Absorption Quantum Research Articles

Comparative analysis of Sm3+-doped BaWO4 and CaWO4 phosphors: Properties and application in latent fingerprints and anti-counterfeiting

Self-activated tungstates doped with lanthanide ions are an excellent class of phosphor materials, exhibiting promising luminescence efficiency as well as stability which opens up their vast arena of applications. In this work, a detailed comparative study has been carried out on Sm3+ doped Ba/CaWO4 phosphors, synthesized via solid state reaction route. The structural, morphological and photo-physical properties have been investigated through various analytical techniques. The optical band gap and the refractive index of the phosphors have been estimated through diffuse reflectance spectroscopy. A 5-fold enhancement of the emission intensity is observed in CaWO4 as compared to BaWO4 phosphors owing to high asymmetrical environment. The underlying mechanisms of photoluminescence and energy transfer process (WO42+→Sm3+) are discussed in detail. The colour tuning from orange red to pure red emission is obtained from the Commission International de l′Eclairage (CIE) diagram. Better luminescent properties with desirable quantum yield, absorption efficiency and suitable Correlated Colour Temperature (CCT) and colour purity (91 %) values allow the optimised phosphors for diverse potential applications such as solid-state lighting, security ink for anti-counterfeiting, latent fingerprint detection, etc.

DFT supported studies of multi-responsive AIE active fluorophores for the sensitive fluorescence recognition of p-nitrophenol and pH: Vapor phase and solution mode sensing

Designing of an aggregation-induced emission (AIE) active multi-responsive fluorophores for the sensitive recognition of targeted analytes has been a hot spot in recent time. In pursuit of this endeavor, two chromene core sensors KG01 and KG02, installed with phenyl rotors, were efficiently designed, synthesized, and characterized through NMR spectroscopy. Proposed fluorophores demonstrated striking features of structure–property relationships, including solvatochromism and J-aggregates-based aggregation induced emission (AIE). Subsequently, well-thought-out developed sensors KG01 and KG02 were subjected to photoinduced electron transfer (PET) operated fluorescence quenching driven optical tracing of p-nitrophenol (p-NP) in the co-existence of competing analytes, with LOD down to 4.7 and 6.6 nM, respectively. Further, diversified theoretical calculations were executed to validate J-aggregates, supreme selectivity of sensors towards p-NP and PET as its primary sensing mechanism. Additionally, Jobs plot experiment, dynamic light scattering (DLS) size distribution, and 1H NMR titration assay also endorsed the selective p-NP sensing. Further, reported sensors were exploited for the fluorescence along with visual recognition of trifluoroacetic acid (TFA) and sodium hydroxide (NaOH). Interestingly, devised sensor KG01 disclosed naked-eye detection of TFA vapors. Furthermore, real water sample analysis, engineering of hand-held thin layer chromatography (TLC) plates-based fluorescent kits, and fabrication of logic devices were carried out to signify the convenient point-of-need applications of the proposed sensors. To the best of our knowledge, sensors KG01 and KG02 are first-ever solvatochromic and AIEgen chromenes with good quantum yield (Φ) and absorption coefficient as potential candidates to establish a range of easy-to-apply platforms for the selective and sensitive distinguishing of different aforementioned analytes. Given the role of p-NP as a priority pollutant from industrial sources with severe ecological and health impacts, these fluorescence sensors offer promising potential for developing cost-effective tools for rapid and precise trace-level detection. Additionally, industrial seepage of TFA and NaOH into water reserves poses serious health risks. These fluorescence sensors could be adapted to create devices capable of detecting these contaminants at nanomolar concentrations.

Elucidating the Supramolecular Interaction of Positively Supercharged Fluorescent Protein with Anionic Phthalocyanines.

