Investigation into covalent triazine frameworks for high efficiency visible-light driven water splitting

Efficient utilisation of solar energy could alleviate major energy and the related environmental issues. The conversion of solar energy into chemical fuels by artificial photosynthesis has thus received much attention, e.g. production of renewable hydrogen from water. Since the first photoelectrode titanium dioxide was found for photoelectrochemical water splitting in 1972, substantial progress on semiconducting materials for photocatalytic water splitting has been made. Specifically, to utilise sunlight efficiently, developing visible-light-responsive photocatalysts is indispensable to realise the application of solar-to-chemical energy conversion in practice. Considering few overall water splitting systems reported, investigation on the oxidative and the reductive half reactions separately is significant for fundamental understanding, optimisations and finally complete water-splitting cycles. Among these photocatalysts, inorganic photocatalysts have been widely explored for the hydrogen evolution reaction. However, most of them are either only active under UV light irradiation or their efficiency is moderate, due to either large band gap energy or fast charge recombination. In the past few years, the increasing interest in a class of metal-free organic photocatalysts for water splitting has been raised, as these organic polymers feature twodimensional (2D) conjugated structures, high chemical stability, ease of modification to achieve suitable thermodynamical potentials to overall water splitting. The most common metal-free organic photocatalyst is melon-based graphitic carbon nitride (for simplicity, usually denoted gC3N4). Moreover, a series of covalent triazine frameworks (CTFs) were synthesised recently. These materials were formed by the ionothermal trimerization of aromatic nitriles in molten ZnCl2 and built up by alternating triazine and phenyl building blocks. Because of the covalent triazine-based structure, CTFs possess excellent thermal and chemical stability, beneficial as new catalysts in liquid phase reactions. CTFs with the π-stacked aromatic units would also be expected to promote exciton separation and charge transportation, promising for photocatalytic lightdriven water splitting. As such, the research project targets on visible light-driven CTF photocatalysts for pure water splitting. Firstly, the photooxidation of water using oxygen doped CTF-1(OCT) was investigated. The OCT was created by a simple dynamic trimerization reaction of the precursor 1,4-dicyanobenzene in ionothermal conditions, that is, in molten zinc chloride at high temperature. It was found that due to the oxygen-containing reaction atmosphere, some oxygen was doped in the crystals to modify the structure, optical, and electrical properties of the materials, resulting in the much better operation window (from UV to NIR) than the benchmark photooxidation catalyst BiVO4 (only active from UV to 500 nm). The external quantum efficiency of OCT was determined to be 2.6% at the wavelength of 400 nm, 1.5% at 500 nm, even ~0.2% at wavelength as long as 800 nm. Structure optimization, thermodynamic calculation and electronic structure analysis of OCT calculated by density functional theory (DFT) were carried out to illustrate the mechanism of the increasing photooxidation yield successfully, which could be applied to improve other semiconductors. Furthermore, hydrogen and oxygen evolutions from water were carried out by another polymer photocatalyst CTF-0, which is one member of the CTFs group and based on 1,3,5-tricyanobenzene as monomer under ionothermal conditions. Compared with OCT, CTF-0 crystals have higher nitrogen ratio and smaller pore size. Herein, two different synthesis ways of a novel photocatalyst covalent triazine framework CTF-0 were utilised and tested for photocatalytic H2 and O2 evolution under visible light irradiation. The CTF-0-M2 produced by a microwave method shows an almost 7 times higher photocatalytic activity of hydrogen evolution (up to 701 µmol/h) than the CTF-0-I produced by an ionothermal trimerization method under similar photocatalytic conditions, which leads to an extremely high turnover number (TON) of 726 over a platinum cocatalyst after seven circles. This can be attributed to the narrow band gap and the rapid photogenerated charge separation and transportation. Whereas, CTF-0-I has produced rough 6 times higher oxygen of 22.6 µmol in the first hour than CTF-0-M2 under the same experimental condition. A high apparent quantum efficiency (AQY) of 7.2% at 420 nm for oxygen production was obtained from aqueous AgNO3 solution without any cocatalysts, exceeding most of the reported CTFs, due to the large driving force of water oxidation and the large number of active sites. Finally, considering that the CTF-0 has a wide bandgap, which could produce both hydrogen and oxygen theoretically, decorating the different co-catalysts on the CTF-0 was explored for the entire water splitting to produce hydrogen and oxygen. The presence of the cocatalyst Pt and Co3O4 promotes the H2 and O2 evolution on the surface of the photocatalysts simultaneously, due to enhanced separation of photogenerated charge carriers, more active sites for catalytic H2 and O2 evolution and the improved stability by suppressing photo-corrosion. Loading different ratio of cobalt cocatalysts on CTF-0 has been explored for overall water splitting. And it is found that water splitting rates are influenced by the concentration of the cocatalyst. 6 wt% Co3O4 and 3wt% Pt-deposited CTF-0 shows the best photocatalytic performances of 0.82 μmol/h H2 and 0.42 μmol/h O2, nearly close to the stoichiometric H2/O2 ratio of 2:1. Whereas, the system didn’t work under the visible light but UV light irradiation, which might be because of the limitation of light absorption range and the efficiency of the charged carriers. Further work is required to confirm the factors and mechanism of the pure water splitting of CTF-0s

Rejoinder: Quantifying the Fraction of Missing Information for Hypothesis Testing in Statistical and Genetic Studies

Rejoinder to "Quantifying the Fraction of Missing Information for Hypothesis Testing in Statistical and Genetic Studies" [arXiv:1102.2774]Comment: Published in at http://dx.doi.org/10.1214/08-STS244REJ the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Quantifying the Fraction of Missing Information for Hypothesis Testing in Statistical and Genetic Studies

