Increase In Emission Intensity Research Articles

Core@shell strategies to enhance green upconversion emission of LaAlO3:ErIII, YbIII nanoparticles

Seeking enhanced luminescence in upconverter nanoparticles, LAO:ErIII0.01, YbIII0.01, LAO = LaAlO3, with an average diameter of 30–40 nm, was synthesized via a modified Pechini method. Two coating strategies were employed: the first with three layers of 1 % LAO, and the second with LAO:NdIIIx at% (x = 10 or 30) or LAO:NdIIIx at%, YbIIIy at% (x, y = 30, 2 or 30, 20). Characterization included FTIR, UV–Vis diffuse reflectance, TEM, XRD, and photoluminescence. In the first strategy, undoped phase coating maintained the LaAlO3 rhombohedral crystalline structure, enhancing ErIII core emission under 980 nm laser excitation. In the second case, the shell containing YbIII (3 or 20 at%) under laser at 808 nm, favored the increase in the relative emission intensity of the activator, exciting ErIII directly in the core or via the outer NdIII sensitizer. Kinetic measurements fixing excitation at 980 nm and emission at 542.5 nm resulted in ErIII excited state decay values between 56 and 68 μs. The doped shell favored increased excited state lifetimes, exhibiting concentration quenching in the 30 % YbIII condition. Both NdIII presence and its combination with YbIII enhanced green emission compared to the uncoated core. From thermometric studies, the successive depositions of inert layers of LAO contributed to the highest relative thermal sensitivity of 1.79 % K−1 at 305 K, among the systems studied. Therefore, the core@shell strategies were successful in intensifying ErIII emission, both in the green and red regions, and resulted in relevant figures of merit that qualify them for applications in nanothermometry in the biological window.

Spatial confinement offered by a blocker on the laser-induced breakdown spectroscopy of Ti plasma

Spatial confinement effects offered by a blocker on the laser-induced plasma parameters of titanium (Ti) are evaluated using the Optical Emission Spectroscopy technique. Nd:YAG (1064 nm, 10 ns) laser is used as an irradiation source. To observe the spatial confinement effects, an Al blocker at different distances of 4, 6, and 8 mm from the target is placed along the plume path. All the measurements are performed under the Ar environment at different pressures. It is observed that with increasing laser irradiance plasma parameters such as excitation temperature (Te) and electron number density (ne) increase, whereas it is vice versa true for increasing blocker distances. Without the blocker, the maximum values of Te and ne are about 7000 K and 1.4 × 1018 cm−3, respectively, at an Ar pressure of 50 Torr. A significant increase in emission intensity along with Te ≈ 9810 K and ne ≈ 2.2 × 1018 cm−3 is achieved in the presence of blocker. The results show that spatial confinement is responsible for the enhancement of Te and ne, which is attributed to the increased collisional frequency of plasma species after compression by shockwaves. The ablation pressure and shock pressure are also analytically evaluated and vary from 0.15 to 0.25 GPa and from 0.1 to 0.2 GPa, respectively, with increasing laser irradiance. With increasing blocker distances from 4 to 8 mm, the work done by reflected shockwaves to compress the plume varies from 0.02 to 0.002 mJ.

Characterizing urban GHG emissions based on land-use change—A case of Airport New City

Measuring greenhouse gas (GHG) emissions across different types of land is essential for urban planning during the transition to low-carbon cities. Urban land identification, based on remote sensing images and points of interest (POIs), has the potential to narrow down the statistical unit, helping achieve spatial visualization of GHG emissions below the city level and distinguish emission characteristics of different land-use types. Considering land type as a classification standard for GHG emissions, we constructed the modified STRIPAT-PLS model by identifying land-use types, reconstructing land-use GHG emissions (LUGEs) inventory, and extracting driving indexes, which calculated driving force and LUGEs that were missed in historical years. It deepened the depth and precision of GHG emissions research and provided a reference for LUGE reduction and land management below the city level where missing historical data on GHG inventories. The results showed that: 1) the modified STRIPAT-PLS model achieved a simulation accuracy of 94.9%, demonstrating the effectiveness of our research approach in depicting GHG emissions across different land-use types. 2) Land scale, socio-economic development, and industrial development were key factors that impacted agricultural land, residential land, and airport respectively. 3) Airport was the most significant carbon contributor, while industrial witnessed the highest growth in emission intensity; 4) the spatial analysis indicated decreasing differences in GHG emissions and an overall increase in emission intensity. In addition, the research proposed emission reduction priorities and strategies for each land type to promote low-carbon goals in airport cities.