Developing bioinspired materials to convert sunlight into electricity efficiently is paramount for sustainable energy production. Fluorescent proteins are promising candidates as photoactive materials due to their high fluorescence quantum yield and absorption extinction coefficients in aqueous media. However, developing artificial bioinspired photosynthetic systems requires a detailed understanding of molecular interactions and energy transfer mechanisms in the required operating conditions. Here, the supramolecular self-assembly and photophysical properties of fluorescent proteins complexed with organic dyes are investigated in aqueous media. Supercharged mGreenLantern protein, mutated to have a charge of +22, is complexed together with anionic zinc phthalocyanines having 4 or 16 carboxylate groups. The structural characterization reveals a strong electrostatic interaction between the moieties, accompanied by partial conformational distortion of the protein structure, yet without compromising the mGreenLantern chromophore integrity as suggested by the lack of emission features related to the neutral form of the chromophore. The self-assembled biohybrid shows a total quenching of protein fluorescence, in favor of an energy transfer process from the protein to the phthalocyanine, as demonstrated by fluorescence lifetime and ultrafast transient absorption measurements. These results provide insight into the rich photophysics of fluorescent protein-dye complexes, anticipating their applicability as water-based photoactive materials.

Surface modification of carbon dots with cyclodextrins as potential biocompatible photoluminescent delivery/bioimaging nanoplatform

BackgroundCyclodextrins are a well-established system which form inclusion complexes with many guest molecules. This property can be easily exploited to develop drug delivery systems. Additionally, carbon dots (CD) are a low-toxic photoluminescent product which have been used as luminescent tags. The combination of cyclodextrins and carbon dots allows obtaining a new nanoplatform, a biocompatible material, with both capabilities, increasing as well the internalization by the cells of the CD, induced by the cyclodextrins. ResultsIn the present work, we have modified the surface of carbon dots obtained from citric acid and glutathione with β and γ cyclodextrins. After a morphological and spectroscopic characterization, we concluded that the luminescence quantum yield and absorption molar coefficient of the derivatized and unmodified carbon dots was the same. These findings, together with the spectroscopic detection of active cyclodextrins, those bond to the CD able to interact with a guest molecule, allowed determination of the ratios: cyclodextrins/CD, active cyclodextrins/CD and an estimation of the CD molecular mass. Furthermore, the biocompatibility of the new materials was evaluated through cytotoxicity and cell-penetrance assays revealing that the materials were non cytotoxic up to 0.1 mg/mL. Moreover, the biocompatible developed nanoplatform penetrates in the cells maintaining the material's intrinsic fluorescence, thus constituting an adequate photoluminescent-tag with high-contrast for in vitro cell imaging. SignificanceThis work provides a new and easy method to combine cyclodextrins and carbon dots into a biocompatible material which can be used as nanoplatform both as drug delivery system and as photoluminescent tag in cell imaging. Likewise, this paper shows how to characterize the number of cyclodextrins and active cyclodextrins per CD, having an average stoichiometric relation of 1:1 for guest molecule – CD. Additionally, the minimum molecular mass of the unmodified CD was indirectly obtained, yielding about 1.6–1.9 kDa.

Red-light-excited TiO2/Bi2S3 heterojunction nanotubes and photoelectric hydrogels mediate epidermal-neural network reconstruction in deep burns

