Crystal Length Research Articles

Near-Infrared All-Fused-Ring Nonfullerene Acceptors Achieving an Optimal Efficiency-Cost-Stability Balance in Organic Solar Cells

Near-Infrared All-Fused-Ring Nonfullerene Acceptors Achieving an Optimal Efficiency-Cost-Stability Balance in Organic Solar Cells

The effect of melt drawing ratio on the crystal structural change and performance of polyketone extrusion cast film

In this paper, the polyketone (POK) extrusion cast film is manufactured by melt stretching method, and the evolution process of the crystal morphology and mechanical properties with the increase of melt drawing ratio (MDR) are followed. The results show that the melt stretching process produces many micro shish-kebab crystals in the POK. The length of the shish crystal and the thickness of the kebab crystal hardly increase with MDR, but the lateral length of the kebab crystal shows linear growth when MDR exceeds 40. The crystalline morphology of POK is mainly affected by melt relaxation. The molecular chain has sufficient relaxation during cooling at a low MDR (20–40). At this time, micro shish-kebab crystals are mainly randomly arranged. When MDR exceeds 40, the rapid melt stretching shortens the relaxation time of the tie chain between the neighborhood shish crystal, and the atomic force microscopy image shows a typical shish-kebab structure. This experimental result indicates that the formation of the oriented lamella structure may be related to the relaxation of the molecular chains between the micro-shish. When the length of the shish axis and the thickness of the kebab lamellae are similar, it is difficult to distinguish the two.

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 , 7.6nm) 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.

Analysis on the thermal effect of Pr:YLF crystal for power scaling

In a high-power Pr:YLF solid-state laser, the thermal effect of gain medium is one of the prime limiting factors, and its thermal damage has become the major concern. The thermal effect of Pr:YLF crystal was analyzed theoretically, and the distribution of temperature, thermal stress, thermal focal length, and pump polarization effects of the Pr:YLF crystal were simulated. The thermal effect investigation indicates that under reasonable pumping power density, crystal length, and beam waist size and location, the temperature rise and nonuniformity of thermal distortion are not intensified under high-power operation. Additionally, the relationship between Gauss or Super-Gaussian pump mode and thermal focal length of Pr:YLF crystal was simulated. To the best of our knowledge, this analysis is the first to examine the thermal effect of Pr:YLF crystal for power scaling, and this thermal effect investigation of Pr:YLF crystal provides first-hand data for a high-power, visible, solid-state laser that could be helpful for high-power Pr:YLF solid-state laser design.

Crystal Structures of Iron‐Based Oxides and Their Catalytic Efficiencies for the Oxygen Evolution Reaction: A Trend in Alkaline Media

AbstractInvited for this month's cover picture are the groups of Prof. Takeo Yamaguchi and Prof. Keigo Kamata at Tokyo Institute of Technology. The cover picture illustrates the data‐driven investigation of the trend in the crystal structures of iron‐based oxides and their electrocatalysis on the oxygen evolution reaction (OER). The investigation using 24 kinds of iron‐based oxides concluded that the OER efficiency on iron‐based oxides was uniquely determined by the Fe–O bond length in the bulk crystals of the materials. Read the full text of the Research Article at 10.1002/celc.202101679.

Micromechanically-Powered Rolling Locomotion of a Twisted-Crystal Optical-Waveguide Cavity as a Mobile Light Polarization Rotor.

We demonstrate mechanically-powered rolling locomotion of a twisted-microcrystal optical-waveguide cavity on the substrate, rotating the output signal's linear-polarization. Self-assembly of (E)-2-bromo-6-(((4-methoxyphenyl)imino)methyl)-4-nitrophenol produces naturally twisted microcrystals. The strain between several intergrowing, orientationally mismatched nanocrystalline fibres dictates the pitch lengths of the twisted crystals. The crystals are flexible, perpendicular to twisted (001) and (010) planes due to π⋅⋅⋅π stacking, C-H⋅⋅⋅Br, N-H⋅⋅⋅O and C-H⋅⋅⋅O interactions. The twisted crystals in their straight and bent geometries guide fluorescence along their body axes and display optical modes. Depending upon the degree of mechanical rolling locomotion, the crystal-waveguide cavity correspondingly rotates the output signal polarization. The presented twisted-crystal cavity with a combination of mechanical locomotion and photonic attributes unfolds a new dimension in mechanophotonics.

