Energies Of Electronic States Research Articles

Theoretical Insights into Size and Dielectric Confinement : Unraveling Real and Imaginary Parts of the Effective Complex Dielectric Function in Spherical Multilayered Quantum Dots with Oxide Interfaces

A quantitative numerical exploration is conducted to scrutinize the combined effects of size and dielectric confinement consequences on the electronic and optical characteristics of spherical multilayered quantum dot CdSe/ZnS/CdSe/ZnS (SMLQD) and its inverted configuration ZnS/CdSe/ZnS/CdSe (ISMLQD) buried into two oxides : HfO2 and SiO2. By employing the effective mass approximation (EMA) and the density matrix approach (DMA), the derived quantized electron energy states and their associated wave functions were obtained by solving the Schrödinger equation in a spherical coordinates. The dipole transition element, both real and imaginary parts of the effective complex dielectric function (ECDF) as well as its linear, nonlinear and total counterparts are brought out for various values of inner core radii, number density of QDs and incident photon intensity. In addition, a specific analysis of electron probability distributions is provided to gain a clearer understanding of the underlying physical factors. Our findings point to a notable influence of these mentionned factors on the computed coefficients. The study unveils that the dielectric mismatch occurring at the system/oxide interfaces plays a crucial role in modifying the electronic structure and a substantial impact on both linear and third-order nonlinear components is witnessed.

Layered double hydroxides derived prussian blue analogue nanocage confining NiCoP nanoparticles as efficient bifunctional electrocatalyst

Designing novel electrocatalysts with excellent catalytic activity for efficient water splitting is necessary to achieve the large-scale H2/O2 production from renewable resources. In this study, a facile hydrothermal method followed by low-temperature phosphorylation treatment was employed to fabricate a nanocage of prussian blue analogue encapsulating NiCoP nanoparticles (NiCoP@PBA), which was derived from the layered double hydroxide precursor. As a bifunctional non-precious metal electrocatalyst, NiCoP@PBA demonstrates superior performance in KOH electrolyte water splitting, with overpotentials of 59 mV for electrocatalytic hydrogen evolution reaction (HER) and 263 mV for oxygen evolution reaction (OER) at 10 mA cm−2. The catalyst also exhibits low Tafel slopes of 54 mV dec−1 for HER and 120 mV dec−1 for OER, reflecting efficient charge transfer kinetics. DFT simulations show that the Co–N moieties at the heterogeneous interface of NiCoP@PBA can optimize the surface electron distribution and energy states, thus facilitating efficient electron-hole pair separation, significantly enhancing catalytic activity for both HER and OER process, and significantly extending the electrocatalyst's service life. Our approach can be extended to more non-precious metal electrocatalysts, which is significant for the design of efficient bifunctional water splitting electrocatalysts.

Intrinsic surface states with electron–surface optical phonon interaction influence in wurtzite Zn-IV-N2 semiconductors

The electronic intrinsic surface states in wurtzite Zn-IV-N2 (with group-[Formula: see text], Ge and Si) semiconductors were investigated using an intermediate-coupling variational approach considering the electron–surface optical phonon interaction influence. The intrinsic surface state energy distribution and the average penetrating depth of surface state eigen-wave function of the electron have been evaluated numerically by changing the surface potential barrier [Formula: see text] for wurtzite ZnSnN2, ZnGeN2 and ZnSiN2, respectively. The results show that the electronic intrinsic surface state energy increased linearly with increasing surface potential barrier [Formula: see text] for all the calculated materials. The result also indicated that the electronic intrinsic surface state energies variations due to the influence of electron–surface optical phonon interaction are dozens of[Formula: see text]meV. The average penetrating depth of electronic surface state eigen-wave function is independent of [Formula: see text]. Its value is no more than the corresponding material’s lattice constant. The electronic scattering by surface optical phonon should be taken into account in the study of the intrinsic surface state of electrons in the group of Zn-IV-nitrides (with [Formula: see text], Ge and Si) semiconductors, especially for materials having strong electron–phonon interaction and wide band gap.

