Luminescence Contrast Research Articles

Photo-induced coloration and reversible luminescence modulation based on phosphosilicate glass ceramics for optcal storage application

Photochromic luminescent glass-ceramics attract lots of attention as an optical storage medium owing to their large storage capacity, reversible luminescence modulation, simple operation, etc. Herein, a kind of phosphosilicate glass containing AgBr nanoparticles was designed and prepared, which can realize the color reversible transformation between light yellowish-green and brown by alternating 365 nm light illumination and thermal treatment at 300 °C. The mechanism of photochromism and bleaching of the glass is related to the generation and decomposition of Ag0 clusters. Relying on the re-absorption effect, the emission intensity of Eu3+ ions could be reversibly regulated, showing the maximum luminescence contrast of 74 %. A good fatigue resistance and reproducibility of transmittance and luminescence modulation could be observed in cycle measurements, demonstrating its potential in the optical memory field.

Unlocking The Inherent Luminescence of Eu2+/Eu3+ by Light‐Induced Oxidation for Invisible Optical Storage

AbstractColor‐tunable luminescent materials are increasingly recognized for their potential applications in high‐security anticounterfeiting and optical storage technologies. However, luminescent materials with high‐contrast photoswitching behavior that change their luminescence properties in response to external stimuli are extremely scarce. In this study, a time‐dependent color‐tunable luminescent material, Na2BaSiO4:Eu2+ (NBSO:Eu), is introduced. This material leverages the inherent luminescence of Eu2+/Eu3+ through a light stimulus. Under 365 nm irradiation, the blue luminescence of Eu2+ gradually degraded over time, reaching a luminescence contrast of up to 88%. This degradation is accompanied by a color change of the emitted light from blue to red (Eu3+). These color changes can be reversibly tuned by alternating light or thermal stimuli. Experimental investigations revealed that the photogenerated Eu3+ ions and defects, acting as killer centers, induced multicolor luminescent switching behavior. Owing to their unique optical properties, NBSO:Eu offers exciting opportunities for designing advanced dynamic anticounterfeiting and invisible optical storage.

Upconverted luminescence from lanthanide-doped ferroelectrics for optical storage and triple-mode temperature probing

Developing smart luminescent materials with desirable and tunable characteristics has always been an overriding priority of fluorescence technology. However, huge challenges encompass the single functionality of the luminescent materials and the traditional chemical synthetic techniques with rigorously controlling over the miscellaneous experimental conditions and variables. Herein, the lanthanide-doped bismuth-layered ferroelectric (Na0.5Bi0.5)0.96Er0.04Bi2Nb2O9.02 has been prepared to be utilized as a platform that not only serves the in-situ and reversible tailoring of the upconverted emission via physical methods, but also enable the versatile functionalities such as photomemory and multi-modal temperature sensing. High luminescent contrast that can reach up to 83.7 % before and after the 405 nm irradiation has been realized on the basis of the photochromic phenomenon of the as-prepared (Na0.5Bi0.5)0.96Er0.04Bi2Nb2O9.02 sample, and the fundamental application in the photomemory has been exhibited. Moreover, the performances of triple-mode thermometry built on the fluorescent intensity ratio techniques (2H11/2/4S3/2 and 4S3/2/4F9/2) as well as the lifetime of the 4S3/2 excited state of the Er3+ ion have been investigated in carefulness, with the maximal relative sensitivities of 1.22 % K−1 at 300 K, 0.92 % K−1 at 510 K, and 0.18 % K−1 at 450 K, respectively. Our results provide significant insights into the methodology of physically modulating the upconversion luminescence, and offer a glamorous pathway for multifunctional high-end applications.

Малогабаритный лазерно-волоконный флуориметр ик-спектрального диапазона для люминесцентной фотодиагностики опухолей

The results of the development of a small-sized laser fiber fluorimeter in the IR spectral range for a luminescent photodiagnostics of superficial localization tumors are presented. This device, working in conjunction with the “Fluroscan” type pharmaceutical composition based on the 2,4-di(α-methoxyethyl)deuteroporphyrin IX ytterbium complex dipotassium salt, ensures the achievement of high values of the luminescent diagnostic contrast index for a neoplasm/normal tissue. Import substitution of some basic design elements of the developed device, in particular the photodiode module, was carried out with a domestic analogue.

