A Dual-Polythiophene Blending Strategy to Reduce the Efficiency-Stability-Cost Gap of Solar Cells.

Benefiting from the photovoltaic material innovation and delicate device optimization, high-efficiency solar cells employing polymeric materials are thriving. Reducing the gap of cost, efficiency, and stability is the critical challenge faced by the emerging solar cells such as organics, quantum dots and perovskites. Poly(3-alkylthiophene) demonstrates great potential in organic solar cells and quantum dot solar cells as the active layer or the hole transport layer due to its large scalability, excellent photoelectric performance, and favorable hydrophobicity. The present low efficiency and insufficient stability, restrict its commercial application. In this work, a facile strategy of blending two simple polythiophenes is put forward to manipulate the film microstructure and enhance the device efficiency and thermal stability of solar cells. The introduction of P3PT can improve the power conversion efficiency (PCE) of a benchmark cost-effective blend P3HT:O-IDTBR to 7.41%, and the developed ternary solar cells also exhibit increased thermal stability. More strikingly, the quantum dot solar cells with the dual-polythiophene hole transport layer achieve the highest PCE of 10.51%, which is among the topmost efficiencies for quantum dots/polythiophene solar cells. Together, this work provides an effective route to simultaneously optimize the device efficiency and thermal stability of solar cells.

Effect of Achiral Glycine Residue on the Handedness of Surfactant-Like Short Peptide Self-Assembly Nanofibers.

Surfactant-like short peptides are a kind of ideal model for the study of chiral self-assembly. At present, there are few studies on the chiral self-assembly of multicharged surfactant-like peptides. In this study, we adopted a series of short peptides of Ac-I4KGK-NH2 with different combinations of L-lysine and D-lysine residues as the model molecules. TEM, AFM and SANS results showed that Ac-I4LKGLK-NH2, Ac-I4LKGDK-NH2, and Ac-I4DKGLK-NH2 formed the morphologies of nanofibers, and Ac-I4DKGDK-NH2 formed nanoribbons. All the self-assembled nanofibers, including the intermediate nanofibers of Ac-I4DKGDK-NH2 nanoribbons, showed the chirality of left handedness. Based on the molecular simulation results, it has been demonstrated that the supramolecular chirality was directly dictated by the orientation of single ß strand. The insertion of glycine residue demolished the effect of lysine residues on the single strand conformation due to its high conformational flexibility. The replacement of L-isoleucine with Da-isoleucine also confirmed that the isoleucine residues involved in the ß-sheet determined the supramolecular handedness. This study provides a profound mechanism of the chiral self-assembly of short peptides. We hope that it will improve the regulation of chiral molecular self-assembly with achiral glycine, as well.

Optimizing the Intercrystallite Connection of a Donor-Acceptor Conjugated Semiconductor Polymer by Controlling the Crystallization Rate via Temperature.

The charge carrier transport of conjugated polymer thin film is mainly decided by the crystalline domain and intercrystallite connection. High-density tie-chain can provide an effective bridge between crystalline domains. Herein, the tie-chain connection behavior is optimized by decreasing the crystal region length (lc ) and increasing the crystallization rate. Poly[4-(4,4-bis(2-octyldodecyl)-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]-thiadiazolo[3,4-c]pyridine] (PCDTPT-ODD) is dissolved in nonpolar solvent isooctane and high ordered rod-like aggregations are formed. As the temperature increases, the changes in solution state and crystallization behavior lead to three different chain arrangement morphologies in the films: 1) at 25 °C, large and separated crystal regions are formed; 2) at 55 °C, small and well-connected crystal regions are formed due to faster crystallization rate and smaller nucleus size; 3) at 90 °C, the amorphous film is formed. Further results show that the film prepared at 55 °C has a smaller crystal region length (lc , 7.6 nm) and higher tie-chains content. Thus, the film exhibits the best device mobility of 2.3 × 10-3 cm2 V-1 s-1 . This result shows the great influence of crystallization kinetics on the microstructure of conjugated polymer films and provides an effective way for the optimization of the intercrystallite tie-chain.

Ordered Packing of ß-Sheet Nanofibrils into Nanotubes: Multi-hierarchical Assembly of Designed Short Peptides.

