A series of three air-stable ester-functionalized polythiophenes were tested for performance and stability in organic thin film transistors. The highest saturated field effect mobility of the series ...was 3.3 x 10 super(-3) cm super(2) V super(-1) s super(-1). The three polymers showed only a small decrease in performance over the course of one month, while P3HT devices fabricated for comparison no longer functioned after this storage interval. The polymers are stable in air due to a HOMO level of -5.6 eV as measured by CV. Increased crystallinity as measured by XRD and DSC accounts for the highest mobility polymer.
Understanding the factors underpinning device switching times is crucial for the implementation of organic electrochemical transistors (OECTs) in neuromorphic computing and real-time sensing ...applications. Existing models of device operation cannot explain the experimental observations that turn-off times are generally much faster than turn-on times in accumulation mode OECTs. Through operando optical microscopy, we image the local doping level of the transistor channel and show that device turn-on occurs in two stages, while turn-off occurs in one stage. We attribute the faster turn-off to a combination of engineering as well as physical and chemical factors including channel geometry, differences in doping and dedoping kinetics, and the physical phenomena of carrier density-dependent mobility. We show that ion transport is limiting the device operation speed in our model devices. Our study provides insights into the kinetics of OECTs and guidelines for engineering faster OECTs.
Carrier spins in semiconductor nanocrystals are promising candidates for quantum information processing. Using a combination of time-resolved Faraday rotation and photoluminescence spectroscopies, we ...demonstrate optical spin polarization and coherent spin precession in colloidal CsPbBr3 nanocrystals that persists up to room temperature. By suppressing the influence of inhomogeneous hyperfine fields with a small applied magnetic field, we demonstrate inhomogeneous hole transverse spin-dephasing times (T2*) that approach the nanocrystal photoluminescence lifetime, such that nearly all emitted photons derive from coherent hole spins. Thermally activated LO phonons drive additional spin dephasing at elevated temperatures, but coherent spin precession is still observed at room temperature. These data reveal several major distinctions between spins in nanocrystalline and bulk CsPbBr3 and open the door for using metal-halide perovskite nanocrystals in spin-based quantum technologies.
We find that conjugated polymers can undergo reversible structural phase transitions during electrochemical oxidation and ion injection. We study ...poly2,5-bis(thiophenyl)-1,4-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzene (PB2T-TEG), a conjugated polymer with glycolated side chains. Using grazing incidence wide angle X-ray scattering (GIWAXS), we show that, in contrast to previously known polymers, this polymer switches between two structurally distinct crystalline phases associated with electrochemical oxidation/reduction in an aqueous electrolyte. Importantly, we show that this unique phase change behavior has important physical consequences for ion transport. Notably, using moving front experiments visualized by both optical microscopy and super-resolution photoinduced force microscopy (PiFM), we show that a propagating ion front in PB2T-TEG exhibits non-Fickian transport, retaining a sharp step-edge profile, in stark contrast to the Fickian diffusion more commonly observed. This structural phase transition is reminiscent of those accompanying ion uptake in inorganic materials like LiFePO\(_{4}\). We propose that engineering similar properties in future conjugated polymers may enable the realization of new materials with superior performance in electrochemical energy storage or neuromorphic memory applications.
Fat is the most potent stimulus for glucagon-like peptide-1 (GLP-1) secretion. The aims of this study were to determine whether dipeptidyl peptidase IV (DPP-IV) inhibition would enhance plasma active ...incretin glucose-dependent insulinotropic polypeptide (GIP), GLP-1 concentrations and modulate the glycemic, gut hormone, triglyceride, energy expenditure, and energy intake responses to intraduodenal fat infusion. In a double-blind, randomized, placebo-controlled crossover design, 16 healthy lean males received 50 mg vildagliptin (V), or matched placebo (P), before intraduodenal fat infusion (2 kcal/min, 120 min). Blood glucose, plasma insulin, glucagon, active GLP-1, and GIP and peptide YY (PYY)-(3-36) concentrations; resting energy expenditure; and energy intake at a subsequent buffet meal (time = 120-150 min) were quantified. Data are presented as areas under the curve (0-120 min, means ± SE). Vildagliptin decreased glycemia (P: 598 ± 8 vs. V: 573 ± 9 mmol·l⁻¹·min⁻¹, P < 0.05) during intraduodenal lipid. This was associated with increased insulin (P: 15,964 ± 1,193 vs. V: 18,243 ± 1,257 pmol·l⁻¹·min⁻¹, P < 0.05), reduced glucagon (P: 1,008 ± 52 vs. V: 902 ± 46 pmol·l⁻¹·min⁻¹, P < 0.05), enhanced active GLP-1 (P: 294 ± 40 vs. V: 694 ± 78 pmol·l⁻¹·min⁻¹) and GIP (P: 2,748 ± 77 vs. V: 4,256 ± 157 pmol·l⁻¹·min⁻¹), and reduced PYY-(3-36) (P: 9,527 ± 754 vs. V: 4,469 ± 431 pM/min) concentrations compared with placebo (P < 0.05, for all). Vildagliptin increased resting energy expenditure (P: 1,821 ± 54 vs. V: 1,896 ± 65 kcal/day, P < 0.05) without effecting energy intake. Vildagliptin 1) modulates the effects of intraduodenal fat to enhance active GLP-1 and GIP, stimulate insulin, and suppress glucagon, thereby reducing glycemia and 2) increases energy expenditure. These observations suggest that the fat content of a meal, by enhancing GLP-1 and GIP secretion, may contribute to the response to DPP-IV inhibition.
Synthesis of two possible diastereomers of (+)-didemniserinolipid B (1), the first natural serinolipid isolated from a tunicate Didemnum sp., were studied. The known butanediacetal (BDA) protected ...aldehyde 2 was converted to the core coupling component 8. The serinol fragments (S)-13 and (R)-13 were prepared from D-serine and L-serine, respectively. Wittig-Horner reaction of 8 and (S)-13 gave (4"S)-14, which was converted to ester (4"S)-18. Finally, removal of all the protecting group was achieved in acidic EtOH to afford (30S)-1. Similarly, (30R)-1 was synthesized from (R)-13. However, the ^1H and ^ C NMR spectra of the synthetic 1 were different from those of natural 1. In view of the fact that related natural products were sulfated on the serinol unit we therefore believed the 31 position of the natural 1 should be sulfated. Based on this assumption, we investigated further derivatization of the synthetic compounds. We studied sulfation of N-Fmoc derivative (30R)-19, however, with the usual reagents and conditions resulted in only recovery of the starting material. Finally we developed new microwave-assisted sulfation conditions which gave the desired monosulfate, followed by the Fmoc deprotection affording 31-monosulfate (30R)-20. As the ^1H and ^ C NMR data and the value of the specific optical rotation of (30R)-20 coincided with those of the natural product, we concluded that the real structure of (+)-didemniserinolipid B corresponded to a 31-sulfate and the absolute configuration was 8R,9R,10R,13S,30S. The microwave-assisted sulfation developed in this process are effective for unreactive hydroxyl groups.
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