Search

Red-emitting CsPbI3 perovskite materials are still limited in various commercial applications because of their stability being related to the morphology and dimension. In this paper, a solvothermal method was developed to fabricate CsPbI3 perovskite nanomaterials with governable morphologies (e.g., nanoplatelets (NPLs) to nanocubes (NCs)) and dimensions ranging from the zero-dimensional (0D) Cs4PbI6 to the three-dimensional (3D) CsPbI3. By adjusting the amount of Cs precursor solutions, the photoluminescence (PL) peak position of the samples was tuned over the whole red-emitting region (from 607 to 700 nm). In addition, the reaction temperature affected the PL properties of the samples and demonstrated that temperature was critical to control the performance of CsPbI3 perovskite materials. Furthermore, sodium dodecyl benzene sulfonate (SDBS) was chosen as the additive to improve the stability of the prepared samples. The result provided an approach to get CsPbI3 perovskite nanocrystals with stabile PL. Finally, CsPbI3 NPLs embedded in the polystyrene film displayed bright and stable white light emission. [ABSTRACT FROM AUTHOR]

Although serogroup W ST-11 complex (cc11) (W:cc11) Neisseria meningitidis has been widespread in China over the past ten years, its origin and genetic relatedness has not yet been described. In this study, we described the genetic relatedness and discuss the possible origin of Chinese W:cc11 isolates by comparing their genome sequences with those of other cc11 strains globally. Comparative genomic analysis with geo-temporally diverse cc11 isolates showed that the Chinese W:cc11 isolates exclusively formed two closely related subclusters within a distinct sublineage (proposed as the Chinese-strain sublineage) of lineage 11.1 close to the interface between the Hajj-strain sublineage and the South American-strain sublineage. Several isolates from Africa and Europe were closely related to the Chinese subclusters which were largely segregated from one another among distinct provinces of China. No alleles were identified that were unique to the Chinese isolates as a whole, though each subcluster possessed unique alleles differentiating itself from the other subcluster as well as closely related isolates within the extended sublineage. Three genes differentiated the two subclusters with allele combinations that were each present among the non-Chinese isolates within the wider sublineage. These results indicate that the Chinese W:cc11 isolates formed part of a previously undescribed W:cc11 sublineage that is closely related to, but distinct from, the Hajj-strain sublineage and South American-strain sublineage. The geographical source of the Chinese subclusters was indeterminate based on available data. [ABSTRACT FROM AUTHOR]

A method for precision small-angle measurement is proposed. This method is based on the total-internal-reflection effect of a light beam at a pair of glass prisms. Angular displacement of the light beam is measured when the intensity change of the reflected beam is detected as a result of the relative phase shift between the s- and the p-polarized beams. An initial phase shift between the s- and the p-polarized components is introduced to increase measurement sensitivity. For increased measurement linearity and reduced effect of laser power fluctuation on the output, a differential method is used in which the light beam is split equally into two beams, each reflected at a prism and detected by a photodiode. The output is obtained as the difference of the two detected intensities divided by their sum. A prototype device was built, which demonstrated a nonlinearity error of 1.3% in a measurement range of [+ or -] 0.6 [degrees] or 0.4% in [+ or -] 0.3 [degrees]. The peak-to-peak noise level was found to be at approximately 0.5 arc sec. This noise level can be reduced further and resolution increased by a reduction of the measurement range. [C] 2001 Optical Society of America OCIS codes: 120.0120, 120.3930, 120.3940, 120.5700, 260.3160, 260.5430, 260.6970.