Bright cyan emission from Eu-Doped borosilicate glasses by optimizing reduction of Eu3+ to Eu2+ in ambient atmosphere

Although substantial strides have been made in exploring the blue and red emissions of amorphous glass under near-ultraviolet excitation for LEDs purpose, the lack of the cyan emission heavily hinders the full spectra LED towards high-quality application. Addressing this cyan gap in white-light LED technology calls for the doping of Eu2+ as the doping center for its highly efficient luminescence. However, Eu3+ as an oxidation state of europium ions poses a critical challenge in effectively reducing to its reduction state. A popular method for reduction involves using mixed gases such as N2/H2 or CO gases in a reaction container, yet this approach brings about environmental pollution and increases production costs. In this work, we proposed a novel strategy that bright cyan emission can be achieved in Eu-doped borosilicate glasses by optimizing reduction of Eu3+ to Eu2+ in ambient atmosphere. It is observed a gradual increase in the band emission intensity associated with the reduced Eu2+, accompanied with a concurrent decrease in the sharp peak intensity linked with Eu3+ with the growing Si3N4 content. The effect of both melting temperature and synthesis time on reduction effect on the reduction of Eu3+ to Eu2+ ions were also investigated. It is revealed that either longer synthesis times or higher melting temperatures diminished the efficient reduction of Eu3+ to Eu2+ ions during the first-melting. Expanding on the Si3N4 reduction method, we employed an external bamboo charcoal approach to produce Eu-doped borosilicate glass under various synthesis times during the secondary melting. The results show that longer synthesis times attributed to the reduction effect. Finally, the optimized cyan-emitting glass sample is featured with emission wavelength of 486 nm, a transmittance of 84 %, and a quantum yield of 37.97 %. All the significant results are paving the solid way to prepare cyan-emitting glasses in the future.

Investigating the use of Er3+ doped β-Ca2SiO4 phosphors derived from agricultural waste for thermal sensing and forensic applications

Leveraging agricultural waste, Erbium (Er3+) doped β-Ca2SiO4 phosphors (β-CS:Er3+) with concentrations ranging from 1 to 9 mol % were developed using the solid-state reaction method. These β-CS:Er3+ samples underwent extensive characterization to examine their crystalline structure, surface morphology, photoluminescence (PL) properties, and thermal sensing capabilities. The PL emission, excited at 378 nm, prominently displayed a peak at 549 nm, indicative of the green emission primarily due to the 4S3/2 → 4I15/2 transition. An optimal concentration of Er3+ at 5 mol% (β-CS:5Er3+) is identified, showing peak luminescence intensity, whereas, higher concentrations led to a decrease in intensity because of concentration quenching (CQ) effects. Temperature-dependent photoluminescence (TDPL) analysis revealed an increase in emission intensity at 523 nm, while the peak at 549 nm exhibited a decrease in intensity within the temperature range of 303–463 K. Nevertheless, the emission peak at 549 nm demonstrates remarkable thermal stability at elevated temperatures, maintaining 79.32% of its emission intensity at 423 K. The optimized β-CS:5Er3+ phosphor exhibited its chromaticity coordinates (0.3152, 0.6631) in the green region under 378 nm excitation, alongside promising temperature sensing capabilities with a relative sensitivity of 2.80 % K−1. The application of these phosphors in a powder dusting technique for revealing latent fingerprints (LFPs) and latent lip prints (LLPs) under 365 nm UV light uncovered detailed ridge and groove patterns on various substrates. This approach, highlighting the phosphor's exceptional fluorescence, dual adherence, and non-interfering background, showcased its potential for enhanced forensic analysis. The thorough examination of LFPs and LPs under various conditions, including aging, heat, and UV exposure, confirms the β-CS:Er3+ NPs' suitability for cutting-edge display technologies and forensic methodologies.

