Red-shift Phenomenon Research Articles

Effect of different doping ratios of Mo doping and Zn vacancy on magneto-optical properties of ZnO

The source of ZnO magnetism in Mo doping and Zn vacancy is not fully understood. Generalized gradient approximate plane wave ultrasoft pseudopotential method was adopted based on the spin density functional theory to solve this problem. The structural stability and magneto-optical properties of Mo doping and Zn vacancy in co-existing ZnO were calculated using the first principle. The band gap of the doping system is narrower than that of the pure ZnO, and the absorption spectrum showed a red shift in the visible light range of 380–600 nm. The Zn34MoO36 had the strongest absorption spectrum intensity, the most significant red shift phenomenon, the easiest electron and hole separation, and the strongest photocatalytic activity. These features are beneficial to the design and preparation of new photocatalysts. When Mo to Zn vacancy ratio of 2:2, the Zn32Mo2O36 has the strongest magnetic properties, and the electron spin polarization was 100%, which is advantageous for designing and preparing the dilute magnetic semiconductors. The Zn32Mo2O36 has shown room temperature ferromagnetism, and the magnetism of the Zn32Mo2O36 came from the hole produced by Zn vacancy. Double exchange interaction occurred between non-pairing itinerant electron in the O–2P orbit near the Zn vacancy and the spin polarization of electrons in Mo-4d orbitals with the hole as a medium. This is consistent with the mean field approximation and the double exchange mechanism theory.

A New Understanding of the Origin of Wave-Particle Duality in Quantum Mechanics

The wave-particle duality of quantum mechanics has always been an unsolved problem in physics. This article attempts to use one of the properties to explain the other, so as to eliminate the confusion of quantum mechanics probability waves. Specifically, this article finds that the discreteness of energy is the inherent property of all waves, so this article explains the particle nature of light from the perspective of light wave, thereby eliminating the confusion of light’s wave-particle duality; in addition, this article found that microscopic matter particles are only suitable for discussing the number of scattered particles or energy flow density, not their position and momentum, when they are forced to discuss their position and momentum, it will inevitably lead to confusion about probability waves, when only discussing the number of scattered particles or energy flow density, its volatility can be explained from the perspective of particle nature, thereby eliminating the confusion of microscopic matter particle probability waves. When the attribute of light as a wave is established, the light needs to overcome the Hamiltonian of the medium in different constraint systems (gravitational fields) during the propagation process, which will produce a universal redshift phenomenon, this can provide a new understanding of cosmic redshift; when the property of light as a wave is established, it means that the speed of light is a constant speed relative to the medium, which can provide a new understanding of the principle of constant speed of light.

Structure and functional properties of sunflower seed protein as affected by enzymatic hydrolysis combined with macroporous resin adsorption decolorization

ABSTRACT In order to improve the color and functional properties of sunflower seed protein, low-temperature defatted sunflower seed meal was used as the raw material to study the effects of limited enzyme hydrolysis combined with macroporous resin adsorption decolorization technology on the color and functional properties of sunflower seed protein. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD), particle size, intrinsic fluorescence intensity, surface hydrophobicity (H0) and scanning electron microscopy (SEM) were used to analyze the influence on its structure. The results showed that the molecular weight of sunflower seed protein was reduced after limited enzyme hydrolysis combined with macroporous resin decolorization; the content of α-helix and β-turn was significantly reduced, and the content of β-sheets and random coils was significantly increased; the average particle size was reduced; the fluorescence intensity was increased and the red shift phenomenon occurred. H0 also increased, SEM results showed that the surface of sunflower seed protein changed from a smooth large sheet-like structure to an irregular fragmented fast-like structure. Solubility, foamability, emulsification and emulsification stability were all significantly improved (p < .05), while foam stability and oil retention were reduced. The above results indicate that limited enzyme hydrolysis combined with macroporous resin adsorption and decolorization changes the structure of sunflower seed protein, and then improve its functional properties.

