Decrease In Emission Intensity Research Articles

Time-Resolved and Temperature-Dependent Fractional Amplitude Contributions to the Broadband Emission of CdSe Quantum Dots

The broadband spontaneous emission of excitons in CdSe quantum dots (QDs) is of great interest for the spectral imaging of living organisms or specific substances in the visible spectral region as well as in the biological optical window near the infrared spectral region. Semiconductor QDs that are near the bulk Bohr radius exhibit wide spectral tunability and high color purity due to quantum confinement of excitons within the dot boundary. However, with reducing dot size, the role of the surface-trapped state increases. The temperature-dependent photoluminescence (PL) confirms this with a ~3:1 emission intensity decrease from the surface-trapped state compared to the band edge. Large crystal irregularity, dangling ions, and foreign molecules can introduce new electronic transitions from surface-trapped states that provide broad spontaneous emission in the spectral region from visible to near IR in addition to the band edge emission. The time-resolved PL analyzed the fractional contributions of band edge, surface-trapped states, and possible intermediate trapped states to the broad spectral emission in order to characterize the CdSe QDs.

Effect of Co concentration and temperature on the energy transfer process between Mn2+ and Co2+ ions in Zn0.99-xMn0.01CoxTe nanocrystals

In this paper, we report a P2O5 – ZnO – Al2O3 – BaO – PbO glass system study, nanostructured with Zn0.99-xMn0.01CoxTe nanocrystals (NCs), synthesized by a fusion method. Transmission electron microscopy (TEM) images confirm the formation and electron paramagnetic resonance (EPR) spectra confirm the substitutional incorporation of Mn2+ and Co2+ ions in these NCs. The overlap between the Mn2+ ion emission bands and the Co2+ ion absorption bands suggests that an efficient resonance energy transfer from Mn2+ to Co2+ ions can be expected in these NCs. Indeed, the increase in emission intensity of Co2+ ions and the decrease in emission intensity of Mn2+ ions, as well as the decrease in lifetime emission of Mn2+ ions, with increasing cobalt concentration, confirm the nonradiative energy transfer from Mn2+ to Co2+ ions. On the other hand, temperature dependent measurements show the thermally activated energy transfer process via carriers of the lower energy states for those of the low energy.

Study of well-aligned Ag@ZnO nanoflower arrays with growth, photoluminescence and ultrafast nonlinear absorption properties

ZnO nanoflowers (NFs) and silver-decorated ZnO ([email protected]) NFs arrays were prepared by two/three-step progress of magnetron sputtering, hydrothermal and magnetron sputtering method, respectively. The effect of silver nanoparticles (NPs) on the visible emission performance of ZnO arrays was described. The results show that the ultraviolet emission (UVE) peak of ZnO NFs array is concentrated at 380 nm red-shifted to longer wavelength after being decorated with Ag NPs in the diameter of 18–50 nm. It is very interesting that the intensity of the visible emission (VE) is enhanced by the VE ratio of 1.43 for the [email protected] NFs arrays of 0.03 mol/L. However, for the [email protected] NFs arrays of 0.015 mol/L, the UVE peak blue shift from 387 nm to 384 nm, indicating a slight decrease in emission intensity due to the decorating Ag NPs of 10–20 nm. The enhancement of VE is considered as the synergistic effect of competition between the increase of exciton concentration and the enhancement of Ag NPs local field. The Z-scan measurement of the opening was performed at 800 nm, revealing the contribution of metal NPs. [email protected] NFs arrays with remarkable nonlinear optical properties are a potential nanomaterial for the development of multifunctional optoelectronic devices.

