Packing Behavior Research Articles

Influence of halogen substitution on crystal packing, molecular properties and electrochemical sensing

Halogen atoms are commonly present in organic molecules and halogen functionalization is of great significance in organic synthesis, to achieve desired material and biological functions. In crystal engineering, the halogen bond is an intriguing interaction utilized to design molecular solids. Herein we report the development of halogen functional red tri-halo Schiff bases/Anils 1–4 in which the nature of halogen atoms is rationally changed, to explore the impact of halogen atoms on molecular packing and physicochemical properties. The trichloro (1), tribromo (2) and triiodo (3) Anils crystallize in the same centrosymmetric triclinic crystal systems and the 2 and 3 are isomorphous. The molecular solids exhibit similar 2-dimensional packing induced by halogen atoms, however, the molecules differ significantly in the third-dimensional packing propagated by π-stackings. It is observed that π-π interactions are stronger in triiodo Anil. To further understand the effect of the nature of halogen on molecular packing a mixed dichloro-iodo Anil (4) was synthesized. The introduction of different halogens on the Anil skeleton greatly alters the packing behavior and the molecules pack in monoclinic P21/n space group. 4 undergoes halogen bonded interactions to arrange as zig-zag solid, further stabilized by π-stackings. The Hirshfeld studies validate the formation of a significant sigma hole on a para-iodine atom in 3 (0.0161 a.u), while the tip of p-chlorine in 1 is not electron-deficient (−0.0128 a.u.), which also reflects in more contribution of halogen-halogen interactions in 3 than 1 and 2, in their fingerprint plots. Theoretical and experimental studies indicate lower band gap values in triiodo form 3 than others. The framework analyses of the molecular solids indicate nature of intermolecular contacts is predominantly dispersive. The physicochemical property investigation of the Anils validates relatively better chemical and thermal stability and optical properties of the trihalo form. Solubility studies of the molecular solids 1–4 validate their hydrophobic nature and the iodo functional groups enhance the hydrophobicity of the molecules, while the solubility investigations of these solids in DCM and toluene indicate higher solubilities with relatively lower values for iodo-functionalized molecules. The molecular solids have been employed for electrochemical sensing of picric acid with the limit of the detection value of 0.72, 0.84, 0.74 and0.73 ​μM for 1–4, respectively.

A Resonating B, N Covalent Bond and Coordination Bond in Aromatic Compounds and Conjugated Polymers.

We herein report an organoboron compound (SBN-1) based on N-B←N units with a balanced resonance hybrid of B, N single bond (B-N) and B, N coordination bond (B←N). Despite the different chemical environments of the two nitrogen atoms in the N-B←N unit, the single-crystal structure reveals that the two B, N bonds have similar bond lengths of ca. 1.55 Å and are almost equivalent. The resonance nature of the two B, N bonds contributes to the excellent chemical stability and photostability of SBN-1. The N-B←N units in SBN-1 show a strong electron-withdrawing capability and large dipole, resulting in a red-shifted absorption spectrum, downshifted LUMO/HOMO energy levels, and drastically altered molecular packing behaviors in solid state. SBN-1 can be used as a building block to construct small band gap conjugated polymers. The resonance of B, N bonds discovered in this work provides new insight into the design of stable organoboron small molecules and polymers for practical applications.

A Resonating B, N Covalent Bond and Coordination Bond in Aromatic Compounds and Conjugated Polymers

AbstractWe herein report an organoboron compound (SBN‐1) based on N−B←N units with a balanced resonance hybrid of B, N single bond (B−N) and B, N coordination bond (B←N). Despite the different chemical environments of the two nitrogen atoms in the N−B←N unit, the single‐crystal structure reveals that the two B, N bonds have similar bond lengths of ca. 1.55 Å and are almost equivalent. The resonance nature of the two B, N bonds contributes to the excellent chemical stability and photostability ofSBN‐1. The N−B←N units inSBN‐1show a strong electron‐withdrawing capability and large dipole, resulting in a red‐shifted absorption spectrum, downshifted LUMO/HOMO energy levels, and drastically altered molecular packing behaviors in solid state.SBN‐1can be used as a building block to construct small band gap conjugated polymers. The resonance of B, N bonds discovered in this work provides new insight into the design of stable organoboron small molecules and polymers for practical applications.