Micromechanically‐Powered Rolling Locomotion of a Twisted‐Crystal Optical‐Waveguide Cavity as a Mobile Light Polarization Rotor

AbstractWe demonstrate mechanically‐powered rolling locomotion of a twisted‐microcrystal optical‐waveguide cavity on the substrate, rotating the output signal's linear‐polarization. Self‐assembly of (E)‐2‐bromo‐6‐(((4‐methoxyphenyl)imino)methyl)‐4‐nitrophenol produces naturally twisted microcrystals. The strain between several intergrowing, orientationally mismatched nanocrystalline fibres dictates the pitch lengths of the twisted crystals. The crystals are flexible, perpendicular to twisted (001) and (010) planes due to π⋅⋅⋅π stacking, C−H⋅⋅⋅Br, N−H⋅⋅⋅O and C−H⋅⋅⋅O interactions. The twisted crystals in their straight and bent geometries guide fluorescence along their body axes and display optical modes. Depending upon the degree of mechanical rolling locomotion, the crystal‐waveguide cavity correspondingly rotates the output signal polarization. The presented twisted‐crystal cavity with a combination of mechanical locomotion and photonic attributes unfolds a new dimension in mechanophotonics.

Engineering Photomechanical Molecular Crystals to Achieve Extraordinary Expansion Based on Solid-State [2 + 2] Photocycloaddition.

Photomechanical molecular crystals are promising candidates for photoactuators and can potentially be implemented as smart materials in various fields. Here, we synthesized a new molecular crystal, (E)-3-(naphthalen-1-yl)acrylaldehyde malononitrile ((E)-NAAM), that can undergo a solid-state [2 + 2] photocycloaddition reaction under visible light (≥400 nm) illumination. (E)-NAAM microcrystals containing symmetric twinned sealed cavities were prepared using a surfactant-mediated crystal seeded growth method. When exposed to light, the hollow microcrystals exhibited robust photomechanical motions, including bending and dramatic directional expansion of up to 43.1% elongation of the original crystal length before fragmentation due to the photosalient effect. The sealed cavities inside the microcrystals could store different aqueous dye solutions for approximately one month and release the solutions instantly upon light irradiation. A unique slow-fast-slow crystal elongation kinematic process was observed, suggesting significant molecular rearrangements during the illumination period, leading to an average anisotropic crystal elongation of 37.0% (±3.8%). The significant molecular structure and geometry changes accompanying the photocycloaddition reaction, which propels photochemistry to nearly 100% completion, also facilitate photomechanical crystal expansion. Our results provide a possible way to rationally design molecular structures and engineer crystal morphologies to promote more interesting photomechanical behaviors.

Novel Pyrrolo [3,4-b] Dithieno [3, 2-f:2″,3″-h] Quinoxaline-8,10 (9H)-Dione Based Wide Bandgap Conjugated Copolymers for Bulk Heterojunction Polymer Solar Cells.

Two D-A copolymers consisting of fused ring pyrrolo-dithieno-quinoxaline acceptors are synthesized with different donor units, i.e., benzodithiophene (BDT) with alkylthienyl (P134) and 2-ethylhexyloxy (P117) side chains. These copolymers are used as donors and a narrow bandgap acceptor Y6 to fabricate bulk heterojunction polymer solar cell devices. Owing to the strong electron-deficient fused ring pyrrolo-bithieno-quinoxaline and weak alkyl thienyl side chains in BDT, the polymer solar cells (PSCs) based on P134:Y6 attain the power conversion efficiency (PCE) of 15.42%, which is higher than the P117:Y6 counterpart (12.14%). The superior value of PCE for P134:Y6 can be associated with more well-adjusted charge transport, weak charge recombination, proficient exciton generation, and dissociation into free charge carriers and their subsequent charge collection owing to the dense π-π stacking distance and more considerable crystal coherence length for the P134:Y6 thin films. This investigation confirms the great potential of a strong acceptor-weak donor tactic for developing efficient D-A copolymers consists of quinoxaline acceptor for PSCs.

