Low-energy Absorption Research Articles

Synthesis and Chiroptical Activity of π-Expanded Electron-rich Heterohelicenes Based on the 1,4-Dihydropyrrolo[3,2-b]pyrrole core.

Herein, we report the synthesis and chiroptical characteristics of the first (double) helicenes possesing the 1,4-dihydropyrrolo[3,2-b]pyrrole (DHPP) moiety as their central core. We have developed a three-step synthesis with 6π-electrocyclization accompanied with HBr elimination as its key step. We found that, whereas for smaller periphereal arms double 6π-electrocyclization occurs smoothly forming a double helicene, in the case of longer policyclic aromatic hydrocarbons the reaction becomes less efficient and mono-helicenes are the only products. An analysis of the electron density distribution of LUMO explains the different regioselectivity of 6π-electrocyclization. The synthesized heterohelicenes are characterized by greenish blue emission, distinct solvatofluorochromism and good fluorescence quantum yields (up to 42%). Moreover, the chiralooptical measurements reveal that unsymmetrical double heterohelicene exhibits excellent circularly polarized luminescence brightness (BCPL) reaching 30 M-1·cm-1. The combined experimental and computational study has revealed that a charge-transfer state is responsible for the observed emission (hence the solvatochromism), while low-energy absorption derives from multiple transitions.

Impact of the Acceptor Group on the Properties of Triphenylamine-Donor-Acceptor Dyes: An Experimental and Computational Study.

Three triphenylamine-Indane donor-acceptor dyes with different functional groups on the acceptor were studied to investigate how substitution would affect the optical properties. The dyes studied were IndCN, containing two malononitrile groups; InO, with two ketone groups; and InOCN, which features mixed functional groups. A combination of Raman spectroscopy, UV-vis absorption and emission spectroscopy, and density functional theory (DFT) calculations were employed for characterization. The dyes exhibited intramolecular charge transfer transitions with relatively high molar absorptivity (εabs) of ∼50 mM-1 cm-1 at 491-591 nm within the visible spectrum and emissions at 690-840 nm in dichloromethane. The malononitrile-containing dyes showed lower-energy absorption and emissions due to a reduced band gap compared to ketone-containing dyes. The bulkiness of the malononitrile group led to a bent geometry, increasing nonradiative decay and reducing the fluorescence quantum yield. The dyes exhibited fluorescence quantum yields less than 0.25 and lifetimes of ∼5 ns. Resonance Raman spectra and DFT calculations showed that the longer linker group (propen-1-ylidene linker) in these systems reduced the charge-transfer character of the optical transition. The emission intensities of the three dyes were temperature-sensitive, with ketone-containing dyes showing shifts in emission bands as well. This could be due to molecular stacking and intermolecular π-interactions.

High-Density Lead Germanate Glasses with Enhanced Gamma and Neutron Shielding Performance: Impact of PbO Concentration on Attenuation Properties

Lead germanate glasses, improved with lead oxide (PbO), have emerged as effective materials for radiation shielding due to their increased density and structural robustness. The goal of this study is to find out how well lead germanate glasses with PbO concentrations between 20 and 55 mol% can block gamma rays and neutrons. The Phy-X/PSD software was used to obtain important numbers like the mass attenuation coefficient (MAC), the linear attenuation coefficient (LAC), the half-value layer (HVL), the mean free path (MFP), and the fast neutron removal cross section (FNRCS). The results show that the 55PbGe sample, which has the most PbO, has better gamma-ray attenuation and a low energy absorption buildup factor (EABF). This makes it a good choice option for locations requiring compact but efficient radiation shielding. The 50PbGe sample, on the other hand, demonstrates effective neutron shielding capabilities, suggesting it may be suitable for applications requiring protection against both gamma and neutron exposure. Higher PbO content is linked to better radiation blocking, which supports the idea that lead germanate glasses could be used instead of traditional lead-based shielding materials.

