Dinuclear Lanthanide Compound as a Promising Luminescent Probe for Al3+ Ions.

Luminescent probes have wide applications in biological system analysis and environmental science. Here, one novel luminescent dinuclear europium compound with a crown ether analogous ligand was synthesized through a solvent-thermal reaction. Through transformation, upon the addition of Al3+ ions to the N,N'-dimethyl formamide solution of the europium compound, the luminescent intensity of the characteristic emission of Eu3+ decreased, and a new emission peak appeared at 346 nm and increased rapidly. The luminescent investigation indicated that it could act as a highly sensitive and selective luminescent probe for Al3+ ions. Moreover, mass spectrometry and single-crystal X-ray diffraction confirmed the formation of a new more stable trinuclear aluminium compound during the sensing process.

Metallo-Supramolecular Octahedral Cages with Three Types of Chirality towards Spontaneous Resolution.

Chirality is one of the most important intrinsic properties of (supra)molecules. In this study, we obtained enantiomeric metallo-supramolecular octahedra without using any chiral sources. Such cages were self-assembled by prochiral trispyridine ligand L based on a C3h truxene core and CuII salts. Crystallization of the cages with BF4 - as counterions afforded racemate crystals; while crystallizations of cages with ClO4 - and OTf- as counterions resulted in conglomerates with spontaneous resolution. Three types of chirality were observed in each cage, including planar chirality of the truxene core, axial chirality from the pyridyl and truxene moieties, and propeller chirality of the pyridyl-CuII coordination sites. The cages reported here are among the largest discrete synthetic metallo-supramolecules ever reported with chiral self-sorting behavior. Remarkably, the chiral cages exhibited very slow racemization even at low concentrations, suggesting their high stability in solution.

Photocatalytic Hydrogen Production over Chromium Doped Layered Perovskite Sr2TiO4.

Layered semiconductor photocatalysts have been found to exhibit promising performance levels, probably linked to their interlayer framework that facilitates separation of charge carriers and the reduction/oxidation reactions. Layered titanates, however, generally demonstrate activities under UV irradiation, and therein lies the strong desire to extend their activity into the visible light region. Here, we investigated a series of layered perovskite by doping Sr2TiO4 with Cr and/or La in the hope to improve their visible light responses. Their crystal structures and other physicochemical properties were systematically explored. Our results show that La and Cr can be successfully accommodated in the layered structure and Cr is an efficient dopant for the extension of visible light absorbance. Much enhanced photocatalytic hydrogen evolution was observed after doping and was found to be composition-dependent. The highest hydrogen production rate approaches 97.7 µmol/h for Sr2Ti0.95Cr0.05O4-δ under full range irradiation (λ ≥ 250 nm) and 17 µmol/h for Sr2Ti0.9Cr0.1O4-δ under visible light irradiation (λ ≥ 400 nm), corresponding to an apparent quantum efficiency of 0.16% and 0.05%, respectively. Theoretical calculation reveals that the improved optical and photocatalytic properties are owing to a newly formed spin-polarized valence band from Cr 3d orbitals. The decreased unit cell parameters, reduced band gaps as well as anisotropic properties of layered architectures are likely the reasons for a better activity. Nevertheless, instability of these compounds in the presence of moisture and CO2 was also noticed, suggesting that protective atmospheres are needed for the storage of these photocatalysts.

Bismuth and chromium co-doped strontium titanates and their photocatalytic properties under visible light irradiation.

Modification of prototype perovskite compound SrTiO3 by introducing foreign elements has been an appealing means to endow this wide band gap semiconductor with visible light responses. Here we systematically investigated a series of Sr1-xBixTi1-xCrxO3 solid solution compounds prepared by two different synthetic routes, namely, solid state reactions and the hydrothermal method. Their crystal structures as well as other physicochemical properties were explored. Our results showed that a number of important factors such as microstructures, crystallinity, light absorbance and surface compositions etc. are all strongly correlated with the synthetic methods used. The hydrothermal method is generally helpful for morphology controls as well as avoiding Cr(6+) defects and Sr segregation at the surface, thereby contributing to a high photocatalytic activity. Better performance normally occurs in samples with a high crystallinity and free of defects like Bi(5+). Theoretical calculations suggest that Cr plays an important role in band gap reduction and photocatalytic reactions, while Bi only acts as a constituent cation for the perovskite structure and does not significantly alter the electronic structures near the Fermi level. Our findings have revealed how synthetic routes are relevant to the final photocatalytic properties of a compound, and therefore comparisons among various photocatalysts have to include concerns about their preparation history.

Trends of mean systolic and diastolic blood pressure among adults in Shenzhen, China, 1997-2018: findings from three rounds of the population-based survey.