Low Temperature Interface Modification: Electrochemical Dissolution Mechanism of Typical Iron and Nickel Base Alloys

<p>Due to its unique advantages, electrochemical machining (ECM) is playing an increasingly significant role in the manufacture of difficult-to-machine materials. Most of the current ECM research is conducted at room temperature, with studies on ECM in a cryogenic environment not having been reported to date. This study is focused on the electrochemical dissolution characteristics of typical iron and nickel base alloys in NaNO<sub>3</sub> solution at low temperature (−10°C). The polarization behaviors and passive film properties were studied by various electrochemical test methods. The results indicated that a higher voltage is required for decomposition and more pronounced pitting of their structures occurs in the passive zone in a cryogenic environment. A more in-depth study of the composition and structure of the passive films by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy showed that the passive films of the alloys are modified at low temperature, and their capacitance characteristics are more prominent, which makes corrosion of the alloys more likely to occur uniformly. These modified passive films have a huge impact on the surface morphologies of the alloys, with non-uniform corrosion suppressed and an improvement in their surface finish, indicating that lowering the temperature improves the localization of ECM. Together with the cryogenic impact of electron energy state compression, the accuracy of ECM can be further improved.</p>

Dihydrophenanthrene Open-Shell Singlet Diradicals and Their Roles in the Mallory Photocyclization Reaction.

A computational study (ωB97X-D/6-31G(d)) of the Mallory photocyclization reaction has revealed that the well-established dihydrophenanthrene (DHP) intermediates can adopt either closed-shell (CS) or open-shell-diradical (OS) singlet ground states. A detailed study of the properties of DHPs allowed their classifications as OS, borderline-OS, borderline-CS, or CS intermediates. The triplet electronic state and higher energy CS* isomer of all the OS singlet diradicals were computationally located, and the expected relationship between the diradical index, yo, and the triplet energy and the OS-CS* energy gaps was established. The importance of aromaticity in stabilizing the OS singlet diradicals was confirmed by using the Harmonic Oscillator Model of Aromaticity (HOMA). The thermal decompositions of DHPs by cycloreversions to regenerate the Mallory starting materials were also studied. The cycloreversion mechanism was described as a homolytic cleavage characterized by an anchimeric assistance continuum promoted by bis-β-homolytic cleavage.

(Invited) Manipulating Light Emission from Rare Earth Doped Nanoparticles for Applications in Theranostics

Luminescent nanomaterials that can be excited, as well as emit, in the near-infrared (NIR) have been investigated for use in a plethora of applications including nanomedicine, nanoelectronics, biosensing, bioimaging, photovoltaics, photocatalysis, etc. The use of NIR light for excitation mitigates some of the drawbacks associated with high-energy (UV or blue) excitation, for example, little to no background autofluorescence from the specimen under investigation as well as no incurred photodamage. Moreover, one of the biggest limitations is of course, that of penetration. As such, NIR light can penetrate tissues much better than high-energy light especially when these wavelengths lie within the three biological windows (BW-I: 700-950, BW-II: 1000-1350, BW-III: 1550-1870 nm) where tissues are optically transparent. At the forefront of NIR excited nanomaterials are rare earth doped nanoparticles, which due to their 4f electronic energy states can undergo conventional (Stokes) luminescence and emit in the three NIR biological windows. However, unlike other classes of nanoparticles, they can also undergo a multiphoton process (known as upconversion) where the NIR excitation light is converted to higher energies resulting in anti-Stokes luminescence spanning the UV-visible-NIR regions. Perhaps the biggest impact of such materials would be in the field of disease diagnostics and therapeutics, now commonly referred to as theranostics. Due to the versatility of their optical properties, it now becomes possible to generate high-energy light (UV or blue) in situ to trigger other light activated therapeutic modalities (i.e. drug release) while using the NIR emission for diagnostics (i.e. bioimaging, nanothermometry). Here, we present the synthesis of various NIR excited (and emitting) rare earth doped core/shell (and multishell) nanoparticles and demonstrate how their luminescence properties can be exploited for potential use in diverse biomedical applications.

