Dipole Moment Research Articles

Controlled interlayer exciton ionization in an electrostatic trap in atomically thin heterostructures

Atomically thin semiconductor heterostructures provide a two-dimensional (2D) device platform for creating high densities of cold, controllable excitons. Interlayer excitons (IEs), bound electrons and holes localized to separate 2D quantum well layers, have permanent out-of-plane dipole moments and long lifetimes, allowing their spatial distribution to be tuned on demand. Here, we employ electrostatic gates to trap IEs and control their density. By electrically modulating the IE Stark shift, electron-hole pair concentrations above 2 × 1012 cm−2 can be achieved. At this high IE density, we observe an exponentially increasing linewidth broadening indicative of an IE ionization transition, independent of the trap depth. This runaway threshold remains constant at low temperatures, but increases above 20 K, consistent with the quantum dissociation of a degenerate IE gas. Our demonstration of the IE ionization in a tunable electrostatic trap represents an important step towards the realization of dipolar exciton condensates in solid-state optoelectronic devices.

Coordination Desymmetrization of Copper Single-Atom Catalyst for Efficient Nitrate Reduction.

Coordination engineering strategy for optimizing the catalytic performance of single-atom catalysts (SACs) has been rapidly developed over the last decade. However, previous reports on copper SACs for nitrate reduction reactions (NO3RR) have mostly focused on symmetric coordination configurations such as Cu-N4 and Cu-N3. In addition, the mechanism in terms of the regulation of coordination environment and catalytic properties of SACs has not been well demonstrated. Herein, we disrupted the local symmetric structure of copper atoms by introducing unsaturated heteroatomic coordination of Cu-O and Cu-N to achieve the coordination desymmetrization of Cu-N1O2 SACs. The Cu-N1O2 SACs exhibit an efficient nitrate-to-ammonia conversion with a high FE of ~96.5 % and a yield rate of 3120 μg NH3 h-1 cm-2 at -0.60 V vs RHE. As indicated by in situ Raman spectra, the catalysts facilitate the accumulation of NO3 - and the selective adsorption of *NO2, which were further confirmed by the theoretical study of surface dipole moment and orbital hybridization. Our work illustrated the correlation between the coordination desymmetrization and the catalytic performance of copper SACs for NO3RR.

Accelerated Electron-Hole Separation at the Organic-Inorganic Anthracene/Janus MoSSe Interface.

Organic light-absorbing materials with two-dimensional semiconductor layers as contact electrodes are promising for efficient and flexible low-cost solar cells. Considering anthracene as an absorber and a MoSSe Janus monolayer, we use non-adiabatic molecular dynamics to show that electron transfer from anthracene to MoSSe is faster on the Se side than the S side. The transfer from anthracene to MoS2 and MoSe2 monolayers takes intermediate times. As a rule, we find that a shorter adsorption distance produces a stronger donor-acceptor coupling. The smaller distance on the Se side is rationalized by the attractive force between the intrinsic dipole moment of the Janus structure and that of the molecule induced due to adsorption. Quantum coherence also affects the transfer time. The study provides detailed insights into adsorption of molecules on Janus structures and the resulting electronic and electron vibrational interactions. The results suggest that the dipole interaction plays an important role in the thermodynamic stability, alignment of electronic levels, and electron vibrational dynamics.

Analysis of the nonlinear optical properties, vibrational spectra, DFT method and photovoltaic performance of cyanidin-3-rutinoside chloride