OBJECTIVE: To quantify the trends in systolic and diastolic blood pressure (BP) among adults in Shenzhen from 1997 to 2018. DESIGN: Cross-sectional study. SETTINGS: The data were collected from all districts in Shenzhen, China in the years of 1997, 2009 and 2018 by multistage cluster sampling procedure. PARTICIPANTS: Participants were residents aged 18-69 years in Shenzhen, China. A total of 26 621 people were included: 8266 people in 1997, 8599 people in 2009 and 9756 people in 2018. PRIMARY AND SECONDARY OUTCOME MEASURES: All participants were surveyed about their sociodemographic and lifestyle information. BP was measured by trained physicians using a mercury sphygmomanometer. Hypertension was defined as systolic BP of at least 140 mm Hg and diastolic BP of at least 90 mm Hg, self-reported use of antihypertensive medications or both. Hypertension control was defined as systolic BP values of less than 140 mm Hg and diastolic BP values of less than 90 mm Hg. RESULT: Age-adjusted mean systolic BP increased from 117±16 mm Hg to 123±15 mm Hg (p<0.001) in males, and from 113±18 mm Hg to 115±16 mm Hg (p<0.001) in females from 1997 to 2018. Diastolic BP among males increased from 75 mm Hg (SD=11) to 79 mm Hg (SD=11) and increased from 71 mm Hg (SD=10) to 73 mm Hg (SD=10) among females between 1997 and 2018 (p<0.001). Rate of hypertension rose rapidly from 17.71% (95% CI: 16.60% to 18.90%) in 2009 to 24.01% (95% CI: 22.84% to 25.22%) in 2018 among males (p<0.001), whereas the prevalence among females remained stable at around 13.5% (p=0.98). Both awareness and treatment rates of hypertension among males and females showed a decreased trend between 2009 and 2018, while no significant changes were observed for control rates. CONCLUSIONS: The mean systolic BP and diastolic BP among adults in Shenzhen increased from 1997 to 2018, and no improvements in hypertension awareness, treatment and control rates were found.

Role of Oxygen Defects on the Photocatalytic Properties of Mg-Doped Mesoporous Ta3 N5.

Tantalum nitride (Ta3 N5 ) highlights an intriguing paradigm for converting solar energy into chemical fuels. However, its photocatalytic properties are strongly governed by various intrinsic/extrinsic defects. In this work, we successfully prepared a series of Mg-doped mesoporous Ta3 N5 using a simple method. The photocatalytic and photoelectrochemical properties were investigated from the viewpoint of how defects such as accumulation of oxygen and nitrogen vacancies contribute to the catalytic activity. Our findings suggest that Mg doping is accompanied by an accumulation of oxygen species and a simultaneous elimination of nitrogen vacancies in Ta3 N5 . These oxygen species in Ta3 N5 induce delocalized shallow donor states near the conduction band minimum and are responsible for high electron mobility. The superior photocatalytic activity of Mg-doped Ta3 N5 can then be understood by the improved electron-hole separation as well as the lack of nitrogen vacancies, which often serve as charge-recombination centers.

Quinary wurtzite Zn-Ga-Ge-N-O solid solutions and their photocatalytic properties under visible light irradiation.

Wurtzite solid solutions between GaN and ZnO highlight an intriguing paradigm for water splitting into hydrogen and oxygen using solar energy. However, large composition discrepancy often occurs inside the compound owing to the volatile nature of Zn, thereby prescribing rigorous terms on synthetic conditions. Here we demonstrate the merits of constituting quinary Zn-Ga-Ge-N-O solid solutions by introducing Ge into the wurtzite framework. The presence of Ge not only mitigates the vaporization of Zn but also strongly promotes particle crystallization. Synthetic details for these quinary compounds were systematically explored and their photocatalytic properties were thoroughly investigated. Proper starting molar ratios of Zn/Ga/Ge are of primary importance for single phase formation, high particle crystallinity and good photocatalytic performance. Efficient photocatalytic hydrogen and oxygen production from water were achieved for these quinary solid solutions which is strongly correlated with Ge content in the structure. Apparent quantum efficiency for optimized sample approaches 1.01% for hydrogen production and 1.14% for oxygen production. Theoretical calculation reveals the critical role of Zn for the band gap reduction in these solid solutions and their superior photocatalytic acitivity can be understood by the preservation of Zn in the structure as well as a good crystallinity after introducing Ge.

Efficient charge separation based on type-II g-C3N4/TiO2-B nanowire/tube heterostructure photocatalysts.

Separation of photo-generated charges has played a crucial role in controlling the actual performance of a photocatalytic system. Here we have successfully fabricated g-C3N4/TiO2-B nanowire/tube heterostructures through facile urea degradation reactions. Owing to the effective separation of photo-generated charges associated with the type-II band alignment and intimate interfacial contacts between g-C3N4 and TiO2-B nanowires/tubes, such heterostructures demonstrate an improved photocatalytic activity over individual moieties. Synthetic conditions such as hydrothermal temperatures for the preparation of TiO2-B and the weight ratio of TiO2-B to urea were systematically investigated. A high crystallinity of TiO2-B as well as the proper growth of g-C3N4 on its surface are critical factors for a better performance. Our simple synthetic method and the prolonged lifetime of photo-generated charges signify the importance of type-II heterostructures in the photocatalytic applications.