Theoretical Calculations Of Energy Levels Research Articles

A dual‐responsive luminescent sensor for efficient detection of 3‐nitrotyrosine and dipicolinic acid biomarkers based on copper(II) organic framework

The trace detection of biomarkers in real samples has profound a most important significance in the early diagnosis and daily monitoring of diseases. Based on the ligand pre‐design strategy, a novel 3D CuMOF, with the formula of {[Cu4(BTPB)(μ2‐OH)2(H2O)5]·3H2O}n, was fabricated by using the hexacarboxyl ligand of 1,4‐bis(2,4,6‐tricarboxylpyrid‐5‐yl)benzene (H6BTPB) and tetranuclear {Cu4(COO)4(μ2‐OH)2} SBUs. Benefiting from the robust framework and unique luminescence performance, the prepared CuMOF displays great potential as a dual‐responsive efficient luminescent sensor in “turn‐off” detection of 3‐nitrotyrosine (3‐NT) biomarker and “turn‐on” detecting the anthrax biomarker of dipicolinic acid (DPA), with detection limits (LOD) for 3‐NT and DPA being 110.8 ng/ml and 85.2 ng/ml, respectively. Additionally, the practicality and compatibility of such developed sensors were verified by quantifying 3‐NT and DPA biomarkers in diluted serum and urine samples with satisfactory recoveries. Further, the theoretical calculations of energy levels as well as the spectral overlap between the analytes and CuMOF were conducted to elucidate the possible sensing mechanisms. This work demonstrated that MOFs‐based luminescent sensors are evolving as an efficacious and equable approach for the detection of biomarkers in real samples.

The study of atomic structure parameters for [formula omitted] = 4 - [formula omitted] = 3 transitions in Mg-like ions with [formula omitted]

Multiconfiguration Dirac–Hartree–Fock (MCDHF) and relativistic configuration interaction (RCI) methods are utilized for theoretical calculations of energy levels, wavelengths, line strengths, absorption oscillator strengths, and transition probabilities in 3s2-3s4p, 3s3p-3s4s, 3s3p-3s4d, 3s3p-3p4p, 3s3d-3s4f, 3p2-3p4s, 3p2-3p4d, and 3p3d-3p4f transitions in Mg-like ions with 15≤Z≤30. The calculations of energies account for Breit interaction and quantum electrodynamics (QED) contributions. The active space approximation is employed for the calculations, and energy converges when the active orbital set is increased to n = 7. The calculated lowest 78 levels including valence and core–valence correlations in Mg-like ions with Z=15–30 show good agreement with experiment results and other calculations. The relative difference between calculated wavelengths and experiment values exhibits a decreasing trend as the atomic numbers increase, and the difference is better than 1% for a majority of transitions. To evaluate the accuracy of the wave functions and transition parameters, the quantity dT is analyzed within 0.1 for most strong transitions. The transition probabilities are compared with other theoretical values to analyze with line strength S. Such calculations may provide valuable data for the experimental study of plasma diagnostics and modeling as there are others.

The origin of carbon-related carrier compensation in p-type GaN layers grown by MOVPE

The role of carbon impurities in p-type GaN layers grown by metalorganic vapor phase epitaxy (MOVPE) was investigated. The lightly Mg-doped (∼1017 cm−3) p-type GaN samples with different carbon concentration [C] were prepared by controlling growth temperature and pressure. Temperature-dependent Hall-effect analyses exhibited an increase in donor concentration with increasing [C]. The low-temperature mobility also decreased with increasing [C], as a result of mobility limitation due to ionized impurity scattering. These results show that carbon atoms in MOVPE-grown p-GaN layers act as ionized donors and cause carrier compensation. Deep-level transient spectroscopy (DLTS) using bias pulses detected the existence of Hd traps (EV +0.88 eV) arising from the 0/−1 charge state of carbon on nitrogen sites (CN). The concentrations of Hd traps closely corresponded to [C] values in p-type GaN layers. Employing low-frequency capacitance DLTS to avoid carrier freeze-out at low temperatures, we newly discovered the Ha trap (EV +0.29 eV) whose concentration was directly proportional to the [C] value. These findings suggest that the Ha trap originates from CN identical to the Hd trap. Based on prior theoretical calculations of energy levels, the Ha trap can reasonably be assigned to a +1/0 donor state of CN. These results strongly suggest that a CN having two different charged states can compensate an electron and a hole in n-type and p-type GaN layers, respectively.

