Tethered Trimeric Small-molecular Acceptors through Aromatic-core Engineering for Highly Efficient and Thermally Stable Polymer Solar Cells.

Polymer solar cells (PSCs) rely on a blend of small molecular acceptors (SMAs) with polymer donors, where thermodynamic relaxation of SMAs poses critical concerns on operational stability. To tackle this issue, tethered SMAs, wherein multiple SMA-subunits are connected to the aromatic-core via flexible chains, are proposed. This design aims to an elevated glass transition temperature (Tg) for a dynamical control. However, attaining an elevated Tg value with additional SMA subunits introduces complexity to the molecular packing, posing a significant challenge in realizing both high stability and power conversion efficiency (PCE). In this study, we initiate isomer engineering on the benzene-carboxylate core and find that meta-positioned dimeric BDY-ß exhibits more favorable molecular packing compared to its para-positioned counterpart, BDY-α. With this encouraging result, we expand our approach by introducing an additional SMA unit onto the aromatic core of BDY-ß, maintaining a meta-position relative to each SMA unit location in the tethered acceptor. This systematic aromatic-core engineering results in a star-shaped C3h-positioned molecular geometry. The supramolecular interactions of SMA units in the trimer contribute to enhancements in Tg value, crystallinity, and a red-shifted absorption compared to dimers. These characteristics result in a noteworthy increase in PCE to 18.24 %, coupled with a remarkable short-circuit current density of 27.06 mA cm-2. More significantly, the trimer-based devices delivered an excellent thermal stability with over 95 % of their initial efficiency after 1200 h thermal degradation. Our findings underscore the promise and feasibility of tethered trimeric structures in achieving highly ordered aggregation behavior and increased Tg value in PSCs, simultaneously improving in device efficiency and thermal stability.

Modular-Approach Synthesis of Giant Molecule Acceptors via Lewis-Acid-Catalyzed Knoevenagel Condensation for Stable Polymer Solar Cells.

The operational stability of polymer solar cells is a critical concern with respect to the thermodynamic relaxation of acceptor-donor-acceptor (A-D-A) or A-DA'D-A structured small-molecule acceptors (SMAs) within their blends with polymer donors. Giant molecule acceptors (GMAs) bearing SMAs as subunits offer a solution to this issue, while their classical synthesis via the Stille coupling suffers from low reaction efficiency and difficulty in obtaining mono-brominated SMA, rendering the approach impractical for their large-scale and low-cost preparation. In this study, we present a simple and cost-effective solution to this challenge through Lewis acid-catalyzed Knoevenagel condensation with boron trifluoride etherate (BF3 ⋅ OEt2 ) as catalyst. We demonstrated that the coupling of the monoaldehyde-terminated A-D-CHO unit and the methylene-based A-link-A (or its silyl enol ether counterpart) substrates can be quantitatively achieved within 30 minutes in the presence of acetic anhydride, affording a variety of GMAs connected via the flexible and conjugated linkers. The photophysical properties was fully studied, yielding a high device efficiency of over 18 %. Our findings offer a promising alternative for the modular synthesis of GMAs with high yields, easier work up, and the widespread application of such methodology will undoubtedly accelerate the progress of stable polymer solar cells.

Diagnostic accuracy of procalcitonin on POD3 for the early diagnosis of anastomotic leakage after colorectal surgery: A meta-analysis and systematic review.

OBJECTIVE: Anastomotic leakage is one of the most serious complications after colorectal surgery, and a reliable method for early diagnosis is urgently needed. Procalcitonin (PCT) is recently considered a potential biomarker by many studies, but their conclusions in detail are controversial. This meta-analysis was conducted to further explore and verify the diagnostic value of the procalcitonin level on postoperative day 3 (POD3) in patients undergoing colorectal surgery. METHODS: This review was performed using the Preferred Reporting Items for a Systematic Review and Meta-analysis of Diagnostic Test Accuracy (PRISMA-DTA) statement. Studies were searched in PubMed, EMBASE, Cochrane Library, Wanfang, and China National Knowledge Infrastructure (CNKI) until August 2021. Quality of the studies was scored based on the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and a summary receiver operating characteristics (SROC) curve were used to estimate the diagnostic value. Meta-regression and subgroup analyses were performed to further explore the primary source of heterogeneity and the influence of various factors on diagnostic accuracy. RESULTS: Eleven studies and 3393 patients were included in our meta-analysis. The derived cutoff value of PCT was 1.12 ng/ml by geometric mean and the pooled sensitivity, specificity, PLR, NLR and DOR were 0.768 (0.704-0.825), 0.788 (0.774-0.802), 4.600 (3.129-6.763), 0.339 (0.267-0.431) and 18.114 (9.872-33.239), respectively. The computed AUC from the SROC curve was 0.8714, and the Q* index was 0.8019. The results of meta-regression and subgroup analyses showed that the usage of laparoscopic surgery was the major factor in improving the reliability of PCT data, and 0.7-1.3 ng/ml may be the appropriate interval for PCT with the DOR (38.610 (16.324-91.321)) well above the average. CONCLUSIONS: The PCT level on POD3 has potential clinical value in the early diagnosis of AL and exhibits a better diagnostic accuracy in patients undergoing laparoscopic surgery. Cut-off values are recommended at the interval range of 0.7-1.3 ng/ml to ensure accurate diagnosis and safe discharge. Research Registry Registration Number: reviewregistry 1282.