Inspired by the strong light absorption of carbon nanotubes, we propose a fabrication approach involving one-dimensional TiO2/Bi2S3 QDs nanotubes (TBNTs) with visible red-light excitable photoelectric properties. By integrating the construction of heterojunctions, quantum confinement effects, and morphological modifications, the photocurrent reached 9.22 µA/cm2 which is 66 times greater than that of TiO2 nanotubes (TNTs). Then, a red light-responsive photoelectroactive hydrogel dressing (TBCHA) was developed by embedding TBNTs into a collagen/hyaluronic acid-based biomimetic extracellular matrix hydrogel with good biocompatibility, aiming to promote wound healing and skin function restoration. This approach is primarily grounded in the recognized significance of electrical stimulation in modulating nerve function and immune responses. Severe burns are often accompanied by extensive damage to epithelial-neural networks, leading to a loss of excitatory function and difficulty in spontaneous healing, while conventional dressings inadequately address the critical need for nerve reinnervation. Furthermore, we highlight the remarkable ability of the TBCHA photoelectric hydrogel to promote the reinnervation of nerve endings, facilitate the repair of skin substructures, and modulate immune responses in a deep burn model. This hydrogel not only underpins wound closure and collagen synthesis but also advances vascular reformation, immune modulation, and neural restoration. This photoelectric-based therapy offers a robust solution for the comprehensive repair of deep burns and functional tissue regeneration. Statement of significanceWe explore the fabrication of 1D TiO2/Bi2S3 nanotubes with visible red-light excitability and high photoelectric conversion properties. By integrating heterojunctions, quantum absorption effects, and morphological modifications, the photocurrent of TiO2/Bi2S3 nanotubes could reach 9.22 µA/cm², which is 66 times greater than that of TiO2 nanotubes under 625 nm illumination. The efficient red-light excitability solves the problem of poor biosafety and low tissue penetration caused by shortwave excitation. Furthermore, we highlight the remarkable ability of the TiO2/Bi2S3 nanotubes integrated photoelectric hydrogel in promoting the reinnervation of nerve endings and modulating immune responses. This work proposes an emerging therapeutic strategy of remote, passive electrical stimulation, offering a robust boost for repairing deep burn wounds.

Optimization of near-infrared luminescence performance in Cr3+-doped double perovskite Sr2ScTaO6 phosphor by Nb5+ ion substitution

Here, Nb5+ were partially substituted for Ta5+ in the double perovskite Sr2ScTaO6: Cr3+ phosphor to improve its luminescence performance and finally obtained the optimized phosphor Sr2ScTa0.6Nb0.4O6: Cr3+. The structure, substitution mechanism, luminescence optimization mechanism, crystal field, and thermal stability of the phosphor were all thoroughly explored. The results indicate that introducing Nb5+ into Sr2ScTaO6: Cr3+ can cause lattice distortion in the host, and the distorted crystal lattice can break the forbidden transition of Cr3+, thereby enhancing its absorption of excitation light. At the same time, the full width at half maximum of the phosphor emission increased from 176.4 nm to 179.7 nm. And the internal quantum efficiency, absorption efficiency, and external quantum efficiency of the optimized Sr2ScTa0.6Nb0.4O6: Cr3+ phosphor can reach 86.3%, 49% and 42.3%, respectively. The photoelectric conversion efficiency of the optimized pc-LED increased from 5.63% to 7.80%@100 mA, indicating the introduction of Nb5+ in Sr2ScTaO6: Cr3+ improved the luminescence performance of phosphor. The above results provide directions for the development of more efficient and promising double-perovskite NIR phosphors.

Asymmetric-absorption-induced spectral redshift in a monolithic III-nitride on-chip system

Integrating optoelectronic devices with various functions into a monolithic chip is a popular research frontier. The top-down integration scheme on silicon-based III-nitride wafers has unique advantages. A monolithic III-nitride on-chip system with lighting source, electrical absorption modulator, waveguide and photodetector with the same structure were designed and fabricated to discover the asymmetry of photon emission and absorption in quantum well diode. The characteristics of the chip were characterized in detail and three different spectral redshifts were observed in the experiment. Results revealed that the asymmetric absorption causes spectral redshift in a quantum well diode, and self-absorption is a fundamental and universal phenomenon in quantum wells. This work provides an important reference for future III-nitride optoelectronic integration.

Photochemistry of IrCl<sub>6</sub><sup>3–</sup> complex in aqueous solutions

The photochemistry of the [IrIIICl6]3- complex in aqueous solutions was studied by the methods of stationary and laser flash photolysis. As the result of a light quantum absorption, parallel processes of photoaquatation and photoionization occur. The aquated electron ea–q, which is formed with a quantum yield of 0.12 (excitation at 266 nm), is predominantly decayed in reactions with the initial complex and dissolved oxygen. The rate constant of ea–q capture by the [IrIIICl6]3- complex was measured. The main final photolysis products are Ir(III) complexes with different compositions of ligands, as well as several percents of Ir(IV) complexes. The formation of final products occurs in the time range from milliseconds to seconds.