(Invited) Luminescence Nanothermometers: Using Light to Detect Temperature

Rare earth doped nanoparticles have recently emerged as versatile luminescent probes for a number of biological applications resulting from their interesting photophysical properties. These nanoparticles can be excited with near-infrared (NIR) light, which is a strict requirement for biomedical applications due its light penetration capabilities. Furthermore, rare earth doped nanoparticles possess a multitude of 4f electronic energy states and excitation with NIR light can therefore lead to different excitation mechanisms. For example, following NIR excitation, the nanoparticles can undergo upconversion where multiple emissions are observed with energies higher than the excitation wavelength. Also, they can undergo conventional luminescence where emission at lower energies than the excitation wavelength can be observed (known as downshifted luminescence). Here, we show that it is possible to harness these various emissions (upconverted and downshifted) to design luminescence nanothermometers capable of detecting temperature in living organisms.

Ground State Electron Energies in sp3 Hybridized Si and C atoms in C-terminated 4H-SiC

Ground State Electron Energies in sp3 Hybridized Si and C atoms in C-terminated 4H-SiC

Molecular spectroscopy as a laboratory experiment: Measurement of important parameters of sodium diatomic molecules

We present an inexpensive sodium molecular spectroscopy experiment for use in an advanced undergraduate laboratory course in physics or chemistry. The molecules were excited predominantly from the ground X1Σg+(v″ = 15) state to the B1Πu(v′ = 6) state using a commercially available 532-nm broadband diode laser. The laser-induced molecular fluorescence was measured using a miniature fiber-coupled spectrometer at a resolution of 0.5 nm. The spectral peak assignments were done by comparing the observed spectrum with the calculated Franck–Condon values. Important molecular constants such as fundamental frequency, anharmonicity, bond strength, and dissociation energy of the ground electronic state were determined by using the Birge–Sponer extrapolation method. The presence of highly visible blue glowing molecules along the green laser beam creates an engaging laboratory experience. Emphasis is placed on students developing their understanding of the molecular structure, practicing molecular spectroscopic techniques, and applying knowledge of light–matter interactions to a physical system.

First Principles Calculation of Compatibility between Environmentally Friendly Insulating Gas C5F10O and CuW Contacts

The insulating gas and contacts in the arc extinguishing chamber of high‐voltage circuit breakers are the focus of research. In practical applications, the gas may react with the surface of the contacts. In this paper, C5F10O environmental friendly insulating gas, which has one of the potential alternatives, is selected as the research object. The compatibility of C5F10O and its decomposition products with CuW contacts was studied. This article uses the Dmol3 program based on density functional theory. The adsorption energy, transfer charge, and density of electronic states of C5F10O and selected typical decomposition products on the Cu (111) surface and Cu‐W surface were calculated, respectively. It was found that the original CuW metal properties were not changed before and after adsorption. The carbonyl O atom in C5F10O is easily adsorbed on the top of the Cu (111) surface, forming a stable CuO bond, which belongs to chemical adsorption. The interaction of the other three adsorption sites is weaker than that of the top site adsorption, which belongs to physical adsorption. C5F10O exhibits more active charge transfer and forms active W‐O chemical bonds when adsorbed on CuW surfaces than SF6. C5F10O has poorer compatibility with CuW alloy than SF6. C2F4 and C3F6 in the decomposition gas are chemically adsorbed on the Cu‐W surface. CO2, CF4, C2F6, and C3F8 do not form chemical bonds on the CuW surface. The adsorption stability of COF2 is weaker than that of CF4, C2F6, and C3F8. Compared with SF6 adsorption, the compatibility of C5F10O and CO2 on the surface of CuW contact is inferior to that of Cu contact. CF4, C2F6, C3F8, and COF2 in the decomposition gas can be compatible with the surface of the CuW contact. C2F4 and C3F6 cannot be well compatible with the surface of CuW contacts. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Lanthanide‐Doped Nanomaterials for Tumor Diagnosis and Treatment by Second Near‐Infrared Fluorescence Imaging