Electrical and magnetic properties of nanostructured Ni doped CeO2 for optoelectronic applications

Employing hydrothermal technique, undoped and nickel doped cerium oxide nanoparticles (Ni doped CeO2 NPs) are synthesized with different concentration of dopant (5 M%, 10 M% and 15 M%). Prepared samples are subjected to Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), High resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), Ultraviolet–visible spectroscopy (UV–vis), Photoluminescence spectroscopy (PL), Vibrational sample magnetometry (VSM), Dielectric and electrical conductivity studies. Formation of CeO2 NPs and Ni doped CeO2 NPs is confirmed by PXRD and EDX. The crystallite size of the samples, determined from powder XRD using Williamson-Hall (W–H) plot, diminishes with increased Ni doping. The lattice parameter variation indicates an initial lattice contraction when the doping is less and a lattice expansion with enhanced Ni doping. These variations in crystallite size and lattice parameter could be due to the replacement of Ce ions by Ni ions in the CeO2 lattice. SEM and HRTEM images show that the morphology of the NPs formed is nearly spherical. The UV–vis spectroscopic studies indicated that bandgap energy of Ni doped CeO2 NPs widens as the Ni dopant concentration is increased. Increase of oxygen vacancy (VO) with increase in Ni concentration is designated by Raman spectra. The PL studies show that the nanoparticles of CeO2 and Ni doped CeO2 exhibit luminescence in the violet-blue-green wavelengths region (400 nm–500 nm). The decrease in emission intensity with increase of Ni concentration is indicative to increase of oxygen vacancies with increase in Ni content which act as non-radiative centers. VSM studies show that all the samples exhibit paramagnetism. The saturation magnetization and the retentivity of the samples increase as the Ni dopant concentration increases. All the samples display frequency dependent dielectric properties. With increase in the concentration of Ni dopant and frequency, a reduction in the values of dielectric constant and dielectric loss and an improvement in the electrical conductivity were observed for all the samples.

Environmental benefit gain from exporting: Evidence from Vietnam

AbstractLarge‐scale trade reforms in developing countries over the past decades, while boosting economic growth, have raised concerns about deteriorating environmental quality. This paper examines whether participating in export markets affects a firm's energy and emission intensity. Using Vietnamese manufacturing firm‐level data over the period 2009–2014, this study finds that upon entering into the export markets, firms reduce their energy intensity by 27%. Furthermore, along with this energy efficiency gain, there is a decrease in emission intensity by roughly 31%–32%. Moreover, these reductions persist in subsequent periods. A possible mechanism for this is that strict requirements for product quality from buyers in high‐income regions drive firms to use higher‐quality inputs and/or invest in cleaner technology.

Anion-Responsive Manganese Porphyrin Facilitates Chloride Transport and Induces Immunogenic Cell Death

Anion-Responsive Manganese Porphyrin Facilitates Chloride Transport and Induces Immunogenic Cell Death

Chromone functionalized pyridine chemosensor for cupric ions detection

A new Schiff base 2-ethoxy-3-{[(6-{[(2-ethoxy-4-hydroxy-2H-chromen-3-yl)methylidene]amino}pyridine-2-yl)imino]methyl}–2H-chromen-4-ol (CD) was synthesized as a result of the condensation of 2,6-diaminopyridine and 3-formyl chromone in 1:2 M ratio and used for cupric ions detection and characterized through FTIR, HRMS and 1H NMR spectral techniques. The sensing capability of Schiff base for cupric ions as compared to other transition metal ions was examined by absorbance and emission studies. A considerable decrease in emission intensity appeared in Schiff base in the case of cupric ions while irrelevant changes were examined for the rest of the ions. The binding stoichiometry was obtained as 1:2 for CD: Cu2+ complex intended from the job’s plot which was confirmed through HRMS spectral technique. DFT calculations were carried for the confirmation of structural relationships and absorption–emission data. The Regression coefficient, Limit of detection, and Association constant were obtained as 98.7%, 1.2 × 10-6 M, and 3.26 × 104 M−1 respectively using Benesi-Hildebrand (B-H) equation. The sensing power of Schiff base CD to recognize cupric ions was unaltered by the addition of the rest of metal ions, which was authenticated through interference studies. Schiff base CD and its complex with cupric ions were found stable over an extensive time period as revealed by time-reliant studies. The data collected by pH studies revealed that the preferred pH range for detecting cupric ions by Schiff base CD was 6 to 11. The Schiff base was finally utilized for sensing cupric ions in a variety of spiked samples of water like canal water, tap water, groundwater, distilled water.

