantly among surgical types. CONCLUSION: Laparoscopically assisted surgery for adnexal tumors via a single suprapubic incision under epidural anesthesia is feasible and safe, and should be viewed as an alternative approach to conventional minimally invasive surgery.

Narsarsukite-structure fluorosilicate as a blue component for white LEDs: structural and optical properties.

A new blue-emitting phosphor, K2ScSi4O10F:Eu>2+ (KSSOF:Eu2+), was synthesized through a solid-state reaction. The structural and optical properties of KSSOF:Eu2+ phosphor, in addition to its thermal quenching and fabrication of white LEDs (WLEDs), were investigated for the first time. The phosphor showed broad blue emission, with a maximum at ∼434 nm under near-ultraviolet excitation due to 5d→4f transition of the Eu2+ ion. The critical distance was calculated to be 12 Šusing the critical concentration of Eu2+ and Dexter's theory for energy transfer. WLEDs were fabricated by blending KSSOF:Eu2+, commercial Lu3Al5O12:Ce3+, and (Sr,Ca)AlSiN3:Eu2+ phosphors, showed a high color rendering index of 88 at a correlated color temperature of 4134 K under a forward bias current of 100 mA.

Control of chromaticity by phosphor in glasses with low temperature sintered silicate glasses for LED applications.

Phosphor-in-glass (PiG) color converters for LED applications were fabricated with a mixture of phosphors, Y3Al5O12:Ce³âº (yellow) and CaAlSiN3:Eu²âº (red). The low sintering temperature (550°C) of SiO2-Na2O-RO (R=Ba, Zn) glass powder enabled the inclusion of CaAlSiN3:Eu²âº (red) phosphor which cannot be embedded with conventional glass powders for PiGs. By simply varying the mixing ratio of glass to phosphors as well as the ratio of yellow to red phosphors, the facile control of the CIE chromaticity coordinates and correlated color temperature of the LED following the Planckian locus has been achieved. Phosphors were well distributed within the glass matrix without noticeable reactions, preserving the enhanced thermal quenching property of the PiG compared to those with silicone resins, for LEDs.

Photoenergy Harvesting by Photoacid Solution.

Solar energy has seen 180 years of development since the discovery of the photovoltaic effect, having achieved the most successful commercialization in the energy-harvesting fields. Despite its long history, even the most state-of-the-art photovoltaics remain confined to solid-state devices, limiting spatial and light utilization efficiencies. Herein, a liquid-state photoenergy harvester based on a photoacid (PA), a chemical that releases protons upon light irradiation and recombines with them in the dark through a fully reversible reaction, is demonstrated. Asymmetric light exposure on a PA solution contained in a transparent tube generates a pH gradient (ΔpH = 2) along the exposed and dark regions, which charges the Nernst potential up to 0.7 V across the two electrodes embedded at each end, as if a capacitor. Owing to the reversibility of PAs, a PA-driven liquid-state photoenergy harvester (PLPH) generates capacitive currents up to 0.72 mA m-2  on an irradiation. Notably, the transparent nature of the PLPH enables vertical stacking up to 25 units, which multiplies the light-harvesting efficiencies by over 1000%. This unique approach provides a new route to harness solar energy with a form-factor-free design that maximizes spatial and light-use efficiencies.

Surface Activity-Tuned Metal Oxide Chemiresistor: Toward Direct and Quantitative Halitosis Diagnosis.

Continuous monitoring of hydrogen sulfide (H2S) in human breath for early stage diagnosis of halitosis is of great significance for prevention of dental diseases. However, fabrication of a highly selective and sensitive H2S gas sensor material still remains a challenge, and direct analysis of real breath samples has not been properly attempted, to the best of our knowledge. To address the issue, herein, we introduce facile cofunctionalization of WO3 nanofibers with alkaline metal (Na) and noble metal (Pt) catalysts via the simple addition of sodium chloride (NaCl) and Pt nanoparticles (NPs), followed by electrospinning process. The Na-doping and Pt NPs decoration in WO3 grains induces the partial evolution of the Na2W4O13 phase, causing the buildup of Pt/Na2W4O13/WO3 multi-interface heterojunctions that selectively interacts with sulfur-containing species. As a result, we achieved the highest-ranked sensing performances, that is, response (Rair/Rgas) = 780 @ 1 ppm and selectivity (RH2S/REtOH) = 277 against 1 ppm ethanol, among the chemiresistor-based H2S sensors, owing to the synergistic chemical and electronic sensitization effects of the Pt NP/Na compound cocatalysts. The as-prepared sensing layer was proven to be practically effective for direct, and quantitative halitosis analysis based on the correlation (accuracy = 86.3%) between the H2S concentration measured using the direct breath signals obtained by our test device (80 cases) and gas chromatography. This study offers possibilities for direct, highly reliable and rapid detection of H2S in real human breath without the need of any collection or filtering equipment.

