Energy Absorption Spectra Research Articles

Preparation and Photophysical Properties of Znq2 Metallic Nanomaterials

AbstractBis(8‐hydroxyquinolates) Zinc (Znq2) can be used as a light‐emitting layer material in OLED devices to achieve its efficient electroluminescence effect. In this paper, Znq2 powder has been successfully synthesized and modified by the physical vapor deposition (PVD) method. Precursors and nano‐materials are characterized by XRD, SEM, PL, and so on. The performance of the modified material has been significantly improved. The emission intensity and absorption intensity in the deposited products increased with the increase in PVD temperature. At 453 K, luminous properties such as luminous intensity reach the optimal value including its fluorescence lifetime. Fluorescence lifetime values vary from 13 to 17 ns with the increase in temperature. The luminescence mechanism is also discussed. The energy gap and absorption spectrum of HOM‐LUMO are calculated by the DFT/UB3LYP method. The experimental values agree well with the theoretical values. The nanomaterial crystals modified by PVD technology are more orderly, impurities are reduced, and the luminous stability of the material is improved, which may be one of the reasons for the relatively slow decline in product life. The research combined with theoretical simulation is expected to be helpful to the research and promotion of such materials.

Aided design and molecular regulatory mechanism of non-fused ring acceptors in the framework of A-D1-D2-A molecular systems

Non-fused ring acceptors (NFRAs) have garnered significant attention due to their low cost, ease of synthesis, and high efficiency. Molecules with asymmetric structures can improve molecular stacking and effectively reduce non-radiative energy loss. So, the asymmetric A-D1-D2-A series NFRAs (DPCT-4F and DPCT-4Cl) were selected as the research objects, and four acceptors (DPCT-D1∼DPCT-D4) were designed using end-capped modification strategies. Theoretical simulations were conducted on the ground and excited state characteristics of DPCT series molecules, and the electron mobility of the dimers formed by these acceptors was calculated. It was found that the simulated energy levels, energy gaps, absorption spectra and open-circuit voltages of original molecules are consistent with the trends in the experiment, ensuring the accuracy of the calculation method. Moreover, the nearly equal bond lengths of the developed compounds and the original molecules at the corresponding positions indicate that end-capping modification strategies have little effect on the molecular bond lengths. However, the instability of C-C single bond results in an increased dihedral angle between dipyran and cyclopentadithiophene. Among these designed molecules, DPCT-D1 and DPCT-D2, modified with -CN/-NO2 functional groups, outperform the reference molecules regarding energy gap, molecular descriptors, absorption spectrum, and exciton binding energy. This demonstrates the superiority of functional group substitution strategies with strong electron-withdrawing ability. Introducing thiophene units enables DPCT-D4 molecule to achieve a higher open-circuit voltage, dipole moment and light capture ability. Additionally, all the designed molecules exhibit higher electron mobility than DPCT-4F. DPCT-D1 shows even higher mobility than the better-performing reference molecule DPCT-4Cl due to its greater electronic coupling strength and lower reorganization energy. Overall, most tailored molecules, particularly DPCT-D1, exhibit superior performance in most critical parameters compared to the reference molecules, demonstrating the design strategy's effectiveness and offering worthwhile theoretical instruction for developing high-performance acceptors.

Exploring the effects of mono-bromination on hole-electron transport and distribution in dibenzofuran and dibenzothiophene isomers: a first-principles study.

This study delves into hole-electron transport and distribution properties inherent in mono-brominated dibenzofuran (DBF) and dibenzothiophene (DBT) isomers. As determined by frontier molecular orbitals, all brominated structures have narrower bandgaps than their primary structures. The TD-DFT calculation showed that 2BDBT had the highest absorption wavelength of all molecules at 315.35nm. Notably, the study unveils remarkably low electron and hole reorganization energies due to bromine substitution in DBF and DBT molecules. Specifically, the 4BDBF has the lowest hole reorganization energy of all DBF configurations, 0.229eV. In addition, 3BDBF has 0.226eV less electron reorganization energy than all other molecules. Compared to DBT, 3BDBT has the lowest electron reorganization energy of 0.254eV. Overall, this research sheds significant light on the fundamental electronic and hole transport characteristics of bromine-substituted DBF and DBT isomers, highlighting their promising role in polymer design as donors/acceptors for advanced organic electronic applications. Molecular structures were optimized using Density Functional Theory (DFT) B3LYP/6-311 + + G (d, p) level of theory, and the study further elucidates these molecules' energy levels and absorption spectra through Time-Dependent Density Functional Theory TD-DFT; these calculations were performed using Gaussian 09W software package. The key parameters such as reorganization energies, Electron Localization Function map, Laplacian Bond Order, and NCI-RDG were meticulously examined for the molecules with the results of DFT calculations were analyzed and displayed by utilizing the software packages VMD 1.9.4 and Multiwfn 3.8, aiming to comprehend their charge transport and distribution properties.