Persistent photoconductivity in ZnO nanowires: Influence of oxygen and argon ambient

ZnO nanowires typically show persistent photoconductivity (PPC), which depends in their temporal behaviour on the ambient. We investigate ZnO nanowires in oxygen and argon ambient and analyze the PPC both on the short and on the long time scale to sort out the underlying mechanisms. Wavelength dependent excitation shows the energy barrier for the PPC to be around 150 meV below the band gap of ZnO, independent of the ambient atmosphere. In photocurrent measurements at constant wavelength, a log-logistic dependence of the conductivity on the partial oxygen pressure is observed. The experimental results are compared to a model of Bonasewicz et al. [J. Electrochem. Soc. 133, 2270 (1986)] and can be explained by oxygen adsorption processes occurring on the surface of the ZnO nanowires. From temperature dependent measurements of the decay times in oxygen and argon ambient, the related activation energies for the fast and slow decay processes are determined. Comparing our results to theoretical calculations of energy levels of intrinsic defects [Janotti and Van de Walle, Phys. Status Solidi B 248, 799 (2011)], we find oxygen vacancies to be related to the fast decay processes, whereas adsorption and desorption processes of oxygen on the ZnO nanowire surface account for the slow part.

Effects of electronic structure and interfacial interaction between metal-quinoline complexes and TiO2 on visible light photocatalytic activity of TiO2

Two metal-quinoline complexes, Fe(III)-8-hydroxyquinoline-5-sulfonic acid (Fe-HQS) and Er(III)-8-hydroxyquinoline-5-sulfonic acid (Er-HQS), were used as sensitizers of TiO2 for improving visible light photocatalytic activity of TiO2. UV–vis spectra, X-ray Diffraction, X-ray Photoelectron Spectroscopy, Scanning Electron Microscope and Transmission Electron Microscope were put to use to characterize the structure and morphology of Fe-HQS-TiO2 and Er-HQS-TiO2. The effects of interfacial electron transfer and energy level matching between each complex and TiO2 were researched intensively. Er-HQS-TiO2 and Fe-HQS-TiO2 exhibited enhanced photocatalytic activity on photodecomposition of phenol in aqueous solution under visible light irradiation comparing to that of pure TiO2. According to photoelectrochemical response property and theoretical calculation of energy levels, two possible energy matching modes and photoelectron transmission pathways were proposed to explain the effects of Fe-HQS and Er-HQS on the interfacial interaction between metal-HQS complex and TiO2, and their different photocatalytic activities under visible light irradiation. The work in this paper indicated that metal-HQS complex with appropriate electronic structure and HOMO-LUMO energy levels relative to the band gap of TiO2 played a major role in improving TiO2 photocatalytic activity.

Theoretical calculation of energy levels of Pb III

In this paper, the results of theoretical calculation of five Rydberg series energy levels 5d_{3/2} \to np_{1/2} (n=6--20), 5d_{3/2} \to nf_{5/2} (n=5--20), 5d_{5/2} \to np_{3/2} (n=6--20), 5d_{5/2} \to nf_{7/2} (n=5-20) and 5d_{5/2} \to nf_{5/2} (n=5-20) for Pb III ions are presented using the weakest bound electron potential model (WBEPM) theory, considering foreign level perturbation corrections. The theoretically calculated results agree very well with present known experimental data, and some energy levels without experimental values are predicted.

Spin‐Coated Highly Efficient Phosphorescent Organic Light‐Emitting Diodes Based on Bipolar Triphenylamine‐Benzimidazole Derivatives

AbstractA new series of star‐shaped bipolar host molecules, tris(4′‐(1‐phenyl‐1H‐benzimidazol‐2‐yl)biphen‐yl‐4‐yl) amine (TIBN), tris(2′‐methyl‐4′‐(1‐phenyl‐1H‐benzimida zol‐2‐yl)biphenyl‐4‐yl)amine (Me‐TIBN), and tris(2,2′‐dimethyl‐4′‐(1‐phenyl‐1H‐benzimidazol‐2‐yl)biphenyl‐4‐yl)amine (DM‐TIBN), that contain hole‐transporting triphenylamine and electron‐transporting benzimidazole moieties are designed based on calculations using density functional theory and successfully prepared. The theoretical calculation of energy levels of TIBN derivatives affords helpful ideas to design molecules with a favorable localization of highest occupied/lowest unoccupied molecular orbital (HOMO/LUMO) levels and a predefined enhancement of the triplet energy gap. The TIBN derivatives are employed as hosts to fabricate phosphorescent organic light‐emitting diodes (OLEDs) by the two methods of spin‐coating and vacuum deposition. Notably, the spin‐coated Me‐TIBN and DM‐TIBN devices exhibit a much better performance than the vacuum‐deposited ones, in which the spin‐coated DM‐TIBN device (47 500 cd m−2, 27.3 cd A−1, 7.3 lm W−1) is outstanding with respect to other seminal work for solution‐processed OLEDs. More importantly, the new concept of localizing HOMO and LUMO levels for bipolar molecules is illustrated, and a facile strategy to tailor the energy levels by breaking the conjugation of hole‐ and electron‐transporting moieties is demonstrated.