Confinement of Ultrasmall Bimetallic Nanoparticles in Conductive Metal-Organic Frameworks via Site-Specific Nucleation.

Conductive metal-organic frameworks (cMOFs) are emerging materials for various applications due to their high surface area, high porosity, and electrical conductivity. However, it is still challenging to develop cMOFs having high surface reactivity and durability. Here, highly active and stable cMOF are presented via the confinement of bimetallic nanoparticles (BNPs) in the pores of a 2D cMOF, where the confinement is guided by dipolar-interaction-induced site-specific nucleation. Heterogeneous metal precursors are bound to the pores of 2D cMOFs by dipolar interactions, and the subsequent reduction produces ultrasmall (≈1.54 nm) and well-dispersed PtRu NPs confined in the pores of the cMOF. PtRu-NP-decorated cMOFs exhibit significantly enhanced chemiresistive NO2 sensing performances, owing to the bimetallic synergies of PtRu NPs and the high surface area and porosity of cMOF. The approach paves the way for the synthesis of highly active and conductive porous materials via bimetallic and/or multimetallic NP loading.

Chemiresistive Hydrogen Sensors: Fundamentals, Recent Advances, and Challenges.

Hydrogen (H2) is one of the next-generation energy sources because it is abundant in nature and has a high combustion efficiency that produces environmentally benign products (H2O). However, H2/air mixtures are explosive at H2 concentrations above 4%, thus any leakage of H2 must be rapidly and reliably detected at much lower concentrations to ensure safety. Among the various types of H2 sensors, chemiresistive sensors are one of the most promising sensing systems due to their simplicity and low cost. This review highlights the advances in H2 chemiresistors, including metal-, semiconducting metal oxide-, carbon-based materials, and other materials. The underlying sensing mechanisms for different types of materials are discussed, and the correlation of sensing performances with nanostructures, surface chemistry, and electronic properties is presented. In addition, the discussion of each material emphasizes key advances and strategies to develop superior H2 sensors. Furthermore, recent key advances in other types of H2 sensors are briefly discussed. Finally, the review concludes with a brief outlook, perspective, and future directions.

Hydrogen Sensors Based on MoS2 Hollow Architectures Assembled by Pickering Emulsion.

For rapid hydrogen gas (H2) sensing, we propose the facile synthesis of the hollow structure of Pt-decorated molybdenum disulfide (h-MoS2/Pt) using ultrathin (mono- or few-layer) two-dimensional nanosheets. The controlled amphiphilic nature of MoS2 surface produces ultrathin MoS2 NS-covered polystyrene particles via one-step Pickering emulsification. The incorporation of Pt nanoparticles (NPs) on the MoS2, followed by pyrolysis, generates the highly porous h-MoS2/Pt. This hollow hybrid structure produces sufficiently permeable pathways for H2 and maximizes the active sites of MoS2, while the Pt NPs on the hollow MoS2 induce catalytic H2 spillover during H2 sensing. The h-MoS2/Pt-based chemiresistors show sensitive H2 sensing performances with fast sensing speed (response, 8.1 s for 1% of H2 and 2.7 s for 4%; and recovery, 16.0 s for both 1% and 4% H2 at room temperature in the air). These results mark the highest H2 sensing speed among 2D material-based H2 sensors operated at room temperature in air. Our fabrication method of h-MoS2/Pt structure through Pickering emulsion provides a versatile platform applicable to various 2D material-based hollow structures and facilitates their use in other applications involving surface reactions.

Single-Atom Pt Stabilized on One-Dimensional Nanostructure Support via Carbon Nitride/SnO2 Heterojunction Trapping.