Mg doping effect on the properties of SnO2 thin films synthesized by dip-coating method

Undoped and Mg doped SnO2 thin films were deposited on glass substrates using dip-coating method for the first time. X-ray diffraction analysis of the films revealed a tetragonal rutile phase. A decrease in crystallite size is observed as the Mg doping increases. The transmittance spectrum exhibits a decrease in transmittance from 87% to 62% as the Mg content is increased. The optical band gap narrows from 3.97 eV to 3.93 eV with the increasing of Mg content. MEB showed an increase of grain sizes with increase in Mg concentration. The RMS roughness increases with Mg doping content. FTIR showd O–Sn–O, Sn–OH, Mg–O, and OH–Mg–OH vibration modes. PL spectra indicated that the incorporation of more Mg2+ into the lattice of SnO2 creates additional oxygen vacancies, leading to an increase in the PL emission intensity in the films. A transition from n-type to p-type conduction was observed at 9 wt% Mg doping.

Characteristics and Formation Mechanism of Ozone Pollution in Demonstration Zone of the Yangtze River Delta, China

Emerging research indicates that ground-level ozone (O3) has become a leading contributor to air quality concerns in many Chinese cities, with the Yangtze River Delta (YRD) region facing particular challenges. This study investigated the characterization of air pollutants in Wujiang, which is located within the YRD demonstration zone, during the warm season (April–September) of 2022. The contributions of emission and meteorology to O3 were identified, the O3-NOX-VOC sensitivities were discussed, and the VOC sources and their contributions to O3 formation were analyzed. A random forest model revealed that the high O3 concentration was mainly caused by a combination of increased emission intensity due to the resumption of work and production after the COVID-19 pandemic, along with adverse meteorological conditions. The results revealed more than 92% of the pollution days were related to O3 during the warm season, and the impact of O3 precursor emissions was slightly greater than that of the meteorological conditions. O3 formation was in the VOC-limited regime, and emission reduction strategies targeting VOCs, particularly aromatics such as toluene and xylene, have been identified as the most effective approach for mitigating O3 pollution. Changes in O3-NOX-VOC sensitivity were also observed from the VOC-limited regime to the transitional regime, which was primarily driven by variations in the NOX concentrations. The VOC source analysis results showed that the contributions of gasoline vehicle exhaust and diesel engine exhaust (mobile source emissions) were significantly greater than those of the other sources, accounting for 20.8% and 16.5% of the total VOC emissions, respectively. This study highlights the crucial role of mobile source emission control in mitigating O3 pollution. Furthermore, prioritizing the control of VOC emission sources with minimal NOX contributions is highly recommended within the VOC-limited regime.

Characterization of Ce3+ and Eu3+ doped and co-doped ZnO nanoparticles for luminescence applications

This paper investigates the synthesis of Ce3+ and Eu3+ doped, as well as co-doped ZnO nanoparticles using the solution combustion route. The nanoparticles exhibit a hexagonal wurtzite structure of ZnO with crystallite sizes ranging from 19 to 22 nm. Structural parameters, including lattice constants, bond lengths, and bond angles, are evaluated. Morphological diversity is observed in field-emission scanning electron microscopy images. The diffuse reflectance spectroscopy results reveal an energy band gap of 3.20 eV for undoped ZnO nanoparticles. The energy band gap value slightly decreases for Eu-doped ZnO and certain (Ce, Eu) co-doped ZnO nanoparticles. Photoluminescence (PL) excitation peaks are attributed to energy levels of native defects in the ZnO band gap, along with f–d and f–f transitions of rare-earth ions (Ce3+, Eu3+). The PL emission spectra under different excitation wavelengths (350 nm, 394 nm, and 465 nm) display varied peak positions. ZnO co-doped with 0.96 mol% of Ce3+ and 0.92 mol% of Eu3+ emerges as a promising material for luminescence applications, exhibiting a significant increase in green emission intensity. Consequently, this study represents a novel contribution to the field of ZnO-based luminescent materials.

