Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure.Superalkalis have low ionization energy.Doping a superalkali in cyclo[18]carbon is an ef...Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure.Superalkalis have low ionization energy.Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs.In this paper,the geometry,bonding properties,electronic structure,absorption spectrum,and nonlinear optical(NLO)properties of superalkaline M_(3)O(M=Li,Na)-doped cyclo[18]carbon were studied by using density functional theory.M_(3)O and the C_(18) rings are not coplanar.The C_(18) ring still exhibits alternating long and short bonds.The charge transfer between M_(3)O and C_(18) forms stable[M_(3)O]+[C_(18)]-ionic complexes.C_(18)M_(3)O(M=Li,Na)shows striking optical nonlinearity,i.e.,their first-and second-order hyperpolarizability(βvec andγ||)increase considerably atλ=1907 nm and 1460 nm.展开更多
Structural, electronic and optical properties of Sc-based aluminum-nitride alloy have been carried out with first-principles methods using both local density approximation (LDA) and Heyd-Scuseria-Ernzerhof (HSE) hybri...Structural, electronic and optical properties of Sc-based aluminum-nitride alloy have been carried out with first-principles methods using both local density approximation (LDA) and Heyd-Scuseria-Ernzerhof (HSE) hybrid functional. This latter provides a more accurate description of the lattice parameters, enthalpy of formation, electronic and optical properties of our alloy than standard DFT. We found the transition from wurtzite to rocksalt structures at 61% of Sc concentration. By increasing the scandium concentration, the lattice parameters and the band gap decrease. The HSE band gap is in good agreement with available experimental data. The existence of the strong hybridization between Sc 3d and N 2p indicates the transport of electrons from Sc to N atoms. Besides, it is shown that the insertion of the Sc atom leads to the redshift of the optical absorption edge. The optical absorption of Sc<sub>x</sub>Al<sub>1-x</sub>N is found to decrease with increasing Sc concentrations in the low energy range. Because of this, Sc<sub>x</sub>Al<sub>1-x</sub>N have a great potential for applications in photovoltaics and photocatalysis.展开更多
Rare earth luminescent materials have attracted significant attention due to their wide-ranging applications in the field of optoelectronics. This study aims to delve into the electronic structure and optical properti...Rare earth luminescent materials have attracted significant attention due to their wide-ranging applications in the field of optoelectronics. This study aims to delve into the electronic structure and optical properties of rare earth luminescent materials, with the goal of uncovering their importance in luminescence mechanisms and applications. Through theoretical calculations and experimental methods, we conducted in-depth analyses on materials composed of various rare earth elements. Regarding electronic structure, we utilized computational techniques such as density functional theory to investigate the band structure, valence state distribution, and electronic density of states of rare earth luminescent materials. The results indicate that the electronic structural differences among different rare earth elements notably influence their luminescence performance, providing crucial clues for explaining the luminescence mechanism. In terms of optical properties, we systematically examined the material’s optical behaviors through fluorescence spectroscopy, absorption spectroscopy, and other experimental approaches. We found that rare earth luminescent materials exhibit distinct absorption and emission characteristics at different wavelengths, closely related to the transition processes of their electronic energy levels. Furthermore, we studied the influence of varying doping concentrations and impurities on the material’s optical properties. Experimental outcomes reveal that appropriate doping can effectively regulate the emission intensity and wavelength, offering greater possibilities for material applications. In summary, this study comprehensively analyzed the electronic structure and optical properties of rare earth luminescent materials, providing deep insights into understanding their luminescence mechanisms and potential value in optoelectronic applications. In the future, these research findings will serve as crucial references for the technological advancement in fields such as LEDs, lasers, and bioimaging.展开更多
Based on the density functional theory, the influences of strain on structural, elastic, thermal and optical properties of CuGaTe_2 are discussed in detail. It is found that the tensile strain on CuGaTe_2 is beneficia...Based on the density functional theory, the influences of strain on structural, elastic, thermal and optical properties of CuGaTe_2 are discussed in detail. It is found that the tensile strain on CuGaTe_2 is beneficial to the decrease of lattice thermal conductivity by reducing the mean sound velocity and Debye temperature. Moreover, all strained and unstrained CuGaTe_2 exhibit rather similar optical characters. But the tensile strain improves the ability to absorb sunlight in the visible range.These research findings can give hints for designing thermoelectric and photovoltaic devices.展开更多
Transparent conductive cadmium indium oxide films (CdIn2O4) were prepared by r.f. reactive sputtering from Cd-In alloy targets under an Ar-O2 atmosphere. Electrical conductivity of the order of 105Ω-1.m-1 and the opt...Transparent conductive cadmium indium oxide films (CdIn2O4) were prepared by r.f. reactive sputtering from Cd-In alloy targets under an Ar-O2 atmosphere. Electrical conductivity of the order of 105Ω-1.m-1 and the optical transmission as high as 94% are easily attained by postdeposition annealing treatment. The effects of oxygen concentration in the reactive gas mixture and post-deposition annealing treatment on the optical transmittance as well as optical parameters, such as refractive index (n), extinction coefficient (k), real part (ε’) and imaginary part (ε") of the dielectric constant, were studied in the visible and near-infrared region. The highfrequency dielectric constant ε∞ the plasma frequency ωP, and the conduction band effective mass mc of different samples were also展开更多