Which Options Exist for NISQ-Friendly Linear Response Formulations?

Linear response (LR) theory is a powerful tool in classic quantum chemistry crucial to understanding photoinduced processes in chemistry and biology. However, performing simulations for large systems and in the case of strong electron correlation remains challenging. Quantum computers are poised to facilitate the simulation of such systems, and recently, a quantum linear response formulation (qLR) was introduced [Kumar et al., J. Chem. Theory Comput. 2023, 19, 9136-9150]. To apply qLR to near-term quantum computers beyond a minimal basis set, we here introduce a resource-efficient qLR theory, using a truncated active-space version of the multiconfigurational self-consistent field LR ansatz. Therein, we investigate eight different near-term qLR formalisms that utilize novel operator transformations that allow the qLR equations to be performed on near-term hardware. Simulating excited state potential energy curves and absorption spectra for various test cases, we identify two promising candidates, dubbed "proj LRSD" and "all-proj LRSD".

High-performance optoelectronic and thermoelectric properties of transparent conductors based on Tl2O3 under pressure

In this work, the full-potential linearized augmented plane wave method (FP- LAPW) and the modified Becke-Johnson (mBJ) functional with spin–orbit (SO) coupling are used the obtain the structural, optoelectronic and thermoelectric properties of Tl2O3 under pressure. The results show that Tl2O3, as transparent conducting oxide (TCO), is a direct bandgap semiconductor with a band gap of 1.23 eV. The band gap value and the effective mass of electrons increases by increasing pressure. Density of state spectra reveal that the nature of electrons in Tl-6s state in the bottom of conduction band, like free electrons in s state, is responsible for the conducting behavior of Tl2O3. A blue shift is observed in optical spectra such as electron energy loss and absorption spectra with an increase in pressure. Obtained dielectric constants under pressure are inversely proportional to the band gap value according to Penn model. The effects of pressure on thermometric properties are also explored. The hydrostatic pressure increases Seebeck coefficient, while it decreases thermal conductivity that is an effective way to the enhancement of the thermoelectric efficiency of TCOs. A figure of merit (ZT) of 0.98 in p-type Tl2O3 is achieved that is desirable for using in thermoelectric devices.

Designing Thiadiazoloquinoxaline-Based Conjugated Polymers for Efficient Organic Photovoltaics: A DFT/TDDFT Study.

Clean and renewable energy development is becoming frontier research for future energy resources, as renewable energy offers sustainable and environmentally friendly alternatives to non-renewable sources such as fossil fuels. Among various renewable energy sources, tremendous progress has been made in converting solar energy to electric energy by developing efficient organic photovoltaics. Organic photovoltaic materials comprising conjugated polymers (CP) with narrow optical energy gaps are promising candidates for developing sustainable sources due to their potentially lower manufacturing costs. Organic semiconductor materials with a high electron affinity are required for many optoelectronic applications. We have designed a series of organic semiconductors comprised of cyclopentadithiophene as a donor and thiadiazoloquinoxaline (TQ) as an acceptor, varying the π-conjugation and TQ-derivatives. We have employed density functional theory (DFT) and time-dependent DFT (TDDFT) to evaluate the designed CP's optoelectronic properties, such as optical energy gap, dipole moment, and absorption spectra. Our DFT/TDDFT result shows that the energy gap of CPs is lowered and redshifted in the absorption spectra if there is no insertion of conjugation units such as thiophene and selenophene between donor and acceptor. In addition, selenophene shows relatively better redshift behavior compared to thiophene. Our work also provides rational insight into designing donor/acceptor-based CPs for organic solar cells.