Development of red-luminescent hybrids as contrast agents for cell imaging: A correlation among surface, luminescence, and biological properties

TTA (2-thenoyltrifluoroacetone), DBM (dibenzoylmethane), and EPHEN (5,6-Epoxy-5,6-dihydro- [1,10] phenanthroline) have generated europium complexes with excellent red emission properties. However, for bio applications, these complexes have been grafted on the surface of silica nanoparticles (SNP), by different approaches, due to their low water solubility. Here, we report how three approaches influence the surface, luminescent, and biological properties of 50 and 170 nm-SNP functionalized with carboxylic acid or phenanthroline ligands, useful to anchor TTA and DBM-Eu-complexes. TTA-hybrids exhibited better photophysical properties over the DBM ones, although intermolecular interactions between TTA and silica surface groups are likely to influence their properties. Aiming at such biological application, approach 3 resulted in the luminescent PHEN-hybrids with the highest values of intrinsic (φEuEu) and absolute quantum yields (φEuL), color purity of 100%, and high sensibilization efficiency (η). However, depending on the approach used, different surface charges were observed for the hybrids that directly impacted their cytotoxicity in Huh 7.5 cells. The larger the size of the nanoparticle or the more positive its surface charge is, the lower the toxicity of the hybrid. Even considering the presence of the protein corona effect, estimated in DMEM medium, the initial surface charge, observed in the buffer solution, plays an important role in the nanoparticle-cell interaction. Confocal microscopy images revealed that the hybrids were internalized by cells regardless of their size and surface charge, and their luminescence was also detectable, making them promising candidates for cell imaging applications as luminescent contrast agents.

Multicolor upconversion reversible modulations in YNbO4:Er3+/Tm3+/Yb3+ photochromic materials

Photochromic materials with multicolor upconversion reversible modulations are attractive in optical switching devices. Herein, the fabricated YNbO4:Er3+/Tm3+/Yb3+ materials exhibit excellent photochromism and multicolor upconversion properties from green, red to near infrared (NIR) emissions with increasing Yb concentrations. Reversible multiband upconversion modulations are achieved by alternating light (365 and 405 nm) or thermal stimuli. After 365 nm irradiation, the luminescence color changes from yellow to red, the luminescent photoswitching contrast reaches up to 86.21% (green), 82.12% (red) and 77.38% (NIR) in the Y0.83Er0.01Tm0.01NbO4:0.15 Yb sample. Besides, the upconversion emission intensity before and after photochromic reaction shows remarkable change in a wide temperature range of 298–718 K. These results indicate that the Er3+/Tm3+/Yb3+ tri-doped YNbO4 materials can be a good candidate in optical switching and data storage applications.

Photochromic and Electric Field-Regulating Luminescence in High-Transparent (K,Na)NbO3-Based Ferroelectric Ceramics with Two-Phase Coexistence.

Rare earth Tb3+ doped (K0.465Na0.465Li0.07)(Nb0.93Bi0.07)O3 (KNNLB-x%Tb) lead-free transparent ferroelectric ceramics were designed and prepared. The effects of Tb3+ on phase structure, microstructure, optical transmittance, photoluminescence, and photochromic behaviors were studied. Although two ferroelectric phases coexist, the optical transmittance can reach the high value of 74% in the visible light region because of the fine grains, dense ceramic microstructure, large optical energy band gap, and relatively high symmetry of coexisting ferroelectric phases. In addition, Tb3+ works as a luminescent center, and the reversible photochromic modulation is achieved by alternate stimulation of illumination and heat treatment. Meanwhile, the luminescence contrast can be improved under in situ electric field stimulation due to the easy change of lattice symmetry in coexisting ferroelectric phases. The generation of color centers after illumination and the local crystal field around the luminescent center caused by in situ electric field contributes to above phenomena. These ceramics exhibit the great potential in optical data storage and anticounterfeiting.

Entirely Reversible Photochromic Glass with High Coloration and Luminescence Contrast for 3D Optical Storage

Entirely Reversible Photochromic Glass with High Coloration and Luminescence Contrast for 3D Optical Storage

Assembly of Aggregation-Induced Emission Active Bola-Amphiphilic Macromolecules into Luminescent Nanoparticles Optimized for Two-Photon Microscopy In Vivo.

The (Z) and (E)-isomers of an extended tetraphenylethylene-based chromophore with optimized two-photon-induced luminescence properties are separated and functionalized with water-solubilizing pendant polymer groups, promoting their self-assembly in physiological media in the form of small, colloidal stable organic nanoparticles. The two resulting fluorescent suspensions are then evaluated as potential two-photon luminescent contrast agents for intravital epifluorescence and two-photon fluorescence microscopy. Comparisons with previously reported works involving similar fluorophores devoid of polymer side chains illustrate the benefits of later functionalization regarding the control of the self-assembly of the nano-objects and ultimately their biocompatibility toward the imaged organism.