Enhancing electrical and optical properties in layered NaxCoO2 through sodium non-stoichiometry: Insights into surface band bending and oxygen vacancies

The concentration of sodium ions (Na+) in layered sodium cobaltite (NaxCoO2) is a pivotal determinant influencing its physical and chemical properties. This study focused on NaxCoO2 with varying sodium content (x = 1, 0.9, 0.7, 0.5, 0.3, 0.1) to establish a correlation between the sodium concentration and the substantial modulation of the structural and electrical properties. X-ray diffraction and Raman studies confirmed the formation of hexagonal structured NaxCoO2 prepared by the sol-gel method, while a reduction in Na content increased the percentage of the Co3O4 phase. Notably, as the Na content was lowered, the Raman peak shifted towards a lower wavenumber due to the lattice alignment along the c-axis of the crystal plane. Morphological analysis displayed the growth of distinct plate-like structures, with a thickness ranging from 10 to 15 μm, which gradually decreased on lowering Na content. X-ray photoelectron spectroscopy studies revealed an increase in the relative concentration of Co4+/Co3+ with a decrease in sodium content implying a lattice distortion in CoO6 octahedra which led to the creation of additional oxygen vacancies in Na0.7CoO2 (NCO7). Optical studies highlighted a band bending phenomenon in the NCO7, while photoluminescence studies indicated an increase in emission intensity, suggesting the presence of oxygen vacancies in NCO7. Electrical measurements demonstrated the highest conductivity for NCO7 emphasizing the significance of the optimal lattice distortion, generation of oxygen vacancies, and surface band bending effect for efficient charge carrier transportation. This study highlights the crucial role of the sodium ion content between the CoO2 layers in precise tuning of the structural, electronic structure/distortion, optical, and electrical properties of NaxCoO2. The insights gained particularly in optimizing the optical and electrical properties through sodium non-stoichiometry, may hold significant implications for diverse energy conversion and storage devices, catalysis, and even optoelectronics devices.

Effects of grain magnetic properties and grain growth on synthetic dust polarization of MHD simulations of low-mass Class 0/I YSOs

ABSTRACT Thermal dust polarization is a powerful tool to probe magnetic fields ($\boldsymbol{B}$) and grain properties. However, a systematic study of the dependence of dust polarization on grain properties in protostellar environments is not yet available. In this paper, we post-process a non-ideal MHD simulation of a collapsing protostellar core with our updated POLARIS code to study in detail the effects of iron inclusions and grain growth on thermal dust polarization. We found that superparamagnetic (SPM) grains can produce high polarization degree of $p \sim 10\!-\!40~{{\ \rm per\ cent}}$ beyond ∼500 au from the protostar because of their efficient alignment by magnetically enhanced radiative torque mechanism. The magnetic field turbulence in the envelope causes the decrease in p with increasing emission intensity I as p ∝ Iα with the slope α ∼ −0.3. But within 500 au, SPM grains tend to have inefficient internal alignment and be aligned with $\boldsymbol{B}$ by RATs only, producing lower $p \sim 1~{{\ \rm per\ cent}}$ and a steeper slope of α ∼ −0.6. For paramagnetic (PM) grains, the alignment loss of grains above $1\, {\mu \rm {m}}$ in the inner ∼200 au produces $p \lt \lt 1~{{\ \rm per\ cent}}$ and the polarization hole with α ∼ −0.9. Grain growth can increase p in the envelope for SPM grains, but cause stronger depolarization for SPM grains in the inner ∼500 au and for PM grains in the entire protostellar core. Finally, we found the increase of polarization angle dispersion function S with iron inclusions and grain growth, implying the dependence of B-field strength measured using the David–Chandrasekhar–Fermi technique on grain alignment and grain properties.