Cover Picture: Novel Three Dimensional Cubic Fm3m Mesoporous Aluminosilicates with Tailored Cage Type Pore Structure and High Aluminum Content (Adv. Funct. Mater. 4/2008)

AbstractCover:3D cubic Fm3m mesoporous aluminosilicates (AlKIT‐5) with very high structural order and unprecedented loadings of Al in the silica framework are reported by Ajayan Vinu and co‐workers on p. 640. The specific surface area, specific pore volume, and pore diameter of AlKIT‐5 can be increased by increasing Al incorporation in the silica framework while retaining the well‐ordered 3D cage‐type porous structure. The mechanism of this unusual behavior is discussed in detail. In a catalytic activity study, AlKIT‐5(10) is found to be superior over zeolite catalysts including ZSM‐5.Organic Light‐Emitting DiodesA new series of star‐shaped bipolar host molecules thatcontain hole‐transporting triphenylamine andelectron‐transporting benzimidazole moieties are designed,based on calculations using density functional theory, and prepared by Masa‐aki Kakimoto and co‐workers, as reportedon p. 584. The theoretical calculation of energy levels affords helpful ideas to design molecules with a favorable localization of HOMO/LUMO levels and a predefined enhancement ofthe triplet energy gap. The derivatives are employed as hosts to fabricate phosphorescent organic LEDs by spin‐coating and vacuum deposition.Magnetic MaterialsSeveral nanoscale technological applications rely on the promise of highly anisotropic magnetic materials. Verónica Salgueirin˜o‐Maceira, Miguel A. Correa‐Duarte, andco‐workers report on p. 616 the structure, magnetic properties, and interfacial exchange anisotropy effects of unique wires of Ni/NiO synthesized using carbon nanotubes as substrates.Structural analyses of these nanocomposites in correlation withmagnetic measurements show that the crystalline NiO outershells cause an enhanced exchange bias, providing an extra source of anisotropy that leads to their magnetization stability.Crosslinked NanoparticlesAn amphiphilic block copolymer is synthesized by RAFTp olymerization and then assembled into micelles in aqueoussolution. Subsequent crosslinking throughout the shell affordswell‐defined nanoparticles. In an attempt to narrow the particlesize distributions, the dodecyl trithiocarbonate chain end of theblock copolymer was replaced by a 2‐cyanoisopropyl moiety.The primary advantages of this system include the ability to conduct in situ synthesis of nanoparticles that are crosslinkeddirectly and derivatized easily before, during, or after the crosslinking, as demonstrated by Karen L. Wooley and co‐workers on p. 551.

Theoretical calculation of energy levels of Sr I

In this paper, results of theoretical calculation of energy levels for the [Kr] 4d3/2nd3/2 (J= 1), [Kr] 4d3/2ng7/2 (J= 2), [Kr] 4d5/2ng9/2 (J=2), [Kr] 4d5/2ng7/2 (J=2), [Kr] 4d5/2ns1/2 (J=2) and [Kr] 4d5/2nd5/2 (J=1) series of doubly excited atom Sr are presented using the weakest bound electron potential model (WBEPM) theory. The comparison of the results with the perturbations and those without the perturbations shows that the effect of proper foreign levels is important in the calculation of energy levels, so we think perturbations of foreign levels should be taken into account in the calculation of doubly excited states of Sr I. The accuracy of most of our results is better than 1 cm−1 with few of them being more than 1 cm−1. Therefore, we can say that the WBEPM theory is an efficient one for calculating energy levels of doubly excited Sr I.

