A Non-Conjugated Polymer Acceptor for Efficient and Thermally Stable All-Polymer Solar Cells

A non-conjugated polymer acceptor PF1-TS4 was firstly synthesized by embedding a thioalkyl segment in the mainchain, which shows excellent photophysical properties on par with a fully conjugated polymer, with a low optical band gap of 1.58 eV and a high absorption coefficient >10⁵ cm⁻¹, a high LUMO level of −3.89 eV, and suitable crystallinity. Matched with the polymer donor PM6, the PF1-TS4-based all-PSC achieved a power conversion efficiency (PCE) of 8.63 %, which is ≈45 % higher than that of a device based on the small molecule acceptor counterpart IDIC16. Moreover, the PF1-TS4-based all-PSC has good thermal stability with ≈70 % of its initial PCE retained after being stored at 85 °C for 180 h, while the IDIC16-based device only retained ≈50 % of its initial PCE when stored at 85 °C for only 18 h. Our work provides a new strategy to develop efficient polymer acceptor materials by linkage of conjugated units with non-conjugated thioalkyl segments.     

Cellular Synthesis and X-ray Crystal Structure of a Designed Protein Heterocatenane

Herein, we report the biosynthesis of protein heterocatenanes using a programmed sequence of multiple post-translational processing events including intramolecular chain entanglement, in situ backbone cleavage, and spontaneous cyclization. The approach is general, autonomous, and can obviate the need for any additional enzymes. The catenane topology was convincingly proven using a combination of SDS-PAGE, LC-MS, size exclusion chromatography, controlled proteolytic digestion, and protein crystallography. The X-ray crystal structure clearly shows two mechanically interlocked protein rings with intact folded domains. It opens new avenues in the nascent field of protein-topology engineering.     

The use of Herschel–Quincke tubes to improve the efficiency of lined ducts

The scattering matrix results of Herschel–Quincke (HQ) resonators installed in combination with an acoustic liner (HQ-Liners) are presented in this paper. This approach aims at controlling both tonal and broadband noise to improve the liner efficiency. It uses circumferential arrays of Herschel–Quincke tubes on a main duct in a serial association with a locally reacting liner of known impedance. Results for the scattering matrix of this system are deduced from an analytical model and compared with experimental and numerical data showing a good agreement. Analysis of the scattering matrix coefficients points out the modal conversion properties that depend on the number of HQ tubes along the circumference. Results of the transmission loss show that the choice of an optimal HQ configuration with respect to the liner properties can substantially improve the liner efficiency.     

Recent advances in short peptide self-assembly: from rational design to novel applications

Owing to their structural simplicity and robust self-assembled nanostructures, short peptides prove to be an ideal system to explore the physical processes of self-assembly, hydrogels, semi-flexible polymers, quenched disorder, and reptation. Rational design in peptide sequences facilitates cost-effective manufacturing, but the huge number of possible peptides has imposed obstacles for their characterization to establish functional connections to the primary, secondary, and tertiary structures. This review aims to cover recent advances in the self-assembly of designed short peptides, with a focus on physical driving forces, design rules, characterization methods, and exemplar applications. Super-resolution microscopy in combination with modern image analysis have been applied to quantify the structure and dynamics of peptide hydrogels, while small-angle neutron scattering and solid-state nuclear magnetic resonance continue to provide valuable information on structures over complementary length scales. Short peptides are attractive in biomedicine and nanotechnology, e.g., as antimicrobials, anticancer agents, vehicles for controlled drug release, peptide bioelectronics, and responsive cell culture materials.     

Different defect morphologies in polyethylene crystal induced by surface physicochemical properties

The physicochemical properties of surfaces have a great effect on the micro-morphologies of the crystal structures which are in contact with them.Understanding the interaction mechanism between the internal driving forces of the crystal and external inducing forces of the surfaces is the prerequisite of controlling and obtaining the desirable morphologies.In this work,the dynamic density functional theory was applied to construct the free energy functional expression of polyethylene(PE) lattice,and the micro-dynamic evolution processes of PE lattice morphology near the surfaces with different properties were observed to reveal the interaction mechanism at atomic scale.The results showed that the physical and chemical properties of the external surfaces synergistically affect the morphologies in both the defect shapes and the distribution of the defect regions.In the absence of the contact surfaces,driven by the oriented interactions among different CH2 groups,PE lattices gradually grow and form a defect-free structure.Conversely,the presence of contact surfaces leads to lattice defects in the interfacial regions,and PE lattice shows different self-healing abilities around different surfaces.     

Synthesis and characterization of an unexpected mechanochromicbistricyclic aromatic ene

An unexpected bistricyclic aromatic ene AF was synthesized in a tin(II) chloride-mediated reductive aromatization reaction. The obtained AF showed a highly overcrowded structural conformation as revealed by X-ray crystallography. Interestingly, AF exhibited reversible high-contrast mechanochromism and thermochromism between pale and red color. The obvious chromism is likely ascribed to the conformation transformation and trace amount of diradical species formation upon stimulus.     