PDMS thin-film composite membrane fabricated by ultraviolet crosslinking acryloyloxy-terminated monomers

Polydimethylsiloxane (PDMS), as a representative membrane material with superior permeability, attracts great attention in gas separation, pervaporation and nanofiltration. However, the fabrication of defect-free ultrathin PDMS membrane remains great challenge mainly due to the difficulty in controlling the processability and substrate pore penetration of casting solution. In this work, for the first time, we employed PDMS monomer terminated with acryloyloxy groups (AC-PDMS) to implement fabrication of thin-film composite (TFC) membrane. The ultraviolet (UV) reactivity between acryloyloxy groups induced fast curing of AC-PDMS casting solution, thereby realizing formation of ultrathin selective layer (∼260 nm) and inhibition of substrate pore penetration. By optimizing the UV wavelength, irradiation time and polymer concentration, the resulting AC-PDMS TFC membrane achieved attractive CO2 permeance of 9635 GPU, with CO2/N2 selectivity of 11.5. Furthermore, chain crosslinking and packing behavior, fabrication of TFC membrane and transport property of AC-PDMS were compared with conventional hydroxyl-terminated PDMS (OH-PDMS). Together with the potential in scalable fabrication, the strategy based on UV crosslinking acryloyloxy-terminated monomers provides a new avenue to produce ultrathin PDMS membranes toward practical application in molecular separation.

Molecular Packing and Charge Transport Behaviors of Semiconducting Polymers Over a Wide Temperature Range

AbstractThe molecular packing and resultant charge transport behaviors of semiconducting polymers are widely known to be temperature‐dependent. Due to the limitation of measurement methods, previous studies on molecular packing behavior have been mainly focused on a very limited temperature range, and therefore cannot support the understanding of charge transport behaviors. In this study, with a homemade temperature‐dependent grazing incidence XRD measurement chamber, the relationship between molecular packing structure and charge transport properties of diketopyrrolopyrrole‐based polymers is investigated across a wide temperature range of 98–623 K. Glass transition temperatures of the alkyl side‐chain and aromatic backbone are identified through the observation of clear transitions in the thermal expansion coefficients of d−d packing and π−π stacking, respectively. A correlation between the π−π stacking distance and charge transport properties is then established using an extended Miller−Abrahams model. The turning point of the charge transport and the failure of the polymer‐based devices are proved to be caused by packing structure changes due to increased temperatures. Such an examination over a wide range of temperatures improves the understanding of the charge transport properties of semiconducting polymers and helps construct thermally stable devices to be used in extreme conditions.

Conformation and structure of ring polymers in semidilute solutions: A molecular dynamics simulation study

Scaling is one of the most fundamental concepts in theoretical polymer physics. For linear polymers in semidilute solutions under a good solvent condition, there has been a well established scaling behavior of mean-square radius of gyration of chains with the concentration, i.e., R g 2 ~ ϕ β , with β = −0.25, which receives strong support from experiments, computer simulations and scaling arguments. However, a clear-cut conclusion about the scaling behavior of dimensions of nonconcatenated and unknotted ring polymers in the semidilute solution with the concentration has not been achieved. Values of the corresponding scaling exponent β are diversely reported in literature, ranging from −0.25 to −0.59 and in contradiction within experimental, simulation and theoretical studies. As an endeavour for clarifying this issue, we carried out extensive molecular dynamics (MD) simulations based on the Kremer-Grest model of ring polymers with chain lengths N up to 5120 in semidilute solutions, and compared our results about ring conformations with almost all of experimental, simulation and theoretical data available in literature. Our MD simulation results lead to a conclusion that the mean-square radius of gyration of ring polymers scales with the concentration in semidilute regime as R g 2 ∼ φ − 0.59 ± 0.01 . This conclusion is in a good agreement with a previous finding by a lattice Monte Carlo simulation. Surprisingly, by looking into the experimental and other simulation results reported previously with sufficient caution, we tend to conclude that in reality almost all of their data can be described reasonably well by the same scaling law, R g 2 ~ ϕ − 0.59 . Furthermore, the scaling exponent obtained (−0.59) can be successfully explained by a scaling argument based on concept of correlation length. Finally, effects of the concentration on shape properties and packing behavior of ring polymers in the semidilute solutions have also been illuminated within our MD simulations. • Scaling behavior of ring dimensions in semidilute solutions with the concentration has been revisited. • Comparison of our results with experimental, and other simulation and theoretical results has been conducted. • Effect of concentration on shape and packing behavior of ring polymers in semidilute solutions has been illuminated.