Lactational performance, rumen fermentation, and enteric methane emission of dairy cows fed an amylase-enabled corn silage

This study investigated the effects of an amylase-enabled corn silage on lactational performance, enteric CH4 emission, and rumen fermentation of lactating dairy cows. Following a 2-wk covariate period, 48 Holstein cows were blocked based on parity, days in milk, milk yield (MY), and CH4 emission. Cows were randomly assigned to 1 of 2 treatments in an 8-wk randomized complete block design experiment: (1) control corn silage (CON) from an isogenic corn without α-amylase trait and (2) Enogen hybrid corn (Syngenta Seeds LLC) harvested as silage (ECS) containing a bacterial transgene expressing α-amylase (i.e., amylase-enabled) in the endosperm of the grain. The ECS and CON silages were included at 40% of the dietary dry matter (DM) and contained, on average, 43.3 and 41.8% DM and (% DM) 36.7 and 37.5% neutral detergent fiber, and 36.1 and 33.1% starch, respectively. Rumen samples were collected from a subset of 10 cows using the ororuminal sampling technique on wk 3 of the experimental period. Enteric CH4 emission was measured using the GreenFeed system (C-Lock Inc.). Dry matter intake (DMI) was similar between treatments. Compared with CON, MY (38.8 vs. 40.8 kg/d), feed efficiency (1.47 vs. 1.55 kg of MY/kg of DMI), and milk true protein (1.20 vs. 1.25 kg/d) and lactose yields (1.89 vs. 2.00 kg/d) were increased, whereas milk urea nitrogen (14.0 vs. 12.7 mg/dL) was decreased, with the ECS diet. No effect of treatment on energy-corrected MY (ECM) was observed, but a trend was detected for increased ECM feed efficiency (1.45 vs. 1.50 kg of ECM/kg of DMI) for cows fed ECS compared with CON-fed cows. Daily CH4 emission was not affected by treatment, but emission intensity was decreased with the ECS diet (11.1 vs. 10.3 g/kg of milk, CON and ECS, respectively); CH4 emission intensity on ECM basis was not different between treatments. Rumen fermentation, apart from a reduced molar proportion of butyrate in ECS-fed cows, was not affected by treatment. Apparent total-tract digestibility of nutrients and urinary and fecal nitrogen excretions, apart from a trend for increased DM digestibility by ECS-fed cows, were not affected by treatment. Overall, ECS inclusion at 40% of dietary DM increased milk, milk protein, and lactose yields and feed efficiency, and tended to increase ECM feed efficiency but had no effect on ECM yield in dairy cows. The increased MY with ECS led to a decrease in enteric CH4 emission intensity, compared with the control silage.

Dual-Responsive Thermally Activated Delayed Fluorescence of Spiropyran Derivatives

Dual-Responsive Thermally Activated Delayed Fluorescence of Spiropyran Derivatives

The effect of self-absorption compensation methods on the quantitative analysis of soil samples using Laser-induced breakdown spectroscopy

When the detection of heavy metal elements in the soil was conducted using Laser-induced breakdown spectroscopy (LIBS), the accuracy of the calibration model can be affected by the self-absorption effect. In this work, the piecewise fitting and the least square support vector machine (LSSVM) were used to reduce the influence of self-absorption effect on quantitative analysis of the Cr element in the soil. With the increase of the Cr element content, the increased rate of the Cr element emission intensity decreases using internal standard method under the best conditions. The non-linear relationship exists between the content of the Cr element and the emission intensity of the Cr element, which reduces the accuracy of the quantitative analysis. Hence, the self-absorption coefficient (SA) was evaluated. The results showed that the self-absorption effect becomes more and more serious with the increase of element content. Therefore, the piecewise fitting and the LSSVM algorithm were used to establish calibration model. The correlation coefficients of the calibration model based on piecewise fitting were 0.9918, 0.9787 and 0.9655, respectively. The root mean square error (RMSE) and mean relative error (MRE) of the calibration model of piecewise fitting were 1.2853 wt% and 15.64%, respectively. Compared with the piecewise fitting calibration model, the LSSVM calibration model performed best, with an overall correlation coefficient of 0.9902, RMSE and MRE of 0.3878 wt% and 8.9926%, respectively. The results indicated that the LSSVM algorithm can be used as a method of reducing the influence of the self-absorption effect on the calibration model.

