Enhancing Planar Inverted Perovskite Solar Cells with Innovative Dumbbell-Shaped HTMs: A Study of Hexabenzocoronene and Pyrene-BODIPY-Triarylamine Derivatives

Dumbbell-shaped systems based on PAHs-BODIPY-triarylamine hybrids TM-(01-04) are designed as novel and highly efficient hole-transporting materials for usage in planar inverted perovskite solar cells. BODIPY is employed as a bridge between the PAH units, and the effects of the conjugated π-system's covalent attachment and size are investigated. Fluorescence quenching, 3D fluorescence heat maps, and theoretical studies support energy transfer within the moieties. The systems are extremely resistant to UVC 254 nm germicidal light sources and present remarkable thermal stability at degradation temperatures exceeding 350 °C. Integrating these systems into perovskite solar cells results in outstanding power conversion efficiency (PCE), with TM-02-based devices exhibiting a PCE of 20.26%. The devices base on TM-01, TM-03, and TM-04 achieve PCE values of 16.98%, 17.58%, and 18.80%, respectively. The long-term stability of these devices is measured for 600 h, with initial efficiency retention between 94% and 86%. The TM-04-based device presents noticeable stability of 94%, better than the reference polymer PTAA with 91%. These findings highlight the exciting potential of dumbbell-shaped systems based on PAHs-BODIPY-triarylamine derivatives for next-generation photovoltaics.     

Improved formulas for velocity,acceleration, and projection angle of explosively driven liners

Improved one-dimensional formulas for both the direction and magnitude of the velocity of explosively driven liners are developed. First, an analytical formula for the direction of motion of the liner under unsteady conditions is derived. This new formula is compared with both two-dimensional calculations and experimental data for both shaped-charge and exploding cylinder geometries. The new formula is more accurate than the classical steady-state Taylor-angle formula for these cases. Next, for implosive geometries, a new formula for the fully accelerated liner velocity is given. Since the standard Gurney approach does not apply to imploding geometries, a modified approach was adopted. Results agree well with two-dimensional code results for a wide range of explosives and geometries. Also, the velocity history is shown to follow an exponential law, and a useful formula for characteristic metal acceleration time was developed.     

Facile Production of the Pseudomonas aeruginosa Virulence Factor LasB in Escherichia coli for Structure-Based Drug Design

The human pathogen Pseudomonas aeruginosa has a number of virulence factors at its disposal that play crucial roles in the progression of infection. LasB is one of the major virulence factors and exerts its effects through elastolytic and proteolytic activities aimed at dissolving connective tissue and inactivating host defense proteins. LasB is of great interest for the development of novel pathoblockers to temper the virulence, but access has thus far largely been limited to protein isolated from Pseudomonas cultures. Here, we describe a new protocol for high-level production of native LasB in Escherichia coli. We demonstrate that this facile approach is suitable for the production of mutant, thus far inaccessible LasB variants, and characterize the proteins biochemically and structurally. We expect that easy access to LasB will accelerate the development of inhibitors for this important virulence factor.     

Targeting the IspD Enzyme in the MEP Pathway: Identification of a Novel Fragment Class

The enzymes of the 2-C-methylerythritol-d -erythritol 4-phosphate (MEP) pathway (MEP pathway or non-mevalonate pathway) are responsible for the synthesis of universal precursors of the large and structurally diverse family of isoprenoids. This pathway is absent in humans, but present in many pathogenic organisms and plants, making it an attractive source of drug targets. Here, we present a high-throughput screening approach that led to the discovery of a novel fragment hit active against the third enzyme of the MEP pathway, PfIspD. A systematic SAR investigation afforded a novel chemical structure with a balanced activity–stability profile ( 16 ). Using a homology model of PfIspD, we proposed a putative binding mode for our newly identified inhibitors that sets the stage for structure-guided optimization.     