Large reversible upconversion luminescence modification and 3D optical information storage in femtosecond laser irradiation-subjected photochromic glass

Fast response, high luminescence contrast, three-dimensional (3D) storage, and nondestructive reading are key factors for the optical storage application of photochromic materials. Femtosecond (fs) laser direct writing technology with multiphoton nonlinear absorption is becoming a useful tool for microprocessing functional units in the 3D space of glass owing to its remarkable advantages, such as a fast processing speed and high processing accuracy. Herein, the photochromism of transparent glass codoped with rare-earth ions was investigated under 800-nm fs laser irradiation, affording a fast response. The photochromic glass achieves an upconversion luminescence (UCL) modification of 92%. The photochromic glass can be bleached back to its original color using heat treatment. The transmittance and UCL modification show excellent reproducibility under alternating stimulations between 800-nm fs laser irradiation and heat treatment. The data can be written in the interior of the transparent photochromic glass using 800-nm fs laser irradiation, facilitating 3D information storage. These results suggest that the 800-nm fs laser irradiation-subjected photochromic glass is an ideal optical data storage medium.

Synthesis and Photoluminescence Properties of MoS2/Graphene Heterostructure by Liquid-Phase Exfoliation.

Here, we report the synthesis of MoS2/graphene heterostructure in single-stage, liquid-phase exfoliation using a 7:3 isopropyl alcohol/water mixture. Further, the synthesized heterostructure was characterized using UV–visible and micro-Raman spectroscopies, transmission electron microscopy (TEM), and dynamic light scattering (DLS) analysis. UV–visible and micro-Raman analyses confirmed that the synthesized heterostructure had mostly few-layered (two-to-four sheets) MoS2. The photophysical properties of the heterostructure were analyzed using steady-state and time-resolved luminescence techniques. Enhanced photoluminescence was observed in the case of the heterostructure probably due to an increase in the defect sites or reduction in the rate of nonradiative decay upon formation of the sandwiched heterostructure. Applications of this heterostructure for fluorescence live-cell imaging were carried out, and the heterostructure demonstrated a better luminescence contrast compared to its individual counterpart MoS2 in phosphate-buffered saline (PBS).

Up-conversion luminescence regulation and its boosting by polarization in Er3+/Yb3+ doped SrBi8Ti7O27 photochromic ceramics for optical switching application

The various applications of luminescence materials were generally based on the effective modulation of luminescence spectra. However, the research on reversible spectral regulation of up-conversion (UC) luminescence materials was still in its infancy stage. In this work, a class of smart phosphor, Er3+ and Yb3+-codoped SrBi8Ti7O27 (SBYT: xEr3+) intergrowth bismuth layer-structured ferroelectric, possessing fast sensitivity to visible light irradiation, was reported based on visible light driven photochromic effect. Through the alternate stimuli of light irradiation and heating treatment, the reversible regulation of UC luminescence was achieved accompanying with the switching of coloration and decoloration processes. The luminescence modulation degree tightly relied on the irradiation time and thermal treatment modes. The reversibility and stability properties were also revealed. Moreover, it is found that polarization treatment was an effective approach which can be adopted to improve the UC luminescence contrast. The maximum luminescence modulation ability of SBYT: xEr3+ reached up to 81.3% which was 131% of that un-polarized sample. It is believed that SBYT: xEr3+ ceramics can act as a promising candidate for optical data storage and anti-counterfeiting applications.

Spontaneous Radiation Amplification in a Microsphere‐Coupled CsPbBr3 Perovskite Vertical Structure

AbstractMicrosphere (MS) cavities hold great potential in nanophotonics due to their extraordinary optical properties. All‐inorganic trihalide perovskites with high environmental stability and easy‐for‐preparation have shown great promise for the next‐generation optoelectronic nanodevices. Unfortunately, the nonradiative recombination of exciton is inevitably aggravating the photoluminescence quantum yields (PLQYs). Here, a microsphere‐coupled CsPbBr3 perovskite vertical structure is proposed for amplification of spontaneous radiation (SR) up to 190‐fold. The mechanisms of SR amplification by an MS cavity are completely revealed, for the first time, including Mie focusing (MF) for energy harvesting, directional antenna (DA) for emission convergence, and whispering‐gallery modes (WGMs) for regulation of exciton dynamics. The temperature‐dependent photoluminescence (PL) spectra clarify the contributions of WGMs for the boosting of SR decay and suppression of exciton–phonon interactions for giant PL enhancement. Furthermore, a straightforward approach is presented for a selective MS array capped on a perovskite microcrystal (PeMC) film as a vertical structure for patterned PL enhancement. The excitation‐power‐ and excitation‐observation‐angle‐dependent luminescence contrast inspire a novel anticounterfeiting strategy. The vertical architecture not only advances the understanding of microcavity‐based SR amplification from PeMCs, but also offers opportunities to facilitate the synergistic manipulation of optical fields and exciton–phonon interactions for developing high‐efficient optoelectronic devices.

