Phonons near Peierls Structural Transition in Quasi-One-Dimensional Organic Crystals of TTF-TCNQ

The Peierls structural transition in quasi-one-dimensional organic crystals of TTF-TCNQ is investigated in the frame of a more complete physical model. The two most important electron-phonon interaction mechanisms are taken into account simultaneously. One is similar of that of deformation potential and the other is of polaron type. For simplicity, the 2D crystal model is considered. The renormalized phonon spectrum and the phonon polarization operator are calculated in the random phase approximation for different temperatures. The effects of interchain interaction on renormalized acoustic phonons and on the Peierls critical temperature are analyzed.

Structure Prediction Based on Hydrophobic to Hydrophilic Volume Ratios in Small Molecule Amphiphilic Organic Crystals

The structure type for the crystal of 4,4'-bis-(2-hydroxy-ethoxyl)-biphenyl 1 has been predicted by using the previously developed interfacial model for small organic molecules. Based on the calculated hydrophobic to hydrophilic volume of 1, this model predicts the crystal structure to be of lamellar or bicontinuous type, which has been confirmed by the X-ray single-crystal structure analysis (C20H26O6, monoclinic, P21/C, a = 16.084(1), b = 6.0103(4), c = 9.6410(7) A, β9 = 103.014(2)°, V= 908.1(1) A3, Z = 2, Dc= 1.325 g/cm3, F(000)=388,μ = 0.097 mm-1, MoKα radiation, λ = 0.71073 A, R = 0.0382 and wR = 0.0882 with I > 2σ(I) for 7121 reflections collected, 1852 unique reflections and 170 parameters). As predicted, the hydrophobic and hydrophilic portions of 1 form in the lamellae. The same interfacial model is applied to other amphilphilic small molecule organic systems for structural type prediction.

Peierls Structural Transition in Q1D Organic Crystals of TTT<SUB>2</SUB>I<SUB>3</SUB>for Different Values of Carrier Concentration

The Peierls structural transition in the TTT2I3 (tetrathiotetracene-iodide) crystal, for different values of carrier concentration is studied in 3D approximation. A crystal physical model is applied that considers two of the most important hole-phonon interactions. The first interaction describes the deformation potential and the second one is of polaron type. In the presented physical model, the interaction of carriers with the structural defects is taken into account. This is crucial for the explanation of the transition. The renormalized phonon spectrum is calculated in the random phase approximation for different temperatures applying the method of Green functions. The renormalized phonon frequencies for different temperatures are presented in two cases. In the first case the interaction between TTT chains is neglected. In the second one, this interaction is taken into account. Computer simulations for the 3D physical model of the TTT2I3 crystal are performed for different values of dimensionless Fermi momentum kF, that is determined by variation of carrier concentration. It is shown that the transition is of Peierls type and strongly depends on iodine concentration. Finally, the Peierls critical temperature was determined.

Surface doping effect on the optoelectronic performance of 2D organic crystals based on cyano-substituted perylene diimides

Compared to organic thin films,organic single crystals offer significant potential in organic phototransistors(OPTs)due to their enhanced charge transport,large surface area,and defect-free nature.However,the development of n-type semiconductors has lagged behind p-type semiconductors.To enhance semiconductor device performance,a doping process can be employed,which typically involves the introduction of charged impurities into the crystalline semiconducting material.Its aim is to reduce the Ohmic losses,increase carrier density,improve transport capabilities,and facilitate effective carrier injection,ultimately enhancing the electrical properties of the material.Traditional doping processes,however,often pose a risk of damaging the structure of single crystals.In this study,we have synthesized novel cyanosubstituted chiral perylene diimides,which self-assemble into two-dimensional single crystals that can be used for n-type semiconductor devices.We have employed a surface doping strategy using diethylamine vapor without disrupting the crystal structure.The fabricated devices exhibit significantly higher charge transport properties after doping,achieving a maximum electron mobility of 0.14 cm^(2)V^(-1)s^(-1),representing an improvement of over threefold.Furthermore,the optoelectronic performance of the doped devices has significantly improved,with the external quantum efficiency increased by over 9 times and the significantly improved response time.These results suggest that our surface doping technology is a promising way for enhancing the performance of 2D organic single-crystal OPTs.

