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This work demonstrates a unique strategy for stabilizing Eu2+ ions in Li2B4O7 for color-tunable light emission through defect engineering by the virtue of U6+ co-doping.

Materials that can depict persistent deep red light under both ultraviolet (UV) and X-ray illumination can be a boon to sustainable economy, particularly for optical imaging, solid state lighting, and anticounterfeiting applications.

This work demonstrated shape tuning of IrO2 nanoparticles to nanocube and nanorods in molten salt and demonstrated the exemplary performance of IrO2 nanorods as an electrocatalyst for oxygen evolution reaction even surpassing commercial IrO2.

This work demonstrates the importance of dopant local structure and concentration in designing Ln3+-doped pyrochlore-based optoelectronic materials.

Trivlent dopants with larger ionic radii and weaker-vacancy dopant association result in higher oxygen vacancy and Ce3+ fraction in CeO2 and facilitate ORR catalysis.

A 15-fold intense green emission at 545 nm is observed in a Tb3+-activated (Y, Gd)F3 nanophosphor with high Tb3+ content and minimal Gd3+ concentration.

In the present study, gas tungsten arc welding was employed to weld Ti-stabilized 439 ferritic stainless steel using 308L austenitic stainless steel filler electrode with varying heat input, i.e., low heat input (LHI) and high heat input (HHI). The optical microstructure revealed the formation of retained austenite (RA) and ferrite in the weld zone (WZ), whereas the peppery structure consisting of chromium-rich carbides were observed in the heat-affected zone for both the weldments. The volumetric fraction of RA was calculated using X-ray diffraction analysis. The RA’s content decreased, whereas grain size in WZ increased with an increase in heat input. The local misorientation and grain boundary distribution in the welded region was investigated by electron backscattered diffraction. The LHI weldment depicted the higher micro-hardness and tensile strength attributed to the higher content of RA as compared to HHI; however, the opposite trend was observed for the intergranular corrosion resistance.

In this study, emissions between 350 nm and 2.8 μm are produced from molten-salt-synthesized LaF3:Yb3+,Er3+ (LFYE) nanocrystals (NCs) under 980 nm excitation. In fact, such wide spectral emissions ...

Slurry polymerization processes using Zeigler–Natta catalysts are most widely used for the production of polyethylene due to their several advantages over other processes. Optimal operating conditions are required to obtain the maximum productivity of the polymer at minimal cost while ensuring operational safety in the slurry phase ethylene polymerization reactors. The main focus of this multi-objective optimization study is to obtain the optimal operating conditions corresponding to the maximization of productivity and yield at a minimal operating cost. The tuned reactor model has been optimized. The single objective optimization (SOO) and multi-objective optimization (MOO) problems are solved using non-dominating sorting genetic algorithm-II (NSGA-II). A complete range of Pareto optimal solutions are obtained to obtain the maximum productivity and polymer yield at different input costs.

Owing to the unique 4f-5d transitions and the involvement of 5d electrons, the divalent europium (Eu

Rice blast caused by Magnaporthe oryzae and sheath blight caused by Rhizoctonia solani, are the two major diseases of rice that cause enormous losses in rice production worldwide. Identification and utilization of broad-spectrum resistance resources have been considered sustainable and effective strategies. However, the majority of the resistance genes and QTLs identified have often been found to be race-specific, and their resistance is frequently broken down due to continuous exposure to the pathogen. Therefore, integrated approaches to improve plant resistance against such devastating pathogen have great importance. Silicon (Si), a beneficial element for plant growth, has shown to provide a prophylactic effect against many pathogens. The application of Si helps the plants to combat the disease-causing pathogens, either through its deposition in different parts of the plant or through modulation/induction of specific defense genes by yet an unknown mechanism. Some reports have shown that Si imparts resistance to rice blast and sheath blight. The present review summarizes the mechanism of Si transport and deposition and its effect on rice growth and development. A special emphasis has been given to explore the existing evidence showing Si mediated blast and sheath blight resistance and the mechanism involved in resistance. This review will help to understand the prophylactic effects of Si against sheath blight and blast disease at the mechanical, physiological, and genetic levels. The information provided here will help develop a strategy to explore Si derived benefits for sustainable rice production.

