Polymeric Semiconductor in Field-Effect Transistors Utilizing Flexible and High-Surface Area Expanded Poly(tetrafluoroethylene) Membrane Gate Dielectrics.

Organic field-effect transistors (OFETs) were fabricated using three high-surface area and flexible expanded-poly(tetrafluoroethylene) (ePTFE) membranes in gate dielectrics, along with the semiconducting polymer poly[2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-3,6-diyl)-alt-(2,2':5',2″:5″,2‴-quaterthiophen-5,5‴-diyl)] (PDPP4T). The transistor behavior of these devices was investigated following annealing at 50, 100, 150, and 200 °C, all sustained for 1 h. For annealing temperatures above 50 °C, the OFETs displayed improved transistor behavior and a significant increase in output current while maintaining similar magnitudes of Vth shifts when subjected to static voltage compared to those kept at ambient temperature. We also tested the response to NO2 gas for further characterization and for possible applications. The ePTFE-PDPP4T interface of each membrane was characterized via scanning electron microscopy for all four annealing temperatures to derive a model for the hole mobility of the ePTFE-PDPP4T OFETs that accounts for the microporous structure of the ePTFE and consequently adjusts the channel width of the OFET. Using this model, a maximum hole mobility of 1.8 ± 1.0 cm2/V s was calculated for the polymer in an ePTFE-PDPP4T OFET annealed at 200 °C, whereas a PDPP4T OFET using only the native silicon wafer oxide as a gate dielectric exhibited a hole mobility of just 0.09 ± 0.03 cm2/V s at the same annealing condition. This work demonstrates that responsive semiconducting polymer films can be deposited on nominally nonwetting and extremely bendable membranes, and the charge carrier mobility can be significantly increased compared to their as-prepared state by using thermally durable polymer membranes with unique microstructures as gate dielectrics.

Co(II) complexes of tetraazamacrocycles appended with amide or hydroxypropyl groups as paraCEST agents.

Co(II) complexes of 1,4,7,10-tetraazacyclododecane (CYCLEN) or 1,4,8,11-tetraazacyclotetradecane (CYCLAM) with 2-hydroxypropyl or carbamoylmethyl (amide) pendants are studied with the goal of developing paramagnetic chemical exchange saturation transfer (paraCEST) agents. Single-crystal X-ray diffraction studies show that two of the coordination cations with hexadentate ligands, [Co(DHP)]2+ and [Co(BABC)]2+, form six-coordinate complexes; whereas two CYCLEN-based complexes with potentially octadentate ligands, [Co(THP)]2+ and [Co(HPAC)]2+, are seven-coordinate with only three of the four pendant groups bound to the metal center. 1H NMR spectra of these complexes suggest that the six-coordinate complexes are present as a single isomer in aqueous solution. For the complexes which are seven-coordinate in the solid state, one is highly fluxional in aqueous solution on the NMR time scale ([Co(HPAC)]2+), whereas the NMR spectrum of [Co(THP)]2+ is consistent with an eight-coordinate complex with all pendants bound. Co(II) complexes of CYCLEN derivatives show CEST effects of low intensity that are assigned to NH or OH groups of the pendants. One complex, [Co(DHP)]2+, shows a highly-shifted CEST peak at 113 ppm versus bulk water, attributed to OH protons. However, the CEST effect is largest for two Co(II) CYCLAM-based complexes with coordinated amide groups that undergo NH proton exchange. All five complexes are inert towards dissociation in buffered solutions containing carbonate and phosphate and towards trans-metalation by excess Zn(II). These data give insight into the production of an intense CEST effect for tetraazamacrocyclic complexes with pendant groups containing NH or OH exchangeable protons. The intense and highly shifted CEST peak(s) of the CYCLAM-based complexes suggest that they are promising for further development as paraCEST agents.

CorMatrix Anterior Leaflet Augmentation of the Tricuspid Valve: Midterm Results.

BACKGROUND: Tricuspid annuloplasty is the most common surgical approach to correct tricuspid regurgitation (TR). In some patients, however, anterior leaflet patch augmentation may be necessary to optimize tricuspid competence. We reviewed our center cohort over the midterm and long term. METHODS: From January 2013 to August 2018, 424 tricuspid valve procedures were performed, of which 420 were repairs and 4 were replacements. Indications were either isolated severe TR or moderate or greater TR, concomitant with other surgery. In the repair cohort, we identified those that had a patch augmentation, and the database was interrogated for preoperative characteristics. The resulting patients had outpatient assessment (clinical and echocardiography) at 6 weeks and at a later interval. Additionally, a comparison was made between those who had good and poor results (moderate or greater TR or cardiac death). RESULTS: In the repair cohort, 19 patients underwent complex tricuspid valve repair with CorMatrix anterior leaflet augmentation. Preoperative characteristics were as follows: age, 65.5 ± 13.5 years; New York Heart Association (NYHA) class, 3.5 ± 0.5; left ventricular ejection fraction, 48.3% ± 5.9%; tricuspid annular plane systolic excursion, 17.1 ± 3.7 mm; right ventricle (good, mild, moderate, poor), 10, 5, 4, 0; annulus size, 40.9 ± 6.9 mm; mean tethering distance, 1.00 ± 0.3 cm; and mean tethering area, 1.53 ± 1.16 cm2. Mean follow-up was 2.1 ± 1.9 years, and survival at 2 years was 73.8%. There were 2 in-hospital deaths. Mean NYHA class was 1.0 ± 0.5 (6 weeks) and 1.5 ± 0.6 (later follow-up); mean residual TR grade was 0.5 ± 0.6 (6 weeks) and 1.3 ± 1.4 (follow-up). Ten of 13 survivors had a good result at last follow-up (TR 0 to 1). We compared the preoperative and operative data of this group versus those with poor results (TR >1 or cardiac mortality). Significant univariate predictors of poor results were larger preoperative tethering area (1.18 ± 0.43 versus 2.4 ± 1.5 cm2; P = .02), longer tethering distance (0.87 ± 0.21 versus 1.2 ± 0.19 cm; P = .007), or the presence of mild or greater TR at 6 weeks (0.2 ± 0.4 vs 1.25 ± 0.5; P = .03). CONCLUSIONS: CorMatrix anterior leaflet augmentation produces successful, stable repair in the majority of this complex population. The presence of even mild TR at 6 weeks' follow-up predicts a poor result. When the tethering area or the tethering distance is significantly high, replacement is probably a better option.