Sr3LiTaO6:xMn4+ red-emitting phosphors for indoor plant growth lighting: High thermal stability and quantum efficiency

A series of Sr3LiTaO6:xMn4+ red-emitting phosphors were synthesized by high temperature solid-state method for the first time. The samples were characterized using XRD, SEM, PLE, PL, UV–vis spectra, and internal quantum efficiency (IQE). The Sr3LiTaO6:0.2%Mn4+ phosphor exhibited a strong emission peak at 695 nm with a maximum IQE of 61.46%, which is suitable for use in indoor plant application. The intense excitation band of the phosphor located at the near ultraviolet region, which can match well with the emission of commercial ultraviolet LED chip. Moreover, the CIE chromaticity coordinate of Sr3LiTaO6:0.2%Mn4+ phosphor is (0.730, 0.270), which falls in deep red range with a color purity of 98.7%. The Sr3LiTaO6:0.2%Mn4+ phosphor also showed a good thermal stability with an emission intensity decrease of only 23.3% at 423 K from that at 289 K (I423K/I289K=76.7%). Finally, a LED device was fabricated for light supplement on wheat, showing an obvious improvement on the content of chlorophyll. It shows that the optimized phosphor may have a good potential for the application in indoor plant growth lighting LEDs.

Laser-induced breakdown in liquid water: Influence of repeated laser pulses on plasma formation and emission

We have experimentally investigated the influence of repeated laser pulses on laser-induced breakdown (LIB) in water following a focused 1064 nm laser pulse, for repetition rates between 0.5 and 20 Hz and up to 100 pulses. LIB plasma image data are collected as a function of repetition rate and laser pulse number, using an intensified CCD camera with sub-nanosecond camera-laser timing. Each pulse induces multiple breakdowns, shockwaves, and macroscopic cavitation bubbles. These effects disappear by the time the next pulse arrives. Even so, we find that the water target retains effects from previous pulses that persist up to roughly a second and that modify subsequent LIB properties including plasma location, spatial extension, and total emission intensity. We quantify the effects by tracking the first moment of the plasma emission intensity, which we call the “center of intensity” (CoI). Three distinct reproducible repetition-rate-dependent phases are identified with repeated pulses. In particular, (1) with initial pulses, emission intensity decreases and the CoI broadens and propagates downstream from the laser focus reaching a maximum axial distance away from the focal point, (2) with additional pulses, the CoI narrows and travels back upstream toward the laser, and (3) with continued pulses, the plasma gains back a portion of the lost intensity and the CoI reaches a steady state position, not at the focal point. Two possible causal effects are highlighted; particle inclusion concentration changes and microbubbles in the laser path.

Detection of truncated isoforms of human neuroserpin lacking the reactive center loop: Implications in noninhibitory role.

Neuroserpin is a serine protease inhibitor expressed mainly in the brain and at low levels in other tissues like the kidney, testis, heart, and spinal cord. It is involved in the inhibition of tissue plasminogen activator (tPA), plasmin, and to a lesser extent, urokinase-type plasminogen (uPA). Neuroserpin has also been shown to plays noninhibitory roles in the regulation of N-cadherin-mediated cell adhesion. It is involved in neuroprotection from seizure and stroke through tPA-mediated inhibition and also through its other protease targets. Mutations in critical domains of neuroserpin lead to its polymerization and neuronal death. In this study, a novel truncated isoform of human neuroserpin was identified in the brain and liver, which was confirmed by reverse transcriptase-PCR and DNA sequencing using exon-specific primers. Structural characterization of novel isoform using MD simulations studies indicated that it lacks the reactive center loop (RCL) but largely maintains its secondary structure fold. The novel truncated variant was cloned, expressed, and purified. A comparative intrinsic fluorescence and 4,4'-bis-1-anilino naphthalene 8-sulfonate studies revealed a decrease in fluorescence emission intensity and a more exposed hydrophobic surface as compared to the reported isoform. However, the novel isoform has lost its ability for tPA inhibition and complex formation. The absence of RCL indicates a noninhibitory role for the truncated isoform, prompting a detailed search and identification of two smaller isoforms in the human brain. With indications of the noninhibitory role of neuroserpin, identifying novel isoforms that appear to be without the tPA recognition domain is significant.