Persistent luminescent nanocrystals (PLNCs) in the sub-10 nm domain are considered to be the most fascinating inventions in lighting technology owing to their excellent performance in anti-counterfeiting, luminous paints, bioimaging, security applications, etc. Further improvement of persistent luminescence (PersL) intensity and lifetime is needed to achieve the desired success of PLNCs while keeping the uniform sub-10 nm size. In this work, the concept of molten salt confinement to thermally anneal as-synthesized ZnGa2 O4 :Cr3+ (ZGOC) colloidal NCs (CNCs) in a molten salt medium at 650 °C is introduced. This method led to significantly monodispersed and few agglomerated NCs with a much improved photoluminescence (PL) and PersL intensity without much growth in the size of the pristine CNCs. Other strategies such as i) thermal annealing, ii) overcoating, and iii) the core-shell strategy have also been tried to improve PL and PersL but did not improve them simultaneously. Moreover, directly annealing the CNCs in air without the assistance of molten salt could significantly improve both PL and PersL but led to particle heterogeneity and aggregation, which are highly unsuitable for in vivo imaging. We believe this work provides a novel strategy to design PLNCs with high PL intensity and long PersL duration without losing their nanostructural characteristics, water dispersibility and biocompatibility.

Exploring lanthanide doped materials and their high-pressure optical properties is important from the perspective of designing pressure sensors, piezoelectric materials, scintillators, and optoelectronic devices, just to mention a few. Understanding the high-pressure optical properties of polymeric fibrous mats provides significant advantages in terms of flexibility, tunability, facile processability, and malleability. In this work, we have developed flexible polyvinylidene difluoride (PVDF) fibrous mats doped with an Eu3+ source of Eu(NO3)3·5H2O (EN-PF) or Eu2(SO4)3 (ES-PF) by a Forcespinning® method. Microstructural analysis of these two systems indicates that Eu(NO3)3·5H2O and Eu2(SO4)3 are homogeneously distributed and dispersed into the PVDF matrix. Fiber formation promotes a β-phase PVDF. Eu3+ doping increases the β-phase. Its fraction is larger for the ES-PF mats. To understand their high-pressure optical properties, their photoluminescence spectra have been taken at various pressures up to 58 GPa in a diamond anvil cell. High-pressure luminescence illustrates a clear change in asymmetry ratio, peak intensity, peak breadth, color coordinate, and color temperature of Eu3+ ions from both EN-PF and ES-PF with a different extent of changes. Specifically, Eu3+ ions in the ES-PF mats switch from asymmetric to symmetric environment as pressure increases. Those in the EN-PF mats present symmetric environment for all tested pressures. Both of the Eu3+ doped PVDF systems present irreversible changes. Therefore, the EN-PF fibrous mats present an opportunity to make pressure induced red-orange-yellow tunable phosphors for multifunctional applications.

A wide range of inorganic nanomaterials with many fascinating properties and application potentials in widespread fields may be synthesized by wet chemical synthetic routes. To achieve scientific a...

Defect engineering in perovskites has been found to be the most efficient approach to manipulate their performance in ultraviolet-to-visible photon conversion. Under UV irradiation, BaSnO3 exhibited multicolor photoluminescence (MCPL) in the bluish white region. Its origin has not been well studied in the literature and has been probed in this work using synchrotron radiation, positron annihilation and density functional theory. To achieve desirable performance of doped BaSnO3 in optoelectronics, it is imperative to have correct information on the dopant local site, doping induced defect evolution and efficacy of host to dopant energy transfer (HDET). Extended X-ray absorption fine structure (EXAFS) showed that Eu3+ ions stabilize at both Ba2+ and Sn4+ sites consistent with the highly negative formation energy of around -6.26 eV. Eu3+ doping leads to an intense 5D0→7F1 orange emission and a feeble 5D0→7F2 red emission and an internal quantum yield (IQY) of ∼21% mediated by ET from the defect level of EuBa and EuSn sites to the valence band maximum (VBM). X-ray absorption near edge structure (XANES) ruled out any role of Sn2+ in the PL of BaSnO3 or Eu2+ in the PL of BaSnO3:Eu3+. Interestingly, when co-doped, Eu3+ stabilizes at Sn4+ sites whereas La3+ stabilizes at Ba2+ sites with a formation energy value of -6.44 eV. Based on the asymmetry ratio in emission spectra, it was found that La3+ ions lead to lowering of symmetry around Eu3+ due to increased vacancies and structural distortions, and also suppress the luminescence IQY. We have performed experimental positron annihilation lifetime spectroscopy (PALS) to probe the defects in BaSnO3 in pristine samples and on doping/co-doping. The positron lifetimes for saturation trapping of positrons in various kinds of defects envisaged in BaSnO3 and in the defect free system were calculated using the MIKA Doppler program. Such deep insight into the effect of local structures, dopant sites, defect evolution, ET, etc. on the optical properties of BaSnO3 is expected to provide very deep insight for material scientists into the fabrication of perovskite-based optoelectronic and light-emitting devices.

