High-performance carbon nanofibers are highly dependent on the performance of their precursors,especially polyacrylonitrile(PAN).In this work,the copolymer of PAN(coPAN)was synthesized for electrospinning.A self-assem...High-performance carbon nanofibers are highly dependent on the performance of their precursors,especially polyacrylonitrile(PAN).In this work,the copolymer of PAN(coPAN)was synthesized for electrospinning.A self-assembling set-up was used for the stretching of single coPAN nanofibers.FTIR and Raman spectroscopies were used to characterize the chemical structure of coPAN nanofibers.Scanning electron microscopy(SEM)and atomic force microscopy(AFM)were used to monitor the morphology of single coPAN nanofibers under different drawing times.Micro-tensile test was used to determine the mechanical properties of single coPAN nanofibers.The results indicated that the drawing led to an increase in degree of molecular orientation along the fiber axis from 0.656 to 0.808,tensile strength from 304 MPa to 595 MPa,and modulus from 3.1 GPa to 12.4 GPa.This research would provide fundamental information of high-performance electrospun coPAN nanofibers and offer opportunities for the preparation of high-performance carbon nanofibers.展开更多
Sum frequency generation(SFG) vibrational spectroscopy has been proven an excellent tool to measure the molecular structures, symmetries and orientations at surfaces/interfaces because of its strong polarization depen...Sum frequency generation(SFG) vibrational spectroscopy has been proven an excellent tool to measure the molecular structures, symmetries and orientations at surfaces/interfaces because of its strong polarization dependence. However, a precise quantitative analysis of SFG spectral intensity and molecular orientation at interfaces must be carefully performed. In this work, we summarized the parameters and factors that are often ignored and illustrated them by evaluating studies of CO adsorption on the(111) facet of platinum(Pt) and palladium(Pd) single crystals at the gas(ultra-high vacuum, UHV)/solid interfaces and methanol(water) adsorption at the air/liquid(solid/liquid) interfaces in the presence of sodium iodide(chloride) salts. To intuitively estimate the influence of incidence angles and refractive indices on the SFG intensity, solely a defined factor of|Fyyz| was discussed, which can be individually separated from the macroscopic second-order non-linear susceptibility χ yyz^(2) term and represents the SSP intensity. Moreover, effects of refractive indices and the molecular hyperpolarizability ratio(R) were discussed in the orientational analysis of interfacial CO and methanol molecules. When IPPP/ISSP was identical, molecules with a larger R had smaller tilting angles(q) on Pt(assuming q < 51°), and CO molecules on Pd would tilt much closer to the surface than they did on Pt. A total internal reflection(TIR) geometry enhanced the SFG intensity, but it also amplified the influence of refractive index on SFG intensity at the solid(silica)/liquid interface. The refractive index and R-value had similar influence on the methanol orientation in the presence of sodium iodide salts at air/liquid and solid/liquid interfaces. This work should provide a guideline for analyzing the orientation of molecules with different R, which are adsorbed on catalysts or located at liquid interfaces involving changes of refractive indices.展开更多
A density functional theory （DFT） is used to investigate molecular orientation of hard rod fluids in a hard slit. The DFT approach combines a modified fundamental measure theory （MFMT） for excluded-volume effect w...A density functional theory （DFT） is used to investigate molecular orientation of hard rod fluids in a hard slit. The DFT approach combines a modified fundamental measure theory （MFMT） for excluded-volume effect with the first order thermodynamics perturbation theory for chain connectivity. In the DFT approach, the intra-molecular bonding orientation function is introduced. We consider the effects of molecular length （i.e. aspect ratio of rod） and packing fraction on the orientations of hard rod fluids and flexible chains. For the flexible chains, the chain length has no significant effect while the packing fraction shows slight effect on the molecular orientation distribution. In contrast, for the hard rod fluids, the chain length determines the molecular orientation distribution, while the packing fraction has no significant effect on the molecular orientation distribution. By making a comparison between molecular orientations of the flexible chain and the hard rod fluid, we find that the molecular stiffness distinctly affects the molecular orientation. In addition, partitioning coefficient indicates that the longer rodlike molecule is more difficult to enter the confined phase, especially at low bulk packing fractions.展开更多
The effects of the characteristics of molecules and external fields on field-free molecular orientation are investigated through the comparison of HBr with LiH driven by the combination of a two-color laser pulse and ...The effects of the characteristics of molecules and external fields on field-free molecular orientation are investigated through the comparison of HBr with LiH driven by the combination of a two-color laser pulse and a time-delayed THz laser pulse. It is shown that the dipole interaction has greater influence on field-free orientation than the hyperpolarizability interaction. In addition to the temperature dependence of orientation degree, the effects of the amplitudes of the two-color laser pulse and THz laser pulse, rising time, and THz laser frequency on molecular orientation are also discussed.展开更多
ITIC is the milestone of non-fullerene small molecule acceptors used in organic solar cells. We study the electronic states and molecular orientation of ITIC film using photoelectron spectroscopy and x-ray absorption ...ITIC is the milestone of non-fullerene small molecule acceptors used in organic solar cells. We study the electronic states and molecular orientation of ITIC film using photoelectron spectroscopy and x-ray absorption spectroscopy. The negative integer charge transfer energy level is determined to be 4.00 ± 0.05 eV below the vacuum level, and the ionization potential is 5,75 ±0.10 eV. The molecules predominantly have the face-on orientation on inert substrates as long as the surfaces of the substrates are not too rough. These results provide the physical understanding of the high performance of ITIC-based solar ceils, which also afford implications to design more advanced photovoltaic small molecules.展开更多