Regulating electronic properties of BiOBr to enhance visible light response via 3d transition metals doping: DFT + U calculations

AbstractIn our work, the formation energies, band structures, densities of states, effective masses and optical absorption properties of pure BiOBr and 3d transition metals‐doped BiOBr have been calculated using DFT + U method. Ti, V, Fe, Cr, Co, Ni and Cu doping can induce impurity energy levels, originating from spin‐up or ‐down orbits of 3d transition metals (TMs), within the forbidden band of BiOBr, but Sc, Mn and Zn atoms only change the electronic delocalization in the valence band or conduction band region of BiOBr. Furthermore, with introduction of 3d TMs atoms, there exist the redshift phenomena for optical absorption band edge of BiOBr to different extents. The photo response priority order, structural stability and recombination probability of photoinduced carriers for 3d TMs‐doped BiOBr are summarized. Our theoretical findings should well explain the experimental observations in the previous literatures, and provide promising prediction and significant guidance for the well‐construction of BiOBr‐based photocatalyst systems.

First principles study on copper and iridium co-doped SrTiO3 for shifting the optical absorption into visible region

Density functional theory (DFT) investigation is performed to observe the opto-electronic properties of iridium and copper co-doped structure of Pristine SrTiO3 (Cubic Perovskite). Results suggest that copper and iridium co-doped structure of SrTiO3 has significant absorption in visible region of the spectrum, which is a result of red shift phenomenon in the wavelength range 400–750 nm observed in this structure. However, in individual copper and iridium structures the optical absorption is mainly in ultraviolet (UV) region which limits its use in light-based devices and applications. The shift in absorption from UV to visible region in the co-doped structure extracts the maximum utilization of solar light and finds wide range of optical applications like solar cells. Refractive index and dielectric constants were also calculated and their peak values were found to be in correlation with the peaks in absorption spectrum.

Enhanced fluorescence of Zn-doped carbon quantum dots using zinc citrate chelate as precursor for fluorescent sensor applications

The Zn2+ doped Carbon Quantum Dots (Zn-CQDs) were synthesized with zinc citrate chelate as the precursor by a hydrothermal method. The evaluation results indicated that Zn2+ was successfully embedded in CQDs. Most of Zn2+ ions were combined with carboxyl groups on the surface of carbon dots to form Zn-O bonds and some Zn2+ ions were embedded in the interstice points of CQDs. The remaining Zn2+ were reduced to zinc atoms and adsorbed on the surface of CQDs. With the increase in Zn2+ concentration, the size of synthesized Zn-CQDs increased. When zinc ion concentration increased to 9%, the average size of Zn-CQDs grew up to 8 nm, but the size of undoped CQDs was just 1.5 nm. When Zn2+ concentration increased from 1% to 9%, the fluorescence intensity increased, while reaching above 9%, the fluorescence intensity showed a downward trend. When Zn2+ concentration was 7%, the fluorescence quantum yield of Zn-CQDs increased to 48%, but the fluorescence quantum yield of undoped CQDs was only 37%. With the increase in Zn2+ concentration, the PL spectrum of Zn-CQDs showed a red shift phenomenon. In addition, Zn-CQDs showed superior fluorescent sensing capability to Fe3+ and Hg2+, presenting greater fluorescence quenching effect on Fe3+ and Hg2+ than CA-CQDs. Therefore, Zn-CQDs demonstrated excellent fluorescence properties and can be applied in fluorescent sensor, biological imaging, optoelectronics, and catalysis fields.