Understanding the intricacies and fundamental processes of materials involved in dopant- and defect-based luminescence is of paramount importance for scientists and engineers working towards the design of solid-state lighting, optoelectronics, scintillators, etc. The lack of such fundamental information has restricted the design of new oxide-based materials for light-emitting devices and phosphor-converted materials. Here, we have designed Er2Ti2O7 (ETO), Er2Zr2O7 (EZO), Eu3+-doped ETO (EETO), and Eu3+-doped EZO (EEZO) via high-energy ball milling. Structural analysis using X-ray diffraction (XRD) and Raman spectroscopy suggested the stabilization of the ordered pyrochlore structure for ETO and EETO, whereas EZO and EEZO are stabilized in the defect fluorite structure. The ETO and EZO samples exhibited bright blue emission under ultraviolet irradiation. X-ray absorption near edge structure (XANES) analysis completely rules out contributions from Ti3+ or Zr3+ to the host emission via confirming that they exist as tetravalent ions. Extended X-ray absorption fine structure (EXAFS) analysis confirms the presence of a high density of oxygen vacancies (OVs) near the Ti and Zr sites, respectively, in ETO and EZO. The DFT-calculated charge transition levels qualitatively explain the origin of the blue emission of ETO and EZO with the dominant involvement of ionized oxygen vacancies. Positron annihilation lifetime spectroscopy (PALS) suggested that few changes in the defect density or type occurred upon europium doping in EETO. The defect concentration and type change significantly in EEZO with respect to EZO, which is of significant importance due to the possible agglomeration of vacancies into large-size defect clusters in EEZO. Surprisingly, in both hosts, red/orange narrow emission from europium (585–750 nm, 5D0 → 7FJ) was completely absent. Density of state (DOS) calculations suggested that a possible reason for this is that the Eu f-states are dominantly distributed around the bottom edge of the valence band (VB), far from the Fermi energy, electronic band gap, and top edge of the VB actively participating in the electronic transitions. Similarly, the Eu f-states are distributed around the top edge of the conduction band, far from the electronic band-gap region. We believe this work will be quite helpful for selecting suitable hosts and dopants, band gap engineering, and defect tuning in the pursuit of achieving efficient host-to-dopant energy transfer in Eu3+-doped pyrochlore materials.

Recent materials science and engineering research focused on defects, dopants, hosts, and morphological structures has resulted in novel cost efficient and sustainable phases with extraordinary properties and performance. Contributing in this direction we have designed dopant and rare earth free white light-emitting zincgallogermanate (ZGG) phosphors in nanosheet (NS) morphology. These ZGG NSs with interlayer and interfacial defects display bright white photoluminescence (PL) with significant quantum yield (QY). Thermal treatment of the as-synthesized ZGG NSs at 750 °C does not degrade their sheet-like morphology while resulting in long persistent luminescence (PerL) with a duration of approximately one hour. Furthermore, to improve the commercial viability of the as-synthesized ZGG NSs, we have assembled them as fine fibers of polyvinyl alcohol (PVA) using Forcespinning® technology. The ZGG–PVA fibers displayed efficient white PL with increased quantum yield compared to the as-synthesized ZGG NSs. We believe this technological evolution, transitioning from bulk ZGG to ZGG nanosheets, will lead to dopant-free/rare-earth-free persistent white light emission and an enhancement in QY. This technology will be a boon to the optoelectronic and lighting industries, and will benefit commercial applications in smart textiles, energy efficient lighting, night vision, anti-counterfeiting, traffic signals, and security, among other potential uses.