This study aims to identify a cyanidin-3-rutinoside chloride that exhibits both photovoltaic performance and nonlinear optical properties, which may be utilized in the field of optoelectronics. Prior to investigating these properties, the stable structure must be determined. For this purpose, its conformational analysis is performed by the Molecular Force Field method with the spartan program. The exact nature of the stable configuration has been ascertained by empirical evidence. The energy of the stable configuration is -1654184.76 kcal/mol, and its dipole moment is 9.94 Debye. Cyanidin-3-rutinoside chloride has been investigated using experimental FT-IR and Raman spectroscopies. Meanwhile, the DFT method at the B3LYP/6-311 + + G(d, p) level was employed in order to study the simulated FT-IR and Raman spectra, the HOMO-LUMO analysis, the molecular electrostatic potentials (MEP), and the non-linear optical (NLO) characteristics of the title molecule. The HOMO and LUMO energies are − 6.45 and − 3.64 electron volts (eV), respectively, with a gap value of 2.81 eV. Additionally, the title compound’s open-circuit voltage, the transition density matrix light-harvesting efficiency, driving force, and binding energy were calculated with by taking photovoltaic cell properties into account. Furthermore, investigations of hole reorganization energy, electron reorganization energy, and total reorganization energy were carried out at the B3LYP/6-31G(d, p) level for the cyanidin-3-rutinoside chloride of interest. In addition, density of state calculations and NBO were made at the B3LYP/6-31G(d, p) level. We calculated the following values for LHE, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{V}_{oc}$$\\end{document}, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{{\\Delta\\:}\ ext{G}}_{\ ext{i}\ ext{n}\ ext{j}\ ext{e}\ ext{c}\ ext{t}}$$\\end{document}, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{E}_{b}$$\\end{document}, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\\lambda\\:}_{h}$$\\end{document}, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\\lambda\\:}_{e}$$\\end{document} and \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\\lambda\\:}_{total}$$\\end{document} : 0.06, 2.45 eV, 0.20 eV, 0.56 eV, 0.50 eV, 0.57 eV and 1.06 eV, respectively.

Thionation‐Induced Enhancement of Optical and Electronic Properties in NDI Molecule for Molecular Electronic Applications: A Computational Study Using DFT/TD‐DFT and QTAIM Theory

AbstractThe study investigates the impact of thionation on N,N'‐di(dodecyl)‐4,5,8,9‐naphthalene diimide (NDI) through computational methods such as density functional theory (DFT/TD‐DFT), quantum theory of atoms in molecules (QTAIM), and Landauer theory (LT). Thionation, involving the replacement of diamide oxygens with sulfurs in NDI, significantly enhances quantum‐electronic/thermoelectric properties. Computational analyzes of energy of frontier orbitals HOMO/LUMO, dipole moment, polarizability, first superpolarizability, UV spectrum, and cohesive energy show the superior performance of the thione structure (M2) compared to the pristine structure (M1). Thionation decreased the energy gap from 01.3 eV (in M1 structure) to 1.87 eV (in M2 structure). The absorption wavelength in the pristine structure (M1) is calculated to be 507 nm, which increased to 1067 nm after thionation (M2). Cohesive energy values for each of M1 and M2 structures are calculated as 12.76 and 12.89 Kcal mol−1, respectively, which indicates the improvement of stability after thionation. After connecting M1 and M2 to gold electrodes (Au‐M1‐Au and Au‐M2‐Au) and applying electric fields, the Au‐M2‐Au structure shows a lower energy gap, lower thermoelectric activity and higher conductivity at field intensities with higher than 140 × 10−4 (a.u.), indicating its use as a field‐effect molecular device (such as molecular wire or molecular switch).

Space and laboratory discovery of iminopentadienylidene, HNC5

We report the discovery of HNC$_5$ in TMC-1. Six lines have been found in harmonic relation, with quantum numbers $J$=12-11 up to $J$=17-16. The lines can be reproduced with the standard frequency relation for linear molecules with $B$=1361.75034pm 0.00033 MHz and $D$=32.2pm 0.7 Hz. The assignment of the carrier to iminopentadienylidene was achieved through examining the possible candidates at a high level of theoretical ab initio calculations. Motivated by the good agreement between the observed $B$ and the calculated value for HNC$_5$, we searched for it in the laboratory and observed the transitions $J$=5-4 to 7-6. The derived rotational and distortion constants are 1361.74998pm 0.00040 MHz and 26.5pm 5.5 Hz, respectively. Hence, we solidly conclude that the carrier of the lines found in TMC-1 is HNC$_5$. The calculated dipole moment for this species is 7.7\,D and the derived column density is (1.3pm 0.2)times 1010 $. We used the new QUIJOTE data to improve previous observations of HC$_4$NC and found that the abundance ratio HC$_4$NC/HNC$_5$ is 10pm 2. The abundance ratio of HC$_5$N and its two isomers HC$_4$NC and HNC$_5$ is 500pm 80 and 5100pm 800, respectively. These abundance ratios are higher by a factor of sim 10 than those of the equivalent isomers of HC$_3$N. Chemical models reproduce the observed abundances reasonably well when a chemistry similar to that of the smaller species C$_3$HN isomers is adopted. The formation of HNC$_5$ and HC$_4$NC arises from the dissociative recombination with electrons of the cations HC$_5$NH$^+$ and HC$_4$NCH$^+$.