Geometry optimization and UV/Vis spectra of organometallic chalcones functionalized with a benzo‐15‐crown‐5 fragment: A DFT/TD-DFT investigation

In this paper, we studied the structural and UV–visible absorption spectrum of the organometallic chalcones from ferrocene and cyrhetrene functionalized with a benzo‐15‐crown‐5 fragment. The influence of different alkali and alkaline earth metal ions on geometric structures, frontier molecular orbitals character, gap energy and electronic absorption spectra of [(η5-C5H4C(O)CH = CH-4-benzo-15-crown5)MLn] (MLn = Fe(η5-C5H5) and Re(CO)3) has been theoretically studied by density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations with PBE0 and CAM-B3LYP hybrid functionals. Calculated geometric parameters of studied complexes are in good agreement with the available experimental values. The theoretical absorption spectra reproduce the main properties of the experimental spectra. Both alkali (Li+, Na+, K+, Rb+ and Cs+) and alkaline-earth (Be2+, Mg2+ and Ca2+) metal ions selective complexes have been theoretically identified. The calculated values the lowest energy band (λmax) of the crown ether derivatives to the alkaline earth metal cations increases from Be, Mg, and then Ca in the complexes [2 M], indicating that these absorption bands are associated to a transition from the HOMO to LUMO transition, which is assigned to metal-to-ligand charge transfer (MLCT).

Ultra-broadband solar absorber based on TiN metamaterial from visible light to mid-infrared

We study and design an ultra-broadband absorber based on TiN metamaterial. The proposed structure consists of a rectangle pillar, two rectangle rings, an Al2O3 substrate, and a TiN substrate. The average absorption in the range of 300–4962 nm is 97.02%. The physical mechanism is illustrated by electric-field and magnetic-field distributions, including the dielectric lossy property of TiN itself in shorter wavelengths, Fabry–Perot resonance, and local surface plasmon resonance in longer wavelengths. The result indicates that the energy absorption spectrum can be well matched with the standard solar spectrum under AM 1.5 over the full range of 300–5000 nm, and then we compare the solar absorption spectrum of different structures. In the end, the influence of different materials and geometrical parameters on absorption is investigated. The absorber can achieve ultra-broadband perfect absorption, and has a simple structure that is easy to manufacture. The result of this work can be applied in many potential fields, for example, thermal photovoltaic power generation, infrared imaging, solar cells, and other optoelectronic devices.

A first principle investigations for electronic, optical and mechanical response of novel Ba2AgIO6 perovskite

The double perovskite compound, Ba2AgIO6 has been studied through density functional theory to explore its mechanical, electronic, and optical properties. To examine the mechanical stability of the compound, elastic constants, Young’s modulus, bulk modulus and shear modulus have been computed. The computed electronic properties show the direct band gap semiconducting nature of the studied perovskite compound. The optical properties of Ba2AgIO6 are interpreted with the help of energy dependent dielectric tensor, absorption, reflection, refraction, and energy loss spectra. From the present study it is found that Ba2AgIO6 is suitable for the various photovoltaic and optoelectronic applications.

Regulating the ESIPT processes and photophysical properties of indole derivates by introducing the appropriate functional groups

In this work, the substitution effect of different electron-donating and electron-withdrawing groups on the electron spectra and excited state intramolecular proton transfer (ESIPT) properties of the chromophore 2-(2-hydroxy-5-methylphenyl)benzo[d]oxazole-5-sulfonic acid (BOM-1) has been studied via the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. All the compounds exhibit the dual-fluorescence emission, and the fluorescence spectra of the derivatives show redshift emission compared with that of the original molecule, resulting in the larger Stokes shift as expected. The results were cross-verified by the molecular geometry, frontier molecular orbitals, infrared spectroscopy and other auxiliary calculations. These results show that the electron-withdrawing group greatly promote the occurrence of the forward ESIPT process and increase the Stokes shift. What is more special is that the Stokes shift and the energy barrier of the forward ESIPT are significantly enlarged by introducing both electron-withdrawing and electron-donating groups. The energy barrier, absorption and fluorescence spectra of luminescent molecules can be adjusted effectively by introducing appropriate functional groups. In addition, the emission spectra from the ultraviolet region (359 nm) to the orange region (601 nm) are obtained. This work would contribute to the understanding of the mechanism of ESIPT reactions and improves the luminescence properties of ESIPT molecules.