Coexistence of circular dichroism and asymmetric transmission in a stretchable chiral metamaterial

A stretchable chiral metamaterial with Au nanoslits and L-shaped and T-shaped Au patterns (SCMM-NLT), which can simultaneously produce circular dichroism (CD) and asymmetric transmission (AT) effects for circularly polarized waves in the mid-infrared region, is proposed. The peak values of CD and AT effects reach 20.4% and − 20.4 % at the resonance wavelength of 23.4 µm, respectively, which originate from the excitation of the bonding and antibonding modes. We use the transmission matrix to analyze the simultaneous appearance of CD and AT effects. By stretching SCMM-NLT, the bands of CD and AT occur at the redshift phenomenon, which is attributed to the decrease of Coulomb force between the positive and negative charge accumulated at both ends of the structure. All results are calculated by the FEM-based software COMSOL Multiphysics. In the future, our findings could be applied to wearable electronic devices, such as refractive index sensors.

Monoclonal antibody stability can be usefully monitored using the excitation-energy-dependent fluorescence edge-shift.

Among the major challenges in the development of biopharmaceuticals are structural heterogeneity and aggregation. The development of a successful therapeutic monoclonal antibody (mAb) requires both a highly active and also stable molecule. Whilst a range of experimental (biophysical) approaches exist to track changes in stability of proteins, routine prediction of stability remains challenging. The fluorescence red edge excitation shift (REES) phenomenon is sensitive to a range of changes in protein structure. Based on recent work, we have found that quantifying the REES effect is extremely sensitive to changes in protein conformational state and dynamics. Given the extreme sensitivity, potentially this tool could provide a ‘fingerprint’ of the structure and stability of a protein. Such a tool would be useful in the discovery and development of biopharamceuticals and so we have explored our hypothesis with a panel of therapeutic mAbs. We demonstrate that the quantified REES data show remarkable sensitivity, being able to discern between structurally identical antibodies and showing sensitivity to unfolding and aggregation. The approach works across a broad concentration range (µg–mg/ml) and is highly consistent. We show that the approach can be applied alongside traditional characterisation testing within the context of a forced degradation study (FDS). Most importantly, we demonstrate the approach is able to predict the stability of mAbs both in the short (hours), medium (days) and long-term (months). The quantified REES data will find immediate use in the biopharmaceutical industry in quality assurance, formulation and development. The approach benefits from low technical complexity, is rapid and uses instrumentation which exists in most biochemistry laboratories without modification.

Theoretical investigation of the photocatalytic mechanism of single Au adsorption on the Bi4O5Br2 (−1 0 1) surface

First-principle calculation based on DFT is performed to explore the structural, electronic, optical properties and photocatalytic mechanism of monatomic Au/Bi4O5Br2 adsorption systems. The results indicate that Au/Bi4O5Br2 adsorption systems not only possess excellent structural stability and appropriate band structure, but also exhibit excellent photon-excited carriers generation efficiency. The optical absorption is strengthened and performs significant phenomenon of redshift. The modification method through monatomic Au absorption causes the charge redistribution of the Bi4O5Br2 (−101) surface, achieving the effective spatial separation of the oxidation center and the reduction center. This significantly improve separation efficiency of the photo-excited electrons and holes. These characters make the Au/ Bi4O5Br2 adsorption system an excellent photocatalyst.

Study on optical discoloration of a material surface and its optical mechanism

The deterioration of material surface is one of the most important problems in decorative materials. Most of the materials are caused by changes in their surface chemical composition. However, the PVC veneers used for decoration are different. Using XPS and other surface analysis instruments, the mechanism of the color change of PVC patches is studied. According to the analysis results of the color change and the relatively stable chemical structure before and after the irradiation, starting from the mechanism of the color formation of the object, the main cause of its discoloration is physical factors, which is analyzed and explained by the diffraction theory in physical optics. Finally, a simulation experiment is carried out to verify the theoretical explanation proposed in this study. The results show that the reason for the deterioration of the PVC surface is the physical factor (the diffraction of light) dominates. The smoothness of the coating on the material surface will directly affect the visual effect, and the redshift phenomenon will occur with the increase of roughness.

