Intensity Of Emission Spectra Research Articles

Improvement of TE-polarized emission in type-II InAlN–AlGaN/AlGaN quantum well**Project supported by the Talent Introduction Project of Nantong University, China (Grant No. 03081055), the National Natural Science Foundation of China (Grant Nos. 61874168 and 61505090), Top-notch Academic Programs Project of Jiangsu Higher Education Institutions, China (Grant No. PPZY2015B135), the Six Top Talents of Jiangsu Province, China (Grant No. 2016-XCL-052), the Natural

The optical properties of the type-II lineup InxAl1−xN–Al0.59Ga0.41N/Al0.74Ga0.26N quantum well (QW) structures with different In contents are investigated by using the six-by-six K–P method. The type-II lineup structures exhibit the larger product of Fermi–Dirac distribution functions of electron and hole and the approximately equal transverse electric (TE) polarization optical matrix elements ( for the c1–v1 transition. As a result, the peak intensity in the TE polarization spontaneous emission spectrum is improved by 47.45%–53.84% as compared to that of the conventional AlGaN QW structure. In addition, the type-II QW structure with has the largest TE mode peak intensity in the investigated In-content range of 0.13–0.23. It can be attributed to the combined effect of and for the c1–v1, c1–v2, and c1–v3 transitions.

Effective Suppression of Antiphase Domains in GaP(N)/GaP Heterostructures on Si(001)

III–V planar semiconductor heterostructures based on GaPN alloy with a nitrogen concentration up to 2.12% were grown on Si(001) by plasma assisted molecular beam epitaxy. Dependence of nitrogen incorporation on the growth conditions and its effect on the crystal structure were investigated via analysis of X-ray diffraction, transmission electron microscopy, and Raman spectroscopy data. Continuous redshift and a substantial increase in intensity of the photoluminescence emission spectra were observed upon increase of nitrogen content. The effect of antiphase disorder in GaP buffer on the GaPN epilayer properties was studied. It was found that antiphase boundaries, protruding from the GaP/Si to the GaPN/GaP heterointerface, change their orientation and self-annihilate in the dilute nitride layer even with a low (0.5%) nitrogen content.

Optical and photoluminensce properties of Eu2+-activated strontium magnesium silicate phosphors using different rare earth co-activators

Nanostructured powders of Sr1.96MgSi2O7:Eu 0.01 2+ , R 0.01 3+ (R3+ = Er3+, Tm3+ and Tb3+) have been fabricated via urea combustion technique. XRD results implied that tetragonal Sr2MgSi2O7 was the major phase whereas monoclinic Sr2SiO4 and SrSiO3 were the minor phases. Meanwhile, field emission SEM textures showed the hollow spherical network-like shape structures filled with fused interconnections for the Sr1.96MgSi2O7:Eu 0.01 2+ sample. It has been recognized that the replacement of Sr2+ with co-dopant R3+ ions e.g. Er3+, Tm3+ and Tb3+ considerably help obtaining homogeneous structure as well. The values of band gap energy and calculated refractive index were ultimately dependant on the ionic radius of R3+ co-doping ion. It has been suggested that the divalent activator ion (Eu2+) was responsible for the number of PL emission spectra, while the trivalent co-activator ions (R3+) were the key reasons for variations in the broadening and intensity of PL emission spectra.

Effect of pressure of laser-induced plasma spectroscopy for zinc element identification in multivitamin

Identification of zinc elements in 99.9% pure zinc metal and zinc multivitamin tablet samples has been done using Laser Induced Plasma Spectroscopy (LIBS) method. Plasma is generating by laser firing Nd: YAG (1064 nm, 50 mJ, 7 ns). Optimization of laser plasma was performed by varying environmental air pressure and on the spectrum of zinc. The character of samples is displayed in the spectrum line. Spectrum line of 99.9% pure zinc metal shows neutral zinc (Zn I) emission at wavelengths of 280.08, 330.25, 334.50, 472.21, 481.05 and 636.23 nm, and ionic zinc (Zn II) emission of 99.9% pure zinc metal at wavelengths of 250.19 and 255.79 nm. Zinc multivitamin tablet spectrum line shows Zn I emission at the wavelengths as same as 99.9% pure zinc metal of 334.50 and 481.05 nm, which is the intensities of Zn I at a wavelength of 334.50 and 481.05 nm in zinc multivitamin tablet is much higher than in the 99.9% pure zinc metal. The higher the given environmental air pressure, the higher the intensity of the zinc emission spectrum accompanied by high background emission intensity.