AbstractLanthanides have unique electronic configurations and stepped energy states of [Xe]4fN, which endows them with advantages including stable luminescence, large stokes shift, wide excitation spectral bands, and long fluorescence lifetime. NIR‐II fluorescence imaging overcomes the strong tissue absorption, scattering, and spontaneous fluorescence interference of traditional fluorescence and can achieve deeper tissue penetration and higher spatial and temporal resolution in vivo imaging. Lanthanides hold great potential for in vivo biosensing and bioimaging. In this work, the design and preparation of nanomaterials doped with different lanthanide elements are reviewed in this paper. Applications of lanthanide‐doped nanomaterials to different tumor therapeutics through NIR‐II fluorescence imaging and the unique potential of NIR lanthanide nanomaterials in tumor diagnosis and therapy are also discussed.

Organic Excitonic State Management by Surface Metallic Coupling of Inorganic Lanthanide Nanocrystals

AbstractThe ability to harness charges and spins for control of organic excitonic states is critical in developing high‐performance organic luminophores and optoelectronic devices. Here we report a facile strategy to efficiently manipulate the electronic energy states of various organic phosphors by coupling them with inorganic lanthanide nanocrystals. We show that the metallic atoms exposed on the nanocrystal surface can introduce strong coupling effects to 9‐(4‐ethoxy‐6‐phenyl‐1,3,5‐triazin‐2‐yl)‐9H‐carbazole (OCzT) and some organic chromophores with carbazole functional groups when the organics are approaching the nanocrystals. This unconventional organic–inorganic hybridization enables a nearly 100 % conversion of the singlet excitation to fast charge transfer luminescence that does not exist in pristine organics, which broadens the utility of organic phosphors in hybrid systems.

Organic Excitonic State Management by Surface Metallic Coupling of Inorganic Lanthanide Nanocrystals.

The ability to harness charges and spins for control of organic excitonic states is critical in developing high-performance organic luminophores and optoelectronic devices. Here we report a facile strategy to efficiently manipulate the electronic energy states of various organic phosphors by coupling them with inorganic lanthanide nanocrystals. We show that the metallic atoms exposed on the nanocrystal surface can introduce strong coupling effects to 9-(4-ethoxy-6-phenyl-1,3,5-triazin-2-yl)-9H-carbazole (OCzT) and some organic chromophores with carbazole functional groups when the organics are approaching the nanocrystals. This unconventional organic-inorganic hybridization enables a nearly 100 % conversion of the singlet excitation to fast charge transfer luminescence that does not exist in pristine organics, which broadens the utility of organic phosphors in hybrid systems.

Linearized Pair-Density Functional Theory for Vertical Excitation Energies.

Multiconfiguration pair-density functional theory (MC-PDFT) is a computationally efficient method that computes the energies of electronic states in a state specific or state average framework via an on-top functional. However, MC-PDFT does not include state interaction among these states since the final energies do not come from the diagonalization of an effective model-space Hamiltonian. Recently, multistate extensions such as linearized PDFT (L-PDFT) have been developed to accurately model the potentials near conical intersections and avoided crossings. However, there has not been any systematic study evaluating their performance for predicting vertical excitations at the equilibrium geometry of a molecule, when the excited states are generally well separated. In this paper, we report the performance of L-PDFT on the extensive QUESTDB data set of vertical excitations using a database of automatically selected active spaces. We show that L-PDFT performs well on all these excitations and successfully reproduces the performance of MC-PDFT. These results further demonstrate the potential of L-PDFT, as its scaling is constant with the number of states included in the state-average manifold, whereas MC-PDFT scales linearly in this regard.