Black carbon(BC)reduces the photolysis coefficient by absorbing solar radiation,thereby affecting the concentration of ozone(O_(3))near the ground.The influence of BC on O_(3)has thus received much attention.In this s...Black carbon(BC)reduces the photolysis coefficient by absorbing solar radiation,thereby affecting the concentration of ozone(O_(3))near the ground.The influence of BC on O_(3)has thus received much attention.In this study,Mie scattering and the tropospheric Ultraviolet and Visible radiation model are used to analyze the effect of BC optical properties on radiation.Combined with data of O_(3)precursors in Nanjing in 2014,an EKMA curve is drawn,and the variations in O_(3)concentration are further investigated using a zero-dimensional box mechanism model(NCAR MM).When O_(3)precursors are unchanged,radiation and O_(3)show a highly similar tendency in response to changing BC optical properties(R=0.997).With the increase of modal radius,the attenuation of fresh BC to radiation and O_(3)first trends upward before decreasing.In the mixing process,the attenuation of BC to radiation and O_(3)presents an upward tendency with the increase of relative humidity but decreases rapidly before increasing slowly with increasing thickness of coating.In addition,mass concentration is another major factor.When the BC to PM_(2.5)ratio increases to 5%in Nanjing,the radiation decreases by approximately 0.13%-3.71%while O_(3)decreases by approximately 8.13%-13.11%.The radiative effect of BC not only reduces O_(3)concentration but also changes the EKMA curve.Compared with the NO_(x)control area,radiation has a significant influence on the VOCs control area.When aerosol optical depth(AOD)increases by 17.15%,the NO_(x)to VOCs ratio decreases by 8.27%,and part of the original NO_(x)control area is transferred to the VOCs control area.展开更多
The structural vibrational, thermodynamical, and optical properties of potentially technologically important, weakly coupled MAX compound, Sc2 Al C are calculated using density functional theory(DFT). The structural p...The structural vibrational, thermodynamical, and optical properties of potentially technologically important, weakly coupled MAX compound, Sc2 Al C are calculated using density functional theory(DFT). The structural properties of Sc_2AlC are compared with the results reported earlier. The vibrational, thermodynamical, and optical properties are theoretically estimated for the first time. The phonon dispersion curve is calculated and the dynamical stability of this compound is investigated. The optical and acoustic modes are observed clearly. We calculate the Helmholtz free energy(F), internal energy(E), entropy(S), and specific heat capacity(Cv) from the phonon density of states. Various optical parameters are also calculated. The reflectance spectrum shows that this compound has the potential to be used as an efficient solar reflector.展开更多
ZnO nano-particles were synthesized via an ammonical ammonium carbonate solution by precipitation method in presence of some additives such as urea, oleic and stearic acid. The morphology and crystallinity of the obta...ZnO nano-particles were synthesized via an ammonical ammonium carbonate solution by precipitation method in presence of some additives such as urea, oleic and stearic acid. The morphology and crystallinity of the obtained zinc oxide particles depend critically on the type of additive which was used. Additives also affected the crystal orientation of precipitate nano-particles. SEM, XRD, BET and UV-visible were used to characterize morphology, microstructure, specific surface area and optical properties of the products.Photo-catalysis properties of the as-prepared ZnO powders were evaluated by degradation of methyl red(acid red) in aqueous solution exposed to UV-light. Results suggested a close relationship among the morphology,size and surface area on photo-catalysis and optical properties of the particles. The widest Egvalue(3.56 e V),highest degradation and decolorization efficiency(99%) were obtained from a sample with the smallest grain size(largest surface area) which were used urea as an additive.展开更多
A novel fluorescent composition was firstly isolated from natural winter fresh Moso bamboo shoots,and its optical properties were fully investigated by fluorescence spectroscopy.It could emit strong blue light both in...A novel fluorescent composition was firstly isolated from natural winter fresh Moso bamboo shoots,and its optical properties were fully investigated by fluorescence spectroscopy.It could emit strong blue light both in solid and solution state,providing high fluorescence intensity in ethanol.The solution’s concentration and addition of water greatly affected the fluorescence intensity,high concentration and addition of much water could quench fluorescence.Apoptosis results showed that the fluorescent extract(0-25 mg/L)could not induce apoptosis of Hela cells.Confocal fluorescent microscopic imaging in human hepatocellular carcinoma cells(HepG2)was realized using the fluorescent extract,it could dye the whole cell well which was different from 4',6-diamidino-2-phenylindole(DAPI)only dying cell nucleus.The fluorescent extract may be candidate for future natural fluorescent bio-imaging agent.展开更多
The structure, electrical transport, and optical properties of GaSe films fabricated by means of radio-frequency (RF) magnetron sputtering in Ar were investigated. The as-sputtered GaSe films were amorphous, and their...The structure, electrical transport, and optical properties of GaSe films fabricated by means of radio-frequency (RF) magnetron sputtering in Ar were investigated. The as-sputtered GaSe films were amorphous, and their optical energy gap Eg are 1.9～2.6 eV. The effect of the synthesis conditions on the optical and electrical properties of the GaSe films has also been展开更多