Rapid synthesis of phosphor-glass composites in seconds based on particle self-stabilization

Phosphor-glass composites (PGC) are excellent candidates for highly efficient and stable photonic converters; however, their synthesis generally requires harsh procedures and long time, resulting in additional performance loss and energy consumption. Here we develop a rapid synthetic route to PGC within about 10 seconds, which enables uniform dispersion of Y3Al5O12:Ce3+ (YAG:Ce) phosphor particles through a particle self-stabilization model in molten tellurite glass. Thanks for good wettability between YAG:Ce micro-particles and tellurite glass melt, it creates an energy barrier of 6.94 × 105 zJ to prevent atomic-scale contact and sintering of particles in the melt. This in turn allows the generation of YAG:Ce-based PGC as attractive emitters with high quantum efficiency (98.4%) and absorption coefficient (86.8%) that can produce bright white light with luminous flux of 1227 lm and luminous efficiency of 276 lm W−1 under blue laser driving. This work shows a generalizable synthetic strategy for the development of functional glass composites.

Quantum radiation and absorption by current fluctuations of atoms in strong laser fields

Quantum radiation and absorption by current fluctuations of atoms in strong laser fields

Efficient and ultra-broadband near-infrared emission in perovskite-like Mg4Sb2O9:Cr3+ phosphor

Near-infrared (NIR) spectroscopy based on phosphor-converted NIR light-emitting-diode (LED) has extensive applications in modern life, stimulating the exploration of ultra-broadband NIR phosphors with high efficiency. Herein, Cr3+-doped perovskite-like Mg4Sb2O9 phosphor was synthesized, which exhibits a NIR emission with peak wavelength of 855 nm, and a full width at half maximum (FWHM) of about 207 nm. Upon 442 nm excitation, the quantum efficiency (QY) and absorption efficiency (AE) were determined to be 59.1 % and 48.3 %, respectively; while the luminescence intensity remained 61.5 % of room temperature at 373 K, indicating an excellent efficient and a moderate thermal stability of this material. The fabricated NIR pc-LED through combining the optimized phosphor with a 455 nm LED chip presents an output power of 20.1 mW and a photoelectronic conversion efficiency of 3.6 % under a driving current of 175 mA. These results suggest that Mg4Sb2O9:Cr3+ phosphor with excellent luminescent performance may have good potential for applications in NIR pc-LEDs.

Theoretical calculations of THz intersubband absorption in step quantum well structures based on MgZnO/ZnO materials at 77 K

Theoretical calculations of THz intersubband absorption in step quantum well structures based on MgZnO/ZnO materials at 77 K

Janus Device Based on Liquid Crystal Regulation with a Large Incidence Angle: Analogous Quantum Optical Effect and Absorption

AbstractIn this paper, a Janus metastructure device (JMD) is proposed. The JMD design introduces asymmetric structures, which leads to the generation of analogous quantum optical effects when light is incident at large angles. Specifically, forward electromagnetic‐induced transparency (EIT) and backward narrowband absorption (NA) are achieved when light is incident along different directions, displaying Janus characteristics in the forward and backward directions. Additionally, the operating frequency of JMD can be controlled through the use of liquid crystal. Such features hold promising potential for various applications in photonic and optoelectronic fields. When the axial direction of the liquid crystal is oriented along the x‐direction, the JMD achieves a transparent window over 90% within 0.46–0.51 THz at forward incidence, and an absorption peak of 84.1% appears at 0.331 THz at backward incidence. When the axial direction is oriented along the y‐direction, the JMD achieves EIT in the range of 0.51–0.575 THz at forward incidence, and a backward absorption peak of 93.3% occurs at 0.305 THz. In addition, the performance changes at different polarization and incidence angles are presented. The mechanism of absorption generation, the method of suppressing excess absorption, and the parametric inversion of the electromagnetic characteristics of JMD are also discussed.