Although it is well-known proteins and their complexes are hierarchically organized and highly ordered structures, it remains a major challenge to replicate their hierarchical self-assembly process and to fabricate multihierarchical architectures with well-defined shapes and monodisperse characteristic sizes via peptide self-assembly. Here we describe an amphiphilic short peptide Ac-I3GGHK-NH2 that first preassembles into thin, left-handed ß-sheet nanofibrils, followed by their ordered packing into right-handed nanotubes. The key intermediate morphology and structures featuring the hierarchical process are simultaneously demonstrated. Further mechanistic exploration with the variants Ac-I3GGGK-NH2, Ac-I3GGFK-NH2, and Ac-I3GGDHDK-NH2 reveals the vital role of multiple His-His side chain interactions between nanofibrils in mediating higher-order assembly and architectures. Altogether, our findings not only advance current understanding of hierarchical assembly of peptides and proteins but also afford a paradigm of how to take advantage of side chain interactions to construct higher-order assemblies with enhanced complexities.

High-resolution mass spectrometry-based methodology for the identification of the metabolites of pterostilbene produced by rat, dog and human hepatocytes.

Pterostilbene, a natural bibenzjyl compound, has been demonstrated to have pleiotropic anticancer effects against a variety of cancer types. The aim of this study was carried out to disclose the metabolic profiles of pterostilbene using rat, dog and human hepatocytes. Metabolites were characterized by ultra-high-performance liquid chromatography/quadrupole Orbitrap mass spectrometry with electrospray ionization interface operating in positive ion mode. The structures of the metabolites were proposed by accurate MS, MS/MS spectra and based on their fragmentation patterns. A total of 12 metabolites, including six new ones, were detected and identified. M10 and M12 were unambiguously identified as pinostilbene and 3'-hydroxy-pterostilbene, respectively, by using reference standards. Our results revealed that pterostilbene was metabolized through the following pathways: (a) hydroxylation to form 3'-hydroxy-pterostilbene (M12), which further undergoes glucuronidation (M9), demethylation (M7) and GSH conjugation through the ortho-quinone intermediate; (b) demethylation to produce desmethyl-pterostilbene (M10), which is further subject to glucuronidation (M4); (c) direct conjugation with glucuronide (M11); and (d) direct sulfation (M8). Among the tested species, no significant species difference was observed. The current study provides valuable information on the metabolism of pterostilbene, which is helpful for us to understand the action of this compound.

A rapid and sensitive ultra-high-pressure liquid chromatography-tandem mass spectrometry method for the determination of notoginsenoside Ft1 in rat plasma with application to pharmacokinetic study.

Notoginsenoside Ft1 (NGFt1), a dammarane triterpene glycoside isolated from Panax notoginseng, showed potent effective in stimulating platelet aggregation in our previous assay, yet its pharmacokinetic behavior is still unclear. This study describes a rapid and sensitive ultra-high-pressure LC-tandem mass spectrometry assay for determining of NGFt1 in rat plasma. Methanol-mediated precipitation was used for sample pre-treatment. Chromatographic separation was achieved on a C18 column with gradient elution using water and acetonitrile as mobile phase. Determination was obtained using an electrospray ionization source in negative selected reaction monitoring (SRM) mode at the transitions of m/z 915.9 → m/z 783.8 and m/z 799.8 → m/z 637.8 for NGFt1 and internal standard, respectively. The assay was linear over the concentration range 0.25-2500 ng/mL (r > 0.995) with the lower limit of quantification of 0.25 ng/mL. The intra- and inter-day precisions (relative standard deviation, %) ranged 1.65%-9.84% and 2.46%-13.49%, respectively, whereas accuracy (relative recovery, %) ranged from 96.21% to 99.45%, respectively. The recovery ranged from 95.09% to 102.22% and the matrix effect from 98.29% to 100.13%. The analyte was stable under tested storage conditions. The method has been successfully applied to a preclinical pharmacokinetic study in rats after a single intravenous (2 mg/kg) and oral (50 mg/kg) administration.

Identification of Human UDP-Glucuronosyltransferase 1A4 as the Major Isozyme Responsible for the Glucuronidation of 20(S)-Protopanaxadiol in Human Liver Microsomes.