Nanofluids have great potential for solar energy harvesting due to their suitable optical and thermophysical properties.One of the promising applications of nanofluids is utilization in solar collectors with the direc...Nanofluids have great potential for solar energy harvesting due to their suitable optical and thermophysical properties.One of the promising applications of nanofluids is utilization in solar collectors with the direct absorption of light(DASC).The design of a DASC requires detailed knowledge of the optical properties of nanofluids,which can be significantly affected by the particle size distribution.The paper presents the method to take into account the particle size distribution when calculating nanofluid extinction spectra.To validate the proposed model,the particle size distribution and spectral absorbance were measured for aqueous suspension with multi-walled graphite nanotubes;the minimum size of primary nanoparticles was 49 nm.The proposed model is compared with experiments demonstrating the concentration averaged and maximum discrepancies of 6.6%and 32.2%against 12.6%and 77.7%for a model assuming a monosized suspension.展开更多
In this paper we investigated the optical properties of ZnO and Mn doped ZnO nanocrystals that were fabricated by a vapor phase transport growth process, using zinc acetate dihydrate with or without Mn in a constant O...In this paper we investigated the optical properties of ZnO and Mn doped ZnO nanocrystals that were fabricated by a vapor phase transport growth process, using zinc acetate dihydrate with or without Mn in a constant O2/Ar mixture gas flowing through the furnace at 400600℃, respectively. The as grown ZnO nanocrystals are homogeneous with a mean size of 19 nm observed by scanning electron microscope（SEM）. The optical characteristics were analyzed by absorption spectra and photoluminescence（PL） spectra at room-temperature. For ZnO nanocrystals, a strong and predominant UV emission peaked at 377 nm was found in the PL spectra. For Mn doped ZnO nanocrystals, in addition to the strong UV emission, a strong blue emission peaked at 435 nm was observed as well. By doping Mn ions, the major UV emission shifts from 377 nm to 408 nm, showing that Mn ions were not only incorporated into ZnO Ncs, but also introduced an impurity level in the bandgap. Moreover, with the concentration of Mn increasing, the relative intensities of the two emissions change largely, and the photoluminescence mechanism of them is discussed.展开更多
The electronic structure and the optical properties of Ca<sub>2</sub>Ge have been calculated by the first-principles pseudo potential method. The results of the electric structure show that Ca<sub>2&...The electronic structure and the optical properties of Ca<sub>2</sub>Ge have been calculated by the first-principles pseudo potential method. The results of the electric structure show that Ca<sub>2</sub>Ge bulk is a direct semiconductor with the band gap of 0.306 eV, the conduction band is mainly composed of Ca 3d, the valence bands is mainly composed of Ge 3p. With Sr-doping, Ca<sub>2</sub>Ge bulk is a direct semiconductor with the band gap of 0.350 eV, the conduction bands are mainly composed of Ca 3d and Sr 3d, the valence bands are mainly composed of Ge 3p and Sr 3d. The results of the optical properties show that the dielectric constant of Ca<sub>2</sub>Ge bulk is reduced from 21.52 to 13.94, the reflectivity is decreased, and the absorption is increased with Sr-doping. The optical properties are improved with Sr-doping, the results offer theoretical guide for the optical properties control of Ca<sub>2</sub>Ge.展开更多
In this work, ZnO, Ce<sup>3+</sup> doped ZnO (ZnO/Ce<sup>3+</sup>) and Cu<sup>2+</sup> + Ce<sup>3+</sup> co-doped ZnO (ZnO/Cu<sup>2+</sup> + Ce<sup>3+&...In this work, ZnO, Ce<sup>3+</sup> doped ZnO (ZnO/Ce<sup>3+</sup>) and Cu<sup>2+</sup> + Ce<sup>3+</sup> co-doped ZnO (ZnO/Cu<sup>2+</sup> + Ce<sup>3+</sup> ) solid solutions powders were synthesized by a solution combustion method maintaining the Ce<sup>3+</sup> ion concentration constant in 3%Wt while the Cu<sup>2+</sup> ion concentration was varied in 1, 2, 3, 10 and 20%Wt. After its synthesis, all the samples were annealed at 900?C by 24 h. The ZnO, ZnO/Ce<sup>3+</sup> and ZnO/Cu<sup>2+</sup> + Ce<sup>3+</sup> powders were structurally characterized using X-ray diffraction (XRD) technique, and the XRD patterns showed that for pure ZnO, Cu<sup>2+</sup> undoped ZnO/Ce<sup>3</sup><sup>+</sup> and ZnO/Ce<sup>3+</sup> doped with the Cu<sup>2+</sup> ion, the three samples exhibited the hexagonal wurtzite ZnO crystalline structure. However, the morphology and particle size of both samples were observed by means of a scanning electron microscopy (SEM);from SEM image, it is observed that the crystallites of both samples are agglomerated forming bigger amorphous particles with an approximate average size of 1 μm. In addition, the photoluminescence of the ZnO, Ce<sup>3+</sup> doped ZnO and Cu<sup>2+</sup> + Ce<sup>3+</sup> doped ZnO samples was measurement under an illumination of 209 nm wavelength (UV region): for the ZnO/Ce<sup>3+</sup> sample, your emission spectrum is in the visible region from blue color until red color;the UV band of the ZnO is suppressed. The multicolor emission visible is attributed to the Ce<sup>3+</sup> ion photoluminescence, while for the ZnO/Cu<sup>2+</sup> + Ce<sup>3+</sup>, its emission PL spectrum is quenching by the Cu<sup>2+</sup> ion, present in the ZnO crystalline.展开更多
Self-consistent ab initio calculations are performed on the structural, electronic and optical properties of wurtzite ZnO. The Full Potential Linearized Augmented Plane Wave (FP-LAPW) method is applied to solve the Ko...Self-consistent ab initio calculations are performed on the structural, electronic and optical properties of wurtzite ZnO. The Full Potential Linearized Augmented Plane Wave (FP-LAPW) method is applied to solve the Kohn-Sham equations. Results are obtained by using the PBE-GGA and mBJLDA exchange correlation potentials. The energy and charge convergence have been examined to study the ground state properties. The band structure and Density of States (DOS) diagrams are plotted from the calculated equilibrium lattice parameters. The general profiles of the optical spectra and the optical properties, including the real and imaginary part of dielectric function, reflectivity, refractive index, absorption co-efficient, electron energy loss function and optical conductivity of wurtzite ZnO under ambient conditions are discussed. The optical anisotropy is studied through the calculated optical constants, namely dielectric function and refractive index along three different crystallographic axes.展开更多