Compact 589 nm yellow source generated by frequency‐doubling of passively Q‐switched Nd:YVO4 Raman laser

AbstractCompact 589 nm yellow source was reported and generated from intracavity frequency‐doubling of c‐cut YVO4/Nd:YVO4/YVO4 Raman laser. A Cr4+:YAG/YAG composite was adopted for compact passively Q‐switching operation. Double‐end composited Nd:YVO4 crystal was designed to reduce the thermal effect and increase Raman crystal length. Both noncritical phase‐matching (NCPM) LBO crystal and critical phase‐matching (CPM) BBO crystal were used as frequency doubling crystal for comparison. 780 mW output power of 589 nm yellow emission was achieved with an incident pump power of 16 W. The pulse repetition frequency and pulse width were 41 kHz and 3.6 ns at the maximum output power, respectively. The results show passively Q‐switched operation provides a compact method to obtain 589 nm yellow emission.

Long carrier diffusion length in two-dimensional lead halide perovskite single crystals

<h2>Summary</h2> Ruddlesden-Popper (RP) perovskites are two-dimensional semiconductors for high-performance optoelectronic devices. In this work, we report a long in-plane carrier diffusion length in 2D RP perovskite single crystals probed by scanning photocurrent microscopy. Carrier diffusion lengths of 7–14 μm are observed when the number of PbI₆⁻² octahedra between organic spacers increases from 1 to 3. Using detailed light intensity and electric-field-dependent photocurrent measurements, we attribute the observed long diffusion length to the dominating dissociated free carrier transport. This is further validated by time-resolved photoluminescence measurements, where the decay lifetime increases in the presence of an electric field. From our experiments, we conclude that the in-plane transport in RP perovskites is efficient because of the partial free carrier generation, which overcomes strong excitonic effects. Our results suggest that semiconducting devices fabricated from RP perovskite single crystals can be as efficient as their 3D counterparts.

An Electrical Method for Acoustic Resonance Frequency Adjustment in Standing-Wave Acousto-Optic Devices.

An acousto-optic (AO) device can be configured to operate in a standing wave (SW) mode. The effectiveness of an SW AO device surpasses the effectiveness of a conventional, running-wave one, when the driving signal frequency meets the SW condition. This SW frequency depends primarily on the acoustic wave velocity and the crystal length. While promising significant benefits, this situation imposes serious restrictions on the AO device performance. In this study, we examine the SW frequency dependency of such a device on its electrical impedance matching circuit (EIMC) parameters and configuration both theoretically and experimentally. Our analysis is aimed at this effect utilization for the purpose of expanding of the standing-wave AO devices applicability domain.

Structure, optical, thermal, SHG & photoluminescence studies of L-Serine cadmium chloride single crystals

Novel semi organic nonlinear optical single crystal of l-Serine Cadmium Chloride monohydrate has been synthesized by conventional slow evaporation method. The single crystal XRD have been employed to describe the crystal structure, space group, bond lengths, bond angles and co ordinates of hydrogen bond. The metal organic complexion between l-Serine and Cadmium chloride is taking place through oxygen atom of l-Serine. The lattice parameters obtained from PXRD technique have been found in good agreement with those obtained from SXRD. Williamson-Hall method has been used to determine the lattice strain of the grown crystal. The investigations of intermolecular interactions in LSCC crystal lattice are carried out by Hirshfeld surface analysis. The FTIR spectrum is utilized to determine the possible functional groups present in the crystal. The investigations on optical qualities of the crystal are carried out by incorporating UV–Visible and photoluminescence spectrum. The behaviour of refractive index below energy gap is carried out by Wemple – DiDomenico single oscillator model analysis. The thermal stability along with the decomposition temperature of the synthesized crystal is ascertained by thermogravimetric analysis. The kinetic and thermodynamic parameters of LSCC crystal have been calculated from C-R plot. Photoluminescence spectrum of the synthesized crystal was recorded by using an excitation wavelength of 320 nm. It suggested the suitability of the synthesized material as green laser diode. The SHG efficiency of LSCC crystal is clarified through the Kurtz-Perry technique.

Tunable Ultraviolet Second Harmonics Generation Pumped by Supercontinuum Laser

This paper presents the first systematic study on second harmonics generation based on a supercontinuum source. We analyzed the effect of the supercontinuum beam diameter and the crystal length to generate second harmonics. The walk-off effect on the second harmonics was also investigated; the efficiency was limited by the walk-off, and the beam of the second harmonic was out of shape. A tunable ultraviolet in the range of 285340 nm is obtained with the pump of a visible supercontinuum, which is generated by a laser with an all-fiber device. The results provide a theoretical basis for the improvement of the second harmonic power and optimization of the crystal and beam diameters. A potentially tunable ultraviolet with a power exceeding 10 mW can be obtained by a high-power supercontinuum pump.