Pair matching charge compensation with trivalent and pentavalent dopants in ceria was found to be an attractive strategy in engineering defects with minimal distortions in the lattice and obtaining enhanced catalytic properties. In the present study, charge compensation with a vanadium codopant in trivalent ion doped ceria is studied. Defect evolution in the trivalent ion doped ceria with vanadium codoping has been studied in CeO2:Eu3+, CeO2:La3+,Eu3+ and CeO2:Y3+,Eu3+ systems and the choices of the dopant and co-dopant are triggered by their ionic radius. Eu3+ photoluminescence (PL) is used as a spectroscopic probe to monitor local structural changes around the dopants. Positron lifetime studies showed that oxygen vacancies formed due to trivalent ion doping are weakly associated when larger ions are doped and result in the formation of vacancy aggregates. Positron lifetime studies along with XRD studies show that vanadium codoping effectively removes the vacancies but the distortions are significant when the size mismatch between the pair match used for charge compensation is higher. Photoluminescence demonstrated that the oxygen vacancies associated with Eu are more effectively removed in the case of Y codoped samples. Electron Spin Resonance (ESR) studies suggested that vanadium in excess over the stoichiometric concentration of the trivalent ion can lead to additional defects. These studies are expected to help in tuning the vacancy concentrations as well as controlling the lattice distortions for technological applications such as catalysis, ionic conductivity, etc.

Cesium lead halide perovskite nanocrystals (NCs) have drawn a great deal of interest in optoelectronic and photonic applications due to their intrinsic and attractive photoluminescence properties, though, their commercial viability is of concern due to their intrinsic instability. In this study, blue and green luminous PMMA–CsPbX3 (X = Cl/Br) fibers were fabricated via the Forcespinning technique, where the polymer matrix encapsulated the NCs. Blue CsPbX3 NCs (b-CPX NCs) were synthesized under ambient conditions while fine color tuned blue to green CsPbX3 NCs (g-CPX NCs) were obtained after heat treatment at 150 °C. Field emission scanning electron microscopy (FESEM) shows fibers with diameters in the single digit microscale. Efficient encapsulation of NCs in the PMMA fiber was confirmed using FTIR spectroscopy. UV visible spectra of the NCs suggested a quantum confinement effect. Pristine NCs show bright blue and green emission from b-CPX and g-CPX NCs under UV irradiation (365 nm) which was successfully reproduced even upon encapsulation in the PMMA matrix. In both cases, the PMMA matrix besides promoting QD encapsulation also enhanced the photoluminescence quantum yield (PLQY) from 25.5% to 31.1% (blue PMMA fibers) and 42.6% to 51.4% (green PMMA fibers) compared to bare NC PLQY. PMMA–CsPbX3 (X = Cl/Br) also possessed narrow half-peak width compared to pristine NCs suggesting high color purity. This work provides a novel polymer fiber-based encapsulation approach to solve the intrinsic instability issues of CsPbX3 NCs, therefore prompting promising practical applications.

Slurry polymerization processes using Zeigler–Natta catalysts, are most widely used for the production of polyethylene due to their several advantages over other processes. Significant advancements have been made in the modeling of these processes to obtain high-quality final products. The modeling work in this field has a very wide scope due to the great diversity of the catalyst types, polymerization processes, polymerization conditions, product qualities and microstructures that exist at the commercial scale. In this article, we have reviewed and discussed the slurry polymerization processes for the production of polyethylene and the multiscale modeling and simulation framework in slurry reactors. The multiscale modeling framework mainly comprises of the kinetic model, single-particle diffusion models, multiphase hydrodynamics, phase equilibria, reactor residence time distribution and the overall mass and heat balances. Guidelines to implement the multiscale mathematical modeling and simulation in slurry-phase olefin polymerization processes are proposed. Special focus is given on the need to reduce the computational effort for the simulation of industrial reactors so that the models can be used as an effective tool-kit for optimization studies using state-of-art algorithms.