Experimental Analysis of Hybrid Panels Combining Flax/PLA Composite with UHMWPE and Steel Under Ballistic Impact

ABSTRACT This study investigates the feasibility of substituting UHMWPE and steel with flax/PLA green composite in ballistic applications with the objective to increase sustainability and cost-effectiveness. Results reveal that flax/PLA composite exhibits significantly lower ballistic performance than UHMWPE due to its lower energy absorption capacity. However, hybrid panels where 33% of UHMWPE was replaced by biocomposite showed similar values of V50 than homogenous UHMWPE, suggesting potential for partial replacement without compromising ballistic performance. However, the hybrid panels of biocomposite and steel showed a ballistic limit much lower than pure steel. Analysis of scan results indicates distinct failure modes: UHMWPE exhibits viscoelastic deformation, biocomposites show local damage failure, and steel displays ductile behavior. These findings provide insights into the viability of hybridizing UHMWPE with biocomposites for eco-friendly ballistic applications.

Fluorenyl Radicals Stabilized by Donor‐π‐Radical Conjugation between Nitrogen Atoms and Carbon Radicals

Comprehensive SummaryA design strategy towards stable fluorenyl radicals (FRs) has been developed through introducing donor‐π‐radical (D‐π‐R) conjugation, facilitated by the linkage of amine N atoms and FR centers via phenyl or 9‐anthryl moieties. Four FRs, with or without N atom containing protecting groups, were designed and synthesized for comparative analysis. X‐ray crystallographic studies revealed the planar fluorenyl skeletons of CDP‐FR and MA‐FR, which exhibit significant dihedral angles relative to their protecting groups. Wiberg bond‐order analysis and natural bond orbital analysis conducted on the C‐C and C‐N bond between the radical center and N atoms in all FRs clearly demonstrated the presence of D‐π‐R conjugation. Furthermore, time‐dependent DFT calculations, based on frontier molecular orbital analysis, highlighted the contribution of D‐π‐R structures as donor‐acceptor effect on the lowest energy absorptions of carbazole and diphenylamine substituted CDP‐FR and DPAA‐FR, which would promote charge transfer process and inhibit the photodegradation reaction. Consequently, beneficial from D‐π‐R conjugations, CDP‐FR and DPAA‐FR exhibited superior photostability compared to TP‐FR and MA‐FR. Our study offers a new strategy for the design and synthesis of persistent stable monoradicals.

Unlocking high-performance near-infrared photodetection: polaron-assisted organic integer charge transfer hybrids

Room temperature femtowatt sensitivity remains a sought-after attribute, even among commercial inorganic infrared (IR) photodetectors (PDs). While organic IR PDs are poised to emerge as a pivotal sensor technology in the forthcoming Fourth-Generation Industrial Era, their performance lags behind that of their inorganic counterparts. This discrepancy primarily stems from poor external quantum efficiencies (EQE), driven by inadequate exciton dissociation (high exciton binding energy) within organic IR materials, exacerbated by pronounced non-radiative recombination at narrow bandgaps. Here, we unveil a high-performance organic Near-IR (NIR) PD via integer charge transfer between Poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (C-14PBTTT) donor (D) and Tetrafluorotetracyanoquinodimethane (TCNQF4) acceptor (A) molecules, showcasing strong low-energy subgap absorptions up to 2.5 µm. We observe that specifically, polaron excitation in these radical and neutral D-A blended molecules enables bound charges to exceed the Coulombic attraction to their counterions, leading to an elevated EQE (polaron absorption region) compared to Frenkel excitons. As a result, our devices achieve a high EQE of ∼107%, femtowatt sensitivity (NEP) of ~0.12 fW Hz-1/2 along a response time of ~81 ms, at room temperature for a wavelength of 1.0 µm. Our innovative utilization of polarons highlights their potential as alternatives to Frenkel excitons in high-performance organic IR PDs.

Effects of Partially Filled EPS Foam on Compressive Behavior of Aluminum Hexagonal Honeycombs.