Synthesis, characterization and photo physical properties of two novel n-type semiconductor materials with trifluoromethyl and cyano groups

Two π-conjugated materials (3a, 3b) possessing –CF3 and -CN were prepared by Knoevenagel condensation by reacting benzene 1,3,5-tricarboxaldehyde and 4-(trifluoromethyl) phenyl acetonitrile, 3,5-bis(trifluoromethyl) phenyl acetonitrile in the presence of sodium ethoxide. The proposed structures of 3a, 3b were elucidated by 1H NMR and Elemental analysis. To study the structure-property relationship, molecular structures of 3a and 3b were determined by X-ray diffraction analysis. In the crystal, molecules are linked by C_H⋯F, C⋯C and F⋯F short contacts, forming a layer like three dimensional networks. From X-ray diffraction analysis it was observed that molecule 3a has better planarity than molecule 3b suggested by angles between the planes of molecules. The molecules 3a and 3b displayed strong absorption maximum at 319 nm corresponding to the π→π* transitions within the whole conjugated molecules and emissions in the visible region at 373–475 nm. The shape and intensity of absorption and emission spectra of 3a, 3b almost identical. Further, we found that molecule 3b (M.p. 251–252 °C) has relatively higher melting point than molecule 3a (M.p. 231–232 °C). Molecules 3a and 3b have emissions close to blue light, may serve as model materials for new OLED applications.

Enhancement of electrical and magnetic properties in acceptor-doped BaTiO3 ferroelectric ceramics

BaTi1−xMnxO3 (x = 0.00, 0.25, 0.50, 0.75 mol%) (BTMO) ceramics were synthesized through sol–gel combustion method. The structural studies suggested that Mn-doped BaTiO3 (BTO) ceramics exhibit a tetragonal structure with P4mm space group via Rietveld refinement analysis. Also, the phonon mode at 308 cm−1 through Raman spectral analysis confirms the local structure of tetragonal symmetries. The redshift observed in UV-absorption spectra indicates a decrease of optical band gap from 3.13 to 2.71 eV with increasing Mn2+ doping. The observed decrease in the intensity of PL emission spectra was due to an increase of Mn2+ concentration. This indicates that a decrease in oxygen vacancies and a reduction in the number of electrons attributed to the Burstein–Moss shift. The carrier hopping process between Mn2+ and Mn3+ is responsible for dielectric as well as magnetization behavior. The ferroelectric double hysteresis loops are related to a ferroelectric and anti-ferroelectric order and it increases with the increase of Mn ion concentration in BTO. Through P–E measurements, the value of remnant electric polarization and coercive field found to be increased with Mn concentration in BTO samples. For BTO sample, two EPR signals with g = 1.969 and g = 2.000 singlets can be assigned with ionized Ba and Ti-vacancy defects. In addition, the EPR signal for BTMO shows a good correlation with Ti vacancies as compensating for lattice defects. Further, the Mn doping induced a weak ferromagnetic to ferromagnetic state due to free carrier concentrations.

Simulation study on plasma discharge and transport in cylindrical cathode controlled by expanding electromagnetic field