Oscillation characterization of volatile combustion of single coal particles with multi-species optical diagnostic techniques

This paper investigated the oscillation characterization of volatile combustion of single coal particles using high-speed OH-PLIF and CH* chemiluminescence, meanwhile advanced data-driven algorithm as post-processing. The measurement region of in-situ 500 Hz OH-PLIF system was set to 53mm × 35 mm with a spatial resolution of ~23 µm per pixel, which was used to capture the continuous and whole volatile combustion process of single particle in a group of pulverized coal particles (SPGCP). A high-volatiles bituminous coal (30 wt%) burned at a gas temperature of 1700 K with oxygen mole fractions in the range of 10%–30%. The morphology of volatile flame and dynamic evolution was obtained. Dynamic mode decomposition (DMD) method can provide a new insight into combustion oscillation of pulverized coal. The oscillation frequency characteristics of pulverized coal flame were captured, and the red-shift phenomenon of dominant frequency with the increase of oxygen concentration was found. The particle aggregation might lead the low-frequency oscillation of pulverized coal combustion. On the contrary, individual or separated particle combustion could generate larger oscillation frequency.

Enhanced luminescence performances of Mn4+-activated Sr4Al14O25 red phosphors by doping with Sc3+ ions

A series of non-rare earth Mn4+-activated strontium aluminate phosphors Sr4Al14O25:Mn4+ co-doped with Sc3+ ions were successfully synthesized by a high-temperature solid-state reaction method. XRD result reveals that there is no introduction of additional phase but expansion of lattice with incorporation of Sc3+ ions. Excitation and emission spectrum measurement shows that the synthesized phosphors can be efficiently excited by near-ultraviolet and blue light, and a deep red emission centered at 652 nm with a narrow full width at half maximum (FWHM) can be obtained, which is attributed to the transition 2E→4A2 of Mn4+ ions. In addition, the crystal field strength parameter (Dq) and Racah parameters (B, C) and energies of states were calculated based on experimental data. Moreover, the luminous intensity of Sr4Al14-xScxO25:Mn4+ is enhanced and increased by 60% compared with Mn4+ single incorporated sample at x = 0.06. A phenomenon of redshift is observed in the excitation spectrum and discussed systematically. Finally, the mechanism of the positive effects with Sc3+ ions incorporated into lattice is discussed in detail. All the results suggest that the Sr4Al13.94Sc0.06O25:Mn4+ phosphor will become one of the great candidates for backlight of LCD.

Fabrication of Ultraviolet Photodetectors Based on Fe-Doped ZnO Nanorod Structures.

In this paper, 100 nm-thick zinc oxide (ZnO) films were deposited as a seed layer on Corning glass substrates via a radio frequency (RF) magnetron sputtering technique, and vertical well-aligned Fe-doped ZnO (FZO) nanorod (NR) arrays were then grown on the seed layer-coated substrates via a low-temperature solution method. FZO NR arrays were annealed at 600 °C and characterized by using field emission scanning microscopy (FE-SEM) and X-ray diffraction spectrum (XRD) analysis. FZO NRs grew along the preferred (002) orientation with good crystal quality and hexagonal wurtzite structure. The main ultraviolet (UV) peak of 378 nm exhibited a red-shifted phenomenon with Fe-doping by photoluminescence (PL) emission. Furthermore, FZO photodetectors (PDs) based on metal–semiconductor–metal (MSM) structure were successfully manufactured through a photolithography procedure for UV detection. Results revealed that compared with pure ZnO NRs, FZO NRs exhibited a remarkable photosensitivity for UV PD applications and a fast rise/decay time. The sensitivities of prepared pure ZnO and FZO PDs were 43.1, and 471.1 for a 3 V applied bias and 380 nm UV illumination, respectively.

