Reabsorption Phenomenon Research Articles

Zero-thermal-quenching broadband yellow-emitting Bi3+-activated phosphors based on metal to metal charge transfer

Bi3+-activated phosphors have been proven to have potential applications foreground in white light-emitting diodes (WLED), plant growth lamps and temperature sensing. Therefore, it is urgent to exploit high-efficiency Bi3+-activated phosphors. Herein, a novel broadband yellow-emitting phosphor Ba2GdGaO5:Bi3+ with high internal quantum efficiency (IQE = 77%) was obtained based on metal to metal charge transfer (MMCT) between Bi3+ ground state and Gd3+ excited states. The photoluminescence excitation (PLE) spectrum and photoluminescence (PL) spectrum range from 225 nm to 400 nm and 400 nm to 700 nm, respectively, which can avoid the reabsorption phenomenon efficiently. Besides, Ba2GdGaO5:Bi3+ has superior thermal stability and it shows zero-thermal-quenching at 150 °C. The K+ doping hardly changes the thermal stability and can improve the PL intensity to 133.1% when the K+ concentration is 2%. Finally, a phosphor-convert WLED (pc-WLED) was simply synthesized by Ba2GdGaO5:Bi3+ and BaMgAl10O17:Eu2+ (BAM:Eu2+) phosphors. The doping of Eu3+ can significantly enhance the color rendering index (CRI, from 88.1 to 91.5) and reduce the correlated color temperature (CCT, from 4911 K to 4014 K). The above experimental results demonstrated that the phosphor has great application prospect in WLED.

Structure, luminescence properties, and valence-induced spectral behavior of a bismuth-activated garnet phosphor

The increasing demand for full-visible-spectrum lighting has prompted the development of novel phosphors with multicolor emission.

Design and Modeling of Bioreactor Utilizing Electrophoresis and Di-Electrophoresis Techniques for Regenerating Reabsorption Function of Human Kidney PCT in Microfluidics Environment.

The need for innovation in medical device technology is immense; especially to replace dialysis techniques the necessity is extremely high. Available techniques that promised to replace dialysis have not yet geared up to the marketization level. The utilization of live kidney cells makes these devices costly, delicate, and unreliable. This paper aims to design a bioreactor to mimic the reabsorption function of the kidney that is fully artificial and highly controllable, which can be one step forward to the emerging Kidney-on-Chip (KOC) technology. The additional benefit of the proposed design is that it utilizes size-dependent reabsorption along with charge-dependent reabsorption phenomena to make it more compatible with human kidney function. The electrophoresis (EP), and di-electrophoresis (DEP) techniques are utilized to mimic the reabsorption function in this report. The structure utilized in the present design exactly replicates the proximal convoluted tubule (PCT) dimensions and functions as well. The whole setup is implemented in the COMSOL Multiphysics FEM benchmark tool for simulation, and analysis with appropriate boundary conditions. The device when excited by an electric field, Electrophoresis has produced a maximum velocity of 1.07 m/s for DC excitation and di-electrophoresis has produced a maximum flow velocity of 1.23 m/s, where both the offset voltages are the same (0.7 V). The flow velocity obtained utilizing both EP and DEP produced a reabsorption rate of 50-58% depending on the voltage applied and dimensions considered which is close to 60% reabsorption rate of the normal human kidney PCT. In accordance with the outcomes produced, the di-electrophoresis technique proved to be more efficient in realizing bioreactor as compared to electrophoresis. The novelty of the present work lies in the creation of a simulation environment, rigorous analysis, and optimization of the bioreactor supported by compact mathematical model.

Determination of orellanine and muscarine in biological fluids in suspected or proven poisoning cases: About several cases