Catalysis with single-atom catalysts (SACs) exhibits outstanding reactivity and selectivity. However, fabrication of supports for the single atoms with structural versatility remains a challenge to be overcome, for further steps toward catalytic activity augmentation. Here, we demonstrate an effective synthetic approach for a Pt SAC stabilized on a controllable one-dimensional (1D) metal oxide nano-heterostructure support, by trapping the single atoms at heterojunctions of a carbon nitride/SnO2 heterostructure. With the ultrahigh specific surface area (54.29 m2 g-1) of the nanostructure, we obtained maximized catalytic active sites, as well as further catalytic enhancement achieved with the heterojunction between carbon nitride and SnO2. X-ray absorption fine structure analysis and HAADF-STEM analysis reveal a homogeneous atomic dispersion of Pt species between carbon nitride and SnO2 nanograins. This Pt SAC system with the 1D nano-heterostructure support exhibits high sensitivity and selectivity toward detection of formaldehyde gas among state-of-the-art gas sensors. Further ex situ TEM analysis confirms excellent thermal stability and sinter resistance of the heterojunction-immobilized Pt single atoms.

Publisher Correction: Probing molecule-like isolated octahedra via phase stabilization of zero-dimensional cesium lead halide nanocrystals.

The original version of this Article contained an error in the title, which incorrectly read 'Probing molecule-like isolated octahedra via-phase stabilization of zero-dimensional cesium lead halide nanocrystals.' The correct version states 'via phase stabilization' in place of 'via-phase stabilization'. This has been corrected in both the PDF and HTML versions of the Article.

Probing molecule-like isolated octahedra via-phase stabilization of zero-dimensional cesium lead halide nanocrystals.

Zero-dimensional (0D) inorganic perovskites have recently emerged as an interesting class of material owing to their intrinsic Pb2+ emission, polaron formation, and large exciton binding energy. They have a unique quantum-confined structure, originating from the complete isolation of octahedra exhibiting single-molecule behavior. Herein, we probe the optical behavior of single-molecule-like isolated octahedra in 0D Cesium lead halide (Cs4PbX6, X = Cl, Br/Cl, Br) nanocrystals through isovalent manganese doping at lead sites. The incorporation of manganese induced phase stabilization of 0D Cs4PbX6 over CsPbX3 by lowering the symmetry of PbX6 via enhanced octahedral distortion. This approach enables the synthesis of CsPbX3 free Cs4PbX6 nanocrystals. A high photoluminescence quantum yield for manganese emission was obtained in colloidal (29%) and solid (21%, powder) forms. These performances can be attributed to structure-induced confinement effects, which enhance the energy transfer from localized host exciton states to Mn2+ dopant within the isolated octahedra.

Colloidal Organolead Halide Perovskite with a High Mn Solubility Limit: A Step Toward Pb-Free Luminescent Quantum Dots.

Organolead halide perovskites have emerged as a promising optoelectronic material for lighting due to its high quantum yield, color-tunable, and narrow emission. Despite their unique properties, toxicity has intensified the search for ecofriendly alternatives through partial or complete replacement of lead. Herein, we report a room-temperature synthesized Mn2+-substituted 3D-organolead perovskite displacing ∼90% of lead, simultaneously retaining its unique excitonic emission, with an additional orange emission of Mn2+ via energy transfer. A high Mn solubility limit of 90% was attained for the first time in lead halide perovskites, facilitated by the flexible organic cation (CH3NH3)+ network, preserving the perovskite structure. The emission intensities of the exciton and Mn were influenced by the halide identity that regulates the energy transfer to Mn. Homogeneous emission and electron spin resonance characteristics of Mn2+ indicate a uniform distribution of Mn. These results suggest that low-toxicity 3D-CH3NH3Pb1-xMnxBr3-(2x+1)Cl2x+1 nanocrystals may be exploited as magnetically doped quantum dots with unique optoelectronic properties.

Hydrophobic Organic Skin as a Protective Shield for Moisture-Sensitive Phosphor-Based Optoelectronic Devices.

A moisture-stable, red-emitting fluoride phosphor with an organic hydrophobic skin is reported. A simple strategy was employed to form a metal-free, organic, passivating skin using oleic acid (OA) as a hydrophobic encapsulant via solvothermal treatment. Unlike other phosphor coatings that suffer from initial efficiency loss, the OA-passivated K2SiF6:Mn4+ (KSF-OA) phosphor exhibited the unique property of stable emission efficiency. Control of thickness and a highly transparent passivating layer helped to retain the emission efficiency of the material after encapsulation. A moisture-stable KSF-OA phosphor could be synthesized because of the exceptionally hydrophobic nature of OA and the formation of hydrogen bonds (F···H) resulting from the strong interactions between the fluorine in KSF and hydrogen in OA. The KSF-OA phosphor exhibited excellent moisture stability and maintained 85% of its emission intensity even after 450 h at high temperature (85 °C) and humidity (85%). As a proof-of-concept, this strategy was used for another moisture-sensitive SrSi2O2N2:Eu2+ phosphor which showed enhanced moisture stability, retaining 85% of emission intensity after 500 h under the same conditions. White light-emitting devices were fabricated using surface-passivated KSF and Y3Al5O12:Ce3+ which exhibited excellent color rendering index of 86, under blue LED excitation.

