Spontaneous Luminescence Research Articles

Assessment of the Development of Metabolic Disorders Following Chronic Low-Dose Exposure to the Amine Salt of 2,4-Dichlorophenoxyacetic Acid in the Animal Experiment

Introduction: 2,4-Dichlorophenoxyacetic acid (2,4-DA) is one of the most common environmental pollutants from the group of organochlorine herbicides. In our experiment, we focused on effects of low doses of 2,4-dichlorophenoxyacetic acid on metabolic parameters, which have been studied to a lesser extent. Objective: To assess the development of metabolic disorders following chronic low-dose exposure to the amine salt of 2,4-dichlorophenoxyacetic acid in an experiment. Materials and methods: The study was conducted on 36 male Wistar rats for 16 weeks in the spring-summer period with the 12/12 hour day/night cycle. Only healthy animals with the body weight of 170±3 g were included in the experiment and divided into the control and exposure groups (Groups 1 and 2, respectively) of 18 animals each. The latter were exposed to 0.5 MAC of 2,4-DA administered with drinking water (0.3–0.4 µg/kg/day). At week 14, the animals underwent a glucose tolerance test. To assess the development of metabolic disorders, the following parameters were measured in blood serum: total protein, albumin, creatinine, uric acid, activity of aspartate and alanine transaminases, alkaline phosphatase, lactate dehydrogenase, total cholesterol, high-density lipoprotein cholesterol, very low- and low-density lipoprotein cholesterol, and triacylglycerols. Statistica 10.0 was used for the analysis. The data were normally distributed (chi-squared test) and are presented as mean (M) and standard error of the mean (m). Results: We observed a decrease in the levels of total protein and albumin and a moderate increase in the activity of serum enzymes (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase) accompanied by the development of hypercholesterolemia, triacylglyceridemia, and dyslipoproteinemia. Results of the glucose tolerance test showed that low doses of 2,4-dichlorophenoxyacetic acid induced insulin resistance in the exposed animals. The main parameters of chemiluminescence in their blood serum, such as spontaneous luminescence, fast flash amplitude, and light sum, were 2.4, 9.3, and 4.1 times higher than in the controls, respectively. We also established a decrease in the level of serum iron by 20 % and an increase in that of ferritin by 12 % compared to the control rats. Conclusions: Long-term low-dose exposure to 2,4-DA induced an increase in the level of markers of metabolic disorders, which can be used to diagnose and assess the state of metabolic processes in the body.

Flame reconstruction of hydrogen fueled-scramjet combustor based on multi-source information fusion

Using various types of data to extract different features and reconstruct flame spontaneous image, the rapid acquisition of flame propagation data and automatic identification of the combustion state in a scramjet combustion chamber in confined space can be promoted. A reconstruction model based on multi-source information fusion is proposed that can effectively reconstruct a flame self-luminous image based on the combustor wall pressure and schlieren image data. A dense convolutional neural network is used to construct and reconstruct the model and train the network based on the experimental datasets. The ground pulse combustion wind tunnel test is conducted under the condition of hydrogen fuel self-ignition using the variation rules of different injection pressures. The evolution process of the combustor wall pressure, schlieren image, and flame self-luminescence image is obtained over time and a dataset is constructed. The reconstruction accuracy of the flame spontaneous luminescence image using the schlieren image and the fusion of the schlieren image and wall pressure under different injection pressure is comprehensively analyzed. Moreover, both qualitative and quantitative results show that the prediction accuracy of flame spontaneous illumination based on multi-source information fusion well matches the experimental result, and the flame boundary, flame head region, flame area, and burning intensity are all well reconstructed. The average peak signal to noise ratio reached 31.57 dB, average structural similarity was 0.939, average mean square error was 0.979, correlation coefficient was 0.0013, and intersection over union reached 0.876.