To present the application of validated methods for determination of (i) orellanine, a highly nephrotoxic molecule responsible of the toxicity of some Cortinarius mushroom and (ii) muscarine, another mushroom toxin, acting as a neurotoxin not reaching the central nervous system, in biological fluids using LC-HRMS/MS technology in poisoning case context. These toxins are annually responsible of poisoning cases or even cases of death. We developed analytical methods using LC-HRMS/MS with Orbitrap technology and a liquid/liquid extraction. These two validated methods were applied to 17 suspecting or proven mushroom intoxication cases (12 for orellanine determination and 5 for muscarine). Biological fluids (whole blood and/or plasma and/or urine) were obtained from the national study CHAMPITOX or from the classical patient care. For orellanine cases, because of the long latency period between intake and first symptoms, the delay between intake and sample collection was particularly long (average of 8.5 days). As muscarinic syndrome is one of the short latency syndromes, a shorter sample collection delay was related to these cases (average of 14.5 hours). A full quantitative validation was performed for orellanine in plasma and urine (LOD: 0.1 μg/L, LLOQ 0.5 μg/L) and a qualitative in whole blood (LOD: 0.5 μg/L) [Flament E. J Anal Toxicol 2022:bkac018.]. Applied to our cases, we have highlighted orellanine in 8 out of the 12 cases with very low concentrations (near to the LLOQ or between the LLOQ and the LOD). Concerning the muscarine, a full quantitative validation was performed in the three matrices (in whole blood and plasma, the LOD and LLOQ were 0.05 and 0.1 μg/L, respectively, and in urine, LOD and LLOQ were 0.5 and 1 μg/L, respectively). Muscarine was identified and quantified in all cases. Concentrations (ranging from 0.12 to 752 μg/L in the three matrices) were much higher than those for orellanine. For orellanine cases, concentrations were very low owing to the high delay between intake and sample collection. In addition, orellanine half-life was estimated to be 109 ± 6 min with reabsorption by proximal tubular cells (in rats) [Najar D. Toxins 2018;10(8):333.]. This reabsorption phenomenon allows the detection of the toxin for up to 17 days in whole blood and 24 days in urine. Concentrations of muscarine were higher because of the shorter sample collection delay after the intake. To our knowledges, these results are (i) the first identification reports of orellanine in biological fluids with quantification in urines, and also (ii) the first identification and quantification reports of muscarine in blood matrices (whole blood and/or plasma). These analytical methods are (i) essential tools for clinicians in order to document mushroom poisoning cases (ii) but also for analysts to fill the knowledge gap about these mycotoxins, and (iii) tools which can be applied to post-mortem cases.

Mathematical model of fluid flow in a double constricted tapered tube with permeable boundary

Abstract In this paper, a mathematical model for the steady laminar, incompressible and Newtonian fluid flow in a proximal renal tubule is presented. In this, the tubule is considered as a tapered tube with double constriction and permeable boundary. The impact of the fluid reabsorption across the tubule wall is assumed as the occurrence of exponentially decreasing flow at each cross-section. The present model is formulated through the Navier–Stokes equations, under the appropriate boundary conditions. A regular perturbation technique is used to obtain the approximate solutions. This study brings out the significant impacts of reabsorption coefficient (α) and tapered angle (ϕ) on the flow variables such as velocities, the drop in pressure, and wall shear stress are discussed through graphs. The streamlines are also plotted to understand the influence of the reabsorption and tapering phenomena on the flow.

Ibuprofen molecular aggregation by direct back-face transmission steady-state fluorescence.

Direct back-face transmission steady-state fluorescence was successfully applied to the study of aggregation of ibuprofen and ibuprofenate anion in solution taking advantage of its own fluorescence. The analysis of the experimental data involves the use of the differential reabsorption model to account for re-absorption phenomenon and the closed association model to describe aggregation. The fluorescence quantum yield of ibuprofenate increases when it aggregates in the presence of sodium, but it markedly decreases when 1-butyl-3-methylimidazolium is used as counterion. The proposed methodology allows the accurate determination of the critical aggregation concentrations and the mean aggregation numbers. Results were supported by complementary techniques such as time-resolved fluorescence, 1H-NMR and small-angle neutron and X-ray scattering. The developed technique constitutes a promising strategy to characterize the aggregation of poorly fluorescent surfactants that aggregates at high concentrations and hence at high absorbance values, conditions in which the most common right-angle configuration for fluorescence acquisition is troublesome due to re-absorption.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s43630-022-00247-7.