Tuning electronic structure and chemical reactivity via oxidation state in molybdenum oxide

Molybdenum oxide has a broad range of applications in areas such as catalysis, antimicrobial coatings, medicine, and sensors. In this study, we have investigated the geometric and electronic structure, thermal stability, and chemical reactivity of molybdenum oxide at different oxidation and electronic charge states using cluster models of Mo7On with density functional theory calculations. A decrease in the energy of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) has been identified as n increases from 0 to 21. Ionization potential and electron affinity of Mo7On correlate strongly with the energies of HOMO and LUMO, and both increase with increasing n. We have identified the most stable CO binding sites on Mo7On, calculated CO binding energy and simulated IR absorption spectrum of COMo7On. An n-dependent increase in CO stretching frequencies and decrease in CO binding energies indicate that electron backdonation from Mo7On to CO governs the changes in CO binding energy as a function of oxide composition. CO stretching frequency in COMo7O21 is 2197 cm−1, which is 55 cm−1 higher than in the gas phase CO molecule, indicating that CO is an electron density donor and the oxide acts as an electron acceptor at this stoichiometric composition. Comparing CO binding energies in neutral and ionic (q=+/-1) COMo7On, there is, in average, a stabilizing effect of excess (missing) charge on CO binding energy at low (high) n.

Radio-absorbing properties of (1-x)BiFeO3 – xLaMnO3 (0.1 ≤ x ≤ 0.9) solid solutions

In the frequency range of 3.2–12 GHz, the microwave energy absorption spectra of a series of the (1-x)BiFeO3 – xLaMnO3 solid solutions with a concentration of x = 0.1 − 0.9 were studied. The spectra contain the absorption maxima of the resonant type, the magnitudes, resonant frequencies, and number of which depend on the x concentration and temperature. At different heights from the surface of the samples under study, located on the microstrip line, the emission spectra of the electric and magnetic components of the microwave field were obtained. The X-ray diffraction data and the obtained absorption and emission spectra are interconnected and complement each other. The features of the spectra are discussed from the point of view of the contribution to the emission and absorption of the energy of the dielectric walls of the twins resonating in the electromagnetic field. The features of the magnetic moments of multiferroics are also discussed.

Determination of Nicotine in Human Saliva Using Electrochemical Sensor Modified with Green Synthesized Silver Nanoparticles Using Phyllanthus reticulatus Fruit Extract

In this study, for the first time, Phyllanthus Reticulatus fruit extract was utilized as a reducing agent in the synthesis of silver nanoparticles (Ag-NPs). For sample analysis, a number of approaches were employed. The synthesized Ag-NPs have a spherical shape and a homogeneous in size. The well-known crystal structure and optical energy absorption spectrum of Ag-NPs were respectively revealed by the XRD and UV-VIS analysis. This new method is simple and eco-friendly for producing silver and other noble metals in large quantities. The Ag-NPs modified glassy carbon electrode was prepared for nicotine oxidation which indicated that Ag NPs had the ability to enhance the electron transfer rate of the oxidation process. In 0.1 M phosphate buffer (pH of 7.4), a significant increase in the oxidation peak current of nicotine was observed at the modified electrode. Cyclic voltammetry, amperometry, and electrochemical impedance spectroscopy characterizations showed that Ag-NPs had better electrocatalytic performance toward nicotine (NIC) oxidation with good stability, and selectivity. This sensor showed a linear response with the concentration of NIC in the range of 2.5 to 105 μM. The limit of detection (LOD) was estimated to be 0.135 μM. The interference analysis was carried out on the Ag-NPs/GCE with various molecules like acetic acid, ascorbic acid, calcium chloride, glucose, magnesium chloride, urea, and uric acid. Hence, these molecules did not interfere with NIC detection, indicating a perfect selectivity of Ag-NPs/GCE. Moreover, the Ag-NPs/GCE sensor was effectively applied to detect NIC in a real-world sample (saliva) of a tobacco chewer. Furthermore, the Ag-NPs/GCE sensor exhibited very good stability and repeatability in human saliva samples. Finally, Ag-NPs/GCE was also successfully applied to detect spiked nicotine in saliva samples with high recovery value, indicating its high accuracy and effectiveness in NIC analysis.