A Study on Combustion Characteristics of Insensitive Triple-Base Propellant

Research on combustion characteristics can provide basic information and theoretical support for the design of insensitive propellant. This work aims to investigate the combustion characteristics of insensitive triple-base propellant. All propellants were prepared based on same triple-base propellant, but they were desensitized with the same desensitizer in different ways. The high-speed camera, spontaneous luminescence, NO, NH chemiluminescence, and OH-planar laser induction fluorescence (PLIF) methods were employed to capture the combustion flame and derive the distributions of important intermediates. Results show that ignition delay times of insensitive propellants are obviously longer. This indicated that the application of the desensitizer has a partly hindering effect on the early ignition stage. The combustion time of insensitive propellants is mostly similar, which means that the desensitizer has little influence on the intensity of actual combustion. The change in flame height and area of insensitive propellants over time indicated that the combustion progressivity of some insensitive propellants was more prominent, which means that the desensitizer concentration and desensitizing methods all affect the performance of insensitive propellant. The signal intensities of NO and NH show a negative correlation, indicating that a competitive relationship probably exists between the formation of NO and NH radicals during the reaction process. The high concentration of OH mainly locates outside NO, suggesting that there may be a transformation between NO and OH. The maximum signal intensity of NO and NH of different insensitive propellants confirmed that both the concentration of desensitizers and the desensitizing methods exhibit important effect on the reaction process.

Chemiluminescence diagnosis of oxygen/fuel ratio in fuel-rich jet diffusion flames

Equivalence ratio is one of key parameters associated with various flame characteristics such as flame structure and heat release rate. Chemiluminescence diagnosis of equivalence ratio has received extensive attention but not yet perfected, especially for fuel-rich diffusion flames. In this paper, the feasibility for evaluating molar equivalence ratio of oxygen to fuel in the fuel-rich conditions based on radical chemiluminescence diagnosis was explored. The sensitivity of the spontaneous luminescence intensity to the change of the nominal oxygen/fuel ratio in co-flow CH4-O2 jet diffusion flames was quantitatively studied. In addition, the two-dimensional distributions of the intensity ratios of CH* to CO2* and OH* to CH* were further analyzed, and local oxygen/fuel ratios were reconstructed. The results show that OH* chemiluminescence is more sensitive to changes in nominal oxygen/fuel ratio than CH* and CO2*. The sensitivity of CH* to oxygen/fuel ratio increases with the rise of CH4 flow rate, while the sensitivity of CO2* decreases. The reconstructed value of local oxygen/fuel ratio according to the two-dimensional intensity ratio of CH* to CO2* is underestimated, while based on the intensity ratio of OH* to CH* it is overestimated. Combined with these two intensity ratio distributions, the local oxygen/fuel ratio can be roughly determined.

Carboxylated cellulose nanocrystal films with tunable chiroptical properties

Carboxylated cellulose nanocrystals prepared by TEMPO-mediated oxidation exhibit a distinct ability to form nematic order, however, their ability to form chiral nematic films remains relatively unexplored. In this study, bleached cotton pulp hydrolyzed with hydrochloric acid and oxidized by TEMPO-mediated oxidation produce carboxylated cellulose nanocrystals with different aspect ratios 33.1, 32.8, 30.9, 29.0 and 28.9, and surface charge densities 0.16, 0.56, 1.00, 1.25, and 1.42 e·nm−2. By tuning the aspect ratio and surface charge density, the optimal carboxylated cellulose nanocrystals producing left-handed chiral nematic films by evaporation-induced self-assembly are obtained. The left-handed chiral nematic films enable selective reflection of left-handed circularly polarized light with the peak wavelength tunable from the visible to the near-infrared regime by modifying the characteristics of nanorods and suspensions. Such carboxylated cellulose nanocrystal films transform spontaneous luminescence to right-handed circularly polarized luminescence with the peak luminescence dissymmetry factor of −0.51.

Homeotropic Concentric Helix Orientations in Chiral Nematic Cellulose Nanocrystal Films by Local Magnetic Fields

AbstractMany fascinating device applications of chiral nematic materials are determined by their helical axis orientations. Cellulose nanocrystals (CNCs) self‐assemble producing left‐handed chiral nematic films with predominant planar textures. While varied techniques have been exploited to tune the helical axis orientations, it remains challenging to produce concentrically aligned chiral nematic state. Herein, the authors report novel findings that left‐handed chiral nematic CNC films formed with homeotropic concentric helix orientations in the planar textures can be realized by local radial magnetic field‐directed self‐assembly of CNCs. These chiral nematic CNC films display left‐handed circular polarization patterns and transform spontaneous luminescence to right‐handed circularly polarized luminescence on both film plane and lateral surfaces owing to the underlying photonic bandgaps. These plane‐lateral chiroptical properties can be tuned simultaneously from the visible to the near‐infrared spectral regime. Their work presents a step towards the development of self‐organized chiroptical materials encoded with complex polarization features for photonic applications.