Toward High‐Quality Laser‐Driven Lightings: Chromaticity‐Tunable Phosphor‐in‐Glass Film with “Phosphor Pattern” Design

AbstractHigh‐quality laser‐driven lightings require not only high luminous flux (LF) but also uniform spectral distribution. Herein, the green‐emitting Lu3Al5O12:Ce3+ (LuAG:Ce) and red‐emitting CaAlSiN3:Eu2+ (CASN:Eu) commercial phosphor powders with high‐performance are fabricated into phosphor‐in‐glass film (PiGF) sintered on sapphire plate, and further served as a motor‐driven rotatory “phosphor wheel” to receive pumping of blue laser in a reflective excitation light path. The greatly relieved thermal pressure, benefited from the high‐thermal‐conductivity sapphire substrate and the pulse‐like rotatory excitation mode, efficiently retards the occurrence of luminescence saturation. Remarkably, the photon reabsorption phenomenon in the conventional “phosphor mixture” design is well solved by introducing a smart “phosphor pattern” design, free of causing inhomogeneous angular color distribution at the same time. The constructed LuAG:Ce PiGF‐based lighting source yields high brightness of 2970 lm@21 W mm−2, and the constructed LuAG:Ce PiGF‐CASN:Eu PiGF‐based lighting source yields luminosity‐chromaticity balanced white light with LF higher than 1000 lm and color rendering index of 80–90.

Effect of Enterohepatic Circulation on the Accumulation of Per- and Polyfluoroalkyl Substances: Evidence from Experimental and Computational Studies.

The pharmacokinetic characteristics of per- and polyfluoroalkyl substances (PFAS) affect their distribution and bioaccumulation in biological systems. The enterohepatic circulation leads to reabsorption of certain chemicals from bile back into blood and the liver and thus influences their elimination, yet its influence on PFAS bioaccumulation remains unclear. We explored the role of enterohepatic circulation in PFAS bioaccumulation by examining tissue distribution of various PFAS in wild fish and a rat model. Computational models were used to determine the reabsorbed fractions of PFAS by calculating binding affinities of PFAS for key transporter proteins of enterohepatic circulation. The results indicated that higher concentrations were observed in blood, the liver, and bile compared to other tissues for some PFAS in fish. Furthermore, exposure to a PFAS mixture on the rat model showed that the reabsorption phenomenon appeared during 8-12 h for most long-chain PFAS. Molecular docking calculations suggest that PFAS can bind to key transporter proteins via electrostatic and hydrophobic interactions. Further regression analysis adds support to the hypothesis that binding affinity of the apical sodium-dependent bile acid transporter is the most important variable to predict the human half-lives of PFAS. This study demonstrated the critical role of enterohepatic circulation in reabsorption, distribution, and accumulation of PFAS.

Interplay of Zn(OAc)2 concentration, morphology, and emission in hydrothermal-grown ZnO nanostructures

We report the interplay of zinc acetate [Zn(CH3COO)2, Zn(OAc)2] concentration, morphology, and emission in hydrothermal-grown ZnO nanostructures. Highly oriented nanorods with intense, 54 to 96 ps near-band-edge ultraviolet (UV) emissions are successfully fabricated using 25 to 75 mM concentrations. On the other hand, larger and randomly oriented nanocrystals are fabricated using 100 to 150 mM concentrations. Although all nanostructures exhibit hexagonal wurtzite crystal structures, increasing the Zn(OAc)2 concentration affects their preferential orientation, morphology, and UV emission. The peculiar nanostructure emissions observed are also attributed to a reabsorption phenomenon among adjacent nanostructures. For potential scintillator applications, particularly for x-ray diagnostics, our results suggest that less than 100 mM Zn(OAc)2 concentrations should be used to reduce the UV emission reabsorption in hydrothermal-grown ZnO nanostructures.

Holmium(iii) molecular nanomagnets for optical thermometry exploring the luminescence re-absorption effect.