The orientation and structural characterization of the ultrathin film of azobenzene-containing amphiphilic compound, C_ 12AzoNaph(1,4)C_6N +Br -, were studied in the present study. The compound can form a stable m...The orientation and structural characterization of the ultrathin film of azobenzene-containing amphiphilic compound, C_ 12AzoNaph(1,4)C_6N +Br -, were studied in the present study. The compound can form a stable monolayer with sodium dextrin sulfate(SDS) by means of electrostatic interaction. Fourier-transform infrared(FT-IR) and near-infrared surface-enhanced Raman scattering(NIR-SERS) spectroscopies were used to study the orientation and characterize the structure of the Langmuir-Blodgett(LB) film and the dipping film. The FT-IR spectra indicate that the alkyl tail is nearly perpendicular to the substrate surface without any aggregation and adopts largely trans-zigzag conformation in the LB film. The NIR-SERS spectra demonstrate that the chromorphoric part in C_ 12AzoNaph(1,4)C_6N +Br is also nearly perpendicular to the surface of silver substrate both in the dipping film and the LB film. A new 'sandwiched system' model was designed to investigate the orientation and structural characterization of the chromophoric part in the multi-monolayer LB films on the non-SERS active substrate. The SERS mechanism of the 'sandwiched system' is discussed in the present paper.展开更多
Molecular packing patterns are crucial factors determining electron/energy transfer processes that are critical for the optoelectronic properties of organic thin film devices.Herein,the polarization-selective ultravio...Molecular packing patterns are crucial factors determining electron/energy transfer processes that are critical for the optoelectronic properties of organic thin film devices.Herein,the polarization-selective ultraviolet/infrared(UV/IR)mixed frequency ultrafast spectroscopy is applied to investigate the relative molecular orientations in two organic thin films of 7-(diethylamino)coumarin-3-carboxylic acid(DEAC)and perylene.The signal anisotropy changes caused by intermolecular energy/electron transfers are utilized to calculate the cross angles between the electronic transition dipole moment of the donor and the vibrational transition dipole moments of the acceptor,yielding the relative orientation between two adjacent molecules.Using this method,the relative orientation angle in DEAC film is determined to be 53.4°,close to 60°of its single crystalline structure,and that of the perylene film is determined to be 6.2°,also close to-0.2°of its single crystalline structure.Besides experimental uncertainties,the small difference between the angles determined by this method and those of single crystals also results from the fact that the thin film samples are polycrystalline where some of the molecules are amorphous.展开更多
The coherent control of field-free molecular orientation of CO with combined femtosecond single- and dual-color laser pulses has been theoretically studied. The effect of the delay time between the femtosecond single-...The coherent control of field-free molecular orientation of CO with combined femtosecond single- and dual-color laser pulses has been theoretically studied. The effect of the delay time between the femtosecond single- and dual-color laser pulses is discussed, and the physical mechanism of the enhancement of molecular orientation with pre-alignment of the molecule is investigated. It is found that the basic mechanism is based on the creation of a rotational wave packet by the femtosecond single-color laser pulse. Furthermore, we investigate the interference between multiple rotational excitation pathways following pre-alignment with femtosecond single-color laser pulse. It is shown that such interference can lead to an enhancement of the orientation of CO molecule by a factor of 1.6.展开更多
The performance of organic solar cells is significantly influenced by the acceptor molecular packing properties within the active layers,which is essential for optimizing charge dynamics and photovoltaic performance.H...The performance of organic solar cells is significantly influenced by the acceptor molecular packing properties within the active layers,which is essential for optimizing charge dynamics and photovoltaic performance.However,achieving precise control over this packaging structure presents a considerable challenge.Herein,we propose a dual additive strategy utilizing dibenzofuran and halogenated naphthalene to systematically manipulate molecular packing orientation and enhance the long-range molecular packing order of the acceptors.Dibenzofuran is crucial in promoting crystallinity within the material,facilitating the formation of an ordered structure,while halogenated naphthalene regulates the orientation of the molecules,ensuring proper alignment.Specifically,the combination of dibenzofuran and 1-chloronaphthalene promotes edge-on molecular packing and enhances the formation of nanofibrillar structures with improved order,leading to improved charge transport and device performance.Implementing this strategy in devices composed of PM6 and L8-BO has yielded a power conversion efficiency of 19.58%,accompanied by long-term stability.Similarly,1-fluoronaphthalene has also demonstrated effectiveness in improving molecular orientation and overall device efficiency,demonstrating the robustness of this dual additive strategy.By addressing the challenges associated with molecular packing and orientation in active layers,our result contributes valuable insights into optimizing organic solar cells for practical applications.展开更多
This study shows the unexpected and counterintuitive possibility of simultaneously orienting a molecule while delocalizing its molecular axis in a plane in field-free conditions.The corresponding quantum states are ch...This study shows the unexpected and counterintuitive possibility of simultaneously orienting a molecule while delocalizing its molecular axis in a plane in field-free conditions.The corresponding quantum states are characterized,and different control strategies using shaped terahertz(THz)laser pulses are proposed to reach such states at zero and nonzero temperatures.The robustness against temperature effects of a simple control procedure combining a laser and a THz pulse is shown.Such control strategies can be applied not only to linear molecules but also to symmetric top molecules.展开更多
The degree of polymer chain orientation is a key structural parameter that determines the mechanical and physical properties of fibers.However,understanding and significantly tuning the orientation of fiber macromolec...The degree of polymer chain orientation is a key structural parameter that determines the mechanical and physical properties of fibers.However,understanding and significantly tuning the orientation of fiber macromolecular chains remain elusive.Herein,we propose a novel electrospinning technique that can efficiently modulate molecular chain orientation by controlling the electric field.In contrast to the typical electrospinning method,this technique can piecewise control the electric field by applying high voltage to the metal ring instead of the needle.Benefiting from this change,a new electric field distribution can be realized,leading to a non-monotonic change in the drafting force.As a result,the macromolecular chain orientation of polyethylene oxide(PEO)nanofibers was significantly improved with a recordhigh infrared dichroic ratio.This was further confirmed by the sharp decrease in the PEO jet fineness of approximately 80%and the nanofiber diameter from 298 to 114 nm.Interestingly,the crystallinity can also be adjusted,with an obvious drop from 74.9%to 31.7%,which is different from the high crystallinity caused by oriented chains in common materials.This work guides a new perspective for the preparation of advanced electrospun nanofibers with optimal orientation–crystallinity properties,a merited feature for various applications.展开更多
