Silver cluster-assembled materials (SCAMs), by virtue of their tunable structure, accessible surface area and excellent stability, hold great promise as highly efficient catalysts. Herein, we report ...a new SCAM Ag12(S t Bu)6(CF3COO)3(TPyP) n (denoted as Ag12TPyP) composed of a Ag12 chalcogenolate cluster core stabilized by porphyrinic ligands. Ag12TPyP showed superior sulfur mustard simulant (2-chloroethyl ethyl sulfide, CEES) degradation efficiency and achieved a half lifetime (t 1/2) of 1.5 min with 100% selectivity. The experimental results demonstrated that synergistic effects between the silver cluster and photosensitizer ligand promote the efficiency of the generation of singlet oxygen (1O2), which accelerates the decontamination rate. Additionally, benefiting from strong affinity between the silver cluster and CEES, Ag12TPyP exhibits a CEES uptake of 74.2 mg g–1. This work demonstrates that SCAMs offer a new route to the rational design of novel materials for the detoxification of mustard gas.
Recently, research on metal–organic frameworks (MOFs) serving as a new type of proton conductive material has resulted in many exciting achievements. However, direct observation of a well-established ...proton-transfer mechanism still remains challenging in MOFs and other crystalline compounds, let alone other conductive materials. Herein we report the solvothermal synthesis of a new proton-conducting MOF, (Me2NH2)Eu(L) (H4L = 5-(phosphonomethyl)isophthalic acid). The compound consists of a layered anionic framework Eu(L)− and interlayer-embedded counter cations (Me2NH2)+, which interact with adjacent uncoordinated O atoms of phosphonate groups to form strongly (N–H···O) hydrogen-bonded chains aligned parallel to the c-axis. Facile proton transfer along these chains endows the compound with single-crystal anhydrous conductivity of 1.25 × 10–3 S·cm–1 at 150 °C, and water-assisted proton conductivity for a compacted pellet of microcrystalline crystals attains 3.76 × 10–3 S·cm–1 at 100 °C and 98% relative humidity (RH). Proton dynamics (vibrating and transfer) within N–H···O chains of the compound are directly observed using a combination of anisotropic conductivity measurements and control experiments using large single-crystals and pelletized samples, in situ variable-temperature characterization techniques including powder X-ray diffraction (PXRD), single-crystal X-ray diffraction (SCXRD), diffuse reflectance infrared Fourier transform spectrum (DRIFTS), and variable-temperature photoluminescence. In particular, a scarce single-crystal to single-crystal (SCSC) transformation accompanied by proton transfer between an anionic structure (Me2NH 2)Eu(L) and an identical neutral framework Eu(HL) has been identified.
Convenient generation of stable superatomic silver clusters and their systematic site-specific tailoring and directional assembly present an enduring and significant challenge. In this work, we ...prepared a face-centered cubic (fcc) array of Ag14 superatoms protected by face-capping 1,2-dithiolate-o-carborane (C2B10H10S2) ligands, each produced from 1-thiol-o-carborane in crystallization with simultaneous reduction of Ag+ to Ag0. We find that the corner N-donor ligands contribute predominately to the stability and luminescence of the Ag14 superatom. As the first-formed nanocluster Ag14(C2B10H10S2)6(CH3CN)8·4CH3CN (NC-1) with labile vertex-coordinated CH3CN ligands is highly unstable, monodendate pyridine ligands were used to replace these CH3CN species site-specifically, giving Ag14(C2B10H10S2)6(pyridine/p-methylpyridine)8 (NCs-2,3) in gram scale with its core structure intact, which features ultrastability up to 150 °C in air. Moreover, using bidentate N-containing ligands to bridge the superatomic Ag14 building blocks, we constructed an unprecedented hierarchical series of 1D-to-3D superatomic silver cluster-assembled materials (SCAM-1,2,3,4), and SCAM-4 is air-stable up to 220 °C. Furthermore, this series of stable solid-state superatomic-nanocluster materials exhibit tunable dual emission with wide-range thermochromism. The present study constitutes a major step toward the development of ligand-modulation of the structure, stability, assembly, and functionality of superatomic silver nanoclusters.
We report a new enantiomeric pair of superatomic silver clusters, R/S-Ag 17 , prepared from chiral alkynyl ligands. R-Ag 17 and S-Ag 17 possess C 3 symmetry and emit near-infrared (NIR) light with a ...quantum yield (QY) of 8.0% under ambient condition as well as NIR circularly polarized luminescence (CPL) as a result of the chirality of the excited states. Both experiments and theoretical calculations indicate for the first time that the CPL originates from transitions between superatomic 1P z (along the C 3 axis) and 1S orbitals. This work opens a new avenue for CPL-active metal nanoclusters by utilizing chiral alkynyl ligands and enlightens the chirality transfer from chiral protecting ligands to superatomic states in metal clusters.