Moving in the Right Direction: Consumption-Based Projection Shows an Earlier and Lower Peak in Global Anthropogenic GHG Emissions

Projections of future emissions based on current trends are vital to assess the performance of mitigation efforts and to devise mitigation strategies. Several studies have investigated the aspiration gap between projected emissions and global warming targets, but it is as yet uncertain how changes in consumption patterns may impact trajectories. Here we employ a Markov Chain Monte Carlo (MCMC) Bayesian analysis of historical and projected consumption-based emissions during 1995-2050 via a modified Kaya identity. We assume regional convergence over time after finding strong supporting historical evidence. We find global emissions of 27-62 GtCO2eq yr-1 by 2050, slightly higher than SSP1-2.6 and encompassing SSP4-6.0, resulting in 1.9-2.4°C of warming above pre-industrial levels mid-way through the century. The median projection shows a 2024 peak of 55 GtCO2eq yr-1 and an annual average decrease of 0.58 GtCO2eq thereafter. Future emission decreases result from the interplay between a rapid reduction driven by decreasing emission intensities, especially in housing, and the change of final demand structure (-53 GtCO2eq yr-1) against increases from economic and population growth (+44 GtCO2eq yr-1). Compared to other work, we find an earlier peak which is lower in magnitude. This is due to the inclusion of recent data, the consideration of regional convergence, and the incorporation of structural changes in final demand as explanatory variables. This highlights the importance in continually updating projections and considering models that reflect convergence and demand structure changes, in order to better inform climate policy.

Greenhouse gas emissions intensity of food production systems and its determinants.

It is estimated that about 1/4th of all greenhouse gas (GHG) emissions may be caused by the global food system. Reducing the GHG emissions from food production is a major challenge in the context of the projected growth of the world’s population, which is increasing demand for food. In this context, the goal should be to achieve the lowest possible emission intensity of the food production system, understood as the amount of GHG emissions per unit of output. The study aimed to calculate the emission intensity of food production systems and to specify its determinants based on a panel regression model for 14 countries, which accounted for more than 65% of food production in the world between 2000 and 2014. In this article, emission intensity is defined as the amount of GHG emissions per value of global output. Research on the determinants of GHG emissions related to food production is well documented in the literature; however, there is a lack of research on the determinants of the emission intensity ratio for food production. Hence, the original contribution of this paper is the analysis of the determinants of GHG emissions intensity of food production systems. The study found the decreased of emission intensity from an average of more than 0.68 kg of CO2 equivalent per USD 1 worth of food production global output in 2000 to less than 0.46 in 2014. The determinants of emission intensity decrease included the yield of cereals, the use of nitrogen fertilizers, the agriculture material intensity, the Human Development Index, and the share of fossil fuel energy consumption in total energy use. The determinants of growth of emission intensity of food production systems included GDP per capita, population density, nitrogen fertilizer production, utilized agriculture area, share of animal production, and energy use per capita.

Spectral investigation of lithium-telluride based glasses doped with Sm3+-ions for lighting application

Glasses with compositions TeO2-BaO-Li2O-GeO2:Sm2O3 were prepared by melt-quenching technique and labeled by TBaLG-Sm. In this study, we report their radiative, physical, optical and luminescence properties. In the emission spectra, four emission peaks were observed at 563 nm, 599 nm, 645 nm, 707 nm wavelengths with corresponding transitions as 4G5/2→6H5/2, 4G5/2→6H7/2, 4G5/2→6H9/2 and 4G5/2→6H11/2, respectively. Up to 1.0 mol% of Sm3+-ion concentration the emission intensity increases, followed by decreasing with further increasing Sm3+-ion content. A non-radiative energy transfer via cross-relaxation channels between Sm-Sm ions is the main cause of decrease in emission intensity. Computing from the absorption and emission spectra, the Judd-Ofelt parameters, radiation transition probability, spectroscopic quality factors and emission cross section were evaluated. The color coordinates of all samples lie in the orange region of the Commission International de lˊEclairage diagram. The large values of branching ratios and stimulated emission cross-section reveal that the studied glass con be used as a lasing material and a lighting device.