The zinc oxide seed film was coated on conductive glass (FTO) substrate by the Czochralski method,Zinc acetate and hexamethylenetetramine were used as raw materials to prepare growth solution,and then ZnO film was pre...The zinc oxide seed film was coated on conductive glass (FTO) substrate by the Czochralski method,Zinc acetate and hexamethylenetetramine were used as raw materials to prepare growth solution,and then ZnO film was prepared by a low-temperature solution method.The effects of annealing temperature on the morphology,structure,stress and optical properties of ZnO films were studied.The thin films were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),UV-visible absorption spectra (UV-vis),photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS).The results show that the films are ZnO nanorods.With the increase of annealing temperature,the diameter of the rod increases,and the nanorods tend to be oriented.The band gap of the sample obtained from the light absorption spectra first increases and then decreases with the increase of annealing temperature.When the annealing temperature is 350 ℃,the crystallinity of zinc oxide film is the highest,the band gap is close to the theoretical value of pure ZnO.展开更多
Over the past decades,sea ice in the polar regions has been significantly affecting local and even hemispheric climate through a positive ice albedo feedback mechanism.The role of fast ice,as opposed to drift ice,has ...Over the past decades,sea ice in the polar regions has been significantly affecting local and even hemispheric climate through a positive ice albedo feedback mechanism.The role of fast ice,as opposed to drift ice,has not been well-studied due to its relatively small coverage over the earth.In this paper,the optical properties and surface energy balance of land fast ice in spring are studied using in situ observations in Barrow,Alaska.The results show that the albedo of the fast ice varied between 0.57 and 0.85 while the transmittance increased from 1.3×10-3 to 4.1×10-3 during the observation period.Snowfall and air temperature affected the albedo and absorbance of sea ice,but the transmittance had no obvious relationship with precipitation or snow cover.Net solar shortwave radiation contributes to the surface energy balance with a positive 99.2%of the incident flux,with sensible heat flux for the remaining 0.8%.Meanwhile,the ice surface loses energy through the net longwave radiation by 18.7%of the total emission,while the latent heat flux accounts for only 0.1%.Heat conduction is also an important factor in the overall energy budget of sea ice,contributing 81.2%of the energy loss.Results of the radiative transfer model reveal that the spectral transmittance of the fast ice is determined by the thickness of snow and sea ice as well as the amount of inclusions.As major inclusions,the ice biota and particulates have a significant influence on the magnitude and distribution of the spectral transmittance.Based on the radiative transfer model,concentrations of chlorophyll and particulate in the fast ice are estimated at 5.51 mg/m^(2)and 95.79 g/m^(2),which are typical values in the spring in Barrow.展开更多
The electronic structure and optical properties of bilayer germanene under different warpages are studied by the first-principles method of density functional theory.The effects of warpages on the electronic structure...The electronic structure and optical properties of bilayer germanene under different warpages are studied by the first-principles method of density functional theory.The effects of warpages on the electronic structure and optical properties of bilayer germanene are analyzed.The results of the electronic structure study show that the bottom of the conduction band of bilayer germanene moves to the lower energy direction with the increase of warpages at the K point,and the top of the valence band stays constant at the K point,and so the band gap decreases with the increase of warpage.When the warpage is 0.075 nm,the top of the valence band of bilayer germanene changes from K point to G point,and the bilayer germanene be-comes an indirect band gap semiconductor.This is an effective means to modulate the conversion of bilayer germanene between direct band gap semiconductor and indirect band gap semiconductor by adjusting the band structure of bilayer ger-manene effectively.The study of optical properties shows that the effect of warpage on the optical properties of bilayer ger-manene is mainly distributed in the ultraviolet and visible regions,and the warpage can effectively regulate the electronic struc-ture and optical properties of bilayer germanene.When the warpage is 0.069 nm,the first peak of dielectric function and extinc-tion coefficient is the largest,and the energy corresponding to the absorption band edge is the smallest.Therefore,the elec-tron utilization rate is the best when the warpage is 0.069 nm.展开更多
The electronic structural, effective masses of carriers, and optical properties of pure and La-doped Cd_2SnO_4 are calculated by using the first-principles method based on the density functional theory. Using the GGA+...The electronic structural, effective masses of carriers, and optical properties of pure and La-doped Cd_2SnO_4 are calculated by using the first-principles method based on the density functional theory. Using the GGA+U method, we show that Cd_2SnO_4 is a direct band-gap semiconductor with a band gap of 2.216 eV, the band gap decreases to 2.02 e V and the Fermi energy level moves to the conduction band after La doping. The density of states of Cd_2SnO_4 shows that the bottom of the conduction band is composed of Cd 5 s, Sn 5 s, and Sn 5 p orbits, the top of the valence band is composed of Cd 4d and O 2p, and the La 5 d orbital is hybridized with the O 2 p orbital, which plays a key role at the conduction band bottom after La doping. The effective masses at the conduction band bottom of pure and La-doped Cd_2SnO_4 are 0.18 m0 and 0.092 m_0, respectively, which indicates that the electrical conductivity of Cd_2SnO_4 after La doping is improved. The calculated optical properties show that the optical transmittance of La-doped Cd_2SnO_4 is 92%, the optical absorption edge is slightly blue shifted, and the optical band gap is increased to 3.263 eV. All the results indicate that the conductivity and optical transmittance of Cd_2SnO_4 can be improved by doping La.展开更多