Based on the reaction microscope at the institute of modern physics, the reaction mechanism in molecular ion-atom collisions is investigated experimentally. The features of this system is illustrated by a kinematicall...Based on the reaction microscope at the institute of modern physics, the reaction mechanism in molecular ion-atom collisions is investigated experimentally. The features of this system is illustrated by a kinematically complete experhnent performed for the collision process. Using the so-called list-mode data recording technique and the coincidence measurement, the momentum vector of each fragment from the molecular ion were recorded event by event. The orientation of the molecular axis for H2^＋ dissociation reactions could be determined for each event in the off-line analysis. The measured orientation of the molecular ion is believed the same as the one at the instance of collision under axial recoil approximation. The polar angle resolution of the molecular orientation of ±8° was obtained.展开更多
As dipyranylidenes are excellent hole carriers, applications in organic solar cells or organic light emitting diode are envisaged. In the present study, we investigate the morphology of 2,2＇,6,6＇-tetraphenyl-4,4＇-d...As dipyranylidenes are excellent hole carriers, applications in organic solar cells or organic light emitting diode are envisaged. In the present study, we investigate the morphology of 2,2＇,6,6＇-tetraphenyl-4,4＇-dipyranylidene （DIPO-Ph4） deposited under vacuum on a silicon nitride （Si3N4） substrate, a paradigmatic system for the study of molecular crystal/inorganic substrate interfaces. Samples with various coating ratios and different thermal treatments were prepared. The films were characterized by atomic force microscopy and scanning transmission X-ray microscopy to gain insight into material growth. The results show a change in orientation at a molecular level depending upon the evaporation conditions. We are now able to tailor an organic layer with a specific molecular orientation and a specific electronic behavior.展开更多
A bulk heterojunction in organic solar cells is where charge separation and recombination occur.Molecular orientation at the interface is one of the key factors that dictate solar cell efficiency.Although X-ray scatte...A bulk heterojunction in organic solar cells is where charge separation and recombination occur.Molecular orientation at the interface is one of the key factors that dictate solar cell efficiency.Although X-ray scattering-based methods can determine donor/acceptor domain orientations between an anisotropic phase and an isotropic fullerene-based phase,the rise of nonfullerene solar cells presents a new challenge in delineating local molecular directions at the interface between two anisotropic donor/acceptor domains.Here,we determine interfacial molecular orientations of three high-efficiency small molecule solar cells(ZR1:Y6,B1:BO-4 Cl,and BTR:BO-4 Cl)using polarization-selective transient absorption spectroscopy.The polarization anisotropy of charge separation dynamics indicates an angle of~90°between ZR1 and Y6 molecules at the interface,an angle close to 0°between B1 and BO-4 Cl,and random orientations between BTR and BO-4 Cl.These observations provide complementary information to X-ray scattering measurements and highlight polarization-selective transient absorption spectroscopy as a tool to probe interfacial structure and dynamics of key photophysical steps in energy conversion.展开更多
Molecular dynamics simulation is employed to study the tension and compression deformation behaviors of magnesium single crystals with different orientations.The angle between the loading axis and the basal direction ...Molecular dynamics simulation is employed to study the tension and compression deformation behaviors of magnesium single crystals with different orientations.The angle between the loading axis and the basal direction ranges from 0° to 90°.The simulation results show that the initial defects usually nucleate at free surfaces,but the initial plastic deformation and the subsequent microstructural evolutions are various due to different loading directions.The tension simulations exhibit the deformation mechanisms of twinning,slip,crystallographic reorientation and basal/prismatic transformation.The twinning,crystallographic reorientation and basal/prismatic transformation can only appear in the crystal model loaded along or near the a-axis or c-axis.For the compression simulations,the basal,prismatic and pyramidal slips are responsible for the initial plasticity,and no twinning is observed.Moreover,the plastic deformation models affect the yield strengths for the samples with different orientations.The maximum yield stresses for the samples loaded along the c-axis or a-axis are much higher than those loaded in other directions.展开更多
The adsorption and molecular orientation of Dy@Cs2 isomer I on Au（111） has been investigated using ultrahigh-vacuum scanning tunneling microscopy at 80 K. At low coverages, the Dy@Cs2 molecules tend to grow along th...The adsorption and molecular orientation of Dy@Cs2 isomer I on Au（111） has been investigated using ultrahigh-vacuum scanning tunneling microscopy at 80 K. At low coverages, the Dy@Cs2 molecules tend to grow along the step edges of Au（111）, forming small clusters and molecular chains. Adsorption of Dy@Cs2 on the edges is dominated by the fullerene-substrate interaction and presents various molecular orientations. At higher coverages, the Dy@Cs2 is found to form ordered islands consisting of small domains of equally oriented molecules. The Dy@Cs2 molecules in the islands prefer the adsorption configurations with the major C2 axis being approximately parallel to the surface of the substrate. Three preferable orientations of the Dy@Cs2 molecules are found in a two-dimensional hexagonal close packed overlayer. These observations are attributed to the interplay of the fullerene-substrate interaction and dipole-dipole interaction between the metallofullerenes.展开更多