High-power impulse magnetron sputtering (HiPIMS) is a new magnetron sputtering technique which can produce high-density plasmas with a high ionization rate and prepare coatings with a good performance such as large density and high adhesion. To obtain stable discharge and universal materials’ ionization rates, a cylindrical cathode is proposed based on the hollow cathode effect. However, the unusual plasma transport results in a large loss of ions and a low deposition rate. To solve these problems, an expanding electromagnetic field is proposed to control the plasma transport in this work. The particle in cell/Monte Carlo collision (PIC/MCC) method and the plasma diffusion model are used to simulate the plasma transport in and out of the cylindrical cathode with different currents in the electromagnetic coils, respectively. The simulation results reveal that different electromagnetic fields can achieve different plasma density distributions, resulting in different accumulated positions and different diffusion paths. When the coil current is positive, the resistance to axial motion of electrons is small but the resistance to radial motion is large, so that the hollow cathode effect is weakened and the plasma beam tends to output uniformly. When the coil current is negative, the resistance to axial motion of electrons is large but the resistance to radial motion is small, so that the hollow cathode effect is enhanced and the plasma tends to gather on the central axis and then diffuses outward. To verify the simulation results, Ar/Cr HiPIMS discharge experiments are carried out with the cylindrical cathode in a homemade vacuum system. The experiment results indicate that the threshold voltage, the plasma flow shape, the optical emission spectrum (OES) intensity, and the deposition distribution are determined by the electromagnetic coil current. The variation tendency is in coincidence with the prediction of the simulation. Consequently, by adding an expanding electromagnetic field, the plasma discharge in the cylindrical cathode can be easily controlled and the deposition rate is greatly enhanced. This electromagnetic control strategy not only realizes the enhancement and effective control of plasma, but also improves the homogeneity and the deposition rate of the coatings, thus laying a foundation for the industrial application of HiPIMS.

Effect of Alkali Oxides on Luminescence Properties of Eu3+-doped Aluminium Phosphate Glasses

Abstract Trivalent europium doped aluminium phosphate glasses with different alkali oxides (Li2O, Na2O and K2O) have been prepared by melt quenching technique at 1200 °C. Photoluminescence properties of the obtained glasses have been studied and characterized. Also, Absorption and radiative properties of glasses are evaluated using the Judd–Ofelt (JO) theory. The emission spectra of all glasses remain the characteristic emission peak of Eu3+ with a dominant peak at 612 nm, corresponding to the 5D0 → 7F2 transition by monitoring an excitation wavelength at 393 nm. In the present glass system it was found that lithium oxide has higher intensity of emission spectra than sodium oxide and potassium oxide. The JO intensity parameters (Ω2, Ω4, Ω6) and subsequent radiative properties for the 5D0 → 7FJ (J = 1,2,3,4) transitions are determined. These glasses have potential candidate in the development as red laser source applications.

White emission from NaO-BaO-Bi2O3-SiO2 Glass system Doped with Dy3+

Abstract The effect of Dy3+ ions on the physical, optical and luminescence properties of (40-x)SiO2: 25Na2O: 10Bi2O3: 25BaO: xDy2O3 where x = 0.0, 0.1, 0.5, 1.0, 1.5 and 2.0 % mol by concentration melt-quenching at 1200°c. The results demonstrated the increases in the density and molar volume with the respect to the increase in the Dy3+ ions concentration. The glass absorbed bands in the near infrared and visible light region. The bands at 385 nm exhibited the highest excitation in visible light. The strongest band centre at 575 nm and the intensity of emission spectra increase up to 1.5 mol% of Dy3+ ion concentration and the decrease. The CIE 1931 chromaticity diagram exhibits that emissions from Dy3+ ions concentration in glass samples are white-light. All results indicate that the Dy3+ ions concentration in glass samples performs the intensity properties by using in the scintillator materials.

Microstructures, optical properties and application in WLEDs of large-size YAG:Ce3+-Al2O3 eutectic grown by HDS method

Large-size YAG:Ce3+-Al2O3 eutectics with the dimensions of 170 mm × 160 mm × 25 mm, a resin-free phosphor for WLEDs, were successfully grown by HDS method. The influence of annealing, growth rate, the mole ratio of Ce/Y on microstructures and optical properties of the eutectics and the preferred orientations in different cross-sections of the eutectics were investigated. Increasing the growth rate and annealing in the air atmosphere could appropriately increase the intensity of excitation and emission spectra of the eutectics. The coarse microstructure regions in the eutectics were triggered by the doping of Ce, meanwhile unconnected layer-type and connected network-type coarse microstructure appeared on the parallel cross-section (⊥X) and the perpendicular cross-section (⊥Z), respectively. “Ce-rich phase” was formed in the microstructures of the eutectics when Ce/Y exceeded 0.50%. At the same time, the valence of Ce in “Ce-rich phase” was determined by XPS and EDS. The influence of the eutectic pieces' transmittance on the luminous characteristics of the WLEDs with those pieces was analyzed. The results showed that WLED with the fine polished eutectic piece was performed much better than the traditional WLEDs.