Achieving 19.4% Efficiency Polymer Solar Cells by Reducing Backbone Disorder in Donor Terpolymers

AbstractThe ternary copolymerization strategy has emerged as a promising strategy for developing high‐efficiency donor polymers in polymer solar cells (PSCs). Terpolymers based on the star polymer PM6 have already realized good photovoltaic performance. However, challenges such as the intricate synthesis of fluorine‐substituted benzodithiophene (F‐BDT) unit of PM6 and entropy increase induced by backbone disorder have hindered the construction of high‐performance donor terpolymers. In this work, these challenges are addressed by opting for the cost‐effective chlorinated‐substituted benzodithiophene unit (Cl‐BDT) as an alternative to F‐BDT and incorporating the large dipole moment and electron‐deficient TPD group as the third component into the high‐performance donor polymer of PM7. As expected, this approach effectively suppresses terpolymer backbone disorder while enhancing crystallinity, thereby optimizing morphology and improving charge generation and transport. Remarkably, the PM7‐TPD‐10‐based device with 10% TPD replacement achieves a champion power conversion efficiency (PCE) of 18.26%. After introducing PM7‐TPD‐10 as the third component into D18:L8‐BO blend, a dual mechanism for improving the efficiency to 19.40% is realized. This work demonstrates that the high dipole moiety as the third component to construct terpolymers is an important strategy to suppress the backbone disorder and increase the crystallinity, facilitating the optimization of morphology and device performance.

Photophysics in Biomembranes: Computational Insight into the Interaction between Lipid Bilayers and Chromophores.

ConspectusLight is ubiquitously available to probe the structure and dynamics of biomolecules and biological tissues. Generally, this cannot be done directly with visible light, because of the absence of absorption by those biomolecules. This problem can be overcome by incorporating organic molecules (chromophores) that show an optical response in the vicinity of those biomolecules. Since those optical properties are strongly dependent on the chromophore's environment, time-resolved spectroscopic studies can provide a wealth of information on biosystems at the molecular scale in a nondestructive way. In this work, we give an overview on the multiscale computational strategy developed by us in the last eight years and prove that theoretical studies and simulations are needed to explain, guide, and predict observations in fluorescence experiments. As we challenge the accepted views on existing probes, we discover unexplored abilities that can discriminate surrounding lipid bilayers and their temperature-dependent as well as solvent-dependent properties. We focus on three archetypal chromophores: diphenylhexatriene (DPH), Laurdan, and azobenzene. Our method shows that conformational changes should not be neglected for the prototype rod-shaped molecule DPH. They determine its position and orientation in a liquid-ordered (Lo) sphingomyelin/cholesterol (SM/Chol) bilayer and are responsible for a strong differentiation of its absorption spectra and fluorescence decay times in dioleoylphosphatidylcholine (DOPC) and dipalmitoylphosphatidylcholine (DPPC) membranes, which are at room temperature in liquid-disordered (Ld) and solid-gel (So) phases, respectively. Thanks to its pronounced first excited state dipole moment, Laurdan has long been known as a solvatochromic probe. Since this molecule has however two conformers, we prove that they exhibit different properties in different lipid membrane phases. We see that the two conformers are only blocked in one phase but not in another. Supported by fluorescence anisotropy decay simulations, Laurdan can therefore be regarded as a molecular rotor. Finally, the conformational versatility of azobenzene in saturated Ld lipid bilayers is simulated, along with its photoisomerization pathways. By means of nonadiabatic QM/MM surface hopping analyses (QM/MM-SH), a dual mechanism is found with a torsional mechanism and a slow conversion for trans-to-cis. For cis-to-trans, simulations show a much higher quantum yield and a so-called "pedal-like" mechanism. The differences are related to the different potential energy surfaces as well as the interactions with the surrounding alkyl chains. When tails of increased length are attached to this probe, cis is pushed toward the polar surface, while trans is pulled toward the center of the membrane.

Intrinsic Out-Of-Plane and In-Plane Ferroelectricity in 2D AgCrS2 with High Curie Temperature.