The polysaccharide capsule (CPS) of Campylobacter jejuni is a virulence factor linked to cell surface carbohydrate diversity which mainly determines the serotypes. Thirty-four CPS gene cluster structures have been published and some of them can be distinguished by multiple-PCR. Penner serotypes HS1/44c, HS2, HS4c, HS19, HS23/36c and HS41 are markers for Guillain—Barré syndrome (GBS). The capsules may contribute to GBS susceptibility. Analysis of 18 CPS loci revealed high gene content diversity and a mosaic nature of the capsule loci, which are possibly due to gene gain/loss events, and demonstrated a high degree of conservation of genes within serotypes/serotype complexes. A method of multiple-PCR was developed to distinguish five specific serotypes and three GBS-related serotypes. Primers specific for each capsule type were designed on the basis of paralogs or a unique DNA region of the CPS locus. The multiple-PCR can distinguish the eight serotypes in two PCRs with sensitivity and specificity of 100% using 227 strains of known Penner type. The multiple-PCR method will help to distinguish serotypes simply and rapidly. [ABSTRACT FROM AUTHOR]

ABSTRACT In this study, a series of LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) down-converting phosphors were synthesized using a modified sol-gel combustion method, and their photoluminescence (PL) properties were investigated as a function of activator concentration and annealing temperature. The resultant particles were characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, UV/Vis diffuse reflectance spectroscopy and PL spectra. The highly crystalline LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) phosphors with an average size of 200-300 nm obtained at 1100°C have an orthorhombic aeschynite-type structure and exhibit the highest luminescent intensity in our study range. The emission spectra of LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) phosphors under excitations at UV/blue sources are mainly composed of characteristic peaks arising from the f-f transitions of RE3+, including 489 nm (5D4 → 7F6) and 545 nm (5D4 → 7F5) for Tb3+, 476 and 482 nm (4F9/2 → 6H15/2) and 571 nm (4F9/2 → 6H13/2) for Dy3+, and 545 nm (5F4 + 5S2 → 5I8) for Ho3+, respectively. The luminescent mechanisms were further investigated. It can be expected that these phosphors are of intense interest and potential importance for many optical applications. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Hollow hamburger-like and other coupled-layered ZnO microstructures have been fabricated by a facile solvothermal process using the mixture of water and alcohol as solvents. The volume ratios of water/glycerol play an important role for the morphologies of the microstructures. In the case of a volume ratio of 1/2, the hamburger-like ZnO microstructures are created by employing zinc glycerolate (C3H6O3Zn) as a sacrificial template. A possible formation process from precursor C3H6O3Zn to ZnO is proposed by arresting a series of intermediate phases and the formation mechanism of the microstructures is proposed accordingly. The volume ratios of water/glycerol, such as 1/10, 1/6, 1/4, 1/2 and 1/1, were adjusted to create microstructures with various morphologies. The results indicated that the morphologies of the resulting samples changed from quasi-rhombic C3H6O3Zn plates to various coupled-layered ZnO microstructures, suggesting that water is responsible for the formation of coupled-layered structures. In addition, investigations into the formation of ZnO microstructures in mixtures of water and various alcohols, including water/ethanol, water/isopropyl alcohol, water/n-butyl alcohol, water/ethylene glycol and water/glycerol, reveal that alcohols are crucial for control of the morphologies of the microstructures. The multi-hydroxyl alcohols, e.g. ethylene glycol and glycerol, favour the formation of hollow structures compared with the case of single-hydroxyl alcohols. [ABSTRACT FROM AUTHOR]

Micro- and nano-structures of iron oxide with tunable morphologies were fabricated through a solvothermal process by adjusting experimental parameters. In this route, the ethylene glycol (EG) solution of ferric chloride hexahydrate (FeCl3·6H2O), sodium bicarbonate (NaHCO3), and ethylenediamine (EDA) was heat-treated to create the micro- and nano-structures of Fe3O4, where EG acted as both solvent and reducing agent. NaHCO3 and EDA were crucial for the morphology and size of these micro- and nano-structures. Fe3O4 micro- and nano-structures revealed solid, porous and hollow morphologies by changing the reaction time, the type of solvent, and the amount of EDA and NaHCO3. Fe3O4 nanoparticles were created by controlling experimental parameters. As the reaction progressed, nanoparticles aggregated together to form solid Fe3O4 spheres, and then inner nanoparticles dissolved and recrystallized onto the outer shell of Fe3O4 spheres having been obtained through agglomerating together and then gradually developing into hollow micro- and nano-spheres due to an Ostwald ripening mechanism. Hematite (α-Fe2O3) was synthesized using ethyl alcohol instead of EG. These magnetic micro- and nano-structures revealed excellent magnetic properties. [ABSTRACT FROM AUTHOR]