基金Project supported by the Natural Science Foundation of Anhui Province(Grant No.1908085MA12)the National Natural Science Foundation of China(Grant No.21703222)。
文摘Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure.Superalkalis have low ionization energy.Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs.In this paper,the geometry,bonding properties,electronic structure,absorption spectrum,and nonlinear optical(NLO)properties of superalkaline M_(3)O(M=Li,Na)-doped cyclo[18]carbon were studied by using density functional theory.M_(3)O and the C_(18) rings are not coplanar.The C_(18) ring still exhibits alternating long and short bonds.The charge transfer between M_(3)O and C_(18) forms stable[M_(3)O]+[C_(18)]-ionic complexes.C_(18)M_(3)O(M=Li,Na)shows striking optical nonlinearity,i.e.,their first-and second-order hyperpolarizability(βvec andγ||)increase considerably atλ=1907 nm and 1460 nm.
文摘Structural, electronic and optical properties of Sc-based aluminum-nitride alloy have been carried out with first-principles methods using both local density approximation (LDA) and Heyd-Scuseria-Ernzerhof (HSE) hybrid functional. This latter provides a more accurate description of the lattice parameters, enthalpy of formation, electronic and optical properties of our alloy than standard DFT. We found the transition from wurtzite to rocksalt structures at 61% of Sc concentration. By increasing the scandium concentration, the lattice parameters and the band gap decrease. The HSE band gap is in good agreement with available experimental data. The existence of the strong hybridization between Sc 3d and N 2p indicates the transport of electrons from Sc to N atoms. Besides, it is shown that the insertion of the Sc atom leads to the redshift of the optical absorption edge. The optical absorption of Sc<sub>x</sub>Al<sub>1-x</sub>N is found to decrease with increasing Sc concentrations in the low energy range. Because of this, Sc<sub>x</sub>Al<sub>1-x</sub>N have a great potential for applications in photovoltaics and photocatalysis.
文摘Rare earth luminescent materials have attracted significant attention due to their wide-ranging applications in the field of optoelectronics. This study aims to delve into the electronic structure and optical properties of rare earth luminescent materials, with the goal of uncovering their importance in luminescence mechanisms and applications. Through theoretical calculations and experimental methods, we conducted in-depth analyses on materials composed of various rare earth elements. Regarding electronic structure, we utilized computational techniques such as density functional theory to investigate the band structure, valence state distribution, and electronic density of states of rare earth luminescent materials. The results indicate that the electronic structural differences among different rare earth elements notably influence their luminescence performance, providing crucial clues for explaining the luminescence mechanism. In terms of optical properties, we systematically examined the material’s optical behaviors through fluorescence spectroscopy, absorption spectroscopy, and other experimental approaches. We found that rare earth luminescent materials exhibit distinct absorption and emission characteristics at different wavelengths, closely related to the transition processes of their electronic energy levels. Furthermore, we studied the influence of varying doping concentrations and impurities on the material’s optical properties. Experimental outcomes reveal that appropriate doping can effectively regulate the emission intensity and wavelength, offering greater possibilities for material applications. In summary, this study comprehensively analyzed the electronic structure and optical properties of rare earth luminescent materials, providing deep insights into understanding their luminescence mechanisms and potential value in optoelectronic applications. In the future, these research findings will serve as crucial references for the technological advancement in fields such as LEDs, lasers, and bioimaging.
基金supported by the National Natural Science Foundation of China(Grant No.11304105)
文摘Based on the density functional theory, the influences of strain on structural, elastic, thermal and optical properties of CuGaTe_2 are discussed in detail. It is found that the tensile strain on CuGaTe_2 is beneficial to the decrease of lattice thermal conductivity by reducing the mean sound velocity and Debye temperature. Moreover, all strained and unstrained CuGaTe_2 exhibit rather similar optical characters. But the tensile strain improves the ability to absorb sunlight in the visible range.These research findings can give hints for designing thermoelectric and photovoltaic devices.
文摘Transparent conductive cadmium indium oxide films (CdIn2O4) were prepared by r.f. reactive sputtering from Cd-In alloy targets under an Ar-O2 atmosphere. Electrical conductivity of the order of 105Ω-1.m-1 and the optical transmission as high as 94% are easily attained by postdeposition annealing treatment. The effects of oxygen concentration in the reactive gas mixture and post-deposition annealing treatment on the optical transmittance as well as optical parameters, such as refractive index (n), extinction coefficient (k), real part (ε’) and imaginary part (ε") of the dielectric constant, were studied in the visible and near-infrared region. The highfrequency dielectric constant ε∞ the plasma frequency ωP, and the conduction band effective mass mc of different samples were also
基金This work was supported by grants from the National Key Research and Development Program of China(Grant No.2017YFC0210003)the National Natural Science Foundation of China(Grant No.42075177)the Qing Lan Project.