Theoretical Investigation of the Electronic Structure of Ferroelectric SbSBr Molecular Cluster

This paper presents the theoretical calculation of energy levels of the valence bands and bond orders of the SbSBr single crystals using the molecular cluster model consisting twenty SbSBr molecules. The theoretical calculation revealed that the ferroelectric phase transition changes the bond orders and shift valence bands. Results of theoretical calculations of averaged total density of states of SbSBr molecular cluster are compared with the experimentally results of X-ray photoelectron spectroscopy (XPS) of SbSI crystals, because that SbSI and SbSBr crystals have isomorphic electronic structure.

Photoluminescence and magnetophotoluminescence of circular and elliptical InAs/GaAs quantum dots

Photoluminescence, magnetophotoluminescence, and atomic force microscopy were used for the characterization of MOVPE prepared InAs/GaAs quantum dots. Significant differences in the behaviour of the first excited photoluminescence transition in magnetic field are explained by the different lateral shape of quantum dots. While the first excited luminescence peak of circular quantum dots splits with increasing magnetic field into two peaks, no splitting occurs for quantum dots with elliptic shape, only small red shift is observed. Theoretical calculations of energy levels in InAs/GaAs quantum dots with circular and elliptical shape with different elongations are presented and compared with experimental results.

Strained Si—O—Si Bonds in Amorphous SiO2 Materials: A Family Member of Active Centers in Radio, Photo, and Chemical Responses

AbstractFor Abstract see ChemInform Abstract in Full Text.

Strained Si–O–Si bonds in amorphous SiO2 materials: A family member of active centers in radio, photo, and chemical responses

Amorphous SiO2 (a-SiO2), such as bulk silica glasses and thin films has been one of the key materials in modern optoelectronic industries. These materials are currently used in communication technologies as optical fibers, thin films for electrical insulation in dynamic random access memories (DRAM), and optical lenses for excimer laser lithography, for example. The property essential for these applications is the wide band gap amounting to ∼9 eV. However, bulk silica glasses commercially available and silica thin films show photoresponses to subband gap lights in the vicinity of 5 eV and unexpected trapping of charges, and the behavior has a strong dependency on the preparation history. A number of studies were carried out to clarify the relationship between the properties and structural imperfections in the materials and the formation mechanisms of the defects. There are two categories of the imperfections: one is dopant- or impurity-related imperfections and the other is nonstoichiometry related defects. These defects constitute gap states in a-SiO2. The structural identification was usually performed by absorption and emission spectroscopy in the visible–ultraviolet (UV) region and electron spin resonance (ESR). The experimentally proposed models were compared with the predictions by theoretical calculations of energy levels. Recent development of the excimer laser lithography technique led us to recognize that a latent member, which has been unnoticed because of no response to the optical absorption or emission in the visible-UV range and ESR absorption, exists in the family of active centers in a-SiO2, that is a strained Si–O–Si bond originating from the planar three membered ring. In contrast, the puckered four membered ring is unstrained. Although it has been pointed out that there was a wide distribution in Si–O–Si bond angle from 90° to 180° by x-ray analysis or Si29 solid state nuclear magnetic resonance, the physical, and chemical responses of the Si–O–Si bonds with a particular bond angle could not be differentiated. Very recently it was clarified that a strained Si–O–Si bond, in other words chemically excited bonds, has an optical absorption locating on the band edge. The chemically excited bond can be scavenged by fluorine doping, because it is chemically reactive. In the present review we show that the unresolved optical and electric responses of silica glasses can be comprehensively understood by taking the presence of the strained bonds into consideration.

Spectroscopy of Pd-like Ions

Ions of the Pd-like isoelectronic sequence, as in the Ni-like sequence, are currently interesting for the development of X-UV lasers. Spectra of this sequence were extensively studied in a joint project at Troitsk, Orsay and Meudon. A review is given of the experimental results for the Cs X–Ce XIII ions obtained with the aid of high resolution spectrographs as well as with theoretical calculations of energy levels and transition probabilities made by the Cowan code or by fitting with orthogonal operator techniques.