On photokinetics under monochromatic light.

The properties of photokinetics under monochromatic light have not yet been fully described in the literature. In addition, for the last 120years or so, explicit, handy model equations that can map out the kinetic behaviour of photoreactions have been lacking. These gaps in the knowledge are addressed in the present paper. Several general features of such photokinetics were investigated, including the effects of initial reactant concentration, the presence of spectator molecules, and radiation intensity. A unique equation, standing for a pseudo-integrated rate law, capable of outlining the kinetic behaviour of any photoreaction is proposed. In addition, a method that solves for quantum yields and absorption coefficients of all species of a given photoreaction is detailed. A metric (the initial velocity) has been adopted, and its reliability for the quantification of several effects was proven by theoretical derivation, Runge-Kutta numerical integration calculations and through the model equation proposed. Overall, this study shows that, under monochromatic light, photoreaction kinetics is well described by -order kinetics, which is embodied by a unifying model equation. This paper is aimed at contributing to rationalising photokinetics via reliable, easy-to-use mathematical tools.

Quantum absorption properties of Kerr–Newman–de Sitter black hole

In this work, we utilize the Wentzel–Kramers–Brillouin (WKB) approximation to determine the Hawking temperature corresponding to the Kerr–Newman–de Sitter (KNdS) spacetime. Specifically, we calculate the low frequency absorption cross-section for the KNdS black hole in a charged scalar field and analyzed its dependence on the characteristics of the black hole. Through our research, we have established a correlation between the absorption cross-section ([Formula: see text]) and the Hawking temperature ([Formula: see text]) of the black hole, demonstrating an inverse proportionality between the two quantities. Furthermore, we also deduce the absorption cross-sections for Kerr–de Sitter, Reissner–Nordstrom–de Sitter, Schwarzschild–de Sitter and Schwarzschild black holes, and compare them with previously obtained results. The validity of our findings is demonstrated by these comparisons.

Disorder effect on intersubband optical absorption of n-type δ-doped quantum well in GaAs

The inevitable structural disorder associated with the fluctuation of the applied external electric field, laser intensity, and bidimensional density in the low dimensional quantum system can affect noticeably optical absorption properties and the related phenomena. In this work, we study the effect of structural disorder on the optical absorption properties in delta-doped quantum wells (DDQWs). Starting from effective mass approximation and the Thomas-Fermi approach as well as using the matrix density, the electronic structure and the optical absorption coefficients of DDQWs are determined. It is found that the optical absorption properties depend on the strength and the type of structural disorder. Particularly, the bidimensional density disorder suppresses strongly the optical properties. Whilst, the disordered external applied electric field fluctuates moderately in the properties. In contrast, the disordered laser holds absorption properties unalterable. So, our results specify that to have and preserve good optical absorption properties in DDQWs, requires precise control of the bidimensional. Besides, the finding may improve the understanding of the impact of the disorder on the optoelectronic properties based on DDQWs.

Bi3+ ions doped double perovskite Ca2MgWO6 phosphor for yellow light emission

To develop new single-phase phosphor materials, a series of Ca2MgWO6:yBi3+ samples were successfully manufactured by high temperature solid state method. The microstructures and optical performances of the phosphors were investigated via X-ray diffraction, electron microscopy, as well as photoluminescence. The crystal lattice and morphology of the samples were adjusted by adding MgF2 flux. And the emission intensity of Bi3+ ions was enhanced by 21.4%. In addition, the characteristics emission of the [WO6] group was explored. Under excitation at 297 nm, [WO6] group possesses a broad emission band (350–550 nm) from W6+→O2− charge transfer band. Under 336 nm excitation, Ca2MgWO6:yBi3+ phosphors exhibit an ultra-wide emission band (400–800 nm) of Bi3+ ions. At the same time, Ca2MgWO6:yBi3+ phosphors have high quantum efficiency and absorption efficiency, and their maximum values reach 42.1% and 89.1%, respectively. All results suggest that Ca2MgWO6:yBi3+ phosphors might have potential applications in solid state lighting.