2D ferroelectric materials have attracted extensive research interest due to potential applications in nonvolatile memory, nanoelectronics and optoelectronics. However, the available 2D ferroelectric materials are scarce and most of them are limited by the uncontrollable preparation. Herein, a novel 2D ferroelectric material AgCrS2 is reported that are controllably synthesized in large-scale via salt-assist chemical vapor deposition growth. By tuning the growth temperature from 800 to 900°C, the thickness of AgCrS2 nanosheets can be precisely modulated from 2.1 to 40nm. Structural and nonlinear optical characterizations demonstrate that AgCrS2 nanosheet crystallizes in a non-centrosymmetric structure with high crystallinity and remarkable air stability. As a result, AgCrS2 of various thicknesses display robust ferroelectric polarization in both in-plane (IP) and out-of-plane (OOP)directions with strong intercorrelation and high ferroelectric phase transition temperature (682 K). Theoretical calculations suggest that the ferroelectricity in AgCrS2 originates from the displacement of Ag atoms in AgS4 tetrahedrons, which changes the dipole moment alignment. Moreover, ferroelectric switching is demonstrated in both lateral and vertical AgCrS2 devices, which exhibit exotic nonvolatile memory behavior with distinct high and low resistance states. This study expands the scope of 2D ferroelectric materials and facilitates the ferroelectric-based nonvolatile memory applications.

Complex conductivity as a tool to investigate the electrical behavior between graphene oxide and reduced graphene in supercapacitors: Correlation between the electrical properties

The storage mechanisms of solid-solid supercapacitors based on graphene oxide (rGO/GO/rGO) were explored by Zhang Q et al. (Zhang et al., 2014) [1], using Density Functional Theory (DFT) and Impedance Spectroscopy (EIS) to elucidate the unusual capacitive behavior of GO sandwich films. Their study revealed alternating charged layers without diffusion zones. Analysis of complex impedance (Z*) data, ranging from 10−3 to 3.106 Hz, was conducted using an equivalent circuit, though this was limited to Nyquist plot data.To further investigate charge storage mechanisms, the current study delved deeper into complex impedance (Z*) and conductivity (σ*). A theoretical approach identified relaxation processes in the imaginary parts of (Z″) and (σ'') across frequencies. Extrapolation up to 3.10^9 Hz and deconvolution confirmed three distinct relaxation processes in Z* and σ*, similar to Cole-Cole relaxation, which describes Maxwell-Wagner-Sillars (MWS) relaxation. This reflects local electrical interactions between active sites on molecular chains and counterions, creating induced dipolar moments or diffusion processes.The identified relaxations at low, medium, and high frequencies correspond well with DFT results, attributed to specific regions: graphene oxide (GO), the (rGO/GO) interface, and reduced graphene (rGO). Key parameters extracted from each relaxation, such as relaxation time, ionic strength, and conductivity values at different frequencies, showed good correlation. This approach, based on deep conductivity (σ*) analysis, effectively highlighted the charge conduction and storage mechanisms in rGO/GO/rGO supercapacitor films.

Harnessing Polar Interactions Tunes the Stability of Ultrathin Polymer Solution Films.

The stability of ultrathin (<100 nm) polymer films is essential in applications like protective coatings. On the contrary, their instability may actually be desirable for the emergence of self-assembled nanoscale patterns utilized in the fabrication of functional devices. Polymer solution films exhibit two distinct kinds of instabilities, viz., dewetting (long-wave) and decomposition (short-wave). Dewetting refers to the rupture of the continuous film to form isolated domains, while decomposition leads to phase separation within the polymer solution. The focus of this work is on leveraging polar interactions between the solute and solvent molecules to tune the stability of the film. A gradient dynamics-based thin film model is developed to investigate pattern formation in a thin polar polymer solution film. The Flory-Huggins theory is suitably modified by introducing a polar interaction parameter that depends upon the concentration of the polymer and the dipole moments of monomer (μ1) and solvent molecules (μ0). A linear stability analysis is performed to determine the characteristic length scale and growth rate of the instabilities. It is shown that the range of concentration space for the occurrence of the decomposition mode is directly affected by the Flory interaction parameter (χ0), μ0, and μ1, thereby serving as control parameters to tune the width of the concentration range. It is further shown that ignoring polar interactions may lead to incorrect predictions of the instability mode, including a complete loss of the decomposition mode. In addition, the long-wave dewetting length scale is found to decrease due to bulk dipolar interactions at higher polymer concentrations. Finally, numerical simulations are carried out to track the nonlinear evolution of the interface and concentration field for both the decomposition and dewetting modes of instability.

Interaction of light with subwavelength particles: Revealing the physics of electric dipole moment in the classical scattering problem

Interaction of light with subwavelength particles: Revealing the physics of electric dipole moment in the classical scattering problem

Near-field induced local excitation dynamics of Na10 and Na10-N2 from real-time TDDFT.