シリカガラスの光学的性質に影響を与える構造欠陥

Amorphous SiO2 such as bulk silica glasses and thin films have been one of key materials in modern optoelectronic industries. They are currently used in communication technologies as an optical fiber, fiber grating and fiber amplifier, thin films for electrical insulation in the dynamic random access memory (DRAM), and optical lenses and photo-masks in the excimer laser lithography. The property essential for the applications is its wide band gap amounting ∼9eV. However, bulk silica glasses commercially available and silica thin films do show photo-responses to sub-band gap lights like KrF emission and unexpected trapping of charges, and the behavior has strong dependency on the preparation histoty. A great number of studies were carried out to clarify the relation between the properties and structural imperfections in the materials and formation mechanisms of the defects. There are two categories of the imperfections: one is dopant- or impurity-related imperfections and another is non-stoichiometry related defects. These defects constitute gap states in a-SiO2. The structural identification was usually done by absorption- and emission-spectroscopy in visible-ultraviolet region and electron spin resonance (ESR). The experimentally proposed models were compared with the predictions by theoretical calculation of energy levels. Recent development of excimer laser lithography technique led us to recognition that a latent member, which has been unnoticed because of no response to the optical absorption or emission in the visible-uv range and ESR absorption, exists in the family of active centers in a-SiO2, that is a strained Si-O-Si bond originated from the planar three membered ring. In contrast, the puckered four membered ring is unstrained. Although it has been pointed out that there was a wide distribution in Si-O-Si bond angle from 90° to 180° by X-ray analysis or 29Si solid state NMR, the physical and chemical responses of the Si-O-Si bonds with a particular bond angle could not be differrentiated. Very recently it was clarified that a strained Si-O-Si bonds, in other words chemically excited bonds, has an optical absorption locating on the band edge. The excited bond can be scavenged by fluorine doping, because it is chemically reactive. In the present review we hope to show the unresolved optical and electric responses of silica glasses can be comprehensively understood by taking the presence of the strained bonds into consideration.

Theoretical Calculation of Energy Levels of a Hydrogen Atom in a Strong Magnetic Field

The eleven low-lying energy levels of a hydrogen atom, and its mean radius in a uniformly high magnetic field are calculated in a simple variational approach. The potential term containing squared magnetic field in Hamiltonian operator is separated into spherically and nonspherically symmetric potentials. The influence over levels and radius of the hydrogen atom is discussed. The results are in good agreement with the recent literatures, but more accurate. We find that the stronger the magnetic field is, the smaller the mean radius of the hydrogen atom is.

Dynamics of metastable-atom deexcitation at metal surfaces.

Theoretical calculations of energy levels and widths are presented that indicate that He(${2}^{3}$S) atoms are sufficiently long lived near a metal surface that a significant fraction of the excited atoms contained in a thermal-energy beam can survive passage to within \ensuremath{\sim}3--4 \AA{} of the surface, where, it is suggested, Auger deexcitation might compete effectively with resonance ionization. This might account for earlier observations that electrons ejected from high-work-function metal surfaces by electron-spin-polarized He(${2}^{3}$S) metastable atoms have a significant spin polarization.

Ar L-MM Auger spectra in energetic Ar4++Ar collisions

Energy distributions of electrons produced in 6.6-45.7 MeV Ar4+ impact on Ar have been measured in the energy range from 80 to 330 eV. A number of Auger lines have been observed in the energy range from 100 to 200 eV, which are attributable to L-MM Auger electrons from target Ar atoms with highly ionised M shells. The identification of these lines has been based on the dependence of their intensities on the projectile energy and on theoretical calculations of energy levels of highly ionised Ar atoms. Some relatively weak peaks representing double L-shell vacancy production have also been observed. In addition, the spectra show a trace of L1-MM Auger lines from multiply ionised Ar targets.

Crystal-field splitting in dysprosium ethyl sulphate-an infrared and theoretical investigation

A detailed experimental study in the near infrared has been made of the low-lying excited states of Dy3+ in the ethyl sulphate lattice. The results, which were obtained using different forms of polarised light and the technique of magnetic circular dichroism, show significant differences from the earlier work on this system. Theoretical calculations of energy levels and g-values that include the effects of intermediate coupling and J-mixing have been made. A very satisfactory agreement between theory and experiment is found for the lower 6H11/2 manifold when using published crystal-field parameters derived to fit the experimental data on the ground state. Making some changes in these parameters yields an even closer fit.

Luminescence of the Pb2+‐Ion Dimer Center in CaS and CaSe Phosphors

AbstractReflection, emission, and excitation spectra of CaS:Pb2+ and CaSe:Pb2+ are measured at 300, 80, and 6K. At higher concentrations of Pb2+ ions, the emission and exeitation bands due to the Pb2+ dimer are observed besides those of the Pb2+ monomer. Theoretical calculation of energy levels of the dimer of Tl+‐type ions is made on the basis of the localized electron model. The values of the spectroscopic parameters appearing in the energy matrices are determined so that the electronic levels obtained experimentally and theoretically may coincide with each other.