文摘Black carbon(BC)reduces the photolysis coefficient by absorbing solar radiation,thereby affecting the concentration of ozone(O_(3))near the ground.The influence of BC on O_(3)has thus received much attention.In this study,Mie scattering and the tropospheric Ultraviolet and Visible radiation model are used to analyze the effect of BC optical properties on radiation.Combined with data of O_(3)precursors in Nanjing in 2014,an EKMA curve is drawn,and the variations in O_(3)concentration are further investigated using a zero-dimensional box mechanism model(NCAR MM).When O_(3)precursors are unchanged,radiation and O_(3)show a highly similar tendency in response to changing BC optical properties(R=0.997).With the increase of modal radius,the attenuation of fresh BC to radiation and O_(3)first trends upward before decreasing.In the mixing process,the attenuation of BC to radiation and O_(3)presents an upward tendency with the increase of relative humidity but decreases rapidly before increasing slowly with increasing thickness of coating.In addition,mass concentration is another major factor.When the BC to PM_(2.5)ratio increases to 5%in Nanjing,the radiation decreases by approximately 0.13%-3.71%while O_(3)decreases by approximately 8.13%-13.11%.The radiative effect of BC not only reduces O_(3)concentration but also changes the EKMA curve.Compared with the NO_(x)control area,radiation has a significant influence on the VOCs control area.When aerosol optical depth(AOD)increases by 17.15%,the NO_(x)to VOCs ratio decreases by 8.27%,and part of the original NO_(x)control area is transferred to the VOCs control area.
文摘The structural vibrational, thermodynamical, and optical properties of potentially technologically important, weakly coupled MAX compound, Sc2 Al C are calculated using density functional theory(DFT). The structural properties of Sc_2AlC are compared with the results reported earlier. The vibrational, thermodynamical, and optical properties are theoretically estimated for the first time. The phonon dispersion curve is calculated and the dynamical stability of this compound is investigated. The optical and acoustic modes are observed clearly. We calculate the Helmholtz free energy(F), internal energy(E), entropy(S), and specific heat capacity(Cv) from the phonon density of states. Various optical parameters are also calculated. The reflectance spectrum shows that this compound has the potential to be used as an efficient solar reflector.
文摘ZnO nano-particles were synthesized via an ammonical ammonium carbonate solution by precipitation method in presence of some additives such as urea, oleic and stearic acid. The morphology and crystallinity of the obtained zinc oxide particles depend critically on the type of additive which was used. Additives also affected the crystal orientation of precipitate nano-particles. SEM, XRD, BET and UV-visible were used to characterize morphology, microstructure, specific surface area and optical properties of the products.Photo-catalysis properties of the as-prepared ZnO powders were evaluated by degradation of methyl red(acid red) in aqueous solution exposed to UV-light. Results suggested a close relationship among the morphology,size and surface area on photo-catalysis and optical properties of the particles. The widest Egvalue(3.56 e V),highest degradation and decolorization efficiency(99%) were obtained from a sample with the smallest grain size(largest surface area) which were used urea as an additive.
基金by the Science and Technology Planned Projects of Zhejiang Province(2018F10009)the National Key Research&Development(R&D)plan(2016YFD060090305)+2 种基金the Promotion of Project of Forestry Science and Technology of the Chinese Forestry Administration([2016]22)the International Joint Project Between Mars Incorporated and China National Bamboo Research Center(PRSD-026-13)the Science and Technology Planned Projects of Zhejiang Province(2017E8002).
文摘A novel fluorescent composition was firstly isolated from natural winter fresh Moso bamboo shoots,and its optical properties were fully investigated by fluorescence spectroscopy.It could emit strong blue light both in solid and solution state,providing high fluorescence intensity in ethanol.The solution’s concentration and addition of water greatly affected the fluorescence intensity,high concentration and addition of much water could quench fluorescence.Apoptosis results showed that the fluorescent extract(0-25 mg/L)could not induce apoptosis of Hela cells.Confocal fluorescent microscopic imaging in human hepatocellular carcinoma cells(HepG2)was realized using the fluorescent extract,it could dye the whole cell well which was different from 4',6-diamidino-2-phenylindole(DAPI)only dying cell nucleus.The fluorescent extract may be candidate for future natural fluorescent bio-imaging agent.
文摘The structure, electrical transport, and optical properties of GaSe films fabricated by means of radio-frequency (RF) magnetron sputtering in Ar were investigated. The as-sputtered GaSe films were amorphous, and their optical energy gap Eg are 1.9～2.6 eV. The effect of the synthesis conditions on the optical and electrical properties of the GaSe films has also been
基金The reported study was funded by RFBR,Project No.19-38-90306.