Development of Fluorescent Sensors for Biorelevant Anions in Aqueous Media Using Positively Charged Quantum Dots.

Quantum dots (QDs) have captured the attention of the scientific community due to their unique optical and electronic properties, leading to extensive research for different applications. They have also been employed as sensors for ionic species owing to their sensing properties. Detecting anionic species in an aqueous medium is a challenge because the polar nature of water weakens the interactions between sensors and ions. The anions bicarbonate (HCO3-), carbonate (CO32-), sulfate (SO42-), and bisulfate (HSO4-) play a crucial role in various physiological, environmental, and industrial processes, influencing the regulation of biological fluids, ocean acidification, and corrosion processes. Therefore, it is necessary to develop approaches capable of detecting these anions with high sensitivity. This study utilized CdTe QDs stabilized with cysteamine (CdTe-CYA) as a fluorescent sensor for these anions. The QDs exhibited favorable optical properties and high photostability. The results revealed a gradual increase in the QDs' emission intensity with successive anion additions, indicating the sensitivity of CdTe-CYA to the anions. The sensor also exhibited selectivity toward the target ions, with good limits of detection (LODs) and quantification (LOQs). Thus, CdTe-CYA QDs show potential as fluorescent sensors for monitoring the target anions in water sources.

Long-term management of rice agroecosystem towards climate change mitigation

The Intergovernmental Panel on Climate Change recognize to agriculture the responsibility for about 15 % of global anthropogenic greenhouse gas (GHG) emissions, contributing to global warming. The increasing nutrient inputs in industrial agriculture affect the GHG concentration in the atmosphere and varies substantially due to rate and type of fertilizers applied to the crops, making the management more or less sustainable. In this perspective, this study has investigated at small scale the effect of different adjusted agricultural management practices, based on different nutrient dosage, to optimize the effect of rice cropping systems on carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions. Farmyard manure (FYM), rice stubbles and Azolla integrated with chemical fertilizers have been correlated with microbial and enzymatic activities, and with different carbon and nitrogen fractions in acid Inceptisol. Results have revealed that the integrated nutrient management used in rice-rice agroecosystem yielded a peak for CO2 and CH4 emissions, whereas two peaks for N2O emission. This study has shown an increase in greenhouse gas emission intensity (GHGI) and grain yield of rice in the following order: rice stubbles > FYM > Azolla and it has confirmed CH4 emission as the dominant contributor to GHGI from the rice-rice agroecosystem. When analyzed together GHGs emission and soil properties, a positive correlation was found with biological properties as well as with the different carbon and nitrogen fractions in soil. The highest GHGI has been highlighted in the treatment where recommended dose of chemical fertilizers has been combined with rice stubbles, primarily due to the increase in CH4 emissions. In contrast, the lowest GHGI has been exhibited in Azolla treated plot, probably due to the cumulative effects of the photosynthetic rate of Azolla, the release of oxygen from the Azolla roots, and the physical protection capacity of the Azolla cover, which partially avoid the CH4 diffusion from the standing water. The seasonality did not affect the estimated rates of GHGI that have been lower both in case of winter and autumn rice compared to previous studies, probably for dissimilarities in management practices. Further research is required in other cropping sequences for addressing the ecological contribution of smallholder agriculture to help reducing GHG emissions, thus, mitigating global warming with actions at local scale.

Steady State and Time-Dependent Fluorescent Peptide Assays for Protein Kinases.