Schiff base flexible organic crystals toward multifunctional applications

The emergence offlexible organic crystals changed the perception of molecu-lar crystals that were regarded as brittle entities over a long period of time,and sparked a great interest in exploring mechanically compliant organic crystalline materials toward next-generation smart materials during the past decade.Schiff base compounds are considered to be one of the most promising candidates forflexible organic crystals owing to their easy synthesis,high yield,stimuli respon-siveness and good mechanical properties.This paper gives an overview of the recent development of Schiff baseflexible organic crystals(including elastic organic crystals,plastic organic crystals,andflexible organic crystals integrating elastic-ity and plasticity)from serendipitous discovery to design strategies and versatile applications such as stimuli responses,optical waveguides,optoelectronic devices,biomimetic soft robots,and organic photonic integrated circuits.Notably,atomic force microscopy-micromanipulation technique has been utilized to bring the mul-tifunctional applications offlexible organic crystals from the macroscopic level to the microscopic world.Since understanding mechanicalflexibility at the molec-ular level through crystal engineering can assist us to trace down the structural origin of mechanical properties,we focus on the packing structures of various Schiff baseflexible organic crystals driven by non-covalent intermolecular inter-actions and their close correlation with mechanical behaviors.We hope that the information given here will help in the design of novelflexible organic crys-tals combined with other unique properties,and promote further research into the area of mechanically compliant organic crystalline materials toward multifunctional applications.

Flexible Organic Crystal with Two-Dimensional Elastic Bending and Recoverable Plastic Twisting for Circularly Polarized Luminescence

Multidimensional mechanical flexible organic crystals with tunable optoelectronic properties hold significant promise for practical application in complicated environmental conditions.Herein,based on a newly designed“flexible”Schiff base small molecule with chirality,we presented a compatibly bendable and twistable organic single crystal with circularly polarized luminescence for the first time.First,the twodimensional elastic bending of the chiral crystal was realized at both room and liquid nitrogen temperatures,along with recoverable plastic twisting at room temperature.Besides,circular dichroism and circularly polarized luminescence spectroscopy were employed to characterize the chiral enantiomer in solution and the solid state.Our design strategy provides a new perspective for the future construction of chiroptical flexible crystal materials.

Side-Chain Engineering of Organic Crystals for Lasing Media with Tunable Flexibility

Abundant high-performance organic crystals have been reported in the past decades;however,applications of crystalline materials are seriously restricted by their notorious brittleness.Recently,some organic crystals have been designed to be deformable in response to stress,light,heat,or humidity;nevertheless,the development of flexible organic crystals currently relies on a molecular framework design.So far there is no effective strategy for constructing organic crystals with tunable flexibility based on the same luminescent skeleton.Herein,we propose a side-chain engineering strategy aimed at facilely modulating the mechanical compliance of organic crystals.Subtly changing the side chains of a single-benzeneπ-skeleton greatly alters the mechanical behaviors while maintaining the unique optical functions of the produced crystals.Optical waveguides and amplified spontaneous emissions were measured to evaluate the application potentials of the flexible crystals as soft optical transducing media.We anticipate that the proposed strategy will be expanded to regulate the mechanical compliance of other organic crystals with unique emission properties.In addition,the applications attempted preliminarily here highlight the superiority of“crystal flexibility”in flexible optoelectronics for some special application scenarios that require complex and shape changeable optical circuits.

Structure and ion transport properties of organic ionic compounds revealed by NMR

Organic ionic plastic crystals(OIPCs)are emerging as an important material family for solid-state electrolytes and many other applications.They have significant advantages over conventional electrolyte materials,such as high ionic conductivity,non-flammability,and plasticity.Various nuclear magnetic resonance(NMR)spectroscopy techniques including solid-state NMR,pulsed-field gradient(PFG)NMR,and magnetic resonance imaging(MRI)etc.,provide us a versatile toolkit to understand the fundamental level structures,molecular dynamics,and ionic interactions in these materials.This article reviews the commonly used NMR methods including solid-and solution-state NMR,PFG-NMR,dynamic nuclear polarization(DNP)and the application of these methods in revealing the microscopic level structures and ion-transport mechanisms in OIPC materials.

Organic crystal-based flexible smart materials

Although the famous brittle characteristics of molecular crystals are unfavorable when they are used as flexible smart materials(FSMs),an increasing number of organic crystal-based FSMs have been reported recently.This breaks the perception of their stiff and brittle properties and promises a bright future for basic research and practical applications.Crystalline smart materials present considerable advantages over polymer materials under certain circumstances,rendering them potential candidates for certain applications,such as rapidly responsive actuators,ON/OFF switching,and microrobots.In this review,we summarize the recent developments in the field of organic crystal-based FSMs,including the derivatives of azobenzene,diarylethene,anthracene,and olefin.These organic crystal-based FSMs can bend,curl,twist,deform,or respond otherwise to external stimuli,such as heat or light.The detailed mechanisms of their smart behaviors are discussed with their potential applications in exciting intelligent fields.We believe this review could provide guidelines toward future fabrication and developments for novel organic crystal-based FSMs and their advanced smart applications.