Plasma-Assisted Molecular Beam Epitaxy of In-Rich InGaN: Growth Optimization for Near-IR Lasing

Near-infrared stimulated emission (SE) from InGaN layers grown by plasma-assisted molecular beam epitaxy has been studied, and the influence of the growth temperature (T gr) on the SE threshold has been revealed. The obtained experimental data strongly suggest a two-layer model for the grown InGaN structure with a thin defect-rich interface layer and a relatively pure InGaN bulk responsible for light emission. For the latter, the crystalline quality appears to be unaffected by the growth temperature, at least in terms of free electron concentration, which is supported by the similar spontaneous luminescence intensities measured throughout the entire T gr range of 430 °C–510 °C. However, the quality of the interface layer improves with increasing T gr, leading to a decrease in the SE threshold down to ∼10 kW cm−2 at T = 77 K for the samples grown at T gr = 470 °C–480 °C. For the higher growth temperatures (T gr ≥ 490 °C), the SE threshold increases rapidly with T gr, apparently related to the strong waveguide losses due to the increasing surface roughness of the InGaN layer, and SE vanishes completely at T gr = 510 °C, further suppressed by the partial phase separation of the InGaN alloy.

Design and fabrication of high power InGaN blue laser diode over 8 W

The impact of multi quantum wells (MQWs) structure on the homogeneity of spontaneous luminescence and quantum efficiency of the high power InGaN blue laser diode (LD) is numerically investigated. The structure with 2QWs in the active region is found to be the optimal choice for the high power InGaN LD. Accordingly, the edge emitting LD structure is grown and fabricated. To study the facet coating effect on the catastrophic optical damage (COD) level, three types of LDs are coated with different materials by different techniques, respectively. The characterization results confirm that the single blue LD coated with the Al2O3 and Al2O3/Ta2O5 films by electron cyclotron resonance deposition exhibits the highest COD level, due to the better crystal quality and interfacial quality of the coated films. The LD starts to operate at 1.04 kA/cm2 with slope efficiency of 1.8 W/A and the wavelength of 444.9 nm. As a result, the output power as high as 8.04 W is achieved at 5.5 A.

The analysis of amplified spontaneous emission and luminescence enhancement of BUBD-1 based on host-guest system

The lowest amplified spontaneous emission (ASE) threshold (1.51 μJ/pulse) of CBP: 2 wt%BUBD-1 blend films was about 6 times lower than that of BUBD-1 neat film (9.25 μJ/pulse). The OLEDs with blend film as the emission layer (EML) exhibited an excellent photoelectric performance. In this regard, a series of theoretical analysis were carried out to explain the enhancement of ASE and luminescence performance of BUBD-1 in different aspects. Except for the reducing concentration quenching, a higher Stokes shift, energy transfer efficiency and radiation attenuation rate (kr) happened in the blend films. Moreover, the molecular dipole orientation of EML films at the interface and in thin films were analyzed based on the second-harmonic generation (SHG) method and angle-dependent PL spectra analysis. We find that not only the molecular dipole orientation angle alters in the blend film relative to the neat film, but also the angle is different when the films deposited with different methods. Based on the calculated molecular dipole orientation angle, we propose that the varied dipole angle in the blend film contributed to the device properties too. Our works provide a theory insight into the enhancement of ASE and luminescence properties based on host-guest system.

Pyroelectric activity of LiGaO2, Li2GeO3, Li2B4O7 and LiNbO3 crystals: Pyroelectric luminescence and excitation of cathodoluminescence in scintillator ScPO4

Abstract Basing on results of electric, spectral and kinetic measurements of spontaneous luminescence caused by cooling/heating in pyroelectric crystals LiGaO2, Li2GeO3, Li2B4O7 and LiNbO3 a mechanism of pyroelectric luminescence is proposed. Series of experiments were undertaken attaching a scintillating phosphor ScPO4 to a pyroelectric crystal and subjecting a pair of the bounded crystals to cooling/heating process. Pyroelectric activity causes not only pyroluminescence in pyroelectric crystals but also luminescence in a ScPO4, which is characterized with high intensity and kinetic and spectral properties typical for the intrinsic luminescence of a scintillator.