Protein kinases catalyze the phosphorylation of proteins most commonly on Ser, Thr, and Tyr residues and regulate many cellular events in eukaryotic cells, such as cell cycle progression, transcription, metabolism, and apoptosis. Protein kinases each have a conserved ATP-binding site and one or more substrate-binding site(s) that exhibit recognition features for different protein substrates. By bringing ATP and a substrate into proximity, each protein kinase can transfer the γ phosphate of the ATP molecule to a hydroxyl group of the target residue on the substrate. In such a way, signaling pathways downstream from the substrate can be regulated based on the phosphorylated versus dephosphorylated status of the substrate. Although there are a number of ways to assay the activity of protein kinases, most of them are technically cumbersome and/or are indirect or based on quenched reactions. This protocol describes an assay employing a fluorescent peptide substrate to detect phosphorylation by protein kinases in real time. The assay is based on the principle that the phosphorylation of the peptide substrate leads to an increase in the fluorescence emission intensity of an appended fluorophore. We extend the application of this assay to an example of how to assess time-dependent covalent inhibition of kinases as well. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Measuring protein kinase activity using fluorescent peptides Alternate Protocol: Measuring protein kinase activity using a fluorescence plate reader Support Protocol: Labeling peptides with sox fluorophore Basic Protocol 2: Measuring time-dependent ATP-competitive inhibition of protein kinases using fluorescent peptides.

Aggregation‐Induced Emission (AIE) of Au(I)‐GSH Complexes is Activated by Optical Manipulation and Exhibits Surprising 780 nm Emission

AbstractAn optical manipulation method to activate the aggregation‐induced emission (AIE) of Au(I)‐glutathione (Au(I)‐GSH) complexes is presented. First, the well‐known AIE‐type Au(I)‐GSH complexes with a solid emission wavelength of 570 nm are synthesized. At the beginning of the focusing a 1064 nm continuous‐wave (CW) laser at the interface of Au(I)‐GSH complexes solution, its luminescence is hardly detectable. However, with the extension of the laser irradiation time, aggregate appears and rapidly grows, and strong luminescence is shown, indicating the activation of AIE of Au(I)‐GSH complexes through optical manipulation. Surprisingly, the emission peak is at 780 nm and no blue‐shift is observed with the emission intensity increases. The activated AIE emission wavelength by optical manipulation is longer than reported previously, which means that optical manipulation activates AIE in a unique manner. The switching on/off of the activation of AIE is arbitrarily controlled by changing the laser power. In this paper, the luminescence phenomenon and mechanism of AIE are discussed from the perspective of the movement limitation of Au(I)‐GSH complexes under optical manipulation. It is of significant importance for further insights into the luminescence of Au(I)‐GSH complexes and their future development.

The impact of reducing trade barriers on enterprises' pollution emissions: Evidence from China

AbstractTrade and pollution are important issues for people's well‐being. However, less attention has been paid to the study of changes in international trade rules affecting the emission behavior of micro firms. This paper takes the quota restriction of the multi‐fiber arrangement (MFA) lifted as an exogenous impact and explores the impact of trade barriers reduction on pollution emissions of textile industries using the difference‐in‐differences (DID) method. The results show that (1) after the quota restriction of the MFA was lifted, the reduction of trade barriers increased the pollution emissions of the textile industry. The enterprises' SO2 emission intensity with trade barriers reduced increases by 8.1% compared to the industries with trade barriers that have not been reduced. (2) The impact of the trade barrier reduction on enterprises' pollution emissions varies with the type of enterprise ownership, export nature, and enterprise scale. For private enterprises, export enterprises, and large‐scale enterprises, the promotion effect of trade barrier reduction on enterprises' pollution emissions is more significant. (3) The mechanism test results show that the increase in SO2 emission intensity is mainly caused by the increase in the market share of enterprises, the deterioration of energy structure, and the increase in pollution output of enterprises. Therefore, it is critical to reduce enterprises' pollution emissions by maintaining a reasonable market share, optimizing energy structures, and increasing investment in pollution treatment equipment. This study reveals that changes in MFA international trade rules have profoundly influenced the production decision‐making behavior of companies in exporting countries, producing deep implications for enterprise pollution emission behavior and providing empirical evidence and management guidance for developing countries' development of environmentally friendly trade policies and responses to trade‐induced environmental pollution shocks.