Surface chemical and geometrical properties of pure copper powder intended for binder jetting and sintering

One novel important application of sinter‐based additive manufacturing involving binder jetting is copper‐based products. Three different variants of nominally pure copper powder having particle size distributions with D90 < 16, 22, or 31 μm were investigated in this study. The packing behavior and the flow properties using dynamic test and shear cell, as well as specific surface area were evaluated. The analyses employed illustrate the multidimensional complexity. Because different measurements capture different aspect of the powder, it is imperative to apply a characterization approach involving different methods. Surface chemical analysis by means of X‐ray photoelectron spectroscopy (XPS) showed that all powder variants were covered by Cu2O, CuO, and Cu (OH)2, with Cu2O being dominant in all cases. The finest powder with D90 < 16 μm tended to have higher relative amount of copper in divalent state. The average apparent oxide thickness estimated by XPS depth profiling showed that the two coarser variants had similar overall average oxide thickness, whereas the finest one possessed smaller oxide thickness. The surface chemistry of the powder grades is found to be related to their rheological behavior in dynamic condition. Considering the specific surface areas in combination with the average oxide thicknesses, the amount of surface bound oxygen was estimated to be about ~220 ppm for all three variants. Specific concerns need to be taken during the sintering of powder to keep oxygen level below that of electrolytic pitch copper (400 ppm).

Mechanistic Study of Controlled Zinc Electrodeposition Behaviors Facilitated by Nanoscale Electrolyte Additives at the Electrode Interface.

Nanoparticle organic hybrid materials (NOHMs) are liquid-like materials composed of an inorganic core to which a polymeric canopy is ionically tethered. NOHMs have unique properties including negligible vapor pressure, high oxidative thermal stability, and the ability to bind to reactive species of interest due to the tunability of their polymeric canopy. This makes them promising multifunctional materials for a wide range of energy and environmental technologies, including electrolyte additives for electrochemical energy storage (e.g., flow batteries) and the electrochemical conversion of CO2 to chemicals and fuels. Due to their unique transport behaviors in fluid systems, an understanding of the near-electrode surface behavior of NOHMs in electrolyte solutions and their effect on electrochemical reactions is still lacking. In this work, the complexation of zinc (Zn) by NOHMs with an ionically tethered polyetheramine canopy (HPE) (NOHM-I-HPE) was studied using attenuated total reflectance Fourier transform infrared and Carbon-13 nuclear magnetic resonance spectroscopy. Additionally, various electrochemical techniques were employed to discern the role of NOHM-I-HPE during zinc electrodeposition, and the results were compared to those of the electrochemical system containing untethered HPE polymers. Our findings confirmed that NOHM-I-HPE and HPE reversibly complex zinc in the aqueous electrolyte. NOHM-I-HPE and HPE were found to block some of the electrode active sites, reducing the overall current density during electrodeposition, while facilitating the formation of smooth zinc deposits, as revealed by surface imaging and diffraction techniques. Observed variations in the current density responses and the degree of passivation created by the NOHM-I-HPE and HPE adsorbed on the electrode surface revealed that their different packing behaviors at the electrode-electrolyte interface influence the zinc deposition mechanism. The presence of the nanoparticle and ordering offered by the NOHMs as well as the structured conformation of the polymeric canopy allowed the formation of void spaces and free volumes for enhanced transport behaviors. These findings provided insights into how structured electrolyte additives such as NOHMs can allow for advancements in electrolyte design for controlled deposition of metal species from energy-dense electrolytes or for other electrochemical reactions.

A simple high-performance fully nonfused ring electron acceptor with a planar molecular backbone

We designed two simple fully nonfused ring electron acceptors 4T-OEH and 4T-EH with 3,4-bis(alkoxy)thiophene and 3,4-dialkylthiophene π-bridge units, respectively, which can be modularly synthesized with only four high-yield steps. With the help of intramolecular S-O noncovalent interaction, 4T-OEH tends to form a planar molecular backbone, which is beneficial for the electron delocalization and charge transport. Besides, the neat 4T-OEH film displays a more ordered molecular packing and obviously red-shifted absorption after thermal annealing. Compared with 4T-EH, 4T-OEH based devices can form more homogenous phase morphology, higher and more balanced hole and electron mobilities. The optimal OSCs based on 4T-OEH can generate an excellent PCE of 12.12%, which is much higher than 4T-OEH based ones (7.36%). It is worth noting that the figure-of-merit values of 4T-OEH is much higher than the star acceptors (ITIC and Y6), demonstrating its high potential for future practical application. Our work has demonstrated that we can tune the backbone planarity, solubility and packing behavior of acceptor molecules via optimizing their lateral substituents to obtain high efficiency and low-cost fully nonfused ring electron acceptors.