Spontaneous Cell Luminescence and Oxidative Metabolism

Spontaneous Cell Luminescence and Oxidative Metabolism

Insights into Excitonic Dynamics of Terpolymer-Based High-Efficiency Nonfullerene Polymer Solar Cells: Enhancing the Yield of Charge Separation States.

Ternary copolymerization strategy is considered an effective method to achieve high-performance photovoltaic conjugated polymers. Herein, a donor-acceptor1-donor-acceptor2-type random copolymer, named PBDTNS-TZ-BDD (T1), containing one electron-rich unit alkylthionaphthyl-flanked benzo[1,2-b/4,5-b'] di-thiophene (BDTNS) as D and two electron-deficient moieties benzo[1,2-c/4,5-c']dithiophene-4,8-dione (BDD) and fluorinated benzotriazole as A, was synthesized to investigate the excitonic dynamic effect. Also, the D-A-type alternating copolymer PBDTNS-BDD (P1) was also prepared for a clear comparison. Although the UV-Vis spectra and energy levels of P1 and T1 are similar, the power conversion efficiencies (PCEs) of the related devices are 11.50% (T1/ITIC) and 8.89% (P1/ITIC), respectively. The reason for this is systematically investigated and analyzed by theoretical calculation, photoluminescence, and pump-probe transient absorption spectroscopy. The density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculation results show that the terpolymer T1 with a lower exciton binding energy and a longer lifetime of spontaneous luminescence can synergistically increase the number of excitons reaching the donor/acceptor interface. The results of the pump-probe transient absorption spectroscopy show that the yield of charge separation of T1/ITIC is higher than that of the P1/ITIC blend film, and improved PCE could be achieved via copolymerization strategies. Moreover, the fabrication of the T1-based device is also simple without any additive or postprocessing. Therefore, it provides a promising and innovative method to design high-performance terpolymer materials.

Dependence of the Spontaneous Luminescence Intensity in ZnO Nanorods on their Length

The influence of the length of ZnO nanorods (500 nm in diameter) on the mode structure and spontaneous luminescence in the ultraviolet spectral region is studied by optical luminescence microscopy. It is shown that individual nanorods with a metal mirror on one face exhibit only two or three laser modes in the case of short nanocavity lengths (8–30 μm). Different values of the optical losses of the longitudinal and transverse waveguide modes are established for a ZnO nanorod lying on a glassy substrate. The quadratic dependence of the spontaneous luminescence intensity on the rod length can be attributed to improvement of the optical quality factor Q of bound longitudinal modes of light within longer rods (the Purcell effect).

Anti-Stokes Ultraviolet Luminescence and Exciton Detrapping in the Two-Dimensional Perovskite (C6H5C2H4NH3)2PbCl4.

Recently, it has been found that low-dimensional organometallic halide perovskites can be adopted as nonlinear monolayer emitters because of their efficient spontaneous anti-Stokes visual luminescence under visual or near-infrared laser excitation. Herein, we demonstrate a luminescence up-conversion process from the visible self-trapped exciton (STE) to an ultraviolet (UV) free exciton (FE) in the two-dimensional perovskite (C6H5C2H4NH3)2PbCl4 quantum wells excited by nanosecond pulse laser excitation. An ultraviolet 347 nm near-band-edge FE emission is obtained under the excitation of 579 nm dye laser at 10 K by a two-step, two-photon absorption process from the real intermediate exciton state. In addition, the decay rise time of higher-laying states of STE indicates the excitonic detrapping procedure could occur by the annihilation of phonons. Our results suggest that the low-dimensional halide perovskites with deformable structure are able to be applied in visible light-pumped UV-emitting devices.

Optical Method of Measuring the Temperature of Fluoride Crystals Activated by Yb3+ and Tm3+ Ions

The fluorescence intensities ratio (FIR) method is applied for measuring the temperature inside the luminescent LiY0.8Yb0.2F4:Tm3+ crystal. The obtained results are used for monitoring of the sample temperature in the experiment when the exciting radiation waist is shifted by the focusing lens inside the sample. It is shown that a considerable change in the luminescence intensity of the LiY0.8Yb0.2F4:Tm3+ crystal (0.2%) is not accompanied by a significant change in the temperature. This verifies the hypothesis about the appearance of amplified spontaneous luminescence (ASL) of Yb3+ ions during intense laser pumping in these crystals.