Mapping deterioration in electrospun zein nonwoven nanostructures encapsulating corn oil

Electrospun nonwovens of biopolymers are gaining popularity in filtration, coatings, encapsulation, and packaging materials. However, their applications are hindered by limited stability, particularly when loaded with lipids. This research aimed to apply a multiscale approach to gain insights into deteriorative processes, e.g., oxidation, limiting the shelf life of these complex materials, using corn oil-loaded electrospun zein nonwovens as a model system. Oil-doped zein electrospun nonwovens were stored in the dark at 23 °C and 33% relative humidity for 28 days and tested at selected intervals to monitor their morphology and mechanical properties. Lipid oxidation was assessed using the thiobarbituric acid reactive species (TBARS) assay. The photophysical properties of intrinsic, i.e., tyrosine (Tyr), and extrinsic, i.e., boron-dipyrromethene undecanoic acid 581/591 (BODIPY C11), lumiphores were also monitored to evaluate changes in local molecular rigidity, and oxidation, respectively. The protein secondary structure was determined with Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) analysis of the oil-loaded electrospun nonwovens revealed that the diameter of the ribbon-like fiber significantly decreased during storage from 701 ± 23 nm to 620 ± 44 nm. Breakage of the electrospun fibers was observed and correlated with increased brittleness and molecular rigidity of the nonwoven material, reflected by an increase in Tyr emission intensity and phosphorescence lifetime. Changes in tensile strength, brittleness and matrix rigidity also correlated with a zein secondary structure transition from unordered to ordered β-sheets. Raman and luminescence micrographs showed oil migration during storage, thereby increasing lipid oxidation. The correlation between local rigidity and lipid distribution/oxidation suggests that reorganizing protein structures increased material brittleness and displaced encapsulated oils within the electrospun fiber. Understanding deteriorative mechanisms aids in developing innovative strategies to improve the stability of these novel food-grade materials.

Design of molecular sensors and switches based on luminescent ruthenium-terpyridine complexes bearing active methylene and triphenylphosphonium motifs as anion recognition sites: experimental and DFT/TD-DFT investigation.

Synthesis, characterization and thorough investigation of the photophysical and electrochemical properties of a new category of emissive homo- and heteroleptic Ru(II)-complexes derived from the [4'-(p-triphenylphosphonium methyl phenyl)-2,2':6',2''-terpyridine]bromide (tpy-PhCH2PPh3Br) ligand have been executed in this work. Incorporation of the PhCH2PPh3+Br- group at the terpyridine motif appropriately adjusts the triplet metal-to-ligand charge transfer (3MLCT) and metal-centered (3MC) excited states so that the complexes luminesce at room temperature (RT) having lifetimes within the range of 6.82-9.63 ns. The RT emission characteristics of the complexes get further enhanced via aggregation phenomena through the use of different solvent/non-solvent mixtures (DMSO/H2O and DMSO/PhCH3 mixtures). Temperature dependent emission spectral measurements indicate that the emission intensity, quantum yield and lifetime increase upon dropping down the temperature, thereby designated as the on-state, while the increase of temperature causes a reduction of the said properties, indicating the off-state and the process is fully reversible. Taking advantage of the active methylene group coupled with a phosphonium motif, anion sensing characteristics of the complexes are investigated systematically in DMSO through the use of various optical channels and spectroscopic tools. The complexes are very much sensitive to fluoride and to a lesser extent acetate and dihydrogen phosphate among the studied anions. In essence, the complexes function as sensors for temperature and fluoride ion. Computational investigations were also executed via density functional theory (DFT) and time-dependent (TD)-DFT to obtain a clear understanding of the electronic structures of the metalloreceptors, appropriate assignment of the spectral bands and their mode of interaction with selected anions.