文摘Nanofluids have great potential for solar energy harvesting due to their suitable optical and thermophysical properties.One of the promising applications of nanofluids is utilization in solar collectors with the direct absorption of light(DASC).The design of a DASC requires detailed knowledge of the optical properties of nanofluids,which can be significantly affected by the particle size distribution.The paper presents the method to take into account the particle size distribution when calculating nanofluid extinction spectra.To validate the proposed model,the particle size distribution and spectral absorbance were measured for aqueous suspension with multi-walled graphite nanotubes;the minimum size of primary nanoparticles was 49 nm.The proposed model is compared with experiments demonstrating the concentration averaged and maximum discrepancies of 6.6%and 32.2%against 12.6%and 77.7%for a model assuming a monosized suspension.
基金supported in parts by the National Natural Science Foundation of China(No.60776004,60976071)the Laboratory for Thin Film Microfabrication of the Ministry of Education
文摘In this paper we investigated the optical properties of ZnO and Mn doped ZnO nanocrystals that were fabricated by a vapor phase transport growth process, using zinc acetate dihydrate with or without Mn in a constant O2/Ar mixture gas flowing through the furnace at 400600℃, respectively. The as grown ZnO nanocrystals are homogeneous with a mean size of 19 nm observed by scanning electron microscope（SEM）. The optical characteristics were analyzed by absorption spectra and photoluminescence（PL） spectra at room-temperature. For ZnO nanocrystals, a strong and predominant UV emission peaked at 377 nm was found in the PL spectra. For Mn doped ZnO nanocrystals, in addition to the strong UV emission, a strong blue emission peaked at 435 nm was observed as well. By doping Mn ions, the major UV emission shifts from 377 nm to 408 nm, showing that Mn ions were not only incorporated into ZnO Ncs, but also introduced an impurity level in the bandgap. Moreover, with the concentration of Mn increasing, the relative intensities of the two emissions change largely, and the photoluminescence mechanism of them is discussed.
文摘The electronic structure and the optical properties of Ca<sub>2</sub>Ge have been calculated by the first-principles pseudo potential method. The results of the electric structure show that Ca<sub>2</sub>Ge bulk is a direct semiconductor with the band gap of 0.306 eV, the conduction band is mainly composed of Ca 3d, the valence bands is mainly composed of Ge 3p. With Sr-doping, Ca<sub>2</sub>Ge bulk is a direct semiconductor with the band gap of 0.350 eV, the conduction bands are mainly composed of Ca 3d and Sr 3d, the valence bands are mainly composed of Ge 3p and Sr 3d. The results of the optical properties show that the dielectric constant of Ca<sub>2</sub>Ge bulk is reduced from 21.52 to 13.94, the reflectivity is decreased, and the absorption is increased with Sr-doping. The optical properties are improved with Sr-doping, the results offer theoretical guide for the optical properties control of Ca<sub>2</sub>Ge.
文摘In this work, ZnO, Ce<sup>3+</sup> doped ZnO (ZnO/Ce<sup>3+</sup>) and Cu<sup>2+</sup> + Ce<sup>3+</sup> co-doped ZnO (ZnO/Cu<sup>2+</sup> + Ce<sup>3+</sup> ) solid solutions powders were synthesized by a solution combustion method maintaining the Ce<sup>3+</sup> ion concentration constant in 3%Wt while the Cu<sup>2+</sup> ion concentration was varied in 1, 2, 3, 10 and 20%Wt. After its synthesis, all the samples were annealed at 900?C by 24 h. The ZnO, ZnO/Ce<sup>3+</sup> and ZnO/Cu<sup>2+</sup> + Ce<sup>3+</sup> powders were structurally characterized using X-ray diffraction (XRD) technique, and the XRD patterns showed that for pure ZnO, Cu<sup>2+</sup> undoped ZnO/Ce<sup>3</sup><sup>+</sup> and ZnO/Ce<sup>3+</sup> doped with the Cu<sup>2+</sup> ion, the three samples exhibited the hexagonal wurtzite ZnO crystalline structure. However, the morphology and particle size of both samples were observed by means of a scanning electron microscopy (SEM);from SEM image, it is observed that the crystallites of both samples are agglomerated forming bigger amorphous particles with an approximate average size of 1 μm. In addition, the photoluminescence of the ZnO, Ce<sup>3+</sup> doped ZnO and Cu<sup>2+</sup> + Ce<sup>3+</sup> doped ZnO samples was measurement under an illumination of 209 nm wavelength (UV region): for the ZnO/Ce<sup>3+</sup> sample, your emission spectrum is in the visible region from blue color until red color;the UV band of the ZnO is suppressed. The multicolor emission visible is attributed to the Ce<sup>3+</sup> ion photoluminescence, while for the ZnO/Cu<sup>2+</sup> + Ce<sup>3+</sup>, its emission PL spectrum is quenching by the Cu<sup>2+</sup> ion, present in the ZnO crystalline.
文摘Self-consistent ab initio calculations are performed on the structural, electronic and optical properties of wurtzite ZnO. The Full Potential Linearized Augmented Plane Wave (FP-LAPW) method is applied to solve the Kohn-Sham equations. Results are obtained by using the PBE-GGA and mBJLDA exchange correlation potentials. The energy and charge convergence have been examined to study the ground state properties. The band structure and Density of States (DOS) diagrams are plotted from the calculated equilibrium lattice parameters. The general profiles of the optical spectra and the optical properties, including the real and imaginary part of dielectric function, reflectivity, refractive index, absorption co-efficient, electron energy loss function and optical conductivity of wurtzite ZnO under ambient conditions are discussed. The optical anisotropy is studied through the calculated optical constants, namely dielectric function and refractive index along three different crystallographic axes.