Strategies to promote permeation and vectorization, and reduce cytotoxicity of metal complex luminophores for bioimaging and intracellular sensing.

Transition metal luminophores are emerging as important tools for intracellular imaging and sensing. Their putative suitability for such applications has long been recognised but poor membrane permeability and cytotoxicity were significant barriers that impeded early progress. In recent years, numerous effective routes to overcoming these issues have been reported, inspired in part, by advances and insights from the pharmaceutical and drug delivery domains. In particular, the conjugation of biomolecules but also other less natural synthetic species, from a repertoire of functional motifs have granted membrane permeability and cellular targeting. Such motifs can also reduce cytotoxicity of transition metal complexes and offer a valuable avenue to circumvent such problems leading to promising metal complex candidates for application in bioimaging, sensing and diagnostics. The advances in metal complex probes permeability/targeting are timely, as, in parallel, over the past two decades significant technological advances in luminescence imaging have occurred. In particular, super-resolution imaging is enormously powerful but makes substantial demands of its imaging contrast agents and metal complex luminophores frequently possess the photophysical characteristics to meet these demands. Here, we review some of the key vectors that have been conjugated to transition metal complex luminophores to promote their use in intra-cellular imaging applications. We evaluate some of the most effective strategies in terms of membrane permeability, intracellular targeting and what impact these approaches have on toxicity and phototoxicity which are important considerations in a luminescent contrast or sensing agent.

Broad bandwidth emission and in situ electric field modulation of photoluminescence in Nd-doped ferroelectric crystals.

The electric field modulation of photoluminescence in ferroelectric-optical materials as a novel in situ, non-damaging and real-time controllable method has drawn much research focus. The broad bandwidth emission of 33 nm and a tuneable luminescence contrast of 28% were achieved in Nd-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Nd:PMNT) tetragonal ferroelectric-optical crystals arising from spontaneous polarization. The study of Nd:PMNT ferroelectric crystals under a cyclic, triangular alternating current voltage wave showed that the change in the photoluminescence intensity subjected to an electric field is mainly related to the 180° domain distribution, rather than the 90° domain. The physical process of electric field tuning luminescence is to control the 180° domain distribution using the external electric field, which thereby effectively tunes the luminescence. This finding restricts the limitation of a specific phase change region, which greatly increases the range of materials used and has guiding significance for research in the electric field modulation of luminescent technology.

Rare earth element doped hydroxyapatite luminescent bioceramics contrast agent for enhanced biomedical imaging and therapeutic applications

The design and synthesis of alternative biocompatible, luminescent bioimaging agent for application in diagnostics imaging and preventive medicine is very important for the future of biomedicine. With an advanced flexible structure of hydroxyapatite (HAp), rare earth ions (Gd3+, Eu3+) were doped to achieve an enhanced luminescent optical property. A facile wet co-precipitation method was employed to dope Gd3+, and Eu3+ on host HAp structure (Eux-Gdx-HAp). Different sophisticated characterization instruments, such as powder X-Ray diffraction, Fourier transformed infrared (FTIR) spectroscopy, micro Raman spectroscopy, Thermogravimetric-differential thermal analysis (TG-DTA), Brunauer-Emmett-Teller (BET) surface area analysis confirms the hexagonal crystal structure, functional groups, high thermal stability, with large surface area and average pore size. The optical properties were measured by diffusive reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and fluorescence imaging. The enhanced luminescence could be observed due to “Gd–Eu” co-doping, which causes energy transfer (6IJof Gd3+→5HJof Eu3+) under 273 nm excitation with possible combination effect of the cooperative up-conversion and subsequent energy transfer under 394 nm excitation respectively. The in vitro study confirms the intracellular nontoxic behavior of Eux-Gdx-HAp nanocrystals with good biocompatibility. Further in vivo studies with Eux-Gdx-HAp nanocrystals confirms the cell labelling and in vivo imaging capabilities. The synthesized biocompatible, nontoxic Eux-Gdx-HAp nanomaterials has the potential to act as a luminescence enhanced contrast agent for biomedical fluorescent imaging applications.