Ultralong Room-Temperature Phosphorescence of Silicon-Based Pure Organic Crystal for Oxygen Sensing

Quantitative oxygen detection is of great importance in biological fields,complex environments,and chemical process engineering.Due to the high sensitivity and rapid response of long-lived phosphorescence to oxygen,pure organic room-temperature phosphorescence(RTP)for oxygen detection has recently attracted considerable interest.However,to simultaneously achieve ultralong phosphorescence at room temperature and quantitative oxygen detection from pure organic crystals is difficult.Tight packing to restrict nonradiative decay is not apt to allow oxygen diffusion for sensing.Reported herein is an exceptional example,that is,a crystal of simple carbazole molecules that bridges with an ethoxysilane(DCzC2OSi)and is capable of oxygen sensing with remarkable sensitivity.Photophysical studies and single-crystal structure analysis reveal that DCzC2OSi crystals display ultralong RTP and suitable oxygen diffusion channels from its butterfly-like tetrahedron geometry.Further comparisons with the crystals of CzC2OH and DCzSi verify the important roles of silicon and ethoxy groups of DCzC2OSi for both enhanced phosphorescence lifetime and oxygen sensitivity.When the crystals of DCzC2OSi were doped into polymer,the lifetime-based oxygen sensor exhibited high KSV(5.308 kPa^(−1))with full reversibility,which is attractive for the development of practical oxygen sensors from pure organic crystals.

Distribution of Crystal Organic Fertilizer-N in Soil-plant System

The distribution of crystal organic fertilizer, urea and compound fertilizer-N in soil and plant system was researched with 15N-trace under tobacco pot experiment. The results showed that the leaf yield of tobacco used crystal organic fertilizer was 23.1% and 14.6% higher than that of urea and compound fertilizer treatments respectively. Compound fertilizer also resulted in higher yield of 8.5 % comparing with the urea treatment. Nitrogen content of the plant from the crystal organic fertilizer treatment was 138. 6% and 145.7% as high as that of the compound fertilizer and urea treatments respectively. The absorbed N from the organic fertilizer was 25.1% and 27.9% more than that from the compound fertilizer and urea respectively. However, the absorbed N from the soil with the organic fertilizer was 47.4% and 58.3% more than that with compound fertilizer and urea respectively. The N use efficiency of the organic fertilizer was 9.4% and 10.1% higher than that of the compound fertilizer and urea. It indicated that the crystal organic fertilizer not only had high N use efficiency, but also stimulated tobacco taking up more N from soil.

ORGANIC NONLINEAR OPTICAL CRYSTAL:N-(4-NITROPHENYL)-(s)-(+)-2-PYRROLIDINEMETHYLENE TOSYLATE(NPP-OTs)

Large crystal NPP-OTs has been obtained by growth from solution,its powder SHG efficiency is 1/3 of urea.It shows it is a new convenient approach to obtain organic second-order NLO crystal:the dipole-dipole interaction is oppos- ed by introducing a large side group.

GROWTH OF o-DICYANOVINYL ANISOLE(DIVA) CRYSTAL IN ORGANIC SOLVENTS

Crystal growth habits of O-Dicyanovinyl anisole (DIVA) in organic solvents are described

Organic Melt Crystallization as a Method for Synthesis of Supramolecular Complexes

The most simple method for solventless synthesis of supramolecular complex of CMCR·2BPY·BZP, [CMCR = C-methylcalix[4]resorcinarene, BPY = 4,4'-bipyridine, BZP = benzophenone], is proposed. Although CMCR by itself is high melting point compound (above 300°C), CMCR was found to be dissolved in melt mixture of BPY and BZPeven below 120°C. In the mixture of the three components, the reaction occurs to form CMCR·2BPY·BZP supramolecular complex.