This study investigates the compressive behavior of aluminum honeycombs partially filled with expanded polystyrene (EPS) foam, emphasizing the effects of filler area fractions and vertex contact locations on energy absorption and crush characteristics. Axial quasi-static compression tests evaluated energy absorption, mean crush force, specific energy absorption, and crush force efficiency. Results revealed that partially filled honeycombs significantly enhance energy absorption and mean crush force compared to their unfilled counterparts. However, higher filler area fractions increased mass, reducing specific energy absorption. Circular fillers exhibited lower energy absorption than hexagonal fillers due to their larger contact radius, which reduces stress concentration. The interaction between cell walls and fillers influenced densification strain, with wall-midpoint vertex contacts increasing peak force by reinforcing walls, while corner contacts reduced peak force but improved crush force efficiency. These findings underscore the potential of optimized, partially filled honeycombs for lightweight, energy-absorbing applications, particularly in automotive engineering.

The attenuation characteristics and optimization design of polyurethane foam bulkhead to blast wave

Abstract Polyurethane foam has the characteristics of low density, nonlinear mechanics and energy absorption, and has been widely used in the research of shock wave attenuation. In order to realize the effective attenuation of the blast wave, the attenuation process of the shock wave in the medium is simulated by Autodyn. The impact ignition simulations were carried out for the Comp B impact ignite TNT under the bulkheads. The results show that the explosion-proof performance of the composite bulkhead is signi2icantly better than that of the single medium bulkhead. The combination of PR 6720 (polyurethane foam) and 45#steel can greatly attenuate the blast wave. The impact impedance matching relationship of the bulkhead and the medium on both sides should be used as an important design factor when designing the bulkhead.

INVESTIGATION OF IMPACT PERFORMANCE OF CYLINDER CORRUGATED SANDWICH STRUCTURES WITH DIFFERENT GEOMETRIC CONFIGURATIONS

The aim of this study is to numerically investigate and compare the impact performance of CFRP composite cylinder sandwich structures with five different geometric configurations. The impact performances and damage types of composite cylinder structures for different core configurations were determined. The impact analyses were performed in LS DYNA finite element program using MAT-54 material model with Progressive damage analysis based on the combination of Hashin damage criterion, Cohesive zone model and Bilinear traction-separation law. Among the five different specimens in the study, the highest peak force (PF) value of 1.88 kN was obtained at impact point P2 of the Trapeozidal sandwich structure. The lowest value was obtained at P1 impact point in Triangular sandwich structure with 0.62 kN. The highest and lowest energy absorption efficiency occurred in the Triangular structure, 78% and 38% respectively. The PF value at P2 point is higher than P1. The effect of core support on PF is very important. Since point P1 is not supported by the core, it is determined that the deformation is larger than P2.

Development of phosphine and diimine stabilized copper(I) catalysts for efficient azide–alkyne cycloaddition

The synthesis of a small family of copper(I) complexes bound to diimine and phosphine ligands, and their characterization, spectroscopic properties and application as pre-catalyst for azide–alkyne cycloaddition reaction are reported. Reaction of bis-(N-aryl)glyoxaldimine (p-R-C6H4NC(H)(H)CNC6H4-R-p; R = OCH3, CH3 and Cl; abbreviated as L-R) with [Cu(PPh3)2(NO3)] in refluxing methanol affords a group of three mixed-ligand copper(I) complexes of type [Cu(PPh3)2(L-R)]NO3, depicted respectively as complex 1 (R = OCH3), 2 (R = CH3) and 3 (R = Cl). Crystal structures of 1–3 have been determined by X-ray diffraction analysis. In each complex, the copper(I) center is nested in a nearly tetrahedral N2P2 coordination environment. Complexes 1–3 exhibit two intense absorptions spanning over the visible and ultraviolet regions. Origin of these absorptions was probed with DFT and TDDFT calculations, which revealed that the lower energy absorption at 346–380 nm is due to an allowed copper-to-diimine charge-transfer transition, and the second absorption near 270 nm is largely due to an intra-phosphine charge-transfer transition. These complexes also show prominent emission spectra while excited at 320 nm. These copper(I) complexes are found to serve as efficient precursor for catalytic azide–alkyne cycloaddition reaction under relatively mild condition, and offering a broad substrate scope.