Bending deformation regulates the electronic and optical properties of black phosphorene

The electronic and optical properties of black phosphorene with different bent angle are studied using density functional theory based on the first-principles. Within the scope of our study, it was found that the phosphorene becomes less stable with the increasement of bending deformation. Bending deformation has great impact on the electronic and optical properties on phosphorene. The bandgap degrades a little at [Formula: see text] bent angle, and then increases when the bent angle does not surpass [Formula: see text], after which the bandgap decreases with the increasement of bending deformation. Besides, the bandgap of black phosphorene occurs a direct to indirect transition at [Formula: see text] bent angle. The bandgap calculated by HSE06 is larger than PBE functional, but the law of changes is consistent. By analyzing the density of states, we concluded that all the undeformed and deformed phosphorene structures have a strong sp orbital hybridization. Besides, the p orbits have narrower gap than s orbits, which causes the narrower bandgaps of these structures. From the analysis of optical properties, we concluded that the black phosphorene with [Formula: see text] bent angle has the highest absorption coefficient. All structures under bending deformation have higher reflectivity peak than intrinsic black phosphorene, among these structures, the black phosphorene with [Formula: see text] bent angle has the highest reflectivity. The novel optical property is observed at the [Formula: see text] deformed structure, it stops absorbing (reflecting) light first. Redshift and blueshift phenomena are observed at the highest absorption peak and reflectivity peak.

Improving the magnetic, electronic and optical properties of the monolayer WSe2 via Mn-X (X = O, S, Se or Te) codoping

The structural, magnetic, electronic and optical properties of the pure and Mn-X (X = O, S, Se or Te) codoped monolayer WSe2 systems are quantitatively examined through first-principles calculations. The lower formation energy under Se-rich condition shows that the codoped systems under Se-rich condition is more stable than W-rich condition, especially the Mn-O codoping is the most stable with the minimum formation energy -2.08 eV. Although the pure monolayer WSe2 is a nonmagnetic semiconductor, the codoped systems are all magnetic with total magnetic moments of 1.00 µB due to the introduced one unpaired electron. It is worth mentioning that the Mn-Se and Mn-Te codoping make the monolayer WSe2 display magnetic half-metallic properties. Finally, the optical properties of the pure and codoped monolayer WSe2 are studied in x (parallel to the WSe2 plane) and z (perpendicular to the WSe2 plane) directions. An interesting red-shift phenomenon has been observed in the curves of imaginary part of the dielectric function and absorption spectra for the Mn-X codoping, suggesting their quite promising applications in optoelectronic devices.

Ultrasound for pectinase modification: an investigation into potential mechanisms.

Today, ultrasound is increasingly utilized in enzyme modification. Strongly dependent on the specific operational conditions, the modification effect brought by ultrasound can be activation and inactivation of enzymes. This work aims to study the ultrasound mechanisms under different conditions, to investigate the respective roles of free radical effect and mechanical effect in pectinase activation and inactivation, and to reveal the influence of pectinase concentration on the ultrasound-modification effect. When ultrasound was introduced to a liquid system, generation of free radicals was positively correlated with ultrasound intensity and treatment duration, but negatively correlated with temperature. Thiourea with a concentration of 4 mmol L-1 was selected as a free radical scavenger to effectively shield ultrasound free radicals. The highest enzyme activity of pectinase solutions at 0.1, 1.0, and 10.0 mg mL-1 was obtained at the same ultrasound intensity of 4.50 W mL-1 and time of 15 min, where the enzyme activity was increased by 68.24%, 20.98% and 18.83%, respectively. Furthermore, the addition of thiourea enhanced the enzyme activity at each tested ultrasound intensity and time, especially those exceeding the best conditions; it also eliminated the redshift phenomenon that was previously presented in the fluorescence spectra of pectinase samples. Pectinase concentrations did not change the optimum ultrasound conditions for enzyme modification, but pectinase with a low concentration was more vulnerable to ultrasound treatment. During modification, ultrasound mechanical effects dominated in the pectinase activation, while free radical effects dominated in the inactivation process. © 2020 Society of Chemical Industry.