Electron dynamics of the Na10 chain and the Na10-N2 complex locally excited by an atomistic optical near-field are investigated using real-time time-dependent density functional theory calculations on real-space grids. Ultrafast laser pulses were used to simulate the near-field excitation under on- and off-resonance conditions. Off-resonance excitation did not lead to the propagation of the excitation through the Na10 chain. In contrast, under the resonance conditions, the excited state is delocalized over the entire Na chain. Analysis of the local dipole moment of each atom in Na10 indicates that this behavior is consistent with the transition density. Adding an N2 molecule to the opposite end of the local excitation region results in energy transfer via the Na10 chain. The energy transfer efficiency of the N2 molecule is well correlated with the absorption spectrum of Na10. The present study paves the way for realizing remote excitation and photonic devices at the atomic scale.

Emergent Ferroelectric Nematic and Heliconical Ferroelectric Nematic States in an Achiral "Straight" Polar Rod Mesogen.

Ferroelectric nematic liquid crystals (NFLCs) are distinguished by their remarkable polarization characteristics and diverse physical phenomena, sparking significant interest and excitement within the scientific community. To date, over 150 NFLC molecules are developed; however, there are no reports regarding straight linear polar molecules with a parallel alignment of the permanent dipole moment and the molecular axis. The straight polar mesogen nBOE exhibits an enantiotropic NF phase with a wide temperature window (up to 100 K) despite having a longer alkyl chain (up to n = 6) than the critical alkyl chain length of conventional models. Interestingly, nBOE with a medium-length alkyl chain displays an exotic phase sequence of NF-HCNF-SmXF during the elimination of positional displacement among adjacent molecules. Furthermore, the reflective color modulation of the HCNFLC over the entire VIS-NIR spectral regime by ultralow E-field (up to 0.14V µm-1) is demonstrated.

Probing charge redistribution at the interface of self-assembled cyclo-P5 pentamers on Ag(111)

Phosphorus pentamers (cyclo-P5) are unstable in nature but can be synthesized at the Ag(111) surface. Unlike monolayer black phosphorous, little is known about their electronic properties when in contact with metal electrodes, although this is crucial for future applications. Here, we characterize the atomic structure of cyclo-P5 assembled on Ag(111) using atomic force microscopy with functionalized tips and density functional theory. Combining force and tunneling spectroscopy, we find that a strong charge transfer induces an inward dipole moment at the cyclo-P5/Ag interface as well as the formation of an interface state. We probe the image potential states by field-effect resonant tunneling and quantify the increase of the local change of work function of 0.46 eV at the cyclo-P5 assembly. Our experimental approach suggest that the cyclo-P5/Ag interface has the characteristic ingredients of a p-type semiconductor-metal Schottky junction with potential applications in field-effect transistors, diodes, or solar cells.

Screening and Antiscreening Effects in Endohedral Nanotubes.

Recently we investigated from first-principles screening properties in systems where small molecules, characterized by a finite electronic dipole moment, are encapsulated in different nanocages. The most relevant result was the observation of an antiscreening effect in alkali-halide nanocages characterized by ionic bonds: in fact, due to the relative displacement of positive and negative ions, induced by the dipole moment of the encapsulated molecule, these cages act as dipole-field amplifiers, different from what is observed in carbon fullerene nanocages, which exhibit instead a pronounced screening effect. Here we extend the study to another class of nanostructures: the nanotubes. Using first-principles techniques based on density functional theory, we studied the properties of endohedral nanotubes obtained by encapsulation of a water molecule or a linear HF molecule. A detailed analysis of the effective dipole moment of the complexes and of the electronic charge distribution suggests that screening effects crucially depend not only on the nature of the intramolecular bonds but also on the size and the shape of the nanotubes and on the specific encapsulated molecule. As observed in endohedral nanocages, screening is maximum in covalent-bond carbon nanotubes, while it is reduced in partially ionic nanotubes, and an antiscreening effect is observed in some ionic nanotubes. However, in this case, the scenario is more complex than in corresponding ionic nanocages. In fact the specific geometric structure of alkali-halide nanotubes turns out to be crucial for determining the screening/antiscreening behavior: while nanotubes with octagonal transversal section can exhibit an antiscreening effect, which quantitatively depends on the number of layers in the longitudinal direction, instead nanotubes with dodecagonal section are always characterized by a reduction of the total dipole moment so that a screening behavior is observed. Our results show that, even in nanotube structures, in principle one can tune the dipole moment and generate electrostatic fields at the nanoscale without the aid of external potentials.