Dynamic and reversible electrowetting with low voltage on the dimethicone infused carbon nanotube array in air

Unremitting efforts have been intensively making for pursuing the goal of the reversible transition of electrowetting owing to its vital importance to many practical applications, but which remains a major challenge for carbon nanotubes due to the irreversible electrochemical damage. Herein, we proposed a subtly method to prevent the CNT array from electrochemical damage by using liquid medium instead of air medium to form a liquid/liquid/solid triphase system. The dimethicone dynamically refills in CNT arrays after removing of voltage that makes the surface back to hydrophobic, which is an elegant way to not only decrease energy dissipation in electrowetting process but also obtain extra energy in reversible dewetting process. Repeated cycles of in situ experiments showed that more than four reversible electrowetting cycles could be achieved in air. It worth mention that the in situ reversible electrowetting voltage of the dimethicone infused CNT array has been lowered to 2 V from 7 V which is the electrowetting voltage for the pure CNT array. The surface of the dimethicone infused CNT array can maintain hydrophobicity with a contact angle of 145.6° after four cycles, compared with 148.1° of the initial state. Moreover, a novel perspective of theoretical simulations through the binding energy has been provided which proved that the charged CNTs preferred binding with water molecules thereby replacing the dimethicone molecules adsorbed on the CNTs, whereas reconnected with dimethicone after removing the charges. Our study provides distinct insight into dynamic reversible electrowetting on the nanostructured surface in air and supplies a way for precise control of wettability in surface chemistry, smart phase-change heat transfer enhancement, liquid lenses, microfluidics, and other chemical engineering applications.     

Theoretical insights into the mechanism of photocatalytic reduction of CO2 over semiconductor catalysts

Photocatalytic reduction of CO₂ is one important approach to alleviate greenhouse gas emission and energy crisis, which has gained huge attention in the past decades. However, the lack of understanding complex reaction mechanism impedes new catalysts design. It is also very difficult to understand the mechanism by using only experimental approaches. For this concern, theoretical calculations can effectively supplement the experimental deficiency and thus play an important role. Recently theoretical calculations have been performed on adsorption, migration and reduction of CO₂ molecule on the photocatalyst surface, leading to useful information that have contributed greatly to this field. This review summarizes recent advances in first-principles calculations about CO₂ photoreduction over various semiconductor photocatalysts like metal oxides, sulfides and g-C₃N₄. The methods, models, adsorption and reaction pathways have been discussed in detail. The perspective about future investigation on the photocatalytic reduction of CO₂ using first principles calculations is also presented.     

Genetically engineered materials: Proteins and beyond

Information-rich molecules provide opportunities for evolution.Genetically engineered materials are superior in that their properties are coded within genetic sequences and could be fine-tuned.In this review,we elaborate the concept of genetically engineered materials(GEMs)using examples ranging from engineered protein materials to engineered living materials.Proteinbased materials are the materials of choice by nature.Recent progress in protein engineering has led to opportunities to tune their sequences for optimal material performance.Proteins also play a central role in living materials where they act in concert with other biological components as well as nonbiological cofactors,giving rise to living features.While the existing GEMs are often limited to those constructed by building blocks of biological origin,being genetically engineerable does not preclude nonbiologic or synthetic materials,the latter of which have yet to be fully explored.     

The Shackling Effect in Cyclic Azobenzene Liquid Crystal

We demonstrate here a novel method for the design of liquid crystals (LCs) via the cyclization of mesogens by flexible chains. For two azobenzene-4,4′-dicarboxylate derivatives, the cyclic dimer, cyclic bis(tetraethylene glycol azobenzene-4,4′-dicarboxylate) (CBTAD), shows LC properties with smectic A phase, while its linear counterpart, bis(2-(2′-hydroxyethyloxy)ethyl azobenzene-4,4′-dicarboxylate (BHAD), has no LC phase. The difference is ascribed to the shackling effect from the cyclic topology, which leads to the much smaller entropy change during phase transitions and increases the isotropic temperature greatly for cyclics. In addition, the trans-to-cis isomerization of azobenzene groups under UV-light is also limited in CBTAD. With the reversible isomerization of azobenzene groups, CBTAD showed interesting isothermal phase transition behaviors, where the LC phase disappeared upon photoirradiation of 365 nm UV-light, and recovered when the UV-light was off. Combined with the smectic LC nature, a novel UV-light tuned visible light regulator was designed, by simply placing CBTAD in two glass plates. The scattered phase of smectic LC was utilized as the “OFF” state for light passage, while the UV-light induced isotropic phase was utilized as the “ON” state. The shackling effect outlined here should be applicable for the design of cyclic LC oligomers/polymers with special properties.