In insects,the sense of smell is mainly mediated by olfactory receptors（Ors）.Olfactory co-receptor（Orco）,which is coexpressed with the Ors in almost all olfactory receptor neurons（ORNs）,is demonstrated to be an ...In insects,the sense of smell is mainly mediated by olfactory receptors（Ors）.Olfactory co-receptor（Orco）,which is coexpressed with the Ors in almost all olfactory receptor neurons（ORNs）,is demonstrated to be an essential component in the insect olfactory system.It can be potential target for developing novel olfactory-disruption strategy to control insect pests.In this study,two full-length cDNA sequences encoding Orcos（CmedOrco and ChsupOrco） were cloned from two Lepidopteran rice pests,the rice leaffolder,Cnaphalocrocis medinalis and the rice striped stem borer,Chilo suppressalis.The amino acid sequences of CmedOrco and ChsupOrco showed high similarity to the previously identified Orcos from other insect species. Bioinformatic prediction and cellular immunofluorescence indicated that CmedOrco and ChsupOrco were both seven-transmembrane proteins with intracellular N-termini and extracellular C-termini.mRNA expression levels of the two Orcos were much higher in male and female antennae than those in non-olfactory tissues,and the ChsupOrco transcripts reached a peak level in adults compared to other life stages.Our results provide a foundation from which it will be possible to elucidate the roles of Orco in moth olfaction and for the development of environment-friendly management strategies of these two rice insect pests.展开更多
A redox-active monolayer on an optically transparent electrode constitutes a typical platform for spectroelectrochemical sensing.The necessity for its sophistication arises from the availability of multi-dimensional s...A redox-active monolayer on an optically transparent electrode constitutes a typical platform for spectroelectrochemical sensing.The necessity for its sophistication arises from the availability of multi-dimensional sensing signals.Simultaneous monitoring of the redox current and color change synchronized with the oxidation state change significantly enhances sen-sitivity and selectivity.This study aimed to elucidate the modification of an indium tin oxide(ITO)electrode with a viologen monolayer with an ordered orientation.Novel methods were developed to immobilize a viologen molecule bearing a car-boxyl group to form assembled monolayers through a condensation reaction using 1-ethyl-3-(3-dimethylaminopropyl)-car-bodiimide with N-hydroxy-succinimide(EDC/NHS).In the two methods of immobilization,one utilizes a two-step process to firstly form an aromatic siloxane base layer and subsequently attach the viologen derivative through an amide linkage by post-amidation.The other employs a direct ester linkage between the hydroxyl groups of the ITO surface and the car-boxyl group of the viologen derivative.The latter method was also applied to immobilize a ferrocenyl group at a very short distance from the ITO surface.Potential-modulated UV-visible transmission absorption spectral measurement techniques with oblique incidence of plane-polarized light were employed to determine the orientation of the longitudinal axis of the reduced form of the viologen.The frequency dependence data of the potential-modulated transmission absorption signals were utilized to analyze the electron transfer kinetics.The performance of the two viologen-modified electrodes was com-pared to that of an ITO modified by post-amidation to the most commonly used base layer prepared with 3-aminopropyl triethoxysilane.展开更多
Bithiophene imide (BTI)-based polymers have been promising photovoltaic materials due to their high mobility and tunable energy levels. However, BTI polymers have rarely been revisited since organic solar cells (OSCs)...Bithiophene imide (BTI)-based polymers have been promising photovoltaic materials due to their high mobility and tunable energy levels. However, BTI polymers have rarely been revisited since organic solar cells (OSCs) entered the era of non-fullerene electron acceptors (NFEA) likely owing to their incompatibility with NFEAs. Herein, fine-tuning the aggregation and orientation of BTI-based donor-π-acceptor (D-π-A) polymer donors was achieved by incorporating the linear n-octyl group into thiophene π-bridge. The resulting polymer donor G15 shows excellent compatibility with NFEA L15 (polymer acceptor). The G15-based all-polymer OSCs achieve high power conversion efficiency of 15.17%. This is significantly higher than that (< 5%) of its analogue with isomerized branched alkyl chains and also among the highest values for all-polymer OSCs. The results highlight that well-tailored BTI polymer donors are attractive photovoltaic materials for further exploration in non-fullerene organic solar cells.展开更多
Nonfused ring electron acceptors(NFREAs)are promising candidates for future commercialization of organic solar cells(OSCs)due to their simple synthesis.Still,the power conversion efficiencies(PCEs)of NFREA-based OSCs ...Nonfused ring electron acceptors(NFREAs)are promising candidates for future commercialization of organic solar cells(OSCs)due to their simple synthesis.Still,the power conversion efficiencies(PCEs)of NFREA-based OSCs have large room for improvement.In this work,by merging end group halogenation and side chain engineering,we developed four A-D-A’-D-A type NFREAs,which we refer to as EH-4F,C4-4F,EH-4Cl,and C4-4Cl.Single crystal X-ray diffraction revealed that multiple intermolecular S⋅⋅⋅F interactions between cyclopentadithiophene and 5,6-difluoro-3-(dicyanomethylene)indanone could cause an unfavorable dimer formation,leading to ineffectiveπ-πstackings in EH-4F and C4-4F,whereas no such dimer was found in EH-4Cl and C4-4Cl after replacing with 5,6-dichloro-3-(dicyanomethylene)indanone.Moreover,although the shorter n-butyl side chain resulted in a closer molecular packing in C4-4Cl,EH-4Cl(2-ethylhexyl substitution)with proper crystallinity exhibited enhanced face-on orientation in thin film,which is favorable for vertical charge transport and further reducing charge recombination.As a result,a PCE of 13.0%is obtained for EH-4Cl-based OSC with a fill factor of 0.70.This work highlights the importance of molecular packing and orientation control toward future high-performance A-D-A’-D-A type NFREAs.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.21774053,21975111,and 51903123)Natural Science Foundation of Jiangsu Province(No.BK20190760)+1 种基金Major Special Projects of Jiangxi Provincial Department of Science and Technology(No.20114ABF05100)Technology Plan Landing Project of Jiangxi Provincial Department of Education(No.GCJ2011-24)。
文摘High-performance carbon nanofibers are highly dependent on the performance of their precursors,especially polyacrylonitrile(PAN).In this work,the copolymer of PAN(coPAN)was synthesized for electrospinning.A self-assembling set-up was used for the stretching of single coPAN nanofibers.FTIR and Raman spectroscopies were used to characterize the chemical structure of coPAN nanofibers.Scanning electron microscopy(SEM)and atomic force microscopy(AFM)were used to monitor the morphology of single coPAN nanofibers under different drawing times.Micro-tensile test was used to determine the mechanical properties of single coPAN nanofibers.The results indicated that the drawing led to an increase in degree of molecular orientation along the fiber axis from 0.656 to 0.808,tensile strength from 304 MPa to 595 MPa,and modulus from 3.1 GPa to 12.4 GPa.This research would provide fundamental information of high-performance electrospun coPAN nanofibers and offer opportunities for the preparation of high-performance carbon nanofibers.