Size-dependent luminescence kinetics of rare-earth Er3+ ions in Y2O3 nanospheres

The luminescence kinetics of Er ions in Y2O3:Er nanospheres with diameters of 75–270 nm has been studied. A pronounced decrease in the luminescence decay times for Er3+ ion transitions in the green-red visible range is observed with increasing diameter up to 270 nm, unlike near-infrared emission at ∼1.5 μm. This finding is attributed to the appearance of photonic modes accelerating spontaneous luminescence, which is confirmed by a model calculation of bound optical states in the studied nanospheres.

Research and application of electroscope identification for UHV transmission and transformation equipment based on electrochromic materials

At present, due to the relatively large insulation gap of UHV(Ultra High Voltage) equipment, the traditional hand-held capacitive electroscope is difficult to operate; the non-contact electroscope is mainly based on the principle of electromagnetic induction, and the reliability is poor in complex areas such as substations and other electromagnetic environments. The power verification problem of AC/DC UHV transmission and transformation equipment has not been effectively solved. In order to optimize and solve the above problems, this research conducts performance testing and reliability analysis for new inorganic electrochromic materials, and uses the color change of inorganic materials to indicate the electrification state of power transmission and transformation equipment, thereby realizing the electricity inspection function. In this project,ZnS Electro-luminescent materials and GaN luminescent materials were prepared, which were packaged into electroscope identification, and the application scheme of electroscope identification on UHV power transmission and transformation equipment was determined. The field practice shows that the electroscope identification prepared by this project can realize spontaneous luminescence discoloration in the electric field, and can effectively indicate the charging state of the equipment, and the effect is very obvious. Thereby effectively solving the problem of power inspection of UHV power transmission and transformation equipment.The economic and social benefits are huge and the application prospects are wide.

Зависимость интенсивности спонтанной люминесценции наностержней ZnO от их длины

AbstractThe influence of the length of ZnO nanorods (500 nm in diameter) on the mode structure and spontaneous luminescence in the ultraviolet spectral region is studied by optical luminescence microscopy. It is shown that individual nanorods with a metal mirror on one face exhibit only two or three laser modes in the case of short nanocavity lengths (8–30 μm). Different values of the optical losses of the longitudinal and transverse waveguide modes are established for a ZnO nanorod lying on a glassy substrate. The quadratic dependence of the spontaneous luminescence intensity on the rod length can be attributed to improvement of the optical quality factor Q of bound longitudinal modes of light within longer rods (the Purcell effect).

Оптический метод измерения температуры фторидных кристаллов, активированных ионами Yb-=SUP=-3+-=/SUP=- и Tm-=SUP=-3+-=/SUP=-

AbstractThe fluorescence intensities ratio (FIR) method is applied for measuring the temperature inside the luminescent LiY_0.8Yb_0.2F_4:Tm^3+ crystal. The obtained results are used for monitoring of the sample temperature in the experiment when the exciting radiation waist is shifted by the focusing lens inside the sample. It is shown that a considerable change in the luminescence intensity of the LiY_0.8Yb_0.2F_4:Tm^3+ crystal (0.2%) is not accompanied by a significant change in the temperature. This verifies the hypothesis about the appearance of amplified spontaneous luminescence (ASL) of Yb^3+ ions during intense laser pumping in these crystals.

Broadband Spontaneous and Stimulated Luminescence of Heavily Doped AlxGa1 – xN Structures

The spectral characteristics of spontaneous and stimulated luminescence of heavily silicon-doped AlxGa1 – xN structures with the concentration nSi > 1020 cm–3 are studied with pulsed optical pumping at λ = 266 nm. The resulting dominant broadband radiation with a full width at half maximum of ~150 nm covers the whole visible spectral region. The radiation spectrum from the end of the structure is split into narrow components determined by the mode structure of the planar waveguide formed. The results indicate the stimulated character of the radiation. The optical gain for different structures fall in the range 20–70 cm–1.