20(S)-protopanaxadiol (PPD), one of the representative aglycones of ginsenosides, has a broad spectrum of pharmacological activities. Although phase I metabolism has been investigated extensively, information regarding phase II metabolism of this compound remains to be elucidated. Here, a glucuronidated metabolite of PPD in human liver microsomes (HLMs) and rat liver microsomes (RLMs) was unambiguously identified as PPD-3-O-ß-D-glucuronide by nuclear magnetic resonance spectroscopy and high resolution mass spectrometry. The chemical inhibition and recombinant human UDP-Glucuronosyltransferase (UGT) isoforms assay showed that the PPD glucuronidation was mainly catalyzed by UGT1A4 in HLM, whereas UGT1A3 showed weak catalytic activity. In conclusion, PPD-3-O-ß-D-glucuronide was first identified as the principal glucuronidation metabolite of PPD in HLMs, which was catalyzed by UGT1A4.

Determination of dencichine in Sanqi tablet by HILIC .

OBJECTIVE: To develop an HILIC method for determination of dencichine in Sanqi tablet and evaluate the quality of Sanqi tablet of different hatches from various manufactures in the market. METHOD: The chromatographic separation was conducted on a Thermo HILIC column (4.6 mm x 250 mm, 5 microm) kept at 25 degrees C with acetonitrile and 0.1% H3PO4 (60:40) as the mobile phase. The flow rate was set at 1 mL x min(-1) and the detection wavelength was set at 213 nm. RESULT: The contents of dencichine in Sanqi tablet ranged from 1.60 to 4.31 mg x g(-1). CONCLUSION: The well established method was successfully applied to determine dencichine in Sanqi tablet. The results demonstrated that this method was simple, accurate and could be applied for quality control of Sanqi as well as its associated preparations.

Metabolic profiles of 20(S)-protopanaxadiol in rats after oral administration using ultra-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry.

RATIONALE: 20(S)-Protopanaxadiol (PPD), a dammarane-type triterpenoid sapogenin, acts as the pharmacophore of ginsenosides which are considered as the principal bioactive components in Chinese ginseng. To fully understand the mechanism of action of PPD, it is important to study its metabolic profiles in vivo. METHODS: Plasma, urine, fece and bile were collected after administration of PPD formulated in 0.5% aqueous Tween-80 to rats (150 mg/kg). Samples were analyzed by using a sensitive and reliable method based on ultra-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (UPLC/Q-TOF-MS/MS) in both positive and negative ion mode. The chemical structures of metabolites were elucidated by comparing the retention time, accurate molecular mass, and fragmentation patterns of analytes with those of PPD. RESULTS: In total 29 metabolites, including 10 new metabolites (M20-M29), were tentatively identified and characterized. Among them, two metabolites (M3 and M4) were unambiguously identified by matching their retention times and fragmentation patterns with their standards. Principal metabolites, namely, 20, 24-oxide metabolites (M3 and M4), 26/27-carboxylic acid derivatives (M22 and M23) and a glucuronidated product (M28), were found in the rat plasma. CONCLUSIONS: The results showed that phase I metabolites are monooxygenation, dioxygenation and oxidative dehydrogenation metabolites, and phase II metabolic pathways were demonstrated to be cysteine conjugation and glucuronidation. The newly identified metabolites are useful to understand the mechanism of elimination of PPD and, in turn, its effectiveness and toxicity.

Combination of UHPLC/Q-TOF-MS, NMR spectroscopy, and ECD calculation for screening and identification of reactive metabolites of gentiopicroside in humans.