Modulating the electronic, magnetic and optical properties of 1T-SnSe2 monolayer by defects: An ab initio study

We investigate the effect of vacancies and doping on the electronic, magnetic and optical properties of 1T-SnSe2 monolayer by using density functional theory calculations. The results reveal that the semiconducting 1T-SnSe2 monolayer becomes a half-metal on creating one tin vacancy (V1Sn), while it is still a semiconducting on creating one selenium vacancy (V1Se), two selenium vacancy (V2Se), as well as one tin and one selenium vacancy (V1Sn+1Se). The V1Sn and V1Sn+1Se vacancies induce magnetic ground states with net magnetic moments of 4 and 2 μB respectively, while the V1Se and V2Se vacancies induce nonmagnetic ground states. In Mo-doped 1T-SnSe2 monolayer, crystal-field splitting of Mo-4d orbital in the octahedral environment induces net magnetic moment of 2 μB. The band structure and density of states also show that the Mo-doped system is a magnetic semiconductor. In addition, the defective 1T-SnSe2 mononlayer can also enhanced the absorption efficiency of the solar energy, particularly in the infrared region. An interesting red-shift phenomenon has been observed in the curves of imaginary part of the dielectric function and absorption spectra for the defect systems, suggesting their quite promising applications in optoelectronic devices.

First-principles investigations of the effect of V and Fe dopants on the magnetic and optical properties of 4H-SiC

The effect of (V, Fe) co-doped 4H-SiC on the magnetic and optical property has been investigated by using the density functional theory approach within the generalized gradient approximation plus Hubbard U term. Comparing with the pure 4H-SiC, we can find that V mono-doped 4H-SiC can induce a total magnetic moment of 2.03 μB, and Fe mono-doped 4H-SiC can induce a total magnetic moment of 3.97 μB. Further, we also find that the system of (V, Fe) co-doped 4H-SiC can induce a total magnetic moment with the value of 6.01 μB, and its ferromagnetic state is more stable than its antiferromagnetic state with a relative energy of −424.60 meV. Finally, we introduce a carbon vacancy to the system of (V, Fe) co-doped 4H-SiC, the results show that the ferromagnetic state will be enhanced. Due to the introduction of V and Fe atoms, red-shift phenomenon appears in the absorption spectrum, and the absorption strength in visible light has been largely enhanced. The results show that the system of the (V, Fe) co-doped 4H-SiC will provide a promising approach for the development of spintronic devices and optical application in the future.

Luminescence properties of nitrogen-rich Ca-SiAlON:Eu2+ phosphors prepared by freeze-drying assisted combustion synthesis

Nitrogen-rich Eu2+-doped Ca-α-SiAlON phosphors (Cam/2−xSi12−m−nAlm+nOnN16−n:xEu) were synthesized by a freeze-drying assisted combustion synthesis (CS) route. Fast-synthesized products with high purity and uniform particle morphology were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The analysis of lattice parameters by comparison with empirical equations showed that the as-prepared phosphors had low oxygen content. A series of samples were prepared according to the stoichiometry of Cam/2−0.08Si12−mAlmN16:0.08Eu for further research. The influences of m value on the luminescence properties were investigated in detail. As m increased, a redshift phenomenon was observed in both the excitation and emission spectra. First-principle electronic structure calculations showed that the 3d energy level of Ca played an important role in the occurrence of the redshift phenomenon.

Role of the intermolecular hydrogen bond in microsolvated of a kind of PRODAN derivative with methanol on excited state

The role of intermolecular hydrogen bond of PRODAN derivative is investigated based on density functional theory (DFT) and time-dependent density functional theory (TDDFT). Geometry analysis demonstrated that the intermolecular hydrogen bonds are enhanced in S1 state. The red-shift phenomenon of fluorescence spectrum and IR spectrum as well as the energy of intermolecular hydrogen bond further confirm the intermolecular hydrogen bond strengthening in excited state. PRODAN-3a-MeOH has been electronically excited to S1 which is a local excitation. The small change of electron density occurred the interaction region of intermolecular can directly influence the intermolecular hydrogen bonding in S1 state.