Roles of particle packing and water coating thickness in carbonation and strength of γ-dicalcium silicate-based low carbon materials

In this work, a low carbon material of γ-dicalcium silicate (γ-C2S) was examined, with an emphasis on the properties influenced by its particle packing and water coating thickness (WCT). Differences in morphology and reactivity from that of cement particles render γ-C2S particles have different particle packing behavior and water film surrounding each particle. However, limited research has been conducted on it to deepen the understanding of γ-C2S-based materials. To fill this gap, the wet packing density of γ-C2S particles was measured and the WCT was varied at different water to solid ratios. At each WCT, the carbonated γ-C2S samples were characterized by techniques of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) consistently. Experimental results revealed little early strength gain when the WCT exceeded a certain value. Moreover, a critical carbonation depth was identified. Below the critical depth, the amounts and characteristics of carbonation products dominated, whilst above the critical depth, the strength gain was influenced by CO2 diffusion rate. An optimal WCT exists for achieving the highest strength and CO2 uptake. This work shall advance the development of low carbon γ-C2S-based materials from the perspective of particle packing.

Enhancing the Intermolecular Interactions of Ladder-Type Heteroheptacene-Based Nonfullerene Acceptors for Efficient Polymer Solar Cells by Incorporating Asymmetric Side Chains

Enhancing the Intermolecular Interactions of Ladder-Type Heteroheptacene-Based Nonfullerene Acceptors for Efficient Polymer Solar Cells by Incorporating Asymmetric Side Chains

CT-based method to measure metal powder characteristics and to study their influence on the quality of additively manufactured parts

Laser powder bed fusion (LPBF) is increasingly used to produce metal industrial components for high value-added sectors, such as aerospace, automotive and biomedical. However, mechanical and structural properties of LPBF parts are often hindered by the large quality variability, poor geometrical and dimensional characteristics, complex surface texture and low density. The quality of the feedstock material is an important aspect to be taken into account, as it significantly influences such possible issues. In particular, metal powder used in LPBF should have shape and size distribution designed to facilitate good flowability, spreading and packing behaviour, so that the final fabricated parts have acceptable density, surface finish and mechanical properties. This work focuses on the accuracy of simultaneous measurement of powder size and shape from three-dimensional reconstructions obtained by X-ray computed tomography (CT). Results of CT measurements are compared with results from other methods based on laser diffraction and scanning electron microscopy. Different materials and powder morphologies were investigated. In addition, the CT-measured powder characteristics can be used to improve other CT analyses of LPBF parts.

Metal-Organic Framework (MOF) Morphology Control by Design.

Exerting morphological control over metal‐organic frameworks (MOFs) is critical for determining their catalytic performance and to optimize their packing behavior in areas from separations to fuel gas storage. A mechanism‐based approach to tailor the morphology of MOFs is introduced and experimentally demonstrated for five cubic Zn4O‐based MOFs. This methodology provides three key features: 1) computational screening for selection of appropriate additives to change crystal morphology based on knowledge of the crystal structure alone; 2) use of additive to metal cluster geometric relationships to achieve morphologies expressing desired crystallographic facets; 3) potential for suppression of interpenetration for certain phases.

Collective cell behaviors manipulated by synthetic DNA nanostructures

Cellular collective motion in confluent epithelial monolayers is involved in many processes such as embryo development, carcinoma invasion, and wound healing. The development of new chemical strategies to achieve large-scale control of cells’ collective motion is essential for biomedical applications. Here a series of DNA nanostructures with different dimensions were synthesized and their influences on cells’ collective migration and packing behaviors in epithelial monolayers were investigated. We found that the framed DNA nanoassemblies effectively reduced the cells’ speed by increasing the rigidity of cells, while the lipid-DNA micelles had a more pronounced effect on cells’ projection area and shape factor. These DNA nanostructures all significantly enhanced the dependence of cells’ speed on their shape factor. Our results indicate that cells’ mobility in monolayers can be manipulated by chemical intercellular interactions without any genetic intervention. This may provide a new chemical strategy for tissue engineering and tumor therapy.