The metabolic investigation of natural products is a great challenge because of unpredictable metabolic pathways, little knowledge on metabolic effects, and lack of recommended analytical methodology. Herein, a combined strategy based on ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/Q-TOF-MS), nuclear magnetic resonance (NMR) spectroscopy, and electronic circular dichroism (ECD) calculation was developed and employed for the human metabolism study of gentiopicroside (GPS), a naturally hepato-protective iridoid glycoside. The whole metabolic study consisted of three major procedures. First, an improved UHPLC/Q-TOF-MS method was used to separate and detect a total of 15 GPS metabolites that were obtained from urine samples (0 to 72 h) of 12 healthy male participants after a single 50-mg oral dose of GPS. Second, a developed "MS-NMR-MS" method was applied to accurately identify molecular structures of the observed metabolites. Finally, given that the associated stereochemistry may be a crucial factor of the metabolic activation, the absolute configuration of the reactive metabolites was revealed through chemical calculations. Based on the combined use, a pair of diastereoisomers (G05 and G06) were experimentally addressed as the bioreactive metabolites of GPS, and the stereochemical determination was completed. Whereas several novel metabolic transformations, occurring via oxidation, N-heterocyclization and glucuronidation after deglycosylation, were also observed. The results indicated that GPS has to undergo in vivo metabolism-based activation to generate reactive molecules capable of processing its hepato-protective activity.

Identification of the metabolites of gigantol in rat urine by ultra-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry.

Gigantol is a typical bibenzyl compound isolated from Dendrobii Caulis that has been widely used as a medicinal herb in China for the treatment of diabetic cataract, cancer and arteriosclerosis obliterans and as a tonic for stomach nourishment, saliva secretion promotion and fever reduction. However, few studies have been carried out on its in vivo metabolism. In the present study, a rapid and sensitive method based on ultra-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-Q/TOF-MS) in positive ion mode was developed and applied to identify the metabolites of gigantol in rat urine after a single oral dose (100 mg/kg). Chromatographic separation was performed on an Acquity UPLC HSS T3 column (100 × 2.1 mm i. d., 1.8 µm) using acetonitrile and 0.1% aqueous formic acid as mobile phases. A total of 11 metabolites were detected and identified as all phase II metabolites. The structures of the metabolites were identified based on the characteristics of their MS, MS(2) data and chromatographic retention times. The results showed that glucuronidation is the principal metabolic pathway of gigantol in rats. The newly identified metabolites are useful to understand the mechanism of elimination of gigantol and, in turn, its effectiveness and toxicity. As far as we know, this is the first attempt to investigate the metabolic fate of gigantol in vivo.

Achieving Record-High Stretchability and Mechanical Stability in Organic Photovoltaic Blends with a Dilute-absorber Strategy.

Organic solar cells (OSCs) have potential for applications in wearable electronics. Except for high power conversion efficiency (PCE), excellent tensile properties and mechanical stability are required for achieving high-performance wearable OSCs, while the present metrics barely meet the stretchable requirements. Herein, this work proposes a facile and low-cost strategy for constructing intrinsically stretchable OSCs by introducing a readily accessible polymer elastomer as a diluent for all-polymer photovoltaic blends. Remarkably, record-high stretchability with a fracture strain of up to 1000% and mechanical stability with elastic recovery >90% under cyclic tensile tests are realized in the OSCs active layers for the first time. Specifically, the tensile properties of best-performing all-polymer photovoltaic blends are increased by up to 250 times after blending. Previously unattainable performance metrics (fracture strain >50% and PCE >10%) are achieved simultaneously for the resulting photovoltaic films. Furthermore, an overall evaluation parameter y is proposed for the efficiency-cost- stretchability balance of photovoltaic blend films. The y value of dilute-absorber system is two orders of magnitude greater than those of prior state-of-the-art systems. Additionally, intrinsically stretchable devices are prepared to showcase the mechanical stability. Overall, this work offers a new avenue for constructing and comprehensively evaluating intrinsically stretchable organic electronic films.

Unraveling the Solution Aggregation Structures and Processing Resiliency of High-Efficiency Organic Photovoltaic Blends.

The solution aggregation structure of conjugated polymers is crucial to the morphology and resultant optoelectronic properties of organic electronics and is of considerable interest in the field. Precise characterizations of the solution aggregation structures of organic photovoltaic (OPV) blends and their temperature-dependent variations remain challenging. In this work, the temperature-dependent solution aggregation structures of three representative high-efficiency OPV blends using small-angle X-ray/neutron scattering are systematically probed. Three cases of solution processing resiliency are elucidated in state-of-the-art OPV blends. The exceptional processing resiliency of high-efficiency PBQx-TF blends can be attributed to the minimal changes in the multiscale solution aggregation structure at elevated temperatures. Importantly, a new parameter, the percentage of acceptors distributed within polymer aggregates (Ф), for the first time in OPV blend solution, establishes a direct correlation between Ф and performance is quantified. The device performance is well correlated with the Kuhn length of the cylinder related to polymer aggregates L1 at the small scale and the Ф at the large scale. Optimal device performance is achieved with L1 at ≈30 nm and Ф within the range of 60 ± 5%. This study represents a significant advancement in the aggregation structure research of organic electronics.