Elucidation of Electronic Structures of Mixed-Valence States Induced by dσ-π Charge Delocalization in Linear-Chain and Discrete Rhodium-Dioxolene Tetrameric Complexes.

We have successfully synthesized unique linear-chain and discrete mixed-valence tetrameric complexes, {[Rh(3,6-DBDiox-4,5-S2CO)(CO)2]4·hexane}∞ (4) and [Rh(3,6-DBDiox-4,5-S2CO)(CO)2]4 (5), by carefully choosing the solvent. X-ray photoelectron spectra (XPS) confirm that 4 and 5 are in the Rh(I,II) mixed-valence state. Analyses of the metrical oxidation state (MOS) of dioxolene ligands reveal that in 4 and 5, the electron density corresponding to one electron per tetramer is transferred from Rh(I) ions to semiquinonato ligands, and the transferred charge is delocalized throughout the four dioxolene ligands. Due to their mixed-valence state, 4 and 5 are semiconductors with relatively high electrical conductivity at room temperature. Density functional theory (DFT) calculations of tetrameric complex demonstrated for the first time that the dσ* orbitals of the Rh atoms and the π* orbitals of the semiquinonato ligands, which are originally highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), respectively, strongly hybridize with each other, leading to the Rh(I,II)-semiquinonato/catecholato mixed-valence state. Furthermore, time-dependent (TD)-DFT calculations have also revealed that the low energy absorption band observed centered at 5700 cm-1 is attributed to a charge transfer from [dσ*(Rh)] (HOMO) or [π*(SQ)-dσ*(Rh)] (HOMO-1) to [π*(SQ)-dσ*(Rh)] (LUMO/LUMO+1). Although 4 and 5 are tetramers with nearly identical structures, their magnetic interactions are found to differ significantly depending on their crystal structures.

Asymmetric fluorinated 2,3-bis(5-arylthiophen-2-yl)quinoxalines: Synthesis and photophysical properties

A series of novel 6-fluoro- and 6-trifluoromethyl-2,3-bis(5-arylthiophen-2-yl)quinoxalines was synthesized via Pd-catalyzed cross-coupling reactions. Their photophysical properties were studied in solutions of fluorophores in toluene, THF, and MeCN, as well as in the solid state. These V-shaped quinoxalines exhibited a low-energy absorption band ranging from 394 to 457 nm and emitted light in the broad region from green to orange in toluene. Notably, the absorption and emission bands of 6-CF3-substituted quinoxalines shifted towards the red region compared to their 6-fluoro analogues. While solvent polarity had negligible effects on the absorption band, it significantly influenced the emission band, causing a pronounced red-shift and attenuating its intensity. The obtained properties were compared with those of related structures, and structure-photophysical property relationships were examined. Furthermore, the effect of external stimuli, including acidity, the presence of water, and nitroaromatic compounds, on the absorption and emission behaviors was evaluated. Finally, electronic-structure calculations based on quantum-chemical methods were conducted to provide insights into the experimental findings.

Quasi-static indentation characteristics of foam-filled sandwich composite structures with additively manufactured CFRP and GFRP corrugated cores

This paper presents an experimental investigation on the quasi-static indentation performance of polyurethane (PU) foam-filled carbon fibre-reinforced polymer (CFRP) and glass fibre-reinforced polymer (GFRP) corrugated sandwich composite structures (SCSs) under different indenter tip geometries (conical, trapezoidal, hemispherical, pyramidal, and cylindrical shapes). The SCSs were produced using hybrid manufacturing methods: (1) the facesheets were fabricated using the vacuum-assisted resin infusion (VARI) process, (2) the CFRP and GFRP corrugated cores were additively manufactured using the fused filament fabrication (FFF) process, and (3) the self-expanding PU foam-filled the open spaces in the core. The results elucidated that the indenter tip geometry and core material have a large influence on the indentation performance of SCSs. The cylindrical indenter showed the highest peak load, bending stiffness, and damage severity, while the conical indenter offered the lowest peak load, energy absorption, and damage severity. Among different core materials, CFRP corrugated core SCSs exhibited higher peak loads, specific energy absorption, and damage severity compared to ones with GFRP core. The primary damage modes were observed using an optical microscope, showing facesheet rupture, debonding between facesheets and core, core crushing, foam densification, and shear plugging. Shear plugging is a unique failure mode observed with cylindrical indenter tip geometry due to the blunt edges of the indenter, which induced large damages in SCSs. These findings provide new insight into the design and development of lightweight additively manufactured SCSs, which will benefit a wide range of industries and applications.