Quantifying thermal barrier coating delamination through luminescence modeling

Thermal barrier coatings (TBCs) are widely used in the hot sections of gas turbine systems as they are remarkably efficient in insulating the underlying superalloys, leading to higher operating temperatures and therefore enhancing the performance of the engines. However, this benefit is only possible if the integrity of the TBC under aggressive thermo-mechanical environments is ensured. Delamination is a common but hard to detect failure mode. We present, in this work, supported by experimentation, the implementation of a modeling approach applying the Kubelka-Munk theory to provide numerical quantification of luminescence contrast and intensity due to top coat delamination in TBCs. The method relies on the drastic change in reflectivity when a delamination forms, exploiting it for high-contrast luminescence mapping. Two distinct TBC configurations containing an erbium-doped yttria-stabilized zirconia (YSZ:Er3+) layer for delamination sensing were used to validate this model. A delamination zone induced by Rockwell indentation was successfully tracked by measuring an increase of the intensity of the erbium emission line at 562 nm. Luminescence-based methods for delamination detection can provide a revolutionary non-invasive technique, with potential for both off-line and on-line engine monitoring.

Porous Upconversion Nanostructures as Bimodal Biomedical Imaging Contrast Agents

Lanthanide ion doped upconversion nanoparticles (UCNPs) hold great promise as multimodal contrast agents for a range of medical imaging techniques, including optical bioimaging (OBI), magnetic resonance imaging (MRI), and computed tomography (CT). However, it is challenging to obtain UCNPs with both maximal contrast enhancement effects for both OBI and MRI simultaneously owing to the dilemma in the size of UCNPs. UCNPs in large dimensions contain more photonic Ln ions and less surface defects, which is favored for high luminescent emissions, while small UCNPs with high specific surface areas allow a higher proportion of paramagnetic Ln ions to be more accessible to water molecules, which offers enhanced contrast in MRI. In this work, we report the novel design of core−porous shell UCNPs with both high luminescent emissions and magnetic relaxivities as potential dual-modal contrast agents. The core–porous shell UCNPs were fabricated via the selective etching of the inert shell of NaYF4: 30%Gd at the active core of NaYF4: 20%Yb, 1%Er. Their morphology and composition were carefully characterized using transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, X-ray diffraction, and high resolution TEM. Their photoluminescent and magnetic resonance properties were experimentally determined and compared for the core, core–dense shell, and core–porous shell UCNPs. Core–porous shell UCNPs were found to display bright luminescence and superior MRI contrast enhancement, thus showing great potential as bimodal OBI and MRI contrast agents.

Apically homoleptic octahedral rhenium cluster complexes with 3-methylpyrazole

Octahedral rhenium cluster complexes with organic apical ligands have a high potential to be used in different fields due to their intrinsic luminescence and X-ray contrast properties. A series of new compounds based on cations [{Re6Q8}(3-Me-pzH)6]2+, where Q is S or Se and 3-Me-pzH is 3-methylpyrazole, were obtained and characterized in the solid state (FTIR, elemental and single crystal diffraction analysis) and in solution (1H NMR and ESI-MS). The compounds possess luminescence properties that mainly depend on inner Q ligands indicating the {Re6Q8}2+ core-centered nature of emission.

Optical temperature sensing and luminescent switching properties in Pr/Er‐doped (K0.5Na0.5)NbO3 materials

AbstractFor optical temperature sensing materials, the emission and excitation bands are extremely critical to measure the temperature by fluorescence intensity ratio (FIR) technique. Singly Ln‐doped optical temperature sensing materials exhibit very few emission bands, which greatly constraints their practical applications of FIR technique. Here, the fabricated Pr/Er co‐doped (K0.5Na0.5)NbO3 materials exhibited multi‐color (red‐green) and dual‐mode (downshifting/upconversion) luminescence properties. The temperature sensitivity can be effectively tuned by choosing different emission or excitation bands. The optimized optical temperature sensitivity reached up to 0.0094 K−1, much higher than that of most temperature sensing materials. Besides, the samples also showed excellent luminescence modulation properties based on the photochromic reaction. Under sunlight irradiation, the luminescent switching contrast (ΔRt) of the samples reached more than 60%. These results may provide a guiding role in designing and modulating optical temperature sensing properties for multifunctional materials.