基金in part supported by the Austrian Science Fund FWF through projects Com Cat(I 1041-N28)and DK+Solids4Fun(W1243)by TU Wien via the Innovative Project “SFG Spectroscopy”
文摘Sum frequency generation(SFG) vibrational spectroscopy has been proven an excellent tool to measure the molecular structures, symmetries and orientations at surfaces/interfaces because of its strong polarization dependence. However, a precise quantitative analysis of SFG spectral intensity and molecular orientation at interfaces must be carefully performed. In this work, we summarized the parameters and factors that are often ignored and illustrated them by evaluating studies of CO adsorption on the(111) facet of platinum(Pt) and palladium(Pd) single crystals at the gas(ultra-high vacuum, UHV)/solid interfaces and methanol(water) adsorption at the air/liquid(solid/liquid) interfaces in the presence of sodium iodide(chloride) salts. To intuitively estimate the influence of incidence angles and refractive indices on the SFG intensity, solely a defined factor of|Fyyz| was discussed, which can be individually separated from the macroscopic second-order non-linear susceptibility χ yyz^(2) term and represents the SSP intensity. Moreover, effects of refractive indices and the molecular hyperpolarizability ratio(R) were discussed in the orientational analysis of interfacial CO and methanol molecules. When IPPP/ISSP was identical, molecules with a larger R had smaller tilting angles(q) on Pt(assuming q < 51°), and CO molecules on Pd would tilt much closer to the surface than they did on Pt. A total internal reflection(TIR) geometry enhanced the SFG intensity, but it also amplified the influence of refractive index on SFG intensity at the solid(silica)/liquid interface. The refractive index and R-value had similar influence on the methanol orientation in the presence of sodium iodide salts at air/liquid and solid/liquid interfaces. This work should provide a guideline for analyzing the orientation of molecules with different R, which are adsorbed on catalysts or located at liquid interfaces involving changes of refractive indices.
基金Project supported by the National Natural Science Foundation of China （Grant No 20646001）, the Beijing Novel Program （Grant No 2006B17）, the Program for New Century Excellent Talents in University （NCET）, the ＂Chemical Grid Program＂ and the Excellent Talent Fund of Beijing University of Chemical Technology.
文摘A density functional theory （DFT） is used to investigate molecular orientation of hard rod fluids in a hard slit. The DFT approach combines a modified fundamental measure theory （MFMT） for excluded-volume effect with the first order thermodynamics perturbation theory for chain connectivity. In the DFT approach, the intra-molecular bonding orientation function is introduced. We consider the effects of molecular length （i.e. aspect ratio of rod） and packing fraction on the orientations of hard rod fluids and flexible chains. For the flexible chains, the chain length has no significant effect while the packing fraction shows slight effect on the molecular orientation distribution. In contrast, for the hard rod fluids, the chain length determines the molecular orientation distribution, while the packing fraction has no significant effect on the molecular orientation distribution. By making a comparison between molecular orientations of the flexible chain and the hard rod fluid, we find that the molecular stiffness distinctly affects the molecular orientation. In addition, partitioning coefficient indicates that the longer rodlike molecule is more difficult to enter the confined phase, especially at low bulk packing fractions.
基金Project supported by the National Natural Science Foundation of China(Grant No.11674198)the Taishan Scholar Project of Shandong Province,Chinathe Natural Science Foundation of Shandong Province,China(Grant No.ZR2014AM002)
文摘The effects of the characteristics of molecules and external fields on field-free molecular orientation are investigated through the comparison of HBr with LiH driven by the combination of a two-color laser pulse and a time-delayed THz laser pulse. It is shown that the dipole interaction has greater influence on field-free orientation than the hyperpolarizability interaction. In addition to the temperature dependence of orientation degree, the effects of the amplitudes of the two-color laser pulse and THz laser pulse, rising time, and THz laser frequency on molecular orientation are also discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374258 and 11079028)
文摘ITIC is the milestone of non-fullerene small molecule acceptors used in organic solar cells. We study the electronic states and molecular orientation of ITIC film using photoelectron spectroscopy and x-ray absorption spectroscopy. The negative integer charge transfer energy level is determined to be 4.00 ± 0.05 eV below the vacuum level, and the ionization potential is 5,75 ±0.10 eV. The molecules predominantly have the face-on orientation on inert substrates as long as the surfaces of the substrates are not too rough. These results provide the physical understanding of the high performance of ITIC-based solar ceils, which also afford implications to design more advanced photovoltaic small molecules.
基金Supported by the Major State Basic Research Development Program( G2 0 0 0 0 7810 2 ) and the National Natural ScienceFoundation of China( No.2 0 0 0 3 0 0 4)
文摘The orientation and structural characterization of the ultrathin film of azobenzene-containing amphiphilic compound, C_ 12AzoNaph(1,4)C_6N +Br -, were studied in the present study. The compound can form a stable monolayer with sodium dextrin sulfate(SDS) by means of electrostatic interaction. Fourier-transform infrared(FT-IR) and near-infrared surface-enhanced Raman scattering(NIR-SERS) spectroscopies were used to study the orientation and characterize the structure of the Langmuir-Blodgett(LB) film and the dipping film. The FT-IR spectra indicate that the alkyl tail is nearly perpendicular to the substrate surface without any aggregation and adopts largely trans-zigzag conformation in the LB film. The NIR-SERS spectra demonstrate that the chromorphoric part in C_ 12AzoNaph(1,4)C_6N +Br is also nearly perpendicular to the surface of silver substrate both in the dipping film and the LB film. A new 'sandwiched system' model was designed to investigate the orientation and structural characterization of the chromophoric part in the multi-monolayer LB films on the non-SERS active substrate. The SERS mechanism of the 'sandwiched system' is discussed in the present paper.