Rare-earth based A2B2O7 compounds have been considered as potential host materials for nuclear waste due to their exceptional chemical, physical, capability of accommodating high concentration of actinides at both A- and B-sites, negligible leaching, tendency to form antisite defects, and radiation stabilities. In this work, La2Hf2O7 (LHO) and Gd2Hf2O7 (GHO) nanoparticles (NPs) were chosen as the RE-based hafnates to study the structural changes and the formation of different U molecular structures upon doping (or alloying) at high concentration (up to 30 mol %) using a combined coprecipitation and molten-salt synthesis. These compounds form similar crystal structures, i.e., ordered pyrochlore (LHO) and disordered fluorite (GHO), but are expected to show different phase transformations at high U doping concentration. X-ray diffraction (XRD) and Rietveld refinement results show that the LHO:U NPs have high structural stability, whereas the GHO:U NPs exhibit a highly disordered structure at high U concentration. Alternatively, the vibrational spectra show an increasingly random oxygen distribution with U doping, driving the LHO:U NPs to the disordered fluorite phase. X-ray spectroscopy indicates that U is stabilized as different U6+ species in both LHO and GHO hosts, resulting in the formation of oxygen vacancies stemming from the U local coordination and different phase transformation. Interestingly, the disordered fluorite phase has been reported to have increased radiation tolerance, suggesting multiple benefits associated with the LHO host. These results demonstrate the importance of the structural and chemical effect of actinide dopants on similar host matrices which are important for the development of RE-based hafnates for nuclear waste hosts, sensors, thermal barrier coatings, and scintillator applications.

Designing a bright blue and red phosphor for phosphor-converted white-light-emitting diodes would be extremely beneficial to the lighting industry. Achieving the same through defect and doping engineering in an interesting inorganic layered structure material, Ca2SnO4 (CSO), would fetch a lot of interest among material and optical scientists. There is no report on undoped and doped CSO lattices where extensive effort has been made to understand the origin of host emission, local site occupancy, defect evolution, etc. With the same intention, in this work, we have investigated the photophysical properties of undoped and Eu3+-doped CSO (CSOE). On UV irradiation, CSO displayed beautiful blue emission, and its origin has been explained experimentally using extended X-ray absorption fine structure (EXAFS) and theoretically using density functional theory (DFT) calculations. Both DFT and EXFAS pinpointed the role of oxygen vacancies (OVs) in blue emission of CSO. In fact, by extensive calculations, we also found out that both neutral and charged oxygen vacancies are involved in producing blue emission in CSO. To further tune the luminescence, the Eu3+ ion was doped in CSO, which produces highly pure red emission with an internal quantum efficiency (IQE) of ∼80% and negligible nonradiative transition. Based on EXAFS and lifetime spectroscopy, it was found that the Eu3+ ion is localized in a much higher fraction at the CaO7 site compared to SnO6 octahedra. This was further substantiated using DFT-calculated formation energies. Further, it is expected that aliovalent doping of the trivalent Eu3+ ion at Ca2+/Sn4+ leads to charge-compensating defects, which significantly impact the optical properties of CSOE, and were further investigated using positron annihilation lifetime spectroscopy (PALS). Such complete spectrum of work wherein photophysical properties of functional materials are optimized and studied by deciphering the role of OVs, local site occupancy of the dopant ion, and charge-compensating defects will inculcate a lot of interest within the scientific community in coming forward for research in the area of rare-earth-free phosphor as well as doped phosphor for solving the energy crisis.

A hierarchical and computationally efficient mathematical model was developed to explain the polymerization of high-density polyethylene (HDPE) in an isothermal, industrial, continuous stirred tank slurry reactor (CSTR). A modified polymeric multi-grain model (PMGM) was used. Steady-state macroscopic mass balance equations were derived for all species (namely, monomer, solvent, catalyst and polymer) to obtain the final particle size and the required monomer and solvent input rates for a given catalyst input and the reactor residence time. The interphase mass transfer coefficients were calculated for the industrial CSTR using the operating data on the reactor. The present model was tuned with some data on an isothermal industrial reactor and the simulation results were compared with data on another set of industrial reactor. The comparison revealed that the present tuned model is capable of predicting the productivity and the polymer yield at various catalyst feed rates and the mean residence times. The effects of variation of two operating variables (catalyst feed rate and mean residence time) on the productivity, the polymer yield, the polydispersity index (PDI) and the operational safety were analyzed. The present study indicated that an optimal value of the reactor residence time (for maximum productivity per catalyst particle) exists at any catalyst feed rate.