Characterization of void space, large-scale structure, and transport properties of maximally random jammed packings of superballs

Dense, disordered packings of particles are useful models of low-temperature amorphous phases of matter, biological systems, granular media, and colloidal systems. The study of dense packings of nonspherical particles enables one to ascertain how rotational degrees of freedom affect packing behavior. Here, we study superballs, a large family of deformations of the sphere, defined in three dimensions by $|{x}_{1}{|}^{2p}+|{x}_{2}{|}^{2p}+{|{x}_{3}|}^{2p}\ensuremath{\le}1$, where $p\ensuremath{\in}(0,\ensuremath{\infty})$ is a deformation parameter indicating to what extent the shape deviates from a sphere. As $p$ increases from the sphere point ($p=1$), the superball tends to a cuboidal shape and approaches a cube in the $p\ensuremath{\rightarrow}\ensuremath{\infty}$ limit. As $p\ensuremath{\rightarrow}0.5$, it approaches an octahedron, becomes a concave body with octahedral symmetry for $p<0.5$, and approaches a three-dimensional cross in the limit $p\ensuremath{\rightarrow}0$. Previous characterization of superball packings has shown that they have a maximally random jammed (MRJ) state, whose properties (e.g., packing fraction $\ensuremath{\phi}$, average contact number $\overline{Z}$) vary nonanalytically as $p$ diverges from unity. Here, we use an event-driven molecular dynamics algorithm to produce MRJ superball packings with $0.85\ensuremath{\le}p\ensuremath{\le}1.50$. To supplement the previous work on such packings, we characterize their large-scale structure by examining the behaviors of their structure factors $S(Q)$ and spectral densities ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{{}_{V}}(Q)$, as the wave number $Q$ tends to zero, and find that these packings are effectively hyperuniform for all values of $p$ examined. We show that the mean width $\overline{w}$ is a useful length scale to make distances dimensionless in order to compare systematically superballs of different shape. Moreover, we compute the complementary cumulative pore-size distribution $F(\ensuremath{\delta})$ and find that the pore sizes tend to decrease as $|1\ensuremath{-}p|$ increases. From $F(\ensuremath{\delta})$, we estimate how the fluid permeability, mean survival time, and principal diffusion relaxation time vary as a function of $p$. Additionally, we compute the diffusion ``spreadability'' $\mathcal{S}(t)$ [Torquato, Phys. Rev. E 104, 054102 (2021)] of these packings and find that the long-time power-law scaling indicates these packings are hyperuniform with a small-$Q$ power law scaling of the spectral density ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\chi}}}_{{}_{V}}(Q)\ensuremath{\sim}{Q}^{\ensuremath{\alpha}}$ with an exponent $\ensuremath{\alpha}$ that ranges from 0.64 at the sphere point to 0.32 at $p=1.50$, and decreases as $|1\ensuremath{-}p|$ increases. Each of the structural characteristics computed here exhibits an extremum at the sphere point and varies nonanalytically as $p$ departs the sphere point. We find the nonanalytic behavior in $\ensuremath{\phi}$ on either side of the sphere point is nearly linear, and determine that the rattler fraction ${\ensuremath{\phi}}_{R}$ decreases rapidly as $|1\ensuremath{-}p|$ increases. Our results can be used to help inform the design of colloidal or granular materials with targeted densities and transport properties.

Terminal alkyl chain tuning of small molecule donor enables optimized morphology and efficient all-small-molecule organic solar cells

Modulation of the interfacial molecular orientation and molecular packing behaviour is essential for fine-tuning the nanoscale morphology toward efficient non-fullerene all-small-molecule organic solar cells (NFSM-OSCs) due to the anisotropic molecular structure of electron donors (D) and acceptors (A). Currently, the design of active-layer material to obtain favourable nanoscale morphology is still quite challenging. This work developed four new small molecular donors, TBCA-CX (X = 2, 4, 6, and 8), with the same conjugated skeleton but different terminal alkyl chains. The GIWAXS measurement results reveal that the predominant molecular orientation of pristine TBCA-CX films began to change from edge-on to face-on with the increased terminal alkyl chains length. Furthermore, the non-fullerene acceptor IT-4F was used to fabricate NFSM-OSCs with the new donor compounds. Finally, the TBCA-C4: IT-4F blend formed a more favourable face-to-face orientation at the D/A interface and a more compact molecular stacking as proved from GIWAXS characterization, which is beneficial for charge transfer and charge carrier transport. As a result, the TBCA-C4-based device exhibited a higher power conversion efficiency (PCE) of 9.21%, while its analogs showed PCEs less than 8%. These results provide an insight to understand the impact of molecular design of interfacial molecular orientation and molecular packing behaviour on photovoltaic performance in NFSM-OSCs.