Effects of alkali treatment on properties of willow bark fiber as potential fillers for polymer composites

In this work, willow fiber was extracted from willow inner bark and modified with alkali solution of various concentrations, temperature and time. The morphology, surface functional group, crystal and thermal stability were investigated by using a scanning electron microscopy, a Fourier transform infrared spectroscopy, an X-ray powder diffractometer, and a simultaneous thermal analyzer, respectively. The acid (H2SO4, 2 ml/l) extraction procedure removed the hemicellulose and part of lignin from willow bark, cleared the aggregation of WB, kept the crystal structure of willow fiber, dramatically increased the crystal length of fiber (from 18.46 to 30.15 nm), and enhanced the onset degradation temperature (from 262.23℃ to 297.62℃) and chemical reactivity (DTG: from 0.57%/s to 0.84%/s). The alkali treatment further removed lignin from willow fiber, smoothed the fiber surface, increased the intensity of cellulose [Formula: see text] from 646 counts to 1292 counts, and lengthened the crystal length from 30.15 to 41.84 nm. Varying the alkali treating condition, the crystal index and thermal stability reached to the climax at 60℃ of treating temperature and 7 h treating time. The treated willow fiber may have potential applications to composite with polymer, and to be used in pharmaceutical field as additives.

Scrutinizing particle size related bond strengthening in anatase TiO2.

A series of small, middle, and large anatase TiO2 particles were synthesized through the hydrolysis of titanium tetraisopropoxide (TTIP) to investigate the size-related chemical bond length and strength variation. Unit cell volume contraction with decreasing particle size is identified from Rietveld refinement of high-resolution synchrotron powder X-ray diffraction (PXRD) patterns. More titanium vacancies are also found for smaller anatase particles. Contrary to the variation in unit cell volume, a larger Debye temperature ΘD(TiO2) derived from the linear and nonlinear fitting of atomic displacement parameters (Uiso(TiO2)) as a function of temperature is revealed for smaller anatase particles. The length of the Ti-O bond is also shorter for smaller anatase particles. Furthermore, optical phonon frequencies blue-shifting with the decrease in anatase particle size are determined by Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) analysis rules out the presence of a large amount of Ti3+, while optical diffuse reflectance measurement eliminates the existence of a large number of oxygen vacancies in all particles. Combining the analysis results of PXRD, thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR), more structural and surface hydroxyls (-OH) appear to exist in smaller anatase particles. It is the structural and surface -OH that are responsible for the size-related chemical bond length and strength variation in the as-synthesized anatase particles.

Theoretical analyses and configuration optimizations of a LD-pumped 3.9 µm Ho:BYF laser

In this paper, we introduced the theoretical simulation results of output performances for a LD-pumped 3.9 µm Ho:BYF laser by considering two unique kinetic processes named as energy transfer up-conversion (ETU) and cross relaxation (CR). The influence of the pump energy, pump beam waist radius, pump pulse width, and crystal length on the output characteristics was discussed in detail for the Ho:BYF laser. The thermal simulation was also carried out for the Ho:BYF crystal by using a finite element method (FEM). Then, we constructed a LD-pumped experimental system and successfully realized a LD-pumped 3.9 µm laser. Next, some efforts were undertaken for optimizing the curvature radius of an output coupler (OC), focus position inside Ho:BYF bulks, and crystal length, respectively. The maximum energy of 1.87 mJ had been finally obtained after the optimization. By considering the LD-pumped solid-state laser is still rare in the mid-infrared, our study is thought to be useful for the development of a novel compact and efficient laser in the future.

Non-Obese MKR Mouse Model of Type 2 Diabetes Reveals Skeletal Alterations in Mineralization and Material Properties.