Many practical studies rely on hypothesis testing procedures applied to data sets with missing information. An important part of the analysis is to determine the impact of the missing data on the performance of the test, and this can be done by properly quantifying the relative (to complete data) amount of available information. The problem is directly motivated by applications to studies, such as linkage analyses and haplotype-based association projects, designed to identify genetic contributions to complex diseases. In the genetic studies the relative information measures are needed for the experimental design, technology comparison, interpretation of the data, and for understanding the behavior of some of the inference tools. The central difficulties in constructing such information measures arise from the multiple, and sometimes conflicting, aims in practice. For large samples, we show that a satisfactory, likelihood-based general solution exists by using appropriate forms of the relative Kullback--Leibler information, and that the proposed measures are computationally inexpensive given the maximized likelihoods with the observed data. Two measures are introduced, under the null and alternative hypothesis respectively. We exemplify the measures on data coming from mapping studies on the inflammatory bowel disease and diabetes. For small-sample problems, which appear rather frequently in practice and sometimes in disguised forms (e.g., measuring individual contributions to a large study), the robust Bayesian approach holds great promise, though the choice of a general-purpose "default prior" is a very challenging problem.Comment: Published in at http://dx.doi.org/10.1214/07-STS244 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Reciprocity in a Two-Part Dictator Game

We conduct a dictator game experiment in which recipients in an initial game become dictators in a second game. When the subjects paired remain the same, the amount sent back is strongly correlated with the amount received, despite the fact that the interaction is anonymous and is known to be one-time and zero-sum in nature. When the initial recipient is instead paired with a third subject, a less significant and lower-valued correlation between amounts received and sent is exhibited. Intelligence and personality test results, gender, and other characteristics also help to predict sending behavior and degree of reciprocity.reciprocity, dictator game, cognition, personality, altruism

Efficacy and prognostic factors of concurrent chemoradiotherapy in patients with stage Ib3 and IIa2 cervical cancer

Objectives: We investigated the efficacy, side effects, and prognostic factors of concurrent chemoradiotherapy for patientswith stage Ib3-IIa2 cervical cancer.Material and methods: We conducted a retrospective analysis of clinicopathologic data from 73 patients with stageIb3-IIa2 cervical cancer who received concurrent chemoradiotherapy from January 2008 to December 2013 in our hospital.Overall response and disease control rates were used to evaluate short-term outcomes; the 3-year and 5-year disease-freesurvival and overall survival were used to evaluate long-term efficacy. Toxicity reactions and prognostic factors were recorded.Results: With concurrent chemoradiotherapy, overall response and disease control rates were 91.78% and 97.26%, respectively.The 3-year disease-free and overall survival were 80.82% and 83.56%; the 5-year disease-free and overall survival were 75.34%and 79.45%, respectively. All side effects were tolerated and potentially alleviated by symptomatic treatment. Tumor pathologicaltype, differentiated degree, primary tumor size and squamous cell carcinoma antigen levels before and after treatment wereclosely related to survival (univariate analysis; p < 0.05). Pathological type, primary tumor size and squamous cell carcinomaantigen levels one month after treatment were independent prognostic factors for long-term outcome (multivariate analysis).Conclusions: Short- and long-term efficacy of concurrent chemoradiotherapy for stage Ib3-IIa2 cervical cancer is well-determinedand tolerable. Patients with adenocarcinomas, tumor diameter ≥ 5 cm and squamous cell carcinoma antigenlevels ≥ 1.5 ng/mL (one month after treatment) had poor prognosis and should be assessed further

Tension fracture behaviors of welded joints in X70 steel pipeline

AbstractThe surface of welded joints in X70 steel pipeline was processed by laser shock wave, its mechanical behaviors of tension fracture were analyzed with tension test, and the fracture morphologies and the distributions of chemical element were observed with scanning electron microscope and energy dispersive spectrum, respectively. The experimental results show that the phenomenon of grain refinement occurs in the surface of welded joints in X70 steel pipeline after the laser shock processing, and compressive residual stress is formed in its surface strengthened layer. There is no yield stage but a continuous yield behavior in the welded joints in X70 steel pipeline after the laser shock processing, and its extensibility has decreased by 20 %. The welded joints in X70 steel pipeline in primitive state exhibits brittle fracture with less tearing edges, while the fracture of welded joints in X70 steel pipeline processed by laser shock is ductile fracture with a lot of tearing edges

Possible molecular states from interactions of charmed baryons

In this work, we perform a systematic study of possible molecular states composed of two charmed baryons including hidden-charm systems $\Lambda_c\bar{\Lambda}_c$, $\Sigma_c^{(*)}\bar{\Sigma}_c^{(*)}$, and $\Lambda_c\bar{\Sigma}_c^{(*)}$, and corresponding double-charm systems $\Lambda_c\Lambda_c$, $\Sigma_c^{(*)}\Sigma_c^{(*)}$, and $\Lambda_c\Sigma_c^{(*)}$. With the help of the heavy quark chiral effective Lagrangians, the interactions are described with $\pi$, $\rho$, $\eta$, $\omega$, $\phi$, and $\sigma$ exchanges. The potential kernels are constructed, and inserted into the quasipotential Bethe-Salpeter equation. The bound states from the interactions considered is studied by searching for the poles of the scattering amplitude. The results suggest that strong attractions exist in both hidden-charm and double-charm systems considered in the current work, and bound states can be produced in most of the systems. More experiment studies about these molecular states are suggested though the nucleon-nucleon collison at LHC and nucleon-antinucleon collison at $\rm \bar{P}ANDA$.Comment: 7 pages, 5 figure