Fluidity is the way to life: lipid phase separation in bacterial membranes.

A hallmark of biological membranes is the dynamic localization of lipids and proteins. Lipids respond to temperature reduction below a critical point with phase separation, and poikilothermic animals and also bacteria adapt their lipid content to prevent gel phase formation in membranes. In a new study, Gohrbandt etal (2022) show that reduced membrane fluidity in bacterial cells causes reversible phase separation without membrane rupture invivo, highlighting the physical robustness of biological membranes.

High‐Performance All‐Small‐Molecule Organic Solar Cells Enabled by Regio‐Isomerization of Noncovalently Conformational Locks

AbstractThe power conversion efficiencies (PCEs) of organic solar cells (OSCs) have surpassed 19% thanks to the innovation of polymer donors and molecular acceptors. However, the batch‐to‐batch variations in polymer materials are detrimental to the reproducibility of the device performance. In comparison, small‐molecule donors (SMDs) possess some unique advantages, such as well‐defined molecular weights, easy purification, and excellent batch‐to‐batch repeatability. Herein, a pair of regioisomeric SMDs (BT‐O1 and BT‐O2) has been synthesized with alkoxy groups as S···O noncovalently conformational locks (NoCLs) at the inner and outer position, respectively. Theoretical and experimental results reveal that the regioisomeric effect has a significant influence on the light‐harvest ability, energy levels, molecular geometries, internal reorganization energy, and packing behaviors for the two SMDs. As a result, BT‐O2‐based binary device shows an impressive PCE of 13.99%, much higher than that of BT‐O1 based one (4.07%), due to the better‐aligned energy level, more balanced charge transport, less charge recombination, lower energy loss, and more favorable phase separation. Furthermore, the fullerene derivative PC71BM is introduced into BT‐O2:H3 as the third component to achieve a notable PCE of 15.34% (certified 14.6%). Overall, this work reveals that NoCLs is a promising strategy to achieve high‐performance SMDs for all‐small‐molecule OSCs.

Molecular Engineering Enables TADF Emitters Well Suitable for Non‐Doped OLEDs with External Quantum Efficiency of Nearly 30%

AbstractNon‐doped organic light‐emitting diodes (OLEDs) are particularly appealing due to the merit of the extremely simple device structure. However, the performance of non‐doped OLEDs is usually far inferior than that of doped devices, mainly due to the lack of desirable emitters. An ideal emitter for non‐doped OLEDs should not merely be highly emissive in the host matrix but also be capable of delivering excellent properties in its condensed state. Herein, through molecular engineering, an “axial and equatorial carbazolyl extension” approach to manipulate the molecular packing behavior is developed, and thus, the emitter is awarded with superior properties in its neat film. Based on this approach, through simply modifying the conventional acridine donor in a thermally activated delayed fluorescence (TADF) emitter with carbazole moieties in the way of hyper‐conjugation, two new TADF emitters with the molecular skeleton being extended both horizontally and vertically by carbazole moieties are constructed. The resulted TADF emitters reveal superb properties with simultaneous excellent thermal and morphological stabilities, photophysical behaviors, and charge transporting ability in their neat film. Owing to the merits of these synergistic superior properties, highly efficient non‐doped green emissive OLED with the state‐of‐the‐art external quantum efficiency of nearly 30% is realized.

Tessellation based quantitative framework for the spatial analysis of subcellular structures

A cell exhibits microtubule-motor-dependent spatiotemporal organization of its subcellular structures. Previously, we observed self-organized asters in the ooplasm enclosed within hexagon dominant polygonal domains similar to the cell packing in epithelial tissues. However, an active, non-crystalline and crowded cell often deviates from an ideal packing behaviour. Here, we discuss the image analysis pipeline and the geometric method to characterize the features of the spatial organization. The algorithm automatically (or user-defined) detects the aster centers that serve as seed points for Voronoi tessellations.