7,14-Diaryl-Substituted Zethrene Diimides as Stable Far-Red Dyes with Tunable Photophysical Properties

Synthesis and physical characterizations of a series of 7,14-diaryl-substituted zethrene diimides (ZDIs) bearing different substituents (alkyl chain, oligoethyleneglycol ether chain, and aryl group) at the imide sites as well as at the bay regions are described in this study. The synthesis takes advantage of Pd-catalyzed cyclodimerization reaction that allows construction of zethrene core and substitution at the bay region in one single step. The partially cyclized ZDI is also separated as a minor product. The carboxylic acid group is introduced to the bay region for the purpose of further bioconjugation. The photophysical properties, electrochemical properties, and photostability of these ZDI dyes are investigated with UV/vis spectroscopic measurements, cyclic voltammetry measurements, and photoirradiation tests. These dyes exhibit tunable photophysical properties in the far-red spectral region with moderate fluorescent quantum yields and good stability. The enhanced stability as compared to the parent zethrene and the 7,14-substituted zethrenes can be attributed to the electron-withdrawing effect of the imide groups and the kinetic blocking of the most reactive sites at the bay region

Distortion Correction for a Brewster Angle Microscope Using an Optical Grating

A distortion-corrected Brewster angle microscope (DC-BAM) is designed, constructed, and tested based on the combination of an optical grating and a relay lens. Avoiding the drawbacks of most conventional BAM instruments, this configuration corrects the image propagation direction and consequently provides an image in focus over the entire field of view without any beam scanning or imaging reconstruction. This new BAM can be applied to both liquid and solid subphases with good spatial resolution in static and dynamic studies

Kinetics of Iodine-Free Redox Shuttles in Dye-Sensitized Solar Cells: Interfacial Recombination and Dye Regeneration

ConspectusDye-sensitized solar cells (DSCs) have gained widespread attentions owing to their low production cost, tunable optical response, and high light-to-electricity conversion. In DSCs, the performance of redox mediators with iodide/triiodide or iodine-free redox couples is vital to internal quantum efficiency. For a long time, iodide/triiodide based electrolytes are the most widely used mediators because of their desirable kinetics. Recently, exciting progress has been made with respect to iodine-free metallorganic and pure organic redox shuttles. Their tunable redox potential and diverse electron transfer behaviors enable the rational screening of electrolyte composition for enhancing the light-to-electricity conversion efficiency of DSCs toward the Shockley–Queisser limit.In this Account, we emphasize on current knowledge of two distinct but interrelated interfacial processes (electron recombination and dye regeneration), particularly for DSCs with iodine-free redox couples. We show that a deeper understanding of electron transfer kinetics of the alternative redox couples is fundamental to develop rational strategies for cell optimization. Compared with iodine electrolyte, iodine-free metallorganic redox couples such as iron, cobalt, and nickel complexes display much faster electron transfer kinetics in dye regeneration and interfacial recombination. Evidently, rapid regeneration enables the employment of more positive metal complex for attaining a higher photovoltage. However, severe recombination reactions have to be well controlled by using several effective surface treatments such as the addition of Brönsted bases and atomic layer deposition. Although these methods offer different pathways in surface passivation, a trade-off between charge injection efficiency and electron diffusion length is always observed. It follows that an appropriate LUMO level of sensitizer is essential to ensure efficient electron injection at the passivated TiO₂ surface. Apart from fast recombination behavior, bulky metal complexes suffer from inefficient charge transport. Thus, the combination of thinner TiO₂ film and sensitizers with high mole extinction coefficient has been employed for both enhancing diffusion-limited current and maintaining light-harvesting efficiency. Unlike metal complexes, most of organic sulfur redox couples in DSCs exhibit slow recombination kinetics. This allows the use of thicker TiO₂ film to achieve an optimized light harvesting. However, the concomitant sluggish behavior of dye regeneration requires the use of sensitizers with more positive HOMO level, which is beneficial to efficient regeneration. Moreover, lower level of TiO₂ band edge in DSCs based on organic sulfur mediators hinders the achievement of desirable photovoltage, spurring future explorations on this class of redox mediator.Based on the comparison of electron transfer behavior between iodine-free metallorganic complexes and pure organic redox couples, we aim to provide a comprehensive Account of the intriguing interfacial processes in iodine-free DSCs as the key scientific point is linked with the kinetics of interfacial reactions. This demonstrates the advantages as well as disadvantages of each class of iodine-free electrolyte and should shed light on to judicious selection of the energy levels for redox mediators, sensitizers, and the conduction band of TiO₂ for DSCs. The knowledge of the reaction kinetics in DSCs should be also beneficial to the interface engineering on recent developed perovskite cells