Coordination complexes of lanthanide(3+) ions can combine Single-Molecule Magnetism (SMM) with thermally modulated luminescence applicable in optical thermometry. We report an innovative approach towards high performance SMM-based optical thermometers which explores tunable anisotropy and the luminescence re-absorption effect of HoIII complexes. Our concept is shown in dinuclear cyanido-bridged molecules, {[HoIII(4-pyridone)4(H2O)2][MIII(CN)6]}·nH2O (M = Co, 1; Rh, 2; Ir, 3) and their magnetically diluted analogues, {[HoIIIxYIII1–x(4-pyridone)4(H2O)2][MIII(CN)6]}·nH2O (M = Co, x = 0.11, 1@Y; Rh, x = 0.12, 2@Y; Ir, x = 0.10, 3@Y). They are built of pentagonal bipyramidal HoIII complexes revealing the zero-dc-field SMM effect. Experimental studies and the ab initio calculations indicate an Orbach magnetic relaxation with energy barriers varying from 89.8 to 86.7 and 78.7 cm−1 K for 1, 2, and 3, respectively. 1–3 also differ in the strength of quantum tunnelling of magnetization which is suppressed by hyperfine interactions, and, further, by the magnetic dilution. The YIII-based dilution governs the optical properties as 1–3 exhibit poor emission due to the dominant re-absorption from HoIII while 1@Y–3@Y show room-temperature blue emission of 4-pyridone. Within ligand emission bands, the sharp re-absorption lines of the HoIII electronic transitions were observed. Their strong thermal variation was used in achieving highly sensitive ratiometric optical thermometers whose good performance ranges, lying between 25 and 205 K, are adjustable by using hexacyanidometallates. This work shows that HoIII complexes are great prerequisites for advanced opto-magnetic systems linking slow magnetic relaxation with unique optical thermometry exploiting a luminescence re-absorption phenomenon.

Modelling approach for analysis of moisture transport in diatomaceous earth pellets

Gradual moisture loss from spherical porous pellets is a prerequisite to induce entomopathogenic nematodes into a partial state of anhydrobiosis and for extending their shelf-life under non-controlled storage conditions. The aim of this work was to analyse the moisture loss in diatomaceous earth pellets through a mathematical model based on the molecular diffusion into a spherical porous structure. A natural and a forced convection scenarios were studied. For the experiments, pellets of 5 mm in radius with an initial moisture content of 1.0 (kg H2O/kg dry matter) were stored at 23 °C and 96% relative humidity. The moisture loss represents a drying process in two-stages and a crack formation in the pellet was observed, causing a moisture re-absorption phenomenon between 5 and 8 days; this event could originate an increase of the macro-porosity and the capillary pressure. The theoretical prediction showed a better accuracy for natural convection. The deviation in the case of forced convection is explained by the crack formation, which was not considered in the model.

Concentration-dependent emission of nitrogen-doped carbon dots and its use in hazardous metal-ion detection

Nitrogen-doped carbon dots (CDts) with tunable fluorescence properties in aqueous media were synthesized hydrothermally. The excitation wavelength variation to obtain the maximum emission produced a blue shift in the emission peaks upon dilution in an aqueous solution. The shift can be explained by a re-absorption phenomenon in a concentrated solution. The interparticle interaction within was responsible to show dilution-dependent optical behavior. The as-synthesized solution of CDts did not show any prominent absorption peak over a wide range. However, upon dilution, two peaks became predominant. The concentration-dependent behavior was observed during the interaction with metal cations. Cationic salts of Co(II) and Hg(II) caused quenching at different dilutions of CDts. This might be explained by the exposure of different surface functional groups during dilution and metal-ion–CDts charge transfer. The quenched fluorescence of CDts was rescued using ascorbic acid. Therefore, the one-pot detection of Co(II)/Hg(II) and ascorbic acid was designed through a ‘Turn Off/On’ phenomenon.

Spectroscopic investigation of Tb(tmhd)3 - Eu(tmhd)3 co-doped poly(methyl methacrylate) fibre

The article presents energy transfer observed in poly (methyl methacrylate) co-doped by trivalent terbium and europium ions. The measured spectra and terbium luminescence decay changes confirm energy transfer process between used lanthanides. Maximum energy transfer efficiency 29.6% was obtained for molar concentration ratio of Eu (tmhd)3/Tb (tmhd)3 equals to 3.6. Additionally, the co-doped polymer host was used for luminescent polymeric fibre fabrication. The waveguide structure is attractive for investigation of energy transfer, reabsorption, and attenuation phenomena observed in polymeric fibre. The luminescent properties vs. fibre length at one end excitation (355 nm) is also investigated in terms of spectrum shape modification.