基金supported by Ministry of Science and Technology of China(No.2017YFA0204702)the National Natural Science Foundation of China(No.21627805,No.21673004,No.21804004,and No.21821004)。
文摘Molecular packing patterns are crucial factors determining electron/energy transfer processes that are critical for the optoelectronic properties of organic thin film devices.Herein,the polarization-selective ultraviolet/infrared(UV/IR)mixed frequency ultrafast spectroscopy is applied to investigate the relative molecular orientations in two organic thin films of 7-(diethylamino)coumarin-3-carboxylic acid(DEAC)and perylene.The signal anisotropy changes caused by intermolecular energy/electron transfers are utilized to calculate the cross angles between the electronic transition dipole moment of the donor and the vibrational transition dipole moments of the acceptor,yielding the relative orientation between two adjacent molecules.Using this method,the relative orientation angle in DEAC film is determined to be 53.4°,close to 60°of its single crystalline structure,and that of the perylene film is determined to be 6.2°,also close to-0.2°of its single crystalline structure.Besides experimental uncertainties,the small difference between the angles determined by this method and those of single crystals also results from the fact that the thin film samples are polycrystalline where some of the molecules are amorphous.
基金Project supported by the National Natural Science Foundation of China （Grant Nos. 61077037 and 11274096）, the Doctoral Research Fund of Henan Normal University, China （Grant No. qd 12109）, and the Key Scientific and Basic Technology Research Program of Henan Province, China （Grant Nos. 102102210184 and 122300410109）.
文摘The coherent control of field-free molecular orientation of CO with combined femtosecond single- and dual-color laser pulses has been theoretically studied. The effect of the delay time between the femtosecond single- and dual-color laser pulses is discussed, and the physical mechanism of the enhancement of molecular orientation with pre-alignment of the molecule is investigated. It is found that the basic mechanism is based on the creation of a rotational wave packet by the femtosecond single-color laser pulse. Furthermore, we investigate the interference between multiple rotational excitation pathways following pre-alignment with femtosecond single-color laser pulse. It is shown that such interference can lead to an enhancement of the orientation of CO molecule by a factor of 1.6.
基金the financial support from the National Natural Science Foundation of China(62275057)the Guangxi Natural Science Foundation(2023GXNSFFA026004)+2 种基金the Guangxi Talent Program("Highland of Innovation Talents")the Shenzhen High-tech Development Special Plan-Pingshan Districts Innovation Platform Project(29853M-KCJ-2023-002-04)Industry and Energy(MOTIE),Republic of Korea(Project No.:RS-2025-02413058)。
文摘The performance of organic solar cells is significantly influenced by the acceptor molecular packing properties within the active layers,which is essential for optimizing charge dynamics and photovoltaic performance.However,achieving precise control over this packaging structure presents a considerable challenge.Herein,we propose a dual additive strategy utilizing dibenzofuran and halogenated naphthalene to systematically manipulate molecular packing orientation and enhance the long-range molecular packing order of the acceptors.Dibenzofuran is crucial in promoting crystallinity within the material,facilitating the formation of an ordered structure,while halogenated naphthalene regulates the orientation of the molecules,ensuring proper alignment.Specifically,the combination of dibenzofuran and 1-chloronaphthalene promotes edge-on molecular packing and enhances the formation of nanofibrillar structures with improved order,leading to improved charge transport and device performance.Implementing this strategy in devices composed of PM6 and L8-BO has yielded a power conversion efficiency of 19.58%,accompanied by long-term stability.Similarly,1-fluoronaphthalene has also demonstrated effectiveness in improving molecular orientation and overall device efficiency,demonstrating the robustness of this dual additive strategy.By addressing the challenges associated with molecular packing and orientation in active layers,our result contributes valuable insights into optimizing organic solar cells for practical applications.
文摘This study shows the unexpected and counterintuitive possibility of simultaneously orienting a molecule while delocalizing its molecular axis in a plane in field-free conditions.The corresponding quantum states are characterized,and different control strategies using shaped terahertz(THz)laser pulses are proposed to reach such states at zero and nonzero temperatures.The robustness against temperature effects of a simple control procedure combining a laser and a THz pulse is shown.Such control strategies can be applied not only to linear molecules but also to symmetric top molecules.
基金partly supported by the grants(51973027 and 52003044)from the National Natural Science Foundation of Chinathe Fundamental Research Funds for the Central Universities(2232020A-08)+5 种基金International Cooperation Fund of Science and Technology Commission of Shanghai Municipality(21130750100)Major Scientific and Technological Innovation Projects of Shandong Province(2021CXGC011004)supported by the Chang Jiang Scholars Programthe Innovation Program of Shanghai Municipal Education Commission(2019-01-07-00-03-E00023)to Prof.Xiaohong QinYoung Elite Scientists Sponsorship Program by China Association for Science and Technology,State Key Laboratory for Modification of Chemical Fibers and Polymer Materials(KF2216)Donghua University Distinguished Young Professor Program to Prof.Liming Wang。
文摘The degree of polymer chain orientation is a key structural parameter that determines the mechanical and physical properties of fibers.However,understanding and significantly tuning the orientation of fiber macromolecular chains remain elusive.Herein,we propose a novel electrospinning technique that can efficiently modulate molecular chain orientation by controlling the electric field.In contrast to the typical electrospinning method,this technique can piecewise control the electric field by applying high voltage to the metal ring instead of the needle.Benefiting from this change,a new electric field distribution can be realized,leading to a non-monotonic change in the drafting force.As a result,the macromolecular chain orientation of polyethylene oxide(PEO)nanofibers was significantly improved with a recordhigh infrared dichroic ratio.This was further confirmed by the sharp decrease in the PEO jet fineness of approximately 80%and the nanofiber diameter from 298 to 114 nm.Interestingly,the crystallinity can also be adjusted,with an obvious drop from 74.9%to 31.7%,which is different from the high crystallinity caused by oriented chains in common materials.This work guides a new perspective for the preparation of advanced electrospun nanofibers with optimal orientation–crystallinity properties,a merited feature for various applications.