ABSTRACTObesity is a common comorbidity of type 2 diabetes (T2D). Therefore, increased risk of fragility fractures in T2D is often confounded by the effects of obesity. This study was conducted to elucidate the mechanistic basis by which T2D alone leads to skeletal fragility. We hypothesized that obesity independent T2D would deteriorate bone's material quality by accumulating defects in the mineral matrix and undesired modifications in its organic matrix associated with increased oxidative stress and hyperglycemia. To test this hypothesis, we used 15‐week‐old male non‐obese mice with engineered muscle creatine kinase promoter/human dominant negative insulin growth factor 1 (IGF‐I) receptor (MKR) and FVB/N wild‐type (WT) controls (n = 12/group). MKR mice exhibit reduced insulin production and loss of glycemic control leading to diabetic hyperglycemia, verified by fasting blood glucose measurements (>250 mg/dL), without an increase in body weight. MKR mice showed a significant decrease in femoral radial geometry (cortical area, moment of inertia, cortical thickness, endosteal diameter, and periosteal diameter). Bone mineral density (BMD), as assessed by micro–computed tomography (μCT), remained unchanged; however, the quality of bone mineral was altered. In contrast to controls, MKR mice had significantly increased hydroxyapatite crystal thickness, measured by small‐angle X‐ray scattering, and elongated c‐axis length of the crystals evaluated by confocal Raman spectroscopy. There was an increase in changes in the organic matrix of MKR mice, associated with enhanced glycoxidation (carboxymethyl‐lysine [CML] and pentosidine) and overall glycation (fluorescent advanced glycation end products), both of which were associated with various measures of bone fragility. Moreover, increased CML formation positively correlated with elongated mineral crystal length, supporting the role of this negatively charged side chain to attract calcium ions, promote growth of hydroxyapatite, and build a physical link between mineral and collagen. Collectively, our results show, for the first time, changes in bone matrix in a non‐obese T2D model in which skeletal fragility is attributable to alterations in the mineral quality and undesired organic matrix modifications. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Reactive Crystallization Kinetics of K2SO4 from Picromerite-Based MgSO4 and KCl

In this work, the kinetic parameters, the degrees of initial supersaturation (S0) and the profiles of supersaturation (S) were determined for the reactive crystallization of K2SO4 from picromerite (K2SO4.MgSO4.6H2O) and KCl. Different reaction temperatures between 5 and 45 °C were considered, and several process analytical techniques were applied. Along with the solution temperature, the crystal chord length distribution (CLD) was continuously followed by an FBRM probe, images of nucleation and growth events as well as the crystal morphology were captured, and the absorbance of the solution was measured via ATR-FTIR spectroscopy. In addition, the ion concentrations were analyzed. It was found that S0 is inversely proportional to the reactive crystallization temperature in the K+, Mg2+/Cl−, SO42−//H2O system at 25 °C, where S0 promotes nucleation and crystal growth of K2SO4 leading to a bimodal CLD. The CLD was converted to square-weighted chord lengths for each S0 to determine the secondary nucleation rate (B), crystal growth rate (G), and suspension density (MT). By correlation, from primary nucleation rate (Bb) and G with S0, the empirical parameters b = 3.61 and g = 4.61 were obtained as the order of primary nucleation and growth, respectively. B versus G and MT were correlated to the reaction temperature providing the rate constants of B and respective activation energy, E = 69.83 kJ∙mol−1. Finally, a general Equation was derived that describes B with parameters KR = 13,810.8, i = 0.75 and j = 0.71. The K2SO4 crystals produced were of high purity, containing maximal 0.51 wt% Mg impurity, and were received with ~73% yield at 5 °C.

Absorption efficiency analysis and optical resonator simulation of Ho:YLF laser pumped with Tm:fiber laser

In this paper, a Tm:fiber laser pumped Ho:YLF laser is simulated. The absorption efficiency, optimum crystal length, and optical resonator are analytically studied and simulated using LASCAD software, and the atomic-level degeneracies are considered in evaluating the absorption efficiency. In this way, the absorption efficiencies of 65% and 87% are obtained for single-pass 30 mm Ho:YLF crystal with doping concentration 0.5% and 1% respectively. These calculated efficiencies are verified by our experimental measurements and they coincide with acceptable errors. To estimate a proper length for the Ho:YLF crystal with specified doping concentration, the up-conversion, and the reabsorption effects are considered. As a result, we find the 30 mm length crystal is suited for reducing the absorption threshold and prohibiting reabsorption while saturation is controlled. The threshold power and slope efficiency for 65 W pumped powers are calculated by LASCAD software, and the thermal lens focal length of −665 mm is obtained. For a nearly constant beam width inside the cavity and suitable beam overlap efficiency, a concave-concave configuration is chosen for the optical resonator. In the continuous-wave operation, the output power is funded to be 38.4 W and the slope efficiency would be 66%.