Study of the behavior of short chains in print paper subjected to a natural aging

Degradation of paper through time can be measured by monitoring the intensity changes in the band located at 620 nm of its emission fluorescence spectra. The behavior of this band is closely related to the structural stability of the short cellulose chains. A fast degradation of these cellulose chains, mainly lignin, translates in the rapid denaturation of paper occurring at its first aging state. This work proposes a method to reincorporate short cellulose chains in the structure of aged paper through its immersion during 24 h in a solution based on ethyl alcohol and extracts of wood pieces. Results of fluorescence spectra measurements indicate that the short cellulose chains in the solution get embedded in the old paper, making the shape and intensity of the fluorescence emission spectra peaks of new and old paper almost indistinguishable. This behavior provides a desirable approach to analyze, preserve and restore aged paper documents.

Influence of the Tb3+ concentration on the luminescent properties of high silica glass

Tb3+- doped high silica glass was prepared by sintering porous glass. The density, valence state and amount of Tb, transmittance, photoexcitation spectra, photoluminescence spectra, and cathodoluminescence spectra (CL) were recorded and the luminescence decay kinetics analyzed in details. These results show that the doping concentration in high silica glass is in direct proportion to the concentration in solution, and the density increases with the increasing concentration of rare earth ions as well as the intensity of emission spectrum. The largest emission intensity of 0.2 mol/L is more than 2 times higher than the intensity of the 0.05 mol/L. Besides, the “red” shift phenomenon could be distinguished clearly in the transmittance spectra. There is a broad band at the “red” region in the CL spectra. The decay time which is in the millisecond range in different spectral range were measured and analyzed revealing that the decay time of 5D3 is shorter than that of 5D4.

Growth and Optical Properties of a Cs2Mo2O7 Single Crystal

A Cs2Mo2O7 single crystal, a molybdenum-based crystal as research and development scintillation material for future neutrinoless double beta decay experiments under milli-Kelvin temperatures, was grown by the Czochralski method. The grown crystal was prepared as a sample for measurements of its optical properties. The sample was cooled down from room temperature to 10 K, and temperature dependence of emission spectrum and decay time were measured. We used a light emitting diode as an excitation source for the emission spectra measurements and a pulsed-type laser for the decay time due to its high intensity. The intensity of emission spectrum and the decay time increased as the temperature decreased. We estimated the optical energy bandgap via a transmittance measurement at room temperature. As far as we know, it is the first time to grow a large Cs2Mo2O7 crystal and to study its luminescence properties. Moreover, we grew a well-studied Li2MoO4 crystal as a reference to compare the light output of the Cs2Mo2O7 at 10 K. Through these results, the Cs2Mo2O7 crystal found to be a candidate scintillator for the future neutrinoless double beta decay experiments.

Research on spectral characteristics of laser-induced plasma by combining Au-nanoparticles and magnetic field confinement on Cu

In order to enhance the intensity of emission spectra of laser-induced plasma, a method of combining magnetic field enhanced laser induced breakdown spectroscopy(LIBS) with nanoparticle enhanced LIBS (NELIBS) was proposed. Laser-induced breakdown of copper was respectively performed by using traditional LIBS, magnetic field-enhanced LIBS, NELIBS, and the combination of the magnetic field enhanced LIBS and NELIBS.Some parameters including electron temperature, electron density and signal-to-noise ratio were obtained and analyzed. The experimental results show that when the Au-nanoparticles(Au NPs) are combined with magnetic field in LIBS, the spectral intensity of plasma is effectively enhanced and, the signal-to-noise ratio is significantly improved, and the optimum is achieved when the laser pulse energy is 80 mJ; the electron temperature and the electron density do not change obviously, the ability of using LIBS to detect trace elements is significantly improved.