Energy transfer of Tb(tmhd)3 - Rhodamine B in poly(methyl methacrylate) fiber for new photonic applications

In our work we present the energy transfer phenomenon observed in poly(methyl methacrylate) co-doped by Tb(tmhd)3 and Rhodamine B. The optical properties characterization (recorded luminescence spectra and decay time measurements) indicate efficient energy transfer (up to 67%) between used complexes. Additionally, the developed matrix was used for luminescent polymeric fiber fabrication. The co-doped PMMA fiber allows significant luminescence spectrum modification by using energy transfer and optical radiation reabsorption phenomena. Presented lanthanide-organic dye co-doped poly(methyl methacrylate) fiber can be used for new photonic applications of polymeric optical fibers.

Carbon nanodots with intense emission from green to red and their multifunctional applications

In this report, carbon nanodots (CDs) with tunable full-color emission were successfully synthesized by a solvothermal method. By changing the carbon source (p-phenylenediamine or o-phenylenediamine) and the concentration, green, yellow, orange and red CDs (GCDs, YCDs, OCDs and RCDs) were successfully fabricated. As the concentration of the starting materials was increased, the emission peak was red-shifted. The shifted peaks showed strong intensity and an obvious color change. This concentration-dependent effect was attributed to the reabsorption phenomenon. Carbon source was critical in determining the fluorescence properties and the quantum yield (QY) of full-color CDs was high. The CDs also presented a distinct pH sensitivity. The PL intensity of RCDs showed linear decreases over decreasing pH from 11 to 4 and from 4 to 2. Fluorescent oil carrying CDs was successfully applied for various purposes such as anti-counterfeiting, information encryption and storage purposes. An RCD film was successfully fabricated that could improve the correlated color temperature and color rendering index of white light-emitting diodes.

Dye-embedded YAG:Ce3+@SiO2 composite phosphors toward warm wLEDs through radiative energy transfer: preparation, characterization and luminescence properties.

The most common yellow phosphor for wLEDs, Y3Al5O12:Ce3+ (YAG:Ce3+), suffers from a deficiency of red in its spectral content of light. In this paper, a new strategy is provided to tailor the Ce3+ spectral profile through surface-located dye molecules of ATTO-Rho101, which feature intense, broad absorption in the green-yellow spectral region of Ce3+ emission as well as bright red emission. Sphere-shaped and highly dispersed micrometer and nanometer-sized YAG:Ce3+ (micro/nano-YAG:Ce3+) was synthesized through a modified solvothermal method. Surface SiO2 coating and simultaneous dye embedding were performed on the solvothermally derived YAG:Ce3+, heat-treated micro-YAG:Ce3+ and commercial phosphors. Efficient radiative transfer/reabsorption from Ce3+ in the inner core of YAG to the dye molecules in the SiO2 outer shell, irrespective of the size of the phosphors, was demonstrated in the accumulated YAG:Ce3+@SiO2 + dye powder upon blue light excitation; this enhanced its red emission. Fluorescence microscopy was demonstrated to be a powerful tool to identify the reabsorption phenomenon of the powdered materials. Packaging the heat-treated micro-YAG:Ce3+@SiO2 + dye phosphors on blue LED chips yielded a warm wLED (Ra∼ 93), but an Ra of only ∼79 was obtained for the wLED with commercial YAG:Ce3+@(SiO2 + dye)5 due to the low concentration of phosphors dispersed in the epoxy resin and the resulting decreased reabsorption by dye molecules. Surface-protonated amine species were found to induce Ce3+→ Ce4+ oxidation upon activation by heating or photoirradiation and then quench the photoluminescence (PL) of micro-YAG:Ce3+ even after surface modification by SiO2, YAG or being embedded in an epoxy resin matrix. High calcination temperatures greatly improved the PL stability of micro-YAG:Ce3+ through the removal of surface-capped species. The dye in the silica matrix showed high stability against heating and irradiation due to the so-called "caging effects"; however, decreased photo-stability was found in commercial YAG:Ce3+@(SiO2 + dye)5 due to the incomplete and/or loose SiO2 layer grown during multiple surface modifications.