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

An insight into the binding behavior of graphene oxide and noble metal nanoparticles

The binding behavior of graphene oxide and metal nanoparticles (Au, Pt, and Pd) was observed by UV–Vis spectroscopy, fluorescence spectroscopy, dynamic light scattering, and zeta potential. Hybrids with a fixed concentration of graphene oxide (GO) were prepared with increasing concentration of metal nanoparticles to observe the effect of binding on their spectroscopic properties, size, and zeta potential. An increase in the absorption spectra of GO after binding with nanoparticles and a gradual decrease in fluorescence emission intensity with increasing concentration of nanoparticles was observed, representing their effective binding. Stern–Volmer plots differentiated the quenching constants of these nanoparticles, where Au shows the lowest and Pd shows the highest quenching among these nanoparticles. The initial hybrids showed more size change as compared to hybrids with a higher concentration of nanoparticles, whereas initial hybrids have charge similar to that of GO and gradual increase in the concentration of nanoparticles bring the charge near to the respective charge of nanoparticles. To the best of our understanding, this is the first report of its kind to study the binding interactions of two different moieties by studying changes occurred in the hydrodynamic radius and zeta potential of hybrids by titration experiments, having applications in surface treatment, drug delivery, and as sensors for environmental pollutants or other classes of organic molecules, etc.

Enhancement of photo luminescent and magnetic properties of surface modified zinc sulphide nanoparticles by manganese doping

In the current paper we have reported the structural, optical and magnetic properties of manganese doped (1% to 10%) zinc sulphide nanoparticles synthesised by simple chemical co-precipitation method at room temperature. The crystal structure of the synthesised nanoparticles has been confirmed by X-ray diffraction and the average crystallite size calculated by Scherrer formula was about 3.0 nm. A slight quenching in the crystallite size with the doping was also observed. The FESEM images showed spherical shape particles with uniform size distribution. The elemental composition of pure and manganese doped zinc sulphide was confirmed by EDAX attached to FESEM. The UV-Vis spectra has an absorption edge at 321 nm with sharp fall in the absorption confirming the particles of uniform size distribution with no shift in the absorption edge with the doping. The band gap widening was observed (4.4 eV) and the particle size (3.4 nm) calculated was by effective mass approximation. The photoluminescence spectra has wide emission spectra with the peaks at 397 nm, 414 nm and 487 nm with increase in the intensity with the doping concentration giving a peak at 1% of doping and decrease in emission intensity after that. The hysteresis curve shows the ferromagnetism and the saturation magnetisation increases with the doping concentration.

Impacts of urbanization on carbon emissions: An empirical analysis from OECD countries

The impacts of urbanization on carbon emissions have attracted widespread attention for a long time. Quantitative research on the impacts is of great significance for formulating carbon reduction policy. Based on the dynamic panel autoregressive distribution lag (ARDL) model, we systematically study the general and heterogeneous long-run equilibrium relationships, short-run dynamic relationships, impact mechanism and lag effect between urbanization and three carbon emission dimensions in OECD high-income countries during long period. The main empirical results indicate that developed countries tend to have the same negative impacts of urbanization on carbon emissions, although there are differences in the endowments of different countries. The impact is relatively weak, for each percentage point increase in urbanization rate, CO 2 emissions per capita decrease by 0.015%, total CO 2 emissions decrease by 0.012%, and CO 2 emission intensity decrease by 0.009%. All member countries have achieved the decoupling of urbanization and carbon emissions. Urbanization affects carbon emissions by affecting economic growth, energy efficiency, and final energy consumption structure. This paper further reveals the multi-level impacts of urbanization on carbon emissions and provides policy implications of achieving carbon reduction through urbanization's agglomeration effect for government decision makers. • Estimate the impact of urbanization on carbon emissions based on panel ARDL model. • Analyze general & heterogeneous long-, short-run relationship and impact mechanism. • Urbanization decreases carbon emissions but the impact is weak in OECD countries. • Developed economies have achieved the decoupling of urbanization and CO 2 emissions. • Promote urbanization process and exert its scale effect to reduce carbon emissions.