基金V. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.10434100） and the Knowledge Innovation Project of Chinese Academy of Sciences.
文摘Based on the reaction microscope at the institute of modern physics, the reaction mechanism in molecular ion-atom collisions is investigated experimentally. The features of this system is illustrated by a kinematically complete experhnent performed for the collision process. Using the so-called list-mode data recording technique and the coincidence measurement, the momentum vector of each fragment from the molecular ion were recorded event by event. The orientation of the molecular axis for H2^＋ dissociation reactions could be determined for each event in the off-line analysis. The measured orientation of the molecular ion is believed the same as the one at the instance of collision under axial recoil approximation. The polar angle resolution of the molecular orientation of ±8° was obtained.
文摘As dipyranylidenes are excellent hole carriers, applications in organic solar cells or organic light emitting diode are envisaged. In the present study, we investigate the morphology of 2,2＇,6,6＇-tetraphenyl-4,4＇-dipyranylidene （DIPO-Ph4） deposited under vacuum on a silicon nitride （Si3N4） substrate, a paradigmatic system for the study of molecular crystal/inorganic substrate interfaces. Samples with various coating ratios and different thermal treatments were prepared. The films were characterized by atomic force microscopy and scanning transmission X-ray microscopy to gain insight into material growth. The results show a change in orientation at a molecular level depending upon the evaporation conditions. We are now able to tailor an organic layer with a specific molecular orientation and a specific electronic behavior.
基金financially supported from National Key R&D Program of China(2016YFA0200700)the National Natural Science Foundation of China(22071207,21721001,21805230,51873217,21734008,51773047,52073068)。
文摘A bulk heterojunction in organic solar cells is where charge separation and recombination occur.Molecular orientation at the interface is one of the key factors that dictate solar cell efficiency.Although X-ray scattering-based methods can determine donor/acceptor domain orientations between an anisotropic phase and an isotropic fullerene-based phase,the rise of nonfullerene solar cells presents a new challenge in delineating local molecular directions at the interface between two anisotropic donor/acceptor domains.Here,we determine interfacial molecular orientations of three high-efficiency small molecule solar cells(ZR1:Y6,B1:BO-4 Cl,and BTR:BO-4 Cl)using polarization-selective transient absorption spectroscopy.The polarization anisotropy of charge separation dynamics indicates an angle of~90°between ZR1 and Y6 molecules at the interface,an angle close to 0°between B1 and BO-4 Cl,and random orientations between BTR and BO-4 Cl.These observations provide complementary information to X-ray scattering measurements and highlight polarization-selective transient absorption spectroscopy as a tool to probe interfacial structure and dynamics of key photophysical steps in energy conversion.
基金supported by the National Natural Science Foundation of China(No.11372032)The Open Project of Key Laboratory of Computational Physics in China
文摘Molecular dynamics simulation is employed to study the tension and compression deformation behaviors of magnesium single crystals with different orientations.The angle between the loading axis and the basal direction ranges from 0° to 90°.The simulation results show that the initial defects usually nucleate at free surfaces,but the initial plastic deformation and the subsequent microstructural evolutions are various due to different loading directions.The tension simulations exhibit the deformation mechanisms of twinning,slip,crystallographic reorientation and basal/prismatic transformation.The twinning,crystallographic reorientation and basal/prismatic transformation can only appear in the crystal model loaded along or near the a-axis or c-axis.For the compression simulations,the basal,prismatic and pyramidal slips are responsible for the initial plasticity,and no twinning is observed.Moreover,the plastic deformation models affect the yield strengths for the samples with different orientations.The maximum yield stresses for the samples loaded along the c-axis or a-axis are much higher than those loaded in other directions.
基金V. ACKNOWLEDGMENTS We thank Professor Shi-he Yang from the Hong Kong University of Science and Technology for supplying Dy@Cs2. This work is supported by the National Natural Science Foundation of China （No.10825415）.
文摘The adsorption and molecular orientation of Dy@Cs2 isomer I on Au（111） has been investigated using ultrahigh-vacuum scanning tunneling microscopy at 80 K. At low coverages, the Dy@Cs2 molecules tend to grow along the step edges of Au（111）, forming small clusters and molecular chains. Adsorption of Dy@Cs2 on the edges is dominated by the fullerene-substrate interaction and presents various molecular orientations. At higher coverages, the Dy@Cs2 is found to form ordered islands consisting of small domains of equally oriented molecules. The Dy@Cs2 molecules in the islands prefer the adsorption configurations with the major C2 axis being approximately parallel to the surface of the substrate. Three preferable orientations of the Dy@Cs2 molecules are found in a two-dimensional hexagonal close packed overlayer. These observations are attributed to the interplay of the fullerene-substrate interaction and dipole-dipole interaction between the metallofullerenes.