基金Funded by Henan International Science and Technology Cooperation Program (No.152102410035)Ph D Research Startup Foundation of Henan University of Science and Technology(No.13480107)。
文摘The zinc oxide seed film was coated on conductive glass (FTO) substrate by the Czochralski method,Zinc acetate and hexamethylenetetramine were used as raw materials to prepare growth solution,and then ZnO film was prepared by a low-temperature solution method.The effects of annealing temperature on the morphology,structure,stress and optical properties of ZnO films were studied.The thin films were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),UV-visible absorption spectra (UV-vis),photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS).The results show that the films are ZnO nanorods.With the increase of annealing temperature,the diameter of the rod increases,and the nanorods tend to be oriented.The band gap of the sample obtained from the light absorption spectra first increases and then decreases with the increase of annealing temperature.When the annealing temperature is 350 ℃,the crystallinity of zinc oxide film is the highest,the band gap is close to the theoretical value of pure ZnO.
基金The National Major Research High Resolution Sea Ice Model Development Program of China under contract No.2018YFA0605903the National Natural Science Foundation of China under contract No.41776192the Fundamental Research Funds for the Central Universities under contract No.202165005。
文摘Over the past decades,sea ice in the polar regions has been significantly affecting local and even hemispheric climate through a positive ice albedo feedback mechanism.The role of fast ice,as opposed to drift ice,has not been well-studied due to its relatively small coverage over the earth.In this paper,the optical properties and surface energy balance of land fast ice in spring are studied using in situ observations in Barrow,Alaska.The results show that the albedo of the fast ice varied between 0.57 and 0.85 while the transmittance increased from 1.3×10-3 to 4.1×10-3 during the observation period.Snowfall and air temperature affected the albedo and absorbance of sea ice,but the transmittance had no obvious relationship with precipitation or snow cover.Net solar shortwave radiation contributes to the surface energy balance with a positive 99.2%of the incident flux,with sensible heat flux for the remaining 0.8%.Meanwhile,the ice surface loses energy through the net longwave radiation by 18.7%of the total emission,while the latent heat flux accounts for only 0.1%.Heat conduction is also an important factor in the overall energy budget of sea ice,contributing 81.2%of the energy loss.Results of the radiative transfer model reveal that the spectral transmittance of the fast ice is determined by the thickness of snow and sea ice as well as the amount of inclusions.As major inclusions,the ice biota and particulates have a significant influence on the magnitude and distribution of the spectral transmittance.Based on the radiative transfer model,concentrations of chlorophyll and particulate in the fast ice are estimated at 5.51 mg/m^(2)and 95.79 g/m^(2),which are typical values in the spring in Barrow.
基金supported by the Science and Technology Foundation of Guizhou Province,China(Nos.1Y[2020]200,1Y[2020]205)the Youth Science and Technology Talents Growth Fund Program of the Ministry of Education Province,China(Nos.KY[2021]105,KY[2021]103).
文摘The electronic structure and optical properties of bilayer germanene under different warpages are studied by the first-principles method of density functional theory.The effects of warpages on the electronic structure and optical properties of bilayer germanene are analyzed.The results of the electronic structure study show that the bottom of the conduction band of bilayer germanene moves to the lower energy direction with the increase of warpages at the K point,and the top of the valence band stays constant at the K point,and so the band gap decreases with the increase of warpage.When the warpage is 0.075 nm,the top of the valence band of bilayer germanene changes from K point to G point,and the bilayer germanene be-comes an indirect band gap semiconductor.This is an effective means to modulate the conversion of bilayer germanene between direct band gap semiconductor and indirect band gap semiconductor by adjusting the band structure of bilayer ger-manene effectively.The study of optical properties shows that the effect of warpage on the optical properties of bilayer ger-manene is mainly distributed in the ultraviolet and visible regions,and the warpage can effectively regulate the electronic struc-ture and optical properties of bilayer germanene.When the warpage is 0.069 nm,the first peak of dielectric function and extinc-tion coefficient is the largest,and the energy corresponding to the absorption band edge is the smallest.Therefore,the elec-tron utilization rate is the best when the warpage is 0.069 nm.
文摘The electronic structural, effective masses of carriers, and optical properties of pure and La-doped Cd_2SnO_4 are calculated by using the first-principles method based on the density functional theory. Using the GGA+U method, we show that Cd_2SnO_4 is a direct band-gap semiconductor with a band gap of 2.216 eV, the band gap decreases to 2.02 e V and the Fermi energy level moves to the conduction band after La doping. The density of states of Cd_2SnO_4 shows that the bottom of the conduction band is composed of Cd 5 s, Sn 5 s, and Sn 5 p orbits, the top of the valence band is composed of Cd 4d and O 2p, and the La 5 d orbital is hybridized with the O 2 p orbital, which plays a key role at the conduction band bottom after La doping. The effective masses at the conduction band bottom of pure and La-doped Cd_2SnO_4 are 0.18 m0 and 0.092 m_0, respectively, which indicates that the electrical conductivity of Cd_2SnO_4 after La doping is improved. The calculated optical properties show that the optical transmittance of La-doped Cd_2SnO_4 is 92%, the optical absorption edge is slightly blue shifted, and the optical band gap is increased to 3.263 eV. All the results indicate that the conductivity and optical transmittance of Cd_2SnO_4 can be improved by doping La.