Development of hybrid extreme learning machine based chemo-metrics for precise quantitative analysis of LIBS spectra using internal reference pre-processing method

Laser induced breakdown spectroscopy (LIBS) is a versatile spectroscopic technique that requires little or no sample preparation and capable of simultaneous elemental sample analysis. Quantitative analysis of its spectra has been a major challenge due to self-absorption of the emitted radiation during plasma cooling and inadequate description of non-linear complex interactions taking place in the laser induced plasma. This work presents a novel chemo-metric tool, extreme learning machine (ELM) and its hybrid HHELM (homogenously hybridized ELM), for the first time in modeling the complex interactions of laser induced plasma and quantification of LIBS spectra. Internal reference preprocessing (IRP) method is also proposed as a novel method of enhancing the performance of ELM based chemo-metrics. Since the proposed chemo-metrics (ELM and HHELM) determine their input weights as well as their hidden biases in a random manner, ELM and HHELM are respectively hybridized with gravitational search algorithm (GSA) for optimization of the number of hidden neurons. Effect of IRP, obtained by normalizing the emission spectra intensities with the emission intensity that has highest upper level excitation energy and lowest transition probability, on the performance of the proposed GSA-ELM and GSA-HHELM chemo-metrics is investigated. The proposed models are implemented using spectra of seven bronze standard samples. Chemo-metrics with IRP (GSA-ELM-IRP and GSA-HHELM-IRP) show better generalization performance than those without IRP (GSA-ELM-WIRP and GSA-HHELM-WIRP) while GSA-HHELM based chemo-metrics perform better than their counterparts. The outstanding performance demonstrated by the proposed chemo-metrics and their self-absorption correction ability would definitely widen the applicability of LIBS and improve its precision for the quantitative analysis.

SnS-AuPd thin films for hydrogen production under solar light simulation

In this work, SnS films were obtained by the SILAR method at 25 and 50 cycles. These films were used by the first time in the photocatalysis process to produce H2 under simulated sunlight. Additionally, AuPd was deposited by physical vapor deposition method on SnS films, which served as co-catalyst to increase the photocatalytic activity of the films. Characterization was done by X-ray diffraction (XRD), where it was found that SnS crystallizes in an orthorhombic crystal structure. By scanning electron microscopy (SEM) it was appreciated a homogeneous distribution in SnS 25 cycles film, while SnS 50 cycles film showed a greater density of particles deposited on the substrate. Band gap energy (UV-vis) for SnS 25 cycles and SnS 50 cycles films were close to 2.0 and 1.25 eV, respectively. Photoluminescence (PL) analysis showed that the emission spectra intensity of films decreases due to the presence of co-catalyst because of the lower electron-hole pair recombination. Both, SnS 25 cycles and SnS 50 cycles films, were able to produce H2 under solar light simulation (91 and 32 μmol/m2 after 3-h irradiation). This activity was increased when AuPd was deposited as co-catalyst on SnS films; around 8 and 6 times, for SnS-AuPd 25 cycles and SnS-AuPd 50 cycles films, respectively (728 and 175 μmol/m2 after 3-h irradiation). Therefore, it can be assumed that AuPd co-catalyst favors the transfer charge and decrease the electron-hole pair recombination to promote and enhance the photocatalytic H2 production.

Solvatochromic and nonlinear optical properties of Eosin B in solvents and AOT/water/Heptane

The third-order susceptibility and second-order hyperpolarizability and the two-photon absorption coefficient of Eosin-B in AOT/water/Heptane were investigated by using the Z-Scan technique. The droplets were prepared with an AOT/water droplet in a continuous phase of Heptane. The droplets size changes with the amount of water and the droplet concentration decreases with the increase of Heptane concentration. To study the nonlinear optical properties of Eosin-B, the Z-scan measurements were performed by means of a laser at 532 nm and 80 mW power. The nonlinear refractive and the nonlinear absorption coefficient indices were found to be in the order of 10−12 (cm2 W−1) and 10−7 (cm W−1), respectively. The change of nonlinear optical properties of Eosin-B by droplet size and concentration is due to the change of dye aggregation and thermal conductivity and thermo-optic coefficient of samples. The absorption of Eosin-B changes with the polarity of the medium (dielectric constant and refractive index). It has been shown that the intensity of emission spectra of Eosin-B in AOT/water/Heptane is enhanced compared to that of aqueous solution. By the Bilot and Kawski theory, the ratio between the excited state and the ground state of the dipole moments (μe/μg) of Eosin-B both in water and in droplets is extracted.