Peptide YY producing strumal carcinoid tumor of the ovary in a postmenopausal woman: a rare cause of chronic constipation.

Strumal carcinoid tumor of the ovary is a rare subtype of ovarian carcinoid tumors; it is characterized by an intimate mixture of thyroid and carcinoid tissues. We present a case of a 64-year-old woman who presented with the chief complaint of persistent, severe constipation for over 5 years; she was later found to have an ovarian strumal carcinoid tumor. Computed tomography showed a well-defined solid mass measuring 6.4 cm at the right adnexa. The patient underwent right salpingo-oophorectomy and was histopathologically diagnosed as having a strumal carcinoid tumor. Immunohistochemical examination showed immunoreactivity for peptide YY (PYY), which exerts an inhibitory effect on the peristaltic actions of the distal intestine. After surgery, the patient's constipation resolved rapidly, suggesting a correlation between PYY producing ovarian carcinoid tumor and constipation. This is the first case report of PYY producing primary strumal carcinoid tumor of the ovary associated with persistent, severe constipation from Korea.

[A case of idiopathic colitis developed after barium enema].

It has been reported that colitis may be associated with intrarectally administered drugs or chemicals. Colonotoxicity may results from conventional medical therapy, herbal or other illicit drugs, contrast materials, and detergents. Clues that a colitis may be due to an intrarectally administered agent include perianal excoriation, segmental distal colitis due to a concentration gradient from enema administration, and recent diagnostic or therapeutic administration of high risk solutions such as hypertonic contrast agents or detergent enemas. Barium is a highly viscous contrast agent that is insoluble in water. Barium enemas are usually very safe. Also, no case report of barium-induced chemical colitis has been reported yet. We report a case of chemical colitis with colonic stricture occurring after the barium enema for diagnostic purpose.

Effective Heat Dissipation from Color-Converting Plates in High-Power White Light Emitting Diodes by Transparent Graphene Wrapping.

We have developed a hybrid phosphor-in-glass plate (PGP) for application in a remote phosphor configuration of high-power white light emitting diodes (WLEDs), in which single-layer graphene was used to modulate the thermal characteristics of the PGP. The degradation of luminescence in the PGP following an increase in temperature could be prevented by applying single-layer graphene. First, it was observed that the emission intensity of the PGP was enhanced by about 20% with graphene wrapping. Notably, the surface temperature of the graphene-wrapped PGP (G-PGP) was found to be higher than that of the bare PGP, implying that the graphene layer effectively acted as a heat dissipation medium on the PGP surface to reduce the thermal quenching of the constituent phosphors. Moreover, these experimental observations were clearly verified through a two-dimensional cellular automata simulation technique and the underlying mechanisms were analyzed. As a result, the proposed G-PGP was found to be efficient in maintaining the luminescence properties of the WLED, and is a promising development in high power WLED applications. This research could be further extended to generate a new class of optical or optoelectronic materials with possible uses in a variety of applications.

An unusual case of pedunculated subserosal leiomyosarcoma of the uterus mimicking ovarian carcinoma.

BACKGROUND: Leiomyosarcoma of the uterus is an extremely rare but highly aggressive tumor that accounts for only 1-2 % of uterine malignancies, and is usually associated with a dismal outcome. CASE PRESENTATION: The authors present an unusual case of pedunculated subserosal leiomyosarcoma of the uterus mimicking ovarian carcinoma. A 57-year-old postmenopausal woman presented with progressive low abdominal pain and urinary frequency. Pelvic magnetic resonance imaging revealed a large adnexal mass with carcinomatosis peritonei. Laboratory examination revealed an elevated serum CA-125 level (398.4 U/ml). The patient underwent exploratory laparotomy under suspicion of ovarian malignancy. Frozen section indicated malignancy originating from the uterus, and thus, total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, pelvic and para-aortic lymph node dissection, and mass excision were performed. Subsequent histopathologic examination resulted in a final diagnosis of leiomyosarcoma of the uterus. The patient's postoperative course was uneventful, and gemcitabine and docetaxel adjuvant chemotherapy was administered. CONCLUSION: The authors report an unusual case of pedunculated subserosal leiomyosarcoma of the uterus mimicking ovarian carcinoma.