White light emitting nanocrystalline Y1−xGdxPO4:Dy3+ and improved PLQY on Gd3+ co-doping

White Light emitting phosphors are in the realm of scientific evolution owing to their several superior photophysical features and maximum commercial reach. Here in this work we have carried out doping of Dy3+ in Y1-xGdxPO4 wherein we have moved from YPO4 to GdPO4 to harness the potential of dysprosium ion in achieving white light emission and correlating the structural evolution in these phosphates with luminescence properties. Y1-xGdxPO4:Dy3+ phosphor has been synthesized using co-precipitation method and characterized using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), time resolved photoluminescence (TRPL) and positron annihilation lifetime spectroscopy (PALS). Based on emission spectroscopy it was deciphered that Dy3+ lacks inversion symmetry in all the samples with asymmetry ratio of ∼1.2 in YPO4 and 2.75 in GdPO4. The same is correlated structurally wherein YO8 is in dodecahedron with D2d symmetry while GdO8 is highly distorted. The photoluminescence quantum yield (PLQY) increases monotonically with Gd3+ insertion and GdPO4:Dy3+ showing the highest PLQY endowed by enhanced asymmetry around Dy3+ making the f-f transitions more relaxed and allowable. The surface defects as revealed by positrons also decreased with increase in Gd content and that also aids the increase in emission intensities. Moreover PLQY value was higher with 274 nm compared to excitation with f-f transitions (∼351 nm) due to Gd3+ to Dy3+ energy transfer. The phosphors have similar color coordinate value and correlated color temperature of (∼0.33, ∼0.36), ∼5400 K, respectively, which are close to the bluish cool-white emission. Therefore, the GdPO4:Dy3+ phosphor with longer excited state lifetime, moderate PLQY, effective CIE coordinates close to white and high CCT can be explored for generation of cool white light emission excitable by UV/NUV LED for solid-state lighting and optoelectronic devices.

Novel Sm3+ doped YCa4O(BO3)3 phosphors: Structural and, low and room temperature luminescent insights

Inorganic phosphors, known for their ability to capture energy from various sources and emit visible light, have become essential in the development of advanced lighting and display technologies. This study explores YCa4O(BO3)3 (YCOB) as a potential host material for phosphors, focusing on the luminescent properties of YCOB phosphors doped with Sm3+ ions. The successful integration of Sm3+ ions into the YCOB host lattice is confirmed through structural characterization using X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Energy-Dispersive X-ray Spectroscopy (EDS). Photoluminescence (PL) studies reveal distinct emission spectra with Stark energy level splitting, indicating a cooperative effect between Y3+ and Sm3+ ions. Concentration quenching, mainly attributed to dipole-dipole (d-q) interactions, is observed at higher Sm3+ concentrations. Temperature-dependent PL measurements demonstrate thermal quenching at lower temperatures and increased emission intensity with higher laser power. Thermal quenching is explained by reduced lattice vibrations and electron-phonon interactions, leading to decreased radiative recombination of charge carriers. The CIE chromaticity data position the samples in the orange-red region, emitting vibrant orange-red light. This comprehensive investigation provides insights into the synthesis and luminescent properties of YCOB:Sm3+ phosphors, highlighting their potential applications in luminescent devices.

Temperature Dependence of Mn4+ Emission Intensity and Lifetime in TriGain® Phosphor (K2SiF6:Mn4+)

The temperature dependence of the Mn4+ photoluminescence and lifetime has been measured in the red emitting K2SiF6:Mn4+ phosphor that is sold under the trade name, TriGain®. In the range 12−450 K, the 2E → 4A2 emission intensity increases considerably while the lifetime decreases. Above 450 K, rapid decrease in the intensity and lifetime is observed. The results are interpreted in terms of dynamically induced increases in the emission intensity and decay rate coupled with an Arrhenius-type thermal quenching. The parameters of our fitting to physical models are compared with those reported on laboratory synthesized K2SiF6:Mn4+ phosphor. This comparative study sheds light on factors responsible for non-radiative relaxation processes, which is fundamental to the understanding of phosphor quantum efficiency and performance. The temperature dependence of the Stokes to anti-Stokes vibronic line intensity ratios is also measured and analyzed. Due to low thermal conductivity of K2SiF6, it was necessary to develop protocols to ensure that the surface temperature of the phosphor was close to that of the cold finger in the closed cycle He cryostat.