Abstract
Ratiometric luminescent oxygen sensing based on dual fluorescence and phosphorescence emission in a single matrix is highly desirable, yet the designed synthesis remains challenging. ...Silver-chalcogenolate-cluster-based metal-organic frameworks that combine the advantages of silver clusters and metal-organic frameworks have displayed unique luminescent properties. Herein, we rationally introduce −NH
2
groups on the linkers of a silver-chalcogenolate-cluster-based metal-organic framework (Ag
12
bpy-NH
2
) to tune the intersystem crossing, achieving a dual fluorescence-phosphorescence emission from the same linker chromophore. The blue fluorescence component has a 100-nm gap in wavelength and 8,500,000-fold difference in lifetime relative to a yellow phosphorescence component. Ag
12
bpy-NH
2
quantifies oxygen during hypoxia with the limit of detection of as low as 0.1 ppm and 0.3 s response time, which is visualized by the naked eye. Our work shows that metal cluster-based MOFs have great potential in luminescent sensing, and the longer-lived charge-separated states could find more photofunctional applications in solar energy transformation and photocatalysis.
A street canyon is an important platform for the understanding of local atmospheric flow and other related processes in the built environment. Many previous studies focused on long street canyons ...under a perpendicular wind direction, as they represent the worst street canyon microclimate, such as stagnation of wind and accumulation of pollutants. While CFD simulations were widely applied to investigate atmospheric processes in street canyons, appropriate computational settings are important factors influencing the predictive reliability. A non-exhaustive literature review of CFD studies on atmospheric processes in long street canyons indicates an arbitrary selection of three important computational settings, namely computational domain configuration, domain dimensions and inflow boundary conditions. Based on previous water tunnel experimental data for street canyons with aspect ratio equal to 0.5, 1.0 and 2.0, this study evaluates the influence of the three computational settings on CFD prediction of isothermal flow field inside the street canyons. Flow field inside an urban street canyon cannot be reasonably predicted using an isolated street canyon included in a conventional computational domain, which, however, can be well predicted using a T-shape computational domain where a street canyon is connected to a free flow layer above the canyon. A T-shape domain with the upstream length, downstream length and height above a street canyon all equal to the height of the street canyon is appropriate when considering both computational cost and predictive accuracy. It is reasonable to use uniform inflow boundary conditions to represent the free layer above street canyons.
•Three sets of water tunnel experimental data used to support below evaluations.•Computational domain configurations evaluated and T-shape domain suggested.•Computational domain dimensions evaluated and appropriate values suggested.•Inflow boundary conditions evaluated and uniform inflow conditions suggested.•Above evaluations made based on three aspect ratios, namely 0.5, 1.0 and 2.0.
Background
Vitamin D and related compounds have been used to prevent osteoporotic fractures in older people. This is the third update of a Cochrane review first published in 1996.
Objectives
To ...determine the effects of vitamin D or related compounds, with or without calcium, for preventing fractures in post‐menopausal women and older men.
Search methods
We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (to December 2012), the Cochrane Central Register of Controlled Trials (2012, Issue 12), MEDLINE (1966 to November Week 3 2012), EMBASE (1980 to 2012 Week 50), CINAHL (1982 to December 2012), BIOSIS (1985 to 3 January 2013), Current Controlled Trials (December 2012) and reference lists of articles.
Selection criteria
Randomised or quasi‐randomised trials that compared vitamin D or related compounds, alone or with calcium, against placebo, no intervention or calcium alone, and that reported fracture outcomes in older people. The primary outcome was hip fracture.
Data collection and analysis
Two authors independently assessed trial risk of selection bias and aspects of methodological quality, and extracted data. Data were pooled, where possible, using the fixed‐effect model, or the random‐effects model when heterogeneity between studies appeared substantial.
Main results
We included 53 trials with a total of 91,791 participants. Thirty‐one trials, with sample sizes ranging from 70 to 36,282 participants, examined vitamin D (including 25‐hydroxy vitamin D) with or without calcium in the prevention of fractures in community, nursing home or hospital inpatient populations. Twelve of these 31 trials had participants with a mean or median age of 80 years or over.
Another group of 22 smaller trials examined calcitriol or alfacalcidol (1‐alphahydroxyvitamin D3), mostly with participants who had established osteoporosis. These trials were carried out in the setting of institutional referral clinics or hospitals.
In the assessment of risk of bias for random sequence generation, 21 trials (40%) were deemed to be at low risk, 28 trials (53%) at unclear risk and four trials at high risk (8%). For allocation concealment, 22 trials were at low risk (42%), 29 trials were at unclear risk (55%) and two trials were at high risk (4%).
There is high quality evidence that vitamin D alone, in the formats and doses tested, is unlikely to be effective in preventing hip fracture (11 trials, 27,693 participants; risk ratio (RR) 1.12, 95% confidence intervals (CI) 0.98 to 1.29) or any new fracture (15 trials, 28,271 participants; RR 1.03, 95% CI 0.96 to 1.11).
There is high quality evidence that vitamin D plus calcium results in a small reduction in hip fracture risk (nine trials, 49,853 participants; RR 0.84, 95% confidence interval (CI) 0.74 to 0.96; P value 0.01). In low‐risk populations (residents in the community: with an estimated eight hip fractures per 1000 per year), this equates to one fewer hip fracture per 1000 older adults per year (95% CI 0 to 2). In high risk populations (residents in institutions: with an estimated 54 hip fractures per 1000 per year), this equates to nine fewer hip fractures per 1000 older adults per year (95% CI 2 to 14).