Fragmentation of Multiply Charged C10H8 Isomers Produced in keV Range Proton Collision

The dissociation of multiply charged C10H8 isomers produced in fast proton collisions (velocities between 1.41 and 2.4 a.u.) is discussed in terms of their fundamental molecular dynamics, in particular the processes that produce different carbon clusters in such a collision. This aspect is assessed with the help of a multi-hit analysis of daughter ions detected in coincidence with the elimination of H+ and CHn+ (n = 0 to 3). The elimination of H+/C+ is found to be significantly different from CH3+ loss. The loss of CH3+ proceeds through a cascade of momentum-correlated dissociations with the formation of heavy ions such as C9H5+, C9H52+ and C7H3+. The structure of such large fragment ions is predicted with the help of their calculated ground state electronic energies and the multi-hit time-of-flight (ToF) correlation between the second and third hit fragments if detected. Furthermore, we report experimentally the super-dehydrogenation of naphthalene and azulene targets, with evidence of complete dehydrogenation in a single collision.

Super-strong Zn and S atomic terminals in an organic/inorganic hybrid S-scheme polyimide based heterojunction for efficient photocatalytic treatment of mixed pollutant wastewater

Integrated oxidation and reduction reactions in the field of wastewater treatment with mixed high concentrations of sewage achieved by photocatalysis are highly desirable but still challenging. The construction of the S-scheme heterojunction system is expected to be a promising strategy to provide carriers with strong redox ability for oxidation of oxytetracycline hydrochloride (OTC) with simultaneous reduction of hexavalent chromium (Cr(VI)). Reduced graphene oxide (rGO) and ZnIn2S4 (ZIS) were successively assembled on perylene diimide polymer (PDIP) nanorods to form the S-scheme ZIS/rGO/PDIP heterojunction. The construction of organic–inorganic systems achieves wide light absorption, enhanced exciton dissociation and accelerated charge separation. A non-radiation-quenched electron transport path is formed in the ZIS/rGO/PDIP system from the conduction band of PDIP through rGO to the valence band of ZIS. The electronic energy state of the S-scheme ZIS/rGO/PDIP heterojunction was changed, and the Zn and S atomic terminals can realize strong adsorption of OTC and Cr(VI).

Molecular modelling of fused heterocycle-based asymmetric non-fullerene acceptors for efficient organic solar cells

Heterocycle substitution plays a key role in designing an ultra-narrower bandgap (ultra-NBG) small molecule-based (SM) non-fullerene acceptors (NFAs) for organic solar cells (OSCs). The NFAs molecules have great significance because of their ability to improve efficiency, narrow band gap, better charge separation, higher absorption spectra, and overall device performance. However, the impact of heterocycles such as benzoselenadiazole (BSe) on optoelectronics characteristics is still unclear. Herein, seven asymmetric NFAs based on BSe electron-deficient fused-ring core were designed from the reference (R) BTP-Se. All seven NFAs exhibited a strong absorption phenomenon from visible to near-infrared (NIR) region, corresponding to the ultra-NBG and lower excitation energy (Ex). These designed asymmetric materials (BTP1-BTP7) along with R are fully characterized theoretically with various advanced quantum chemical techniques. The optical and optoelectronics features were explored with density functional theory (DFT) and time-dependent (TD-DFT) simulations. The in-depth calculations related to density of state (DOS), transition density of state (TDM), open-circuit voltage, fill factor, and reorganization energy of electrons and holes are performed intensively. BTP3 has an optical band gap narrow of 1.76 eV and an outstanding absorption maximum of 906.85 nm. For charge transfer, a donor:acceptor complex study of BTP3:PBDBT is carried-out. We hope that this may provide a favourable strategy for building highly efficient near infrared (NIR)-based OSCs.