Robustness of electronic screening effects in electron spectroscopies: Example of V2O5

In bulk and low-dimensional extended systems, the screening of excitations by the electron cloud is a key feature governing spectroscopic properties. Widely used computational approaches, especially in the framework of many-body perturbation theory, such as the GW approximation and the resulting approximate Bethe-Salpeter equation, are explicitly formulated in terms of the screened Coulomb interaction. In the present work we explore the effect of screening in absorption and electron energy loss spectroscopy, concentrating on the effect of local distortions on the screening and elucidating the resulting changes in the various spectra. Using the layered bulk oxide V$_2$O$_5$ as prototype material, we show in which way local distortions affect the screening, and in which way changes in the screening impact electron energy loss and absorption spectra including excitons. We highlight cancellations that make many-body effects in the spectra very robust with respect to structural modifications, while the band structure undergoes significant changes and the nature of the excitations may also be affected. This yields insight concerning the structure-properties relations that are crucial for the use of V$_2$O$_5$ as energy storage material, and more generally, that may be used to optimize the analysis and the calculation of electronic spectra in complex materials.

A Highly Efficient Infinity-Shaped Large Angular- and Polarization-Independent Metamaterial Absorber

An efficient diagonally symmetric infinity-shaped broadband solar absorber has been demonstrated in this research paper. The structure was developed with an infinity-shaped resonator made of titanium (Ti) and gallium arsenide (GaAs) at the base substrate layer to achieve absorption in a wideband spectrum under solar energy radiation, and absorption efficiencies were calculated employing the finite element method. The average solar energy absorption spectrum ranges from the ultraviolet to the mid-infrared regions, and 93.93% average absorption in this band is achieved. Moreover, bandwidths of 2800 and 1110 nm were observed, and, in these bands, we attained continuous absorption above 90% and 95%, respectively, with average absorption rates of 93.93% and 96.25%, respectively. Furthermore, based on this solar energy absorber, which was optimized after varying many design parameters, it is also observed that the developed design is angle-insensitive from 0° to 50° and polarization-insensitive from the results of the transverse electric (TE) and transverse magnetic (TM) modes. The developed infinity-shaped broadband solar absorber design is highly efficient and provides broadband absorptance that can be used as an absorber layer in solar cells.

An efficient protocol for excited states of large biochromophores.

Efficient energy transport in photosynthetic antenna is a long-standing source of inspiration for artificial light harvesting materials. However, characterizing the excited states of the constituent chromophores poses a considerable challenge to mainstream quantum chemical and semiempirical excited state methods due to their size and complexity and the accuracy required to describe small but functionally important changes in their properties. In this paper, we explore an alternative approach to calculating the excited states of large biochromophores, exemplified by a specific method for calculating the Qy transition of bacteriochlorophyll a, which we name Chl-xTB. Using a diagonally dominant approximation to the Casida equation and a bespoke parameterization scheme, Chl-xTB can match time-dependent density functional theory's accuracy and semiempirical speed for calculating the potential energy surfaces and absorption spectra of chlorophylls. We demonstrate that Chl-xTB (and other prospective realizations of our protocol) can be integrated into multiscale models, including concurrent excitonic and point-charge embedding frameworks, enabling the analysis of biochromophore networks in a native environment. We exploit this capability to probe the low-frequency spectral densities of excitonic energies and interchromophore interactions in the light harvesting antenna protein LH2 (light harvesting complex 2). The impact of low-frequency protein motion on interchromophore coupling and exciton transport has routinely been ignored due to the prohibitive costs of including it in simulations. Our results provide a more rigorous basis for continued use of this approximation by demonstrating that exciton transition energies are unaffected by low-frequency vibrational coupling to exciton interaction energies.