Re-evaluation of the steady-state self-quenching constant of quinine bisulphate from fluorescence measurements in transmission geometry

In the present work we show that a recent methodology developed by us to acquire emission spectra and fluorescence quantum yields of highly absorbing samples in transmission configuration, constitutes a very simple and robust alternative to determine self-quenching constants, KSQ. We measured the absorption and the steady-state emission spectra of quinine bisulphate, QBS, solutions ranging between 1.5 × 10−5 and 1.5 × 10−1 M. From these data, we calculated the expected emission spectra, affected by re-absorption, for all QBS concentrations. For higher concentrations, the re-absorption in the excitation/detection direction reaches values up to 6% of the total emitted intensity. The KSQ of the dye was re-evaluated from the concentration dependence of the quotients between the calculated and the experimental integrated emission spectra. The obtained value, KSQ = 18.4 ± 0.1 M−1, shows no significant differences with those obtained from steady-state and average lifetimes by other authors, pointing out the diffusional nature of the self-quenching phenomenon. The present work helps clarify some ambiguous aspects concerning the photophysics of QBS, stressing that re-absorption phenomena must be considered in QBS concentrated solutions for accuracy measurements.

Growth, structure and spectroscopic properties of 1 at.% Er3+: GdTaO4 laser crystal

1at% Er3+ doped Er: GdTaO4 laser crystal with high optical quality was successfully grown by the Czochralski method. The structural parameters were obtained by the X-ray Rietveld refinement. A high crystalline quality of Er: GdTaO4 was determined by the X-ray rocking curve. The transition intensity parameters of Er3+ ions were fitted according to the absorption spectra along three principal polarization directions. The relatively larger emission cross section (1.022×10−20cm2), long fluorescence lifetime ( 5.66ms) and relatively weaker reabsorption phenomenon around 1.6µm indicate that 1at% Er: GdTaO4 crystal can be used as a promising NIR laser material. Meanwhile, the stimulated emission cross-section spectra along three principal polarization directions were investigated for 4I13/2 →4I15/2 transitions at 1.5–1.6µm which indicates a great potential of Er: GdTaO4 for multi-wavelength emission at 1.5–1.6µm. In addition, the possibility of generating green and red lasers in Er: GdTaO4 was also analyzed and evaluated.

Effects of photon reabsorption phenomena in confocal micro-photoluminescence measurements in crystalline silicon

Confocal micro-photoluminescence (PL) spectroscopy has become a powerful characterization technique for studying novel photovoltaic (PV) materials and structures at the micrometer level. In this work, we present a comprehensive study about the effects and implications of photon reabsorption phenomena on confocal micro-PL measurements in crystalline silicon (c-Si), the workhorse material of the PV industry. First, supported by theoretical calculations, we show that the level of reabsorption is intrinsically linked to the selected experimental parameters, i.e., focusing lens, pinhole aperture, and excitation wavelength, as they define the spatial extension of the confocal detection volume, and therefore, the effective photon traveling distance before collection. Second, we also show that certain sample properties such as the reflectance and/or the surface recombination velocity can also have a relevant impact on reabsorption. Due to the direct relationship between the reabsorption level and the spectral line shape of the resulting PL emission signal, reabsorption phenomena play a paramount role in certain types of micro-PL measurements. This is demonstrated by means of two practical and current examples studied using confocal PL, namely, the estimation of doping densities in c-Si and the study of back-surface and/or back-contacted Si devices such as interdigitated back contact solar cells, where reabsorption processes should be taken into account for the proper interpretation and quantification of the obtained PL data.

Analytical model of photon reabsorption in ZnO quantum dots with size and concentration dependent dual-color photoluminescence

We investigate the concentration and size dependent UV/green photoluminescence properties of the ZnO quantum dots (QDs) with sizes in the strong confinement regime. The luminescence characteristics of an ensemble of colloidal semiconductor QDs with quantum confinement effect depend sensitively on particle concentration but this has only been qualitatively understood. By taking ZnO QDs as an ideal prototype, we construct a material-independent theoretical model to study the photon reabsorption phenomenon. The theoretical result agrees well with the experiment. This model can be used to quantitatively study the concentration-dependent luminescence properties of any collection of QDs with considerable size dispersion. On the other hand, the origin of green emission in ZnO QDs remains debated. The comparative study of the size dependence of UV and green emissions in conjunction with the effective-mass approximation calculation suggests that the green emission in the ZnO QDs originates from the conduction band to the deep level transition.