The Electronic Structure and Optical Spectroscopy of ErNi2Mnx Compounds

The electronic structure and optical properties of nonstoichiometric ErNi2Mnx compounds (with х = 0, 0.5, 1) have been studied. Spin-polarization calculations of the total and partial densities of electron states have been performed in terms of DFT + U method with a correction for strong electronic correlations in the 4f shell of Er in the approximation of ErNi2 – xMnx solid-solution. The peculiarities of transformations of the densities of electron states Have been determined depending on the manganese content. The optical properties of these compounds have been studied over a wide wave length range. The calculated interband optical conductivity spectra have been compared with the dependences obtained experimentally. The origin of the quantum absorption of light is discussed. The plasma and relaxation frequencies of current carriers have been determined.

Hybrid Dielectric-Plasmonic Nanoantenna with Multiresonances for Subwavelength Photon Sources

The enhancement of the photoluminescence of quantum dots induced by an optical nanoantenna has been studied considerably, but there is still significant interest in optimizing and miniaturizing such structures, especially when accompanied by an experimental demonstration. Most of the realizations use plasmonic platforms, and some also use all-dielectric nanoantennas, but hybrid dielectric-plasmonic (subwavelength) nanostructures have been very little explored. In this paper, we propose and demonstrate single subwavelength hybrid dielectric-plasmonic optical nanoantennas coupled to localized quantum dot emitters that constitute efficient and bright unidirectional photon sources under optical pumping. To achieve this, we devised a silicon nanoring sitting on a gold mirror with a 10 nm gap in-between, where an assembly of colloidal quantum dots is embedded. Such a structure supports both (radiative) antenna mode and (nonradiative) gap mode resonances, which we exploit for the dual purpose of out-coupling the light emitted by the quantum dots into the far-field with out-of-plane directivity, and for enhancing the excitation of the dots by the optical pump. Moreover, almost independent control of the resonance spectral positions can be achieved by simple tuning of geometrical parameters such as the ring inner and outer diameters, allowing us to conveniently adjust these resonances with respect to the quantum dots emission and absorption wavelengths. Using the proposed architecture, we obtain experimentally average fluorescence enhancement factors up to $654\times$ folds mainly due to high radiative efficiencies, and associated with a directional emission of the photoluminescence into a cone of $\pm 17\degree$ in the direction normal to the sample plane. We believe the solution presented here to be viable and relevant for the next generation of light-emitting devices.

Quantum mechanics-based seismic energy absorption analysis for hydrocarbon detection

SUMMARYSeismic attenuation has a considerable impact on resolution reduction and the increase in the dominant frequency period of seismic data. The absorption coefficient estimates, which measure inelastic attenuation, provide a deep understanding of the medium property changes in different geological settings. Conventional absorption coefficient estimation technologies always use time–frequency methods for seismic energy absorption analysis. However, despite continuing efforts to improve the absorption coefficient estimation, the limitation of the time–frequency methods still causes insufficient accuracy of the attenuation estimates, imposing major challenges in oil and gas hydrate exploration. In this study, a quantum mechanics-based seismic absorption coefficient estimation method was proposed for hydrocarbon detection. The seismic data were first projected on a specific basis constructed using the resolution of the Schrödinger equation. Seismic energy absorption analysis was then conducted in the potential-wave function domain. Finally, the quantum absorption coefficient estimates are given by the procedure after using a logarithmic operation and the least-squares fitting method. We examined the merits of these methods using model and field data. The gas reservoir was accurately targeted, which demonstrates that the proposed method has great potential for hydrocarbon detection.