Controlled Assembly and Disassembly of Higher-Order Peptide Nanotubes.

The controlled peptide self-assembly and disassembly are not only implicated in many cellular processes but also possess huge application potential in a wide range of biotechnology and biomedicine. ß-sheet peptide assemblies possess high kinetic stability, so it is usually hard to disassemble them rapidly. Here, we reported that both the self-assembly and disassembly of a designed short ß-sheet peptide IIIGGHK could be well harnessed through the variations of concentration, pH, and mechanical stirring. Microscopic imaging, neutron scattering, and infrared spectroscopy were used to track the assembly and disassembly processes upon these stimuli, especially the interconversion between thin, left-handed protofibrils and higher-order nanotubes with superstructural right-handedness. The underlying rationale for these controlled disassembly processes mainly lies in the fact that the specific His-His interactions between protofibrils were responsive to these stimuli. By taking advantage of the peptide self-assembly and disassembly, the encapsulation of the hydrophobic drug curcumin and its rapid release upon stimuli were achieved. Additionally, the peptide hydrogels facilitated the differentiation of neural cells while maintaining low cell cytotoxicity. We believe that such dynamic and reversible structural transformation in this work provides a distinctive paradigm for controlling the peptide self-assembly and disassembly, thus laying a foundation for practical applications of peptide assemblies.

Preclinical evaluation of chemically reactive metabolites and mitigation of bioactivation in drug discovery.

The formation of reactive metabolites (RMs) is thought to be one of the pathogeneses for some idiosyncratic adverse drug reactions (IADRs) which are considered one of the leading causes of some drug attritions and/or recalls. Minimizing or eliminating the formation of RMs via chemical modification is a useful tactic to reduce the risk of IADRs and time-dependent inhibition (TDI) of cytochrome P450 enzymes (CYPs). The RMs should be carefully handled before making a go-no-go decision. Herein, we highlight the role of RMs in the occurrence of IADRs and CYP TDI, the risk of structural alerts, the approaches of RM assessment at the discovery stage and strategies to minimize or eliminate RM liability. Finally, some considerations for handling a RM-positive drug candidate are suggested.

Development of an automatic sample changer with variable temperature for small-angle neutron scattering at China Spallation Neutron Source.

A small-angle neutron scattering (SANS) instrument at the China Spallation Neutron Source (CSNS) is an operating instrument for studying structures and inhomogeneities with dimensions ranging from 1 to 100 nm. Preparing multiple samples at once and measuring them sequentially is a common approach in SANS experiments to reduce neutron beamline wastes and increase experimental efficiency. We present the development of an automatic sample changer for the SANS instrument, including system design, thermal simulation, optimization analysis, structure design details, and temperature control test results. It features a two-row construction that can hold 18 samples on each row. The controllable temperature range is -30 to 300 °C. Furthermore, neutron scattering experiments on SANS at CSNS proved that this instrument has good temperature control performance and low background. This automatic sample changer is optimized for usage at SANS and will be offered to other researchers through the user program.

Exploiting terminal charged residue shift for wide bilayer nanotube assembly.