An ultra-broadband solar absorber based on α-GST/Fe metamaterials from visible light to mid-infrared.

In this paper, we proposed an ultra-broadband and high absorption rate absorber based on Fe materials. The proposed absorber consists of a rectangle pillar, two rings, a SiO2 film, a Ge2Sb2Te5(GST) planar cavity, an Fe mirror, and a SiO2 substrate. The average absorption reaches 98.45% in the range of 400-4597 nm. We investigate and analyze the electric field distributions. The analysis of the physical mechanism behind the broadband absorption effect reveals that it is driven by excited surface plasmons. Furthermore, the absorber can maintain high absorption efficiency under a large incident angle. The geometrical symmetric structure possesses polarization insensitivity properties. The proposed structure allows for certain manufacturing errors, which improves the feasibility of the actual manufacture. Then, we investigate the effect of different materials on absorption. Finally, we study the matching degree between the energy absorption spectrum and the standard solar spectrum under AM 1.5. The results reveal that the energy absorption spectrum matches well with the standard solar spectrum under AM 1.5 over the full range of 400 to 6000 nm. In contrast, energy loss can be negligible. The absorber possesses ultra-broadband perfect absorption, a high absorption rate, and a simple structure which is easy to manufacture. It has tremendous application potential in many areas, such as solar energy capture, thermal photovoltaics, terminal imaging, and other optoelectronic devices.

First-principles study on the photocatalytic field of two-dimensional Janus BiSY (Y = I, Br, Cl) monolayers

This study demonstrates the photocatalytic performance of two-dimensional Janus BiSY (Y = I, Br, Cl) based on energy bands, vacuum energy levels, absorption spectra, and reaction potential diagrams.

Kinetic Salt Effect on Base-Catalyzed Isomerization of d-Glucose into d-Fructose.

Isomerization of d-glucose (Glc) into d-fructose (Fru) is of great importance for food sector as well as for valorization of lignocellulosic biomass. Soluble and solid bases exhibit high catalytic activity for the isomerization. Here, we report a salt effect on the base-catalyzed aqueous-phase Glc-Fru isomerization. Addition of soluble salts (Na2 SO4 , NaNO3 , K2 SO4 , and NaCl) results in an increased apparent reaction rate (factors of 1.5 to 6). The salt effect was observed both in the presence of soluble base NaOH at constant pH value and solid bases MgO, Li3 PO4 , and Mg-Al hydrotalcite. Apparent activation energy and UV absorption spectra were not significantly influenced by addition of salts. Potentiometric titration showed that the acidity constants of the saccharides increase in the presence of electrolytes. Since the rate of the isomerization depends on the thermodynamic acidity constant of Glc, the isomerization is accelerated by the presence of electrolytes.

18.66% Efficiency of Polymer Solar Cells Employing Two Nonfullerene Acceptors with Fluorine or Chlorine Substitution

Organic semiconducting materials with fluorine or chlorine substitution are commonly designed to prepare efficient polymer solar cells (PSCs) through finely modulating the energy levels and absorption spectra. Herein, two small molecular acceptors with fluorine substitution L8‐BO or chlorine substitution eC9‐2Cl are selected to prepare ternary PSCs with PM6 as polymer donor. The optimal ternary PSCs exhibit a power conversion efficiency of 18.66%, benefiting from the simultaneously increased open‐circuit voltage (VOC) of 0.89 V, short‐circuit current density (JSC) of 26.63 mA cm−2, and fill factor of 78.74% when the content of chlorine substitution eC9‐2Cl is about 20 wt% in acceptors. Fluorinated and chlorinated substitutions can improve the VOC or JSC of the corresponding binary PSCs, which can be recombined into efficient ternary PSCs through optimizing their content in acceptors. Chlorinated materials have special crystalline conditions due to the specific features of the chlorine atoms with large atomic radius and the empty 3d orbits compared to the corresponding fluorinated materials. Adding an appropriate amount of the chlorine substitution eC9‐2Cl further enhances the crystallization and intermolecular interaction of the ternary PSCs, which is beneficial for charge transport in the active layer and for device performance improvement.