基金funded by the Industry Project of Ministry of Agriculture of China(200903051)the National Natural Science Foundation of China(30900149)
文摘In insects,the sense of smell is mainly mediated by olfactory receptors（Ors）.Olfactory co-receptor（Orco）,which is coexpressed with the Ors in almost all olfactory receptor neurons（ORNs）,is demonstrated to be an essential component in the insect olfactory system.It can be potential target for developing novel olfactory-disruption strategy to control insect pests.In this study,two full-length cDNA sequences encoding Orcos（CmedOrco and ChsupOrco） were cloned from two Lepidopteran rice pests,the rice leaffolder,Cnaphalocrocis medinalis and the rice striped stem borer,Chilo suppressalis.The amino acid sequences of CmedOrco and ChsupOrco showed high similarity to the previously identified Orcos from other insect species. Bioinformatic prediction and cellular immunofluorescence indicated that CmedOrco and ChsupOrco were both seven-transmembrane proteins with intracellular N-termini and extracellular C-termini.mRNA expression levels of the two Orcos were much higher in male and female antennae than those in non-olfactory tissues,and the ChsupOrco transcripts reached a peak level in adults compared to other life stages.Our results provide a foundation from which it will be possible to elucidate the roles of Orco in moth olfaction and for the development of environment-friendly management strategies of these two rice insect pests.
基金supports by the Grant-in-Aid of Scientific Research of Challenging Research(Exploratory)(JP23K17738)to TS from MEXT of Japanthe 41st grant of research from Nippon Sheet Glass Foundation for Materials Science and Engineering to TS.
文摘A redox-active monolayer on an optically transparent electrode constitutes a typical platform for spectroelectrochemical sensing.The necessity for its sophistication arises from the availability of multi-dimensional sensing signals.Simultaneous monitoring of the redox current and color change synchronized with the oxidation state change significantly enhances sen-sitivity and selectivity.This study aimed to elucidate the modification of an indium tin oxide(ITO)electrode with a viologen monolayer with an ordered orientation.Novel methods were developed to immobilize a viologen molecule bearing a car-boxyl group to form assembled monolayers through a condensation reaction using 1-ethyl-3-(3-dimethylaminopropyl)-car-bodiimide with N-hydroxy-succinimide(EDC/NHS).In the two methods of immobilization,one utilizes a two-step process to firstly form an aromatic siloxane base layer and subsequently attach the viologen derivative through an amide linkage by post-amidation.The other employs a direct ester linkage between the hydroxyl groups of the ITO surface and the car-boxyl group of the viologen derivative.The latter method was also applied to immobilize a ferrocenyl group at a very short distance from the ITO surface.Potential-modulated UV-visible transmission absorption spectral measurement techniques with oblique incidence of plane-polarized light were employed to determine the orientation of the longitudinal axis of the reduced form of the viologen.The frequency dependence data of the potential-modulated transmission absorption signals were utilized to analyze the electron transfer kinetics.The performance of the two viologen-modified electrodes was com-pared to that of an ITO modified by post-amidation to the most commonly used base layer prepared with 3-aminopropyl triethoxysilane.
基金support from the Songshan Lake Mate-rials Laboratory(2021SLABFK03)This work is supported by the National Natural Science Foundation of China(52173172,52173171,and 21801124)+4 种基金the Natural Science Foundation for Distinguished Young Scholars of Guangdong Province(2021B1515020027)the Guangdong Basic and Applied Basic Research Foundation(2021A1515110892)the China Postdoctoral Science Foundation(2021M700062)the Shenzhen Science and Technology Innovation Commission JCYJ202103243104813035 and JCYJ20180504165709042)the Open Fund of the State Key Laboratory of Luminescent Materials and Devices(South China University of Technology).
文摘Bithiophene imide (BTI)-based polymers have been promising photovoltaic materials due to their high mobility and tunable energy levels. However, BTI polymers have rarely been revisited since organic solar cells (OSCs) entered the era of non-fullerene electron acceptors (NFEA) likely owing to their incompatibility with NFEAs. Herein, fine-tuning the aggregation and orientation of BTI-based donor-π-acceptor (D-π-A) polymer donors was achieved by incorporating the linear n-octyl group into thiophene π-bridge. The resulting polymer donor G15 shows excellent compatibility with NFEA L15 (polymer acceptor). The G15-based all-polymer OSCs achieve high power conversion efficiency of 15.17%. This is significantly higher than that (< 5%) of its analogue with isomerized branched alkyl chains and also among the highest values for all-polymer OSCs. The results highlight that well-tailored BTI polymer donors are attractive photovoltaic materials for further exploration in non-fullerene organic solar cells.
基金National Key Research and Development Program,Grant/Award Number:2019YFA0705900National Natural Science Foundation of China,Grant/Award Numbers:22275058,U20A6002,22109046+1 种基金Guangdong Basic and Applied Basic Research Foundation,Grant/Award Numbers:2022B1515120008,2022A1515011417Guangdong Innovative and Entrepreneurial Research Team Program,Grant/Award Number:2019ZT08L075。
文摘Nonfused ring electron acceptors(NFREAs)are promising candidates for future commercialization of organic solar cells(OSCs)due to their simple synthesis.Still,the power conversion efficiencies(PCEs)of NFREA-based OSCs have large room for improvement.In this work,by merging end group halogenation and side chain engineering,we developed four A-D-A’-D-A type NFREAs,which we refer to as EH-4F,C4-4F,EH-4Cl,and C4-4Cl.Single crystal X-ray diffraction revealed that multiple intermolecular S⋅⋅⋅F interactions between cyclopentadithiophene and 5,6-difluoro-3-(dicyanomethylene)indanone could cause an unfavorable dimer formation,leading to ineffectiveπ-πstackings in EH-4F and C4-4F,whereas no such dimer was found in EH-4Cl and C4-4Cl after replacing with 5,6-dichloro-3-(dicyanomethylene)indanone.Moreover,although the shorter n-butyl side chain resulted in a closer molecular packing in C4-4Cl,EH-4Cl(2-ethylhexyl substitution)with proper crystallinity exhibited enhanced face-on orientation in thin film,which is favorable for vertical charge transport and further reducing charge recombination.As a result,a PCE of 13.0%is obtained for EH-4Cl-based OSC with a fill factor of 0.70.This work highlights the importance of molecular packing and orientation control toward future high-performance A-D-A’-D-A type NFREAs.