Eco-friendly synthesis of Nd³⁺-doped Eu₂O₃ nanoparticles for enhanced dye-sensitized solar cells utilizing oxalis Corniculata leaf extract

An environmentally friendly synthesis of Nd³⁺-doped Eu₂O₃ nanoparticles (NPs) was developed using Oxalis Corniculata leaf (OCL) extract to enhance the performance of dye-sensitized solar cells (DSSCs). The as-synthesized NPs were annealed at 600 °C to improve their crystallinity. X-ray diffraction and field-emission scanning electron microscopy revealed high crystallinity and a sub-100 nm spherical morphology. Annealing reduced the NP size from ∼85 nm to ∼45 nm and decreased the bandgap from 4.97 eV to 4.62 eV, enhancing low-energy photon absorption. Fourier-transform infrared spectroscopy showed changes in the chemical bonding environment, with a higher presence of dangling bonds in the as-prepared NPs compared to the 600 °C-annealed NPs, likely due to the OCL extract. Photoluminescence spectra confirmed strong red emission peaks at 580 nm and 612 nm, with a slight reduction in the full width at half maximum of the electric dipole transition after annealing. Integrating these NPs into TiO₂ matrices in DSSCs improved power conversion efficiency to 8.58%, outperforming both as-prepared NPs (6.88%) and bare TiO₂ cells (5.05%). This green synthesis approach offers a sustainable pathway for slightly enhancing performance of photovoltaic devices, with additional potential for UV-shielding applications when incorporated into PVA films.

Evidence of Different Charging Behavior of Conductive and Dielectric Materials in Low-Temperature Plasmas and a New Diagnostic for Low-Energy Electron Absorption.

In any physical system where a surface is hit by electrons, the sticking probability s of the electrons is a central parameter governing, for example, the charging of the surface. For dielectrics, it could previously only be measured for high energies (>100 eV), while it is well-known for metals even at energies of only a few eV. Recent theoretical investigations concerning dielectrics such as silica predict values for s significantly below 1. With precision charge measurements on microparticles in the sheath of a low-pressure plasma, a difference in charge between silica and gold-coated particles is found, challenging the long-standing assumption in dusty plasma physics that dielectric and metallic particles charge in the same way for the first time. Based on the measured charging difference, the low-energy sticking coefficient of silica is obtained, validating the theoretical predictions and offering a new diagnostic for the otherwise quasi-inaccessible low-energy electron sticking of dielectric materials.

Hypoxia-Active Iridium(III) Bis-terpyridine Complexes Bearing Oligothienyl Substituents: Synthesis, Photophysics, and Phototoxicity toward Cancer Cells.