Evaluating temporally decomposed associations between PM2.5 and hospitalisation risks of AECOPD: A case study in Beijing from 2010 to 2019

 Few studies investigated relative contributions of PM2.5 concentration at multiple time-scales (short-term, seasonal and long-term periods) on the hospitalisation risk for acute exacerbation of COPD (AECOPD). In this study, we specified and discriminated the short-term, seasonal and long-term trend effects of PM2.5 concentration on the hospitalisation for AECOPD in Beijing between 2010 and 2019. Daily PM2.5 observations from US Beijing Embassy from Jan 1, 2010, to Dec 31, 2019 (3652 days) were decomposed to short-term, seasonal and long-term trend components by using the robust Kolmogorov-Zurbenko filter. During the study period, daily counts of AECOPD hospitalisation were obtained from a database compiled by Beijing Public Health Information Center. Two separate generalized additive models were built to assess effects of raw PM2.5 concentrations and the three decomposed components of time-scales on hospitalisation of AECOPD in Beijing. We found raw PM2.5 concentrations were associated with AECOPD in Beijing with a 10 μg/m3 increase corresponding to 0.46% (95% CI: 0.40%–0.52%) increase in hospitalisation. In the model of decomposed PM2.5 time-series, both the short-term and long-term components exhibited statistically significant positive association with AECOPD, which, respectively, was associated to 0.42% (95% CI: 0.36%–0.48%) and 6.91% (95% CI: 6.08%–7.74%) increase in AECOPD hospitalisation per 10 μg/m3 increase. The seasonal trend had an insignificant U-shaped relationship with AECOPD. Our study simultaneously confirmed that a statistically significant positive association between the raw PM2.5 concentrations, the decomposed short-term and long-term trend of PM2.5 concentrations and increased risk for AECOPD hospitalisation. Strong long-term effects in this study indicated that stringent emission control measures would bring strong public health benefits concerning AECOPD. </p

Base Stable Pyrrolidinium Cations for Alkaline Anion Exchange Membrane Applications

The synthesis and characterization of pyrrolidinium cation based anion exchange membranes (AEMs) are reported. Pyrrolidinium cations with various N-substituents (including methyl, ethyl, butyl, octyl, isopropyl, 2-hydroxylethyl, benzyl, and cyclohexylmethyl groups) were synthesized and investigated with respect to their chemical stability in alkaline media. The influence of substitutions on alkaline stability of pyrrolidinium cations was investigated by quantitative ¹H nuclear magnetic resonance spectroscopy (NMR) and theoretical approaches. <i>N</i>,<i>N</i>-Ethylmethyl-substituted pyrrolidinium cation ([EMPy]⁺) exhibited the highest alkaline stability in this study. The synthesized AEMs based on [EMPy]⁺ show promising alkaline stability in strongly basic solution. The study of this work should provide a feasible way for improving the alkaline stability of pyrrolidinium cation based AEMs

Correlation of Flotillin2 and erbB2 expression with clinicopathologic parameters in gastric cancer.

<p>P values are based on a X2 test, *Significant difference</p

Multivariate analysis of overall survival after surgery.

<p>HR hazard radio, CI confidence interval, *Significant difference.</p

Flotillin2 expression in relation to the status of erbB2 expression.

<p>Figures in parentheses are percentages, % is within ErbB2</p>*<p>p<0.05 considered to be statistically significant.</p

Kaplan-Meier curves for patient survival.

<p>(A) Patients with an erbB2-positive tumor showed a significantly shorter survival period after surgery than those with an erbB2-negative tumor (p  = 0.014). (B) Patients with a flotillin2-positive tumor showed the worst outcome. High flotillin-2 and erbB2 expression are significantly correlated with poor patient outcome (p<0.001).</p

Univariate analysis of prognostic variables in overall survival (OS) for patients.

*<p>Significant difference.</p