There is high quality evidence that vitamin D plus calcium is associated with a statistically significant reduction in incidence of new non‐vertebral fractures. However, there is only moderate quality evidence of an absence of a statistically significant preventive effect on clinical vertebral fractures. There is high quality evidence that vitamin D plus calcium reduces the risk of any type of fracture (10 trials, 49,976 participants; RR 0.95, 95% CI 0.90 to 0.99).
In terms of the results for adverse effects: mortality was not adversely affected by either vitamin D or vitamin D plus calcium supplementation (29 trials, 71,032 participants, RR 0.97, 95% CI 0.93 to 1.01). Hypercalcaemia, which was usually mild (2.6 to 2.8 mmol/L), was more common in people receiving vitamin D or an analogue, with or without calcium (21 trials, 17,124 participants, RR 2.28, 95% CI 1.57 to 3.31), especially for calcitriol (four trials, 988 participants, RR 4.41, 95% CI 2.14 to 9.09), than in people receiving placebo or control. There was also a small increased risk of gastrointestinal symptoms (15 trials, 47,761 participants, RR 1.04, 95% CI 1.00 to 1.08), especially for calcium plus vitamin D (four trials, 40,524 participants, RR 1.05, 95% CI 1.01 to 1.09), and a significant increase in renal disease (11 trials, 46,548 participants, RR 1.16, 95% CI 1.02 to 1.33). Other systematic reviews have found an increased association of myocardial infarction with supplemental calcium; and evidence of increased myocardial infarction and stroke, but decreased cancer, with supplemental calcium plus vitamin D, without an overall effect on mortality.
Authors' conclusions
Vitamin D alone is unlikely to prevent fractures in the doses and formulations tested so far in older people. Supplements of vitamin D and calcium may prevent hip or any type of fracture. There was a small but significant increase in gastrointestinal symptoms and renal disease associated with vitamin D and calcium. This review found that there was no increased risk of death from taking calcium and vitamin D.
In this paper, we review and provide additional details about our progress on multilayer silicon nitride (SiN)-on-silicon (Si) integrated photonic platforms. In these platforms, one or more SiN ...waveguide layers are monolithically integrated onto a Si photonic layer. This paper focuses on the development of three-layer platforms for the O- and SCL-bands for very large-scale photonic integrated circuits requiring hundreds or thousands of waveguide crossings. Low-loss interlayer transitions and ultralow-loss waveguide crossings have been demonstrated, along with bilevel and trilevel grating couplers for fiber-to-chip coupling. The SiN and Si passive devices have been monolithically integrated with high-efficiency optical modulators, photodetectors, and thermal tuners in a single photonic platform.
Abstract
Visible and near-infrared spectrum photonic integrated circuits are quickly becoming a key technology to address the scaling challenges in quantum information and biosensing. Thus far, ...integrated photonic platforms in this spectral range have lacked integrated photodetectors. Here, we report silicon nitride-on-silicon waveguide photodetectors that are monolithically integrated in a visible light photonic platform on silicon. Owing to a leaky-wave silicon nitride-on-silicon design, the devices achieved a high external quantum efficiency of >60% across a record wavelength span from
λ
~ 400 nm to ~640 nm, an opto-electronic bandwidth up to 9 GHz, and an avalanche gain-bandwidth product up to 173 ± 30 GHz. As an example, a photodetector was integrated with a wavelength-tunable microring in a single chip for on-chip power monitoring.
A questionnaire survey was conducted to investigate the effects of daylighting and human behavior patterns on subjective luminous comfort in Hong Kong housing units. The participants were recruited ...via mail, and included residents of both public and private housing units. 340 questionnaires were returned and analyzed by using SPSS 19.0. In analyzing the response statistics, the Cronbach's alpha coefficient, Spearman rank correlation coefficient, Chi-square test, Kruskal–Wallis test and stepwise regression were adopted to identify the effects of particular aspects of human behavior and daylighting quality. The results confirmed that luminous comfort is a function of both behavior patterns and daylighting conditions. Behavior factors have a significant influence on luminous comfort among people who grade their satisfaction with daylighting as moderate. In general, the degree of luminous comfort is most affected by satisfaction with daylighting. External obstruction is the major physical factor affecting luminous comfort, while the perception of uniformity is the major factor of residents' feelings toward daylight. The use of artificial lighting is the most relevant behavior factor affecting luminous comfort, as using artificial lighting for many hours per day indicates poor daylighting conditions and decreased luminous comfort. These results should help to raise awareness of the detailed factors that influence the luminous environment. Our findings may also assist planners and architects to implement better daylighting for housing projects and provide residents with greater luminous comfort.
•Luminous comfort was surveyed in both public and private housing in Hong Kong.•Non-parametric tests were adopted to identify factors' effects on luminous comfort.•Uniformity and obstruction are the main factors to the satisfaction of daylighting.•The degree of luminous comfort is most affected by satisfaction with daylighting.•Long usage time of artificial lighting decreases the luminous comfort.
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