In an effort to develop hypoxia-active iridium(III) complexes with long visible-light absorption, we synthesized and characterized five bis(terpyridine) Ir(III) complexes bearing oligothienyl substituents on one of the terpyridine ligands, i.e., nT-Ir (n = 0-4). The UV-vis absorption, emission, and transient absorption spectroscopy were employed to characterize the singlet and triplet excited states of these complexes and to explore the effects of varied number of thienyl units on the photophysical parameters of the complexes. In vitro photodynamic therapeutic activities of these complexes were assessed with respect to three melanoma cell lines (SKMEL28, A375, and B16F10) and two breast cancer cell lines (MDA-MB-231 and MCF-7) under normoxia (∼18.5% oxygen tension) and hypoxia (1% oxygen tension) upon broadband visible (400-700 nm), blue (453 nm), green (523 nm), and red (633 nm) light activation. It was revealed that the increased number of thienyl units bathochromically shifted the low-energy absorption bands to the green/orange spectral regions and the emission bands to the near-infrared (NIR) regions. The lowest triplet excited-state lifetimes and the singlet oxygen generation efficiency also increased from 0T to 2T substitution but decreased in 3T and 4T substitution. All complexes exhibited low dark cytotoxicity toward all cell lines, but 2T-Ir-4T-Ir manifested high photocytotoxicity for all cell lines upon visible, blue, and green light activation under normoxia, with 2T-Ir showing the strongest photocytotoxicity toward SKMEL28, MDA-MB-231, and MCF-7 cells, and 4T-Ir being the most photocytotoxic one for B16F10 and A375 cells. Singlet oxygen, superoxide anion radicals, and peroxynitrite anions were found to likely be involved in the photocytotoxicity exhibited by the complexes. 4T-Ir also showed strong photocytotoxicity upon red-light excitation toward all cell lines under normoxia and retained its photocytotoxicity under hypoxia toward all cell lines upon visible, blue, and green light excitation. The hypoxic activity of 4T-Ir along with its green to orange light absorption, NIR emission, and low dark cytotoxicity suggest its potential as a photosensitizer for photodynamic therapy applications.

Thermal life assessment of laser powder-directed energy deposited NiCrAlY/CuCrZr bimetallic clad for rocket nozzle applications

To enhance the thermal life of rocket exhaust nozzles, the hot side of copper liners is coated with thermal barrier coatings (TBCs) to provide thermal insulation and oxidation resistance. However, interface failures often occur between M-CrAlY bond coats and nozzle liners due to significant differences in their thermal expansion coefficients (CTE). This study explores the use of Laser Powder-Directed Energy Deposition (LP-DED) to clad NiCrAlY onto a CuCrZr substrate, as the process offers localized heating which can offer better bond strength. Optimization trials were conducted using single and multi-track studies to identify optimal parameters. Due to the low energy absorption of the CuCrZr substrate to 1070 nm laser sources, cladding was performed at a high energy density of 135 J/mm2 with a 1.2 g/min feed rate to achieve defect-free clads with sufficient diffusion. The bulk of the NiCrAlY clads showed γ′-Ni3Al, β-NiAl, and γ-Ni phases, while Y4Al2O9 and Y2O3 oxides formed on the top surface due to aluminum and yttrium depletion at high temperatures. The clads exhibited cellular dendritic microstructures at the bulk region, and planar microstructures were observed at the dilution zone. EBSD-KAM maps showed higher dislocation density near the interface due to CTE mismatch across substrate and clad. Scratch tests confirmed strong adhesion with no interface cracks, though crack propagation was observed from the edges after 50 isothermal cycles, driven by copper erosion. With Cu diffusion, interface region exhibited a graded microstructure which could enhance CTE, improving compatibility compared to standard NiCrAlY alloys.

Energy absorption properties of origami‐based re‐entrant honeycomb sandwich structures with CFRP subjected to low‐velocity impact

AbstractThis paper investigates a honeycomb sandwich structure that draws inspiration from the craft of origami. A specific folding pattern was applied to the honeycomb to create the origami‐based re‐entrant honeycomb (ORH), aimed at improving the energy absorption properties of the sandwich structure. The study on the energy absorption properties of structures under low‐velocity impact (LVI) utilized both experimental and numerical approaches. The energy absorption properties of the sandwich structure were examined by conducting LVI tests with different impact energy and then compared to the mechanical properties of the traditional re‐entrant honeycomb sandwich structures (TRHSS). Additionally, a refined finite element model has been established and its accuracy verified. Numerical studies were conducted to explore the effects of structural parameters on the energy absorption properties of ORH sandwich structure (ORHSS). The results show that the ORHSS exhibited a significant reduction in peak force when subjected to LVI, in contrast to the TRHSS. Furthermore, the ORHSS exhibit significant efficiency in energy absorption. Enhancing the wall thickness or folding angle can significantly improve the energy absorption properties of the ORHSS, thereby boosting the honeycomb's contribution to this process. This optimization results in an improved absorptive effect of the structure. The findings offer new recommendations for developing lightweight absorbent materials with potential applications across various industries.Highlights A novel composite sandwich structure serves as an efficient device for absorbing energy. This sandwich structure exhibits excellent cushioning and energy absorption capabilities. Changing geometric parameters can enhance the impact performance of the structure. A larger folding angle makes the core more prone to deformation. The greater the forward length of the ORH, the lower specific energy absorption (SEA) of the ORHSS.