CdTe0.5Se0.5/Cd0.5Zn0.5S core/shell quantum dots (QDs) with a tunable photoluminescence (PL) range from yellow to dark red (up to a PL peak wavelength of 683 nm) were fabricated using various reaction systems. The core/shell QDs created in the reaction solution of trioctylamine (TOA) and oleic acid (OA) at 300 °C exhibited narrow PL spectra and a related low PL efficiency (38%). In contrast, the core/shell QDs prepared in the solution of 1-octadecene (ODE) and hexadecylamine (HDA) at 200 °C revealed a high PL efficiency (70%) and broad PL spectra. This phenomenon is ascribed that the precursor of Cd, reaction temperature, solvents, and ligands affected the formation process of the shell. The slow growth rate of the shell in the solution of ODE and HDA made QDs with a high PL efficiency. Metal acetate salts without reaction with HDA led to the core/shell QDs with a broad size distribution. [ABSTRACT FROM AUTHOR]

ABSTRACT A new ion sensor based on hybrid SiO2-coated CdTe nanocrystals (NCs) was prepared and applied for sensitive sensing of Cu2+ and Ag+ for the selective quenching of photoluminescence (PL) of NCs in the presence of ions. As shown by ion detection experiments conducted in pure water rather than buffer solution, PL responses of NCs were linearly proportional to concentrations of Cu2+ and Ag+ ions < 3 and 7 uM, respectively. Much lower detection limits of 42.37 nM for Cu2+ and 39.40 nM for Ag+ were also observed. In addition, the NC quenching mechanism was discussed in terms of the characterization of static and transient optical spectra. The transfer and trapping of photoinduced charges in NCs by surface energy levels of CuS and Ag2S clusters as well as surface defects generated by the exchange of Cu2+ and Ag+ ions with Cd2+ ion in NCs, resulted in PL quenching and other optical spectra changes, including steady-state absorption and transient PL spectra. It is our hope that these results will be helpful in the future preparation of new ion sensors. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Hydrophobic oleic acid-capped CdSe/Cd x Zn1−x S core/shell quantum dots (QDs) with high photoluminescence (PL) efficiency of 62% and a PL peak wavelength of 602nm were assembled in SiO2 particles through a novel silanization technique. Ligand exchange (3-mercaptopropyltrimethoxysilane (MPS) instead of oleic acid) occurred via the connection of mercapto groups and QDs when MPS was added in the toluene solution of the QDs. After being silanized using MPS, partially hydrolyzed tetraethyl orthosilicate (TEOS) was attached to the surface of the silanized QDs. The hydrophobic CdSe/Cd x Zn1−x S QDs were then transferred from toluene phase to water phase by the hydrolysis of TEOS through the addition of ethanol, ammonia, and water. Further hydrolysis and condensation of the TEOS and MPS causes them to form assemblies in the water phase. MPS is crucial for proper assembly of the QDs in SiO2 particles and for controlling the size of resulting SiO2 particles. The resulting SiO2 particles exhibited tunable diameters from several tens to 100nm. After being encapsulated in SiO2 particles, the QDs revealed a PL efficiency of 25%. Because of the resulting SiO2 particles encapsulating multiple hydrophobic CdSe/Cd x Zn1−x S QDs and having a functional surface (mercapto group), they are applicable to bio-probes. [Copyright &y& Elsevier]