Do Molecular Geometries Change Under Vibrational Strong Coupling?

As pioneering experiments have shown, strong coupling between molecular vibrations and light modes in an optical cavity can significantly alter molecular properties and even affect chemical reactivity. However, the current theoretical description is limited and far from complete. To explore the origin of this exciting observation, we investigate how the molecular structure changes under strong light-matter coupling using an ab initio method based on the cavity Born-Oppenheimer Hartree-Fock ansatz. By optimizing H2O and H2O2 resonantly coupled to cavity modes, we study the importance of reorientation and geometric relaxation. In addition, we show that the inclusion of one or two cavity modes can change the observed results. On the basis of our findings, we derive a simple concept to estimate the effect of the cavity interaction on the molecular geometry using the molecular polarizability and the dipole moments.

Asymmetric dumbbell dimers simultaneously supporting quasi-bound states in continuum and anapole modes for terahertz biosensing

Abstract Multi-resonant metasurfaces are of great significance in the applications of multi-band nanophotonics. Here, we propose a novel metasurface design scheme for simultaneously supporting quasi-bound states in continuum (QBIC) and other resonant modes, in which QBIC resonance is generated by mirror or rotational symmetry breaking in oligomers while other resonant modes can be simultaneously excited by rationally designing the shapes of meta-atoms within oligomers. As an example, the simultaneous excitation of QBIC and anapole modes are demonstrated in a dimer metasurface composed of asymmetric dumbbell-shaped apertures. Based on the far-field multipole decomposition and near-field electromagnetic field distributions, the origin mechanisms of QBIC and anapole mode are elucidated. The symmetry breaking of dumbbell-shaped dimer results in QBIC. Within a certain asymmetric variation range, the contributions of toroidal dipole moment and electric dipole moment with approximately equal magnitudes remain dominant, which allows the anapole mode to always present. The effectiveness of the proposed design scheme is further confirmed by the experimental results identical with the evolutions of numerical simulation. In terahertz biosensing experiments, the anapole mode exhibits a higher sensitivity of 271.3 GHz (nmol/μl)−1, whereas the QBIC can achieve a lower detection limit of 0.015 nmol/μl and expands the detection range by almost an order of magnitude. Our findings are beneficial to designing multi-resonant metasurfaces with different resonance modes and promote the corresponding applications in the fields of biosensing, lasers, filtering, and nonlinearity.

In Quest of the Missing C2H6O2 Isomers in the Interstellar Medium: A Theoretical Search.

Ethylene glycol (C2H6O2), the only diol detected in the interstellar medium (ISM), is a key component in the synthesis of prebiotic sugars. Its structural isomer, methoxymethanol, has also been found in the ISM. Our results show that neither ethylene glycol (ethane-1,2-diol) nor methoxymethanol is the most stable isomer. Using high-level computational methods, we identified five isomers: two diols, one hydroxy ether, and two peroxides. The geminal diol 1,1-ethanediol (ethane-1,1-diol) is the most stable isomer, although it has not been detected in the ISM, whereas the two peroxides are less stable than the geminal diol by 60 kcal/mol. This study also provides the rotational constants and dipole moment for each conformer of every C2H6O2 isomer.

Effect of methyl trifluoride substitution on colorless transparency of polyimide: A DFT/TD-DFT study

The rapid advancement of flexible electronic devices has rendered high-performance colorless transparency polyimide (PI) films essential for energy storage and devices. However, there still remains controversy regarding the charge-transfer complexes in relation to the optical properties of PIs. Herein, we employed a combination of DFT and TD-DFT methods to elucidate the hole and electron characteristics of PIs. The results revealed that the incorporation of a CF3 group significantly enhances the dipole moment. Notably, the incorporation of CF3 groups onto both the anhydride and diamine units impedes charge transfer, resulting in a reduction of the HOMO energy level and an increse of the LUMO energy. The calculation results also indicate that the introduction of CF3 groups markedly hinders charge transfer within P4 in its excited state, leading to the minimum values for three characteristic parameters (D = 2.60 Å, CT = 0.51 e, t = 0.53 Å). Therefore, P4 exhibits a shortest charge transfer pathway resulting in minimal electron transfer and obvious blue-shifted UV–vis spectra, thus contributing to its excellent colorless transparency. This work provides a theoretical foundation and guidance for targeted design and development of colorless transparent PI films.