Laser Powder Bed Fusion of Multifunctional Bio-inspired Vertical Honeycomb Sandwich Structures: For the Application of Lightweight Bipolar Plates of Proton Exchange Membrane Fuel Cells

The bipolar plate (BPP) is a crucial component of proton exchange membrane fuel cells (PEMFC). However, the weight of BPPs can account for around 80% of a PEMFC stack, posing a hindrance to the commercialization of PEMFCs. Therefore, the lightweight design of BPPs should be considered as a priority. Honeycomb sandwich structures meet some requirements for bipolar plates, such as high mechanical strength and lightweight. Animals and plants in nature provide many excellent structures with characteristics such as low density and high energy absorption capacity. In this work, inspired by the microstructures of the Cybister elytra, a novel bio-inspired vertical honeycomb sandwich (BVHS) structure was designed and manufactured by laser powder bed fusion (LPBF) for the application of lightweight BPPs. Compared with the conventional vertical honeycomb sandwich (CVHS) structure formed by LPBF under the same process parameters setting, the introduction of fractal thin walls enabled self-supporting and thus improved LPBF formability. In addition, the BVHS structure exhibited superior energy absorption (EA) capability and bending properties. It is worth noting that, compared with the CVHS structure, the specific energy absorption (SEA) and specific bending strength of the BVHS structure increased by 56.99% and 46.91%, respectively. Finite element analysis (FEA) was employed to study stress distributions in structures during bending and analyze the influence mechanism of the fractal feature on the mechanical properties of BVHS structures. The electrical conductivity of structures were also studied in this work, the BVHS structures were slightly lower than the CVHS structure. FEA was also conducted to analyze the current flow direction and current density distribution of BVHS structures under a constant voltage, illustrating the influence mechanism of fractal angles on electrical conductivity properties. Finally, in order to solve the problem of trapped powder inside the enclosed unit cells, a droplet-shaped powder outlet was designed for LPBF-processed components. The number of powder outlets was optimized based on bending properties. Results of this work could provide guidelines for the design of lightweight BPPs with high mechanical strength and high electrical conductivity.

Synthesis and Optical Characterization of Hydrazone-Substituted Push-Pull-Type NLOphores.

Two distinct families of NLOphores featuring hydrazone donors were synthesized using click-type [2 + 2] cycloaddition retroelectrocyclizations (CA-RE). Despite the limitations in the substrate scope, it was shown for the first time that hydrazone-activated alkynes could undergo reactions with TCNE/TCNQ. The electrochemical, photophysical, and second-order nonlinear optical (NLO) characteristics of the chromophores were analyzed utilizing experimental and computational approaches. Chromophores 17-21 and 23-27 exhibited two reduction waves, along with one oxidation wave that can be attributed to the hydrazone moiety. All chromophores exhibit charge-transfer bands extending from the visible to the near-infrared region. The λmax of hydrazone-based chromophores falls within the range of 473 to 725 nm. Additionally, all chromophores exhibited positive solvatochromism. Computational studies have been performed to elucidate the origin of the low-energy absorption bands. Parameters such as dipole moment, band gaps, electronegativity, global chemical hardness/softness, average polarizability, and first hyperpolarizability were calculated to obtain information about NLO properties of the target structures. The thermal stabilities of the NLOphores were assessed through TGA. Experimental NLO measurements were conducted using the electric field-induced second harmonic generation (EFISHG) technique. The studied structures demonstrated NLO responses, with μβ values between 520 × 10-48 esu and 5300 × 10-48 esu.