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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]

Background: Neisseria meningitidis (N.meningitidis) bacteria belonging to clonal complex 4821 (CC4821) have been mainly reported in China and have been characterized by a high resistance rate to ciprofloxacin (CIP). The aim of this study was to assess the evolution of the DNA gyrase A (gyrA) gene from N.meningitidis CC4821 strains collected in China between 1978 and 2016. The complete sequence of gyrA gene from 77 strains are reported in this study and analyzed in the context of publicly available sequences from N. meningitidis of other CCs as well as other Neisseria species. Results: The phylogenetic analysis of CC4821 gyrA gene reveals at least 5 distinct genetic clusters. These clusters are not CC4821-specific showing that gyrA evolution is independent of CC4821 evolution. Some clusters contain sequences from other Neisseria species. Recombination within N.meningitidis strains and between Neisseria species was identified in SimPlot analysis. Finally, amino acid substitutions within GyrA protein were analyzed. Only one position, 91 (83 in E.coli gyrA gene), was linked to CIP resistance. Thirty-one additional putative resistance markers were identified, as amino acid substitutions were only found in resistant strains. Conclusions: The evolution of gyrA gene of CC4821 N.meningitidis strains is not dependent on CC4821 evolution or on CIP resistance phenotype. Only amino acid 91 is linked to CIP resistance phenotype. Finally, recombination inter- and intra-species is likely to result in the acquisition of various resistance markers, 31 of them being putatively mapped in the present study. Analyzing the evolution of gyrA gene within CC4821 strains is critical to monitor the CIP resistance phenotype and the acquisition of new resistance markers. Such studies are necessary for the control of the meningococcal disease and the development of new drugs targeting DNA gyrase. [ABSTRACT FROM AUTHOR]

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]

Mercaptoacetic acid-capped CdTe quantum dots (QDs) are potential luminescent markers for biological analysis. The photoluminescence (PL) stability of the QDs in buffer solutions determines their practicability as markers in electrophoresis. The stability of the QDs was thus investigated in electrophoresis buffers including tris-borate-ethylenediaminetetraacetic acid (TBE) and tris-acetate-ethylenediaminetetraacetic acid (TAE). The QDs were completely unstable in high-concentrated buffers (≥0.1×). In the case of low concentrations (≤0.07× for TAE, ≤0.035× for TBE), the PL intensity of the QDs in two kinds of buffers decreased with increasing buffer concentrations. A red-shifted PL peak wavelength and PL intensity fluctuation were observed after dispersing the QDs in diluted TAE buffer solutions with concentrations of ≤0.07× for long time. According to the Stern-Volmer plots of PL degradation, the factors leading to the degradation were complicated, which was attributed to the actions of the components including tris, borate or acetic acid, and ethylenediaminetetraacetic acid as well as their mutual effects. [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]

The synthesis and photoluminescence (PL) properties of aqueous CdTe/ZnO core/shell quantum dots (QDs) have been investigated by using thiolglycolic acid as a capping reagent. The highlighted contribution of the present study was CdTe QDs coated with a ZnO shell by controlling the hydrolysis process of Zn(OAc). The QDs benefitted from overcoming the high lattice mismatch between CdTe and ZnO. The PL peak wavelength of the CdTe/ZnO QDs with high PL quantum yields up to 88% was located in a range between 547 and 596 nm by adjusting the size of CdTe cores and the thickness of ZnO shells. The results of X-ray diffraction analysis and transmission electron microscopy observation indicate that the dot-shaped CdTe/ZnO QDs (566 nm) with an average size of 2.2 nm in diameter belong to the cubic CdTe crystal structure. Due to the passivation of surface defects, it is found that the luminescence decay curves accord with a biexponential decay model of exciton and trap radiation behavior. The average PL lifetimes of CdTe (571 nm) and CdTe/ZnO (596 nm) QDs at room temperature are 27.3 and 35.1 ns, respectively. [ABSTRACT FROM AUTHOR]

Silver particles with various morphologies were prepared by a facile synthesis via the reduction of silver ions in an ethylene glycol solution with poly(vinyl pyrrolidone) (PVP) and trace amounts of sodium chloride. Preparative conditions such as reaction temperature (from 120 to 160 °C), time, and the concentration of starting materials were optimized for the purpose of controlling the morphology of Ag particles. Scanning electron microscopy indicated Ag particles with various morphologies such as rod, cubic, and spherical. The creation of various morphologies was ascribed to the select adsorption ability of PVP and the erosion behavior of the chloride ion. Because of the morphology dependence of the Ag particles on the preparative conditions, this strategy provided a platform for controlling the morphologies of metallic particles. [ABSTRACT FROM AUTHOR]

CdTe quantum dots (QDs) were prepared in an aqueous solution using various mercaptocarboxylic acids, such as 3-mercaptopropionic acid (MPA) and thioglycolic acid (TGA), as stabilizing agents. The experimental result indicated that these stabilizing agents played an important role for the properties of the QDs. Although both TGA and MPA-capped CdTe QDs exhibited the tunable photoluminescence (PL) from green to red color, the TGA-capped QDs revealed a higher PL quantum yield (QY) up to 60% than that of MPA-capped QDs (up to 50%) by using the optimum preparation conditions, such as a pH value of ~11.2 and a TGA/Cd molar ratio of 1.5. PL lifetime measurements indicate that the TGA-capped QDs exhibited a short average lifetime while the MPA-capped QDs revealed a long one. Furthermore, the average lifetime of the TGA-capped QDs increased with the increase of the QDs size, while a decreased lifetime for the MPA-capped QDs was obtained. This means that the PL lifetime depended strongly on the surface state of the CdTe QDs. These results should be utilized for the preparation and applications of QDs. [ABSTRACT FROM AUTHOR]