Optical-induced dielectric tunability properties of DAST crystal in THz range

The optical-induced dielectric tunability properties of DAST crystal in THz range were experimentally demonstrated.The DAST crystal was grown by the spontaneous nucleation method(SNM) and characterized by infrared spectrum. With the optimum wavelength of the exciting optical field, the transmission spectra of the DAST crystal excited by 532 nm laser under different power were measured by terahertz time-domain spectroscopy(THz-TDS) at room temperature. The transmitted THz intensity reduction of 26 % was obtained at 0.68 THz when the optical field was up to 80 m W. Meanwhile,the variation of refractive index showed an approximate quadratic behavior with the exciting optical field, which was related to the internal space charge field of photorefractive phenomenon in the DAST crystal caused by the photogenerated carrier.A significant enhancement of 13.7 % for THz absorption coefficient occurred at 0.68 THz due to the photogenerated carrier absorption effect in the DAST crystal.

Irradiation Effect on Second Harmonic Generation of Dyes Doped KDP Crystals

Most irradiation studies in the hydrogen bonded ferroelectrics have been concentrated on the transient defects induced by ionising radiation, such as ultraviolet （UV） light, where the defects are closely related to the optical properties. But heavy ion beam irradiation effects have rarely been studied. The structural, optical, and non-linear optical properties of the doped crystals were analyzed with the characterization studies, such as powder XRD, UV-Visible and second harmonic generation （SHG） measurements, respectively. The results for doped KDP crystal were compared with the results of the pure KDP crystals. The experiment results showed that Li^3＋ irradiation leads to the development of a well-defined surface H peak in dye doped KDP crystals. The stability of KDP single crystal was improved by doping organic dyes. The nano-islands of dye in KDP were likely to be dissolved and enhance the non-linear optical properties of these materials.

Synthesis of a Highly Crystalline Amide-Linked Covalent Organic Framework

The dilemma for the synthesis of covalent organic frameworks(COFs)is crystallinity and stability.Herein,we present the synthesis of a single-crystalline amide-linked COF,and demonstrate its excellent chemical as well as thermal stabilities.This study will inspire the synthesis of a wide spectrum of highly crystalline and stable COFs,promote their structure-property investigations and boost their applications in selective gas adsorption,storage and separation.

Liquid-liquid interface‐assisted growth of two‐dimensional organic semiconductor single crystals:Mechanisms,properties,and applications

Two‐dimensional organic semiconductor single crystals(2D OSSCs)represent the promising candidates for the construction of high‐performance electronic and optoelectronic devices due to their ultrathin thicknesses,free of grain boundaries,and long‐range ordered molecular structures.In recent years,substantial efforts have been devoted to the fabrication of the large‐sized and layer‐controlled 2D OSSCs at the liquid‐liquid interface.This unique interface could act as the molecular flat and defect‐free substrate for regulating the nucleation and growth processes and enabling the formation of large‐sized ultrathin 2D OSSCs.Therefore,this review focuses on the liquid-liquid interface‐assisted growth methods for the controllable preparation of 2D OSSCs,with a particular emphasis on the advantages and limitations of the corresponding methods.Furthermore,the typical methods employed to control the crystal sizes,morphologies,structures,and orientations of 2D OSSCs at the liquid-liquid interface are discussed in detail.Then,the recent progresses on the 2D OSSCs‐based optoelectronic devices,such as organic field‐effect transistors,ambipolar transistors,and phototransistors are highlighted.Finally,the key challenges and further outlook are proposed in order to promote the future development of the 2D OSSCs in the field of the next‐generation organic optoelectronic devices.

Vapor-Induced Coating Method for Well-Aligned and Uniform Organic Semiconductor Single Crystals

Uniform and well-aligned organic semiconductor single crystals(OSSCs)are critical for high-performance electronic and optoelectronic device applications due to their long-range order and low defect density.However,it is still challenging to fabricate uniform and well-aligned OSSCs by an efficient and facile method.Here,we report a vapor-induced coating method to prepare uniform organic semiconductor stripe single crystals with well-aligned orientation.The coating velocity and solution concentration are important to control the stripe crystals’morphology,which influence the triple-phase contact line dewetting behavior and then change the mass transport of the meniscus.Insufficient solute supply causes the generation of dendritic crystals.Uniform stripe single crystals of high quality and pure orientation are prepared in the condition of a sufficient and suitable solute supply.Moreover,the electronic and optoelectronic properties are evaluated.Notably,the polarization-sensitive photodetectors based on the uniform stripe crystals exhibit high polarization sensitivity and its dichroic ratio of photocurrent is 1.98.This method is efficient for the preparation of various high-quality and uniform organic semiconductor stripe single crystals,opening an opportunity for high-performance organic functional devices.