The Effect of TiO2-Nanoparticle on the Activity and Stability of Trypsin in Aqueous Medium

Trypsin (E.C.3.4.21.4) is a serine protease commonly used in proteomics for digestion of proteins. In the present study, the effect of nano-TiO2 on the conformation and catalytic activity of trypsin were studied. The thermal denaturation of trypsin has been investigated in the presence and absence of nano-TiO2 over the temperature range (293-373 K) at pH 3.0 and 7.25, using temperature scanning spectroscopy. In presence of nani-TiO2, the ester lytic activity of trypsin is decreased. The result indicates that Nano-TiO2 is a non-competitive inhibitor for enzyme trypsin. With the addition of TiO2 to protein solution at pH 3.0, the maximum intensity of emission spectrum of trypsin is increased. But at pH 7.25, the maximum intensity of emission spectrum of trypsin is decreased. The result of fluorescence spectroscopy indicated that the structure of the Trp residue environments was altered. Increasing the concentration of nano-TiO2 decreases the stability of trypsin to thermal denaturation.

Simultaneous multi-wavelength ultraviolet excited single-phase white light emitting phosphor Ba1-x(Zr,Ti)Si3O9:xEu

A kind of novel compound Ba1-x(Zr,Ti)Si3O9:xEu simultaneously activated by different-valence Eu2+ and Eu3+ ions has been successfully synthesized. The existence of Ti4+-O2- charge transfer (CT) transitions in Ba1-xZrSi3O9:xEu is proved by the photoluminescence spectra and first principle calculations, and the Ti4+ ions come from the impurities in commercial ZrO2 raw materials. Under the excitation of multi-wavelength ultraviolet radiation (λEX = 392, 260, 180 nm), Ba1-xZrSi3O9:xEu (x = 0.15) can directly emit nearly white light. The coexistence of multiple luminescent centers and the energy transfer among Zr4+-O2- CT state, Ti4+-O2- CT state, Eu2+ and Eu3+ ions play important roles in the white light emission. Ba1-xZrSi3O9:xEu (x = 0.15) has good thermal stability, in particular, the intensity of emission spectrum (λEX = 392 nm) at 150 °C is ∼96% of that at room temperature. In general, the multi-wavelength ultraviolet-excited single-phase white light emitting phosphor Ba1-x(Zr,Ti)Si3O9:xEu possesses a promise for applications in white light emitting diodes (WLEDs), agriculture, medicine and other photonic fields.

A new approach to the old problem: Inner filter effect type I and II in fluorescence

The fluorescence technique is very popular and has been used in many fields of research. It is simple in its assumptions but not very easy to use. One of the main problems is the inner filter effect (IF) I and II which takes place in the cuvette. IF type I is permanently present, but IF type II occurs only when absorption and fluorescence spectra overlap. To avoid IF type I, absorbencies in the cuvette should be smaller than 0.05, which is however very difficult to obtain in many experiments. In this work we propose a new method to solve these problems in the case of a Cary Eclipse fluorimeter, having horizontally-oriented slits, based on old equations developed in the middle of the last century. This method can be applied for other instruments, even these with vertically-oriented beams, because we share scripts written in MATLAB and GRAMS/AI environment. Calculations in our method enable specifying beam geometry parameters in the cuvette, which is necessary to obtain the correct shape and fluorescence intensity of emission and excitation spectra. Such a specific fluorescence intensity dependence on absorbance can, in many cases, afford possibilities to determine the quantum yield (QY) using slopes of the straight-lines, which was demonstrated with the use of Tryptophan (Trp), Tyrosine (Tyr), and Rhodamine B (RhB) solutions. For example, assuming that QY=0.14 for Tyr, the QY determined for RhB reached QY=0.71±0.05, although the measurement for Tyr and RhB was performed at a completely different spectral range.