HYPOTHESIS: Self-assembly of peptides is influenced by both molecular structure and external conditions, which dictate the delicate balance of different non-covalent interactions that driving the self-assembling process. The shifting of terminal charge residue is expected to influence the non-covalent interactions and their interplay, thereby affecting the morphologies of self-assemblies. Therefore, the morphology transition can be realized by shifting the position of the terminal charge residue. EXPERIMENTS: The structure transition from thin nanofibers to giant nanotubes is realized by simply shifting the C-terminal lysine of ultrashort Ac-I3K-NH2 to its N-terminus. The morphologies and detailed structure information of the self-assemblies formed by these two peptides are investigated systemically by a combination of different experimental techniques. The effect of terminal residue on the morphologies of the self-assemblies is well presented and the underlying mechanism is revealed. FINDINGS: Giant nanotubes with a bilayer shell structure can be self-assembled by the ultrashort peptide Ac-KI3-NH2 with the lysine residue close to the N-terminal. The Ac-KI3-NH2 dimerization through intermolecular C-terminal H-bonding promotes the formation of a bola-form geometry, which is responsible for the wide nanotube assembly formation. The evolution process of Ac-KI3-NH2 nanotubes follows the "growing width" model. Such a morphological transformation with the terminal lysine shift is applicable to other analogues and thus provides a facile approach for the self-assembly of wide peptide nanotubes, which can expand the library of good template structures for the prediction of peptide nanostructures.

Determination of the Structures of Lignin Subunits and Nanoparticles in Solution by Small-Angle Neutron Scattering: Towards Improving Lignin Valorization.

Lignin nanoparticles (LNPs) are usually produced from lignin solution through supersaturation. The structure of the lignin in solution is still poorly understood due to structural variability of isolated lignins. Here, lignins were extracted from different plants to establish a general pattern of their structure in several lignin solvents. Lignin molecules (lignin subunits) and larger aggregates were observed in dimethyl sulfoxide (DMSO), ethylene glycol (EG) and 0.1 N NaOD solutions by small-angle neutron scattering (SANS). It was proposed that the aggregates were composed of lignin subunits with a higher molecular weight and a higher ratio of the aliphatic to phenolic hydroxyl groups. The size, shape, and compactness are important factors that affect the uses of the LNPs, which were obtained from the SANS data for the first time. A discrepancy in the radius between SANS and DLS was discovered, pointing to a large hydration shell around the LNPs in aqueous solutions. The cytotoxicity of the corncob lignin, kraft lignin, and their LNPs were measured and compared.

Unraveling the Molar Mass Dependence of Shearing-Induced Aggregation Structure of a High-Mobility Polymer Semiconductor.

Aggregation-structure formation of conjugated polymers is a fundamental problem in the field of organic electronics and remains poorly understood. Herein, the molar mass dependence of the aggregation structure of a high-mobility conjugated copolymer (TDPP-Se) comprising thiophene-flanked diketopyrrolopyrrole and selenophene is thoroughly shown. Five batches of TDPP-Se are prepared with the number-average molecular weights (Mn ) varied greatly from 21 to 135 kg mol-1 . Small-angle neutron scattering and transmission electron microscopy are combined to probe the solution structure of these polymers, consistently using a deuterated solvent. All the polymers adopt 1D rod-like aggregation structures and the radius of the 1D rods is not sensitive to the Mn , while the length increases monotonically with Mn . By utilizing the ordered packing of the aggregated structure in solution, a highly aligned and ordered film is prepared and, thereafter, a reliable hole mobility of 13.8 cm2 V-1 s-1 is realized in organic thin-film transistors with the moderate Mn batch via bar coating. The hole mobility is among the highest values reported for diketopyrrolopyrrole-based polymers. This work paves the way to visualize the real aggregated structure of polymer semiconductors in solution and sheds light on the microstructure control of high-performance electronic devices.

Hysteresis-Free Nanoparticle-Reinforced Hydrogels.

The elastic storage and release of mechanical energy has been key to many developments throughout the history of mankind. Resilience, absent hysteresis, has been an elusive goal to achieve, particularly at large deformations. Using a low-crosslink-density polyacrylamide hydrogel at 96% water content having hyperbranched silica nanoparticles (HBSPs) as the major junction points, a hysteresis-free material is realized. The fatigue-free characteristic of these composite hydrogels is evidenced by the invariance of the stress-strain curves at strain ratios of 4, even after 5000 cycles. At a strain ratio of 7, only a 1.3% hysteresis is observed. A markedly increased strain-ratio-at-break of 11.5 is observed. The unique attributes of these resilient hydrogels are manifested in the high-fidelity detection of dynamic deformations under cyclic loading over a broad range of frequencies, difficult to achieve with other materials.