Improved Gurney Formulas for Exploding Cylinders and Spheres using “Hard Core” Approximation

The final liner velocity predicted by the Gurney formulas for sandwich cylindrical and spherical configurations for very light liners (small M/C values) are (6E)^1/2, (4E)^1/2 and (10E/3)^1/2 respectively. The existance of these differences among the limiting velocity values contradicts the well known fact that the explosive products' escape velocity does not depend on the initial geometry of the explosive when no Mach waves are formed. An improvement to the Gurney formulas for exploding cylinders and spheres is suggested which corrects this basic inconsistancy. It is based on the observation that light liners are accelerated to their final velocity in a short time getting their kinetic energy mainly from that part of the explosive which is in contact with them. It is shown that by excluding from the explosive mass the inner volume and replacing it with an infinitely hard core the experimentally measured liner velocities for the cylindrical and spherical geometrics are more accurately reproduced. The core radius is found by maximizing the liner velocity, thus getting the fastest transformation of the gas potential energy to kinetic energy which is possible within the model assumptions. The improved formulas predict for the limit of very small M/C the same velocity, (6E)^1/2 for all the above mentioned geometries. The comparison of the improved formulas with available experimental data reveals how the accuracy of the Gurney model is limited at the large and the small values of M/C.     

From P-type to N-type: Peripheral fluorination of axially substituted silicon phthalocyanines enables fine tuning of charge transport

Silicon phthalocyanines (R₂-SiPcs) are a family of promising tunable materials for organic electronic applications. We report the chemistry of the synthesis of axially substituted fluorinated SiPcs (tb-Ph)₂-F_xSiPc (where X = 0, 4, 8, or 16) and explore how the degree of fluorination effects optical and electronic properties. A new treatment with boron trichloride was included to obtain Cl₂-F_XSiPcs from F₂-F_XSiPcs, activating the axial position for further functionalization. We observed that as the degree of fluorination increased, so did the electron affinity of the compounds, leading to a drop in frontier orbital levels, as measured by electrochemistry and ultraviolet photoelectron spectroscopy (UPS). The deeper energy levels enabled successful (tb-Ph)₂-F₄SiPc and poly [[6,7-difluoro[(2-hexyldecyl)oxy]-[5,8-quinoxalinediyl]-2,5-thiophenediyl]] (PTQ10) blends for organic photovoltaics and photodetectors. All four compounds were incorporated in organic thin-film transistors (OTFTs), where the degree of fluorination influenced device operation, changing it from p-type conduction for (tb-Ph)₂-F₀SiPc, to ambipolar for (tb-Ph)₂-F₄SiPc, and n-type for (tb-Ph)₂-F₈SiPc and (tb-Ph)₂-F₁₆SiPc. The OTFT devices made with (tb-Ph)₂-F₁₆SiPc achieved a low average threshold voltage of 7.0 V in N₂ and retained its n-type mobility when exposed to air.     

Additive Manufacturing of Porous Biominerals

Nature fabricates hard functional materials from soft organic scaffolds that are mineralized. To enable an energy-efficient locomotion of these creatures while maintaining their structural stability, nature often renders parts of these minerals porous. Unfortunately, methods to produce synthetic minerals with a similar degree of control over their multi length scale porous structure remain elusive. This level of control, however, would be required to design lightweight yet robust biominerals. Here, a room temperature process is presented that combines a localized mineralization with emulsion-based 3D printing to form cm sized biominerals possessing pores whose diameters range from the 100 s of nm up to the mm length scale. The samples encompass up to 80 wt% of CaCO₃ and display a specific compressive strength that is significantly higher than that of previously reported 3D printed porous biominerals and close to those of trabecular bones. The universality of this approach by forming different types of bioactive minerals, including calcite, aragonite, and brushite is demonstrated. The ability to 3D print these materials under benign conditions renders this energy-efficient process well-suited to construct cm-sized lightweight yet load-bearing structures that might find applications, for example, in the design of the next generation of flying or motile objects.     

A model explaining the Rule for Calculating the Break-up Time of homogeneous ductile metals

It was shown in a previous paper⁽¹⁾ that the break-up time of homogenious ductile metals which elongate due to explosions, is equal to the sample's smallest initial dimension (thickness) divided by the velocity V_pl which characterizes the metal. It is attempted to explain this rule by suggesting a break-up mechanism where holes caused by a pile-up of vacancies are formed at the metal surface and gradually increase until breaking it. This model also predicts the existence of a strain rate threshold below which other mechanisms dominate the break-up process. Its validity is supported by experimental evidence which is also presented.