Theoretical Study on the Spectroscopic Properties and Photodissociation Mechanism of Dibromocarbene.

Detailed calculations on the electronic states of dibromocarbene (CBr2) herein are presented. First, the spectroscopic properties of the electronic states including geometry parameters, harmonic vibrational frequencies and transition energies of the lowest electronic states of the neutral radical were calculated in detail using the internally contracted multireference configuration interaction methods including Davidson correction (icMRCI+Q) with correlation consistent basis sets of aug-cc-pVXZ (X = T, Q, 5). Second, as CBr2 including two Br atoms, the Spin-Orbit Coupling (SOC) effect on the spectroscopic parameters and the one-dimensional cuts of the potential energy surface (PESs) of the lowest three states were studied. The barrier to linearity and dissociation of the singlet state were discussed. Third, the one-dimensional cuts along with the vertical transition energy (VTE), the oscillator strength, and so on of the electronic states related to the several lowest dissociation limits of CBr2 were calculated at the icMRCI+Q/aug-cc-pVTZ level. Based on the computed results of the electronic states of the radical, the photodissociation mechanism in the UV region were discussed in detail. The ab initio calculations are compared with the previous theoretical and experimental data and are in good agreement. The present work will provide a comprehensive understanding on the electronic structures and dissociation dynamics for the electronic states of the CBr2 radical.

Theoretical Study of Hydrostatic Pressure and Temperature Effect on a Multi-Quantum well ZnO/Zn<sub>1-X</sub>Mg<sub>x</sub>O Containing a Staircase Defect for Sensing Application

This work describes a theoretical and analytical study of a temperature and pressure sensor based on II-VI semiconductors with a simple multi-quantum wells (MQWs) structure. The proposed sensor operates by detecting changes in the intensity (transmission coefficient) and energy of localized electronic states inside gaps under external perturbations of hydrostatic pressure and temperature. Specifically, the proposed MQWs structure is ZnO/Zn1-XMgXO with 10 cells, each containing two materials that form the wells and barriers, respectively. The structure is perturbed by a staircase defect consisting of three defects of the same material or geomaterial. The Green function method is used to study the transmittance of the structure, with cleavage and coupling operators employed. The objective of the work is to explore a new type of defect for use in sensing applications such as multi-quantum well sensors. Key parameters for evaluating the sensor's performance include full width at half maximum (FWHM), sensor sensitivity (S), quality factor (QF), detection limit (DL), signal-to-noise ratio (SNR), dynamic range (DR), detection accuracy (DA), the figure of merit (MF), and standard deviation. These parameters can be optimized by adjusting structural parameters such as the thickness of the staircase or material concentration. The study found that a geomaterial staircase defect provides higher sensitivity to pressure and temperature changes. Additionally, the step (δx) of the staircase defect influences the sensitivity of the localized states: with increasing steps, δx improves sensitivity to temperature and decreases sensitivity to pressure.

H2 formation via non-Born-Oppenheimer hydrogen migration in photoionized ethane

Neutral H2 formation via intramolecular hydrogen migration in hydrocarbon molecules plays a vital role in many chemical and biological processes. Here, employing cold target recoil ion momentum spectroscopy (COLTRIMS) and pump-probe technique, we find that the non-adiabatic coupling between the ground and excited ionic states of ethane through conical intersection leads to a significantly high yield of neutral H2 fragment. Based on the analysis of fingerprints that are sensitive to orbital symmetry and electronic state energies in the photoelectron momentum distributions, we tag the initial electronic population of both the ground and excited ionic states and determine the branching ratios of H2 formation channel from those two states. Incorporating theoretical simulation, we established the timescale of the H2 formation to be ~1300 fs. We provide a comprehensive characterization of H2 formation in ionic states of ethane mediated by conical intersection and reveals the significance of non-adiabatic coupling dynamics in the intramolecular hydrogen migration.